In the eye (as well as all other body tissues except the lungs), arteries deliver blood to a tissue and veins remove blood from a tissue. The arteries carry oxygen and nutrition to the tissue, while veins remove waste products. A tiny retinal vein can become blocked by a blood clot; this blockage creates a backup in the system, resulting in leakage of blood and plasma (fluid from the bloodstream) into the retinal tissue. The retinal bleeding (hemorrhage) and swelling (edema) can cause significant visual loss. In addition, disruption of the blood supply can cause permanent damage to the retinal tissue from lack of oxygen and nutrition. In some cases, this may result in the development of abnormal blood vessels as a response to the lack of oxygen. 

Demographics

This condition typically occurs in individuals greater than 50 years old. Risk factors include hypertension, cardiovascular disease, diabetes, and glaucoma. Sometimes, individuals with retinal vein occlusion are found to have blood clotting disorders or inflammatory conditions. The second eye is affected in approximately 10% of cases.

Clinical Appearance & Symptoms

Retinal vein occlusions are classified as central retinal vein occlusion (CRVO) if the blockage occurs in the main vein leaving the eye through the optic nerve (Figure 1, 2). They are classified as branch retinal vein occlusion (BRVO) if the blockage occurs at one of the branches before reaching the main vein at the nerve; these often occur where arteries and veins cross (Figure 3, 4).

Figure 1	Figure 2	Figure 3	Figure 4

When patients have a retinal vein occlusion, they frequently complain of blurred vision, distortion, and/or a central blind spot.

Occluded veins typically appear tortuous, just as a hose tends to twist when water flow is blocked. There is bleeding seen in the distribution of the blocked vein in BRVO; the whole retina is involved in CRVO. There is also usually swelling of the retina in the same distribution; macular edema is a common finding and is often a source of significant visual loss.

When there is a severe blockage in which blood flow is cut off or significantly reduced, sensitive retinal tissue can become permanently damaged. This process is called ischemia. As a response to ischemia, the eye may develop abnormal new blood vessels called neovascularization. Unfortunately, these new vessels are fragile and tend to bleed, potentially resulting in vitreous hemorrhage. They may also scar and pull on the retina, potentially resulting in traction retinal detachment. Finally, if these blood vessels grow in the drainage structure of the eye, a very serious form of glaucoma can develop called neovascular glaucoma.

Diagnosis

When a retinal vein occlusion is suspected, certain diagnostic tests may be requested by your retinal specialist. The purpose of these tests is to confirm the diagnosis, evaluate the severity of the blockage, and possibly guide treatment.  Fluorescein angiography (Figure 2, 4)may be employed in the diagnosis of retinal vein occlusion. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the ocular circulation. The site of blockage can often be clearly identified. Leakage of dye is also often seen from macular edema and areas of neovascularization. Areas of ischemia can be identified and measured.

Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the retina and any associated macular edema (Figure 5). This technique is very valuable in quantifying the degree of fluid and monitoring response to potential treatment (Figure 6).

Treatment

Treatment of retinal vein occlusion is aimed at macular edema and complications of neovascularization.

Macular Edema:
Macular edema can be treated in two ways. In BRVO, laser treatment has proved beneficial in reducing the retinal swelling and improving vision compared to no treatment; unfortunately, no such benefit was found for CRVO with laser in most cases. A newer technique for treating macular edema from both BRVO and CRVO involves an injection of medication directly into the vitreous cavity (see sections on Intravitreal Injection and New Medications). Although experimental, this new therapy has shown great promise in alleviating macular edema and restoring vision in many cases. Current medications being injected include a corticosteroid (Kenalog) and an anti-neovascular agent (Avastin).

Retinal Neovascularization:
Complications of neovascularization include bleeding from abnormal blood vessels and a severe form of glaucoma, called neovascular glaucoma. At the earliest signs of any of these complications, your retinal specialist will recommend a different laser treatment called panretinal photocoagulation to target the abnormal vessels and help prevent these complications. These complications have the potential of causing blindness, and can even result in the loss of an eye in the worst cases.

The retina is essentially a thin sheet of light-sensitive nerve tissue that lines the back wall of the eye, much like wallpaper lines a wall of a room. If the retina tears, fluid can seep behind the retina through the opening caused by the tear. The gradual accumulation of fluid results in further separation of the retina from the eye wall, much like wallpaper peeling off of a house wall. This is termed a retinal detachment. Contrary to popular belief, retinal detachments don't only occur in boxers and those who have experienced trauma; in fact, most retinal detachments occur through no fault of the patient.

Demographics

Retinal detachment can affect any age group, male or female. Across the population, they occur in approximately 1 out of every 7000 people. There is a higher incidence with increasing nearsightedness; these eyes are longer and the retina tends to be stretched and thinned with a higher tendency to tear. Individuals with a condition called lattice degeneration are about 10 times as likely to develop a retinal detachment. Lattice degeneration is a condition in which the peripheral retina is thinned and has abnormal adhesion of the vitreous gel this predisposes the retina to tearing. Certain inflammatory conditions and infections are associated with a higher incidence of retinal detachment. Retinal detachments are particularly common with certain viral infections of the retina. Trauma is a definite cause in a certain percentage of retinal detachments. In certain cases, no definite cause can be identified.

Clinical Appearance & Symptoms

The key retinal defect in the above type of retinal detachment is a retinal tear. The thin retinal tissue is prone to tear when it is pulled upon by vitreous gel, the substance that fills the vitreous cavity. As we age, this gel normally liquefies and separates from the retina in a process called vitreous detachment. As the gel separates, two symptoms are often experienced. First, collagen particles suspended in the vitreous cavity can produce a sensation of floaters; patients often describe "cobwebs" or "bugs" in their vision. Second, any pulling on the retina stimulates the light sensors in this nerve tissue; this often results in flashes that are described as white lightning streaks.

