Commentary: Advanced Coats' disease - Is it worth chasing the goal of globe salvage?

Coats’ disease is an idiopathic retinal telangiectasia with intraretinal and/or subretinal exudation.[1] It is usually unilateral and has a male predilection, though bilateral cases and female affliction are also known.[2] Coats’ can manifest as asymptomatic retinal telangiectasia identified on examination and may progress to the advanced stage having exudation causing retinal detachment, leading to subsequent neovascular glaucoma (NVG) and phthisis. As per the classification given by Shields et al.,[3] advanced Coats’ disease primarily consists of eyes with stage 3B and stage 4 disease. Given the largely unilateral presentation and the relatively young age of presentation, the majority of the cases in large series present with advanced disease.[4] These eyes not only have lower vision at presentation but also have a poorer visual outcome despite intervention.

One may argue that given the other eye is normal in such cases, chasing the eyes with advanced disease and low visual potential may not be worthwhile. However, this is not the case. There is something worse in store if eyes with advanced Coats’ disease are not treated—it is the end stage Coats’ disease also known as stage 5 in the Shields classification. This stage primarily consists of a painful blind eye secondary to neovascular glaucoma and ultimately pthisis bulbi. Both these scenarios have significant morbidity associated with them both for the child socially and mentally as well as for the parents. Silodor et al.[5] demonstrated in 1988 the effectiveness of surgical intervention in eyes with stage 3B Coats’ disease versus observation alone. In their cohort of 13 eyes, seven underwent surgical drainage of subretinal fluid with cryotherapy, and all these seven eyes were anatomically salvaged, with none developing NVG at a mean follow-up of 28 months. In contrast, almost 67% of the eyes under observation went on to develop a blind, painful eye secondary to NVG and had to be ultimately enucleated.

That being said, caution needs to be given against indiscriminate use of surgery in any eye of suspected advanced Coats’ disease. While approaching a case of suspected advanced Coats’ disease, one must have three objectives in mind. First, getting the diagnosis correct. Given the age group we are dealing with, retinoblastoma forms a major differential diagnosis in cases with advanced Coats’ disease and must be ruled out with as much certainty as possible before proceeding with any surgical intervention. A combination of one’s clinical acumen and radiological findings must be used to reach that certainty. Second, when deciding upon the surgical procedure, always remember the dictum that is true for most pediatric retinal procedures: “less is more.” Simple external drainage of subretinal fluid with laser/cryotherapy to the abnormal vascular will suffice for most cases. Some cases with a shallow fluid at presentation may not need drainage either. It has been shown that anatomical outcomes do not improve and are instead adversely affected upon increasing the complexity of the vitreous surgery.[6] Lastly, one must be ready for a long-term follow-up and repeated interventions. Recurrences are the rule rather than an exception in Coats’ disease and are more likely to happen in cases that present with advanced disease.[1] Taking these three things in mind, the goal of globe salvage in cases with advanced Coats’ disease can be achieved in the majority of the cases.