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Nursing Practice Keywords Special sense organs/ Presbyopia/Presbycusis/Tinnitus Systems of life This article has been Eyes and ears double-blind peer reviewed In this article... ● Age-related changes to two special sense organs ● Physiological processes behind declining sight, hearing and balance ● Common sight and hearing pathologies arising in older age

Anatomy and physiology of ageing 6: the eyes and ears

Key points Authors John Knight is senior lecturer in biomedical science; Chris Wigham is senior Of all age-related lecturer in interprofessional studies; Yamni Nigam is associate professor in biomedical 1changes to the science; all at the College of Human Health and Sciences, Swansea University. special sense organs, the most Abstract The special senses – sight, hearing, smell, touch and balance – allow us to dramatic are seen in perceive the world and communicate. Like all body systems, they undergo age- the eyes and ears related changes that negatively affect their function. Physiological changes to the Presbyopia is eyes and ears mean older people gradually see, hear and balance less well. The 2the age-related changes also increase the risk of conditions such as cataracts, age-related macular decrease in the degeneration, and conductive and sensory hearing loss. This sixth article in our series ability to see objects on the effects of age on the body describes what happens to the eyes and ears. that are near Presbycusis is Citation Knight J et al (2017) Anatomy and physiology of ageing 6: the eyes and ears. 3the sum of all Nursing Times [online]; 113: 7, 39-42. conditions that lead to decreased hearing with age he special sense organs – the causing the eyeball to recede into its socket Changes to eyes, ears, nose, tongue – detect (enophthalmos). As a result, eyelid tissues 4the vestibular information coming from the become lax and the levator muscles in the system of the inner Tenvironment, such as light, eyelids weaken, causing the eyelids to ear contribute to sound, smells and tastes, which is then droop (ptosis). Drooping eyelids can grad- balance problems relayed to the brain where it is processed ually obstruct the upper field of vision. in older people into meaningful sensations. Diminished Sinking eyeballs and drooping eyelids Regular testing acuity of the special senses reduces our often lead to the conjunctiva lining the 5allows early ability to perceive the world and commu- eyelids (tarsal conjunctiva) failing to suffi- diagnosis of nicate. All the senses go through an age- ciently lubricate the front of eye (cornea). common age- related decline, but the most dramatic This can result in an air space developing related sight and changes are seen in the eyes and ears. This between the lid and the cornea, particu- hearing problems sixth article in this series on the effects of larly at night, potentially leading to epithe- ageing on the different body systems lial breakdown (Sobel and Tienor, 2013; examines the age-related changes in the Liang et al, 2011). eyes and ears. In some people, the weakening of the muscles supporting the eyelids and loos- The ageing eye ening of the eyelids result in the eyelashes Vision is affected by the ageing of the turning inwards (entropion) and irritating internal and external structures of the eye. the cornea’s surface, which could lead to Its decline is gradual and linear, and detect- ulceration. A significant weakening of the able changes begin in the third decade of muscles supporting the lower eyelids can life. The main changes are outlined in Fig 1. result in them ‘flopping away’ from the eyeball (ectropion), which can then dry out Anatomical changes and become irritated. Symptoms of entro- The retro-orbital fat, which protects and pion and ectropion can be relieved by anti- cushions the eye, atrophies with age, inflammatory eye drops or artificial tears,

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Fig 1. Age-related changes to the eye effect on the pupils’ ability to adapt to changes in light intensity – for example, Vitreous humor when going from light to dark. Adapting ● Changes from gel to Pupil to the dark requires the photosensitive ● Resting pupil diameter liquid, may detach from cells of the retina to regenerate the photo- decreases retina (posterior vitreous detachment) pigment rhodopsin; this is considerably delayed with age, which contributes to night-vision problems. These changes increase older people’s risk of falls and other accidents, for example, when leaving a brightly lit bath- room to walk up or down a flight of poorly lit stairs (Rukmini et al, 2017; Turner and Mainster, 2008; Bitsios et al, 1996). Lens Macula (fovea centralis) of retina ● Lens proteins precipitate ● Receptors generate and die, causing Posterior vitreous detachment (cataract formation) loss of central vision (age-related The eye consists of two hollow chambers macular degeneration) separated by the lens. The anterior