From birth on, the eye examination is the best and only accurate means of detecting disorders so that proper treatment can be received. Regular screening for problems that might require urgent attention has been statistically proven to reduce the incidence of vision loss.

The eye exam is a relatively pleasant experience for most people. The eye doctor and the patient will discuss the patient's health, eyes and vision. Following this case history, there are three primary types of clinical eye tests performed in a regular exam: An external eye health evaluation, a refraction (or acuity) test, and a retinal examination. A thorough eye health and visual analysis should take approximately 30 minutes.

External Eye Evaluation
During the external exam, the doctor uses a penlight to check the dilating and constricting function of the pupil. He or she holds up fingers and moves them across the patient's field of vision to evaluate eye movement and test peripheral vision. The eyelids, conjunctiva, cornea, iris, lens and vitreous are visually inspected. The doctor will look for signs of and perform tests for eye conditions such as glaucoma. The quantity and quality of tears may also be examined.

Refraction

Light rays bend as they pass through water, glass, crystal, plastic or other transparent material. This is called refraction. Light rays from various distances bend to a different angle as they pass through the lens of the eye. The lens accommodates by adjusting in thickness to place the light rays on the retina.

Then, using special charts with letters and numbers, the doctor is able to detect whether images are in focus. For preschoolers who cannot read, the eye exam is performed using illustrations instead of letters and numbers.

The characters are scaled in size as if they were 3/8 inch high when viewed from 20 feet. "Normal" vision can distinguish letters this size at this distance. This is referred to as 20/20 vision.

To determine the factors causing any focusing errors, the eye doctor positions a large instrument in front of your eyes. You read the eye chart while the eye doctor rotates lenses in front of your eyes, and you provide feedback regarding your vision. Once your optimum vision is reached, the eye doctor records the strength of the lenses that provided this clarity.

You should feel free to ask your eye doctor what each test measures, what your results are, and about the latest equipment and technology.

A nearsighted eye is too long, causing light to converge in front of the retina and blurring distant vision.

Retinal Exam
During a retinal exam, or ophthalmoscopy, the eye doctor views the back of your eye through an instrument called an ophthalmoscope. The retina should be examined regularly so that problems can be discovered before they damage vision. There are other tests that would be performed if the ophthalmoscopy indicates potential problems.

The retina is best examined through a dilated pupil, allowing the eye doctor a wider view inside the eye. Eye drops are used to dilate the pupil. The drops cause temporary blurriness and sensitivity to light but these side effects subside relatively quickly.

Prior to your exam, you should share your vital health information with your eye doctor, and parents should do so for their children. If you change eye doctors, try to provide your new doctor with your prior records. Be sure to discuss:

• medications you are taking
• allergies
• health conditions such as diabetes
• recent illness

Routine exams are varied somewhat based on age and eye condition.

Birth
At birth, a baby's first medical examination includes a check for congenital eye defects. Although rare, early diagnosis of these problems is important to preserve sight. Pediatricians and eye doctors can usually correct most eye problems, if spotted early.

Some babies are born with strabismus, in which one or both eyes are not straight. It can be caused by either extreme farsightedness or eye muscle imbalance. The condition usually goes away within a few months without treatment. Premature babies have a greater chance of developing this condition.

Strabismus can develop from birth to about age 7. It may be rarely noticed at first but become frequent over time.

Infancy
At 3 to 4 months, parents should consult an eye doctor if a baby:

• cannot focus on or follow an object with both eyes
• has difficulty moving one or both eyes in all directions
• has crossed eyes most of the time
• has one or both eyes that tend to wander outward

Otherwise, infants should have an eye exam at the age of 6 months. During a thorough examination, the eye doctor will test both of the baby's eyes for large differences in visual status to rule out "lazy eye," or amblyopia. He or she will check the baby's eye movements and eye health. Problems with vision development and eye health are uncommon in infants but most easily treated if caught early.

Childhood and Adolescence
Normally, parents should schedule an eye examination when their child is 3 years old, then again just before school begins. Once of school age, regular exams are recommended once a year even if no problems have been detected previously. Visual changes take place gradually and may go unnoticed by a child, parents, and caretakers.

Visual screenings done in school are valuable for spotting conditions that could affect how a child is functioning. These are preliminary assessments, designed to detect vision defects such as nearsightedness and farsightedness, and give a rough degree of refraction error. The visual screenings are no substitute for a more thorough evaluation by an eye doctor. It is estimated that 25 percent of school-age children with correctable vision problems do not receive treatment.

• Eye Conditions - Most preschool and young school-aged children are slightly farsighted. The condition lessens as children grow, usually stabilizing by adolescence. Nearsightedness, however, may begin in childhood but continue to progress through adolescence and into early adulthood. Parents' first clues that their child is nearsighted often occur at school. When a child has difficulty seeing the blackboard, learning or behavioral problems often surface in class. Because of vision difficulties, the child may avoid sports. Other clues are:

• sitting too close to the television
• eye rubbing
• squinting
• clumsiness
• holding head at an odd angle
• headaches or dizziness

• Injury and Infection - The most common need for eyecare in childhood is caused by infection and injury. Pink eye (conjunctivitis), corneal scratches and sports injuries are the most common causes.

