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Questioning photostasis

Published online by Cambridge University Press:  28 August 2013

ALEXANDER CUNEA
Affiliation:
Institute of Ophthalmology, University College London, UK
RANA BEGUM
Affiliation:
Institute of Ophthalmology, University College London, UK
DIETER REINISCH
Affiliation:
Institute of Ophthalmology, University College London, UK
GLEN JEFFERY*
Affiliation:
Institute of Ophthalmology, University College London, UK
*
*Address correspondence to: Glen Jeffery, Institute of Ophthalmology, University College London, Bath Street, London EC1V 9EL, UK. E-mail: [email protected]

Abstract

Photostasis is a phenomenon where the photoreceptor outer segment (OS) length and its rhodopsin content vary depending on environmental lighting. When light is reduced for extended periods, it is argued that OS lengthen and its rhodopsin concentration rises to increase photon capture in darker environment. Increases in OS length may occur because the retinal pigment epithelium (RPE) cells reduce OS consumption in prolonged darkness. But sample sizes in assessing changes in OS length have been small, and results highly varied with no statistical analysis ever offered. Further, animals used were often albinos, which have abnormal RPE cells. Here we keep pigmented and albino mice for 21 days in darkness and compare OS length with those in a normal 12:12 light/dark environment. We measured approximately 1300 OS but found no statistically significant difference in their lengths between light and dark groups in either pigmentation phenotype, although there was a small trend in the data favoring OS extension in the dark. Given that earlier studies were undertaken on limited samples with no statistical analysis, our data pose serious questions for the notion of mammalian photostasis in terms of significant OS plasticity.

Type
Brief Communication
Copyright
Copyright © Cambridge University Press 2013 

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