During the last decade, numerous research reports have considerably improve
d our knowledge about the physiopathology of retinal degenerations. Three n
on-mutually exclusive general areas dealing with therapeutic approaches hav
e been proposed; gene therapy, pharmacology and retinal transplantations. T
he first approach involving correction of the initial mutation, will need a
great deal of time and further development before becoming a therapeutic t
ool in human clinical practice. The observation that cone photoreceptors, e
ven those seemingly unaffected by any described anomaly, die secondarily to
rod disappearance related to mutations expressed specifically in the latte
r, led us to study the interactions between these two photoreceptor populat
ions to search for possible causal links between rod degeneration and cone
death. These in vivo and in vitro studies suggest that paracrine interactio
ns between both cell types exist and that rods are necessary for continued
cone survival. Since the role of cones in visual perception is essential, p
ending the identification of the factors mediating these interactions under
way, rod replacement by transplantation and/or neuroprotection by trophic f
actors or alternative pharmacological means appear as promising approaches
for limiting secondary cone loss in currently untreatable blinding conditio
ns. (C) 2001 Elsevier Science Ltd. All rights reserved.