As more than two million Americans suffer from eye related diseases, three studies summarized in this Examiner related article show that these potential medical treatments may cure people who suffer macular degeneration , retinitis pigmentosa , the most common form of retinal degeneration in humans, and people with aged related cataracts.
These findings were presented by three distinguished scientists during a press conference and during three hour poster sessions during the Society for Neuroscience conference that concluded about two weeks ago in Chicago. In brief, these studies remarkably showed that retinal implants, stem cell research and retinal fetal transplant tissue partially restored the vision in blind people.
A brief synopsis of each of the unpublished findings are presented below:
1. In a study in which 15 volunteers participated, scientists created a "bionic eye", a novel artificial retina consisting of an array of transistors and electrodes; these bionic eyes were implanted on the back of the eye of blind patients. In other words, these patients had tiny micro-chips implanted on the back of their eyes that allows them to process images sent by a digital camera mounted on eye-glasses. Each of the participants were then given a pair of this special glasses with a small video camera mounted on it, hooked to a belt with a tiny computer attached.
Without going into the technical aspects, the following is a brief description on the principles of the bionic device. The camera receives light from the environment and these signals are send to the tiny computer connected to the eye glasses in order to convert these signals into digitized information. The digitized data is transmitted to the implanted electrodes found on the back of the retina which then sends the signals to the ocular nerve. The prototype for this kind of bionic implant have been in the works for quite some time (over more than ten years in the working). In fact, some of the earlier versions of the bionic eye some damaged the retina of patients depending on how and where the chip and electrodes were implanted in the eye.
The patients were then evaluated by running a battery of tests to examine their visual acuity, central and peripheral visions. The evaluation phase was performed in patients three months following the implant of these devices in patients. The evaluation/ assessment phase consisted of asking patients to draw the direction and motion of an object they perceive while sitting in front from of a large monitor or were asked to describe what they see to researchers. Impressively, the results showed that 10 of the 15 patients were able to perceive moving objects during a rigorous evaluation of their visual perception and acuity. Overall, the results are very impressive although much research is needed to improve the quality and resolution of the Argus II retinal prostheses. The drawback right now is that they can only see moving blurs on a screen right now. However, these results are impressive considering that some patients were legally blind and be able to recognize faces in a room full of people may allow them to socialize one day and feel integrated in society.
2. On a second study lead by Jason S. Meyer from the University of Wisconsin, researchers found ways to differentiate both embryonic and inducible pluripotent stem cells into retinal precursor cells and finally into retinal cells using growth factors. A previous Examiner related article examined potential medical uses of both embryonic and induced pluripotent stem cells.
There are different types of retinal cells which include light -sensing rod and conce photoreceptors, specialized light-sensing neurons, and epithelial cells which support the photoreceptors. The human eye has millions of rod and cones in which rods are specialized for detecting bright and vivid colors while cones are specialized for detecting low intensities of light at night. The research presented by this group of researchers have shown for the first time that stem cells have been able to differentiate into retinal cells. The new stem cell technique allow to up to 90% of the stem cells to differentiate into neural retinal progenitor cells. In addition, all major types of differentiated retinal cell types were identified in this population of cells. This new line of retinal differentiated stem cells that were developed by this group of scientists could be used to better understand eye related disorders. In the words of the lead author, “ This ability could aid in the discovery of new therapeutic approaches to a variety of disorders affecting the retina; these findings could lead to treatments for other neurological disorders in addition to eye diseases”.
3. A phase II clinical trial lead by Dr. Robert B. Aramant from the University of California in Irvine and by Dr. N.D. Radtke from the University of Louisville, in Louisville, K.Y., showed the potential of using fetal retinal cells for restoring severe blindness. In brief, 10 patients with advanced retinal related diseases (20/320 vision) received transplants consisting of intact “sheets” of fetal retinal cells and were evaluated to determine whether the transplanted tissue developed into functioning retinal cells such as rods and cones. Impressively, seven of the ten patients improved, one remained the same and two other patients’ condition deteriorated at one year following transplantation. However, the patients that showed improvement were able to read letters on a chart and read time from a clock or watch. As a matter of fact, one patient’s visual acuity improved eight times more following retinal transplantation compared to before the surgery. The most impressive aspect of this study is that none of the patients experienced outright immunological rejection of the transplanted tissue thus far, possibly due to the embryonic nature of the tissue; it will be interesting to see whether rejection occurs at later stages of the clinical trial.
More importantly, the study lead by these authors show new evidence of the safety, benefits and medical potential offered by these novel techniques in retinal transplantation in humans. However, the application is still limited due to the low amount of donated retinal tissue available for transplantation at any given time or the need to obtain fetal retinal tissue (there is controversy to using fetal tissue for this purpose ). Lastly, these results indicated that it is a very viable technique to revert severe partial blindness but more patients are needed confirm these exciting results.
Final thoughts:
Although the research proposed during this press conference show that big leaps have been undertaken to find cures for severe blindness and eye related diseases, there still need more to be done before this can be possibly. In order to make more progress, retinal prostheses should be able to produce full visual acuity in blind patients as the human eye, a very difficult task considering the amount of data that computers have to process thousands of different colors, tones, shades and light patters simultaneously in matter of milliseconds. Moreover, the regenerative capacity of neural retinal stem cells needs to drastically improve and be able to generate neural retinal precursor cells in bulk amounts in order to offset the large requests from potential recipients. Lastly, and the promising results obtained from the phase II clinical study in which blind patients received transplanted retinal tissue needs to be repeated in different clinical trials to confirm its safety and efficacy of this potential treatment. Again, there is a lot of controversy with using human fetal tissue for this purpose and more needs to be done to adress ethical concerns with this kind of research.
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