What is blindness?
Before any discussion can be had regarding biotechnological advances in artificial vision, we must identify what constitutes “blindness.” In our research, we’ve discovered several causes of the loss of sight, ranging from genetic to accidental. There are about 1.3 million blind people in the United States, 93,600 of whom are children.[i] 3.5% of the population age 65 and older is blind.[ii] Of course, many Americans are highly visually impaired even if they are not technically blind. For instance, 100 million Americans are “visually disabled” without the use of corrective lenses (70 million are myopic) and 80 million Americans suffer from potentially blinding eye disease.[iii] 5.5 million people have obstructed vision due to cataracts and 1.4 million cataracts are extracted each year.[iv] Furthermore, 2 million people are visually impaired by glaucoma, of whom 120,000 people are blind.[v] 4.2 million people have impaired vision due to corneal dystrophies.[vi] Additionally, 7.5 million Americans struggle with strabismus (cross eyes), and between 2-4% of the population is born with this ailment or develop it in their first 6 years of life.[vii] Luckily, many of these diseases and medical issues can be treated with corrective lenses, therapies or medicines. Unfortunately, several necessitate major biotechnological breakthroughs in order to recover or develop vision.
One major cause of blindness is age-related macular degeneration, which affects large numbers of adults older than fifty. Due to damage to the retina, patients lose vision in the macula, which means that patients lose the ability to see fine detail.[viii] There are two types of age related macular degeneration, wet and dry. Wet AMD occurs when blood vessels behind the retina begin to grow under the macula abnormally, leaking blood and fluid and thereby causing the macula to move from its normal location at the back of the eye.[ix] Dry AMD, on the other hand, develops when light-sensitive cells in the macula begin to break down, which causes blurred vision.[x] As you can see by looking at images 1 and 2, AMD is a serious ailment, causing major disruptions to afflicted persons’ lifestyles. The greatest risk factor for AMD is age—although it can occur in middle age, studies have shown that people who are older than 60 are at the greatest risk.[xi] In fact, at middle-age, people have about a 2 percent risk of developing AMD, while people over age 75 have a nearly 30 percent risk.[xii]
This is what one sees with normal vision
This is the same scene as viewed by someone with AMD
AMD can be treated in several ways. First of all, wet AMD can be treated with laser surgery, which uses a laser to destroy the fragile, leaky blood vessel to prevent further vision loss. Of course, this treatment is also somewhat risky and might destroy some surrounding healthy tissue—therefore, this type of treatment is not commonly used because it basically puts a bandage on the problem without stopping it from happening again.[xiii] Another option is photodynamic therapy, which uses a drug called verteporfin, which is injected into the patient’s arm. The drug “sticks” to the surface of new blood vessels, namely the ones in a patient’s eyes, and a light is shined into the eye to activate the drug. Once activated, the drug destroys the new blood vessels, which leads to a slower rate of vision decline but does not destroy surrounding tissue.[xiv] Finally, people who are affected by wet AMD have the option of taking drug injections, which block the effects of the abnormally high levels of a specific growth factor in their eyes so that the excess blood vessels in the eye are no longer produced.[xv]
Another type of vision loss is due to retinitis pigmentosa, which is another eye disease in which the retina is quite damaged, however this specific disease is genetic. This condition affects about 1 in 4,000 people in the United States.[xvi] The disease has several main symptoms, including decreased vision at night or in low light, loss of peripheral vision, and in advanced cases, loss of central vision.[xvii] Currently, there is no treatment for this disease, however we will later discuss treatments that are being researched, including microchip implants to the retina.[xviii]
Lastly, blindness can be caused by accidents, although only 4% of blindness in the United States is actually due to injury.[xix] Nevertheless, this number should not be ignored in biotechnology research because many people who lost their vision by accidents are actually army veterans. Americans face a unique ethical question when considering the fact that these veterans made this sacrifice in order to protect this nation, therefore they might deserve research and efforts into restoring their vision if that is at all possible. This brings up many public policy issues that we will discuss in a section on artificial vision’s role in current healthcare debates.
In the world of visual prostheses (artificial vision devices), the ability to reverse blindness is contingent on the circumstances surrounding the loss of sight. Visual prostheses have been found to be most successful in blind patients who have an optic nerve that was fully developed prior to the onset of blindness. In the case of people born with blindness, the optic nerve was not fully developed prior to birth and these patients might not receive the full efficacy of a visual prosthesis. One of the most advanced visual prosthetics currently under development is a retinal prosthetic device, which combats vision loss due to degeneration of photo receptors that arises from diseases like retinitis pigmentosa, coroidermia, and geographic atrophy macular degeneration. These technologies are founded on the knowledge that nerves behind a degenerated retina continue to function and can be electrically stimulated, which was shown in a study by Dr. Mark Humayun. [xx] This finding inspired researchers to create an artificial retina as a means of restoring vision. However, creating a retinal prosthetic device is no easy task. Not only does the device have to be safe and effective, it also needs to be durable enough to last for a lifetime for the individual. The device must be biocompatible with the delicate eye tissue, yet tough enough to withstand the corrosive, salty environment. It needs to be powered at a high enough level to generate a response, but it cannot generate enough heat that would damage the remaining functioning retinal cells. It also needs to stay put on the retinal macula. Furthermore, the image processing needs to be instantaneous so that there is no delay in interpreting an object in view. Of the several retinal prosthesis projects that are underway, the one that we chose to most thoroughly explore in our blog was the Argus Prosthesis Project.
