Long-Term Multimodal Imaging Analysis of Selective Retina Therapy Laser Lesions

Abstract

This study evaluates the long-term effects of selective retina therapy (SRT) on the retinal pigment epithelium (RPE) and neuroretina in patients with central serous chorioretinopathy. SRT was performed on 36 patients using a Nd:YLF-Laser at 527 nm (R:GEN^®, Lutronic, Goyang-Si, Republic of Korea). A total of 994 titration spots were examined using up to three years' multimodal imaging. Leakage in fluorescein angiography (FA) was observed after SRT in 523 lesions and resolved after one month. SRT lesions were not visible clinically, but appeared as brightly reflective areas in infrared and multicolor images. Normal morphology was observed in optical coherence tomography (OCT) immediately after SRT. After one month, thickening of the RPE and interdigitation zone changes were seen and disappeared after 539 ± 308 days. No RPE atrophies occurred during the observation period. Decreased fundus autofluorescence (FAF) was mostly observed directly after SRT followed by increased FAF at one month, which faded over time. A significant decrease in the number of visible lesions in the FA and FAF was observed within the three-year follow-up. OCT findings are consistent with animal studies showing SRT-related defect closure by hypertrophy and migration of neighboring cells without RPE atrophy or photoreceptor damage. This suggests that SRT is a safe treatment option for macular diseases and does not lead to retinal atrophy.

Keywords: OCT; central serous chorioretinopathy; fluorescein angiography; fundus autofluorescence; micropulse laser; selective retina treatment; subretinal fluid.

Figure 1

SD-OCT images of the test lesions over 24 months. The top row shows the infrared image of the depicted area (green line) and an enhanced image section of the titration lesions 1 month after SRT. Typical dune-shaped RPE changes are clearly visible in the enhanced image section (circled). Irregularities within the RPE layer and the interdigitation zone are still visible at the 9-month follow-up examination. However, the RPE layer fully reverted to its normal morphology at 18 months.

Figure 2

Infrared images (A), multicolor images (B) and fundus photographs (C) of the SRT test lesions at baseline, 1-month and 3-month follow-up examinations. No lesions are visible in any of these recordings directly after performing the SRT. The foci appear in the infrared image (A) and multicolor images (B) one month after the irradiation and start to fade over time. It is not possible to detect the lesions at any time in fundus photography (C).

Figure 3

FAF images of SRT test lesions of 3 different patients (A–C) taken over a period of 6 months. Decreased autofluorescence often appeared in the area of irradiation directly after SRT (B,C) but this effect is absent in some cases (A). Increased autofluorescence is clearly visible 1 month after SRT. This can be very apparent (C) or interspersed with more (B) or less (A) decreased autofluorescent areas. This increase in FAF fades completely (A) or only slightly (B) over time. However, in some patients it remains constant (C).

Figure 4

FAF images of SRT test lesions over 3 years. The first image shows leakage of the lesions in FA after treatment. Increased autofluorescence is visible 1 month after treatment. Later, a mainly decreased autofluorescence with interspersed increased autofluorescence is observed. No RPE atrophy was observed over time.

Figure 5

FA images of the titration lesions over 6 months. Leakage that indicated RPE cell death was seen directly after SRT. No more leakage was visible 1 month after treatment. Hyperfluorescent spots interspersed with hypofluorescent areas can be observed within the titration lesion area. It was observed that these lesions shrink over time.

Figure 6

Multimodal imaging of SRT titration lesions 1 year after treatment. The lesions appear as regressive hyperreflective spots in the infrared image (A). OCT (B) shows RPE hypertrophy with an adjacent RPE defect (green circle) at the site of lesions which are seen as hyperreflective spots in the infrared image (A) The location of the OCT section is shown as the green line and at the hyperreflective spot is shown within a green circle (C). The lesions appear as hypoautofluorescent areas in FAF (D) and hyperfluorescent areas in FA (E).

Figure 7

Decrease in the number of visible titration lesions in FA (a) and FAF (b) over time. Median values are plotted and IQRs are displayed as error bars. A Wilcoxon rank test was used to compare means of not normally distributed matched samples. * p < 0.05, ** p < 0.01, *** p < 0.001.

Figure 8

Decrease in area (µm²) irradiated with energy levels suitable for macular treatment (a) and visible whitening reaction (b) over time. Median values are plotted and IQRs are displayed as error bars. A Wilcoxon rank test was used to compare means of not normally distributed matched samples. * p < 0.05, ** p < 0.01, *** p < 0.001.