When the vitreous gel pulls on the retina, the most common result is a gradual release of the gel and resolution of symptoms. The flashes often disappear completely, while floaters tend to linger. In some cases, the traction of the gel on the retina occurs near a blood vessel; this can result in sheering of the blood vessels and bleeding into the vitreous cavity. The patient experiences a different type of floaters caused by blood cells floating in the liquefied vitreous gel; sometimes this is severe enough to cause temporary blindness.

Finally, as a precursor to retinal detachment, vitreous traction on the retina can result in tearing of the retinal tissue. Floaters can be caused by pigment cells released from the space under the retina. At the first signs of floaters or flashes, individuals are advised to consult with their retinal specialist immediately. It is hoped that the tear(s) can be identified and sealed before fluid (liquefied gel) starts to seep under the retina and cause retinal detachment.

Left alone, fluid will generally continue to accumulate under the retina and peel the retina off of the eye wall (Figure 3-6). At the early stages, patients often notice a shadow in their peripheral (side) vision. As time progresses, the shadow gets closer and closer to the central vision. Eventually, the center of vision (the macula) usually will detach if left untreated. It is very important to try to repair a retinal detachment before the central vision is involved, as macular involvement often results in permanent visual loss or symptoms. Once the macula detaches, it is still important to reattach it to attempt to restore as much vision as possible.

The reason that retinal detachment is so critical is that it is a potentially blinding disease. The retina depends on two blood supplies to function properly and allow one to see. The first blood supply is within the retina. The second is on the back wall of the eye. When a retina detaches, it is separated from this second blood supply and the retinal nerve tissue is starved of oxygen and nutrition. The longer the retina is detached, the more nerve cells ultimately die. After a retinal detachment is repaired and the blood supply is restored, cells often recover; however, cells that have died cannot be replaced and this is what is responsible for potential permanent visual loss.

Diagnosis

When a retinal detachment is suspected, your retinal specialist will perform a detailed examination of the retina. The purpose is to identify the extent of the retinal detachment, find any retinal tear(s), and plan surgical repair. He or she will also be looking for any complicating conditions such as lattice degeneration. The examination process almost always involves pressing gently on the surface of the eye while looking in with a lens, a technique called scleral depression. This allows for a complete and accurate evaluation of the entire retina.

Treatment

Treatment of retinal detachment (regardless of technique) depends upon three factors: finding the retinal tear(s), sealing the retinal tear(s), and supporting the retinal tear(s).

A surgical approach will be formulated based on many variables including: number and location of tears, size of retinal detachment, degree of nearsightedness, presence of lattice degeneration, presence of vitreous hemorrhage, presence of a natural lens or cataract surgery, and age/health of the patient, among others.

There are basically 3 procedures that can be performed:

• Pneumatic Retinopexy
• Scleral Buckle
• Vitrectomy

Pneumatic Retinopexy:
A pneumatic retinopexy is the simplest technique, and can be performed in the office. The retinal specialist localizes the retinal tear(s) as with any retinal detachment. The tear(s) are then often sealed with a freezing treatment, called cryotherapy. A small gas bubble is then injected into the vitreous cavity with a small needle through the white of the eye. The patient is asked to position such that this bubble floats against the retinal tears and allows the freezing treatment to seal as the fluid under the retina dissipates. Alternatively, a laser treatment can be applied to seal the tear(s) after the fluid has dissipated. The patient is positioned for several days to allow the retina to heal properly. The gas bubble disappears on its own, usually within 2 weeks.

This procedure is most successful in patients with one tear located in the top half of the retina. It is also more successful in those that have natural lenses, as opposed to those that have undergone cataract surgery. Positioning is critical in this surgical technique. Therefore, those who cannot position should be excluded; reasons include back problems, neck problems, advanced age, young children, and mental disorder. Properly selected cases can expect a single procedure success rate around 85%. The healing is very rapid with this technique.

Scleral Buckle:
A scleral buckle must be performed in the operating room. As above, it involves locating the retinal tear(s). The tears are then often frozen with cryotherapy to seal them. Alternatively, a laser can be used to "spot weld" the retina after it is reattached; this often involves draining the accumulated fluid from under the retina. A thin plastic material is then sewn to the wall of the eye to indent the eye in the area of the tear(s). Often, this material is wrapped around the eye like a belt to support the retina for 360 degrees. The extra support provided by this device results in improved outcomes, with single surgery success rates close to 90%.

In order to properly place a scleral buckle, significant manipulation of the surface tissues of the eye must be performed. The eye is often bruised, red, and swollen following surgery and it can take up to 6 weeks to heal completely. Fortunately, the scleral buckle can almost never be seen following surgery and the eye looks completely normal once it heals. The scleral buckle is generally left on the eye permanently. In certain cases, the buckle must be removed if there is associated infection or if it works its way through the surface tissues (a process called extrusion). Individuals undergoing scleral buckling may also experience increased nearsightedness following surgery, and there may be a discrepancy in the size of objects between the two eyes. In some cases, there may be a droop in the eyelid or lack of full movement of the eye caused by the scleral buckle. Bleeding is generally the worst complication of scleral buckling; fortunately, this is not common.

Vitrectomy:
Vitrectomy surgery must be performed in the operating room (see treatments/Vitrectomy). It involves complete removal of the vitreous gel through tiny openings made in the eye wall. The fluid is then drained from under the retina, and the retinal tear or tears are treated with laser. The entire vitreous cavity is filled with a gas bubble to press on the tears and allow the laser to seal while the retina is healing. The gas bubble usually lasts between 1 and 8 weeks, depending on the gas used and its concentration. This is in contrast to pneumatic retinopexy (above) where a smaller gas bubble is injected due to the presence of vitreous gel within the eye that is not removed.

