Choice of Treatment is not Limited by Age but is Case-Specific

Robert M Schertzer, MD, FRCSC
Glaucoma & Anterior Segment Surgery
Multimedia Technology
Medical Director Visual Field and Optic Nerve Head Imaging Units
VHHSC/UBC Eye Care Centre

When pharmaceutical treatment of glaucoma proves ineffective, several surgical options remain available. In fact, some types of glaucoma may be best handled with immediate surgical intervention, even without prior medical management. Ocular surgery is any procedure that causes an alteration in the structure of the eye and can be laser (using a light) or incisional (using microsurgical blades). The type of surgical intervention indicated will depend on the mechanism of the glaucoma.

Laser surgery
There are three types of laser surgery used in treating glaucoma: trabeculoplasty, iridotomy, and cycloablation.

Trabeculoplasty, usually performed with an Argon green laser, is the application of laser energy next to the drainage channels (trabecular meshwork) around the circumference of the iris inside the eye (the coloured part of the eye.) This is used only for open-angle types of glaucoma, especially chronic ("primary") open angle glaucoma, pseudoexfoliation glaucoma, or pigmentary glaucoma.

Reviewing the Major Classes of Antiglaucoma Medication

Catherine M. Birt, MA, MD, FRCSC
Sunnybrook & Women's College
Health Science Centre,
Assistant Professor,
University of Toronto

Medical management of glaucoma is a field that has expanded dramatically over the past five or six years. Since aging is one of the major risk factors for the development of glaucoma, it is an area that is of great relevance to anyone managing geriatric patients. The purpose of this article is to review the five major classes of antiglaucoma medications, the drugs that are currently available in each class, their indications and their side effects.

Glaucoma is considered to be an optic neuropathy with characteristic optic nerve damage (with loss of the neuroretinal rim and an increased cup-to-disc ratio) and visual field changes (with arcuate field defects progressing to complete loss of peripheral vision). Intraocular pressure (IOP) is not part of the definition of the disease, as many people with statistically elevated IOP do not develop the neuropathy, and many patients with statistically normal IOP do. Intraocular pressure is considered a major risk factor for the development of glaucoma. Other risk factors include advanced age, race, positive family history, myopia, and systemic factors such as diabetes and hypertension. Glaucoma is generally divided into open versus closed angle, and each of these can be subdivided into primary and secondary subtypes.

Kathleen Jaques Bennett, BSc, BSc, MSc

In Ontario, 71% of the individuals with poor vision are over 65 years of age. To make matters worse, these seniors often suffer from additional sensory deprivation in the form of hearing loss.¹ Sensory deprivation can be defined as the partial or complete loss of any of the five senses. It can lead to embarrassment, social isolation, depression, or the labelling of the patient as demented or infantile by family and caregivers. Vision and hearing loss are strongly correlated to an increased risk of mortality over a five-year period,² probably because the psychosocial effects take an enormous toll on the afflicted individual. The partial or complete loss of the senses can lead to diminished quality of life, and may predispose an elderly person toward other conditions.

Types of Sensory Deprivation
Sensory deprivation can involve the loss of only one sense, or the combined loss of several senses. The loss of visual acuity associated with age often begins with the development of presbyopia. Presbycusis, the loss of hearing, is more prevalent among men than women.7 As well, touch, taste and smell become less acute with time. All of these forms of sensory deprivation undermine an elderly person's ability to live independently, increasing dependence on caregivers, and can result in the infantilization of the elderly individual. When sensory loss is coupled with another condition such as diabetes, the handicap becomes even more severe.

Tracey Tremayne-Lloyd and Lonny J. Rosen
Tremayne-Lloyd Partners,
Toronto, Ontario

Introduction
Of all the symptoms associated with illnesses that commonly affect geriatric patients, the most difficult to manage--for the patient and his or her physician--are those that affect the patient's mental faculties. Physicians attempting to treat geriatric patients who suffer the onset of mental illness, must deal with such issues as the patients' capacity to consent to treatment and their ability to participate in the management of their symptoms, including the regular taking of prescribed medication. While physicians always had tools embedded in provincial mental health legislation to assist them in the care of their mentally ill patients, these tools offered practically no alternative to committing patients to a psychiatric facility, something physicians have been loath to do.

After years of confusion within the mental health system, provincial governments in Mani-toba, Saskatchewan, British Columbia and now Ontario, have passed amendments to their mental health legislation which could lead to better care for people with serious mental disorders, including the elderly.

