Effects of Laser Physical Parameters on Lesion Size in Retinal Photocoagulation Surgery: Clinical OCT and Experimental Study

Introduction: The aim of the present study was to determine burn intensity in retinal laser photocoagulation based on laser parameters; wavelength, power, beam size and pulse duration, using Optical Coherence Tomography (OCT), fundus camera, physical eye model and computer simulation in a clinical study.Materials and Methods: Participants were ۱۰ adult patients between ۵۰-۸۰ years with proliferative diabetic retinopathy. A multicolor-photo coagulator with ۵۳۲ nm green and ۶۷۲ nm red for retina photocoagulation in diabetic retinopathy was used to investigate the participants. Lesion size was measured for spot sizes ۵۰ and ۱۰۰ μm, with ۱۰۰ and ۱۵۰ mW laser power, and pulse duration ۵۰ and ۱۰۰ ms by OCT. Artificial eye and Zemax-optical design software were used with the same laser parameters.Results: Appearance of OCT and fundus images showed direct relationship between retina burn size and lesion intensity with exposure time and power and also reverse relationship with laser spot size. Compared to red wavelength, burn size and lesion intensity increased in green wavelength. On the other hand, results from physical eye model were the same as clinical examination shown. Laser spot size in retina with Zemax simulation demonstrated that red wavelength was greater than green one.Conclusion: This study showed shorter pulses provide decrease in duration of laser surgery with significantly reduced pain. Results and calculations described in this article can help clinicians adjusting the required total coagulated area, the number of lesions and pattern density.

Keywords:

Retinal Laser Surgery , Photocoagulation , Diabetic Retinopathy , Lesion Size , Optical Coherence Tomography , Laser Parameters of surgery