A range of problems can compromise our eyesight. Steve Titmarsh considers common conditions and how they can be managed... 
 
 
Age-related macular degeneration (AMD) describes changes to the central part of the retina (macula) which are often seen in people over 50 years of age. These include: 

• accumulation of lipid material beneath the retinal pigment epithelium
• areas of hypopigmentation or hyperpigmentation
• degeneration of light-sensitive cells in the macula, or the development of new blood vessels in the choroid which bleed or leak blood
• components, leading to retinal distortion and scarring, known as neovascular (exudative) AMD.1 

People with AMD may complain of distorted vision - straight lines may appear crooked or wavy, for example. There may be painless loss or blurring of central or near central vision, or a black or grey patch affecting the central field of vision (scotoma).  
 
Other warning signs are difficulty in reading, driving, or seeing fine detail such as facial features. Sufferers may see flickering or flashing lights (photopsia), and have difficulty adjusting from bright to dim lighting, or even visual hallucinations, which is associated with severe visual loss.1 
 
The greatest risk of visual impairment is associated with advanced AMD, where there is a 22–50 per cent risk of developing advanced AMD in the other eye at 5 years.1 Severe visual loss can develop within weeks or months in people with neovascular AMD.  
 
Urgent referral is needed if AMD is suspected as prompt treatment can preserve eyesight. Intravitreal injection of antivascular endothelial growth factor (VEGF) drugs improves vision in around 1 in 3 people. The majority maintain their vision and although about 10 per cent of patients do not respond.1 
 
Cataracts 
Cataracts cause the lens of the eye to become opaque as a result of accumulation of protein following disruption of the crystalline fibres that form the main lens structure.  
 
Another factor contributing to the development of cataracts is a build-up of yellow-brown pigment in the lens that happens with age. The pigment affects colour vision but not the sharpness of images so can eventually make reading difficult.2  
 
Eye disease, such as chronic anterior uveitis or acute congestive angle-closure glaucoma, can also result in cataract formation, as can trauma. Diabetes, atopic dermatitis and myotonic dystrophy are associated with an increased risk of cataracts.3  
 
Treatment with corticosteroids and exposure to ultraviolet light can increase the risk of cataracts. Female gender, hypertension and smoking tobacco are also risk factors.3 Symptoms include: 

• gradual and painless loss of sharpness and clarity of vision
• difficulty reading and/or watching television
• sensitivity to light and glare
• difficulty seeing at night
• difficulty recognising faces
• diplopia in one eye, and seeing haloes around lights.2,3 

Initially the effect of cataracts on vision can be ameliorated with prescription glasses and brighter reading lights. However, eventually cataracts will progress so surgery is needed to remove them.4 For people with no other eye problems, surgery will help the majority (95 per cent) regain eyesight that meets the UK driving test standard (6/12 best corrected vision). However, they will need glasses after surgery, even if they did not need them before, because the lenses used to replace those affected by cataracts are fixed focus.2,5 
 
Glaucoma 
In glaucoma the optic nerve is damaged, often by increased intraocular pressure (above 21mmHg). Reduced drainage of aqueous humour is thought to be the principal cause.6 
 
Age and family history are key risk factors for glaucoma and the condition is two to three times more common in black people than in white. Corticosteroid use and type 2 diabetes are associated with increased risk of the disease, as are hypertension and cardiovascular disease.6 
 
There are two main types of glaucoma – open angle and angle closure. Primary open angle glaucoma (POAG) is the most common type.6 
 
Loss of peripheral vision is the first noticeable effect of glaucoma, with central vision loss later. About 5–10 per cent of people with POAG will eventually become blind. Treatment delays progression of the condition and prevents most people from becoming blind.6 
 
People with acute closed angle glaucoma are at risk of very sudden changes in their vision. In the early stages vision may seem misty. Rainbow-coloured rings may be seen around white lights, or the eyes may ache, especially in the evening. 
 
