PURPOSE: We evaluated the morphologic changes in retinal structure after laser photocoagulation using supra- and subthreshold laser fluence. METHODS: In a prospective cohort study 10 consecutive patients received scatter laser photocoagulation. Treatment was performed using a semiautomated patterned scanning laser system. In a study area adjacent to the temporal vessel arcades, 2 × 2 pattern laser spots were applied with halving the flux of the laser power in a stepwise manner starting from a power producing a typical grayish lesion. The study areas then were imaged on days one, three, and seven, and on months one, two, three, and six using color fundus photography, autofluorescence (AF), infrared (IR) imaging, and spectral domain optical coherence tomography (SD-OCT). RESULTS: The starting threshold power lesions each were visible on color fundus photography, IR, and AF in all patients, and showed characteristic changes on OCT throughout the follow-up period. The halved flux laser burns (first step) were undetectable ophthalmoscopically during the laser session, but during the follow-up always were detectable on IR and AF images, and sometimes on fundus photography. On OCT they showed changes similar to the suprathreshold laser scars, but were much smaller in diameter, and in some instances an inward migration of the photoreceptor layer was observed. CONCLUSIONS: Subthreshold laser burns with halved energy flux produced similar morphologic changes in the retina as threshold power, but with a smaller size. They induced less collateral damage to the neuroretina, and permit a level of reorganization in the outer retina. (ClinicalTrials.gov number, NCT00682240.).
PURPOSE: We evaluated the morphologic changes in retinal structure after laser photocoagulation using supra- and subthreshold laser fluence. METHODS: In a prospective cohort study 10 consecutive patients received scatter laser photocoagulation. Treatment was performed using a semiautomated patterned scanning laser system. In a study area adjacent to the temporal vessel arcades, 2 × 2 pattern laser spots were applied with halving the flux of the laser power in a stepwise manner starting from a power producing a typical grayish lesion. The study areas then were imaged on days one, three, and seven, and on months one, two, three, and six using color fundus photography, autofluorescence (AF), infrared (IR) imaging, and spectral domain optical coherence tomography (SD-OCT). RESULTS: The starting threshold power lesions each were visible on color fundus photography, IR, and AF in all patients, and showed characteristic changes on OCT throughout the follow-up period. The halved flux laser burns (first step) were undetectable ophthalmoscopically during the laser session, but during the follow-up always were detectable on IR and AF images, and sometimes on fundus photography. On OCT they showed changes similar to the suprathreshold laser scars, but were much smaller in diameter, and in some instances an inward migration of the photoreceptor layer was observed. CONCLUSIONS: Subthreshold laser burns with halved energy flux produced similar morphologic changes in the retina as threshold power, but with a smaller size. They induced less collateral damage to the neuroretina, and permit a level of reorganization in the outer retina. (ClinicalTrials.gov number, NCT00682240.).