A person who has eye symptoms should be checked by a doctor. However, some eye disorders cause few or no symptoms in their early stages, so the eyes should be checked regularly (every 1 to 2 years or more frequently if there is an eye condition) by an ophthalmologist or an optometrist. An ophthalmologist is a medical doctor who specializes in the evaluation and treatment (surgical and nonsurgical) of eye disorders. An optometrist is a health care practitioner who specializes in the diagnosis and treatment of vision or refractive problems (refractive errors).

Diagnosis of eye disorders is initially based on the person's symptoms, the appearance of the eyes, and the results of an examination.

A person with eye or vision problems describes the location and duration of the symptoms, and then the ophthalmologist examines the eye, the area around it, and possibly other parts of the body, depending on the suspected cause. An eye examination usually includes refraction, visual field testing, ophthalmoscopy (also called funduscopy), a slit-lamp examination, and tonometry. By having the person look in all directions, the examiner can determine how the cranial nerves supplying the muscles that move the eyes (called extraocular muscles) are functioning.

efraction is the procedure examiners use to assess focusing errors. Problems with visual acuity (sharpness of vision) that result from refractive errors, such as nearsightedness, farsightedness, astigmatism, and presbyopia, are diagnosed by refraction. Acuity is usually measured on a scale that compares a person's vision at 20 feet (about 6 meters) with that of someone who has perfect vision. Thus, a person who has 20/20 vision sees objects that are 20 feet away with the same clarity as a person with normal vision, but a person who has 20/200 vision sees at 20 feet only as clearly as a person with perfect vision sees at 200 feet (about 61 meters).

One important visual acuity test uses the Snellen chart (eye chart), which is a large card or lighted box that displays rows of letters in smaller and smaller sizes. The chart is read from a standard distance. The degree of visual acuity is determined by the size of the row of letters that the person can read. For people who are unable to read, a modified chart can be used in which the letters are represented by an upper case "E," which is rotated randomly. People are asked to describe which way the "E" is facing. If a person cannot read anything from a chart, the examiner may see whether the person can count the examiner's fingers or see whether the examiner's hand moves. Examiners also test near vision by asking the person to read a standard near card or newsprint at a distance of about 14 inches (35 centimeters).

Automated refraction is done with a device that determines the refractive error of the eye by measuring how light is changed when it enters the eye. The person sits in front of the autorefractor, a beam of light is emitted from the device, and the eye's response is measured. The machine uses this information to calculate the lens prescription needed to correct the person's refractive error. This measurement takes only a few seconds.

Thanks and Regards
Sarah Rose,
Associate Managing Editor
Journal of Eye Diseases and Disorders
ISSN: 2684-1622