Association of Change in Iris Vessel Density in Optical Coherence Tomography Angiography With Anterior Segment Ischemia After Strabismus Surgery

Abstract

<p class="first" id="d9080105e299">This case series study analyzes the use of iris optic coherence tomography angiography (OCT-A) for patients undergoing strabismus surgery at risk for anterior segment ischemia. </p><div class="section"> <a class="named-anchor" id="ab-eoi180055-1"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e305">Question</h5> <p id="d9080105e307">Is optical coherence tomography angiography useful in patients undergoing strabismus surgery to determine whether anterior segment ischemia is present? </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-2"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e310">Findings</h5> <p id="d9080105e312">In this case series study of 9 participants, the mean vessel density for all quadrants had a relatively small decrease from preoperative to postoperative. Optical coherence tomography angiography detected filling defects in the quadrant adjacent to the operated muscle in 1 patient. </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-3"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e315">Meaning</h5> <p id="d9080105e317">The clinical relevance of these findings is unknown, and given the small sample size, further research to determine its use in clinical practice seems warranted. </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-4"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e321">Importance</h5> <p id="d9080105e323">Anterior segment ischemia (ASI) is a rare but potentially serious complication of strabismus surgery. Indocyanine green angiography and fluorescein angiography have been used to reveal iris-filling defects for clinicians considering a patient’s risk of ASI. However, both are limited by invasive and time-consuming nature and potential adverse effects. Recently, optic coherence tomography angiography (OCT-A) has been introduced and used to image iris vasculature in individuals without abnormalities. </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-5"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e326">Objective</h5> <p id="d9080105e328">To determine the use of iris OCT-A for patients undergoing strabismus surgery and who are at risk for ASI. </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-6"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e331">Design, Setting, and Participants</h5> <p id="d9080105e333">This prospective case series study took place in an academic center. Adults undergoing strabismus surgery on at least 1 vertical muscle were prospectively recruited. The study took place from June to November 2017, and analysis began in January 2018. </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-7"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e336">Interventions</h5> <p id="d9080105e338">Indocyanine green angiography and OCT-A of the iris preoperatively and 1 day postoperatively.</p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-8"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e341">Main Outcomes and Measures</h5> <p id="d9080105e343">A masked examiner evaluated all images and determined whether any filling defects were present qualitatively (lack of perfusion) and quantitatively (for OCT-A using internal software to calculate vessel density). </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-9"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e346">Results</h5> <p id="d9080105e348">Ten eyes of 9 individuals (mean [SD] age, 63 [11] years) were included. Two individuals (22.2%) identified as Hispanic, and 7 (77.8%) identified as white. There were 6 women (66.7%). The mean preoperative vessel density (percentage of the area occupied by vessels) averaged for all quadrants decreased from 57% preoperatively to 55% postoperatively (mean difference, 2%; 95% CI, 0.4%-4.2%; <i>P</i> = .05). When comparing quadrants adjacent to operated muscles, the mean vessel density decreased from 56% to 53% (mean difference, 2.6%; 95% CI, 0.17%-4.8%; <i>P</i> = .02). In addition, OCT-A detected vascular filling defects in the quadrant adjacent to the operated muscle on the patients in whom they were present (n = 1, inferior rectus recession). </p> </div><div class="section"> <a class="named-anchor" id="ab-eoi180055-10"> <!-- named anchor --> </a> <h5 class="section-title" id="d9080105e357">Conclusions and Relevance</h5> <p id="d9080105e359">In this preliminary study, OCT-A determined iris vessel filling defects when present. In addition, OCT-A gives qualitative vessel density values that can be compared preoperatively and postoperatively although the clinical relevance of small differences is not known. While only 10 eyes were evaluated, and as such generalizability of these findings cannot be determined, the results suggest that OCT-A may be a useful tool in the evaluation of patients undergoing strabismus surgery to determine whether a patient is at risk to develop ASI. </p> </div>