Pan-retinal photocoagulation (PRP) laser spots from outer (avascular) layer of retina (Fig1). This slab is defined as bottom of OPL to Bruch’s membrane, which includes ONL, Ellipsoid Zone (EZ) and RPE. Any visible laser spots from this slab can be classified as ≥ grade 1 of L’Esperance scale. Light gray background represented intact photoreceptors (EZ), while dark gray background in PRP zone was from EZ disruption. Dark gray in macular with blurry boundaries was from intra-retinal fluid. Black spots in posterior pole were shadows of hard exudates. In addition, pores of lamina cribrosa can be identified in the area of optic disc.

Fig2 is Deep Vascular Complex (DVC) structural slab, defined as IPL (lower boundary) +6um to OPL (lower boundary) +9um. Includes most part of INL, all OPL and some ONL. Laser spots visible from this slab can be classified as ≥ grade 2 scale. Bright white signals in posterior pole were hard exudates. Black cavities in fovea were cystoid macular edema.

Fig3 is Superficial Vascular Complex (SVC) structural slab, defined as ILM to IPL+9um. Includes RNFL, GCL, IPL and partial INL. Light gray laser spots visible from this slab can be classified as grade 3 scale, which is classical endpoint of PRP treatment. Bright gray or white spots in this slab may indicate over dose energy setting of photocoagulations for diabetic retinopathy (DR). More details can be observed from this slab as well. Such as nerve fiber bundles around optic disc, microaneurysms (little white dots) at temporal part of macular.

Laser energy spreads in both directions. Burn spots can be found in Choriocapillaris (Fig 4) and Sattler’s & Haller’s layers (Fig 5) too. Clinically, evaluation of retina involvement is more important than of choroid for Proliferative Diabetic Retinopathy (PDR).

Such observation can be conducted even right after PRP therapy, providing better guide of treatment for PDR patients. 120° images were captured through one scan from a 400KHz SS-OCTA system produced by TowardPi. Extremely fast speed and wide filed optic design brings theory to the reality.

Please note that most of time, laser spots cannot be visualized from blood flow mode. All images presented here are structural enfaces. Information regarding flow images can be found from more of our other posts.

“TowardPi high-speed full-range HD OCTA meets all the expectations of ophthalmologists for fundus blood flow imaging, and is still continuously improving, upgrading and breaking through. I believe that, like its imaging products, TowardPi Medical will go faster, wider and farther!” Images courtesy and endorsement by: Prof. MeiXia Zhang, West China Hospital of Sichuan University, Chengdu, China.

Editor: Dr. Jian Zhou (TowardPi Medical)