chamber is filled with a watery fluid while surgery to tighten the skin and mus- Late-stage ageing of the lens and cataracts (aqueous humor) and the posterior cles of the eyelid can provide permanent New lens cells continue to be produced chamber with a jelly-like material (vit- relief (Garrity, 2016). throughout life, so the lens continues to reous humor). The composition of the vit- increase in density. This can cause par- reous humor can change from a gel to Changes affecting tears ticular light frequencies to be absorbed liquid with age and, in some people, it With age, the lacrimal glands produce fewer and the lens to take on a yellowish hue, shrinks, collapses and separates from the tears, while the composition of tears affecting contrast sensitivity and the accu- retina. This posterior vitreous detachment changes, and the wetting efficiency and sta- rate perception of colours. often manifests as discrete opacities bility of the tear film is reduced. This leads When the concentration of proteins in (floaters) or sheering patterns in the field to dry eye syndrome in up to 14% of the over- the lens becomes very high, precipitation of vision (Bishop et al, 2004). 65s. Irritation, grittiness and pain can ensue occurs. This is seen as a cataract. The and affect many activities, such as reading scattering of the light causes a glare or a Age-related macular degeneration or watching television. Persistent irritation halo effect when looking at bright lights. With age, cone photoreceptor cells in the can make the cornea less sensitive, which in As the densest area of the lens is the centre, fovea, which provide high-quality colour turn can diminish the ability to detect injury this is where age-related cataracts are most vision, begin to die, eventually resulting in or infection. Many people find the use of commonly seen. age-related macular degeneration (ARMD). artificial tears effective (Bit.ly/NHSChoices- Cataracts can make it difficult to see in This is thought to be caused by changes to DryEyeTreatment; Dry Eye WorkShop, 2007). certain circumstances – for example, when the cells of the retinal pigment epithelium driving at night. They can also interfere (RPE), which lies next to, and maintains, Vision changes with the ability of certain wavelengths of the photoreceptor cells. Presbyopia light to enter the eye, thereby reducing There are two types of ARMD: dry (90% of Throughout life, equatorial lens cells colour perception: people with cataracts cases) and wet (10%). Dry or atrophic ARMD divide and new cell layers are added to the may wear garish clothing due to their com- is characterised by a gradual bilateral loss of outside of the lens. Since the lens cannot promised colour vision. vision as the RPE degenerates. Wet or exuda- grow in size (if it did it would soon out- Individuals with poorly controlled dia- tive ARMD is caused by the growth of new grow the eyeball), its cells must be com- betes are at much greater risk of devel- blood vessels in the space between photore- pressed, which results in the lens oping cataracts because increased blood ceptors and RPE (subretinal space) and the becoming increasingly dense and inflex- glucose encourages the build-up of dam- leakage of serous fluid from these new ves- ible. The lens, therefore, becomes progres- aging levels of sorbitol in the lens (Knight sels. Wet AMRD has a more rapid onset and sively less able to change shape to be able et al, 2017). causes more severe loss of vision. to focus light on the retina. Cataracts are managed by removing the In ARMD, pale yellow-white elevated Presbyopia is the age-related reduction lens’s contents from the capsular bag and spots called drusen appear on the retinal in the ability to see near objects. It typically placing a small intraocular lens inside the surface, distorting vision and reducing presents as an inability to read text posi- capsule to provide refractive power. The visual acuity. Their appearance steadily tioned close to the eye and generally power of the intraocular lens can be chosen increases after the age of 60 years. ARMD develops in the 40s and 50s. Presbyopia to suit the patient’s wishes and lifestyle accounts for half of all visual impairments results from a reduction in the ability of the (Truscott, 2003). among people aged 75 and over (Bit.ly/ intraocular lens to change shape. The dis- AMDMacularDegeneration; Bit.ly/NERC- tance from the eye at which print can be read Pupil changes and poor night vision MacularDegeneration; Forester et al, 2001). (near point) increases from about 10cm at One role of the pupils is to regulate the the age of 20 to over 100cm by the age of 70. amount of light entering the eye. With age, The ageing ear Most people manage presbyopia by using their diameter decreases, reducing the The ear is the organ of hearing but also catherine hollick catherine correcting reading glasses (Boyd, 2016). admittance of light. Age also has a negative plays the major role in our sense of balance.