The Argus Retinal Prosthesis Project
Arguably the most promising retinal prosthesis project, the Argus Retinal Prosthesis Project is developing an active epi-retinal prosthesis (with up to 200 electrodes on the current model) that transmit electronic pulses to the brain through the optic nerve. The artificial retina receives signals from a receiver that is attached to the surface of the eye, which in turn receives its signals from a pair of eyeglasses that the patient wears. This pair of eyeglasses holds a camera that captures images and passes the information along to a video processor, which then converts the image into the electronic signals that are sent to the receiver. Started originally by Drs. Mark Humayun and Eugene DeJuan at the Doheny Eye Institute (USC), this project has grown to include many different academics, private institutions, and the government (including the US Department of Energy as well as the National Institute of Health). This collaboration has pooled many human and capital resources and has generated some promising clinical results. While still years away from officially entering the market and becoming a profitable sector in the neural prostheses market, this project is certainly leading the pack of visual prostheses into the direction of market viability.
Innovations
Several innovations that we also discussed in our blog include the following:
• Curved Imagers:
o In addressing the limitations of flat image receptors, this innovation allows for prostheses to more accurately mimic the curved imagers found in nature. These curved imagers overcome shortcomings of the conventional systems, which use multiple lens combinations to reduce distortions at the edges of lenses. Ultimately, these curved imagers allow for more light-weight and cheaper prostheses that generate clearer images.
• Diamond Coating:
o In addressing the complications that come with trying to implant a piece of complex machinery into the eye without getting the circuitry damaged via reaction with the retinal fluid, researchers have found that their solution rests in the form of an ultrananocrystalline diamond film. This new film fulfills all of the necessary criteria for a coating; it is safe, long-lasting, electrically insulating, and tough. A diamond coating may be a great step forward in creating a device that has the potential of being used in human patients, but how this will affect the price tag on a retinal implant will be a vital factor for future users.
• CYCLOPS:
o In addressing the lack of ways to objectively evaluate the performance of visual prostheses, researchers have developed a small mobile robotic platform named CYCLOPS that can test the visual prostheses for them. CYCLOPS allows scientists to better assess what the blind can see with a retinal implant. It also allows scientists to identify ways to improve upon the implants.
The Artificial Silicon Implant Project
As the first retinal implant to move into clinical trials (currently Phase II), the ASR chip contains approximately 5,000 microscopic solar cells, called microphotodiodes, that convert light into electrical impulses. The chip is inserted into the subretinal space and basically takes on the role of photoreceptors: in response to light entering the eye, it sends the information along to the brain for interpretation. What is special about this microchip is that it requires no external battery source; the chip powered solely by incident light. This distinguishes the ASR from one of its competitors, ARCC (Artificial Retina Component Chip). The ARCC, like the ASR, is composed of light sensors and electrode arrays that send signals to the retinal neurons. However, the system requires additional power and is dependent upon an external camera to detect a picture and induce a laser pulse. Both the camera and the laser are built into a pair of sunglasses, which the patient will wear. Incoming laser light is then detected by the photo sensors in the implant to create a picture. The ASR is thus a much more elegant solution in terms of convenience and aestheticism. The fact that the ASR does not require any external power also greatly reduces the size of the chip (2 mm in diameter, 25 microns in thickness and is less than the thickness of a human hair) and makes surgery less invasive. In addition, the microchip is strategically placed so as to directly stimulate the remaining healthy cells in the retina. Of the 10 patients who received the microchip implant surgery, all reported some degree of improvement in visual function.
Besides these technologies outlined here, there are many other projects currently underway that are attempting to repair damaged retinal cells. For example, researchers are now using stem cells to reverse retinal degeneration. [xxi]
Sustainability of Artificial Vision
Although the technological advancements for artificial vision have come a long way in the past several years, the sustainability of the artificial vision systems such as the silicon chip retinal implants has not been confirmed. Research groups and biotechnology companies are currently still in the clinical trial stage and have not produced anything that will be on the market soon. Although feasibility trials have commenced recently to test the ability of the implants to be used for long term use, not enough time has passed to allow for definite conclusions. Most of the current research focuses on improving various aspects of the retinal implant, whether it be increasing the number of electrodes for better vision or developing materials that will raise durability. Other methods that have been developed to assist lost vision like the creation of an auditory soundscape to “see” be hearing, while holding the potential of becoming a veritable solution, is still very much in the preliminary stage of experimentation with little consideration for sustainability. Simply put, artificial vision is a field that is just in the process of taking flight, focusing greatly on feasibility, and thus has had little opportunity to deal with the issue of sustainability.
