Going the distance with cyclodiode laser

The aim of glaucoma management is to effectively reduce intraocular pressure (IOP), in order to slow the rate of visual field loss and prevent progression to blindness. When IOP cannot be sufficiently reduced with medication and/or selective laser trabeculoplasty (SLT) and the visual potential is poor, then incisional surgery may not be desirable. However, without intervention, elevated IOP may lead to a painful eye from endothelial failure and bullous keratopathy. An effective, non-penetrating method of lowering IOP is therefore needed. Cyclodestructive procedures which were utilised in the management of refractory glaucoma have been available for the past 100 years. The initial procedures described were those of cyclectomy and cyclodiathermy. These gained favour during the first half of the last century; however, audits found very low efficacy with an unacceptable number of complications. Cyclocryotherapy was described in 1950 and demonstrated a much better efficacy; however, adverse outcomes were still frequent. Transscleral cyclophotocoagulation was first described in 1961 using a xenon arc laser and then later, using ruby and Neodymium YAG laser. However, since 1992, the transscleral cyclodiode laser has become the most commonly performed cyclodestructive procedure and is generally reserved for cases of end-stage glaucoma with poor visual potential. Being performed with a specially designed probe head that targets the melanin in the ciliary processes and using a standard protocol of 1500– 2000 mW of laser power and 1500–2000 ms of laser burn duration, it has been found to have an acceptable combination of IOP lowering and low adverse event outcomes. Having the advantage of being a non-penetrating procedure, it is well suited for those for whom the primary goal is comfort as opposed to function. Its outcomes have been assessed on several occasions; however, published reports have never followed patients for more than 36 months.7–10 Scott et al. have presented a paper, which documented the outcomes of cyclodiode laser over a much longer time period of 5 years. Their cohort had cyclodiode laser performed by a single surgeon using a standardised technique reflective of the aforementioned protocols and then followed 6–12 monthly for at least 5 years. They demonstrated that the procedure remained successful in almost 80% of cases beyond 5 years, with only about 25% requiring re-treatment and IOP reduction being approximately 7% greater for every 10 decades of age. They were able to estimate the rate of complications, with hypotony developing in about 6% of cases, phthisis occurring in 4% and vision loss occurring in 69%, with those most likely to suffer these adverse outcomes being those who were elderly or who had neovascular glaucoma. The authors were also able to demonstrate that cyclodiode laser had the greatest IOP-lowering effect for those with the highest pre-treatment IOP and who were on the greatest number of medications. When medications and SLT have failed and incisional surgery is not clinically indicated, a painful, blind eye might be the inevitable result. This paper confirms that cyclodiode laser is an effective method of managing IOP, with its effects lasting more than 5 years in the majority of cases. It may be particularly effective in the elderly when surgery is not desirable and preservation of vision is not the primary necessary outcome. Although titration of the procedure can be difficult, with one-quarter of patients requiring retreatment and almost 10% suffering from phthisis or hypotony, this needs to be balanced against the ability of the procedure to avert the need for glaucoma drainage surgery.