Session Title: New Drug Treatment and Technology II
Session Date/Time: Sunday 20/09/2015 | 09:00-10:30
Paper Time: 10:04
First Author: : E.Pedanova RUSSIAN FEDERATION
Co Author(s): : D. Buryakov V. Akopyan N. Semenova
PURPOSE:Subthreshold micropulse laser photocoagulation has shown an efficacy in vascular retinal disorders management. Moreover it has no limitations of threshold laser related to injury of retina that result in vision quality reduction. However, there is still no consensus about the most safe technical parameters of micropulse laser. Subthreshold micropulse laser exposure provides high selectivity to retinal pigment epithelium and upregulates cytokines expression, but the influence on expression of pigment epithelium-derived factor (PEDF) hasn’t been described. The purpose of the study is to evaluate morphological and immunohistochemical features of subthreshold micropulse yellow laser photocoagulation (SMYLP) of rabbit retina in experiment.
FSBI “The acad. S.N.Fyodorov Eye Microsurgery Complex” of the Minpublhealth of Russia”; Lomonosov Moscow State University, School of Medicine, Department of Ophthalmology
Morphological study included eight eyes of eight pigmented rabbits after SMYLP («Supra» laser, 577 nm). To determine the most safe parameters, which do not cause retinal tissue damage, SMYLP was performed in four combinations of laser exposure parameters(modalities): Modality “A” - micropulse duration (MD) 0.1 ms; train 100 ms; duty cycle (DC) 5%; laser spot diameter (LSD) 100 µm (n=2); Modality “B” - MD 0.1 ms; train 200 ms; DC 5%; LSD 100 µm (n=2); Modality “C” - MD 0.1 ms; train 100 ms; DC 10%; LSD 100 µm (n=2); Modality “D” - MD 0.1 ms; train 200 ms; DC 10%; LSD 100 µm (n=2). Laser power was adjusted individually in each case after testing. Laser spots were applied on central part of rabbit retina in grid-like pattern with 100 µm spacing. Four rabbits were sacrificed at 24 hours posttreatment and the other four were sacrificed at 1 month posttreatment to reveal morphological changes of retina. The immunohistochemical study was performed in one eye (1 rabbit) treated with laser modality determined as the most safe towards retinal structure during morphological study to evaluate the expression of pigment derived-epithelium factor (PEDF) after SMYLP. The rabbit was sacrificed 24 hours posttreatment.
The morphological study data showed no retinal structure changes after SMYLP using Modality “A” of laser exposure parameters at both time points and using Modality “B” at 24-hours time point. The photoreceptor layer damage, increase of intercellular gaps, cell junctions disruption in outer nuclear layer, nuclei of apoptotic cells and nerve fiber layer thickness reduction were seen both at 24 hours and at 1 month time point using laser exposure Modality “C” and “D”. Similar changes were observed 1 month after SMYLP using Modality “B”. According to morphological findings laser exposure Modality “A” was preferred to use in immunohistochemical study. Immunohistochemical study showed expression of PEDF after SMYLP using low laser exposure parameters compared to fellow (intact) eye at 24 hours time point.
SMYLP is a safe procedure for retinal structure while using low laser exposure parameters. One of the significant biological effects of SMYLP in short-term posttreatment is PEDF expression, known to be the antagonist of Vascular Endothelial Growth Factor (VEGF), playing an important role in pathogenesis of many vascular retinal disorders. Nevertheless, further long-term investigation of PEDF expression and PEDF/VEGF ratio after SMYLP should be conducted.