Visual fields and electroretinography following extensive photocoagulation
R. N. Frank
Twenty-four patients with proliferative or preproliferative diabetic
retinopathy underwent extensive argon laser photocoagulation in one eye.
Detailed central and peripheral visual-field examinations and
electroretinography were performed before treatment, and at intervals after
treatment. Visual field changes were as follows: (1) eight patients had
only mild to moderate constriction of all isopters, (2) 11 had discrete
scotomata in addition, (3) two had prominent nerve-fiber-bundle defects,
(4) three had severe constriction of all isopters, save (in two) that to
the largest peripheral test object. Electroretinographic b-wave amplitudes
were reduced an average of 40% to white test flashes. Blue test flashes
showed an even larger reduction of the rod response. This suggests the
receptors in approximately 40% of the retinal area are destroyed by such
extensive photocoagulation, covering predominantly that part of the retina
that has the highest concentration of rods.