• an eye that wanders inward or outward when tired
• eyelid droopiness
• redness of eyes or eyelids
• crusted eyelids
• tearing or leaky eyes
• eyelid styes or sores
• too much eye rubbing
• avoidance of bright light

Adulthood
The human eye reaches peak strength in the young adult, around the mid- to late-20s. Night vision, eye-hand coordination, motion and depth perception, and color discrimination may all improve during this time. During the years of improved sight, nutrition can contribute to optimum vision.

Aging Eyes
By the time we reach our mid- to late-30s, most people begin to have difficulty focusing on close objects. The ciliary muscles that adjust the thickness of the lens start to weaken. Meanwhile, the lens itself loses its elasticity. Consequently, the ability of the lens to focus at close range decreases. The condition is referred to as "aging eyes" or presbyopia.

Most people notice signs of aging eyes, between the ages of 40 and 45 when they begin holding reading material at arms' length. The majority need to wear reading glasses or other corrective lenses. The condition may progress indefinitely or stabilize by 65 to 70 years of age. To detect this condition, an annual eye exam is recommended.

Sensitivity to Light
During our mid-40s, the iris muscles tend to slow. The reflex response decreases, increasing the amount of light entering the eye. For many people, sensitivity to glare starts at this age. Their eyes may be overexposed to the sun and other UV light, potentially causing permanent damage. Eyewear with ultraviolet radiation protection can shield the eyes from the harmful rays.

Pregnancy
Vision often changes during pregnancy but usually returns to normal after delivery. Here are some eye-related changes that may occur during pregnancy:

• a change in refraction, requiring a different prescription for corrective eyewear
• blurry vision
• dry eye
• less tolerance of contact lenses
• worsening of existing eye conditions

Vision problems during pregnancy may signal other health problems. Blurred vision or seeing spots may indicate gestational diabetes or pregnancy-induced hypertension, an increase in blood pressure that usually occurs after the 20th week of pregnancy. Eclampsia and pre-eclampsia, caused by extremely high blood pressure, can cause eye hemorrhages and retinal detachment, although these are extremely rare.

Not all pregnant women develop eye problems, but experts recommend routine examinations by an eye doctor each trimester. Early treatment is vital to the health of the mother and baby.

Maturity
Healthy eyes and good vision help older people lead active, independent lifestyles. Many eye problems are treatable, especially if spotted early. An annual visit to the eye doctor is one of the best ways to maintain healthy eyesight. This is especially important if you have diabetes or eye disease.

Some vision changes are a normal part of aging. Others may be indicative of other diseases such as high blood pressure or diabetes, both common in older adults. Common occurrences during the elder years include:

• stabilization of presbyopia, or "long arm syndrome"
• development of cataracts
• increase in spots, floaters and flashes
• onset of glaucoma
• incidence of dry eye
• disease, infection or injury of the cornea
• retinal disorders such as macular degeneration, diabetic retinopathy and retinal detachment

Retinal disorders are a leading cause of vision loss in elderly people. When damaged, the light-sensitive cells lining the retina cannot pass images to the brain. If detected and treated early, vision loss may be slowed or halted.

Retinal Detachment
During the aging process, the retina may become detached from the back of the eye. If caught in time, laser surgery may be able to bond it to the back of the eye. You should consult an eye doctor if you experience:

• blurry central vision
• clouded vision
• inability to see faces or details clearly
• double vision
• visual distortion
• sudden vision loss
• sudden onset of flashing lights

Corneal Disease
Older adults are particularly vulnerable to corneal disease, largely due to the high incidence of dry eye. Symptoms include:

• redness
• reflex tearing or watery eyes
• eye pain
• loss of vision
• seeing halos

Accommodation
In addition to corrective eyewear and regular eyecare exams, you can make minor changes in your home or in your behavior to adapt to the limitations of your changing vision. There are several ways that you can enhance the safety and convenience of your surroundings:

• Make sure lighting is adequate, day and night, in key areas:

• outdoors
• garage
• storage areas
• stairways
• work spaces
• favorite reading places

• Keep flashlights in your car and in a carryall bag for unexpected situations.
• If your vision is best in the morning, schedule your reading and detailed work accordingly.
• If your ability to see in the dark is diminished or you have increased sensitivity to glare:

• Use caution when walking near traffic.
• Drive only on well-lit roads.
• Keep your windshield, headlights and glasses clean.
• Wear anti-glare glasses.
• Consider avoiding driving at night

Sources
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D'Alonzo, T.L. Your Eyes: A comprehensive Look at the Understanding and Treatment of Vision Problems. Clifton Heights, PA: Avanti Publishing, 1991.
Eden, J. The Physician's Guide to Cataracts, Glaucoma, and Other Eye Problems. New York, NY: Consumer Reports Books, A Division of Consumers Union Yonkers, 1992.
Schuman, B.N. The Human Eye. New York, NY: Atheneum, 1986.
Leach, Penelope. Your Baby and Child. Alfred A. Knopf. New York, NY: 1990
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