Cataracts
By The Treatment Registry editors
Clouding of the natural lens of the eye, most commonly age-related but also occurring after trauma, with diabetes, with prolonged steroid use, or congenitally. Cataracts produce gradually worsening blurred vision, glare sensitivity, and difficulty with night driving. Treatment is overwhelmingly surgical (phacoemulsification with intraocular lens implantation); there is no effective non-surgical treatment for established cataracts.
Clinical overview
Signs and symptoms
The signs and symptoms of cataract depend on which part of the lens is affected and how; mild lens opacity may produce no symptoms at all. As clouding worsens, symptoms include blurred vision, short-sightedness, astigmatism, difficulty with night vision, sensitivity to light, double vision in one eye, faded colours, and reduced contrast and colour vision, along with halos around lights or loss of part of the visual field. Worsening visual impairment can interfere with everyday tasks and driving, reduce physical activity and independence, and increase the risk of falls and associated injuries; reduced functioning may also contribute to mental-health difficulties.
Causes and risk factors
Cataract is most commonly age-related: lens proteins denature and degrade over time, a process accelerated by diabetes mellitus and hypertension. Formation is primarily driven by oxidative stress and lipid peroxidation, which damage lens proteins and lead to their aggregation and to the accumulation of protein clumps or yellow-brown pigment, reducing light transmission to the retina; imbalances in calcium and other ions also contribute. Risk factors include diabetes, longstanding corticosteroid use, smoking, prolonged sunlight (especially UVB) exposure, alcohol, poor nutrition, obesity, chronic kidney disease, and autoimmune disease. Cataracts may also follow blunt or penetrating trauma and ionising or non-ionising radiation, or arise congenitally through genetic and chromosomal disorders.
How it is diagnosed
Cataracts are usually diagnosed through an eye examination, with ophthalmoscopy and slit-lamp examination the most effective methods. During ophthalmoscopy the pupil is dilated and the red reflex is examined for opacities in the lens, while slit-lamp examination gives further detail on the cataract's characteristics, location, and extent. Age-related cataracts are classified histologically as nuclear sclerosis (the most common type), cortical, and posterior subcapsular. They may also be graded using the Lens Opacities Classification System (LOCS III), which classifies cataracts by type and by severity on a scale from 1 to 5.
Who it affects
In 2020 cataracts caused 39.6 per cent of all cases of blindness and 28.3 per cent of visual impairment worldwide, and they remain the single most common cause of global blindness; age-related cataracts account for about 51 per cent of world blindness, some 20 million people. In the United States, age-related lens changes have been reported in 42 per cent of people aged 52 to 64, 60 per cent aged 65 to 74, and 91 per cent aged 75 to 85, and by age 80 more than half of Americans have cataracts.
Clinical overview sourced from encyclopaedic medical reference; see sources below. General information only — not a substitute for individual clinical assessment.
Treatment ladder
Conservative options are first-line where appropriate; surgical options are typically reserved for cases where lower-tier options are unsuitable or have failed. Decisions are individual and depend on clinical assessment.
Conservative
- Updated spectacle prescription
May provide modest improvement in early cataracts but does not halt progression. First-line for symptomatic patients not yet at surgical threshold.
- Brighter lighting and anti-glare strategies
Practical mitigation for early cataract symptoms; not disease-modifying.
Procedural
- Phacoemulsification with IOL implantation
Standard cataract surgery: ultrasonic fragmentation of the cataractous lens and aspiration through a small incision, followed by implantation of an intraocular lens (monofocal, multifocal, or toric). Outpatient procedure under topical anaesthesia. The most commonly performed surgical procedure worldwide.
- Femtosecond laser-assisted cataract surgery (FLACS)
Femtosecond laser performs the corneal incision, capsulotomy, and initial lens fragmentation. Theoretical precision advantages; comparative outcome data with conventional phacoemulsification remain mixed.
Surgical
- Extracapsular cataract extraction (ECCE) — for dense/complex cataracts
Larger-incision removal of the lens nucleus in one piece. Reserved for very dense cataracts unsuitable for phacoemulsification, or in resource-limited settings.
Related procedures
Sources
- [1]American Academy of Ophthalmology — Preferred Practice Patterns including Refractive Surgery — aao.org(accessed 2026-05-09)
- [2]Wikipedia — Cataract — en.wikipedia.org(accessed 2026-07-24)
Sources marked “on file” are held by The Treatment Registry but are not publicly accessible.