Birdshot Retinochoroiditis Incidence and Clinical Presentations in UK Determined

A nationwide survey among UK-based clinicians identified 37 confirmed cases of birdshot retinochoroiditis (BSRC) between May 2017 and June 2019, and discussed common clinical presentations and treatment regimens, according to a study published in Eye.

Investigators sourced study data from the British Ophthalmological Surveillance Unit, a monthly prospective reporting system established in 1997, and evaluated incidence, presenting characteristics, and treatments among patients with BSRC. A total of 26 ophthalmologists (14 uveitis specialists) provided the study data and were asked to complete a 12-month follow-up questionnaire. 

Overall, 37 cases were included in this analysis — 23 had both baseline and follow-up data. The incidence rate of BSRC was 0.035 cases per 100,000 person-years. Median patient age was 46 years (range, 18-74 years), patients were primarily women (78%), and a majority were positive for major histocompatibility complex, class I, A (HLA-A)*29 (97.3%).

The most common presenting symptoms included floaters (72.9%), poor vision (60.8%), photopsia (32.4%), and nyctalopia (13.5%). Most patients presented with functional abnormalities of electroretinography (82%) and some with visual field (47%) or color vision (11%) abnormalities. Common clinical signs included optic disc swelling (24.3%) or pallor (8.1%) and cystoid macular edema (21.6%).

Visual acuity at presentation was significantly correlated with age (r², 0.44; P =.007) but not duration of symptoms. Stratified by presenting symptoms, those with cystoid macular edema had significantly better visual acuity compared with those without cystoid macular edema (0.097 vs 0.32 logarithm of the minimum angle of resolution [logMAR]; P =.007).

The most common treatment strategy was steroids with immunomodulatory therapy (IMT; 41%), followed by topical treatments (18%), IMT alone (14%), steroids alone (11%), intravitreal treatment (9%), and periocular treatment (7%).

According to the report, treatment regimens often changed from baseline to 1-year follow-up among patients with both baseline and follow-up data. Clinicians administered more intravitreal treatment (13% vs 32%) or IMT alone (19% vs 25%), while providing less steroids plus IMT (39% vs 32%), topical treatments (19% vs 7%), and periocular treatments (7% vs 0%).

“BSRC is a rare progressive posterior uveitis with the potential for significant visual morbidity,” according to the researchers. “This study confirms the pre-existing body of knowledge related to BSCR, and aims to educate ophthalmologists on the difficulty in timely diagnosis of BSCR, the need for comprehensive functional testing and the importance of steroid-sparing treatment.”

Study limitations include a small sample size and the potential for recall bias.