Eye Tests

What happens when I go for an Eye test?

Eye examinations at Perfect Vision usually last about half an hour, during your examination your optometrist may perform one or more of the following tests. The test is non invasive and easy to do

Retinoscopy

This is one of the first tests to be performed in an eye examination and it will give your optometrist an idea of what kind of prescription you may need. In a darkened room, you’ll be asked to stare at a target, such as a large letter E. The optometrist will shine a light into your eyes and will look at the way your eyes reflect light when different lenses are passed in front of them.

Refraction

This test fine-tunes the prescription estimated by the retinoscopy. An instrument called a phoropter will be put in front of your eyes and you will be asked which of each choice of two lenses looks the clearer. Based on your answers, the optometrist will be able to determine which exact prescription is best for you. Refraction tells you how long-sighted, short-sighted, astigmatic or presbyopic you are.

Visual acuity

The visual acuity test is the one most people think of when they think of an eye exam. You will be shown an eye chart and asked to say what’s on it. Adults are usually shown letters of the alphabet, while young children are often shown pictures.

Cover test

For this test, your eyes will be alternately covered while you focus on a distant object. By looking at how much each eye has to move to focus on the object, the optometrist can detect strabismus (eye turn), which can lead to amblyopia (lazy eye), poor depth perception and other conditions.

Slit lamp test

The slit lamp examination is like looking into your eyes through a powerful microscope. The instrument used is called a biomicroscope and it allows your optometrist to get a close look at the internal structures of the eye. The eyelids, cornea, iris, conjunctiva, retina, optic nerve and macula are among the things that can be seen with a biomicroscope, and cataracts, macular degeneration, diabetic eye disease and corneal ulcers can all be detected using this test.

Tonometry

This measures the pressure inside your eye, which is also called intraocular pressure. It is used to test for glaucoma and often involves a non-contact tonometer, also known as the “puff of air” test. This involves having a puff of air directed at your eye. The machine will calculate your intraocular pressure on the basis of your eye’s resistance to the air. It is completely painless. For the other type of glaucoma test, your eye needs to be numbed and the optometrist will do this by giving you a yellow eyedrop. Once the drop has taken effect, you’ll be asked to stare into the slit lamp while the optometrist touches you on the front of each eye with a bright blue glowing instrument. This may not sound nice, but it is painless.

Dilation

The pupil (the black spot in the middle of your eye) is effectively the hole through which your optometrist looks into your eye. The larger the pupil, the bigger the “window” is to look through. Because of this, you may be required to take some dilating drops, these usually take a few minutes to start working and will probably make your eyes more sensitive to light. It is advisable to take along a pair of sunglasses to your exam as this sensitivity can last for several hours after you have left the surgery

Colour vision testing

The usual test for colour blindness involves looking at numbers formed of dots against a background of dots of a different colour. These pictures are called Ishihara plates. People with normal colour vision will see the number as it is meant to be, while people with colour vision problems may see a different number (for example a 3 instead of an 8), or even no number at all. These are the most common tests performed in an eye exam, but there are others and you shouldn’t be alarmed if tests are performed on you that haven’t been mentioned here. It is also important that you’re honest in the answers you give to any questions the optometrist asks; concealing or even just playing down problems may make it more difficult to make a proper diagnosis