focalise eyewear blog

What does Sphere really mean?

2008-03-26T23:33:04+11:00

Just a quick one to deal with an issue in a recent customer order. The customer requested reading glasses but entered a Sphere correction that started with a "-".

The “Sphere” column indicates your level of long or shortsightedness, a “+” indicating Hypermetropia (long-sightedness) and a “-“ indicating Myopia (short-sightedness).

For reading glasses we'd expect to see a "+" measurement for the Sphere column or a measurement in the ADD column.

More on Lenses

2008-03-24T17:23:44+11:00

I just wanted to add a little more information about the types of lenses that are commonly available (and that'll you'll be able to order at Focalise Eyewear).

Standard plastic CR39 - we use 1.49 index lenses as standard - these lenses are ideal for most prescriptions - for powers that are beyond +3.00 or -3.00, these lenses may give a distorted affect.

Plastic 1.56 - our standard thin lenses - again should be fine for prescriptions with powers that are between +3.00 and -3.00.

Plastic 1.61 - ideal for powers between +5.00 and -5.00. These are more than 25% thinner than our standard plastic lenses.

Plastic 1.67 - a popular thin lens that is 15% thinner than 1.61 index and 25% flatter - these are good for prescriptions between +7.00 down to -7.00.

Plastic 1.74 - the thinnest plastic lenses currently available in the market - over 50% thinner than our standard plastics and 30% lighter than the glass equivalent - excellent for mid to high powers, but obviously a bit pricey.

Glass 1.7 - a "budget" thin lens for high power prescriptions - obviously heavier than plastic equivalents.

Glass 1.8 and 1.9 - rarely used, but can be for high powers - expensive options.

Please note that the above options cover the range we offer in single vision lenses only. We only currently stock 1.61 index lenses for bifocals and varifocals.

Lenses Explained

2008-03-17T22:46:24+11:00

I had a question the other day about different lenses, so I thought I post a little bit of information about the subject.

Lenses are either made of plastic or glass - most lenses sold today are plastic. Usually it's only when extremely thin lenses are required for very high prescriptions that glass may be the better option. Otherwise plastic is the more practical and lighter choice.

The different lens numbers (1.49, 1.56, 1.61, etc.) refer to the refractive index of a lens - it's a measure of how the lens bends light.

The higher the number; the thinner the lens. This is because lenses that bend light more than others have a higher refractive index and need less material to achieve the same eyesight correction (hence are thinner).

So 1.49 index does not mean 1.49mm. It refers to the lens refractive index.

However, less material in thinner lenses doesn't make them cheaper - the thinner you go, the more expensive the lenses are!

I'll post again soon about the different indexes you can get at Focalise.

More on Prescriptions

2008-03-11T11:13:06+11:00

Following on from the last post, there were a few other things I thought I might add.

In case you weren't sure, the higher the numbers the stronger the prescription.

Another thing. Your glasses prescription and contact lens prescription will differ slightly. This is due to the contact lens being physically closer to your eye, usually resulting in a slightly different prescription to your glasses. Also your contact lens prescription doesn’t always show your degree of astigmatism.

The following is an example of a prescription:

(Click on the image to enlarge). This prescription is read:

“Right eye, -2.75, -1.00 axis 180. Left eye, -2.50, -0.50 axis 180. Add +2.25”.

This means that the person is shortsighted or myopic (indicated by the " –" sign in front of the sphere measurement), with a slight astigmatism at an axis of 180 degrees from the horizontal. There is a reading addition of +2.25 indicating presbyopia.

The “Sphere equivalent” measurement is achieved by adding half of the cylinder to the sphere. So in the case above the sphere equivalent is:

RE: (-)1.00 / 2 + (-)2.75 = (-)3.25 and LE: (-)0.50 / 2 + (-)2.50 = (-)2.75

What Does My Prescription Mean?

2008-03-10T16:01:27+11:00

It's a question we get asked regularly, so I thought I would give you a quick summary of what we need to see to process your prescription.

First, make sure you have an up-to-date prescription (not more than two years old). Then, make sure that the prescription includes the following measurements:

Sphere (or SPH) – this gives the strength of the lens (plus for long-sightedness, minus for short-sightedness)

Pupiliary distance (or PD) – this is the horizontal distance between your pupils measured in millimetres (as a guide, the average is between 60mm and 66mm) - we'll use an average if we can't get this info

Cylinder (or CYL) – this is your astigmatism correction. Not everyone has astigmatism (when the eye is slightly rugby-shaped) so don't worry if you don't have a measurement for this

Axis – this corrects an astigmatism and tends to be an angle measurement like 150 or 90

Addition (or ADD) - this is a number we add to your distance prescription to give the reading measurement for your bifocals. For bifocals it's really important you get your optician to tell us what position the reading and distance segments should be - we can use an average again, but it may lead to some blurring in the final glasses,

And by the way, OD and OS - it means your right eye and left eye (OD and OS are latin abbreviations for right eye and left eye)

Specsavers are coming...Beware!

2008-03-01T16:26:50+11:00

Specsavers are in Australia, having just opened stores in Melbourne. They're massive in the UK and now they're over here to wrestle part of the billion dollar market out of the previously dominant hands of Luxottica (otherwise known as OPSM, Budget Eyewear and others). But will Aussie consumers be getting a good deal with this extra competition?

You can check out the Specsavers media release about their new launch at www.specsavers.com.au.

The truth, however, is that it isn't just a choise between Luxottica and Specsavers for Aussie consumers. Going online and buying your glasses that way delivers by far the best value - whatever these giant retailers would have you believe.