Hes 383 Physical Dimensions Of Aging PDF

HES 383 – PHYSICAL DIMENSIONS OF AGING Sept 14, 2023 Sensory changes with aging Prof Gina Whitaker, BSc Kin, PhD The UBC Okanagan Campus and the City of Kelowna are located on the traditional, ancestral, and unceded territory of the Syilx Okanagan Nation. SENSORY DECLINE WITH AGING – THE EYE REV...

HES 383 – PHYSICAL DIMENSIONS OF AGING Sept 14, 2023 Sensory changes with aging Prof Gina Whitaker, BSc Kin, PhD The UBC Okanagan Campus and the City of Kelowna are located on the traditional, ancestral, and unceded territory of the Syilx Okanagan Nation. SENSORY DECLINE WITH AGING – THE EYE REVIEW OF EYE ANATOMY - Light rays travel into eye and are bent within cornea and again in the lens in order to focus light onto retina.  Refraction - The lens is able to change shape in order to bend the rays more or less  Accommodation - The retina contains nerve cells (e.g. rods and cones) that transform light waves into electrical impulses and send to the brain for interpretation  Signal transduction LENS ACCOMMODATION DUE TO CONTRACTION & RELAXATION OF THE CILIARY BODY - Lens is attached to ciliary muscle via connective fibres  Relax ciliary muscle  stretch fibres  lens is pulled and flattened  focus on objects farther away  Contract ciliary muscle  relax fibres  lens recoils to form a more spherical shape  focus on close objects The lens contains collagen that makes it elastic such that it can recoil when ciliary muscle contracts AGE-RELATED CHANGES TO THE EYE Lens gets opaque & stiff Decreased density of cells of the neural retina Cornea thickens, flattens, gets rigid Degeneration of the sclera, pupil, iris CNS: Slower processing of visual stimuli  harder to ID objects, especially if they are moving, in and out of light quickly or have a complex figure or background PRESBYOPIA • The normal age-related gradual loss of the eye’s ability to focus on close objects. • Noticeable as early as 40s, with progressive worsening with age • Caused by stiffening of the lens  no longer able to recoil as well when the ciliary muscles contract • Treatment: lens correction (reading glasses or bifocals if you already need correction for other eye-sight issues PATHOLOGICAL CONDITIONS OF THE AGING EYE • Cataracts • Glaucoma • Age-Related Macular Degeneration • Diabetic Retinopathy CATARACTS • Opacity in the lens of the eye • A protein called crystallin is found in the lens cells. This protein normally makes the lens transparent. • With age, crystallin misfolds and the misfolded proteins aggregate  makes the lens opaque • Symptoms: decreased acuity, hazy vision, increased sensitivity to glare, harder to see lowcontrast • Tx: Surgical removal of the lens and replace with a prosthetic lens AGE-RELATED MACULAR DEGENERATION Macula – The area of the retina where the fovea is located. Very high density of rods and cones here. It is where we focus images • Loss of central field of vision • Dry AMD – most common, a slow and progressive disease • Build up of lipid deposits (Drusen) in the macula • Wet AMD – less common, Dry AMD can progress to Wet AMD • Growth of abnormal blood vessels that leak blood and fluid around the macula • No established treatment to prevent AMD or reverse vision loss, but people who exercise, don’t smoke, good nutrition  Lower risk of AMD Drusen Fluid and blood around the macula GLAUCOMA • Progressive optic nerve damage due to high intraocular pressure • Results in permanent loss of peripheral vision  Blindness if left untreated • Open-angle glaucoma - slow onset • Raised intraocular pressure that damages the nerves of the retina and optic nerve • Closed-angle glaucoma – acute, rapid onset • Sudden blockage of fluid outflow  rapid elevation of intraocular pressure • Severe pain, blurry vision, halos around lights • A medical emergency and vision loss progresses quickly • Treatment: Eye drops to relieve intraocular pressure WHAT IS RESPONSIBLE FOR CAUSING DAMAGE IN GLAUCOMA? a) Increased pressure inside the eye due to fluid build up b) Blood vessels within the retina burst c) Protein deposits block the light from hitting the retina d) The lens becomes clouded and light is scattered DIABETIC RETINOPATHY • Damage to blood vessels of the eye due to chronic high blood glucose levels • Initial stage: Microaneurysms form but are then absorbed retina  temporary sight issues (blurriness) • Over time: Capillaries of the retina begin to leak fluid into tissue  Edema of the retina  prolonged sight issues blood by the surrounding • Late stage: New blood vessels grow in the retina and easily rupture, bleeding into the eye  Blindness Symptoms range from: Blurred vision, decreased contrast sensitivity & night vision issues, spotty visual field loss, complete blindness Treatment: Control blood glucose levels. Laser to treat microaneurysms, surgically remove scar tissue SENSORY DECLINE WITH AGING – THE EAR ANATOMY OF THE EAR • Sounds waves come in at variable frequencies • Reach tympanic membrane, causing it to vibrate • Vibration transferred across the 3 small bones of the middle ear • Transfers vibration to fluid waves within the cochlea • The fluid waves push on the flexible membranes within the cochlea at different locations based on the sound frequency (pitch) • The movement of these membranes cause bending of the hair cells • The hair cells transform the mechanical signal into an electrical signal to be sent to the brain for processing PRESBYCUSIS • Age-related hearing loss (~50% of adults aged 60 – 79YO) • Usually manifests slowly as bilateral loss of highfrequency (high pitch) sounds. • If this extends to slightly lower frequencies, the ability to understand speech becomes impaired • Usually due to Sensorineural Hearing Loss – damage to sensory hair cells of the cochlea. This is thought to be due to damage from noise that accumulates over the years • Exacerbated by loud and busy surroundings • Tx: Hearing aids, cochlear implants OTHER AGE-RELATED HEARING PATHOLOGIES Tinnitus: perception of sounds in the absence of an acoustic stimulus • Ringing, buzzing, whistling • Due to age-related and noise-related damage within the structures of the ear • Can be caused by medications, nicotine, caffeine, high salt, stress, high or low blood pressure Central auditory processing disorder (or central presbycusis) • Issues processing the neural stimuli – interpretation, recognition, higher-order processing • Linked to neurodegenerative diseases such as dementia IMPLICATIONS OF VISION &/OR HEARING LOSS A LINK BETWEEN HEARING LOSS AND DEMENTIA • Untreated hearing loss is associated with accelerated cognitive decline and dementia • The mechanism underlying this association is not yet clear but there are a few hypotheses: • Changes in brain function: auditory centers work differently when hearing stimuli decline and this causes other changes in the brain • Increased cognitive load: increased effort required to process auditory stimuli, leaving less reserve for other cognitive functions e.g. memory • Social disengagement due to hearing loss reduced social and cognitive stimulation  cognitive decline • Both hearing loss and cognitive decline arise from some other common cause