A squint (strabismus) refers to the misalignment of the eyeballs, usually causing the eye to turn inward or outward. An eye can also turn upward or downward but this is not as common. The most common types of squint are: Divergent squint (exotropia): one eye turns outwards, away from the nose. Convergent squint (esotropia): one eye turns inwards, towards the nose. Hypertropia: one eye higher than the other Hypotropia: one eye lower than the other. Squint can be constant or intermittent. Intermittent divergent squint is the most common types among Hong Kong population.

Squint can be congenital or acquired. Acquired causes includes diseases of nervous system, accidents, or uncorrected long or short sight. In many cases there is no know cause. However, there may be a family history of squints.

Treatment for squint may include: Glasses: Many childhood squints are related to uncorrected refractive error. Glasses may help to correct the squint or reduce the size of the squint. Prisms: Prisms may help to resolve the symptoms of double vision. Patching: Patching may be necessary during childhood to improve the vision of the squinting eye. Patching does not cure the squint. Orthoptic exercise: Orthoptic exercise may help to improve the control in some types of squints and improve binocular vision. Surgery: Surgery done by Ophthalmologist may be required. Some patients need a combination of these treatments.

Amblyopia, commonly know as lazy eye, means poor vision in one eye or rarely both eyes even with glasses on. Vision development starts from birth and continues during childhood up to 9 years old. Amblyopia occurs when the vision is interrupted for whatever reason during this period.

Common causes of amblyopia are: Refractive error: significant short-sightedness, long-sightedness, or astigmatism in one or both eyes. Defocusing image interrupt normal vision development which requires clear image stimulation on the retina. Strabismus (Squint): If one eye is constantly turning or turning most of the time, the brain favours the straight eye and causing amblyopia in the turning eye. Vision Deprivation: Obstruction of the light entering the eye by a droopy eyelid or a cataract, etc. interrupt normal vision development.

As the age increases, it becomes more difficult to improve vision, so the earlier the treatment the better. Firstly, the cause of amblyopia must be treated, e.g., refractive error should be corrected with full-time glasses wearing, followed by patching. The mainstay of amblyopia treatment is patching the good or better eye and make the child use the weaker eye. The duration of treatment varies from months to years, depending on the vision level, age of patching and the compliance. Most children achieve vision improvement with amblyopia treatment.