Amblyopic adults might be able to regain lost visual function in their affected eyes, according to a new study conducted at the University of Maryland. Previous studies of amblyopia have suggested that the condition is largely irreversible if not treated during early postnatal life; but, this particular study, conducted on adult rats, posits that ocular dominance plasticity may be restored later in life.     

The study specifically addressed deprivation amblyopia, which is typically categorized by the presence of a unilateral cataract in the patients affected eye at birth. Often, this condition is treated by first removing the cataract, and then occluding the stronger eye in an effort to force recovery of the damaged eye.

The authors of the study artificially induced deprivation amblyopia in adult rats by occluding one eye. We demonstrate that complete visual deprivation through dark exposure restores rapid ocular dominance plasticity in adult rats, the researchers say. We propose that the enhancement of ocular dominance plasticity by dark exposure may be well suited for combining with current behavioral therapy to improve treatment success for human amblyopia.

But, will the treatment be effective on humans? Optometrist Bruce Moore, Marcus professor of pediatric studies at the New England College of Optometry, does not believe so. The treatment regimen for amblyopia must be diligently followed to have any measurable success, he says. Because of the logistical difficulties involved in forcing the occlusion of an adults eye for an extended duration, Dr. Moore doubts that the positive results demonstrated in adult rats could be consistently replicated in humans.

He HY, Ray B, Dennis K, Quinlan EM. Experience-dependent recovery of vision following chronic deprivation amblyopia. Nat Neurosci 2007 Aug 12; [Epub ahead of print].