Clinical Effect Of Photocoagulation On Retinal Thickness In Eyes With Proliferative Diabetic Retinopathy

Objective To investigate the effect of panretinal photocoagulation (PRP) by different wavelengths of krypton laser on retinal thickness in eyes with diabetic retinopathy (DR).Methods This was a prospective case-control study of 60 eyes (30 right eyes as krypton green laser group and 30 left eyes as krypton yellow laser group) from 30 patients diagnosed to have diabetic retinopathy (DR). They were treated with panretinal photocoagulation (PRP) by a wavelength of 532 nm of krypton green laser or a wavelength of 561 nm of krypton yellow laser respectively. Baseline and morphological changes on optical coherence tomography (OCT) were evaluated before PRP, one hour, one week, two weeks, and four weeks after PRP. The thickness of laser spot on nasal optic area was recorded and compared. The thickness of the laser spot of the same eye at different time points were analyzed by using paired sample t-test, while the thickness of the laser spot of the different eyes at the same time point were analyzed by using independent sample t-test.Results Sixty eyes of 30 patients received krypton green laser and krypton yellow laser for PRP respectively. The retinal thickness before PRP was measured as baseline and compared with that at one hour, one week, two weeks, and four weeks after PRP. OCT showed morphological changes of the same eye after PRP:the mean thickness of retina was increased by 8.4% at one hour after PRP and dropped by 9.5% at one week later. The thickness of retina were decreased by 17.1% at two weeks after PRP. The difference between different time points was statistically significant. It remained stable and unchanged at four weeks after PRP compared with the data at two weeks after PRP. No statistically significant difference was found between different eyes at the same time point. Three months after PRP, the BCVA in 85% of the patients were increased or kept stable while 15% of the patients with the BCVA decreased.Conclusion Krypton green laser and krypton yellow laser can be used effectively in treating diabetic retinopathy, and there is no statistically significant difference between them in the effect of pigment epithelium layer of retina. The thickness of retina increased by 10% one hour after PRP and kept stable at two weeks after PRP.