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CONGENITAL ESOTROPIA (CET)(August 04)

CET is the commonest type of strabismus (eye misalignment) seen in babies. The eyes point to the nose (esotropia), and the angle of misalignment is usually quite severe. Other names used for this condition are: infantile esotropia or essential infantile esotropia

Causes of CET


CET probably develops as a result of poor maturation of some visual wiring in the brain at 6-12 weeks of age. This has two effects:

1. It results in tightening of the inside muscles (hence esotropia) and
2. It results in a very subtle eye wobble (nystagmus) which prevents perfect development of the visual system.

The tight muscles causing the misalignment is the easy part of the problem and is fixable with surgery. Straightening the eyes in CET is a bit like erecting an excellent looking house knowing that the foundations are poor. No matter how good the house looks on day one there is unfortunately a chance that it won't stay looking good.

Common Associations


Most children with CET are otherwise healthy but CET is more frequent in children with other physical problems.

1. Reduced vision in one eye (amblyopia or lazy eye) > 35%

This is seen in approx 1 in 3 patients. This requires treatment with patching BEFORE surgery is planned. Treatment may begin or need to continue after surgery.

2. Vertical misalignment.

This can be due to a number of different mechanisms. Some cases look weird and need surgery for the child to look normal. Some children have surgery for the vertical imbalance at the same time as they have the surgery for the horizontal misalignment.

3. Abnormal Head Position
The nystagmus may cause a face turn [so the child always looks at you with face turned to the right or to the left but not straight on] or a head tilt.

Goals of Treatment


The aim is to get the child's eyes straight with as few surgeries as possible. Dr. Kowal's personal results are:

1. 75% perfect at 12 months. These patients typically require low level follow-up and have a high expectation of long term stability.
2. 5% near perfect at 12 months.
3. 10% very good-excellent at 12 months. These two groups (2 & 3) of patients are typically considered "successes". They require closer monitoring than group 1.
4. 10% require repeat surgery within 12 months.
5. Children who have a surgery before the age of 2 have a 15% expectation of needing a second surgery in the next 2 years.

Over the first five years, about 25% of children end up developing a convergent strabismus again. About half of the time this is fixable with glasses. About 10% develop a divergent strabismus; most of these end up needing a second operation for that.

Age At Which Best Result Is Achieved


When we treat large numbers of children statistically better results are achieved with early or very early surgery:
· Research by Dr Birch in the US: better results if eyes are successfully aligned within four months of going crosseyed (better depth perception and 50% lower re-operation rate).
· Research by Dr Ing in the US: better results if eyes are successfully aligned by the age of 2;
· Late alignment (e.g. age 4) can also produce excellent results in some patients, but less commonly than with earlier surgery.

Delaying surgery often results in the angle of misalignment increasing. The results of surgery are a little better if the angle of misalignment is no more than 25°.

'Statistics' can be misleading. YOUR child may or may not be one who will benefit from early surgery - your child just might be one that would do just as well with late surgery, or your child might be one that is so unstable that multiple surgeries might be required irrespective of the age at first successful straightening. However, early or very early surgery does give your child the best chance for the best result.

CET and Bad Focussing


A small number of children have both CET and bad focussing. Some of these children need glasses followed by surgery (and then followed by glasses again). Others need surgery to be later followed by glasses. Patients who have this combination tend to be a little more difficult to treat and are more likely to need a second (or third!) surgery as they grow up.

Pseudo Esotropia

This is a condition superficially similar to CET. It is due to a broad nasal bridge. There is less white of the eye showing near the nose and this is due to too much skin on the side of the nose rather than a true esotropia.

Surgery


Surgery to align the eyes involves weakening the inside muscle of each eye (the one that pulls each eye towards the nose) with an operation. When two-muscle surgery is required (the usual case) the surgery takes about 60 minutes.

Surgery is usually performed as a day case. The child comes into hospital in the morning (fasting for at least 6 hours), has the surgery (which requires a full general anaesthetic), and goes home later that day. The child is checked a few hours after the surgery and usually the next day as well. If everything is OK the child is seen again 10-14 days later. If a child is difficult to examine you may need to come in daily for a few days.

You can expect your child's eyes to be red and watery, and for this to just slowly get better. If the child's eyes become very red and irritable then antibiotic and cortisone medicine or eye drops are used. The redness usually takes 7-10 days to substantially lessen, but may take weeks before it goes away completely. If you carefully look at the inside corner of your child's eyes you may see a little bit of dark suture material on the white of the eye. This takes a few months to disappear.

Safety


Straightening surgery is 99+% safe - 'disasters' are very rare. Early complications (e.g. slipped stitches) are rare (1% or less). Disasters that can threaten vision are seen less than 1 in 10,000 cases.

A general anaesthetic in a healthy child has a "disaster" rate of less than 1 in 100,000. These numbers don't mean very much, but it probably means that the risk is about the same as the risk of driving to the hospital.

Botox


Botox has been used in CET for many years. In Australia this is "off label" for children, though there are no official fears about its safety (eg. it is used in much larger doses for cerebral palsy). There is much international uncertainty about the best way to use Botox in CET. I currently use Botox to supplement the effect of surgery in very large angle deviations.

Can it Get Better by Itself?


If a healthy infant has esotropia of 15 degrees or more measured on two occasions, then the chance of it getting completely better by itself is less than 1%. I personally have never seen such improvement, but do know colleagues who have had one or more cases.

'Alternative' or 'Natural' Therapy

With CET, I have seen many 'failures' and not heard of ANY successes with chiropractic treatment, craniosacral therapy, kinesiology, behavioural optometry etc. Please do not delay effective treatment by spending time and resources on ineffective therapy.

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