What is a General Eye Exam?
A thorough eye examination consists of a variety of standard tests designed to measure visual acuity and other vision faculties, as well as observe the health of the eye and check for common eye diseases. There is no pain or discomfort associated with an exam, and they typically take less than an hour and a half.
General eye exams can diagnose a variety of eye conditions early on and are the best way to preserve good vision. For children, strabismus (crossed eye) and amblyopia (lazy eye) can often be diagnosed and treated in early childhood, avoiding life-long vision impairment. Also, rare eye conditions from birth (like congenital cataracts) can be diagnosed and treated. For all ages, refraction tests can determine whether prescription eyewear would be beneficial, and what power is necessary. Furthermore, many debilitating eye diseases can be diagnosed before noticeable symptoms occur, potentially making the difference between minor damage and major vision loss.
Eye exams are recommended regularly throughout all phases of one's life. In the first three years, infants should have their vision checked as part of regular pediatric checkups. Between age three and six, an eye exam every year or two is recommended. Throughout childhood and the teenage years, exams should be scheduled as necessary. Adults should have at least one exam in their twenties, at least two in their thirties, and an exam every two to four years after that. Exams are recommended for seniors every one to two years. People with diabetes should have at least one dilated exam per year. Exams are also more frequent for patients monitoring a diagnosed eye condition, such as glaucoma, or with a hereditary predisposition to an eye disease.
Common tests and evaluations during an eye exam include:
- Introductory interview: The doctor will ask basic questions about a patient's medical history and eye health history.
- External examination: The doctor inspects all outward visible parts of the eye and surrounding tissue.
- Pupil inspection: The patient's pupils will be inspected for equal size and regular shape and how they react to light.
- Eye muscle health and mobility: Eye movement is checked in six directions (corresponding to the six extraocular muscles), as well as tracking a moving object (such as a pen).
- Visual field: The patient covers one eye at a time, and with the other eye gazing straight ahead, identifies objects in peripheral vision (often simply the number of fingers shown.)
- Visual acuity: A common means of measuring visual acuity is the Snellen chart. This is a large card or projection with progressively smaller horizontal lines of random block letters. The test determines how well a patient can discern detail at a given distance. Patients taking this test will cover one eye and then read aloud the letters of each row, starting from the top. The smallest row that can be accurately read indicates the patient's visual acuity in that eye.
- Refraction: This test is used to find the best corrected vision, if necessary for prescription eyewear or contacts. Various lenses are placed in front of each eye, as the patient focuses on a chart at a distance or up-close, to help determine the best power of correction. For patients under the age of 18, the patient may need to have their eyes dilated.
- Ophthalmoscopy: This test is often done with a magnifying lensesand a slit lamp, which affords a three-dimensional view of the eye. Ophthalmoscopy aims to inspect the retina and surrounding internal eye. This test can help diagnose problems with the retina or detachment of the retina, and monitor diseases like glaucoma and diabetes. An opacity in the eye can indicate a cataract. To gain a wider view of the internal eye the patient will be dilated.
- Tonometry: This test measures intraocular pressure, which can be a sign of glaucoma if pressure is abnormally high. Internal eye pressure is measured with brief direct contact with the cornea, to measure how easily it is pushed inward.