Eyesight in the elderly

Original Editor - Wendy Walker

Top Contributors - Wendy Walker and Scott Buxton  

The Aging Eye

As we age, our sensory modalities (including vison) show gradual deterioration. Older people must adapt to problems such as reduced visual field, decrease in visual acuity, delayed dark adaptation, reduced colour perception and decreased power of accommodation resulting in presbyopia. Taken together, these different visual problems all lead to impairment of visual function.
Then in addition, a large number of older people also suffer from medical conditions affecting function of the eye, such as glaucoma, age related macular degeneration, diabetic retinopathy and cataracts.

As mentioned above as you age different sensory systems may become impaired, be it through diabetes and peripheral proprioception or vestibular systems through benign paroxysmal positional vertigo. As other systems are affected extra reliance can be place upon vision for a person to gain critical imformation from their surrondings in order to remain steady. It is important, therefore, that there is an extra-importance in aintaining visul acuity through regular eye appointments, in fact the NHS provides free annual eye tests to those above the age of 75. Such is the importance of eye sight and falls risk it is now part of the NICE falls guidelines.

Impairments of visual function

Visual field reductions

With aging there is a decrease in peripheral and upper visual fields. It is thought likely that in the early stages this may be as a result of decreased pupil size and therefore less light admitted to the peripheral retina; later on changes may result from decreased retinal metabolism. 

In addition loss of retrobulbar fat results in the eyes sinking more deeply into the orbits which leads to a mechanical restriction of upper gaze[1].

Functional effects:

  • reduced awareness of the lateral field of view can cause difficulties when driving
  • reduced upper visual field vision results in the individual being less aware of high traffic and street signs

Reduced visual acuity

Visual acuity is the ability of the eye to discriminate fine details of objects, and it frequently (not inevitably) declines with age.

An increase in the thickness of the lens combined with its loss of elasticity result in decreased ability to see clearly, and particularly affect near objects. In addition, with increased age the iris no longer changes width and pupil size remains small in both dim and bright light, resulting in detrioration in night vision. It is generally thought that other contributing factors are loss of photoreceptors within the retina and possibly changes in the geniculostriate pathway[2].

Functional effects:

  • need for reading glasses or contact lenses
  • may require hand-held magnifiers when doing sewing or craft work

Accommodation difficulties

Accommodation = the ablity of the eye to focus images on the retina independent of object distances.

With age both the cornea and the lens lose transparency, the lens thickens and becomes more rigid and the ciliary muscle weakens. All of which cause the lens to gradually lose its ability to change shape and focus at varyig distances[3].

This is generally labelled presbyiopia, which means "old eye".

Functional effects:

  • initially require reading glasses
  • later bifocals or varifocals are frequently required as focusing on even distant objects is impaired

Reduced colour perception

With increased age, changes in the retinal cones and the visual pathways, as well as in the lens, lead to the eye becoming less sensitive to colours that have shorter wavelngths, ie. blues, greens and violets (the cooler colours).

In addition, pale pastel colours may become more difficult to distinguish, as may varying shades of grey.

Functional effects:

  • may struggle to see furniture if not brightly coloured or in bright light, so can bump into it leading to falls

Slower dark adaptation

The ability of the eye to become more visually sensitive after remaining in darkness for a period of time is delayed in older people.

Metabolic changes in the retina result in reduced oxygen supply to the rod-dense area of the retina and the reduction in pupil size both contribute to this problem[4].

Functional effects:

  • difficulty adapting to darkness, especially abrupt and extreme changes in light levels
  • risk of falls at night or in low light situations

Medical eye conditions affecting older people

Macular Degeneration

Age-related macular degeneration (AMD) is a common, polygenic disease in which multiple genetic variants as well as environmental, lifestyle factors contribute to disease risk, each adding a small to moderate amount of increased risk[5]. The risk of developing the disease is three-fold higher in people who have a family member with AMD than in those without a first-degree relative with AMD[6].

Symptoms of AMD include:

  • Loss of central vision, with peripheral vision unaffected
  • Trouble discerning colours
  • Reduction in contrast sensitivity
  • Blurred vision
  • Slow recovery of visual function after exposure to bright light

Glaucoma

Glaucoma is currently defined as a disturbance of the structural or functional integrity of the optic nerve that causes characteristic atrophic changes in the optic nerve, which may also lead to specific visual field defects over time[7]. This disturbance usually can be arrested or diminished by adequate lowering of intraocular pressure (IOP).

