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Strabismus is the misalignment of the eyes. People with this affliction are commonly referred to as "cross-eyed." Either or both eyes may be turned in, up, down or out. It is most often diagnosed in children. Strabismus can be either a disorder of the brain coordinating the eyes or a disorder of one or more muscles, as in any process that causes a dysfunction of the usual direction and power of the muscle or muscles.
The two types of strabismus are -
1. Exotropia
2. Esotropia
1. Exotropia –
People with exotropia often experience crossed diplopia. Intermittent exotropia is a fairly a common condition. "Sensory exotropia" occurs in the presence of poor vision. Infantile exotropia is know as "congenital exotropia".It is seen during the first year of life, and is less common than "essential exotropia" which frequently becomes apparent a number of years afterward.
2. Esotropia -
Esotropia is sometimes speciously called "lazy eye", which describes the condition of Amblyopia. Amblyopia is a reduction in vision of one or both eyes which is not the result of any pathological lesion of the visual pathway and which cannot be resolved by the use of corrective lenses. It is the opposite of Exotropia.Amblyopia can, yet, arise as a result of esotropia occurring in childhood. In order to relieve symptoms of diplopia or double vision, the child's brain will ignore or "suppress" the image from the esotropic eye, which when allowed continuing untreated will lead to the development of amblyopia. Treatment options for esotropia include glasses to correct refractive errors (see accommodative esotropia below), the use of prisms and/or orthoptic exercises and/or eye muscle surgery.
The four types of Esotropia are -
1. Congenital Esotropia.
2. Infantile Esotropia.
3. Accommodative Esotropia.
4. Partially Accommodative Esotropia.
1. Congenital Esotropia - Congenital" means from birth and, using this strict definition, most infants are born with eyes that are not aligned at birth. Only 23% of infants are born with straight eyes. In the common of cases, one eye or the other in fact turns outward during the neonatal period. Within the first three months the eyes slowly come into more consistent alignment as coordination of the two eyes together as a team develops.
2. Infantile Esotropia - The baby with infantile esotropia typically cross fixates, which means that he or she uses either eye to look in the opposite direction. The right eye is used to look toward the left side, and the left eye is used to look toward the right side. By definition, they alternate which eye they are looking with. It is more difficult to help this type of strabismus with non-surgical methods, such as vision therapy and/or glasses.
3. Accommodative Esotropia -
If excessive inward turning of an eye is first noted around 2 years of age, it may be due to difficulty in integrating the focusing (accommodative) system with the eye alignment (binocular) system. Normally when we look across the room or beyond, our eyes are parallel, or straight. However, when we look at things up close, two things happen. We need to converge more (aim both eyes inward at the same time) and we have to input more focus, or accommodate to keep things clear. Children have large amounts of focusing power, and sometimes in getting things clear, inward turning or esotropia results. If the inward turning only occurs up close, as when playing with small objects, making eye contact, coloring, looking at picture books and so forth, the child may just need glasses for near activities to reduce or eliminate the esotropia.
4. Partially Accommodative Esotropia -In some instances, part of the inward turn is due to basic esotropia, and an additional amount due to the effect of accommodation. Glasses may reduce the amount of eye turn, but it is not totally compensated. Initially, the eye doctor may prescribe prism to compensate for the amount of turn. Office-based vision therapy is usually needed. Surgery remains an option to address the non-accommodative portion of the esotropia
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