Don’t remember the lessons on eye anatomy from your highschool biology class? That’s OK—we have provided the following eyeball illustration and terms just to give you a refresher course. And we won’t give you a pop quiz afterwards…
| IRIS: |
Pigmented tissue lying behind cornea that (1) gives color to the eye, and (2) controls amount of light entering the eye by varying size of black pupillary opening; separates the anterior chamber from the posterior chamber. |
| CORNEA: |
Transparent front segment of the eye that covers iris, pupil, and anterior chamber, and provides most of an eye's optical power. |
| PUPIL: |
Variable-sized, circular opening in center of iris; it appears as a black circle and it regulates the amount of light that enters the eye. |
| LENS: |
Natural lens of eye; transparent intraocular tissue that helps bring rays of light to focus on the retina. |
| SCLERA: |
The white of the eye; a protective fibrous outer layer covers all of the eyeball except for the part covered by the cornea. |
| CILIARY BODY: |
A muscular ring under the surface of the eyeball; helps the eye focus by changing the len’s shape and also produces aqueous humor. |
| CHOROID: |
The vascular layer between the sclera and the retina; the blood vessels in the choroid help provide oxygen and nutrients to the eye. |
| OPTIC NERVE: |
Largest sensory nerve of the eye; carries impulses for sight from
retina to brain. |
| MACULA: |
Small, specialized central area of the retina responsible for acute
central vision. |
| RETINA: |
Part of the eye that converts images into electrical impulses sent along the optic nerve for transmission back to the brain. Consists of many named layers that include rods and cones. |
| VITREOUS: |
Transparent, colorless, gelatinous mass; fills rear two-thirds
of the interior of the eyeball, between the lens and the retina. |
Amblyopia
Amblyopia, commonly called lazy eye, occurs when the eyes do not develop properly. This results in seeing poorly out of one or both eyes. Amblyopia is the most common cause of visual impairment in both children and young adults, affecting about 3% of the population.
Symptoms of amblyopia
It is hard to spot amblyopia. Parents often do not realize than anything is wrong with their child’s eyes until they are told about it by their doctor. Sometimes a child will noticeably favor one eye over the other or bump into things on one side. The best way to tell if your child has amblyopia is through a comprehensive eye exam at ages six months, three years, five years, and then annually. Early diagnosis can prevent amblyopia from leading to more serious problems, such as loss of the ability to see three dimensions or functional blindness in the amblyopic eye.
Types of amblyopia
In general, amblyopia is caused by a lack of seeing well while the eyes are developing during infancy and early childhood. There are several types of amblyopia; each of them is a different way that one or both eyes do not see clearly during the developmental period. This blur is so significant that the brain does not learn to see correctly.
- Refractive Amblyopia is caused when a baby or young child has high or unequal amounts of far-sightedness, near-sightedness, or astigmatism and they do not get glasses or contact lenses to treat it when they are young. The extreme blur does not allow the connections between the eye and brain to properly develop.
- Strabismic Amblyopia is caused when a baby or young child has one eye that is constantly turned in, out, up or down. The turned eye is “shut off” or not used, and therefore does not develop vision properly.
- Deprivation Amblyopia is caused when a baby or young child has a condition that is blocking vision out of one or both eyes, such as a cataract or droopy eye lid, and the lack of visual stimulation stops the development of the visual centers in the brain.
How to treat amblyopia?
The best way to decrease amblyopia in the population is prevention. The American Optometric Association recommends comprehensive eye evaluations, in addition to pediatrician well-visits, at ages 6 months, 3 years, 5 years, and every year while the child is in school. Because of the importance of early detection for vision and ocular health conditions, many optometrists are providers for the InfantSEE™ program, which provides a complimentary comprehensive vision and ocular health evaluation for children less than 12 months of age.
Amblyopia will not go away on its own. Although treating amblyopia during the “critical period” before seven years of age gives the chances of the best possible vision, treatment of some types of amblyopia can take place at any age. However, the length of the treatment period increases dramatically the older the patient is. Research has also demonstrated that patients with amblyopia are more likely to sustain injuries resulting in the loss of their good eye than individuals with two good eyes.
Management is dependent on the type of amblyopia that is present. If the child has refractive amblyopia, treatment starts with glasses or contact lenses in the correct prescription. Deprivation amblyopia must be treated during the first few months of life and starts with removing the occlusion (taking out the cataract, surgically raising the lid). Treatment of all types often includes patching the eye with better vision or putting dilating drops in the better eye. Treatment can take weeks or months. This corrects amblyopia by training the brain to use visual signals from the eye with weaker vision, building a stronger connection between the brain and the weak eye, and allowing vision to develop normally in that eye. Patching is most effective in conjunction with an active vision therapy program.
Recommended Link
National Eye Institute Amblyopia Resource Guide
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