Acute Retinal Morphologic Changes Following Panretinal Laser Coagulation in the Human Retina

Abstract

Purpose: : To determine the acute morphological in vivo changes in the human retina after panretinal photocoagulation in patients suffering from proliferative diabetic retinopathy (PDR).

Methods: : Ten patients with previously untreated proliferative diabetic retinopathy were evaluated in this prospective study. All patients underwent a photocoagulation therapy using a semi-automated patterned scanning laser system (PASCAL©) or with a conventional laser system (Novus Omni©, Coherent). Measurements were obtained with the Spectral Domain OCT (Spectralis OCT © Heidelberg Engineering), infrared (IR) and autofluorescence (AF) imaging at day 1, 2, 4 and 7 after treatment. The laser lesions were evaluated for changes in their retinal structure, diameter, and center point thickness.

Results: : On the first two days following treatment, the intra-retinal lesions were confined to the outer retinal layers i.e. the photo receptor layer (PRL), the outer nuclear layer (ONL) and in part the outer plexiform layer (OPL), and showed clear borders to the surrounding tissue in SD OCT. The loss of the marginal sharpness as well as the decrease in diameter and thickness could be observed within each lesion between day 3 and 7. These changes were caused by a strong scarring reaction in the PRL and ONL causing traction forces on the inner retinal layers lying above. The onset and extent of this tissue reaction to therapy depended on the administered Laser energy. By day seven coagulates had already lost their initial shape and reflectivity and showed a clear attachment of the OPL to the laser coagulate which was than visible as a hyper-reflective area at the level of the PRL.

Conclusions: : Panretinal laser therapy causes significant acute structural intra-retinal morphologic changes observable in the first seven days that can clearly be analyzed in SD OCT. Traction forces on the inner layers lying above the lesions emerged between day 3 and 7 indicating a characteristic scarification process depending on the laser energy used.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • laser • diabetic retinopathy