Far-red, high-resolution, reflection-free images of the anterior segment in retroillumination

Abstract

Purpose : Retroillumination observation of the anterior segment is a routine examination method as old as the slit lamp, but capturing good quality images is difficult because of patient glare, the presence of corneal and or lens reflections, and limited resolution. We have modified a slit lamp to overcome these limitations and present the first series of images obtained.

Methods : On a Topcon SL-D7 slit lamp, we replaced the light source with a far-red LED (Thorlabs, M780L3, 200 mW, 800 mA at 780 nm) and added a monochrome camera with sufficient resolution (Baumer, VCXU-123M). Reflection suppression was achieved by modifying the optical path (patent pending). In a clinical trial validated by an ethics committee (IDRCB: 2021-A01496-35), we acquired images of 5 different diseases after pupillary dilation: cataract, posterior capsule opacification, hereditary stromal dystrophy, Fuchs' corneal endothelial dystrophy (FECD), Bowman's membrane dystrophy.

Results : Our innovative prototype device made it possible to obtain images of 3000 x 4096 pixels for 13.3 x 9.7mm (x40 magnification). In 100% of the cases, one or more images focused on the area of interest were obtained without glare, and without disturbing reflections in 90% of the cases. Some pseudophakic patients showed minimal to moderate light reflection. The images were sufficiently resolved to allow precise analysis of disease areas, such as each guttae of the FECD.

Conclusions : Our retroilluminator prototype provides, for the first time to our knowledge, high-resolution images of the different structures of the anterior segment, easy to acquire and likely to facilitate the diagnosis and follow-up of patients. Improvements to the prototype are underway to remove some persistent reflections. One of the first applications will be the classification of the severity of endothelial damage in FECD

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.

 

far red high res reflection free retroilluminated picture of a stromal lattice dystrophy