Vitrectomy surgery is highly successful, with single surgery success rates approaching 95%. It is particulary valuable in patients who have previously had cataract surgery. Rare complications include bleeding and infection. In patients who have not had cataract surgery, cataract progression is more rapid following vitrectomy surgery. Vitrectomy is often combined with scleral buckling (above) in certain patients in an attempt to improve success rates in particularly high risk cases.

Redetachment
The most common complication of retinal detachment surgery (regardless of technique) is redetachment of the retina. This generally occurs through two mechanisms. First, new tears in the retina can develop after surgery. Fluid can enter these new tears and start the retinal detachment process all over again. Further surgery is necessary in these cases.

Second, scar tissue can grow on the surface of the retina following repair of retinal detachment. This can be thought of as an aggressive healing response. Unfortunately, the scar tissue often pulls on the retina, opens up old or new tears, and results in redetachment. This type of retinal detachment is particularly complicated and requires advanced surgical techniques to attempt to repair; in addition, the visual results are sometimes disappointing. Surgery is generally approached using vitrectomy techniques to access the inside of the eye, particularly the retinal surface. Fine instruments are used to peel the scar tissue off of the retina, allowing it to lay flat against the wall of the eye. Often times, an oil bubble is injected into the eye to achieve long-term support (as opposed to a gas bubble that dissipates in 1 to 8 weeks, as described above). Once the retina is stabilized, a second surgery is required if the oil bubble is to be removed.

With modern techniques, over 98% of retinal detachments can be successfully reattached. Those with extensive scar tissue and/or those left untreated for an extended period of time tend to have the worst outcomes. Patients are strongly advised to see their eyecare professional at the first signs of flashes, floaters, or shadows in their vision. Early intervention can often times lead to better outcomes, although any retinal detachment can ultimately lead to blindness.

Signs and symptoms
transient loss of vision prior to the artery occlusion in some cases

Branch Artery Occlusion
sudden & painless partial loss of vision in one eye

Central Artery Occlusion
sudden & painless total loss of vision in one eye

Diagnosis
diagnosis is usually made during a complete retinal exam and is made with an ophthalmoscope and a fluorescein angiogram

Treatments

Unfortunately, there are no treatment options that can restore vision which may be lost from an artery occlusion. Infrequently laser treatment may be necessary for delayed complications such as new blood vessel formation (neovascularization). Risk factors for an artery occlusion are diabetes, valvular heart disease, glaucoma, hypertension and high cholesterol levels.

Autosomal Dominant Inheritance has to do with genes and chromosomes. Genes are the basic unit of inheritance. They provide the instructions for growth and development from the single cell of a fertilized egg into the complex structure of a baby. Many continue to provide instructions for the production of proteins needed for bodily functions throughout a person's lifetime. Genes are strung together like beads on a string and packaged into individual chromosomes. Chromosomes come in pairs, with one coming from an individual's mother and the other from the father. One pair of chromosomes is called the sex chromosomes, since they determine the sex of the individual. The other 22 pairs of chromosomes are called autosomes.

Since our chromosomes come in pairs, we have two copies of all of our genes. The two copies in a pair of genes may or may not have the same code. A gene that is expressed regardless of the code in the other gene is said to be dominant. An autosomal dominant gene is one carried on one of the 22 pairs of autosomes. This means that males and females with the gene are equally likely to pass it on to male or female offspring.

A person who has a pattern macular dystrophy has one gene for the pattern dystrophy and one normal gene in one pair of genes. For example, if the father has one gene for the pattern dystrophy and one normal gene and the mother has two normal genes, the mother will always contribute a normal gene from that pair when they have children. There is a 50% chance the father will contribute the pattern dystrophy gene and a 50% chance he will contribute the normal gene.

There can be variation in the expression of a dominant gene even within the same family. In other words, the gene may cause a profound loss of vision for an individual and only a mild to moderate loss for that individual's child. Another phenomenon that is seen with some dominant genes is non-penetrance. This means that there is no detectable evidence that an individual with a dominant gene has the gene. When the gene is non-penetrant, it appears that the gene has skipped a generation. An example of this would be in a family with many people who have pattern dystrophy, including a child and a grandparent, but the intervening parent who has the same dominant gene for pattern dystrophy, has normal vision. Over the past few years, significant progress has been made in the molecular genetics of inherited macular dystrophies. Genes responsible for dominant and recessive Stargardt's macular dystrophy, as well as, Best's disease, have been localized to specific chromosomal regions. The peripherin/RDS gene, when defective, is associated with butterfly-shaped pattern dystrophy.

Based on the pattern of pigment distribution in the macula, this disease has been subdivided into five principle groups:

Group 1: adult-onset foveomacular vitelliform dystrophy.
Group 2: butterfly-shaped pigment dystrophy.
Group 3: reticular dystrophy of the RPE.
Group 4: multifocal pattern dystrophy simulating fundus flavimaculatus.
Group 5: fundus pulverulentus.

Patients with pattern dystrophies may show different patterns between the two eyes. They may even show progression from one pattern to another over several years. Patients can have a pattern dystrophy in just one eye since it may not yet have presented in the fellow eye. The presence of different pattern dystrophies within the same family suggests a common etiologic continuum. Pattern dystrophies of the retinal pigment epithelium, an arrangement of a pattern of dots, lines, or branches, are infrequent fundus abnormalities.

