The use of optical coherence tomography angiography to measure changes in iris vasculature after strabismus surgery.

INTRODUCTION: Anterior segment ischemia (ASI) is a rare but potentially sight-threatening complication of strabismus surgery. Preoperative imaging of the iris vasculature may be appropriate in patients at high risk of ASI. In clinical practice, this is currently done through invasive fluoresceine or indocyanine green (ICG) angiography and in study context through laser speckle contrast imaging. The purpose of this study is to investigate the use of noninvasive optical coherence tomography angiography (OCTA) as a screening tool for ASI in strabismus surgery. METHODS: A prospective interventional trial was conducted from September until November 2021 at the Leuven University Hospitals. Patients scheduled for strabismus surgery to one or more rectus muscles underwent OCTA preoperatively and at day two postoperatively. The vascular density was calculated for all images with sufficient quality. Information on risk factors for ASI was collected. A two-sided t-test was used for pairwise comparison pre- and postoperatively. Filling defects were qualitatively assessed. RESULTS: Eighteen patients were included. In only seven muscles of five patients, images of sufficient quality on both image acquisition moments were suitable for statistical analysis. The mean age of these patients was 45.2 years and 40% were women. A mean vascular density of 53,099% preoperatively and a mean density of 50,782% postoperatively with a mean decrease of 2.316% (p = .318, 95% confidence interval [-2.886; 7.516]) was found. No filling defects were identified. DISCUSSION: The small final number of images contributing to statistical analysis shows that current application of the OCTA technique is hampered by poor image quality and poor repeatability. We identified difficulties in the image acquisition process and variable pupil size due to iris muscle contractions as the two main reasons. We believe that adjustments in the OCTA software such as pupil tracking and tracking of iris vasculature can largely overcome these limitations. Furthermore, there is a need for a normative database to allow good quantitative comparison and risk stratification. We conclude that OCTA could be suitable for screening in prevention of ASI with both qualitative and quantitative analysis if adjustments are made.

Association between near viewing and acute acquired esotropia in children during tablet and smartphone use.

We investigated a possible association between the acute onset of esotropia and tablet or smartphone use in children. We characterized the clinical aspects of esotropia associated with tablet or smartphone use. The medical records of 10 children aged between 5 and 15 years old with presumably tablet or smartphone associated esotropia were reviewed regarding orthoptic examination and cycloplegic refraction. Legal guardians of the children were asked to fill in a questionnaire regarding tablet and smartphone use of their child. This questionnaire was also conducted in a control group of age-matched children. The results of this questionnaire were compared to search for possible determinants of tablet or smartphone associated esotropia. All 10 patients presented with a comitant esotropia ranging from 8 to 45 prism diopters with no significant difference between near and far. The mean age of onset was 9.8 years. Cycloplegic refraction showed a mild hyperopia in eight patients, a mild myopia in one patient and emmetropia in the other patient. All patients had near full refractive correction at the onset of esotropia. Diplopia was reduced after visual hygiene recommendations, however in six patients, strabismus surgery was needed. The working distance was significantly shorter in the 10 cases compared to the controls. In children with acute acquired esotropia, we found a statistically significant association with a smaller working distance during tablet or smartphone use compared to age-matched controls. We hypothesize that intensive near viewing can be a precipitating factor in this type of esotropia.

Ocular Neuromyotonia: Case Reports and Literature Review.

Ocular neuromyotonia (ONM) is a rare eye movement disorder, presenting as a paroxysmal involuntary spasm of one or more extra-ocular muscles, that can persist for a few seconds up to several minutes. The phenomenon is caused by the contraction of an extra-ocular muscle, excited by a damaged nerve, which leads to delayed muscle relaxation. We present eight patients with this rare condition together with an overview of the literature on all published ONM cases. One of the presented cases is possibly secondary to hypovitaminosis D. This association has not been reported previously in the literature. A possible underlying mechanism is given.