Squint refer to appearance in which both eyes are not facing the same direction. It can be exo (eye deviated out) , eso (eye turning in), hypo (eye turning down), or hyper (turning up) or in combination. It can be congenital (develop since birth) or acquired (develop later in life).
For congenital cause of squint, it can be due to the brain unable to coordinate the eye muscle movement, abnormal eye refractive power (too short sighted or long sighted) or disease which reduced vision in one eye (eg. cataract or other eye abnormalities).
The cause of developing squint later in life can be neurological cause (nerve that supply muscle is not working) or mechanical (muscle entrapped in a fracture). Sometimes it can be both , eg. in a car accident in which there is a fracture in the floor of orbit with entrapment of muscle together with multiple cranial nerve injury. Recently , high myopia (severe short-sightedness) is also recognised to be associated with double vision.
In a child, the eye which is deviated out may develop less image information and hence become lazy and hence not able to see well if left untreated (ambloypia). Therefore it is important to treat squint otherwise child will have reduced vision in the 'squinting eye' and will not develop stereoscopic (3D ) vision which may adversely their career choices. Sometimes, the child may also develop abnormal head movement (eg head tilt) in order to achieve single vision. It is important to note that children seldom complained of double vision as they suppress the abnormal easily and hence parents need to pay attention.
However, it is important to note that many Chinese child may with wide distance between eye (wide inter-canthal distance) with epicanthic fold may appear to have squint with both eyes turning in. However, a visit to the doctor usually will reveal otherwise. No treatment is required for this group of children.
In adult, squint can cause double vision which many people find disabling. The double vision can be horizontal or vertical depending on which muscle it affected. It is important to seek ophthalmologist attention to identify the issue.
As some cases of squint may be related with brain disorder, it is important to seek doctor to confirm the diagnosis and cause of squint first.
Treatment varies with cause. In some cases, medical treatment such as glasses or fusion glasses) may be adequate. However, in other scenarios, squint surgery or stabismus surgery may be required to restore binocular single vision and stereopsis. This is an operation require general anesthesia but can be discharged same day post recovery. Sometimes, in order to restore single vision, adjustable sutures may be required.
Pre op: This girl has left divergent squint (left eye deviated out) since young. She is keen to look more normal in order to get a job/training opportunity.
Post op: Eyes looks straight and normal now. The patient regained confidence.
Pre op: this patient has a slightly more complicated squint with right eye deviated in and left eye deviated up.
Post op: The child looks better with a straighter eyes. Now he can concentrate on building his life and getting a job.
Pre op: convergent squint in a Down syndrome patient
Post Squint surgery: Both eyes look straighter now.