Good Hope Eye Clinic

Refraction: a test for spectacles

David Kinshuck

What is a 'refraction' test

This is a test to measure your eyesight for glasses. It is the name of the test you have at your local optometrist. However, the hospital specialises in refractions for people with problems such as poor vision, or double vision. The test takes 20 - 30 minutes.

Please bring you glasses with you, even if they are out of date, as they still help the hospital optician decide if you need a new pair. The test will be carried out by one of the optometrists in the department.

If you do need new glasses you will be given a prescription. Take the prescription to your local optometrist to have your glasses made. The hospital optometrist will advise if you are entitled to NHS glasses before you take your prescription.

When you collect your new glasses give yourself several days to settle down to the new lenses, especially if you plan to work or drive.

The refraction in the hospital is only available if you attend the Eye Clinic. If you are discharged you should consult your local optician if you need an eye examination.

 

Refractive error

You may need glasses if you are long-sighted (hypermetropic), short-sighted (myopic) or have astigmatism in one or both eyes. See this page,   BBC   See refraction animation ,  presbyopia animation

 

Long-sighted: hypermetropic

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Light focuses behind the eye; the eye is usually shorter than average.
If you have had an operations and the lens/cataract is removed, and there is no lens implant used to replace it, this makes your eye very 'hypermetropic'    BBC WP

Shortsighted (myopia)

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Your eye is slightly longer than average. The retina lines the back of the eye like wall paper; it is the 'film' of the eye.

As the retina is 'stretched' if you are myopic, retinal disturbances are slightly more likely. BBC.    Wilkipedia

Astigmatism

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This occurs when the shape of the eye is more like that of a 'rugby ball' than that of a 'football'. You will need glasses to see clearly, otherwise your sight will be blurred. diagram   text BBC

Presbyopia

As you get older, the lens of our eyes becomes rigid and cannot changes its focus. You need glasses for reading to make reading images focus on your eye (or at least different glasses for reading). animation  & www.contactlenses.co.uk

 

Refractive surgery

Many people ask ophthalmologists for advice about refractive surgery, and opinions vary widely. If you want refractive surgery, read up...here are the NICE reports.

Here are some useful points that may help some people decide. Many people have now had refractive surgery, and most are very pleased. Mind you, very few of these are ophthalmologists.
No refractive surgery is carried out at Good Hope Hospital.

 

  1. If you are younger than 20y, your eye is still growing, so it is unwise to have refractive surgery.
  2. There are many new types of contact lens that appear very safe...I appreciate not 100% safe, but serious problems are very rare. I would ask, why have laser when such contact lenses may do the trick?
  3. Laser does have risks, although serious complications are rare.
  4. The people who need laser the most such as 'high myopes' (e.g. -10 dioptres or more) or 'high hypermetropes' can have laser, but the results not completely predictable. Surgery for high myopes is more complicated, as explained on the links above.
  5. Once you reach the age of 45y, you will need a different pair of glasses for reading than your distance pair. This is explained here and above.
    Even with laser you cannot be focused for reading and distance simultaneously, so even with laser you will still need glasses for one or other.