There are several kinds of vision impairments. The World Health Organization defines four levels of visual function: normal vision, moderate visual impairment, severe visual impairment, and blindness . Most visual impairments are caused by “uncorrected refractive errors”, issues with the physical structure of the eye. Refractive errors include astigmatism (irregular cornea shape), myopia (near sightedness), hyperopia (far sightedness), and presbyopia (inability to focus as a result of aging) . Diseases, such as glaucoma, can result in vision loss or blindness . Glaucoma damages the eye’s optic nerve. It can be caused by eye pressure buildup due to fluctuations in how fluid moves around the eye . Medication and corrective surgery can slow the progression of glaucoma .
Hearing loss can occur from a variety of factors. Things like hereditary, diseases and infections, trauma, reaction to medications, long-term exposure to loud noise, and aging can contribute to hearing loss . According to the National Institute on Deafness and Other Communication Disorders, there are two main types of hearing loss. The first occurs when the inner ear or auditory never is damaged. This is also permanent. The second occurs when sound is unable to reach the inner ear. This damaged can be caused by earwax build up, excess fluid, or a punctured eardrum. Treatments include hearing aids, cochlear implants, special training, medication, and surgery (such as ear tubes) .
For hearing and/or sight-impaired persons, animals have filled service roles to help those individuals increase their mobility and independence. Service animals can fetch items, turn on lights, aid in crossing streets, and recognizing alarms and other household concerns . Service animals have been predominately dogs. Dogs have long been human companions. Some dogs pull wheel chairs, fetch keys, and help those with vision impairments as guides and a second pair of eyes. Other animals have taken on the role of service animals as well, including chimpanzees for quadriplegics and even miniature horses in the same service roles as canines . Besides these task and assistance benefits, many owners of service animals report similar positive psychological gains that those with therapy or companion animals receive  A pilot study. Journal of Rehabilitation Research & Development. 45. 489-504.)]. The expansion and diversity of animals in service roles has caused push back in legal terms and concerns over health and safety of both humans and animals.
State of Current Research
Natalie Sachs-Ericsson, Nancy K. Hansen, and Shirley Fitzgerald (2002) conducted a literature review regarding the benefits of assistance dogs. Assistance dogs (ADs) aid persons with disabilities in conducting a variety of tasks. Ads might fetch keys and perform other daily activities. Service dogs (SDs) primarily work with people who have motor impairments while hearing dogs (HDs) aid those who suffer from hearing loss A review. Rehabilitation Psychology. 47. 251-277.)]. AD programs have been present in the United States since 1929, the first of which trained guide dogs (GDs) for the blind . The immediate physical benefits of ADs are fairly well known because these dogs are taught to do very specific and tangible tasks. Surveys collected data on the most common tasks SDs provide. These tasks including navigating the community (82%), getting around the house (78.2%), obtaining communication devices (72%), and other activities such as bathing, dressing, grooming, emergency responses, feeding, and toileting . The review also notes that owners of SDs also receive some of the psychological benefits that owners of strictly companion animals do, such as greater self esteem, lower stress and anxiety, increased confidence, and higher life satisfaction .
L. Whitmarsh (2005) claims that many visually impaired people who do not own a GD do not own them. A study was conducted to determine the benefits of GD ownership and why some people do not apply for guide dogs. In a study of 831 visually impaired people (404 GD owners, 427 non-GD owners), interviews collected information on ownership demographics, reactions to the guide dogs, awareness of guide dog programs, and reported benefits. When elicited about what might have put a potential GD owner off of owning a dog, misconceptions included age limits, non-eligibility for those with multiple disabilities, and cost of ownership  Other psychological misconceptions were reported, such as stigma attached to owning a dog, unwillingness to accept blindness, and unwillingness to undergo training.
Whitmarsh claims that service animals may provide the same comforts as companion animals . A similar study found that wheelchair users with SD reported more social interaction when with their SDs than a control group without SDs. Participants in GD programs and with GDs reported similar benefits: greater mobility, greater self esteem, and greater social interaction . Whitmarsh’s study also found that owners of GDs reported increased mobility and independence (81% reporting they felt their mobility had improved) . The author notes that while GDs may provide many benefits, they are not for everyone and practitioners should know what means of sight augmentation to suggest based on the person.
