What is squint ? Symptoms ,Type , Causes

Introduction

Squint is misalignment of the eyes such that the right and left eyes are pointed in different directions. Though it is a common condition among younger populations, affecting 2 to 4 percent of children, it may also appear later in life.The misalignment may be permanent or it may be temporary, occurring occasionally. The deviation may be in any direction: inward, outward, upward or downward. If the child is not treated at the appropriate time, a condition called amblyopia occurs, which eventually leads to permanent loss of vision

Types of squint

Esotropias

An esotropia is the medical name for a convergent squint where one eye turns in towards the nose.

Exotropias

An exotropia is the medical name for a divergent squint where the one eye turns outwards.

Hypertropias and Hypotropias

These terms refer to vertical squints where one eye is higher (hypertropia) or lower (hypotropia) than the fellow eye. There are a number of different types of squint in each of these three groups, which have their own individual characteristics and treatments.

Paralytic Squints

There are three nerves which send signals to the six eye muscles, these are the third, fourth and sixth cranial nerves. Damage to these nerves as result of poor blood supply to the nerve, pressure on the nerve or head injuries will cause limited eye movements and a squint.

Restrictive Squints

These are squints due to problems with the muscle or the orbit where the eye is placed which prevent the eye from moving normally or in a particular direction due to a
mechanical restriction. Thyroid disease often causes restrictive squints.

Symptoms:

The symptoms include headache, crossed eyes, deviated eyes, double vision, blurred vision due to lazy eye, abnormal head posture and sometimes associated dancing eyes (nystagmus).

Causes:

The exact cause of a squint is not always known. In most cases, babies develop squintin their first year of life which may be idiopathic (no identifiable cause) or because of a
problem with their vision. If a baby is born with the condition, it is called an infantile squint. Squints that develop later are called acquired squints .

Refractive errors

Acquired squints are sometimes caused by the eye’s inability to focus light that passes through the lens. This is known as a refractive error. These include myopia (shortsightedness), Hyperopia (Long-sightedness) or Astigmatism (cylindrical power).

Other causes

Although most squints are idiopathic or caused by refractive errors, in rare cases they are
the result of:
• Childhood illnesses, for example viral infections such as measles, although it is possible these illnesses simply accelerate a squint that would have developed anyway
• Some genetic conditions, such as Down’s syndrome
• Hydrocephalus, which is caused by find a build-up in the brain
• Lazy eye (amblyopia) - when the brain starts to ignore signals coming from the eye with the squint
• Other eye problems, such as abnormal development of the muscles that move the eye, or a problem with the retina (the layer of light-sensitive nerve cells at the back of the eye)

Risk factors:

Some things may increase the risk of having a squint, which may include:
• Having a family history of squints, lazy eye (amblyopia) or need of glasses
• Having a condition that affects the nervous system, such as cerebral palsy
• Being born early (premature birth) or with a low birth weight SQUINT
• For acquired squints in adults, risk factors include high blood pressure, diabetes and thyroid disease.

Tests and diagnostics:

Sight tests
Different tests can be used to help diagnose a squint and assess the level of vision. These will vary according to your age, but may include:
• Concentrating at a light
• Matching letters and pictures
• Reading a letter chart
• Looking at visual targets at different distances, first with one eye covered and then the other

Retina and optic nerve examination

A retina and optic nerve examination would be done by your doctor to rule out any treatable cause for squint.

Refraction

It is important to check the power of the eye to give appropriate glasses. This test may often be done after putting eye drops or an eye ointment for getting the most accurate result.

Ocular movements test

The doctor will examine your eyes and ask you to move them in different directions to check if they are moving normally and determine the type of squint. Prism test The doctor may use prisms or prism bars to measure the amount of squint.

Synoptophore

This machine is often used to perform a full evaluation of squint. It
is a non invasive test where you would be asked to look into two
tubes of this machine and fix on two targets. Then the doctor will
move the targets to measure your squint.