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Squint Correction

A squint, also known as strabismus, is when the two eyes are not aligned in a way that they are not looking in the same direction. Generally, a squint test is conducted to determine the actual cause and course of the treatment.

With strabismus, one eye may not focus on the object being viewed. On the other hand, the second eye may turn inward, outward, upward or downward when the patient is gazing straight ahead. It is imperative to keep in mind that squinting is frequently diagnosed in children, but it can also occur in adults.

The majority of children who squints may be brought on by poor vision. Adult squints typically result from secondary factors including trauma, brain lesions, prolonged computer use, etc., and require a different approach to treatment than those in kids. Children who squint typically learn to block out the image from the offending eye; however, adults often experience diplopia or double vision.

Symptoms of Squint Eyes

The most typical strabismus symptoms include:

  • Eyes that continuously focus in multiple directions
  • Eyes that are fixed on one another
  • Shutting one eye or squinting in direct sunlight
  • deviation of eye
  • A poor sense of depth
  • In addition, there are a number of risk factors associated with them
  • People who have a parent or sibling who has squint eyes or who have a family history of the condition are more prone to develop it.
  • People who are significantly farsighted or hyperopic are more likely to squint their eyes.
  • Squint eyes are more likely to develop in people with a stroke, Down syndrome, or cerebral palsy, among other medical disorders.

Different Types of Squint Tests

To ensure the accuracy of your condition, make sure you carry out or undergo a squint test to assess the severity of the situation. There are multiple squint eye tests that are available in the medical sector:

  1. Single Cover Test
  2. Prism Cover Test
  3. Alternate Prism cover Test
  4. Cover-uncover Test
  5. Alternate cover Test
  6. Hirschberg Test

1. Single Cover Test:

The cover test for squint is used to identify the presence of heterotropia or tropia, which is always present, evident strabismus or misalignment. For around 1-2 seconds, the first eye is hidden. The uncovered eye is watched for any focus shift while this eye is covered. Any refixation movements are then documented after removing the occluder. If there is no change in fixation, one of two things may be the case:

  • If the patient sees the same item when the other eye is covered, it is likely that they are orthotropic or have no alignment issues.
  • In the case of heterotropia, the uncovered eye is the fixating or favored eye.

After waiting a few seconds from the previous eye so as not to suspend fusion and allow a phoria to emerge, the opposite eye is then covered in a similar manner for about 1-2 seconds. Next, the unobstructed eye’s fixation is then observed for any changes.

2. Prism Cover Test

If a tropia is present, a simultaneous prism cover test can be used to assess the angle of deviation. The non-fixating eye is covered with a prism of changing strength that is oriented in the direction that corresponds to the deviation. Next, the fixating eye is covered with an occluder until there is no shift in fixation or the deviation is neutralized.

Exotropia, as in this instance, occurs when the unoccluded eye slips inward in a temporal to nasal direction while the opposite eye is occluded. Esotropia is seen when the unoccluded eye slips laterally or outward in a nasal to temporal direction when the other eye is covered. When the opposite eye is occluded, if the unobstructed eye slides downward- this indicates that a hypotropia exists.

Only modest angle tropias are normally measured with this test to prevent patient dissociation and reveal an underlying phoria. When performing the prism test for squint eyes, it’s crucial that each eye’s occlusion be brief in order to prevent suspending binocular fusion and dissociating the patient since doing so could cause the deviation to appear greater by superimposing a phoria on top.

3. Alternate Prism cover Test:

The alternate cover test carried out with the prism positioned as above is an alternate prism cover test. This is used to calculate a phoria’s angle of deviation. When compared to not using a prism, the prism should reduce the refixation movement’s magnitude. The magnitude of the phoria is equal to the strength of the prism at this moment because there is no longer any refixation movement being seen. The strength of the prism can be increased so that the direction of the refixation movement is reversed and then dropped to the prior strength of the prism where there is no refixation movement once more to confirm the outcome of the alternate prism cover test.

4. Cover-Uncover Test

A cover uncover test is the next test. This test is used to identify the presence of heterophoria or phoria, latent strabismus or misalignment that only manifests when binocular fusion is interrupted or suspended. The single cover test is used for this test, however, as the occluder is removed away, the focus is switched to the eye that has been covered. A phoria is present when the covered eye exhibits a refixation movement when the occluder is removed, but the uncovered eye does not exhibit a fixation shift while the occluder is applied.

5. Alternate Cover Test

The alternate cover test is the next test. By suspending binocular fusion, this squint eye test will bring out any tropia that may be present in addition to the tropia identified on single cover testing, allowing the whole deviation to be measured. Since it is the most dissociative cover test, it is conducted after single cover testing.

In order to perform this test, one eye must be covered and the occluder held in place for several seconds to suspend fusion. Then, the occluder must be moved to the other eye, and the patient must quickly alternate between the two without allowing the patient to go binocular and while being careful to always keep one eye covered. To assess the direction of deviation, the eye beneath the occluder is watched when it is taken off and placed over the other eye.

6. Hirschberg Test

The Hirschberg test for squint uses light sources such as penlight or finoff transilluminator and is one of the simplest and easiest to perform.
Distancing the light source from two feet away from patient’s eyes, shining it in the middle will equally cover corneas in both eyes. The relative difference in position of reflex will determine the alignment. For instance, in case of esotropia, displacement will be outwards from the center of cornea and inwards in case of hypertropia. Thus, reflection will appear at the same position if alignment is normal.

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