In vivo retinal morphology after grid laser treatment in diabetic macular edema

To analyze immediate in vivo intraretinal morphologic changes secondary to standardized grid photocoagulation using spectral domain optical coherence tomography (SD OCT).

Prospective clinical trial.

Thirteen consecutive patients with treatment-naïve clinically significant diabetic macular edema (DME).

Before and 1 day after standardized grid photocoagulation using the PASCAL system (Pattern Scan Laser, OptiMedica Corporation, Santa Clara, CA), Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) examinations based on an eye-tracking system, infrared fundus imaging, color fundus photography, and biomicroscopy were performed. A standardized visual acuity assessment (Early Treatment Diabetic Retinopathy Study protocol) and fluorescein angiography were performed at baseline.

Morphologic changes secondary to grid laser treatment.

One day after laser therapy, immediate morphologic alterations of only the outer retinal layers, that is, the retinal pigment epithelium (RPE), the photoreceptor layer (PRL), and the outer nuclear layer (ONL), were observed. The shape of the laser-induced lesions did not show a sagittal alteration pattern throughout all 3 of the layers, however, but rather seemed to follow an oblique pathway throughout the ONL, changing direction at the level of the external limiting membrane and proceeding sagittally through the PRL and RPE. These morphologic changes also induced biometric changes, such as a decrease in central retinal thickness combined with local thickening at the lesion site, especially in the PRL.

Spectral domain optical coherence tomography provides new insight into the immediate morphologic changes after laser treatment using the PASCAL laser system. Standardized grid photocoagulation induces characteristic homogenous alteration in the neurosensoric retinal layers. Biometric changes, indicating an immediate effect, were observed within 1 day after treatment.