Introduction
Physiological changes in the eye with ageing
Diseases of the eye related to ageing
Theories behind age-related eye diseases
Prevention measures and follow-ups
References

 

 

Introduction

Change is the only constant thing in life. Just like the rest of our body, our eyes change as they age. While it is not as obvious as our height, our hair or skin, it still undergoes dramatic changes as we advance in age.

From the age of 40 years, we will probably notice that our vision is changing. This may mean that one needs spectacles to see up close or one has a problem adjusting to glares or differentiating between some colours. These changes are a normal part of ageing. Despite these changes, one can still live an active lifestyle even in advanced stages of age without even noticing a severe visual impairment.

However, age is a major risk factor for developing age-related eye diseases. Disease processes like age-related macular degeneration, cataract, diabetic eye disease, glaucoma, dry eyes are common examples.1

 

Physiological changes in the eye with ageing

There are plenty of benign changes that can affect our eyes as they age, while these can reduce our eye’s optimum functioning, they don’t necessarily cause vision loss. Presbyopia is the condition where the lens loses it flexibility to focus on nearby objects.2 As a consequence, it becomes more difficult to read from a normal reading distance or see objects up close. Reading glasses are often needed to bring images into focus.

The sclera might turn yellow or brown in colour due to the exposure to sun and weather elements. It can also turn bluish because it becomes more transparent with age. The muscles that move our lower eye lids decrease in strength as we age. That, combined with the effect of gravity, can cause the lower eye lid to sag and turn outward, a condition called ectropion.3 It can sometimes turn inward causing our eyelashes to rub against the surface of the eye, a condition called entropion.

As the ocular surface is continuously exposed to sun light, UV rays induce oxidative stress in the conjunctival and corneal epithelium. This can give rise to a pterygium; a triangular benign tumour of the cornea that typically arises from the nasal margin and grows towards the pupil. It doesn’t usually require treatment unless it impairs vision. Avoidance of sunlight and wearing sunglasses is recommended. UV light can also cause conjunctival chalasis, which refers to loosening of the conjunctiva creating a redundant conjunctival tissue. This can be asymptomatic, but can sometimes lead to surface irritation or obstruction of tear flow. A grey-blue ring is sometimes seen in the corneal margin (or high iris periphery) of the elderly, this is called Arcus senilis.2 It results from cholesterol deposition in corneal stroma and can be a sign of hypercholesterolemia.

 

Dry eyes

Dry eyes are also common in old age.4 This tends to happen due to the reduced tear production by the tear glands or a change in the consistency of the tear film causing it to evaporate easily. Tear production is important to keep the surface of the eye moist. If tear production is reduced or ineffective in keeping the eyes moist, patients are likely to complain of eye irritation, soreness or perversely excessive, though ineffective, tear production.

The pupil of the eye tends to become smaller with age. This is because of the muscles that control its size that weaken as we age. This also makes it more sluggish to react to changes in light. It doesn’t dilate quickly enough in the dark or constrict quick enough in well-lit conditions. This is why elderly people can’t accommodate well to the dark and can be dazzled initially when going outdoors.

 

Floaters

Floaters are deposits of various size, shape and motility within the eye’s vitreous humour, which is normally transparent, but as one ages, imperfections gradually develop. The common type of floater, which is present in most persons’ eyes, is due to degenerative changes of the vitreous humour. However, it can also indicate a serious eye pathology like posterior vitreous detachment and retinal detachment, which requires urgent medical attention as it can easily cause visual loss.

 

Diseases of the eye related to ageing

Age related macular degeneration

Age related macular degeneration (AMD) is one of the most common age-related eye diseases. Patients report loss of the central part of the visual field; it starts with distortions in central vision until it is severely distorted or lost. While the person affected doesn’t usually develop complete blindness, the central part of vision is needed for daily tasks like reading or driving or even recognising faces, thus AMD places a significant impact on the patients’ daily activities. They would also suffer from trouble discerning dark colours from each other and light colours from each other and might suffer from slow vision recovery after exposure to bright light. Besides age,5 smoking and genetics play a role and increase the risk of developing the disease. Dry AMD (non-exudative AMD) is a broad classification, it encompasses all forms of AMD that are not neo-vascular (wet AMD). Like early and intermediate forms of AMD, it accounts for 80–90% of AMD cases and tends to progress slowly with minimal symptoms in early stages. Unfortunately, there is no medical or surgical management for dry AMD.

Wet AMD on the other hand (exudative AMD) occurs when there’s an abnormal growth of blood vessels that would leak blood and proteins due to their fragility and ultimately affect vision. Laser photocoagulation and anti-VEGF injections are the mainstay of treatment and will help stop the progression of the disease.

 

Cataract

Cataract occurs when the lens becomes less transparent to light and causes the image to look blurred, with faded colours and lots of glare. The lens consists of water and proteins. These proteins tend to aggregate together with age, causing small clumps throughout the lens. This impedes the transition of light and affects the overall quality of vision. That could affect the nucleus of the lens and is thus called Nuclear Cataract, which occurs mainly with ageing. It can also affect the cortex (outermost layer of the lens) and is called cortical cataract. Or it affects the back of the lens, called sub capsular cataract, which occurs primarily in diabetics or patients on steroid medications. Other causes of cataract include trauma, radiation, genetics, smoking and medications. Cataract can be fixed by changing the lens for an artificial one (IOL) and this is very common (approximately 99.7%)6 in the UK.

There are different methods of doing that, of which, phacoemulsification (phaco) is the most common and includes using a high frequency ultrasound waves to emulsify the lens and fragment it, then extract it through a small corneal side incision. The artificial lens is then inserted through that incision afterwards.

