A cataract is defined as any opacity in the crystalline lens of the eye. It can affect one or both eyes. The changes to the transparency and refractive index of the lens result in various levels of visual impairment. This impairment is associated with decreased quality of life because it may restrict the person's ability to carry out daily activities and function independently, while increasing the risk of accidents and falls.
Cataracts most commonly affect adults as a result of biological ageing (age-related cataracts) and may be classified according to the area of the lens that is affected (nuclear sclerotic, cortical or posterior subcapsular cataracts). Cataracts can also occur in children, and may be classified according to the age of onset (congenital or infantile/juvenile cataracts). This guideline only covers cataracts in people who are 18 years or older.
Cataracts may occur secondary to hereditary factors, trauma, inflammation, metabolic or nutritional disorders, and exposure to radiation. In addition, lifestyle factors such as tobacco smoking and high alcohol intake are associated with an increased risk of developing age-related cataracts. Most cataracts are progressive, although the decline in visual function may be variable and unpredictable. The natural history of cataracts depends on the type and severity of the cataract and the presence of comorbid ocular conditions. In severe, untreated cases, cataracts can lead to significant reduction in vision, which is reversible with cataract surgery, although some level of visual impairment may persist.
Cataract surgery has a high success rate in improving visual function, with low morbidity and mortality. It is the most common operation performed in the NHS, with an ever growing need as the population ages.
Cataract management usually involves a multidisciplinary team that includes ophthalmologists, optometrists, nurses and technicians. Diagnosis is usually based on self-reported symptoms and a series of tests performed by an optometrist, normally based in the community. Symptoms may include blurred vision, difficulty seeing at night, sensitivity to light or glare, seeing 'halos' around lights and double vision in a single eye. Diagnostic tests include a visual acuity test, and slit-lamp and retinal examinations.
In adults with early age-related cataracts, non-surgical management may include prescription of spectacles. Alternatively, adults with age-related cataracts may be referred for surgery by an optometrist or a GP. The clinical threshold used to access cataract surgery varies across NHS trusts in England. This has resulted in differences in access to cataract surgery, because policies vary in scope and content and are not necessarily consistent with research evidence or guidance provided by the Department of Health in Action on cataracts and the Royal College of Ophthalmologists' Cataract surgery guidelines.
Guidance on appropriate referral criteria for cataract surgery is needed to address patient need and to optimise the allocation of NHS resources. In addition, an understanding of the most clinically and cost-effective methods for undertaking cataract surgery, and recommendations to minimise complications and surgical errors such as wrong intraocular lens implants, are needed to further improve patient care.