Safety of Pharmacologic Dilation: Acute Angle Closure Incidence in a Los Angeles County-Wide Safety Net Teleretinal Screening Program

ImportancePharmacologic dilation is vital for eye disease screening but is often avoided due to concerns about triggering acute angle closure (AAC), a sight-threatening ophthalmic emergency. ObjectiveTo assess AAC incidence after dilation and validate the use of International Classification of Diseases (ICD) codes for identifying AAC cases. DesignRetrospective cohort study SettingPrimary care-based teleretinal diabetic retinopathy screening (TDRS) program ParticipantsEligible participants were Los Angeles County (LAC) Department of Health Services (DHS) patients who underwent teleretinal screening by dilated fundus photography between August 23, 2013, and March 1, 2024. Potential AAC cases were identified using ICD codes for angle closure, including acute angle closure glaucoma (AACG), primary angle closure glaucoma (PACG), and anatomical narrow angle (ANA), within three months of dilation. All urgent care, emergency department, and eye clinic encounters within the next calendar day after TDRS and encounters with Current Procedural Terminology (CPT) codes for iridectomy/iridotomy or lens extraction within 14 calendar days of TDRS were also identified. Manual chart review was conducted to verify AAC cases and extract clinical information. ExposuresDilation with 1.0% or 0.5% tropicamide. Main Outcomes and MeasuresCumulative incidence of AAC after dilation. Results84,008 patients received 168,796 dilations with a mean of 2.01 {+/-} 1.50 (mean {+/-} standard deviation) dilations per patient. 55.1% were female. Mean age was 55.4 {+/-} 10.7 (mean {+/-} standard deviation) years. The cohort was 67.7% Hispanic, 8.2% Black, 6.3% Asian, 4.1% White, and 2.4% Other. Manual chart review confirmed four AAC cases after dilation: 3 coded as AACG and 1 as ANA. The AAC risk was 2.4 (95% CI 0.05-4.69) per 100,000 dilations (0.0024%) or 4.8 (95% CI 0.10-9.43) per 100,000 patients (0.0048%). All four cases were female, had narrow angles in the non-presenting eye on gonioscopy, and presented within one day with AAC symptoms, including eye pain and blurry vision. Conclusions and RelevanceAAC risk was less than 1 in 40,000 per dilation in a high-volume TDRS program serving a diverse, safety net population, supporting the overall safety of dilation in this setting. Further discussion about AAC risk as a contraindication to dilation is warranted.