Patients with adult-onset foveomacular vitelliform dystrophy generally present with a solitary yellow subretinal lesion that's symmetric, round and slightly elevated. It is usually about 1/3 to 1 disc diameter in size (the size of the optic nerve that is visible in the retina). There is often a pigmented spot in the center. Initially, the yellow lesion may develop only in one eye. Most of the vitelliform lesions in this condition are small, but the larger ones can look identical to the "sunny-side-up" stage (looks like an egg sunny-side-up) of Best's vitelliform macular dystrophy. These can also look quite similar to bilateral serous detachments of the RPE. In differentiating Best's disease from these adult vitelliform lesions, it is important to remember that the vitelliform lesions in Best's develop in infancy or early childhood. Also, genetic linkage studies have identified Best's disease to a different chromosome. Attempts to identify common genetic linkage between Best's disease and other vitelliform macular dystrophies have been unsuccessful. The prognosis for maintaining good vision is favorable with this type. The elevated foveal lesions generally fade and leave an irregular oval or round area of RPE depigmentation. The lesions generally do not show the sort of disruption and layering of the yellow pigment that is seen with Best's vitelliform lesions. Choroidal neovascularization may occur, but it is rare.

Patients with a butterfly-shaped pattern dystrophy will have gray or yellow pigment in a well-organized pattern.

With reticular dystrophy, the pattern extends into the periphery and the yellow pigment is highly organized, in a manner resembling the knotted configuration of a fishnet or chicken wire.

Those with multifocal pattern dystrophy simulating fundus flavimaculatus develop a pattern of flecks similar to those of Stargardt's disease, but these patients do not show angiographic evidence of a dark choroid suggesting a lipofuscin storage disease. The RPE dystrophy is characterized by an X-shaped yellowish macular lesion and numerus flavimaculatus retinal flecks. The condition is bilateral, has a dominant inheritance, and starts in middle age with a slow-developing macular lesion. Visual functions are often minimally disturbed for two or three decades. The association between flaveomacular vitilliform macular dystrophy and vascularized pigment epithelial detachment (PED), supports the hypothesis that flaveomacular vitilliform macular dystrophy may be a different subgroup of age-related macular degeneration with specific genetic predisposition. Adult onset foveomacular vitelliform dystrophy (AOFVD) is considered a subtype of pattern dystrophy. Onset occurs during middle age, with an accumulation of yellow-gray macular deposits in the deeper retinal layers. Electro-oculograms are mildly subnormal or normal. Genetic studies suggest an autosomal dominant inheritance with variable penetrance.

Patients with fundus pulverulentus display prominent, coarse, "punctiform" mottling of the RPE in the macular area. Further testing might include an electro-oculogram (EOG) and fluorescein angiography. Angiography may show hypofluorescence (under fluorescence) from increased pigmentation or hyperfluorescence (over fluorescence) due to RPE atrophy. Patients will infrequently show evidence of choroidal neovascularization. Pattern dystrophy has been associated with pseudoxanthoma elasticum and myotonic dystrophy. The visual prognosis is favorable. Usually, good visual acuity is maintained in this inherited macular disease. However, acute visual loss can be caused by the ingrowth of subretinal new vessels. Therefore, if visual acuity decreases or metamorphopsia (crooked lines and different sized squares on an Amsler Grid) develops in these patients, careful fluorescein or Indocyanine Green angiography is advisable. Management should include photodocumentation, laser intervention (if there is choroidal neovascularization), and genetic counseling. There should be annual follow-up.

REFERENCES:
Retinal Quiz April 2000 Review of Optometry Mark T. Dunbar, O.D.
Surv Ophthalmol 1995 Jul-Aug;40(1):51-61 Genetic and molecular studies of macular dystrophies: recent developments. Zhang K, Nguyen TH, Crandall A, Donoso LA. Henry and Corinne Bower. Laboratory for Macular Degeneration, Wills Eye Hospital, Philadelphia, Pennsylvania, USA.
Ophtalmologie 1990 Jul-Aug;4(4):372-6 Francois P, Puech B, Turut P. Service d'Exploration Fonctionnelle de la Vision, Lille. Eye 1990;4 ( Pt 1):210-5 Adult vitelliform macular dystrophy. Brecher R, Bird AC. Department of Clinical Ophthalmology, Institute of Ophthalmology, Moorfields Eye Hospital, London.

Macular pucker, also referred to as epiretinal membrane, is a condition in which a thin, membranous tissue grows over the surface of the retina. Contraction of this membrane or 'scar tissue' causes wrinkling of the retina and may result in subsequent swelling of the retina (macular edema). Just as one would prefer to view a movie on a flat, smooth movie screen, clear vision depends on a smooth retina to accurately receive visual information from our environment. Wrinkling of the retina results in distorted images, while swelling of the retina produces blurred vision.

Demographics

Macular pucker typically occurs in those over age 50, and there is a slightly higher incidence in females. In most cases, the cause is unknown but predisposing conditions include retinal vascular disease (e.g. diabetic retinopathy), retinal tear, prior retinal detachment, and uveitis (ocular inflammation). The condition is mild in most cases and affects both eyes in approximately 25% of cases.

Clinical Appearance & Symptoms

Most epiretinal membranes are clinically insignificant and produce no symptoms or very mild visual disturbances. These membranes are often discovered on routine eye examination and present with a glistening or subtle sheen on the retinal surface. No treatment other than periodic monitoring is required, as approximately 70% of these will remain stable without intervention.

