What happens during a sight test?

A guide to an eye examination at Enderbys

Regular sight tests are essential for clear vision as well as an excellent way for your optician to check the health of your eyes and check for other medical conditions. There are numerous ways to complete each sight test, listed below are a number of the checks that your optician may perform during a sight test at Enderbys. You may not require all of the checks listed below, your optician will tailor your eye examination to suit your individual needs and guide you through the examination explaining each part as necessary.

1. Non Contact Tonometer (NCT)

The Non Contact Tonometer measures the pressure inside your eye, the intraocular pressure. It does this by puffing air towards your eye. It is painless and quick. It is used mainly to screen for glaucoma, a condition in which the intraocular pressure may be raised.

2. Central Field Screening

This test is done with an instrument which uses frequency doubling technology (FDT). You press a button when you see a flickering light appear in different positions while you are looking at a target in front of you. It is quick and easy and can help to locate areas of the eye that are less sensitive than normal.

3. The Ophthalmascope

An ophthalmascope is a hand held instrument which allows your optician to shine a light into your eye and focus through the different layers to the retina at the back. It can reveal anything that might be in the way, such as a cataract, and it gives your optician an opportunity to examine the back of your eye including the blood vessels and the optic nerve where it enters the eye. This is an important part of the sight test as it sometimes reveals signs of general health conditions, such as high blood pressure and diabetes, or eye conditions such as glaucoma. All being well the eye will look healthy.

4. The Cover Test

The cover test is used to see how well your eyes line up. By covering and uncovering each eye we can see what adjustments your eyes may need to make them work together. The cover test will show if there is a squint or if there is some difficulty in lining the eyes up properly.

5. The Confrontation Test

The confrontation test is a simple check on the size of your field of vision. Your optician sits facing you and, with one your eyes covered, asks where you can see a hand movement at the edge of vision with the uncovered eye.

6. The Ocular Motility Test

The ocular motility test checks the muscles that control your eye movements. You will be asked to follow a small target as it is moved from side to side and up and down while your optician observes how well the eye movements are coordinated. If any of the six muscles that control each eye are not functioning correctly the coordination will be upset.

7. The Convergence Test

The convergence test is like the ocular motility test but it is used to check how well the eyes can converge (come together) to view near objects. If the convergence is poor there are eye exercises that can help or help can be incorporated in your spectacles.

8. The Pupil Reaction Test

Your optician will shine a light into each eye to see if it causes the pupil to contract. They will also be checking to see if the left pupil contracts when light shines into the right eye and if the right pupil contracts when light shines into the left eye. It will be necessary to shine a light back and forth to observe how each pupil reacts. The reactions should be equal in each eye and the pupils should contract when your eyes converge.

9. The Retinoscope

A retinoscope is a hand held instrument which your optician will use to shine a light into your eye and observe the reflected light in the pupil. Depending on how the reflected light moves we can obtain a very good indication of the spectacle power you require before we ask for your input to help us decide the best power to prescribe for you.

10. The Slit Lamp

The slit lamp is a binocular microscope which is used to see the structure of your eye in great detail and in 3D. It can be used to look at the front part of the eye and the deeper layers including the retina while it shines a light into your eye to illuminate it. It is called a slit lamp because the light that shines into your eye can be made very thin, like a slit, when necessary.

11. Finding The Right Correction (Refraction)

When we have done the retinoscopy we will have a good idea of your requirements but we will ask you how well you can see with some slightly different lenses to find the very best correction for you. Sometimes people worry that they will not know which option to choose during this process. Don’t worry, it is perfectly alright to say if you can’t see any difference as that is also helpful to your optician.

12. Humphrey Field Analyser and Henson Field Screener

If the central field screening with the FDT shows some reduction in sensitivity we will repeat the the test, either with the same instrument or on our Humphrey Field Analyser (HFA) or our Henson Field Scanner. The HFA is the gold standard, used in most hospital eye departments, while the Henson is an easier test for people who find visual field testing difficult to do. It is common to find some inconsistencies in visual field testing so by repeating the test we can be happier that the results are valid.

13. Goldmann Tonometry

If the intraocular pressure readings are borderline or a bit high with the non contact tonometer we will check the results with Goldmann tonometry. This is the gold standard for reading of intraocular pressure. We will need to put a drop into each eye to do this test, but it is easy to do and is not uncomfortable.

14. Optical Coherence Tomography (OCT Screening)

The OCT scans your eye to reveal its structure in great detail. It works on a similar principle to ultrasound but because it works with light it is much more accurate.

Having an OCT scan is similar to having a photograph taken except that the the process takes around 3 or 4 seconds to collect all of the information. Your optician will ask you to look at a target and try to keep your eye still while the scan is taking place. The procedure is quick and easy and the results are available straight away.

Enderbys is proud to be one of the opticians who offer their patients OCT Screening. To find out more about this ground breaking technology please visit our OCT Screening page.