The architecture of eye is one of nature's wonders and takes many shapes and forms. From the primitive light-detecting cells of invertebrates to the complex eye of mammals, there are many eye types in between these two ends of the “eye spectrum”, and some of these are thought to have evolved in parallel evolution. The eye of many animal types show adaptations to their specific environments. An example of this is seen in birds of prey, which have a significantly higher visual acuity than what we have as humans. Other species such as bees can see and extended spectrum of light into the ultraviolet range, which gives them an advantage in distinguishing different flower patterns. Finally, some animal species have multiple eyes, often of different designs and in different parts of the body. As editors of this book we are privileged to work on one of mother nature's evolutionary wonders.
The eye, like every other organ in the body is prone to disease and malfunctions and this creates both medical and socioeconomic issues that need to be addressed. We have a very poor understanding of these conditions and even poorer therapeutic options. This book seeks to address what future therapeutic avenues to treat degenerative conditions of the retina may open up over the next several years. Since many of these conditions result from cell loss, strategies to either prevent such losses or replace the lost cells are attractive, but technically difficult.
In the opening chapter, Nicolas Cuenca and colleagues describe the course of cell loss during retinal degeneration illustrated with “art-like” confocal images, with the following chapters exploring the cell biology behind this cell loss and how we might control it therapeutically. Mechanistic chapters focused on calcium overload and the role of inflammation in the degenerative process shed some light on the complex biological issues involved. Targeting cGMP production (François Paquet-Durand and colleagues), which is often deregulated in retinitis pigmentosa due to a mutation in the cGMP phosphodiesterase, is a rational approach that may yield results. The idea here is that if we can regulate cGMP production we may be able to prevent the loss of photoreceptors which are very sensitive to increased levels of the cyclic nucleotide. Other approaches include the use of biological-based therapeutics, but whatever approach is contemplated, delivery is always going to be an issue. This pivotal issue is explored in detail in chapters by Rocio Herrero-Vanrell and R. V. Rajala and their colleagues, who look at two quite distinct approaches.
Since many degenerative diseases of the retina result from the mutation of one of several different genes, the recent advances of gene therapy to rectify these conditions has several attractions. This may sound easy in theory, but is difficult in practice. This approach is eloquently described by Lolita Petit and V. Kalatzis in their chapter. The two final therapeutic strategies discussed in the book are neuroprotection and stem cell therapy; one prevents cells from dying and the other replaces the dead cells.
Only time will tell which of the above therapeutic strategies will make it to clinic. But with several horses in the metaphorical race there is bound to be at least one winner.
We would like to thank all the authors who have taken time from their busy schedule to contribute a chapter. We would also like to thank the people at the Royal Society of Chemistry for all their encouragement and belief in the subject and us as editors. I hope we did them and the subject justice.
Thomas G. Cotter and Enrique J. de la Rosa
Cork and Madrid