How Artificial Vision Fits Into the Current Healthcare Debate
Healthcare expenditures in the US are the highest of any developed country, at almost 16% of GDP. The Congressional Budget Office estimated that around one-third of 2006 health care expenditures, about $700 billion or nearly 5% of GDP, did not improve health outcomes. It is not surprising then that the current healthcare debate centers on the efficient allocation of funds and reform in healthcare policies that could reduce inefficient spending and deadweight costs. The crucial question to ask is then: To what sector of healthcare should we spend the most money on? And how do developments in artificial vision technology fit into the bigger picture of the current healthcare crisis?
The estimated annual costs of blindness to the federal government was $4 billion
in 1994. Although more up-to-date statistics could not be found, we believe that this number most probably went up in the past decade owing to the rapidly aging population in the US. 1.3 million of the US population is legally blind, and 3.5% of the population over 65 is blind. The main culprit for blindness in the elderly is age-related macular degeneration, which affects more than 1.75 million individuals in the United States. Owing to the rapid aging of the US population, this number will increase to almost 3 million by 2020. Although this number is relatively small compared to the entire US population (1% of the current population), there definitely are long-term costs of not addressing the needs of the blind, especially those of the elders, since they will be comprising over 20% in two decades. The main question we would like to ask is how much of these diseases are preventable, and how much current developments in artificial vision can actually contribute to treating blindness.
75% percent of total health care spending in the United States in 2007 went towards the treatment of chronic diseases, such as diabetes and asthma, and approximately half of all chronic diseases are linked to preventable problems including smoking, obesity, and physical inactivity. This spending could be vastly reduced through better consumer health practices and better preventive medicine. Interestingly, one of the two most common eye diseases in the US, age-related macular degeneration, is linked to causes that could be easily prevented. These causes include hypertension, high cholesterol, obesity, and smoking (smoking tobacco increases the risk of macular degeneration by two to three times that of someone who has never smoked, and may be the most important modifiable factor in its prevention). The Centers for Disease Control and Prevention reported that medical costs for obesity-related diseases rose as high as $147 billion in 2008, compared to $74 billion in 1998. Although age-related macular degeneration are caused by a number of other factors such as genetic predisposition and environmental cues, it is certainly a preventable disease. Therefore, it makes sense that the government should be allocating a high percentage of funds to the education and prevention of such diseases, and also to better geriatric care so that such diseases could be identified in the early onset.
On the other hand, advancements in artificial vision do seem to hold promise for those who want to regain vision. Nonetheless, medicine cannot solve every issue. This fact stems from the reality that there are limited resources to invest in research while there are countless diseases and ailments that affect the lives of many Americans. Therefore, at some point we must make a decision as to where we will allocate our scarce resources. This decision is not an easy one, and its effects will tacitly lead to the valuation of one person’s quality of life over another’s. Nevertheless, the decision must be made.
We are not qualified to make this decision for our society. Although blindness is not a deadly ailment, it certainly changes its victims’ lives forever. For those people who once had sight and lost it, blindness is truly devastating. Yet, as we said above, many people who develop blindness develop it at least in part due to lifestyle choices that they themselves made. Noting this fact, one might argue that we should not focus too heavily on research to cure this disease because it was, at least to some degree, self-imposed. Of course, if we had all the resources we could ever want, this argument would be very flawed, but reality legitimates it.
However, with regard to veterans of war who lost their sight in battle, a very compelling question is raised. What do we owe these veterans? Should society take on the burden of making every possible effort to restore these patients’ sight? At what point, if ever, do we decide that it is a lost cause and move on to helping veterans in other ways, namely therapy to help them to adjust to their new lives back home?
Medical research into treating vision problems has led to some of the most valuable lifestyle-improving devices of our day. From glasses to contact lenses, millions of people around the world rely on technologies that would have never been developed without the support of the biotechnology community. At this point in time, however, research into vision loss will lead to advances that could only possibly ever help a relatively small segment of society. It is for this reason that many policy questions must be considered when determining where funds and resources should be allocated. We hope that our blog has not only provided useful information as to what current research is being undergone in the field of vision loss, but has also left you with questions regarding what our society owes its citizens, especially its veterans, and where in the field of biotechnology we should focus our time and energy.
Best,
Stephanie, Victoria, Naomi and Yukiko
[xx] http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1809925/?tool=pmcentrez&report=abstract
[xxi] http://www.technologyreview.com/biomedicine/17768/
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