When macular pucker starts to cause symptoms, the membrane is more clearly visualized on the surface of the retina (Figure 1, 2). Definite wrinkling or striae of the retina are observed; the retinal blood vessels appear tortuous where the membrane is contracting and straightened or stretched in the surrounding areas. This produces symptoms of varying degrees of distortion depending upon the degree and location of traction induced by the epiretinal membrane. Careful examination will often reveal retinal swelling, or macular edema, which is responsible for blurred vision. Patients often describe their condition as 'looking through a fish tank. 

Diagnosis

When an epiretinal membrane is discovered, certain diagnostic tests may be requested by your retinal specialist. The purpose of these tests is to evaluate a possible underlying cause of the epiretinal membrane, determine the degree of traction or macular edema caused by the membrane, and plan possible treatment.

The simplest technique is photographic documentation of the epiretinal membrane. Color and red-free photographs provide a valuable baseline for following the progress of membrane formation through time or evaluating a response to treatment.

Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the epiretinal membrane and its effect on the retina. This technology uses laser light to scan the retina and construct an accurate cross-sectional image, non-invasively. The epiretinal membrane can be visualized along with its attachments to the retina, traction and distortion of the retinal architecture, and degree of macular edema (Figure 3). This is very helpful in guiding decisions for treatment.

Fluorescein angiography may be employed in the diagnosis of epiretinal membrane. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the retinal circulation. This technique is very useful for evaluating possible underlying causes of epiretinal membrane due to retinal vascular diseases such as diabetic retinopathy and retinal vein occlusion. The dye also highlights the retinal blood vessels, and depicts the tortuosity often seen in areas of retina under significant traction (Figure 4, 5). Leakage of dye into the retina also provides an indication of the presence and degree of retinal swelling, or macular edema. 

Treatment

When a macular pucker, or epiretinal membrane, causes significant visual loss or symptoms that affect an individual's ability to adequately perform their activities of daily living, consideration is given to surgical intervention. Surgery is the only definitive treatment for effectively removing the membrane and alleviating the symptoms. The procedure is called vitrectomy with membrane peeling and involves removal of the vitreous gel from the eye through tiny openings, followed by peeling of the membrane from the surface of the retina using fine instruments such as micro-forceps. Following removal of the membrane, the retinal architecture usually returns to a more normal state with relief of traction and distortion and resolution of edema (Figure 6).

Visual recovery after vitrectomy with membrane peeling usually occurs over several weeks. Approximately 80-90% of patients report significant improvement in blurred vision and distortion, although many are left with some degree of residual visual loss or symptoms. The cause, duration, baseline vision, and severity of the original macular pucker all play a role in the ultimate prognosis following surgical intervention.

A macular hole occurs when the vitreous gel exerts traction in the area of central vision, the macula. The pulling of the gel on the center of the retina results in the formation of an opening or hole in the central vision. Liquefied gel or fluid may enter this opening and collect under the retina, forming a cuff of fluid around the macular hole. Visual symptoms are caused by the missing retinal tissue in the center of the hole leading to a blind spot, as well as the cuff of fluid which creates distortion and waviness.

Demographics

Macular holes typically occur in individuals in their 50's and 60's. This condition is more common in females. In most cases, the cause is unknown but macular holes have been reported after trauma, laser treatment, macular edema, macular pucker, and retinal detachment. The second eye is affected in approximately 15% of cases.

Clinical Appearance & Symptoms

Most macular holes present with an opening in the central retina surrounded by a cuff of fluid under the retina (Figure 1, 2). At this stage, patients typically complain of blurred central vision with an associated blind spot and distortion. The degree of visual loss, size of the blind spot, and level of distortion are often related to the duration of the macular hole. Sometimes, the duration of symptoms may be uncertain, as patients can often compensate with their unaffected, better-seeing eye. Eventually, patients often note a difficulty in depth perception when one eye is affected, and report problems with reading and performing fine motor tasks with that eye. 

Diagnosis

A macular hole is often diagnosed on clinical examination of the central retina. When a macular hole is suspected or discovered, certain diagnostic tests may be requested by your retinal specialist. The purpose of these tests is to confirm the presence of a true macular hole, identify possible underlying causes of the macular hole, determine characteristics of the hole, and plan possible treatment.

Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the macular hole with its associated retinal traction and fluid. This technology uses laser light to scan the retina and construct an accurate cross-sectional image, non-invasively. The macular hole can be visualized to determine if there is indeed a full-thickness defect in the central retina. OCT is very useful at identifying areas of traction on the retina responsible for the macular hole, as well as depicting collections of fluid within and under the retina.

OCT is also very useful in helping to stage macular holes, which is valuable in planning possible treatment and determining the ultimate prognosis. Macular holes, as previously described, are often caused by traction of the vitreous gel on the central retina (Figure 3). A stage I hole occurs when this traction causes elevation of the central macula (the fovea), without causing a full-thickness hole in the retina (Figure 4). This is important, as approximately 55-60% of stage I holes will resolve on their own through natural release of the vitreous traction (Figure 5); for this reason, they are often followed closely without treatment. With continued traction, the remaining stage I holes progress to stage II in which there is a full-thickness defect or hole in the central vision (Figure 6). The symptoms are much more significant at stage II, and the hole will often enlarge over the next several months without treatment. This typically results in further visual loss and progression to stage III (Figure 7). Finally, in 20-40% of untreated macular holes, the vitreous gel will separate over the hole spontaneously and progress to stage IV (Figure 8).

Fluorescein angiography may be employed in the diagnosis of macular hole. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the retinal circulation. This technique may be useful for evaluating possible underlying causes of macular hole or differentiating macular hole from other conditions such as macular edema, macular pucker, and macular degeneration. Fluorescein angiography of a macular hole shows a focal bright area in the central retina, corresponding to the defect (Figure 9). 

