Microstructural changes following inadvertent multi-spot laser photocoagulation of the fovea

Abstract

Dear Editor, Laser photocoagulation of the fovea is historically an accidental and sight-threatening complication rarely reported during routine treatment [1]. We present a case of inadvertent foveal laser photocoagulation during multi-spot Pascal macular grid laser. A 66-year-old woman presented with left branch retinal vein occlusion and non-resolving cystoid macular oedema (Fig. 1), and underwent macular laser treatment. Vision was 6/18, with an artificial fellow eye. The patient was comfortable during initial laser titration stages, using single-spot 10ms 100μm burns, (power 125mW;fluence 16 Joules/cm). Modified Pascal grid laser involved multispot arrays applied to the macula. During delivery of the first multi-spot array, the patient’s head moved suddenly away from the slit-lamp due to anxiety from the light flashes produced. Laser burns were inadvertently scattered across the foveal zone (Fig.1). Immediately postlaser, vision was 6/19. Routine fundus autofluorescence (AF) and OCT identified misdirected parafoveal burns, with a single burn overlying the anatomical fovea (Fig. 2). At day 3, vision was stable despite increased central retinal thickness (Fig. 1). Burns showed initial hyper-autofluorescence on serial AF, and the intraretinal hyper-reflectivity slowly resolved (Fig. 2) [2]. At 6 months, the anatomical foveal burn showed restoration of the inner and outer segment junction of the photoreceptors (Fig. 2). Vision was 6/9 and with barely-visible foveal burns (Fig. 1). Retrospective review of our laser logbook documented 3,932 Pascal laser procedures between 11 December 2006 and April 1 2011. Institutional Pascal auditing has not reported any operational or laser-related adverse events [3]. The prevalence of inadvertent foveal photocoagulation complication following Pascal is 0.025% (1/3,932) in our institution. The Pascal photocoagulator has safety mechanisms in place [4]. The inner row of Pascal spots is delivered in 132ms, theoretically below patients’ reaction time. Lowfluence 10–30ms pulse duration Pascal can minimize scarring [2, 5]. The foveal 10ms burns healed over time, with photoreceptor infilling and minimal retinal pigment epithelium damage [6]. After this case, we routinely advise patients pre-laser application about multi-spot Pascal light flashes. In borderline cases, single-spot laser strategies are recommended. Despite a potentially sight-threatening adverse event such as foveal photocoagulation, a pattern-spot laser system application of low fluence 10ms burns may not lead to long-term microstructural alterations on FD-OCT or visual complications. Funding support None