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cataracts

An opacity of the crystalline lens of the eye; a loss of transparency of the lens of the eye or of its capsule. Etiology: (risk factors) 1) aging 2) systemic disorders a) diabetes mellitus b) hypoparathyroidism c) hypothyroidism d) obesity 3) genetic abnormalities 4) trauma 5) pharmacologic causes: a) busulfan b) chlorambucil c) glucocorticoids d) phenothiazines e) phospholine iodide 6) environmental a) diets low in antioxidants b) smoking c) UV radiation/sunlight d) ethanol Epidemiology: 1) 45-60% of individuals > 75 years of age - prevalence may approach 100% in persons age > 90 2) most common cause of reversible blindness in USA 3) 2nd most common cause of blindness in USA 4) among older diabetics, more common cause of visual disability than diabetic retinopathy 5) cataract extraction is the most frequently performed surgical intervention on the Medicare population 6) more common among persons with lower education & socioeconomic class Pathology: - damage to the major lens crystallin proteins causes their misfolding & aggregation into insoluble amyloids resulting in opacification of the crystalline lens [12] Genetics: - defects in CHMP4B associated with autosomal dominant cataract posterior polar type 3 Clinical manifestations: 1) diminished vision in one or both eyes 2) lenticular opacities 3) glare sensitivity [8] 4) generalized blurry vision [8] 5) diminished ability to see objects in dim light (contrast sensitivity) 6) myopic shift in eyeglass prescription [11,12] Laboratory: 1) ophthalmoscopy - reduction in the red reflex 2) slit-lamp examination 3) lenticular opacities may be observed with 1 & 2 Complications: - older drivers with cataracts were 2.5 times more likely to have a history of at fault motor vehicle accidents - angle closure glaucoma - cataracts can displace the iris forward, narrowing the angle [14] - glaucoma, cataracts, & age-related macular degeneration may increase risk of falls in the elderly [17] Management: 1) surgery a) indications: 1] diabetic retinopathy: monitoring requires a clear lens 2] vision worse than 20/40 3] visual function interferes with life function b) procedures: 1] lens implantation 2] extracapsular approach a] leaves posterior capsule of lens in place b] permits posterior chamber lens implants c] reduces incidence of post-operative complications 3] phacoemulsification a] ultrasonic vibrations to remove lens b] requires smaller incision c] shorter period of post-operative visual rehabilitation c) YAG laser capsulotomy for post-operative opacification d) routine perioperative evaluation unnecessary [3] 2) tight control of diabetes 3) vitamin/mineral supplementation (antioxidants?) may provide some protective benefit [4,5] a) vitamin A & beta-carotene, vitamin C, zinc b) Ocuvite Preservision c) vit E, riboflavin & thiamine supplements may reduce progression of age-related lens opacification [6] 4) use of statins may be associated with reduced risk [7] 5) UV light filters (sunglasses) Comparative biology: - lanosterol reverses protein aggregation in cataracts (in vitro, rabbits, dogs) [12] - molecules that bind to alpha-crysallin & prevent their misfolding & aggregation may improve crystalline lens transparency [12]

Related

cataract surgery

Specific

anterior cortical cataract (ACC) congenital cataracts cortical cataract familial cataracts glaucomatous flecks; glaukomflecken nuclear sclerosis nuclear sclerotic cataracts (NSC) posterior subcapsular cataract (PSC)

General

ocular lens disorder sign/symptom

References

  1. Harrison's Principles of Internal Medicine, 13th ed. Companion Handbook, Isselbacher et al (eds), McGraw-Hill Inc. NY, 1995, pg 829-39.
  2. DeGowin & DeGowin's Diagnostic Examination, 6th edition, RL DeGowin (ed), McGraw Hill, NY 1994, pg 872
  3. Medical Knowledge Self Assessment Program (MKSAP) 11, 15, American College of Physicians, Philadelphia 1998, 2009
  4. Journal Watch 21(1):3, 2001 Mares-Perlman et al Arch Ophthalmol 118:1556, 2000
  5. Mangione C. In: Intensive Course in Geriatric Medicine & Board Review, Marina Del Ray, CA, Sept 12-15, 2001
  6. Jacques PF, Taylor A, Moeller S Long-term nutrient intake and 5-year change in nuclear lens opacification, Archives of Ophthalmology 123:517, 2005
  7. Klein BEK et al, Statin use and incident nuclear cataract. JAMA 2006; 295:2752 PMID: 16788130
  8. Geriatric Review Syllabus, 7th edition Parada JT et al (eds) American Geriatrics Society, 2010
  9. Asbell PA, Dualan I, Mindel J, Brocks D, Ahmad M, Epstein S. Age-related cataract. Lancet. 2005 Feb 12-18;365(9459):599-609. PMID: 15708105
  10. Bienfang DC, Kelly LD, Nicholson DH, Nussenblatt RB Ophthalmology. N Engl J Med. 1990 Oct 4;323(14):956-67. PMID: 2205800
  11. Delcourt C et al. Risk factors for cortical, nuclear, and posterior subcapsular cataracts: the POLA study. Am J Epidemiol 2000 Mar 9; 151:497-504 PMID: 11004323
  12. Zhao L et al. Lanosterol reverses protein aggregation in cataracts. Nature 2015 Jul 30; 523:607. PMID: 26200341 - Makley LN et al. Pharmacological chaperone for alpha-crystallin partially restores transparency in cataract models. Science 2015 Nov 6; 350:674. PMID: 26542570 - Quinlan RA. A new dawn for cataracts: Sterols reverse protein aggregation in an eye lens paradigm. Science 2015 Nov 6; 350:636. PMID: 26542559
  13. Lamoureux EL, Fenwick E, Pesudovs K, Tan D. The impact of cataract surgery on quality of life. Curr Opin Ophthalmol. 2011 Jan;22(1):19-27. Review. PMID: 21088580
  14. Hobbs BN Seeing Red: Five Eye Diagnoses Not to Miss Medscape - Apr 23, 2018. https://www.medscape.com/viewarticle/895295
  15. Iroku-Malize T, Kirsch S. Eye Conditions in Older Adults: Cataracts. FP Essent. 2016 Jun;445:17-23. PMID: 27348528 Review.
  16. Pelletier AL, Rojas-Roldan L, Coffin J. Vision Loss in Older Adults. Am Fam Physician. 2016 Aug 1;94(3):219-26. PMID: 27479624 Free article. Review.
  17. Tsang JY et al. Risk of falls and fractures in individuals with cataract, age-related macular degeneration, or glaucoma. JAMA Ophthalmol 2023 Dec 28; [e-pub]. PMID: 38153708 https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2813168