SQUINT ( STRABISMUS)
A squint, or strabismus, is a condition in which the eyes do not align properly. One eye turns inwards, upwards, downwards, or outwards, while the other one focuses on one spot.
TYPES:
There are several different types of squint (strabismus). Squints can be classified or described in various ways, including;
- By the direction of the squinting eye (ie the eye not looking perfect in the direction of gaze):
- An eye that turns inwards is called esotropia.
- An eye that turns outwards is called an exotropia.
- An eye that turns upwards is called a hypertropia.
- An eye that turns downwards is called a hypotropia.
- By how constantly the squint is present:
- Squint which is present all the time is called a constant squint.
- Squint that comes and goes is called an intermittent squint.
- By when the squint is seen:
- If it happens when the eyes are open and being used it is called a manifest squint.
- If it happens only when the eye is covered or shut it is called a latent squint.
- By whether the severity of the squint is the same in all directions or not:
- A concomitant squint means that the angle (degree) of the squint is always the same in every direction that you look. That is, the two eyes move well, all the muscles are working but the two eyes are always out of alignment by the same amount, no matter which way you look.
- An incomitant squint means that the angle of squint can vary. For example, when you look to the left, there may be no squint and the eyes are aligned. However, when you look to the right, one eye may not move as far and the eyes are then not aligned.
- CAUSES:
Strabismus can be caused by problems with the eye muscles, the nerves that transmit information to the muscles, or the control center in the brain that directs eye movements. It can also develop due to other general health conditions or eye injuries.
Risk factors for developing strabismus include:
- Family history. People with parents or siblings who have strabismus are more likely to develop it.
- Refractive error. People who have a significant amount of uncorrected farsightedness (hyperopia) may develop strabismus because of the additional eye focusing they must do to keep objects clear.
- Medical conditions. People with conditions such as Down syndrome and cerebral palsy or who have suffered a stroke or head injury are at a higher risk for developing strabismus.
- Accommodative esotropia often occurs because of uncorrected farsightedness (hyperopia). The eye's focusing system is linked to the system that controls where the eyes point. People who are farsighted are focusing extra hard to keep images clear. This may cause the eyes to turn inward. Symptoms of accommodative esotropia may include seeing double, closing or covering one eye when doing close work, and tilting or turning the head.
- Intermittent exotropia may develop when a person cannot coordinate both eyes together. The eyes may point beyond the object being viewed. People with intermittent exotropia may experience headaches, difficulty reading and eye strain. They also may close one eye when viewing at distance or in bright sunlight.
- DIAGNOSIS:
- An optometrist can diagnosis squint through some comprehensive eye examination.
- Patient history: A doctor of optometry will ask the patient or parent about any current symptoms. In addition, the doctor will note any general health problems, medications or environmental factors that may be contributing to the symptoms.
- Visual Acuity: A doctor of optometry will measure visual acuity to assess how much vision is being affected. For the test, you will be asked to read letters on reading charts that are near and at a distance.
- Refraction: A doctor of optometry can conduct refraction to determine the appropriate lens power you need to compensate for any refractive error (nearsightedness, farsightedness or astigmatism). Using an instrument called a phoropter, the doctor places a series of lenses in front of your eyes and measures how they focus light using a handheld lighted instrument called a retinoscope. Or the doctor may use an automated or handheld instrument that evaluates the refractive power of the eye without the patient needing to answer any questions.
- Alignment and focusing testing: Your doctor of optometry needs to assess how well your eyes focus, move and work together. To obtain a clear, single image of what you are viewing, your eyes must effectively change focus, move and work in unison. This testing will look for problems that keep your eyes from focusing effectively or make it difficult to use both eyes together.
- Examination of eye health: Using various testing procedures, your doctor of optometry will observe the internal and external structures of your eyes to rule out any eye disease that may be contributing to strabismus. This testing will determine how the eyes respond under normal seeing conditions. For patients who can't respond verbally or when some of the eyes focusing power may be hidden, your doctor may use eye drops. The eye drops temporarily keep the eyes from changing focus during testing.
cover - uncover test
- TREATMENT:
- Glasses: If hypermetropia, or long-sightedness, is causing the squint, glasses can usually correct it.
- Eye patch: Worn over the good eye, a patch can get the other eye, the one with the squint, to work better.
- Botulinum toxin injection, or botox: this is injected into a muscle on the surface of the eye. The doctor may recommend this treatment if no underlying cause can be identified and if signs and symptoms appear suddenly. The botox temporarily weakens the injected muscle, and this can help the eyes to align properly.
- Eye drops and eye exercises may help.
- Vision therapy: Your doctor of optometry might prescribe a structured program of visual activities to improve eye coordination and eye focusing. Vision therapy trains the eyes and brain to work together more effectively. These eye exercises can help problems with eye movement, eye focusing and eye teaming and reinforce the eye-brain connection. Treatment can occur in your doctor of optometry's office as well as at home.
- Prism lenses: These special lenses are thicker on one side than the other. The prisms alter the light entering the eye and reduce how much turning the eye must do to view objects. Sometimes the prisms can eliminate the eye turning.
- Surgery: Surgery is only used if other treatments are not effective. It can realign the eyes and restore binocular vision. The surgeon moves the muscle that connects to the eye to a new position. Sometimes both eyes need to be operated on to get the right balance.
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