Limbus-Based External Reference Coagulation in Transscleral Diode Laser Photocoagulation for Threshold Retinopathy of Prematurity—Reply

In reply

Dr Arnold reported limbal reference cryotherapy for the treatment of acute ROP to obviate the the need for conjunctival incisions.¹ He proposes the limbus-based external reference method for transscleral diode laser coagulation in ROP, a procedure we have recently described.²

Limbal reference cryocoagulation has several disadvantages. The major disadvantages are the loss of direct visibility of conventional cryotherapy and the lack of ophthalmoscopic control when placing the coagulation spot. For that reason Dr Arnold noticed that the vascular ridge of acute ROP was unintentionally treated in his study.¹ Skip areas of untreated retina and overtreatment by treating the same retinal area twice or by overlapping coagulation spots cannot be avoided if there is no ophthalmoscopic control. Dr Arnold did not comment on these problems in the eyes he treated with limbal reference cryotherapy.¹ Inadvertent treatment of the ridge, skip areas, and overtreatment in eyes with ROP will increase the risk of therapy failure and of an unfavorable outcome. Additionally, treatment of ROP using the limbus-based external reference without conjunctival incisions does not allow coagulation of the far-posterior avascular retina in very immature eyes [eg, zone I disease³] as shown in the figures in Dr Arnold's article.¹ Thus, Dr Arnold had to use additional transpupillar diode laser coagulation in a case of posterior ROP.¹