Your Prescription Explained

Your prescription explained

What is myopia?

  • In myopia (short sightedness), the eye is longer than normal or the cornea is too steep, so that light rays focus in front of the retina. Near objects are clear but distant objects appear blurred.

What is hypermetropia?

  • In hypermetropia (long sightedness), the eye is shorter than normal or the cornea is too flat, so that light rays focus behind the retina. Light rays from close objects such as pages of a book cannot focus clearly on the retina.

What is astigmatism?

  • In astigmatism (distorted vision), the cornea is more curved in one direction than in the other. It is shaped more like a rugby ball, than a football. This results in vision being blurred for both near and distant objects.


What do the numbers in my glasses prescription mean?

Your prescription for glasses or contact lenses is a series of numbers in different boxes.

Here’s an example:

           SPH         CYL            AXIS

OD    -2.75D     -0.50D            90

OS     -3.25D     -0.75D           180


The above prescription refers to someone with short sight and mild astigmatism. OD refers to your RIGHT eye prescription; OS to your LEFT eye prescription.


The SPH (sphere) box shows how long or shortsighted you are, measured in dioptres (D).

The CYL (cylinder) box shows the strength of any astigmatism, also measured in dioptres.

The AXIS box shows the rotational position or angle of the astigmatism on the eye.


SHORT SIGHT (myopia) is shown with a minus (-) sign, either before or above the value, in the SPH box. LONG SIGHT (hypermetropia) is shown with a plus (+) sign, either before or above the value, in the SPH box. ASTIGMATISM can be plus (+) or minus (-), and this is shown in the CYL box.


The range of sight correction procedures offered by Miss Saw covers any level of spectacle prescription. Laser surgery covers the range +4 to -10D and up to 4D of astigmatism. Lens implants can cover a wider range of focusing errors and can be combined with laser procedures where necessary in order to correct very high spectacle prescriptions. There is considerable overlap between treatment ranges for different procedures. After a comprehensive assessment at your initial consultation, Miss Saw will take a number of factors into account to make a recommendation for the procedure that will suit your eyes best.

Don't take our word for it

Reviews from happy patients

Margaret Picken
I have only the highest praise for Valerie Saw and gratitude for her professionalism, kindness, and clear and calm advice before, during and following YAG laser capsulotomy on my right eye and the...
Kenneth Fish
Valerie Saw carried out cataract surgery on me as a private patient in April of 2011 at Moorfields Eye Hospital in London. I am absolutely delighted with the outcome and can't praise her skills...
Christ Stott
Ms Valerie Saw is a friendly and very professional eye surgeon. She is very thorough during the examination. Valerie is courteous and immediately put me at ease providing just the right amount of...
Julie Brownson
I could not be happier with my decision to have laser eye surgery to correct short-sightedness/astygmatism performed by Miss Saw. Miss Saw is professional, calm and reassuring. She talked me through...
Carole Jones
What a lovely lady! What a fantasitic surgeon......My husband has only had one good eye since birth, and that was getting worse and worse. He had to wear glasses all the time and it makes things...
Heather Pearce
Absolutely delighted with result and service, couldn't be happier!
Bola Awoyinka
I had absolutely no idea of what to expect when I discovered cataracts in my eyes. And I was living abroad. On my first visit, during my initial consultation Valerie explained in very simple but...
Katie Price
Having laser eye surgery was the best decision I have ever made and, given the serious nature of the surgery, I researched the procedure and the best surgeon for me before commiting to it.The whole...
Kevin Carnegie
I was considering having laser eye surgery on my right eye. I consulted Valerie who diagnosed me with keratoconus. Valerie recommended inserting a Keraring in my eye instead of laser treatment. The...
Ruth Rowland
I’m very happy with my diagnosis and treatment. I elected for laser surgery in my right eye to improve short sightedness. Ms Saw diagnosed Blepharitis, a condition I had suffered with for some time...

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