Robert J. Casson, Glyn Chidlow, WengOnn Chan, John Wood

Purpose: In humans, short-wavelength cones (S-cones) are more susceptible to damage from retinal detachment than medium and long-wavelength cones (M/L-cones). We investigated the temporal profile of cone loss in a rat model of retinal detachment to determine if it modelled the human pathological profile.

Methods: Retinal detachments were induced in Sprague- Dawley rats and the eyes underwent spectral domain optical coherence tomography and were processed at various time points from 1 day to four weeks as follows: Retinal wholemount immunohistochemistry (n = 31); qPCR: (n = 22); Transverse section immunohistochemistry (n = 52).

Results: S-cones displayed a striking vulnerability to retinal detachment. The S-opsin messenger ribonucleic acid
level in the detached portion of the retina was reduced to < 20% of the level in the intact retina by 1 day after surgery and was significantly lower than the M/L-opsin mRNA level at all time points. Loss of S-opsin+ immunolabelling was apparent earlier than loss of M/L-opsin+ immunolabelling and the S-cones were affected to a greater extent than M/L-opsin+ cones throughout the duration of experimental detachment. The loss of S-cone+ immunolabelling encompassed both a reduction in the overall number of segments as well as a reduction is individual segment size. The acute susceptibility of S-cones to separation from the RPE/choriocapillaris was best illusrated by visualisation of the boundary of the intact and detached portions of the retina, which was technically feasible in both wholemounts and retinal cross-sections. Conclusions: S-cones are particularly affected by retinal detachment in a rat model which mimics the human situation.