Laser photocoagulation increases PVR severity
Purpose. To determine the effect of peripheral scatter laser in a model of PVR. We have hypothesized that severity of PVR is regulated by an activated vitreous microenvironment fVME) created, in part, by growth factors released from activated RPE cells under detached retina and cells recruited into the vitreous by these factors. We evaluated the role of scatter laser in activating the VME anc thereby influencing the course of PVR in a rabbit model of PVR due to giant retinal tear. Methods. PVR was induced in albino rabbits by creation of a large retinal break in the inferior retina, followed by intraocular injection of 200 ng of plateletderived growth factor. The animals were divided in 3 groups: no laser treatment, superior hemi-retinal scatter phoiocoagulation (away from the break), or inferior hemi-retinal scatter photocoagulation (around the break). All eyes were examined weekly for 6 weeks and vitreous samples were aspirated periodically for flow cytometric determination of total cell concentration, a measure of activated VME. Results. Animals without laser treatment demonstrated the typical pattern of slowly progressive PVR. At week 3, none (0%) of the retinas revealed severe traction retinal detachment (TRD). However, by week 5, 60% of the animals developed TRD. Animals that received inferior scatter laser (around the retinal break) demonstrated severe and rapidly progressive PVR with more than 80% of the animals developing TRD by week 3. Animals that have received superior laser (away from the break) demonstrated similar time course to the untreated control group. Flow cytometric analysis at early time points suggested that increased vitreous cellular infiltration was correlated with inferior laser treatment. Conclusion. Scatter laser coagulation around the break, but not away from the break, appeared to exacerbate PVR. We suspect that laser activates RPE production of growth factors which diffuse into the vitreous through the retinal break to stimulate the VME.
Morales, PH; Hernandez, E; Rolon, A; Cousins, SW
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