One of the main purposes of mental health legislation is to allow a medical practitioner to admit, or recommend for admission, to a psychiatric hospital for the purpose of an assessment, persons viewed by the practitioner as constituting a danger to themselves or others.

Hearing Loss in the Elderly Often Coincides with CAPD, Making Diagnosis More of a Challenge

Shechar Dworski, MSc

Hearing is an important part of our sensory system; it enables us to interact with our environment and to communicate verbally with others. Twenty percent of those over the age of 65, and 40% of those over the age of 75, have significant hearing loss, and at least 80% of nursing home residents have some degree of hearing loss.¹ There are two types of hearing impairment: peripheral and central. Peripheral damage to the ears can be caused by anything from the build up of cerumen to a perforated eardrum (for a description of peripheral hearing loss, see the articles on Hearing Loss and on Biology of the Aging Ear). Central processing impairment involves the dysfunction of certain areas of the brain's higher auditory centres that are responsible for hearing, language and comprehension. Causes of hearing loss include tumours, ototoxi-city from certain drugs, noise exposure and injury to the cochlear nerve and brain, as well as age-related degeneration of the ear and the associated neural pathways.

Impairments to the hearing process which occur in the brain are called central auditory processing disorders (CAPDs). With CAPDs, hearing impairment seems apparent even in the absence of any peripheral causes of hearing loss. CAPD can be defined as an impaired ability to recognize, discriminate, and/or comprehend auditory information.

Hearing Aid Devices are Tiny Yet Offer Greater Sound Amplification & Less Distortion

Cory Soal, RHAD
Registered Hearing Aid Dispenser

Hearing loss is as individual as a fingerprint. Generally, its progression is so slow that it remains undetected until it has become a real concern. Like any other medical problem, early detection of hearing impairment is important. A proper and thorough hearing test is crucial not only for purposes of diagnosis--it is key to determining what type of hearing aid technology will be the most suitable for a patient.

With the advent of micro-technology, hearing aids have become greatly improved. It is now possible to place more circuitry in a smaller package. Hearing aids can be fitted far into the ear canal and have internal controls that automatically adjust in extreme noise conditions.

First and foremost, a successful fitting of a hearing aid is dependent upon a complete hearing evaluation. A proper hearing test consists of the following components: Pure Tone Air and Bone Conduction tests, Speech Reception Threshold tests, and Speech Discrimination testing. The more accurately hearing is evaluated, the more suitable is the prescription for a hearing aid. There are two important concerns when selecting a hearing instrument. Firstly, the patient must be comfortable with the size of the hearing aid chosen: a patient can be fitted with a Behind-The-Ear (BTE), In-The-Ear (ITE), or the smallest hearing aid that fits Completely-In-The-Canal (CIC).

Kimby N. Barton, MSc
Assistant Editor,
Geriatrics & Aging

With recent advances in medical interventions for the treatment of cardiovascular diseases, including the introduction of ACE inhibitors and the use of b-blockers for left ventricular dysfunction, the role of coronary revascularization in managing elderly cardiovascular patients has become more difficult to define. Unfortunately, the bulk of research in this area has either failed to compare treatments directly, or has excluded patients who are 65 years or older. Research in this field has also focussed on long-term benefits of surgery over medical treatment, which may not be as germane to an elderly patient as symptomatic improvements, given that this patient's life expectancy may be considerably shorter than that of someone younger. In addition, with the increased frailty that accompanies old age, perioperative mortality and postoperative complications are a much greater concern for elderly patients. They are at an increased risk for stroke, acute renal failure, and other major complications. All of these factors suggest that caution should be exercised when extrapolating data from younger patients and applying it to older ones.

Common Presentations, Diagnostic Strategies, and Principles of Treatment

Michael A. Gardam MSc, MD, CM, FRCPC
Medical Director,
Tuberculosis Clinic,
Associate Hospital Epidemiologist,
University Health Network,Toronto.

The elderly are one of four sub populations in Canada, which also include the foreign born, homeless persons, and Native Canadians, that are at high risk for developing active tuberculosis. There are several reasons why tuberculosis is common among the elderly: Firstly, today's elderly have a high possibility of being infected with M. tuberculosis. They are survivors of the earlier part of the twentieth century in which an estimated three-quarters or more of the population were infected with tuberculosis by the time they were 30 years of age. Secondly, the elderly often suffer from other conditions which predispose them to reactivation of tuberculosis, such as diabetes mellitus, chronic renal failure, malnutrition, and diseases requiring prolonged corticosteroid therapy. Finally, residents of nursing homes and long-term care facilities may become infected or reinfected through contact with other residents with active disease.