Diana Rintala, Rebeca Matamoros, and Laura Sietz (2008) conducted a study focusing on effects of assistance dogs on those with mobility and/or hearing impairments. Forty persons were recruited to participate in the study. For those with hearing and mobility impairments, the study reported positive changes in psychological functioning such as feelings of greater independence, higher self-esteem, and greater contentment . Negative responses were also reported. For some, the attention received in public from the SD or HDs was unwanted and a negative association with ownership. Some individuals also had poorly trained dogs, which contributed to negative responses. However, the authors maintain that the benefits of a SD and the tasks the animals are able to complete make up for the cost of owning the animal.
Since the introduction of SDs, other kinds of animals have stepped into the role of service animals. Monkeys assist paraplegics, miniature horses fulfill roles similar to SDs, and parrots for psychosis . Some animals have advantages over service dogs. Miniature horses have longer service lives than dogs do (30 years as opposed to 8 or 9) and are more docile. However, as more and more different kinds of animals were claimed by there owners to be service animals there has been a legislative pushback. The Americans with Disabilities Act (ADA) allows service animals entrance to public buildings such as restaurants, on public transit, and shopping centers . Service animals, unlike therapy animals, have a legal definition under the law and cannot be denied entrance with their owners. The variety of service animals, some legitimate service animals and some comfort or companion animals passed off as service animals, raised public concern over health and safety . In 2011 the ADA was revised to say “only dogs are recognized as service animals under titles II and III of the ADA” (ADA). Service animals are defined as being able to help accomplish a specific task. Comfort animals often fail to fill that definition, since providing comfort is a nebulous definition ( .
Rintala et al. note that, consistent with prior research, their findings lack diversity (most of their subjects were Caucasian). The authors believe more diverse studies would improve findings and give a more definitive picture of human animal bond benefits.
Whitmarsh (2005) suggests conducting a study to investigate the differences between mobility aids for those with vision impairments. Not everyone with vision impairments should use a GD, but materials for comparison should be available between mobility devices.
Service animals are defined as being able to help accomplish a specific task. Persons with mental disorders cannot always articulate the specific task their animals is able to provide. In cases like Jim Eggers (a man who has sever bipolar disorder and cannot be in public without large doses of medication), a therapy parrot helps him stay calm and social. Is that a specific enough task to provide justification for labeling that animal a service animal? Is there any reason to exempt particular animals as service animals if they are not dogs?
Rintala, D., Matamoros, R., Seitz, L. (2008). Effects of assistance dogs on persons with mobility or hearing impairments: A pilot study. Journal of Rehabilitation Research & Development. 45(4). 489-504.
This study examines the effect that assistance dogs have on persons with impairments. The article finds that people who have assistance dogs reported more independence and required fewer hours of paid assistance. The study also reports the positive and negative factors described by individuals with assistance dogs. Overall, more positive than negative factors are recorded. Positive effects include greater independence, positive emotional effects, and assistance with tasks. Negative effects cited were cost of care, unwanted attention in public, and shedding.
Sachs-Ericsson, N., Hansen, N., Fitzgerald, S. Benefits of assistance dogs: A review. Rehabilitation Psychology. 47(3). 251 277.
This article is a review of literature surrounding the distinctions between service dogs, guide dogs, hearing dogs, and the benefits of assistance animal ownership and utilization. Evidence for the benefits of assistance animal ownership is marshaled from activities of daily living that the animal helps with, as well as physiological and psychological benefits consistent with previous research in human and animal bond interaction. The article also addresses the disadvantages of assistance animal ownership, such as cost and behavioral issues.
Skloot, R. (2009). Create Comfort. New York Times Magazine. 34-40.
Rebecca Skloot’s article describes the difficulties associated with defining therapy animals versus service animals. Service animals are defined by law and cannot be restricted access to establishments via the Americans with Disabilities Act (ADA). The author describes cases where the line between service and therapy animals get blurred and the legal difficulties surrounding the allowance of many species of service animals. Since its publication, the ADA recognizes only canines as service animals.
Whitmarsh, L. (2005). The benefits of guide dog ownership. Visual Impairment Research. 7. 27-42.
This article outlines the benefits of guide dog ownership. Guide dogs are service animals assigned to those with some kind of disability. This specific study focuses on over 800 visually impaired people and found greater independence, confidence, companionship, and social interactions were reported in conjunction with guide dogs. Appealing to literature concerning the benefits of human and animal interaction, the authors cite better cardiovascular health, decreased depression, and higher well being in addition to the advantages a service animal provides. The survey in the study also asked about common misconceptions of guide dog ownership, including levels of visual impairment and deterrents in cost of care for the animal.
^ a b c d Rintala, D., Matamoros, R., Seitz, L. (2008). Effects of assistance dogs on persons with mobility or hearing impairments: A pilot study. Journal of Rehabilitation Research & Development. 45(4). 489-504.