 

Glaucoma

Glaucoma occurs when the increased intra-ocular pressure compresses the optic nerves inside the eye and damages them. The increased pressure can happen because of the poor drainage of the aqueous humor inside the anterior chamber of the eye causing it to accumulate and the pressure to rise. However, glaucoma can still take place even if the pressure inside the eye is not elevated. The aetiology is not fully understood,7 but it is thought to be due to the presence of fragile eye nerves or reduced blood flow to them making them susceptible to pressure effects. People affected tend to lose the outside of the visual field (the peripheries), as if they are looking through a cylinder, but the central vision is preserved which is why it is called ‘tunnel vision’.

Treatments include medications that help lower intraocular pressure, eg. prostaglandin analogues and procedures like laser trabeculoplasty, canaloplasty and trabeculectomy, which is the most common of them and involves removing a portion of the trabecular meshwork to allow the fluid to flow out easily.

 

Diabetic retinopathy

Diabetic retinopathy is the leading cause of blindness. It commonly affects the microvasculature of the retina that swells and leak because of the changes that high levels of glucose induce in their walls. New abnormal tiny vessels can grow when areas of the retina lack vasculature. Because these vessels are abnormal in shape and are fragile, retinal haemorrhage can result.

Patients may complain of irregular spots of visual loss or dark flecks. The centre of vision on the retina, the macula, can swell and cause blurring of vision, which can rapidly deteriorate into vision loss. Moreover, diabetes itself is also risk factor for developing glaucoma and cataract. Tight glycaemic control and regular eye checkups are recommended to help slow the progression of the disease.

 

Hypertensive retinopathy

Hypertensive retinopathy is another common disease. It often goes undetected because patients are usually asymptomatic. In later stages, patients might complain of headaches or blurred vision. Early changes include arteriolar narrowing and arteriovenous nicking, advanced stages include flame haemorrhages, cotton-wool spots and disc oedema. Management is primarily preventative, target blood pressure of below 140/90mmhg is recommended, but no surgical treatment is available for the ocular complications.

 

Theories behind age-related eye diseases

There are theories they might explain why these changes occur. One theory called the biological clock theory8 or the programmed theory focuses on the genetic programming of our DNA that we inherit from out parents and ancestors.

It is in that DNA you find the coding to how our bodily functions are programmed. And it is thought that we are programmed to self-destruct as we age. That our biological clock is set to go off at a certain age and the ageing process begins from then, but this is largely affected by the environment that surrounds us as we age and can affect when the clock goes off.

Another theory, which seems more acceptable, called the theory of Error.8 It basically suggests that as we age, our body cells lose their ability to regenerate and repair errors in their structure. This is because of the excessive wear and tear that happens to our cells due to the exposure to the various harms in our environment from sunlight to diet to pollution. This causes the body to accumulate abnormal molecules called free radicals, which are destructive to our body cells and their precipitation ultimately kills them.

 

Prevention measures and follow-ups

While we can’t, unfortunately, stop the ageing process. We definitely can reduce the extent of ageing on vision, and most importantly, the modifiable risk factors. Maintaining a healthy lifestyle like diet and exercise is of an undeniable benefit. Avoiding the harmful effects of the ultraviolet light can definitely reduce the damaging effects of the sun. Maintaining tight blood sugar control for diabetics is proven to reduce the risk of diabetic retinopathy. Antioxidants like vitamin C, E and β carotene9 counteract the effects of free radicals and have shown benefit in the prevention of AMD. Regular eye checkups and surveillance visits to ophthalmologists can help detect early changes in the eye structure and potentially prevent the development of visual loss.

The NHS10 currently recommends a routine checkup every two years for ages 60 and above. The frequency can increase depending on the individual eye problem and the optometrist or ophthalmologist will be able to advise as to how often a patient needs to be seen.

 

Mohammed Mohammed, FY2 Doctor, Manchester Foundation Trust hospitals

Mr Ali Yagan, Consultant ophthalmic surgeon, Manchester Royal Eye hospital

Conflict of interest: none declared

 


References

1. Forrester J V. Aging and vision. Br J Ophthalmol 1997; 81: 809–810

2. Duncan G, Wormstone IM, Davies PD. The aging human lens: structure, growth, and physiological behaviour. Br J Ophthalmol 1997; 81: 818–23

3. James Garrity, MD, Whitney and Betty MacMillan Professor of Ophthalmology, Mayo Clinic College of Medicine, Effects of Aging on the Eye. www.MsdManuals.com

4. National Eye Institute. Age related Eye Diseases. https://nei.nih.gov/healthyeyes/aging_eye

5. Grunwald J E, Piltz J, Patel N. Effect of aging on retinal macular microcirculation: a blue field simulation study. Invest Ophthalmol Vis Sci 1993; 34: 3609–13

6. Royal National Institute of Blind People (RNIB) – December 2014

7. Weinreb RN, Aung T, Medeiros FA. The Pathophysiology and Treatment of Glaucoma: A Review. JAMA 2014; 3118: 1901–11

8. Salvi SM, Akhtar S, Currie Z. Ageing changes in the eye. Postgraduate Medical Journal 2006; 82(971): 581–87 doi:10.1136/pgmj.2005.040857

9. The Age‐Related Eye Disease Research Group: A randomized, placebo‐controlled, clinical trial of high‐dose supplementation with vitamins C and E, beta carotene, and zinc for age‐related macular degeneration and vision loss. AREDS report no 8. Arch Ophthalmol 2001; 119: 1417–36

10. NHS choices, How often can I have a free NHS eye test?. http://www.nhs.uk/chq/Pages/1093.aspx?CategoryID=68&SubCategoryID=157