Fight against blindness is a big challenge in the field of Science and Technology. A recent report of the world health organization says that around 1.3 billion people live with some visibility impairment. Out of which, 39 million Peoples are completely lost the vision. In European and American country, visual acuity 20/200 and the visual field below 200 is considered as a parameter for blindness.
Visual acuity 20/200 means, a person will able to see an object in such a magnification as a normal person see at a distance of 200 meters. As per the report, the distressing thing is that in most of the cases eye could be saved if care and proper medication were provided to the patient. The life of a person with impaired vision is intricate. They lack education and often socially discriminated. One can observe their problem in transport or during accessing buildings etc.
A recent report in Nature Biomedical Engineering Journal is considered as a new hope for people who have blindness or extremely low vision. To discuss it, let us first focus on some basic points related to the eye. Blindness is a result of any damage or alteration in the vision-related pathway, i.e., cornea, lens, retina, optic nerves, thalamus, and visual cortex. The cornea is the eye’s outer most lens that helps to focus and control incoming light; it bends and refracts the incoming light on the lens. Lens again further focuses the light taking help of vitreous humor- a transparent gel-like substance that also provides support and attachment to retina. Image forms on the retina and further retina converts the optical signal into an electrical signal, which finally carried through optic nerves up to the thalamus and visual cortex.
Thalamus is the part of the brain which helps in relaying of sensory signal. The visual cortex is connected to the thalamus, and it processes the visual signal such that a person can exactly imagine the objects having the correct shape, size, and distance of the object. Problematic cornea distorts image, cloudiness, and in more severe conditions, causes blindness. Breakdown of a small portion of the retina in the case of age-related macular degeneration, hereditary disease degenerative retina, or retinitis pigmentosa is also retina related disorder. Damage of bundle of the optic nerve due to inflammation and pain is common, and hence, there is disruption in the signal going to the brain.
Now let us come on recent new development reported in Nature Biomedical Engineering Journal. Scientists report this work belongs to EPFL Switzerland and SSSA Italy. The novelty of this work is that it bypasses the complete pathway of the eyeball and directly sends the signal to the brain. So all the complication related to different pathway of eyeball does not interfere any way in this new technology. They invented a new thin intramural electrode which directly stimulates the optic nerve. This new invention has already been tested successfully in a rabbit. This new technology uses the concept of phosphine. Phosphine can be understood as a phenomenon in which one can experience seeing the light without actually any entrance of the light in the eye. Phosphine is generated directly by stimulating the visual cortex. In the present invention, prosthetic device implantation is required to do. The prosthetic device is made of medical-grade elastomer material already been popular as implant materials. Elastomer is further coated with a polymeric material known as PDMS to save the parent material for any degradation after implant. Two electrodes, cathode, and anode, acts as a generator and make the phosphine movable.
Now technology is reached in a stage where the complete eyeball is being neglected for seeing an object. But earlier first remarkable experimentation, namely retinal visual prosthesis (bionic eye), was reported in the year 2014 in which a group of Scientists from Centre of eye research Australia and other six Australian organizations reported this system. It was successfully tested in three persons of different age groups. In this bionic eye cathode made of platinum grown on silicon substrate was used, two return electrodes were also required in this system. However, it has produced some positive visibility results, but the main problem was related to the large size of electrodes and its energy back up. However, testing this device on the first three implanted persons was carried out for two years. In clinical test bacteria, S Aureus infection due to implantation was observed, and it raised a question mark in the success of this system.
The Second remarkable invention of an ongoing clinical trial is reported on the Argus II Retinal Prosthetic system. Five years of clinical testing results were published in 2016. However, this trial is being carried out for ten years, and still, the clinical trial is continuing. Argus II is a little complicated system having glasses attached with a small camera that further connected with a video processing unit. Implanting material has an array of 60 electrodes and a sealed electronic amplifying circuitry containing an antenna too. When the system is switched on, then camera collected video signals are processed, and real-time data is sent by an outside antenna to the receiving antenna inside the eye. This external device is kept fixed on the body of the patient by using a strap. In this clinical trial, 30 people of different age groups are participating, however, this system seems a little complicated, but it is exhibiting encouraging results.
Argus II was granted for trial by European regulatory in 2011 and the USA in 2013. Longest10 years of the trial reported being full of encouraging results. By 2021 expected to come in the market for the use of general masses. Out of 30 trial patients, few have only shown complication.15 out of 30 implants are continue to show reliability, long term efficiency, and fulfilling safety norms. However, two devices have shown failure, but the related technical problem was corrected in time. In one case, chronic hypotony was reported. Experts are correlating the problem with the patient’s other diseases developed before or during the trial period. The longest trail in the field of eye implant is Argus II, and it is indicating success and the nearest possibility for availability for masses.