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Problems with hearing are the most Fig 2. Age-related changes to the ear common sensory disorder associated with ageing. At age 61-70 years, around a third of people develop problems understanding Helix and tragus Vestibular apparatus: semi- circular canals and otolith organs speech if there is ambient background ● Hairs grow external middle inner ● Hair cells are lost and otoliths noise, and in those aged 85 years and over EXTERNALear EAR MIDDLEear EAR INNERear EAR degenerate, negatively affecting this rises to around 80% (Sogebi, 2015). balance Age-related changes to the ear are shown in Fig 2.

Outer ear changes Cochlea ● Outer and inner The auricle (pinna) collects sound waves hair cells Pinna and directs them through the ear canal degenerate, ● Enlarges (auditory meatus) to the eardrum. With causing with age age, the pinna often becomes larger and presbycusis features more external hair on the tragus and lower helix; these changes are more often seen in men. The pinna becomes increasingly dry and scaly in both sexes. Eustachian tube The auditory meatus produces earwax Muscles atrophy (cerumen), which moistens the ear canal and is mildly antiseptic, helping to keep the ear free from infection. Unless com- Ear canal Ossicles Tympanic membrane pressed and pushed inwards by imple- ● Potential for collapse Joints between bones calcify ● Becomes less vascular ments such as cotton buds, cerumen grad- ● Earwax accumulates, with and become thinner ● Elasticity and compliance ually works its way out (the ears are often associated hearing loss decrease described as self-cleaning). With age, the ceruminous glands become less active and produce less earwax, synovial joints between the three auditory Presbycusis which can lead to the auditory meatus ossicles are often stiff and calcified, Almost everyone experiences a deteriora- becoming increasingly dry and prone to leading to less efficient conduction and tion in hearing as they age, and currently infection. The cartilaginous components amplification of sound waves. there is no way of preventing or reversing that form the walls of the auditory meatus The air-filled chamber of the middle ear these age-related changes. Presbycusis is can lose elasticity, degrade and sometimes is connected to the back of the pharynx by “the sum of all conditions that lead to collapse, which increases the likelihood of the auditory or Eustachian tube: this ensures decreased hearing sensitivity with age”; it ear canal collapse (Howarth and Shone, the pressure is kept relatively equal on both can be accelerated by exposure to loud 2006). A drier environment and ear canal sides of the eardrum to prevent pressure noise, conditions that impair cardiovas- collapse both increase the likelihood of building up and damaging the tympanic cular function and nerve damage (Parham cerumen accumulation and obstruction, membrane. The musculature lining the et al, 2011). Presbycusis is usually associ- commonly resulting in conductive hearing auditory tube often undergoes age-related ated with a progressive degeneration of the loss. Older people may need to use earwax atrophy, which may interfere with the tube’s hair cells and neurones in the cochlea. softeners before having excess wax removed opening during swallowing, thereby It has been suggested that a lifetime by micro-suction at audiology clinics or by increasing the risk of pressure differences exposure to loud noises cumulatively dam- syringing at GP surgeries. between the two sides of the eardrum. ages hearing. Indeed, some people living in isolated, non-industrial communities in Middle ear changes Inner ear changes Africa and India have little age-related The middle ear consists of the ear drum The inner ear consists primarily of the: hearing loss. Inheritance of certain genes, (tympanic membrane) and a hollow, air- ● Cochlear – which detects sounds; increased exposure to free radicals and filled chamber spanned by three tiny bones ● Vestibule and semicircular canals toxins, and decreasing blood supply to the (auditory ossicles): – which are responsible for balance. inner ear (Danner and Harris, 2003) con- l Hammer (malleus); The cochlear is a fluid-filled, spiral- tribute to presbycusis and the rate at l Anvil (incus); shaped organ that receives sound waves which it develops. A slowing in the brain’s l Stirrup (stapes). directly from