Hi Yingda
I saw in another of your questions that you are referring to intermittent exotropia (intermittent XT), where the child's eyes sometimes are straight and at other times turn outwards.
This is perhaps one of the most common squints that we see in Singapore.
There are various aspects in assessing how significant the condition is, in a particular patient.
1. Patients with intermittent XT can control their eye position some of the time, but not all of the time. If the squint appears more often, or for longer periods of time, that could be an indication of deterioration in the condition
2. If the angle of the squint is getting larger, that could also be a sign of deterioration
3. Control of eye position is also determined in clinic and monitored. Sometimes the squint becomes obvious only if we cover one eye, and quickly becomes straight again by itself-this is good control. Poor control is shown when the eyes deviate spontaneously and cannot straighten by themselves.
4. 3D vision, or stereoacuity is monitored. If this worsens, it could also be a sign that the squint is worsening.
Like all squint operations, the aims of surgery can be to preserve/restore binocular function (including 3D vision/stereopsis), prevention of double vision, and cosmesis/appearance.
Surgery for intermittent XT may be considered if there are signs of deterioration, of which one of the most important considerations is the first point-ie the XT is happening for longer and longer periods of time. If the XT becomes constant, there is also the risk of 'lazy eye' or amblyopia, where vision is not good despite correction of spectacle power.
Although it can be a bit controversial, most of the time if surgery is needed we prefer to operate when the child is a bit older eg above 4 years of age. However, if a child has eg deteriorated rapidly to a constant squint, earlier surgery might be advisable. Each case has to be considered on its own particular characteristics, to some extent.
Having said all that, don't worry as long as you are being monitored by an eye doctor. Although I don't have the actual statistics, in my experience most children with intermittent XT don't deteriorate to such an extent as to require surgery.