Treatment

Most stage I macular holes are observed periodically for spontaneous resolution or progression to stage II. A highly symptomatic stage I hole may be a candidate for surgery after a thorough discussion with your retinal specialist. A stage II or higher macular hole is usually recommended for surgical intervention. Those who are not candidates for surgery (health reasons, physical limitations) or who do not desire surgery will typically progress until the vision reaches approximately 20/200. Although the central visual loss is rather severe at this level, patients will routinely preserve their side vision in the affected eye. Additionally, they often can compensate with the unaffected eye.

Surgery is the only definitive treatment for effectively removing the traction from a macular hole, sealing the central defect, and attempting the restore lost central vision. The procedure is called vitrectomy and involves removal of the vitreous gel and its attachments to the retina through tiny openings in the eye. Sometimes, the inner-most layer of the retina, the internal limiting membrane, is also peeled to assure complete relief of traction from the macular hole. At the end of the procedure, the vitreous cavity is filled with a gas bubble to gently press against the hole and help seal the edges. This bubble lasts from 2-6 weeks, and patients cannot see normally through the bubble until it disappears naturally. Patients are often asked to position with their face down for several days to 'float' the bubble against the macular hole and help close the defect. After macular hole surgery with a gas bubble, one cannot fly in an airplane or travel to high altitude since the bubble will expand under these conditions and cause a potential dangerous increase in eye pressure. In rare cases, an oil bubble is used to seal the hole instead of gas; patients may fly with an oil bubble, but do require a second surgery to have this type of bubble removed.

Visual recovery after vitrectomy for macular hole usually occurs over several weeks. The first sign of visual recovery occurs after 2-6 weeks, following reabsorption of the gas bubble. Over 90% of macular holes are successfully closed at this stage after a single surgery (Figure 10). In these cases, patients typically report significant improvement in blurred vision and distortion, although many are left with some degree of residual visual loss or symptoms. The cause, duration, baseline vision, stage, and severity of the original macular hole all play a role in the ultimate prognosis following surgical intervention. Cataract progression is common following this type of surgery, but is usually not of great concern since most macular hole patients already have mild baseline cataracts due to their age. Less common complications include retinal tear (2%) and retinal detachment (<1%), both of which are generally treatable. Bleeding and infection are rare complications associated with any surgery.

Diabetic retinopathy is the most common cause of blindness in individuals between 20 and 74 years old. Elevated blood glucose for prolonged periods of time causes damage to the retinal blood vessels (along with the kidneys and nerves). Such damage to the blood supply of the retina can result in abnormal bleeding, swelling of the retina, poor blood flow to the retina, and/or scarring of the retina.

Demographics

Approximately 10 million new cases of diabetes are diagnosed every year. It affects approximately 6% of individuals between 45 and 64 years old, and 11% of individuals over 65. Diabetic retinopathy of some degree is present in approximately 90% of type 1 (juvenile) diabetic individuals after 10 to 15 years; the most severe form occurs in approximately 25% during this time. For type 2 (adult-onset) diabetics, 84% of individuals taking insulin and 53% not taking insulin will develop retinopathy between 15 to 20 years; 25% will develop the most severe form after 25 years. Macular edema (swelling of the central retina) affects about 20% of diabetics and is a common cause of visual loss.

Clinical Appearance & Symptoms

Diabetic retinopathy is subdivided into two forms: non-proliferative diabetic retinopathy (NPDR) and a more severe form, proliferative diabetic retinopathy (PDR).

NPDR starts with damage to the retinal blood vessels from prolonged elevation of blood glucose. The blood vessels develop tiny weak areas called microaneurysms. Over time, these microaneurysms can rupture and leak. This can result in retinal bleeding, or hemorrhage. Fluid from the blood stream can also leak into the retina and cause swelling, a condition called macular edema. Fats and proteins from the blood stream may leak into the retina as well, and are referred to as hard exudates. Macular edema tends to cause central blurring of vision and/or distortion. Over time, poor blood supply can result in death of nerve cells responsible for fine vision (a process called macular ischemia); this can lead to a permanent central blind spot with corresponding untreatable decreased central vision. (Figure 1, 2)

After prolonged poor blood flow, the retina produces substances that promote the growth of new, abnormal blood vessels (a process called retinal neovascularization). Retinal neovascularization marks the shift from non-proliferative to proliferative diabetic retinopathy (PDR) and is a very serious condition. This development of new blood vessels may appear logical, as the old, original blood vessels are often permanently damaged and poorly functioning. However, the retinal neovascularization process tends to do more harm than good over the long-term. The new blood vessels are fragile and tend to bleed into the vitreous cavity, a condition termed vitreous hemorrhage. A vitreous hemorrhage can cause significant floaters in the vision (from floating blood cells) and may cause transient near-total blindness if the hemorrhage is particularly dense. The new blood vessels may also grow along the surface of the retina, scar, and contract; this can pull on the retina and cause a very serious condition called traction retinal detachment.

Diagnosis

When a diabetic retinopathy is identified, your retinal specialist may perform additional testing to further evaluate the condition. The purpose is usually to identify areas of macular edema, macular ischemia, and retinal neovascularization (see above)

Fluorescein angiography may be employed in the diagnosis of retinal vein occlusion. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the ocular circulation. Sites of leakage can be identified that correspond to areas of macular edema or retinal neovascularization. Areas of compromised circulation can also be localized in evaluating macular ischemia and general retinal ischemia. (Figure 3, 4)

Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the retina and any associated macular edema (Figure 5). This technique is very valuable in quantifying the degree of fluid and monitoring response to potential treatment (Figure 6). It can also very effectively show any traction on the surface of the retinal tissue.