the stirrup. Sound waves processing of auditory information is The tympanic membrane vibrates in travel rapidly through the fluid of the another contributing factor. harmony with the sound waves collected cochlear and are detected by special sen- Presbycusis is particularly associated by the outer ear, and these vibrations are sory receptor cells called hair cells. These with a declining ability to hear high fre- transmitted and amplified across the relay auditory signals to the cochlear quencies, which are important for inter- middle ear by the three auditory ossicles. nerve, which delivers them to the auditory preting speech. As a result, older people With age, the tympanic membrane cortex of the brain, where they are per- find it increasingly difficult to follow and becomes less vascular and begins to thin ceived as sound. Our sense of hearing is join in conversations, especially when and stiffen (Liu and Chen, 2000; Wein- most acute at the age of 10 years and gradu- competing background sounds (for catherine hollick catherine stein, 2000). In older people, the tiny ally declines thereafter. example, from television or music) are

Nursing Times [online] July 2017 / Vol 113 Issue 7 41 www.nursingtimes.net Copyright EMAP Publishing 2017 This article is not for distribution Nursing Practice Systems of life present. This can restrict interactions and Box 1. Eye and hearing tests: undergo regular testing because this con- contribute to loneliness and social isola- recommended frequency dition (which is not part of the normal tion (Parham et al, 2011). ageing process) can be hereditary. NT l From the age of 70 years onwards: Tinnitus eye test at least every two years References Bishop PN et al (2004) Age-related changes on the Tinnitus is the hearing of a noise – often a l From the age of 60 years onwards: surface of vitreous collagen fibrils. Investigative ringing, buzzing, humming or whooshing hearing test every 2-3 years Ophthalmology and Visual Science; 45: 4, 1041-1046. – in the absence of any external sound; it is l People with a family history of Bitsios P et al (1996) Changes in autonomic function with age: a study of pupillary kinetics in occasionally reported as having a musical glaucoma: eye test every month until healthy young and old people. Age and Ageing; quality (Bit.ly/AllAboutTinnitus). The con- intraocular pressure is normalised 25: 6, 432-438. dition has a variety of causes, including: and then every year Boyd K (2016) What is Presbyopia? American Academy of Ophthalmology. Bit.ly/AAOPresbyopia ● Changes in blood flow in the ear; Danner CJ, Harris JP (2003) Hearing loss and the ● Drug toxicity (from example, adverse aging ear. Geriatrics and Aging; 6: 5, 40-43. reactions to gentamicin); touch and the vestibular system of the inner Dry Eye WorkShop (2007) The definition and classification of dry eye disease: report of the ● Muscular spasms in the ear; ear. To trigger the intricate motor coordina- Definition and Classification Subcommittee of the ● Loss of hair cells. tion of skeletal muscles required to main- International Dry Eye WorkShop. Ocular Surface; 5: However, the major cause of tinnitus tain balance, various regions of the brain 2, 75-92. Forrester JV et al (2001) The Eye: Basic Sciences might be the lack of sensory input reaching need to quickly process a large and contin- in Practice. New York, NY: Elsevier. the auditory cortex of the brain. Tinnitus has uous input from these sensory systems Garrity J (2016) Entropion and Ectropion. Bit.ly/ been compared to phantom sensations per- (Horak, 2006). MerckEntropionEctropion Horak FB (2006) Postural orientation and ceived in a non-existent limb after amputa- The vestibular system of the inner ear equilibrium: what do we need to know about tion: in some people, the sounds associated consists of a labyrinth containing semicir- neural control of balance to prevent falls? Age and with tinnitus persist even after the cochlear cular canals and their hair cells, and the oto- Ageing; 35: Suppl 2, ii7–ii11. Howarth A, Shone GR (2006) Ageing and the nerve has been severed (Danner and Harris, lith organs (utricle and saccule). All are key in auditory system. Postgraduate Medical Journal; 82: 2003). As ageing is associated with a loss of maintaining balance. With age, the vestib- 965, 166-171. Knight J et al (2017) Diabetes management 2: sensory hair cells, the resultant reduction in ular apparatus