Retinal anatomical changes may be observed in patients with bipolar disorder (BD), according to a study published in Photodiagnosis and Photodynamic Therapy. These changes include choroidal thickness, area, and vascularity index alterations and may indicate neuronal degeneration in the retina and choroid, the report suggests.
Investigators included patients with BD (n=39; mean age, 36.15 years; 29 women) and age- and sex-matched control group participants (n=36; mean age, 33.33 years; 28 women) in the prospective, observational, cross-sectional study. All study participants underwent spectral domain-optical coherence tomography (SD-OCT) assessment during which researchers measured total choroidal area, choroidal vascularity index, and choroidal thickness at 5 locations, which included the subfoveal area, areas 500 and 1500 μm nasal to the fovea, and areas 500 and 1500 μm temporal to the fovea.
Patients with BD had significantly thinner mean central macular (241.54 vs 267.61 μm; P =.0001) and ganglion cell layer thicknesses (15.68 vs 33.97 μm; P =.0001) compared with control group participants. Other retinal anatomical changes included a smaller mean total choroidal (1.17 vs 1.61 mm2; P =.0001), luminal (0.80 vs 1.10 mm2; P =.0001), and stromal area (mean, 0.37 vs 0.50 mm2; P =.0001) for participants with BP compared with control group individuals.
Choroidal thickness was thinner in all 5 areas measured by SD-OCT for patients with BD compared with control group participants (500 μm temporal to the fovea: 288.56 vs 371.75 μm; 1500 μm temporal to the fovea: 273.79 vs 359.08 μm; subfoveal: 296.21 vs 382.86 μm; 500 μm nasal to the fovea: 287.74 vs 369.78; 1500 μm nasal to the fovea: 252.46 vs 317.03 μm; P =.0001 for all).
The retinal anatomical changes did not include alterations in mean retinal nerve fiber layer thickness or choroidal vascularity index, evidenced by similar measurements between the 2 cohorts (P =.532 and P =.766, respectively).
“Significant thinning of the [ganglion cell complex] in patients with BD may reflect the condition of the thalamus, which has been demonstrated to be the most damaged structure in BD,” according to the researchers. “We believe that neurodegeneration in bipolar illness begins in the [ganglion cell layer], which is responsible for the formation of neuronal cell bodies, and then gradually advances to axonal degeneration.”
Study limitations include a small sample size and failure to assess retinal anatomical changes among patients with less stable BD.
Torun IM, Dikmen NT, Saka NT, Sonmez M. Choroidal structural alterations and choroidal vascularity index in bipolar disorder patients. Photodiagnosis Photodyn Ther. Published online March 21, 2023. doi:10.1016/j.pdpdt.2023.103518