B-scan ultrasonography is used to evaluate the retina when the view is blocked by hemorrhage (bleeding) in the vitreous cavity. The sound waves of the ultrasound can penetrate the bloody vitreous and depict the anatomic status of the underlying retina. 

Treatment

The most important aspect in the treatment of diabetic retinopathy is long-term control of blood glucose. Patients should monitor their glucose daily and follow their hemoglobin A1c level with their diabetes doctor. They should also control any coexisting conditions that can worsen retinopathy; these include hypertension and elevated cholesterol/lipids. 

Retinal intervention is generally aimed toward preventing visual loss from macular edema and complications of proliferative diabetic retinopathy.

Macular Edema:
Macular edema is frequently treated with laser. Research studies have shown that laser treatment results in 1 the rate of significant visual loss when compared to those who did not receive laser. Unfortunately, most patients treated with laser do not gain significant vision. In an attempt to improve visual outcomes, retinal specialists have been injecting experimental medications into the vitreous cavity to target macular edema . These medications are currently offered on an off-label basis to patients who may be good candidates after an extensive discussion of risks and potential benefits. Currently, these medications include Kenalog (a corticosteroid) and Avastin (an anti-neovascular agent). In certain cases, vitrectomy surgery may be recommended to treat specific causes of macular edema.

Proliferative Diabetic Retinopathy:
Complications of proliferative diabetic retinopathy result from retinal neovascularization, so this process is the target of most treatments. Untreated retinal neovascularization may result in vitreous hemorrhage and/or traction retinal detachment. The main procedure for attempting to control retinal neovascularization involves the use of laser; this treatment is called panretinal photocoagulation. The peripheral retina is treated extensively with laser to target abnormal blood vessels and prevent complications. Research has shown that an individual with specific characteristics warranting laser will have 1 the risk of significant visual loss compared to those not undergoing laser treatment. Unfortunately, individuals do not typically gain vision after this type of laser treatment. 

Vitreous Hemorrhage:
When a vitreous hemorrhage develops, the patient usually experience significant floaters or diffuse blurring (blindness) in one eye. The hemorrhage will often clear on its own over several weeks, so immediate intervention is often unnecessary. However, there are often times when the hemorrhage is slow to clear or new hemorrhages continue to occur. In these cases, vitrectomy surgery is often recommended (see section on Treatment/Vitrectomy). In this procedure, the vitreous gel is removed along with the blood that fills the vitreous cavity. At the time of surgery, laser is usually applied to treat the retinal neovascularization that is suspected to be the source of bleeding.Traction Retinal Detachment:

With traction retinal detachment (Figure 7), vitrectomy surgery is often performed to relieve the traction on the retinal surface caused by scar tissue and allow the retina to lay flat on the back wall of the eye (Figure 8) after vitrectomy surgery). The procedure involves peeling of the scar tissue, or membranes, from the retinal surface using microscopic instruments such as forceps, scissors, and pics.

Central serous chorioretinopathy is a condition in which "blisters" of fluid collect under the retina, or under the tissue that nourishes the retina, the retinal pigment epithelium (RPE).

Demographics

This condition typically occurs in younger adults between the ages of 30 and 50, although there have been many reported cases in older individuals. It is also more common in men, affecting approximately 3 times as many males as females. Central serous chorioretinopathy is often thought to result from stress, and many affected individuals are labeled as "type A" personalities. Other associations include pregnancy, renal disease, and steroid use.

Clinical Appearance & Symptoms

Central serous chorioretinopathy is often suspected when an individual presents with "blisters" of fluid under the retina or RPE (Figure 1). The patient often reports central blurring of vision, distortion, and micropsia (objects appearing smaller). There is often a shift in focus toward farsightedness.

Diagnosis

When central serous chorioretinopathy is suspected, certain diagnostic tests may be requested by your retinal specialist. The purpose of these tests is to confirm the diagnosis, evaluate the source of leakage of fluid, quantify the amount of fluid, and possibly guide treatment.

Fluorescein angiography may be employed in the diagnosis of central serous chorioretinopathy. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the ocular circulation. "Hot spots" of leakage can often be identified as the source of fluid causing the condition (Figure 2, 3, 4). If treatment (such as laser) is recommended, the angiogram is often used to guide treatment of these "hot spots."
Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the retina, RPE, and fluid accumulations from central serous chorioretinopathy (Figure 5, 6). This technique is very valuable in quantifying the amount and location of fluid collections as well as following its resolution during healing or after treatment.

Treatment

Most cases of central serous chorioretinopathy resolve without treatment after several weeks or months. In certain circumstances, treatment is recommended. These include non-resolving fluid, a need for more rapid visual recovery, and a poor outcome in the other eye without treatment. When treatment is indicated, a laser is often used to "seal" an area of leakage identified on the angiogram. Thermal laser can not be used if the "hot spot" is directly in the center of vision, as the laser burn will damage the fine central vision. In these cases, a technique called photodynamic therapy may be recommended (see procedures). This involves an off-label use of a current macular degeneration treatment. A photosensitizing dye in injected intravenously and activated in the eye with a low energy (non-thermal) laser, resulting in no burn.

The prognosis with central serous chorioretinopathy is considered excellent, although there are certainly severe cases that result in significant, permanent visual loss in one or both eyes.

Age-related macular degeneration is the most common cause of legal blindness in individuals 65 years or older. This condition affects the macula, the sensitive central portion of the retina that is responsible for fine vision (reading, driving, recognizing faces) and color perception. The condition is broadly divided into two forms: a "dry" form and a "wet" form. The dry form involves aging changes in the tissue that nourishes the retina, the retinal pigment epithelium (RPE). This layer of tissue lines the wall of the eye underneath the retina and is supplied by a network of blood vessels known as the choroid. In the wet form of macular degeneration, abnormal blood vessels grow under the retina from the choroid. These new blood vessels (referred to as choroidal neovascularization) tend to leak fluid, blood, fats, and/or proteins from the bloodstream into the space under the retina; this is where the name "wet" comes from.