In the year 2010, an artificial silicon retina was proposed, and it was implanted in six patients suffering from retinitis pigmentosa for a clinical trial. In this system, a photosensitive selenium cell and a microchip were also being implanted. This was initially exhibited good results as the visual acuity, perception of color, darkness, etc. were good enough. But after two months of trial, a sudden problem in vision was observed, and finally, the vision was lost. The problem with electrical stimulation was detected, and finally, this attempt did not materialize.
Ultrasonic wave for retinal stimulation was first introduced in 2012. The principle behind this is related to the transmission of real-time camera captured video signals through acoustic ultrasonic waves. The ultrasonic signal is seen quite capable of exciting retinal neurons. The good thing with this method is that it does not require an inside implant. Only a multi-element phased array is required to wear near cornea, infect it require to paste there. In ultrasonic stimulation, many questions are still to be answered by the scientific community. Long term effect or tolerability of ultrasonic wave is one of the questions. Scientists are working on a different technical issue. After a successful trial report, this device can come into the public domain.
Infrared neural stimulation
In 2005 use of infrared laser pulses to give neural stimulation was reported. Tissues water content get the infrared wave adsorbed. Adsorption results in photothermal stimulation. Water absorption of the infrared wave concept is used for visual restoration in this method. Black micro particle photo absorber is being used in this experimentation. Now conjugated polymer is replaced as a photo absorber. Work in different laboratories is going on in this visual restoration method. Biophysical and physiological characterization of this method is still in the testing period. This product has not come for trial so far.
Availability of Biocompatible implant materials
In this field, one of the major challenges is related to the availability of proper eye implant material. In most of the above-mentioned cases, the failure of experimentation was either related to the incompatibility of implant material or electronic devices. Once an implant is done in a patient the toxic effect of the implant with the period is another problem. In many earlier tests or trials, it has been found that initially, the implant worked well, but with the time, it started showing some infection or non-functioning kind of problem.
In the present time, a lot of work on graphene, carbon nanotube, or conjugated polymer is going on as an eye implant material. Reports coming are very encouraging. One of the main issues in the field of materials science is related to the reproducibility of fabricated material. But thanks God, new technology on 3 D printing of material has provided an amazing relief. In 3 D printing technology replica of material with full physical, chemical, and mechanical property can be fabricated. 3 D technology can be assumed a remarkable turn in the field of materials engineering, whatever be the complication in designing the material, one can do it in CAD programming and can be fabricated as per design using 3 D printing technology. This technology is cost-effective also, hence patients have not to worry much about implant costs too.
Preventive Eye disease
Good vision is the priority of all human beings. Most of the eye diseases are preventive and require little awareness. Let us discuss preventive eye disease and method of prevention-
Dry Eye: This problem is related to not proper secretion of tears or due to poor quality of tear. Applying warm compresses gives relief in this disease. Giving a short break to the eye is helpful. The habit of blinking properly is also one of the ways to prevent this disease.
Allergic Conjunctivitis: If a person is careful especially in the day which has a high pollen level then conjunctivitis is not going to affect. A chemical known as histamine present in pollen is the cause of this disease.
Glaucoma: Glaucoma causes due to high eye blood pressure. The disease can be prevented by regular exercise; exercise keep the pressure under control.
Tips to keep eye vision healthy
Foods: Fish such as salmon, tuna, etc are rich in Omega 3 fatty acids, it saves the eye from cataract, dry eye syndrome, and macular degeneration. Nuts are also rich in Omega 3 fatty acids. Citrus fruits are rich in vitamin C; it helps in reducing any kind of inflammation in the eye. It helps in maintaining optic nerves. Leafy vegetable contains carotenoids such as lutein and zeaxantnan helpful in maintaining retina health. Carrot is rich in vitamin A, helps in maintaining the ocular surface of the eye.
Specific exercises: Relaxing our eye in our long continues work is important. One simple exercise one can do by rubbing the palm for a few seconds and keep the palm on the eyelid. Let the warm transfer to the eye. This can be repeated twice or thrice. Blinking of the eye for 10-15 times very fast also provides a lot of comfort to our work stress eye. This should also be repeated for 4-5 times after a short interval.
The third effective one is sit somewhere comfortably and bring your both thumb together close to your eye by bending your arms. This a process of zooming your thumb. Rotating eyeball clockwise and anti-clockwise regularly at least once in a day improves the eyesight.
What to avoid: Smokers more likely to get into cataract problems. Smoking damages the optic nerves. Keep away looking direct sunlight or any high-intensity light source, it damages the retina. Long hours of continuous television watching is also not advisable. Proper Eye protection from dust, air pollution, snow, UV ray, etc is essential.