Effects of hereditary retinal degeneration due to a CEP290 mutation on the feline pupillary light reflex.
OBJECTIVE
To understand how progressive rod cone degeneration due to a mutation in CEP290 affects the pupillary light reflex (PLR) in domestic cats.


METHODS
Domestic cats identified as either normal wildtype (WT; n = 6), or homozygous for the rdAc mutation in CEP290 and having early stage retinal degeneration (stage 2, S2; n = 4), or advanced retinal degeneration (S4; n = 6).


METHODS
The effect of light on pupil size was measured over a series of 10-s pulses of white and chromatic light in cats lightly sedated with medetomidine.


RESULTS
In WT cats, the PLR was characterized by a pronounced initial constriction that rapidly re-dilated during the stimulus (pupil escape), to a stable or sustained constriction. There was then a marked constriction at stimulus offset. Each component of the PLR was retained in affected cats, but with progressively reduced irradiance sensitivity from early to advanced retinal disease.


CONCLUSIONS
The PLR of cats had multiple phases, with a remarkably high-amplitude 'paradoxical' off-constriction even in the absence of retinal disease. In rdAc cats, reduced irradiance sensitivity was consistent with progressive loss of rod and cone function. Based on previously characterized retinal pathology, this suggests the visual streak of the retina has a proportionally large contribution to PLR input. These findings support the hypothesis that the efficacy of planned therapeutic trials can be determined by careful evaluation of the PLR in cats.
Thompson
Stewart
S
Howard Hughes Medical Institute and Department of Ophthalmology and Visual Sciences, The University of Iowa, Iowa City, IA 52242, USA.
Whiting
Rebecca E H
RE
Kardon
Randy H
RH
Stone
Edwin M
EM
Narfström
Kristina
K
D000818:Animals; D002371:Cat Diseases / Q000235:genetics* / Q000503:physiopathology; D002415:Cats; D005820:Genetic Testing; D009154:Mutation; D012025:Reflex, Pupillary / Q000235:genetics* / Q000502:physiology; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology / Q000662:veterinary*