Evaluation of chorioretinal complex tissue response on subthreshold micropulse yellow laser (577-nm) photocoagulation of retina in experiment

Abstract

Purpose. To evaluate chorioretinal complex (CRC) tissue response on subthreshold micropulse yellow laser (577-nm) photocoagulation (SMYLP) of rabbit retina in experiment and to determine its safest laser exposure energy settings.Material and methods. Morphological study was performed to determine the safest laser exposure settings, which do not cause CRC structure damage. The study was carried out in 8 eyes of 8 rabbits 24 hours and 1 month after the SMYLP. The SMYLP was performed in four combinations of laser exposure settings. Four rabbits were sacrificed at 24 hours post-treatment and the other four were sacrificed at 1 month posttreatment to reveal morphological changes of CRC. The CRC tissue response was evaluated during immunohistochemical study in two eyes (2 rabbits) after SMYLP, wherein the expression of pigment derived epithelium factor (PEDF) 24 hours post-treatment was assessed.Results. The morphological study data showed no retinal structure changes after SMYLP using low-level energy settings, including 100ms train duration and 5% duty cycle. Immunohistochemical study revealed expression of PEDF after SMYLP using selected laser exposure settings compared to fellow (intact) eyes at 24 hour s time point.Conclusions. SMYLP is safe for retinal structure integrity while using low laser exposure settings. One of the significant biological effects of SMYLP is the PEDF expression in short-term post-treatment. Nevertheless, further long-term investigation of PEDF expression and PEDF/VEGF ratio after SMYLP should be conduc ted.

Keywords

• subthreshold micropulse yellow laser photocoagulation
• immunohistochemical study
• morphological study
• pigment epithelium derived factor
• retinal pigment epithelium.