Glaucoma is the second leading cause of blindness in the world[8] (surpassed only by cataract, see below, which is a reversible condition).

In glaucoma the loss of vision often occurs gradually over a long period of time, and symptoms only occur when the disease is quite advanced. Once lost, vision cannot normally be recovered, so treatment is aimed at preventing further loss.

Treatment can involve medications to lower intra-ocular pressure (IOP), laser or conventional surgery.

Cataracts

Senile cataract is a vision-impairing disease characterized by gradual, progressive thickening of the lens. It is one of the leading causes of blindness in the world today, and is treatable by surgery.

Senile cataract continues to be the main cause of visual impairment and blindness in the world. In recent studies done in China[9], India[10], Canada[11], Japan[12], and Denmark[13], cataract was identified as the leading cause of visual impairment and blindness, with statistics ranging from 33.3% (Denmark) to as high as 82.6% (India). Published data estimate that 1.2% of the entire population of Africa is blind, with cataract causing 36% of this blindness. In a survey conducted in 3 districts in the Punjab plains, the overall rates of occurrence of senile cataract was 15.3% among 1269 persons examined who were aged 30 years and older and 4.3% for all ages. This increased markedly to 67% for ages 70 years and older.

As a cataract worsens, it gradually reduces the amount of light entering the eye causing;

  • Blurring of vision
  • Glare in bright lights or when driving
  • A change in the spectacle prescription
  • Some doubling of vision
  • Colours appear to be faded
Photograph by Rakesh Ahuja, MD, from Wikipedia
Photograph by Rakesh Ahuja, MD, from Wikipedia.

Senile cataracts have been associated with a lot of systemic illnesses, to include the following: cholelithiasis, allergy, pneumonia, coronary disease and heart insufficiency, hypotension, hypertension, mental retardation, and diabetes.

Systemic hypertension was found to significantly increase the risk for posterior subcapsular cataracts.




Recent Related Research (from Pubmed)

References

  1. Melore GG: Visual function changes in the geriatric patient and environmental modifications. In Melore GG, editor: Treating vision problems in the older adult, St. Louis, MO, 1997, Mosby
  2. Spear PD: Neural basis of visual deficits during aging. Vision Res 33:2589–260, 1993
  3. Linton AD: Age-related changes in the special senses. In Linton AD, Lach HW, editors: Matteson & McConnell’s Gerontological nursing: concepts and practice, ed 3, Philadelphia, PA, 2007, Saunders/Elsevier
  4. Melore GG: Visual function changes in the geriatric patient and environmental modifications. In Melore GG, editor: Treating vision problems in the older adult, St. Louis, MO, 1997, Mosby
  5. Seddon JM, Sobrin L. Epidemiology of age-related macular degeneration. In: Albert D, Miller J, Azar D, Blodi B, eds. Albert & Jakobiec's Principles and Practice of Ophthalmology. Philadelphia, Pa: WB Saunders; 2007:413-422
  6. Seddon JM, Ajani UA, Mitchell BD. Familial aggregation of age-related maculopathy. Am J Ophthalmol. Feb 1997;123(2):199-206
  7. Bathija R, Gupta N, Zangwill L, Weinreb RN. Changing definition of glaucoma. J Glaucoma. Jun 1998;7(3):165-9.
  8. Kingman, Sharon (2004). "Glaucoma is second leading cause of blindness globally". Bulletin of the World Health Organization 82 (11): 887–8.
  9. You QS, Xu L, Yang H, Wang YX, Jonas JB. Five-Year Incidence of Visual Impairment and Blindness in Adult Chinese The Beijing Eye Study. Ophthalmology. Jan 4 2011
  10. Murthy GV, Vashist P, John N, Pokharel G, Ellwein LB. Prevelence and causes of visual impairment and blindness in older adults in an area of India with a high cataract surgical rate. Ophthalmic Epidemiol. Aug 2010;17(4):185-95.
  11. Maberley DA, Hollands H. The prevalence of low vision and blindness in Canada. Eye(Lond). 2006/03;20(3):341-6.
  12. Iwase A, Araie M, Tomidokoro A, Yamamoto T, Shimizu H, Kitazawa Y. Prevalence and causes of low vision and blindness in a Japanese adult population: the Tajimi Study. Ophthalmology. Aug 2006;113(8):1354-62
  13. Buch H, Vinding T, Nielsen NV. Prevalence and causes of visual impairment according to World Health Organization and United States criteria in an aged, urban Scandinavian population: the Copenhagen City Eye Study. Ophthalmology. Dec 2001;108(12):2347-57