progressively loses hair cells long-term complications due to poor control. sensory input to the brain may explain why – some people aged 70 years or over experi- Nursing Times; 113: 4, 45-48. prebycusis and tinnitus often coexist. ence up to 40% reduction in hair cells in the Kujawa SG, Liberman MC (2006) Acceleration of age-related hearing loss by early noise exposure: There is mounting evidence that expo- semi-circular canals (Rauch et al, 2001). evidence of a misspent youth. Journal of sure to loud sounds throughout life can Other notable changes are the progres- Neuroscience; 26: 7, 2115-2123. both accelerate age-related hearing loss sive fragmentation and degeneration of the Liang L et al (2011) Ocular surface morbidity in eyes with senile sunken upper eyelids. and increase the risk of tinnitus. It is a con- otoliths (tiny stones made of calcium car- Ophthalmology; 118: 12, 2487-2492. cern to audiologists that growing numbers bonate), particularly in the saccule. The Liu TC, Chen YS (2000) Aging and external ear of young people attend loud concerts and number of vestibular nerve cells also resonance. International Journal of Audiology; 39: 5, 235-237. listen to loud music through headphones diminishes from around the age of Parham K et al (2011) Challenges and for long periods – this is likely to accelerate 60 years. These changes mean that, with opportunities in presbycusis. Otolaryngology their hearing loss and lead to hearing prob- age, our sense of balance becomes impaired – Head and Neck Surgery; 144: 4, 491-495. Rauch SD et al (2001) Decreasing hair cell counts lems and deafness much earlier in life and we may experience dizziness. Poor bal- in aging humans. Annals of the New York Academy (Kujawa and Liberman, 2006). ance and dizziness, together with frailty of Sciences; 942: 220-227. and reduced reaction times, contribute to Rukmini AV et al (2017) Pupillary responses to short-wavelength light are preserved in aging. Diminished sense of balance the risk of falls – a major concern in older Scientific Reports; 7: 43832. The ability to balance the body at rest (static people. Each year an estimated 20-40% of Shupert C, Horak F (2017) Balance and Aging. balance) and when moving (dynamic bal- those aged 65 and over fall at home (Shu- Portland, OR: Vestibular Disorders Association. Bit.ly/ShupertBalance ance) relies on a complex interplay between pert and Horak, 2017). Sobel RK, Tienor B (2013) The coming age of different sensory systems including sight, enophthalmos. Current Opinion in Ophthalmology; Regular testing 24: 5, 500-505. Sogebi OA (2015) Middle ear impedance studies in While little can be done to avoid the effects of elderly patients: implications on age-related hearing Anatomy and physiology of ageing on sight and hearing, it is vital to loss. Brazilian Journal of Otorhinolaryngology; 81: 2, ageing – updated series encourage older people to have regular eye 133-140. Truscott RJW (2003) Human cataract: the and hearing tests (Box 1). This means appro- mechanisms responsible; light and butterfly eyes. Article Date priate glasses and/or hearing aids can be dis- International Journal of Biochemistry and Cell Part 1: the cardiovascular system Feb pensed, and common age-related patholo- Biology; 35: 11, 1500-1504. (2008) Circadian Part 2: the respiratory system Mar Turner PL, Mainster MA gies such as cataracts, ARMD, and conductive photoreception: ageing and the eye’s important Part 3: the digestive system Apr and sensory hearing loss can be diagnosed role in systemic health. British Journal of Part 4: the renal system May early. Many people now have their eyes and Ophthalmology; 92: 11, 1439-1444. Part 5: the nervous system Jun Weinstein BE (2000) Geriatric Audiology. New hearing tested by high-street optometrists Part 6: the eyes and ears Jul York, NY: Thieme. Part 7: the endocrine system Aug in addition to relying on GP referrals. Part 8: the reproductive system Sep People who have diabetes and hyperten- For more on this topic go online... the immune system Oct sion need tests more often because both Part 9: l A communication protocol to help Part 10: the musculoskeletal system Nov conditions can adversely affect sight and patients with sensory impairment Part 11: the skin Dec hearing. People with a family history of Bit.ly/NTSensoryImpairment glaucoma should also be encouraged to

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