Purpose: To investigate changes in retinal thickness, drusen volume, and visual acuity as a result of subthreshold nanosecond laser (SNL) intervention in patients with intermediate age-related macular degeneration (ARMD).

Study Design: Retrospective chart review.

Methods: Patients with intermediate ARMD treated with a single session of SNL (2RT®, Ellex R&D Pty Ltd, Adelaide, SA, Australia) were included in this study. Swept-source OCT (SS-OCT) imaging (Triton; Topcon Medical Systems, Tokyo, Japan) was performed within 6 months before and after SNL treatment. Retinal layers were segmented using the artificial intelligence-enabled Orion® software (Voxeleron LLC, San Francisco, CA, USA). The macular region, defined as a 6mm-diameter circle centered on the fovea, was analyzed according to the Early Treatment Diabetic Retinopathy Study (ETDRS) map. Mean difference and standard deviation in baseline and post-treatment retinal layer thicknesses are reported. P-value <0.05 was statistically significant.

Results: 37 eyes from 25 patients were included in this study with a mean age of 74.7 ± 9.2 years. An average of 51 ± 6 spots were applied around the macula of each study eye, with a mean spot power of 0.33 ± 0.04mJ. Increases in total retinal thickness were observed within the outer temporal and inferior sectors (P<0.05). Within the annulus, there was an increase in thickness of the outer plexiform layer (OPL) [1.29 ± 3.11μm, P=0.02] and sub-retinal pigment epithelial (RPE) space [0.88 ± 2.41μm, P=0.03], defined between the RPE and Bruch’s membrane. An increase in thickness of 1.13 ± 2.55μm (P=0.01) was also noted in the inferior sector of the photoreceptor complex, defined from the inner and outer segment junction to the RPE. Decreases in thickness were observed within the superior sector of the inner nuclear layer (INL) [-1.08 ± 2.55μm, P=0.01], and within the annulus of the outer nuclear layer (ONL) [-1.44 ± 3.55μm, P=0.02]. Total retinal and sub-RPE volumes following SNL were not significantly different from baseline (P>0.05), and there was no change in visual acuity in this study (P=0.24).

Conclusions: At 6 months post-SNL treatment, there were sectoral increases in OPL, photoreceptor complex, and sub-RPE space thicknesses and sectoral decreases in INL and ONL thicknesses. This study contributes to the evolving understanding of SNL treatment, and suggests a deviation from the geographic atrophy that is known to occur with progression of ARMD. Longitudinal follow-up of these patients with OCT imaging will provide further insight on the retinal changes that occur in response to SNL intervention and its ability to impact the natural history of this condition.

Effects of subthreshold nanosecond laser therapy in intermediate age-related macular degeneration using artificial intelligence (STAR-AI)

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