A thorough eye examination consists of a variety of standard tests designed to measure visual acuity and other vision faculties, as well as to observe the health of the eye and check for common eye diseases. There is no pain or discomfort associated with an exam, and it typically takes less than an hour.
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 eyes) and amblyopia (lazy eye) can often be diagnosed and treated in early childhood, avoiding life-long vision impairment. Rare eye conditions from birth (like congenital cataracts) can also be diagnosed and treated. For all ages, refraction tests can determine whether prescription eyewear would be beneficial, and what power is necessary. 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 life. In the first three years, infants should have their vision checked as part of regular pediatric checkups. Between ages 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 exam per year. Exams are also recommended more frequently for patients monitoring a diagnosed eye condition, or with a hereditary predisposition to an eye disease.
Common tests and evaluations during an eye exam include:
- History — The doctor will ask basic questions about the patient’s medical and eye health history.
- External Examination — The doctor inspects all the outwardly visible parts of the eye and surrounding tissue.
- Pupil Inspection — The patient’s pupils will be inspected for equality of size and shape and tested for how they react to light and when focusing at various distances.
- Eye Muscle Health and Mobility — Eye movement is checked in six directions (corresponding to the six extraocular muscles), by tracking a moving object, such as a pen.
- Visual Field — The patient covers one eye and, with the other eye gazing straight ahead, identifies objects in peripheral vision.
- 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. The smallest row that can be accurately read indicates the patient’s visual acuity in that eye.
- Refraction — This test is used to determine if one has a refractive error that needs to be corrected with prescription eyewear or contact lenses. The doctor will place various lenses in front of each eye as the patient focuses on a chart at a distance or up-close, to help determine the appropriate power of correction.
- Color Vision — The patient is presented with a series of images with symbols embedded in colored dots or patterns. Based on the patient’s ability to identify the symbols, certain types of colorblindness can be diagnosed or ruled out.
- Ophthalmoscopy — Often performed with an ophthalmoscope, a handheld instrument with a light and magnifying lenses, or a slit lamp, which affords a more three-dimensional view, this allows for the inspection of the retina. Ophthalmoscopy can help diagnose problems with the retina and monitor diseases such as glaucoma, macular degeneration and diabetes. Sometimes the doctor will dilate the pupils with eyedrops, to gain a wider view of the internal eye.
- Tonometry — This test measures intraocular pressure. Internal eye pressure is measured either with a puff of air at the cornea or by brief direct contact with the cornea, to measure how easily it is pushed inward.
LASIK Eligibility Evaluation
An individual with nearsightedness, farsightedness, or astigmatism that finds glasses or contacts cumbersome or uncomfortable may be a good candidate for LASIK or other vision corrective surgery. Before a recommendation for surgery can be made, however, an eligibility exam and consultation is required. The doctor will ask questions about your medical history and perform a thorough eye exam designed to determine if the procedure is appropriate for your individual case. The doctor will also talk about the benefits, risks, available options, preparation and recovery associated with the surgery to ensure that your goals and expectations are realistic.
