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Editors Selection IGR 18-2

Surgical treatment: Postoperative complications

Comment by Syril Dorairaj & Abayomi Fabunmi on:

52391 Risk Factors for Decompression Retinopathy After Glaucoma Surgery, Jung KI; Lim SA; Lopilly Park HY et al., Journal of Glaucoma, 2014; 23: 638-643

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The earliest reports of decompression retinopathy (DR) in literature date back to 1965 by Paufique et al., and were subsequently characterized and named by Fechtner et al. in 1992. Since that time, only case reports and case series have been documented. Clarification of potential risk factors for DR will invariably guide development of future projects and help characterize this postoperative complication. This study conducted by Jung et al., is the first cohort study that provides data on potential risk factors and incidence rates of DR. Based on the fundoscopic description of retinal hemorrhages within the first two postoperative days, authors retrospectively reviewed the charts of 769 patients who underwent trabeculectomy or Ahmed implantation. Risk factors evaluated include age, sex, glaucoma type, previous intraocular surgery, preoperative and postoperative intraocular pressure (IOP), refractive error, axial length, anesthesia, and systemic risk factors such as history of diabetes, hypertension, medication, and laboratory parameters, including hemoglobin, hematocrit, platelet, pro-thrombin time, and activated partial thromboplastin time were evaluated. Authors conclude that high pre-operative IOP and hematologic abnormalities have a higher risk for developing DR. Considering the novel intentions of this study, it does provide insight into the potential risk factors associated with DR after glaucoma surgeries.

The authors excluded 81 patients due to recorded histories of neovascular glaucoma, severe media opacities or other retinal diseases. The authors' exclusion criteria were an attempt to exclude pathologies that may confound the detection of a retinal hemorrhage. However, these exclusions weaken the study's evaluation of diabetes and other conditions associated with VEGF and fibrovascular wall integrity. An additional area of concern is the definitions used for DR in the selection process. The authors define DR as retinal hemorrhage, determined by the postoperative fundoscopic description, within the first two postoperative days. This method of selection would eliminate non-healthy retina resulting in a significant bias that weakens the reported findings. An approach that compared the patients' preoperative and postoperative fundoscopic exam would allow for the inclusion of more cases, despite retinal abnormalities. The narrow selection process significantly hinders the reader's confidence in the authors' ability to apply retrospective cohort data to external populations. Additionally, the study's small sample size poses an issue on the study's power to identify associated risk factors.

This study represents a milestone in the development of future studies aimed at elucidating additional risk factors, mechanisms, and preventative measures for DR. Echoed in case reports since 1965 and supported by the findings of this study, high preoperative IOP appears to increase the risk of developing DR. The second significant finding reported by the authors interestingly establishes hemoglobin as a risk factor for the development of DR. As described in the study, hemoglobin-mediated scavenging of nitrous oxide (NO) may predispose patients with lower than normal concentrations of NO to DR. The authors postulate that hemoglobin scavenging of NO, a potent vasodilator, is suppressed in individuals with lower concentrations of hemoglobin. This baseline vasodilation may predispose to DR when combined with acute changes in IOP and other unknown factors. These two findings merit further evaluation in future DR related studies. Overall, Jung et al. Have provided the first observational study addressing DR, and even its shortcomings provide useful information and direction for future studies on DR.

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