Vision loss: Treatments and technologies
Blindness has long been one of humanity’s dreaded disabilities (Vash & Crewe, 2004), probably because we are a highly visual species. Indeed, primates are the most visually adapted order of mammals. Binocular vision allowed our primate ancestors to judge distances between trees and to detect prey and predators accurately. It is strongly linked to the complexity of primate brains, and – combined with fingers and opposable thumbs – allowed for development of the many technologies that have made humans the dominant species on our planet. It’s no wonder we experience a visceral response to the prospect of losing sight.
In this article, we look at the most significant contributors to loss of vision, and the treatments and technologies that have been or are in development.
Major eye diseases
The major eye problems that damage vision and/or cause blindness are:
- cataracts – a clouding of the lens, and the leading cause of blindness worldwide
- trachoma – a bacterial eye infection that can lead to scarring, which causes the margin of the eyelid to turn inwards, forcing the eyelashes to rub on the cornea and scratch it, often painfully; trachoma is the leading cause of blindness through infection
- diabetic retinopathy – a complication of diabetes that damages the retinal blood vessels
- glaucoma – a group of eye diseases that damage the optic nerve
- macular degeneration, also known as age-related macular degeneration –a group of chronic, degenerative retinal eye diseases that cause progressive loss of central vision.
An estimated 180 million people worldwide are visually impaired and, of these, between 40 and 45 million persons are blind. About 80 per cent of blindness is avoidable (resulting from preventable or treatable conditions).
In 2011–12, more than half of all Australians reported at least one long-term eye condition, and nearly half reported wearing glasses or contact lenses. Between 2001 and 2012, the proportion of the population affected by long-sightedness rose from 22 per cent to 26 per cent, while the prevalence of short-sightedness increased from 21 per cent to 23 per cent. The risk of a long-term eye condition increases with age: 95 per cent of people aged 55 years and over reported an eye problem, compared with 11 per cent of those aged 0–14 years.
Cataracts are more common in people who smoke, consume alcohol at harmful levels, are obese, have a family history of cataracts, have diabetes or high blood pressure, have had long-term sun exposure without good eye protection, have had injuries or inflammation to the eye, or have taken certain medications (such as steroids).
People with diabetes are 25 times more likely to experience vision loss than people without the disease. A recent study found prevalences of diabetic retinopathy of 28.5 per cent and 39.4 per cent among non-Indigenous and Indigenous Australian adults with self-reported diabetes (respectively). Diabetic retinopathy, cataracts, refractive error and trachoma account for 94 per cent of cases of vision loss in Indigenous Australians.
Trachoma is a disease of disadvantage, spreading through poor hygiene. Women suffer more frequently and severely from trachoma than men, due to more frequent reinfection caused by exposure to infected children. Eighty per cent of trachoma sufferers live in 13 African countries and Pakistan. Australia is the only developed country with endemic trachoma (in some remote Indigenous communities in the Northern Territory, South Australia and Western Australia). The prevalence of trachoma in Indigenous Australians was 14 per cent in 2009, but fell to 4.7 per cent by 2014.
Approximately 300 000 Australians (about 1.25 per cent) have glaucoma. Two per cent of Australians will develop glaucoma in their lifetime, and one in eight aged over 80 years. First-degree relatives of people with glaucoma have an up to 10-fold increased risk of developing the disease. About half of all glaucoma cases remain undetected.
Macular degeneration is the leading cause of legal blindness in Australia, responsible for 50 per cent of all cases of blindness. About one in seven Australians – or 1.15 million people – over the age of 50 years has some evidence of this disease. Approximately 17 per cent of these people will experience vision impairment. Over 14 per cent of Australians over 80 years of age have vision loss or blindness from age-related macular degeneration.
Past and current treatment
No effective treatments for any serious eye problems existed until very recent times. In fact, it’s fair to say that until modern times the treatment was often worse than the disease.
Perhaps the most famous example of botched treatment is John Taylor’s blinding of the composers George Frideric Handel and Johann Sebastian Bach. The standard 18th-century treatment for cataract involved a needle being poked into the eye to push the cataract-clouded lens out of the field of vision. This worked in about a third of cases, but in a time before knowledge of hygiene, bacterial infection was rampant; a post-operative infection is thought to have killed Bach. Moreover, the surgery was at least as likely to blind the victim as the original complaint, and often induced painful and/or vision-reducing complications.
Fortunately, contemporary treatments for conditions that affect vision are much safer and more effective.
Surgery is the only effective long-term treatment for cataracts, which worsen progressively in adults (but not always in children). Surgical treatment is very safe, usually involving replacement of the clouded lens with an artificial one under a local anaesthetic. Cataract removal and lens replacement are among ophthalmology’s most successful procedures.
All people with diabetes are at risk of developing diabetic retinopathy, so regular eye examinations are vital to reduce the risk of vision loss and blindness. Laser treatment to seal leaking blood vessels and stop the growth of abnormal blood vessels is highly successful; traditional surgery may be required in people with more advanced disease.
