Anna Brouwer

Prolonged cone b-IT in relation to retinal layer analysis Introduction Uveitis is a relatively rare disease with a significant visual impact. The prevalence is estimated at 121 cases per 100.000 adults in the United States. However, uveitis causes a relatively large percentage of 10% of blindness in the working population. 1,2 Multiple treatment strategies are available with immunomodulating treatments, but still several complications can develop, including glaucoma, cystoid macula edema (CME), and retinal atrophy. 3,4 Recently we described a characteristic abnormality on the electroretinogram (ERG) in uveitis patients: a prolonged cone b-wave implicit time (cone b-IT). 5 This ERG abnormality was present in all anatomical subtypes of uveitis and correlated to the severity of the inflammation. In most cases a prolonged cone b-IT persisted even when the inflammation had become quiescent, indicating a possible permanent loss of retinal function. 6 We investigated a possible association between retinal function and retinal structure using automatic segmentation of the retinal layers on optical coherence tomography (OCT) images. Automatic segmentation is constantly improving, and associations between the thickness of retinal layers and clinical functional parameters have been described. For instance, in glaucoma and diabetic retinopathy a correlation was found between thinning of layer thickness and visual fields, and retinopathy stage, respectively. 7–10 We investigated possible differences in retinal layer thickness between non- uveitis eyes and uveitis eyes with and without a prolonged cone b-IT. Because the cone b-wave is mainly generated by theON andOFF bipolar cells, 11 we expected changes in thickness to occur in the retinal layers which correspond to the photoreceptor-bipolar cell synaps and the bipolar cells: the outer plexiform layer (OPL), inner nuclear layer (INL) and the inner plexiform layer (IPL). However, associations between the thickness of other retinal layers and the cone b-IT were investigated as well. Methods Patients We included 189 patients from a previously described cohort of 200 uveitis patients, who had an OCT on the same day as an ERG measurement and a clinical visit. 5,6 All patients were mentally competent, ≥ 18 years of age, and gave informed consent to participate. Patients were all treated at the University Medical Center Utrecht, a tertiary referral center for uveitis. Patients with uveitis associated with juvenile idiopathic 95 4