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Eye tests and examinations

Adults and children are usually advised to have a sight test or eye test every two years, or more often if advised by a doctor or optometrist.

If you don't qualify for free NHS sight tests, private fees apply. NHS eye tests are free in Scotland.

Here's a brief guide to the special eye tests your eye care specialist may perform during an eye examination. In addition to a complete examination of your eye, your eye specialist may want to arrange one of the following eye tests.

Applanation method

This eye test helps eye care specialists diagnose glaucoma by measuring the amount of pressure needed to flatten a portion of the cornea. This is often done by placing a dye in the eye from a thin strip of paper coated with the dye. This dye stains the front of the eye and enables a better eye examination. The patient is given local anaesthetic drops and the pressure is measured using a tonometer held in the hand or attached to a slit lamp.

Corneal and retinal topography

These are computerised tests used to create a ‘map’ of the curvature of the cornea or surface of the retina. This test is not necessary during a routine eye examination. The analysis will show distortions of the surface such as swelling or scarring, as well as conditions such as astigmatism. This corneal test may be used to evaluate patients before they undergo any refractive surgery, corneal transplants, as well as for fitting contact lenses. The retinal test may be used to follow patients with serious conditions of the retina.

Fluorescein angiogram

The fluorescein angiogram is an eye test used to evaluate the blood circulation in the retina. It is useful in helping to diagnose diabetic retinopathy and retinal detachment. During this eye test, a special dye, called fluorescein, is injected into a vein in the arm. The dye quickly travels to the blood vessels inside the eye. Once it reaches the eye, a specialised camera equipped with special filters that highlight the dye is used to photograph the fluorescein as it circulates though the blood vessels in the back of the eye. This will enable the doctor to diagnose any circulation problems, swelling, leaking or abnormal blood vessels.

Pupillary dilation test

During this eye test, the eye care specialist places special drops in the eye that cause the pupil to dilate (expand). Dilating your pupils means your retina can be examined for any signs of disease.

Refraction test

This eye test determines your glasses prescription. The patient looks at a chart, usually six metres away, or in a mirror simulating six metres distance, and tries to read it while looking through a special instrument known as a phoropter. The eye care specialist moves lenses of different strengths into place for the patient to look through. He or she will ask you which of the choices looks clearer or more blurry and based on these answers will determine the appropriate prescription needed for glasses or contacts. This eye test will also identify presbyopia, hyperopia, myopia, and astigmatism.

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