Cataract overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1], Associate Editor-In-Chief: Joseph Nasr, M.D.[2]
A cataract is an opacification of the natural intraocular crystalline lens, or its capsule, which normally transmits and focuses light onto the retina in the posterior part of the eye. This opacification results in a progressive decrease in visual acuity and visual function and may lead to complete vision loss if left untreated. In the early stages of age-related cataract, changes in the refractive index of the crystalline lens may increase lens power, resulting in a myopic shift, while gradual yellowing and clouding of the lens can impair color perception, particularly of blue hues.
Cataracts typically progress slowly but are potentially blinding. In advanced cases, liquefaction of the lens cortex may result in a Morgagnian cataract, which can provoke severe intraocular inflammation if the lens capsule ruptures. Untreated cataracts may also lead to complications such as phacomorphic glaucoma. In very advanced disease, zonular weakness may result in anterior or posterior dislocation of the lens. Historically, spontaneous posterior dislocation of the lens occasionally restored limited light perception in bilaterally affected individuals.
Cataracts are the leading cause of blindness worldwide and the leading cause of preventable blindness.[1] Globally, cataracts accounted for approximately 15 million cases of blindness and 79 million cases of moderate to severe visual impairment among individuals aged 50 years or older in 2020.[2] In the United States, age-related lenticular changes have been reported in approximately 42% of individuals aged 52 to 64 years,[3] 60% of those aged 65 to 74 years,[4] and 91% of individuals aged 75 to 85 years.[3]
At present, there are no scientifically proven interventions to prevent cataract formation or progression. Although ultraviolet light exposure has been implicated as a risk factor, and the use of ultraviolet-protective sunglasses is sometimes suggested as a protective measure, definitive benefit has not been established.[5][6] Antioxidant supplementation, including vitamins C and E, has been proposed but has not been proven effective.
Cataract surgery is the only effective and approved treatment for cataracts. The procedure involves removal of the opacified crystalline lens, which develops due to metabolic changes within lens fibers over time, followed by implantation of an artificial intraocular lens (IOL). Cataract surgery is generally performed by an ophthalmologist in an ambulatory surgical center or hospital setting using local anesthesia, including topical, peribulbar, or retrobulbar techniques. More than 90% of cataract operations successfully restore useful vision, with a low complication rate,[7] and modern small-incision phacoemulsification with rapid postoperative recovery has become the standard of care worldwide. In the United States, cataract extraction with intraocular lens implantation is one of the most commonly performed surgical procedures, with approximately 3 million surgeries performed annually.
Visual acuity may not improve to 20/20 following cataract surgery if other ocular conditions, such as age-related macular degeneration, are present. In many cases, ophthalmologists can, but not always, identify these limiting factors preoperatively.
The term cataract is derived from the Latin cataracta, meaning “waterfall,” and the Greek kataraktēs or katarrhaktēs, from katarassein, meaning “to dash down.” The term likely originated from the resemblance of mature lens opacities to rapidly running white water, although in Latin it also referred to a “portcullis,” suggesting obstruction as an alternative etymologic origin.
References
- ↑ https://web.emmes.com/study/areds/mopfiles/chp2_mop.pdf
- ↑ GBD 2019 Blindness and Vision Impairment Collaborators; Vision Loss Expert Group of the Global Burden of Disease Study. Causes of blindness and vision impairment in 2020 and trends over 30 years, and prevalence of avoidable blindness in relation to VISION 2020: the Right to Sight: an analysis for the Global Burden of Disease Study. Lancet Glob Health. 2021;9(2):e144-e160. doi:10.1016/S2214-109X(20)30489-7
- ↑ 3.0 3.1 Sperduto RD, Seigel D. Sperduto RD, Seigel D. "Senile lens and senile macular changes in a population-based sample." Am J Ophthalmol. 1980 Jul;90(1):86-91. PMID 7395962.
- ↑ Kahn HA, Leibowitz HM, Ganley JP, Kini MM, Colton T, Nickerson RS, Dawber TR. "The Framingham Eye Study. I. Outline and major prevalence findings." Am J Epidemiol. 1977 Jul;106(1):17-32. PMID 879158.
- ↑ Epidemiology. 2003 Nov;14(6):707-12. Sun exposure as a risk factor for nuclear cataract
- ↑ http://www.nei.nih.gov/nehep/pdf/NEHEP_5_year_agenda_2006.pdf p.37 quoting Javitt, J. C., F. Wang, and S. K. West. “Blindness Due to Cataract: Epidemiology and Prevention.” Annual Review of Public Health 17 (1996): 159-77.
- ↑ University of Illinois Eye Center."Cataracts." Retrieved August 18, 2006.