Defocused large spot laser delivery in retinopathy of prematurity

Dear Editor, Laser indirect ophthalmoscopy (LIO) is the most common treatment for managing retinopathy of prematurity (ROP). Laser of large avascular areas (e.g. zone I/zone II posterior) in bigger uncooperative babies under topical anesthesia poses unique challenges as the large number of spots needed leads to prolonged procedure time, often systemically destabilizing the baby and fatiguing the surgeon. There were reported significant advantages of performing large spot size (LSS) laser delivery (used for transpupillary thermotherapy) in ROP, which significantly reduced total treatment duration in zone I by 32% and zone II by 63.4%.[1] LSS laser in ROP enabled faster procedure, lesser total duration of pain, and similar regression profile, without additional myopia.[1] Balasubramaniam et al.[2] have shown the ability to deliver spots with increased uniformity and reduced fluence using LSS laser in a variety of pediatric retinal conditions including ROP. We describe a defocused large spot (DLS) technique that defocuses the laser beam spot to achieve a larger laser spot delivery (LIO headset - Keeler Ltd USA; 20D lens - Volk USA; 532 nm Laser console - Nidek USA), without the need for a dedicated LSS laser delivery system [Fig. 1a]. In the LIO headset, by rotating the knob from the neutral working distance (WD) position toward the extreme long end [Fig. 1b], the aiming beam becomes defocused, resulting in visibly larger spots on the retinal surface. It is notable that this needs 20–40% more laser power with similar pulse duration for effective spot delivery (as spot is not sharply focused), but it does enable faster treatment as the larger spots can cover a larger area of avascular retina rapidly. The larger spots have fuzzy diffuse borders, exhibit blooming effect over time, and allow greater interspot spacing, thereby helping to fill larger areas with lesser spots. However, skip areas may occur between the large spots and must be actively looked for at the end of procedure and filled to avoid the need for laser augmentation later.Figure 1: (a) Fundus picture of right eye with persistent avascular retina demonstrating large laser spots created by DLS laser technique (double arrows) vs conventional laser spots (single arrow). (b) Adjusting the LIO headset knob from neutral WD setting (top) to long end (bottom) to defocus the laser beam (white arrows)However, the exact degree of defocus, resultant spot size, and additional power needed cannot be precisely quantified as they depend on several factors, including working distance, optics of the eye, and the surgeon’s technique. It is notable that some laser LIO headsets may not have a WD adjustment knob. There is a possibility of less homogeneous energy delivery, greater pain from additional power used, risk of overtreatment, and so this technique should be avoided by beginners. The improved time efficiency outweighs these concerns, and in our experience, no adverse events occurred using this technique, with no extra sedation needed. We believe the DLS technique is simple, reproducible, and easy to adopt and will enable experienced surgeons to perform faster laser therapy in ROP eyes and other retinal situations where larger retinal areas need to be lasered, thereby reducing duration of pain and enhancing surgeon comfort. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.