Purpose: To characterize the morphology of patterned scanning laser (PASCAL) panretinal photocoagulation.
Methods: In this prospective cohort study, patients with proliferative diabetic retinopathy or severe nonproliferative diabetic retinopathy with high-risk characteristics, who were treated with PASCAL panretinal photocoagulation as part of their indicated clinical course, were serially imaged with spectral domain optical coherence tomography. Thirty eyes of 25 patients were studied from 1 hour to 21 weeks after laser treatment.
Results: Over a quarter (26.1%) of all treatment spots were imaged by spectral domain optical coherence tomography 1 hour after PASCAL panretinal photocoagulation. At 1 hour (±30 minutes) after PASCAL treatment, spectral domain optical coherence tomography demonstrated retinal pigment epithelium detachment in 23 of 27 eyes (85.2%) and in 36.1% of all imaged laser spots. Detachments occurred preferentially at the photocoagulation edges in 48.4% of pigment epithelium detachments (PEDs). Linear regression analysis revealed that average laser power (Pearson's r = 0.671, P < 0.001) and average laser energy (Pearson's r = 0.588, P = 0.001) were significantly associated with PEDs observed 1 hour after treatment. Pigment epithelium detachments occurred at a rate of 9.2% ± 4.9% at an average power of 0 mW to 400 mW, 37.8% ± 9.5% at 401 mW to 800 mW, 42.1% ± 5.6% at 801 mW to 1,200 mW, and 53.6% ± 5.7% at >1,200 mW. By a 1-week follow-up, no PEDs were observed, and the retinal pigment epithelium appeared morphologically similar to its preoperative structure by 3 weeks. Patient characteristics (study eye, sex, race, diagnosis, age, preoperative blood glucose, hemoglobin A1C, duration of diabetes, and body mass index) and other PASCAL parameters (number of laser applications, spot size, pulse duration, and average laser fluence) were not significantly associated with PEDs.
Conclusion: Retinal pigment epithelium detachment occurs 1 hour after PASCAL treatment over a wide range of laser settings. Laser power and energy are positively correlated with the occurrence of PEDs, which are no longer observed by 1-week follow-up. Future studies might examine various acute posttreatment time points and directly compare the morphology of PASCAL burns with that of longer pulse–duration laser modalities.
Spectral domain optical coherence tomography was performed on 30 eyes of 25 patients with proliferative diabetic retinopathy or severe nonproliferative diabetic retinopathy with high-risk characteristics after patterned scanning laser panretinal photocoagulation. Retinal pigment epithelium detachment occurred in 85.2% of eyes at 1 hour after treatment and was no longer identified by a 1-week follow-up. The percentage of pigment epithelium detachments occurring 1 hour after treatment correlated significantly with average laser power (Pearson's r = 0.671, P < 0.001) and energy (Pearson's r = 0.588, P = 0.001). Nearly half of retinal pigment epithelium detachments occurred at the edge of the laser burn.
*Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida;
†Duke University Eye Center, Duke University, Durham, North Carolina; and
‡Shiley Eye Center, University of California San Diego, La Jolla, California.
Reprint requests: Jeffrey L. Goldberg, MD, PhD, 9415 Campus Point Drive #0946, Shiley Eye Center, University of California San Diego, La Jolla, CA 92093; e-mail: JLGoldberg@ucsd.edu
Supported by National Eye Institute core grant P30-EY14801, an unrestricted grant from Research to Prevent Blindness, and the Walter G. Ross Distinguished Chair in Ophthalmic Research.
Three of the cases were presented, in part, as a poster at a meeting of the Association for Research in Vision and Ophthalmology in Fort Lauderdale, Florida, May 7, 2009.
None of the authors have any conflicting interests to disclose.
The authors contributed equally to the design of the study; conduct of the study, collection, management, analysis, and interpretation of the data; and preparation and review of the manuscript.