The ophthalmic literature can help inform clinical practitioners of rare but concerning outcomes and findings. In the March issue of JAMA Ophthalmology, Vajaranant and colleagues described the finding of diffuse retinal hemorrhages after successful intraocular pressure–lowering surgery. The case describes a glaucoma patient with very high intraocular pressures prior to the surgery, and low to normal intraocular pressures following the uncomplicated surgery. The vision was excellent prior to the surgery, and dropped to hand motions following this otherwise successful surgery. On fundus examination, diffuse intraretinal hemorrhages are seen throughout the retina, explaining the reduction in vision. The question then arises: what happened? Is this a coincidental development of a central retinal vein occlusion on the day of the glaucoma surgery? What are the odds of that? Fortunately, this is not a classic central retinal vein occlusion, but rather a condition known as ocular decompression retinopathy. Ocular decompression retinopathy occurs in just the scenario described—a very high intraocular pressure that falls to a low level after surgery. A variety of mechanisms have been proposed that relate to autoregulation, changes in the position of the lamina cribrosa, and scleral compliance, all explained in the article. Flourescein angiography may appear similar to a central retinal vein occlusion. Interestingly, there is an association between retinal vein occlusions and glaucoma. In the Ocular Hypertension Treatment Study, intraocular pressure lowering slightly reduced the occurrence of retinal vein occlusions in the group that received treatment.
Perhaps the most positive and reassuring aspect of ocular decompression retinopathy is the fact that the natural history of this condition is for complete resolution to occur. The average time to resolution is 13 weeks (although it may last up to 4 years), and some patients may actually be asymptomatic, although temporary vision loss can occur. As a glaucoma surgeon who has encountered this phenomenon on a handful of patients, it is a startling finding. The dramatic reduction in visual acuity is a cause of great concern to the patient, and knowing that this is likely to be a self-limiting condition is very important. In my experience, offering reassurance to the patient that this is a known entity and that it tends to improve makes all the difference. The main risk factor observed for this finding is a high baseline intraocular pressure, so reducing the intraocular pressure as much as possible before the surgery is advisable, although often not possible because glaucoma surgery is usually being employed when all medical means of pressure-lowering have been exhausted. It is important to note that the condition can occur bilaterally, so a patient who experiences the completion in one eye should be carefully managed to try to reduce the likelihood of this happening in the fellow eye. Preoperative mannitol can be employed for this purpose in high-risk cases.
Performing glaucoma surgery on an eye that is facing glaucoma-related blindness represents an extraordinary measure. We are altering the physiology of the eye significantly. It is not entirely surprising that the autoregulation of the eye may be thrown off, and that fluid may shift from one cavity to another as the eye adjusts to its new, lower intraocular pressure. Fortunately, in the case of ocular decompression retinopathy, knowing the natural history of the condition will allow the treating physician to reassure the patient and weather the storm, hopefully toward a successful resolution. The article Vajaranant et al provides helpful information to those of us to perform glaucoma surgery regularly.