Ocular manipulation reduces both ipsilateral and contralateral electroretinograms

Purpose: To determine the electroretinogram (ERG) changes in eyes manipulated in the course of local ablative therapy (transpupil thermotherapy (TTT), cryotherapy or both) or scleral depression and in un-manipulated fellow, healthy eyes. Methods: This prospective observational report summarizes 73 ERG studies in 42 patients with retinoblastoma; a study consisted of ERGs of one or both eyes (if present) followed by ocular manipulation (scleral depression, cryotherapy, transpupillary thermotherapy, pressure applied to orbital implant in an anophthalmic socket, or a 5- or 10-min delay without mechanical manipulation) followed by a repeat of the ERGs. Each patient was studied with only a single manipulation modality on any given date: 23 patients were studied only once, and 19 patients were included in more than one study occasion. Results: Following local ablative treatment of patients with unilateral retinoblastoma, the photopic response decreased significantly in both the treated eye and the untouched fellow, healthy eye. Following scleral depression of the diseased eye, the photopic response immediately decreased in the diseased eye by a mean of 16 μV (21 %, p =.006) and, in the fellow, healthy eye by 40 μV (23 %, p =.0005). Following scleral depression of the fellow, healthy eye, the photopic response immediately decreased by a mean of 11 μV (4 %, p =.37) in the fellow, healthy eye, and by 16 μV (28 %, p =.01) in the diseased eye. Conclusions: Following physical ocular manipulation, the amplitude of the photopic response decreased in the manipulated, but also the untouched healthy, fellow eyes. These findings may account for some of the variation in clinical ERG recordings, particularly that observed following ocular manipulation by TTT, laser or even scleral depression.