PAEDIATRIC OPTHAL & ADULT SQUINT
This deals with eye care for children between birth and 16 years. It includes Squint, Nystagnus (rapid eye movements), Amblyopia (Lazy Eyes), Retinopathy of prematurity (ROP) – Retinal disorders in premature children and various hereditary disorders as well as Congenital Cataract, Glaucoma + Malformations.
What is Squint (Strabismus)?
Squint is a misalignment of the two eyes so that both the eyes are not looking in the same direction. This misalignment may be constant, being present throughout the day, or it may appear sometimes and the rest of the time the eyes may be straight. It was then called intermittent.
It is a common condition among children. It may also occur in adults.
What causes Squint?
The movement of each eye is controlled by six muscles. Each of these muscle acts along with its counterpart in the other eye to keep both the eyes aligned properly. A loss of coordination between the muscles of the two eyes leads to misalignment. This misalignment may be the same in all directions of gaze, or in some conditions the misalignment may be more in one direction of gaze, e.g. in Squint due to nerve palsy.
Sometimes a refractive error hyper metropia (long sight) may lead to inward deviation of the eye. Poor vision in an eye because of some other eye disease like prolonged cataract, etc. may also cause the eye to deviate. Therefore it is important in all the cases of Squint, especially in children, to have a thorough eye check up to rule out any other cause of loss of vision.
What is Binocular Vision?
Under normal circumstances, when both the eyes have good vision and they are aligned properly, they focus on the same object. Each of the eyes sends picture of the same object, viewed from a slightly different angle. These two images reach the brain, where they are fused to form a single three-dimensional picture with depth perception. This is known as binocular single vision.
What are the problems with Squint?
When the eyes are not aligned properly, each of the eyes is focusing on a different object and sends signal to the brain. These two different images reaching the brain lead to confusion and may have either of the two effects:
A child would ignore the image coming from the deviated eye, and thus sees only one image. But in the process, he loses the depth perception. This suppression of the image from the deviating eye results in poor development of vision in this eye, which is known as Ambylopia or Lazy Eye. Squint in children should never be ignored or it may lead to permanent damage to the visual apparatus.
Since an adult cannot ignore the image from either eye, and therefore has double vision. This can be very annoying and may interfere with work.
Treatment:
Surgical correction,Prisms,Eye Exercises,Medical therapy and paediatric eye screening.
Symptoms of Squint?
In a child, the parents may notice the deviation of eyes. It is important to remember that the eyes of a newborn are rarely aligned at birth. Most establish alignment at 3-4 weeks of age. Therefore Squint in any child who is more than one month old must be taken seriously and should be evaluated by an ophthalmologist.
Adults may notice double vision, or misalignment of the eyes
How is Squint Diagnosed?
The Squint is diagnosed by the ophthalmologist. He or she would do a few special tests to confirm the Squint, to try and find out the cause and to quantify the amount of deviation. In some cases there may be a false appearance of Squint due to broad nasal bridge in a child. An ophthalmologist will be able to differentiate between a true Squint and false Squint.
When should the Squint be treated?
In a child, the treatment of Squint and any associated amblyopia should be started as soon as possible. Generally speaking, the younger the age at which amblyopia is treated; the better is the chance of recovery of vision. Remember that the child would never grow out of Squint. A delay in treatment may decrease the chances of getting a good alignment and the vision.
LAZY EYE
Amblyopia is an early childhood condition where the childs vision does not develop properly. It usually occurs in one eye, but it can occur in both eyes. Sometimes referred to as lazy eye, amblyopia affects about 1 in 25 children. A baby is able to see as soon as it is born, and vision continues to develop up until around the age of seven or eight. After this, no further development occurs until sight deteriorates with age, or after eye injury or disease.
Light rays travel through the lens at the front of the eye, and form images on the retina, which is a light sensitive surface at the back of the eye. The retina sends messages to the brain so that it recognises the objects we are seeing. During early childhood, it is important that clear images are formed in the eye and are sent to the brain, so that the childs vision develops normally. If there is a problem with this development, it may result in impaired vision (amblyopia).
The better working eye is patched to stimulate the weaker eye to work
Symptoms
If your child has amblyopia she/he does not receive and send clear images. This means that your child is unable to focus properly with one of their eyes. However, the other eye will often make up for the problems in the affected eye, resulting in the affected eye becoming lazy.
Also, a child may not notice that there is a problem. Therefore, a lazy eye is often not diagnosed until the child has their first eye test. As the affected eye is not able to send clear, sharp images to the brain, the main symptom of a lazy eye is blurred or double vision. Although, there are usually no physical symptoms of a lazy eye, some children may have a noticeable squint, a droopy eyelid or a cataract (clouding of the lens of the eye).
There are a number of different eye disorders that can cause amblyopia including:
Strabismic Amblyopia
Strabismic amblyopia is the most common cause of lazy eye. The condition involves a squint (strabismus) in one eye, which is noticeable because the eyes look in different directions. For example, one eye may look straight ahead and the other may look inwards, outwards, up, or down. To avoid double vision, the brain ignores the signals from the eye with a squint, and only sees images from the normal eye. As the affected eye is not being used, over time the squinting eye will become lazy.
Anisometropic Amblyopia
Anisometropic amblyopia is where a refractive error (spectacle power poor focussing of light occurs due to short-sightedness (myopia), long-sightedness (hypermetropia), or astigmatism (where the surface of the lens is uneven, causing blurred vision) and there is a difference of refraction in each eye. Usually, both eyes are affected to the same degree. However, in anisometropic amblyopia, a child who has hypermetropia, for example, will be more long-sighted in one eye compared with the other. As a result, their brain will ignore the signals from the eye that has the biggest refractive error (is most long-sighted) and, as a result, amblyopia may develop in this eye.
Ametropic Amblyopia
Ametropic amblyopia is a reduction in the vision of both eyes. It usually occurs when a child has large, uncorrected refractive errors(spectacle power0. The image that is produced on the retina, at the back of the eye, is constantly blurred as a result of undetected long-sightedness or astigmatism.
Stimulus Deprivation Amblyopia
Stimulus deprivation amblyopia is the rarest form of amblyopia, but it is often the most severe. It is caused when one or both eyes are prevented from seeing and become lazy due to:
- An eye disease such as a corneal ulcer or scar,
- A congenital cataract (clouding of the lens of the eye present from birth),
- A droopy eye lid (ptosis or blepharoptosis),
- Glaucoma
Stimulus deprivation amblyopia can also be caused by an injury, or surgery, to the eye.
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