Commentary: Subthreshold micropulse yellow laser for central serous chorioretinopathy: Finding the right protocol

Central serous chorioretinopathy (CSCR) is an intriguing retinal condition with myriad of clinical presentations and outcomes. While most cases subside with near-normal recovery of vision, a proportion of cases run a chronic course with multiple episodes and suboptimal visual outcome. Fluorescein angiograph (FA)-based focal thermal laser photocoagulation to the leak has been the cornerstone of treatment of nonrevolving CSCR.[1] However, thermal laser photocoagulation is not suitable for treatment of subfoveal leak, for which photodynamic therapy with verteporfin has been the treatment of choice.[1,2] In view of ongoing unavailability of photodynamic therapy, the role of subthreshold micropulse laser in management of CSCR seems more pertinent than ever. It uses a grid pattern of laser spots to treat the FA-guided leakage point. Initial randomized controlled PLACE trial used subthreshold micropulse diode laser (810 nm) and compared it with reduced dose verteporfin photodynamic therapy in the management of CSCR. Compared to reduced dose verteporfin photodynamic therapy, which showed resolution of subretinal fluid in 67.2% eyes, micropulse diode laser had resolution of subretinal fluid in only 28.8% eyes.[3] However, there was no significant difference in visual acuity gains between these two treatment modalities.[3] Further, subthreshold micropulse yellow (577 nm) laser was compared with reduced dose verteporfin photodynamic therapy. This study by The Pan American Collaborative Retina Study Group showed significant visual acuity gains in eyes treated with yellow laser, compared to nonsignificant gains with photodynamic therapy.[4] A visual acuity gain of at least three lines or more was noted in 48.9% and 19% eyes with yellow laser and photodynamic therapy, respectively. It established subthreshold micropulse yellow laser as a safe and effective treatment for CSCR.

Many challenges still exist in adopting subthreshold laser as the treatment for CSCR. Lack of treatment endpoint in the form of visible retinal burn has been suggested as a reason for undertreatment and nonresponse to this treatment modality.[1] There are no standard parameters of subthreshold micropulse yellow laser for treatment of CSCR. Various studies have used duty cycles ranging from 5% to 15% with spot size of 100–200 mm and power of 90–1800 mW.[1] Hence, the present study is a step in the right direction as it attempts to compare two different duty cycles of yellow laser.[5] It has found similar visual acuity gains and central macular thickness reduction with 5% and 10% duty cycles of yellow laser. Both duty cycles were comparable in terms of complete resolution of CSCR too. The odds ratio of complete resolution of CSCR favored (2.25 times) the 10% duty cycle protocol. However, the small sample size makes these findings less robust to be able to replicable in clinical practice. The decision to have best corrected visual acuity of 20/30 or worse as the guideline for inclusion in the analysis has not been explained. The present study has established subthreshold micropulse yellow laser in the treatment of CSCR; additionally, it has provided some insight into the appropriate duty cycle. It should prompt further larger studies to validate the appropriate protocol of treatment of CSCR with subthreshold micropulse yellow laser in view of continued unavailability of verteporfin photodynamic therapy.