A sudden increase in eye pressure can be very painful and immediate treatment is needed. Once pressure is under control, laser treatment (peripheral iridotomy) is used to prevent further attacks. For most people the treatment results in almost complete recovery of sight.7 
 
Eye drops containing a prostaglandin analogue, prostamide or beta-blocker are recommended as first-line treatment for POAG. Sometimes a second drug, such as a topical sympathomimetic, a topical carbonic anhydrase inhibitor or a topical miotic is added. In some cases where drug treatment does not work laser treatment may be offered to puncture the trabecular meshwork (situated where the iris and cornea meet) allowing better drainage of the aqueous humour.6,7 
 
Diabetic retinopathy 
A number of eye conditions are associated with diabetes, the most common being diabetic retinopathy. The cause is unknown, but it is linked to how long a person has had hyperglycaemia and its severity.8 
 
Patients experience a painless slow reduction in central vision. Management to delay progression of the condition is primarily through improving diabetes control along with controlling blood pressure and lipids. A balanced diet, exercise and stopping smoking are also beneficial.8  
 
Most people with diabetic retinopathy do not need treatment per se, but if they do options include laser treatment; intravitreal steroids; anti-vascular endothelial growth factor, and surgery.8 
 
Left untreated, retinopathy will lead to loss of sight in half of those with proliferative diabetic retinopathy within two years, and 90 per cent of sufferers will lose any useful vision within 10 years. Treatment can reduce the risk of moderate visual loss from 30 per cent to 15 per cent over three years.8  
 
Dry eye syndrome 
Dry eye syndrome is a result of under-production or over-evaporation of tear fluid or tear fluid composition.9 
 
Blepharitis, allergic conjunctivitis and drug adverse effects may cause a reduction in tear production. Tear evaporation may be increased by the low humidity caused by central heating or air conditioning, or by windy conditions. A low blink rate, which might result from looking at a computer for long periods,) or allergic conjunctivitis are other possible causes.9 
 
People with dry eyes may complain of grittiness in their eyes, or the feeling that something is in their eye. After any aggravating factors such as prolonged screen time and adverse drug reactions have been addressed, tear substitutes are the main form of treatment for mild disease. Preservative-free preparations should be recommended for prolonged or frequent (more than 4–6 times daily) use and for people who cannot stop using contact lenses.9 
 
Elvy Mardjono, senior brand manager for Rohto Dry Aid, said: “Many people suffer one or more of the eight main symptoms of dry eye - dryness, soreness, itchiness, irritation, burning, grittiness, stinging and tiredness - but they do not realise that they have the condition.” 

References

1. Clinical Knowledge Summaries (CKS). Macular degeneration – age-related https://cks.nice.org.uk/topics/macular-degeneration-age-related; accessed 7 May 2021). 
2. Lowth M, Tidy C. Cataracts and cataract surgery (https://patient.info/doctor/cataracts-and-cataract-surgery; accessed 7 May 2021). 
3. Clinical Knowledge Summaries (CKS). Cataracts (https://cks.nice.org.uk/topics/cataracts/background-information/causes-risk-factors; accessed 7 May 2021). 
4. NHS.UK. Age-related cataracts (www.nhs.uk/conditions/cataracts; accessed 7 May 2021). 
5. Oxford Radcliffe Hospitals NHS Trust. Choice of lens and glasses after your cataract surgery. Information for patients www.ouh.nhs.uk/patient-guide/leaflets/files/090427cataractsurgery.pdf; accessed 7 May 2021). 
6. Clinical Knowledge Summaries. Glaucoma (https://cks.nice.org.uk/topics/glaucoma/background-information; accessed 7 May 2021). 
7. Royal College of Ophthalmologists. Understanding Glaucoma (www.rcophth.ac.uk/wp-content/uploads/2017/10/2017_Understanding-Glaucoma.pdf; accessed 7 May 2021). 
8. Tidy C, Cox J. Diabetic retinopathy and diabetic eye problems (https://patient.info/doctor/diabetic-retinopathy-and-diabetic-eye-problems; accessed 7 May 2021). 
9. Harding M, Huins H. Dry eyes (https://patient.info/doctor/dry-eyes-pro; accessed 7 May 2021).