Ageing Changes in the Eye

In the UK, the 2001 census revealed more people over 60 than children for the first time. About 21% of the population is over 60, with 1.1 million individuals aged 85 or older. As people age, their eye functions decline, along with the central visual system’s abilities like reception, storage, and analysis. 

We aim to understand what falls under “normal aging” in eye health, distinguishing it from actual diseases. The biological clock and wear-and-tear theories help explain these age-related changes, including those in the eyes.

Biological clock theory (Programmed theory)

The biological clock theory, the programmed theory, suggests that our DNA contains a predetermined plan for aging and lifespan. Like a ticking clock, this genetic programming determines when our bodies begin to age and ultimately die. However, the timing of this clock can vary greatly depending on both genetic factors and our environment and lifestyle (nature versus nurture). 

In essence, we are born with a genetic blueprint that influences how quickly we age, but external factors also play a significant role.

Wear and tear theory (Error theory)

The wear and tear theory, also known as the error theory, suggests that our bodies, including our eyes, deteriorate over time due to various factors like diet, environment, and stress. This theory was proposed by Dr. August Weismann in 1882.

Our organs, including the eyes, can be damaged by toxins in our diet and environment, as well as by unhealthy habits like excessive consumption of fat, sugar, caffeine, alcohol, and smoking. Even regular use of our organs can lead to wear and tear, which worsens with age.

One major factor in this process is the production of free radicals in the body. 

Free radicals are molecules with unpaired electrons that react destructively with other molecules, damaging cell membranes and interfering with cell repair and reproduction. This damage accumulates over time and contributes to aging, including in the eyes, which can cause dark spots and wrinkles.

Antioxidants are substances that help prevent this damage by neutralizing free radicals. Some natural antioxidants like vitamin C, E, and β carotene (which the body converts into vitamin A) can help protect against age-related eye conditions like macular degeneration.

Overall, the wear and tear theory suggests that our eyes, like the rest of our body, are subject to damage from various sources over time, leading to aging and potentially vision problems.

Ageing changes of the eyelids and lacrimal system

The eyelids and tear system change as we age, similar to those of other body parts. The tissues start to shrink, leading to loose and wrinkled skin. This can cause problems like droopy eyelids, sagging brows, and wrinkles around the eyes.

The skin becomes loose and lax in the lower eyelids, sometimes causing the eyelids to turn outwards (ectropion) or inwards (entropion). This can lead to tearing and discomfort. Surgery may be needed to correct these issues.

In the upper eyelids, the muscles responsible for lifting the eyelids may weaken, causing drooping (ptosis). Excess skin and fat can also accumulate, making the eyelids appear heavy. Surgery may be considered if these changes affect vision.

Wrinkles, like “crow’s feet,” may also develop around the eyes due to aging. Treatments like botulinum toxin injections can help reduce their appearance. Elderly individuals may experience watery eyes due to eyelid problems or blockages in the tear drainage system. Surgery can help in severe cases of tear blockage, while dry eyes caused by reduced tear production can be managed with artificial tears or plugs to keep tears in the eyes.

Corneal Changes

As people age, their corneas undergo various changes that can affect their vision. These changes include alterations in corneal curvature, decreased luster and sensitivity, increased fragility, and age-related dystrophic changes in the corneal epithelium, stroma, and endothelium.

One common alteration is a shift in astigmatism type, typically from “with the rule” to “against the rule.” This means the steepness of the cornea’s meridians changes, impacting how light is refracted. With “with the rule” astigmatism, horizontal lines may appear blurry, while vertical lines may be less precise with “against the rule” astigmatism.

Other notable changes include the development of pigmented lines like the Hudson‐Stahli line and yellow-white deposits called Arcus senilis. These deposits are composed of lipids and can form a ring-shaped opacity on the cornea.

Moreover, age-related dystrophic changes can lead to thickenings in the endothelium (Hassall-Henle bodies), pigment deposition (Kruckenberg spindle), and other alterations that may be observed during a slit lamp examination.

While these changes may not always cause vision problems, they can contribute to overall age-related visual decline. Therefore, regular eye check-ups are recommended for elderly individuals to ensure optimal vision and address developing issues.

Ageing in Retina

Our vision tends to decline as we age, with various aspects of visual function deteriorating over time. This decline includes decreased visual acuity, reduced sensitivity in the visual field, poorer contrast sensitivity, and a higher threshold for adapting to darkness.

These changes stem from a combination of factors affecting the neuronal components of the visual system, alterations in the eye’s media, and pupil constriction.

 Specifically, in the retina, which is crucial for vision, the retinal pigment epithelium (RPE) undergoes several age-related changes:

1. Increased variation in RPE cells’ shape (pleomorphism).
2. Reduction in the number of RPE cells in the central region of the retina.
3. Decreased melanin content in the RPE cells.
4. Accumulation of lipofuscin (a type of cellular waste) in the RPE.
5. Reduced volume of cytoplasm in the RPE cells.

Age-related macular degeneration

Age-related macular degeneration (AMD) is an eye condition where the retina’s central part deteriorates, affecting vision. In AMD, debris accumulates under the retina, forming drusen. Drusen can be hard or soft; soft Drusen increases the risk of severe vision loss.

Risk factors include aging, smoking, family history, and genetics. Other factors may include sunlight exposure, high blood pressure, and farsightedness.

Preventive measures include eating green leafy vegetables, quitting smoking, and taking specific vitamins. Some treatments like photodynamic therapy and injections are available for advanced cases, mainly for wet AMD, but they’re not always practical. Regular monitoring is crucial for early detection and management.

Functional changes

As we age, various changes affect our vision. One common issue is presbyopia, which makes it hard to focus on close objects. Additionally, early lens changes can cause glare, especially at night.

With age, contrast sensitivity decreases due to eye changes, making it harder to see in low light or distinguish between shades. This can affect depth perception, making steps or street curves challenging.

Color vision also declines, especially when telling blues and greens apart. Using warm colors like yellow, orange, and red can help older adults navigate better.

The aging lens absorbs more blue light, making objects appear yellow. Elderly individuals struggle to adjust to bright light or darkness and are sensitive to glare, making night driving difficult.

Conclusion

Age-related changes in the eye affect older adults’s quality of life. It’s crucial to distinguish between average age-related vision decline and vision problems caused by diseases. There may be ways to delay or stop age-related vision issues in the future.