Symptoms
While the clinical symptoms of tuberculosis may be vague and non-specific in any age group, this is particularly true in elderly persons. Fever, malaise, weakness, and failure to thrive are the most consistent symptoms.

Hearing Loss Traced to Age-related Changes in Cochlear Function and Central Auditory Processing

Nadège Chéry, PhD

In a society that extols the virtues of youth, hearing impairment in the elderly is often perceived as a graceless symbol of old age. Unfortunately, because of this attitude, most seniors would rather deny that, upon reaching their aged ears, even the most vibrant sounds fail to be heard. Hearing impairment affects over 50% of Canadians aged 60 years and over.¹ The incidence of hearing loss increases considerably with age, reaching 81% among persons 80 years of age or over.¹ Importantly, hearing impairment can have devastating consequences on the social life of an older person, and may profoundly alter their emotional wellbeing.^1,3,7 Although common among older adults, auditory processing defects are not an inevitable side effect of aging.^5,9 In fact, in most cases, hearing problems can be resolved,³ and yet, many older persons afflicted with hearing loss are unaware of this or simply choose not to deal with the problem.

Normal hearing is a complex mechanism that involves the transfer and subsequent conversion of sound into electrical impulses to be processed by the brain.

Target for a New Generation of Therapeutic Agents

Kimby N. Barton, MSc
Assistant Editor,
Geriatrics & Aging

The small southern Italian village of Nicastro, once again made it into International headlines when researchers at the University of Toronto discovered a new protein, nicastrin, which is involved in Alzheimer's disease (AD). Nicastrin was so named to honour a large family in Nicastro that has been plagued with AD for generations and played a key role in the 1995 discovery of two genes that cause early onset Alzheimer's. The same team, led by Peter St. George Hyslop, has found that nicastrin is a functional component of the g-secretase, which is involved in the formation of toxic plaques found in the brains of AD patients. More importantly, they have found an exposed and highly conserved domain of this protein that affects production of the amyloid-b (Ab) peptide and may serve as a potential target for pharmaceutical modulation of Ab production in patients with AD and other related disorders.

Much of the research into AD has been focused on the mechanism underlying the formation of the (Ab) peptide, which is a key component of the toxic amyloid plaques that are characteristic of brain tissue from patients with AD. In 1995, it was discovered that a mutation in a previously unknown protein could lead to an early-onset form of familial AD. This protein was subsequently discovered to be presenilin, a highly conserved, polytopic membrane protein. However, several studies have demonstrated that although mutations in presenilin may result in overproduction of the toxic Ab derivative, it is unlikely that the protein acts alone.

The Ab peptide is generated from a large precursor protein, the amyloid precursor protein (APP) in a two-step proteolytic pathway. Initially, the protein is cleaved near the cell surface in an extracellular domain either by a b- or a a-secretase to generate C-terminal stubs of the protein. These stubs are then further cleaved in their transmembrane domains by the presenilin-linked g-secretase to generate two different isoforms of the Ab peptide, one that is benign and one that is neurotoxic. The b-secretase enzyme appears to have a benign role; during development it may cleave a protein called Notch, which releases a fragment that activates gene transcription. Unfortunately it has been difficult to determine which proteins are directly responsible for the g-secretase activity, although evidence suggests that the presenilins are involved.

St. George-Hyslop's tream found that nicastrin binds to presenilins 1 and 2 and interacts with the APP carboxy terminal 'stub', the fragment that is produced by the initial, b-secretase cleavage. Mutations in an exposed and conserved domain of nicastrin, increase the production of both forms of the Ab peptide and deletions inhibit their production. The team also found that nicastrin is required for processing of the protein Notch, which is involved in gene activation.

So, nicastrin is structurally part of the g-secretase complex, but how does it interact with the other proteins? The team has suggested that nicastrin may bind to the APP stub and align it in the correct way to presenilin, so that it is cleaved at the right position. Another possibility is that nicastrin regulates the cleavage activity, in which case, compounds that interact with either nicastrin or the presenilins should effectively alter g-secretase and APP turnover; hence a site for pharmaceutical intervention.

Whether or not genetic variants in nicastrin are associated with inherited susceptibility to AD remains to be determined. Research in this field will be ongoing, but in the meantime pharmaceutical companies will no doubt devote a great deal of attention to this little 'Italian' protein.