Amblyopia or Lazy Eye Syndrome
Dr Virender Sachdeva, Consultant, Pediatric Ophthalmology, Strabismus and Neuro-Ophthalmology, L V Prasad Eye Institute Visakhapatnam.
Sometimes our children’s eyes can be afflicted by a condition known as lazy eye syndrome which can go unnoticed till a long time and could be a potentially blinding condition. It literally means one or both eyes have a subnormal vision in the absence of any structural problem for the same.
This condition is one of the leading causes of the childhood visual impairment globally. It is estimated that the prevalence of this conditions is about 2-12% in various parts of India. Take the example of this patient, Shruti, a six years old girl who was brought to us with the complaints of poor vision in the right eye noticed since last one week. She was diagnosed to have poor vision at a school screening camp conducted by our institute. Following a careful eye examination, she was found to anisometropia, i.e., a gross difference in the spectacle power in the two eyes, right eye being -4.5 Diopters and left eye being -0.5 Diopters. Even with the glasses, her best corrected visual acuity was 20/ 80 in the right eye and 20/20 in the left eye. Her rest of the ocular examination was normal, so she was diagnosed to have anisometropic amblyopia.
This is common to many patients with amblyopia, their condition remaining undiagnosed due to problem in one eye only and child being able to perform normal function from the other eye. The chief casues of amblyopia are: Squint (crossed eyes); anisometropia (difference in the glass power between two eyes); ammetropia ( large uncorrected glass power in both eyes) and stimulus deprivation (conditions that do not let the light pass into the eye like cataract, ptosis, corneal scars, etc.
These condition lead either to a poor image formation in the affected eye or a difference in the images perceived by the two eyes. Hence, the normal process of visual maturation remains incomplete. Since most of this maturation takes place during 6 months to 7 years of life, many of these patients remain undiagnosed as children cannot express their problems and there is lack of awareness in the parents. Amblyopia or Lazy eye syndrome can thus be diagnosed with the presence of the early screening of the children.
Treatment of this condition is actually simple and involves a correction of the underlying problem such as a proper use of the spectacles; surgery for a pediatric cataract, ptosis, squint and and a specific therapy which promotes the use of the amblyopic/ lazy eye. There are two principal ways to achieve this: Patching and Penalisation (which may be called as 2 P’s of amblyopia therapy).
Patching (also called as occlusion) involves putting and adhesive patch over the stronger eye for a period of several weeks to months. This is done for a few hours/ day depending on the degree of the difference in the vision between the two eyes. A novel form of therapy involves splitting this patching treatment into two or more sessions to make to achieve the desired number of hours of patching (split hours patching).
Penalisation means ‘ penalising’ the child for using the better eye by blurring the vision in the affected eye by the use of some medicines like atropine (atropinisation) or frosted glasses (optical penalisation) that make the vision hazy in the better eye . The medicine (atropine) is more effective than optical penalisation and can be used one to two times a week as compared to using frosted glasses that need to be used daily.
These specific treatments force the child to use the eye with amblyopia. Patching/ penalisation stimulate the vision in the weaker eye and helps that part of the brain that manages vision to develop more completely. This is also combined with about one hour/ day of intensive treatment session with the visual stimuli which is called as near vision exercises. This may include filling the colors, making drawings, mapping the dots, etc appropriate for the age of the children.
Scientific literature shows that both of the treatment options, patching and penalisation are equally effective in treatment of amblyopia. However, as stated earlier the process of visual maturation takes place between 6 months to 7years of life, hence these treatment modalities are most effective if started earlier than 7 years of age. However, recent studies have also shown that for some types of amblyopia, good response may also be achieved up to 17 years of age.
However, it is sometimes difficult to make the children wear the patches regularly and can cause a significant emotional strain on the children as well as parents. Hence, it requires repeated sessions of counselling for the children and their parents to make them understand the importance of this therapy. With repeated sessions of timely counselling good results can be achieved in over 85% of the children with amblyopia.
The most important determinants of success of the amblyopia therapy are: age (< 7 years best prognosis), depth of amblyopia (depends on best corrected visual acuity of amblyopic eye), spectacle wear (if needed) and compliance to therapy. Thus, good response may be achieved in most children if the condition can be diagnosed early and glasses/ patches are worn appropriately.
To conclude, amblyopia which is an important cause of the avoidable blindness in children, needs concentrated efforts on part of parents, teachers, ophthalmologists and optometrists at the early screening to diagnose early; appropriate and timely glasses or surgery and regular specific treatment with patching or penalisation or both under careful guidance of a trained ophthalmologist.
Virender Sachdeva, MS, DNB
Pediatric Ophthalmology, Strabismus and Neuro-ophthalmology,
LVPEI, GMRV Campus