Types of eye testing

Visual field

In this type of eye test you have to stare at a light in the center of your field of vision while lights will be shone in the periphery of your vision. It is called the perimetry test. This test measures your peripheral vision and can be used to detect the onset of open-angle glaucoma.

Cover test

Here your eyes will be alternately covered while you focus on a distant object. By looking at the movement of the eye to focus on the object, the optometrist can identify strabismus (eye turn), which can lead to amblyopia (lazy eye), poor depth perception and other conditions.

Slit lamp test

The slit lamp examination is carried out with a biomicroscope, which allows the optometrist to get a close look at the internal structures of the eye such as the eyelids, cornea, iris, conjunctiva, retina, optic nerve and macula. Also cataracts, macular degeneration, diabetic eye disease and corneal ulcers can all be detected using this test.


This test measures your eye pressure, which is also called intraocular pressure, and is used to test for glaucoma. It often involves a painless test where a puff of air is directed at your eye. The machine will calculate your intraocular pressure on the basis of your eye's resistance to the air. The other test for glaucoma requires your eye needs to be numbed with eye drops. After the drops take effect, you'll have to stare into the slit lamp while the optometrist touches you on the front of each eye with a bright blue glowing instrument. This is also painless.


The optometrist looks into your eye through the pupil. The optometrist can see better if the pupils are dilated. To dilate the pupils you need to put in dilating drops. The dilation takes about 20-30 minutes, which will also make your eyes more sensitive to light. It is advisable to take a pair of sunglasses to your test, as this sensitivity can last for several hours.

Colour vision testing

The colour vision test entails 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 the way it is, whereas people with colour vision problems may see a different number (for example a 6 instead of a 5), or even no number at all. These are the usual tests performed in an eye exam, but there are others tests too. It is also essential to answer the optometrist's questions clearly and honestly for a correct diagnosis.