Comparison of different settings for yellow subthreshold laser treatment in diabetic macular edema

Abstract

Background: To assess the safety and efficacy of two subthreshold parameters (5 and 15% duty cycle (DC)) compared to standard ETDRS (early treatment of diabetic retinopathy study) continuous wave (CW) laser.

Methods: In this prospective randomized study, 30 eyes from 20 patients with non-center involving macular edema were randomized into 3 different groups: 5% DC, 15% DC and CW navigated modified ETDRS laser treatment. Titration in subthreshold groups was performed with 30% of the threshold power, decided with microsecond pulses. CW laser was titrated to a barely visible burn. All patients underwent microperimetry, thickness measurements and visual acuity examinations at baseline, 6 weeks and 12 weeks post treatment.

Results: At three months follow up, retinal sensitivity was significantly reduced in the CW group by - 2.2 dB whereas in both subthreshold groups, retinal sensitivity increased by 2.4 dB for 5% and 1.9 dB for 15% DC with no significant difference. Retinal volume (mm3) decreased in both subthreshold groups by 0.08 ± 0.3 and 0.12 ± 0.11 in 5 and 15% DC group respectively. Whereas the CW group showed volume increase of 0.55 ± 0.92 (p = 0.02 and 0.01 for 5 and 15% DC groups). Visual acuity remained stable in all 3 groups (- 0.7 letter in 5% DC; 2.11 letters in 15% DC and 0.88 in CW with no significant difference).

Conclusion: Subthreshold microsecond laser was shown to be safe and effective with both 5 and 15% DC as compared to conventional photocoagulation with ETDRS parameters. The 15% DC setting trended to achieve better anatomical, visual and functional outcomes.

Trial registration: Retrospectively registered ( NCT03571659 , 06/26/2018).

Keywords: Diabetic macular edema; Laser photocoagulation; Microperimetry; Micropulse; Microsecond; Subthreshold laser.

Conflict of interest statement

Ethics approval and consent to participate

Approval from ‘Institutional Review Board, L V Prasad Eye Institute, Hyderabad, India. The study was conducted in accordance with the tenets of the Declaration of Helsinki. Written informed consent was obtained from patients.

Consent for publication

Not applicable.

Competing interests

Jay Chhablani is a member of the editorial board.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1

Continuous wave laser photocoagulation: Color fundus photograph (a) shows signs of extrafoveal macular edema with few microaneurysms in early phase of fluorescein angiogrpahy (FA) (b) with late leakage in late phase (c). Microperimetry map (d) shows retinal sensitivity map at baseline. Spectral domain optical coherence tomography (SD-OCT) (e) shows normal foveal contour with minimal extrafoveal edema. Laser planning map (f) on NAVILAS® device with continuous wave with 60mw power, 100 msec pulse duration, and single burn width apart. At three months follow up FA early and late phases show decrease in overall leakage along with laser scars (g and h). Microperimetry shows decrease in retinal sensitivity (i). SD-OCT shows normal foveal contour with outer retinal damage due to laser scars

Fig. 2

Subthreshold 5% duty cycle laser photocoagulation: Color fundus photograph (a) shows signs of extrafoveal macular edema with few microaneurysms in early phase of fluorescein angiogrpahy (FA) (b) with late leakage in late phase (c). Microperimetry map (d) shows retinal sensitivity map at baseline. Spectral domain optical coherence tomography (SD-OCT) (e) shows normal foveal contour with minimal extrafoveal edema. Laser planning map (f) on NAVILAS® device with 5%DC with 400mw power, 100 msec pulse duration, and confluent burns. At three months follow up, FA early and late phases show almost same leakage, compared to baseline without any visibile laser scars (g and h). Microperimetry shows improvement in retinal sensitivity (i). SD-OCT shows normal foveal contour without any outer retinal damage

Fig. 3

Subthreshold 15% duty cycle laser photocoagulation: Color fundus photograph (a) shows signs of extrafoveal macular edema with few microaneurysms in early phase of fluorescein angiogrpahy (FA) (b) with late leakage in late phase (c). Microperimetry map (d) shows retinal sensitivity map at baseline. Spectral domain optical coherence tomography (SD-OCT) (e) shows normal foveal contour. Laser planning map (f) on NAVILAS® device with 15%DC with 240mw power, 100 msec pulse duration, and single burn width apart. At three months follow up, FA early and late phase shows almost same leakage, compared to baseline without any visibile laser scars (g and h). Microperimetry shows improvement in retinal sensitivity (i). SD-OCT shows normal foveal contour without any outer retinal damage

Fig. 4

Change in best-corrected visual acuity (BCVA) during study visits

Fig. 5

Change in central retinal thickness during study visits