Abstract
Purpose: :
To evaluate the retinal reflectivity response after irradiation at threshold and sub–threshold powers with optical coherence tomography (OCT)
Methods: :
Five eyes of five patients with diabetic retinopathy were exposed to sub–threshold and threshold laser irradiation with a diode laser emitting at 805 nm. Threshold lesions were obtained with 100% duty cycle (continuous wave) at various powers, exposure times, and spot sizes. Sub–threshold lesions were not visible at ophthalmoscopy and were obtained with 100% duty cycle and halving the power used for visible lesions or with 15% duty cycle (micropulse) at various powers. OCT was performed prior to irradiation and at ten minutes after laser exposure
Results: :
A consistent OCT pattern emerged after irradiation at threshold powers. Areas exposed to laser spots were visible at ophthalmoscopy and showed homogeneous increased reflectivity involving all the retinal layers. OCT detected non ophthalmoscopically visible laser lesions obtained with continuous wave emission modality as areas of increased reflectivity involving the inner layers of the retina. Irradiation with 15% duty cycle did not show any reflectivity change as detectable with OCT
Conclusions: :
Optical coherence tomography can detect retinal reflectivity changes that occur following laser irradiation at threshold and sub–threshold powers. OCT may be of help in guiding subthreshold non visible laser treatments in a clinical setting
Keywords: laser • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)