The exact causes of glaucoma are unknown, but in some cases it results from malformation of the eye’s drainage network, or blockage due to natural ageing processes or injury. Initial treatment involves administration of eye drops and medication; if the blockage in the drainage system does not clear, surgery may be necessary.
Early detection of any form of macular degeneration via an eye test is crucial to halting progression of disease and saving the person’s sight. Macular degeneration is either ‘dry’ or ‘wet’. The dry form results in gradual loss of central vision. No treatment is currently available, but diet and lifestyle, including the use of an appropriate supplement, can slow disease progression and vision loss.
The wet form of macular degeneration involves abnormal blood vessels growing under the retina, resulting in a sudden loss of vision. A protein called Vascular Endothelial Growth Factor (VEGF) causes this process;
anti-VEGF drugs can be injected into the eye to combat it. Anti-VEGFs do not cure the disease but can stabilise and maintain vision, and will improve vision in some people.
The bionic eye
A bionic eye is a prosthetic device consisting of a glass-mounted digital camera and a microchip implanted into the eye of a blind patient. The camera transmits high-frequency radio signals to the microchip, which causes an array of electrodes on the retina to stimulate the nerve cells that would normally receive input from the person’s missing photoreceptors. The nerve cells send the information to the brain, which generates a pattern of electrical signals that replicates those from a sighted person’s eye.
Three retinal bionic eyes have already been approved for commercial sale: the Argus II (United States), the Alpha-AMS (Germany) and the IRIS V2 (France). An Australian bionic eye has been in development for almost a decade, and is expected to involve safer surgery than existing bionic eyes due to being implanted at the back of the eye rather than inside the eye.
The Australian bionic eye is intended to help people with severe vision loss due to retinitis pigmentosa or age-related macular degeneration. (Retinitis pigmentosa is the major cause of inherited blindness, affecting 1.5 million people worldwide.) To benefit, patients must have:
- some remaining retinal ganglion cells
- a healthy optic nerve and visual cortex
- very low or no vision
- to have been able to see in the past, so that the vision-processing part of the brain has developed fully.
Bionic Vision Australia has developed three bionic eye devices to date: a prototype with 44 electrodes, a wide-view device with 98 electrodes and a high-acuity device with 256 electrodes. Tests have been completed with three people. Before surgery, these patients could not see a hand in front of their face; with the bionic eye they could locate objects on a table and navigate around objects while walking. A second-generation bionic implant is set to be trialled in 2018.
Access to high-quality information is a significant problem for blind and visually impaired people, and finding and using spatial information is particularly difficult. Augmented reality (AR) applications for people with visual impairments, or AR4VIs, are solutions that combine annotation with spatial location data, using electronic glasses containing cameras and sensors or other forms of portable personal technology. Unlike existing assistive technologies, AR4VIs do not require modifications to the built environment. They take advantage of accelerating improvements in computing power, connectivity and cloud-based resources, making spatial information available widely, quickly and cheaply.
Augmented reality assistance can involve speech or audio cues, haptic or tactile feedback, or image enhancement for people who have some vision. AR enables users to explore their environment in a natural way, by touching, pointing or otherwise indicating a location or direction of interest. The reality augmentation is provided as information related to the location or the direction indicated by the gesture.
AR4VI can provide audio–haptic access to tactile documents and maps, and 3D models. This has long been done using braille labels (e.g. automatic teller machines and traffic light buttons), but is severely limited by the space available on objects and the lack of braille literacy. Audio labels are an alternative, enabling users to explore surfaces with the fingers and receive aural information about locations of interest through touch-sensitive sensors or camera-enabled ‘smart pens’ that interact with a customised surface. These methods are effective but require each object to be specially modified, which is very costly.
In an AR4VI approach to audio labels, a camera tracks the user’s hands as they explore an object, and triggers audio feedback when a finger points to a ‘hotspot’. It enables feedback from existing objects with minimal or no modification. Existing applications include geographical maps, optical character recognition (reading text from paper or screens) and a free smartphone app that gives blind pedestrians accurate information about business locations, addresses and other points of interest. With the overTHERE app, the user simply points their phone to hear audio cues explaining what is ‘over there’. The smartphone’s global positioning system (GPS), magnetometer and other sensors are used to estimate the user’s location and pointing direction, and thereby to determine directions and distances, and generate audio cues.
Vision loss – whether inherited, age-related or caused by accidents or infections – is a serious disability affecting hundreds of millions of people worldwide. Governments and public health organisations are working to reduce the incidence of preventable blindness, with some success. Early detection and treatment are vital for most conditions, but remedial and surgical techniques are now highly effective, and novel technologies such as the bionic eye and AR hold great promise for improving mobility and accessibility for people who are blind and visually impaired.
Vash C, Crewe N. (2004) Psychology of disability (2nd edn). New York: Springer Publishing.