Peter Francis, Institute of Ophthalmology, University College London, London, UK
Published online: January 2006
DOI: 10.1038/npg.els.0006105
The function of the crystalline lens of the eye is to focus light onto the retina. It has a unique structure, as lens cells are never shed but continually added throughout life. Cataract, or opacification, is by far the most common disorder affecting the lens.
Keywords: eye; lens; cataract; lenticonus; crystallin
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Figure 1. The adult lens consists of clinically discernible regions. (a) Lens viewed from anteroposterior. (b) Lens in cross-section.
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Figure 2. Lens development. In humans, lens organogenesis begins in the fourth week of gestation with thickening of the surface ectoderm overlying the optic vesicle (a) to form the lens placode; (b) this area begins to invaginate (the lens pit) and (c) eventually closes over to form the lens vesicle; (d) cells lining the posterior wall of the lens vesicle rapidly elongate to form the primary lens fibers (embryonic nucleus); (e) thereafter, throughout life, secondary lens fibers differentiate from equatorial epithelial cells, forming concentric lamellae around the embryonic nucleus.
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Figure 3. Autosomal dominant congenital cataract phenotypes. (a) Slit-lamp (above) and retroillumination (below) view of anterior polar cataract (47-year-old female). (b) Slit-lamp and retroillumination view of a stationary posterior polar cataract (49-year-old female). (c) Slit-lamp view of a progressive posterior polar cataract (9-year-old female). (d) Slit-lamp and retroillumination view of a dense nuclear cataract (14-year-old male). (e) Slit-lamp and retroillumination view of nuclear opacities (50-year-old female). (f) Slit-lamp and retroillumination view of the Coppock-like (pulverulent) cataract with fine nuclear opacities (24-year-old female). (g) Slit-lamp and retroillumination view of the Coppock-like cataract with dense central opacities (6-year-old female). (h) Slit-lamp view of lamellar cataract. (i) Slit-lamp view of a blue-dot (cerulean) cataract (32-year-old male). (j) Slit-lamp and retroillumination view of a cortical cataract (45-year-old female). (k) Slit-lamp view of a fine pulverulent cataract (32-year-old male). (l) Slit-lamp view of large pulverulent opacities (12-year-old female).
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| References | |
| book Albert D and Jakobiec F (1994) Principles and Practice of Ophthalmology. Philadelphia, PA: WB Saunders. | |
| book Elkington A and Frank H (1984) Clinical Optics. Oxford, UK: Blackwell. | |
| Evans J, Rooney C, Ashwood F, Dattani N and Wormald R (1996) Blindness and partial sight in England and Wales: April 1990–March 1991. Health Trends 28: 5–12. | |
| Francis P, Berry V, Moore A and Bhattacharya S (1999) Lens biology, development and human cataractogenesis. Trends in Genetics 15: 191–196. | |
| Hammond C, Sneider H, Spector TD and Gilbert CE (2000) Genetic and environmental factors in age-related nuclear cataracts in monozygotic and dizygotic twins. New England Journal of Medicine 342(24): 1786–1790. | |
| Kannabiran C, Rogan P, Olmos L, et al. (1998) Autosomal dominant zonular cataract with sutural opacities is associated with a splice mutation in the A3/A1-crystallin gene. Molecular Vision 4: 21. | |
| other McKusick V (1997) Online Mendelian Inheritance in Man, OMIM. Centre for Medical Genetics, John Hopkins University (Baltimore, MD) and National Centre for Biotechnology Information, National Library of Medicine (Bethesda, MD). 1998. | |
| Pal J, Liu X, Mackay DA, et al. (2000) Connexin46 mutations linked to congenital cataract show loss of gap junction channel function. American Journal of Cell Physiology 279(3): C596–C602. | |
| Piatigorsky J (1998) Multifunctional lens crystallins and corneal enzymes. More than meets the eye. Annals of the New York Academy of Sciences 842: 7–15. | |
| Pras E, Levy-Nissenbaum E, Bakhan T, et al. (2002) A missense mutation in the LIM2 gene is associated with autosomal recessive presenile cataract in an inbred Iraqi Jewish family. American Journal of Human Genetics 70: 1363–1367. | |
| Further Reading | |
| book Duke-Elder S (1978) The Practice of Refraction Edinburgh, UK: Churchill Livingstone. | |
| Ionides A, Francis PJ, Berry V, et al. (1999) Clinical and genetic heterogeneity in autosomal dominant congenital cataract. British Journal of Ophthalmology 83(7): 802–808. | |
| book Johnson GJ and Foster A (1998) Prevalence, incidence and distribution of visual impairment. The Epidemiology of Eye Disease, pp. 8–9. London, UK: Chapman & Hall. | |
| Krutovskikh V and Yamasaki H (2000) Connexin gene mutations in human genetic diseases. Mutation Research 462(2–3): 197–207. | |
| book Lambert S (1997) Lens. Paediatric Ophthalmology. Oxford, UK: Blackwell Scientific. | |
| Piatigorsky J (1998) Gene sharing in lens and cornea: facts and implications. Progress in Retina and Eye Research 17(2): 145–174. | |
| book Snell RS and Lemp MA (1989) Clinical Anatomy of the Eye, pp. 1–9. Oxford, UK: Blackwell Scientific. | |
| Web Links | |
| ePath crystallin, A (CRYAA); LocusID: 1409. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=1409 | |
| ePath crystallin, B2 (CRYBB2); LocusID: 1415. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=1415 | |
| ePath crystallin, C (CRYGC); LocusID: 1420. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=1420 | |
| ePath gap junction protein, 8 (GJA8); LocusID: 2703. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=2703 | |
| ePath lens intrinsic membrane protein 2 (LIM2); LocusID: 3982. LocusLink: http://www.ncbi.nlm.nih.gov/LocusLink/LocRpt.cgi?l=3982 | |
| ePath crystallin, C (CRYGC); MIM number: 123680. OMIM: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?123680 | |
| ePath crystallin, A (CRYAA); MIM number: 123580. OMIM: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?123580 | |
| ePath crystallin, B2 (CRYBB2); MIM number: 123620. OMIM: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?123620 | |
| ePath gap junction protein, 8 (GJA8); MIM number: 600897. OMIM: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?600897 | |
| ePath lens intrinsic membrane protein 2 (LIM2); MIM number: 154045. OMIM: http://www.ncbi.nlm.nih.gov/htbin-post/Omim/dispmim?154045 | |
| ePath Online Mendelian Inheritance in Man (OMIM). Database of human genes and genetic disorders made available online by the National Center for Biotechnology Information http://www.ncbi.nlm.nih.gov/Omim/ | |
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