Purpose: To investigate whether the developing retina is
more resistant to toxic insults than adult retina.
Methods: Gentamycin, a highly toxic aminoglycoside
antibiotic was injected to the right eyes of newborn rabbits, aged 10-30 days.
The left eye of each rabbit was injected with saline and served as control.
Electroretinographic studies were performed at 1 and 4 weeks after injection.
Retinal function was assessed from the b-wave ratio ]experimental eye/control
eye). After 4 weeks the rabbits were sacrificed, the eyes enucleated, and
histopathological studies performed.
Results: Mean b-Wave ratio was found to be dependent upon
the age of drug injection. It was close to unity when the injection was
performed at 11-13 days ]n=4) and
gradually decreased in relation to the age of injection. When gentamycin was
injected to rabbits close to 30 days old, b-wave ratio was severely reduced as
has been previously found in adult rabbits.
Discussion: The developing rabbit retina seems to be more
resistant than the adult retina to intravitreal gentamycin. It is suggested
that gentamycin major site of action is the photoreceptors. Therefore, in the
developing retina during the process of outer segment elongation, the
photoreceptors can recover from the insult of one dose of gentamicine.