ARTICLE BY: Dr. Lisa Pray

WHAT IS REFRACTIVE AMBLYOPIA?

Refractive Amblyopia (or lazy eye) occurs when the eye is unable to achieve good visual acuity even with proper glasses because of a significant prescription or unequal prescription between the two eyes. Most commonly it results from significant unequal prescriptions. In this type of amblyopia, the difference in the prescription between the eyes disrupts the normal development of the visual pathway because one eye receives a clearer image than the other eye. The visual pathways develop most rapidly from birth to 6-8 years of age, with most of the development occurring in infancy. Consequently, it is important for amblyopia to be diagnosed as early as possible to allow for intervention to attempt to improve vision in the weaker eye during this critical period of development. If amblyopia is left untreated during this time period, the prognosis for good vision in the amblyopic eye is poor.

HOW IS IT TREATED? The first step to treat refractive amblyopia is to correct the underlying prescription with glasses and/or contact lenses. In cases where there is a significant difference between the two eyes, it may be more advantageous to correct the prescription with contact lenses. This is because contact lenses minimize the size difference of the image that the brain receives from the two eyes, allowing it to more easily process the two images.

If vision remains weaker in the lazy (amblyopic) eye after wearing glasses or contact lenses for a couple months, the next step in treatment is to initiate patching. Patching is a therapy in which the stronger eye is covered (while maintaining full time wear of the glasses or contact lenses) for a prescribed number of hours per day to allow the brain to recognize the weaker, lazy eye. This hopefully will strengthen the neural connections in the visual pathway for the weak eye leading to improved vision in the weak eye and improved depth perception when both eyes are used together. The weaker the lazy eye, the greater the number of hours that the good eye must be patched.

Patching therapy usually lasts from 6-12 months with follow-up at the optometrist’s office every 2-3 months to check for progress. The most significant improvement (assuming compliance) usually occurs in the first 3-4 months. Adding visual tasks (such colouring, puzzles, etc.) helps to speed up visual improvement. Sometimes, vision can start to deteriorate again once patching is stopped, and occasionally, patching may have to be re-initiated. In some cases, patching does not improve vision because the lazy eye (amblyopia) is too deeply set. However, in most cases, there is some visual improvement.

Dr. Lisa Pray is a practicing optometrist in London Ontario’s East London Optometry.