ABSTRACT
Janis T. Eells,a Sandeep Gopalakrishnan,b Michele M. Salzman,c
Krisztina Valter,d Jan Provis,d Ricardo Natoli,d John Mitrofanis,e
The retina is one of the highest oxygen-consuming tissues in the
human body. Its inner layers have the high metabolic rate of
all central nervous tissue, and the oxygen consumption rate in
its photoreceptor layer is, uniquely, several times higher again.
The photoreceptor cells (rods and cones) are correspondingly
rich in mitochondria, which concentrate in their inner segments
and provide the ATP required by the ionic pumps that drive the
“dark current,” whose modulation by light is the beginning of
vision [51]. As a result, photoreceptors consume more oxygen
per gram of tissue weight than any cell in the body [51]. This
intense oxidative phosphorylation in their inner segments, coupled
with high concentrations of polyunsaturated fatty acids in their
outer segments, renders the retina susceptible to oxidative stress
and lipid peroxidation [49]. The retina also contains abundant
photosensitizers and is exposed to visible light [20]. Normally,
oxidative damage is minimized by endogenous antioxidants and
repair systems. With aging and/or retinal disease, there is an
increase in mitochondrial dysfunction and oxidative damage and
corresponding decrements in antioxidants and repair systems,
resulting in retinal dysfunction and retinal cell loss, leading to visual
impairment.
