Subthreshold argon-laser irradiation elicits a pronounced vitreal prostaglandin E2 response

Chorioretinal production of prostaglandin type E2 (PGE2) as well as changes in vitreal protein and PGE2 concentrations were studied following retinal irradiation with low-power laser energy that caused ophthalmoscopically invisible ("subthreshold") laser burns. This was compared with changes following ophthalmoscopically visible ("suprathreshold") laser burns. Our results demonstrate that with in eyes exposed to the lower-power levels, the enhancement in vitreal PGE2 concentration persisted for a longer period and was more pronounced than in eyes exposed to the suprathreshold levels (a 3-fold and a 2-fold increase above baseline values, respectively). Protein leakage into the vitreous was noted only in the suprathreshold group, indicating a blood-retinal barrier (BRB) disruption. The findings of persistent, excessive PGE2 vitreal levels with no protein leakage in the subthreshold group suggest a possible anti-inflammatory role for PGE2 following low-power laser exposure.