Demographics

Age-related macular degeneration, as its name implies, affects older individuals. As many as 10% of individuals over 65 and 35% of individuals over 75 will show some signs of this condition. It almost always affects both eyes to some degree, and usually starts with the dry form. The wet form affects approximately 10% of patients with macular degeneration. The most common uncontrollable risk factors for age-related macular degeneration include advanced age and genetic tendency for the disease. However, there are some controllable risk factors that patients are encouraged to actively address: cigarette smoking, nutritional deficiency, and cardiovascular risks such as hypertension.

Clinical Appearance & Symptoms

The dry form of age-related macular degeneration often starts without symptoms. Upon examination of the retina, patients show changes in the layer that nourishes the retina, the RPE. There are frequently "yellowish" deposits in the RPE layer, known as drusen. The RPE may also show dark clumps known as RPE hyperpigmentation. Finally, the RPE may begin to degenerate to a point where patches of RPE begin to disappear; this is referred to as RPE atrophy and is responsible for most cases of visual loss associated with dry macular degeneration. With the dry form, visual loss tends to be very gradual. Patients may note distortion, dark spots, or blind spots in their vision. Many individuals with dry macular degeneration may maintain excellent visual function for many years. However, those with large patches of RPE atrophy in the central macula may become legally blind from the dry form. Wet macular degeneration tends to be the more serious form of this condition. As explained above, abnormal blood vessels grow from the choroid in a process known as choroidal neovascularization. These blood vessels may grow within the RPE or through the RPE into the space under the retina. The wet form gets its name from the resulting leakage of fluid, blood, fats, and/or proteins from the bloodstream that typically occurs with choroidal neovascularization. With the wet form, patients often note distortion of images in the earlier stages. With time, patients note dark spots or blind spots as the retina begins to deteriorate over the damaged RPE. Normally, it is the RPE that is responsible for nourishing the retina and keeping it healthy; a damaged RPE is unable to effectively perform this function. In the later stages of wet macular degeneration, the abnormal blood vessels under the retina become scarred. Scar tissue in the central vision can have severe visual consequences; most patients will become legally blind at this stage (vision <20/200) and will not be able to read or recognize faces with the affected eye(s). On a positive note, patients with macular degeneration almost never become totally blind. The side vision is almost always preserved, as the macula (central vision) is generally the only area of the retina affected.

Diagnosis

When macular degeneration is identified, your retinal specialist may perform additional testing to further evaluate the condition. The purpose is usually to identify areas of choroidal neovascularization so that potential treatment may be planned or followed. Fluorescein angiography may be employed in the diagnosis of macular degeneration. In this procedure, a dye is injected into an arm vein and travels through the circulatory system to the eye. The dye acts as a tracer and is photographed as it passes through the ocular circulation. Sites of leakage can be identified that correspond to areas of choroidal neovascularization in wet macular degeneration. Areas of drusen and RPE atrophy can be identified in dry macular degeneration. Optical coherence tomography (OCT) is commonly used to obtain a high-resolution image of the retina and any associated thickening from fluid leakage due to choroidal neovascularization. It can sometimes also show the location of the abnormal blood vessels. This technique is very valuable in quantifying the degree of fluid and monitoring response to potential treatment.

Treatment

The most important aspect in the treatment of age-related macular degeneration is prevention. Patients who smoke are encouraged to stop immediately. Cardiovascular risk factors such as hypertension and elevated cholesterol should be controlled as well as possible. Those with nutritional deficits should improve their diets and consider supplementation with multi-vitamins. A specific higher risk group of patients will benefit from a specialized nutritional supplement with high doses of vitamin A, C, and E, as well as zinc; please see the section of this website on prevention for further information on this formulation (the AREDS formula). Your doctor can determine if you would benefit from this product.   Retinal intervention is generally aimed at preventing visual loss from choroidal neovascularization. Each therapy is explained in further detail in the Treatments section of this website. There is also a Medications section that reviews current pharmaceuticals used in treating wet age-related macular degeneration.

Antineovascular Agents: Choroidal neovascularization is triggered by chemicals that are released from the retina. New drugs have been developed that block these chemicals and prevent or slow the growth of new blood vessels. These are termed antineovascular agents and include the drugs Macugen, Avastin, and Lucentis. These drugs are injected directly into the eye and have shown benefits in preserving vision compared to no treatment. Unfortunately, many patients will not gain significant vision after treatment and a certain percentage will continue to lose vision despite treatment. Retreatment is typically required at 4 to 6 week intervals, depending on the drug used.

Photodynamic Therapy: This treatment involves a combination of drug and laser. A light sensitive drug (photosensitizer) is injected into an arm vein and travels to the retina through the circulation. After 15 minutes, the drug is activated with a low-energy laser targeted at the abnormal growing blood vessels (choroidal neovascularization). This therapy has also shown benefit in preventing or slowing visual loss compared to no treatment. As with the antineovascular agents, most patients will not gain significant vision after treatment; retreatment is typically required at 3 month intervals.

Thermal Laser: In certain cases, a thermal (hot) laser is used to burn the abnormal blood vessels and prevent further growth and corresponding visual loss. The above treatments have largely replaced this method, although thermal laser still has a place in the treatment of wet macular degeneration. Your doctor will discuss all reasonable options for your particular case and decide upon the best treatment with you.