# Which Tests Are Done in an Eye Examination? Source page: https://www.kudretgozistanbul.com/en/blog/eye-diseases/which-tests-are-done-in-an-eye-examination **Author:** Kudret Eye İstanbul | **Medical Approval:** Op. Dr. Mehmet Ali Özdil | **Date:** 2026-09-17 > **Summary:** An eye examination is far more than finding out a prescription: it checks visual acuity, eye pressure, the front and back of the eye, colour vision, the visual field, eye muscle coordination and corneal thickness, so that conditions such as glaucoma, cataract and retinal disease are noticed before they cause permanent sight loss. Not every test is applied to every patient; the ophthalmologist chooses according to complaints and eye structure. ## Quick Facts - **Duration:** A standard examination generally takes fifteen to thirty minutes, longer with fundus examination, visual field test or detailed investigations - **Frequency:** Children after birth, pre-school and primary school; adults every two years between eighteen and forty; once a year after forty; more often with diabetes, hypertension or a family history of eye disease - **Fundus drops:** Dilate the pupil; blurred near vision and light discomfort for a few hours, so do not drive - **Harm:** Standard tests do not harm the eye; any discomfort is temporary --- ## The Stages of an Eye Examination - **Visual acuity:** the chart of letters or symbols shows whether you see clearly at distance and near; myopia, hyperopia and astigmatism emerge and the glasses or lens prescription is determined. - **Autorefractor:** you look into the device and within a few seconds the refractive errors are measured automatically, helping the doctor write a more accurate prescription. ## Measuring Eye Pressure Glaucoma generally advances without symptoms and damages the optic nerve irreversibly if unnoticed, so measuring eye pressure is vital. Some devices blow a light puff of air at the eye, while the more precise applanation method measures through light contact with the eye after a numbing drop. ## Slit Lamp Examination A special microscope examines the eyelids, cornea, iris and lens in turn. The beginnings of cataract, infections and scratches on the cornea are noticed here. ## Fundus Examination Drops dilate the pupil and the doctor examines the retina, the vascular structure and the head of the optic nerve. Retinal damage in diabetes, macular degeneration and retinal tears are identified this way; the findings guide treatment. Near vision may blur for a while; the effect generally passes within a few hours. ## Colour Blindness Test Carried out for driving licences and medical reports, and particularly important in children and certain occupations. You look at cards made up of coloured dots and make out the numbers or shapes; people with colour blindness cannot distinguish them. ## Visual Field Test Measures vision outside the centre of the eye: you look into a device and press a button as lights appear around the edges. It plays a large part in diagnosing glaucoma, which first affects side vision without the patient realising. ## Test for Squint In children and where squint is suspected, the coordination of the eye muscles is checked by looking in different directions; early noticing of deviation makes treatment easier. ## Corneal Thickness Measurement The structure of the cornea can affect the eye pressure reading. It is also very important for people considering laser eye surgery, because a thin cornea may make them unsuitable. For contact lens wearers or candidates, corneal curvature and tear quantity are examined; a wrongly chosen lens can cause irritation, stinging or infection and, rarely, permanent damage. ## How Often to Have an Eye Examination - Children: after birth, in the pre-school period and during primary school. - Adults: every two years after the age of eighteen; once a year over forty, because the risk of glaucoma and cataract rises. - People with chronic conditions such as diabetes and hypertension: more often. - These are general recommendations; the ophthalmologist determines the most appropriate frequency for each person. ## Why Eye Examinations Matter Early diagnosis preserves quality of life and prevents permanent sight loss. An incorrectly measured refractive error leads to unsuitable glasses or lenses, and serious conditions such as glaucoma, cataract or retinal disease can be missed without detailed examination. See an ophthalmologist without delay if you have blurring, headache or double vision or have not been examined for a long time. --- ## Frequently Asked Questions **Q: How long does an eye examination take?** A: Generally fifteen to thirty minutes; somewhat longer with a fundus examination, visual field test or detailed investigations. **Q: Why are drops used in a fundus examination, and how long do they last?** A: They dilate the pupil so the retina and optic nerve can be assessed clearly. The effect generally lasts a few hours, with blurred vision and discomfort in light, so you are advised not to drive. **Q: Can I wear lenses to an eye examination?** A: Ask the doctor or clinic how long before the examination to remove them; for eye measurements and corneal assessment lenses may need to be left out for a period that depends on the lens type and the examination. **Q: Do eye tests harm the eye?** A: No. Visual acuity, eye pressure, fundus and visual field tests do not harm the eye; brief discomfort, blurred vision or light sensitivity is temporary. **Q: How often should I have an eye examination?** A: Children after birth, pre-school and primary school; every two years between eighteen and forty; once a year after forty; shorter intervals with diabetes, hypertension or a family history of eye disease.