Delayed response to argon laser trabeculoplasty in monkeys. Morphological and morphometric analysis
S. Melamed, J. Pei and D. L. Epstein
In eight cynomolgus monkeys we performed argon laser trabeculoplasty and
evaluated morphological changes in the trabecular meshwork (TM). Four weeks
after laser treatment, the treated spots were detected as regions of
flattened and collapsed beams covered by a cellular sheet extending from
the corneal endothelium. The inner wall of Schlemm's canal beneath these
regions was flat, with no vacuoles despite fixation with intraocular
pressure maintained at 15 mm Hg. Adjacent nonlasered spots had wide open
intertrabecular spaces with herniations of juxtacanalicular TM and of inner
wall endothelium into and across the lumen of Schlemm's canal. The
herniations contained chronic inflammatory cells and large vacuoles.
Statistical morphometric analysis in three monkeys established that these
herniations were significantly wider, more numerous, and contained more
vacuoles than did control eyes. Our findings suggest that a biologic
process is involved in these reactions to argon laser trabeculoplasty.
Scarring is seen to obliterate TM in spots treated by the laser, and this
apparently causes the flow of the aqueous humor to be diverted through
adjacent nonlasered regions that become structurally altered to compensate
for this overload of flow.
