> Table of Contents > Cataract
Cataract
Yasir Ahmed, MD
Ingrid U. Scott, MD, MPH
image BASICS
DESCRIPTION
  • A cataract is any opacity or discoloration of the lens, localized or generalized; the term is usually reserved for changes that affect visual acuity (1,2).
  • Etymology: from Latin catarractes, for “waterfall”; named after foamy appearance of opacity
  • Leading cause of blindness worldwide, estimated 20 million people (1,2)
  • Types include the following:
    • Age related: 90% of total
    • Metabolic (diabetes via accelerated sorbitol pathway, hypocalcemia, Wilson disease)
    • Congenital (1/250 newborns; 10-38% of childhood blindness)
    • Systemic disease associated (myotonic dystrophy, atopic dermatitis)
    • Secondary to associated eye disease, so-called complicated (e.g., uveitis associated with juvenile rheumatoid arthritis or sarcoid, tumor such as melanoma or retinoblastoma)
    • Traumatic (e.g., heat, electric shock, radiation, concussion, perforating eye injuries, intraocular foreign body)
    • Toxic/nutritional (e.g., corticosteroids)
  • Morphologic classification:
    • Nuclear: exaggeration of normal aging changes of central lens nucleus, often associated with myopia due to increased refractive index of lens (some elderly patients consequently may be able to read again without spectacles, so-called second sight of the aged)
    • Cortical: outer portion of lens; may involve anterior, posterior, or equatorial cortex; radial, spoke-like opacities
    • Subcapsular: Posterior subcapsular cataract has more profound effect on vision than nuclear or cortical cataract; patients particularly troubled under conditions of miosis; near vision frequently impaired more than distance vision.
  • System(s) affected: nervous
Geriatric Considerations
Some degree of cataract formation is expected in all people >70 years of age.
Pediatric Considerations
See “Congenital Cataract”; may present as leukocoria.
Pregnancy Considerations
See “Congenital Cataract” (i.e., medications, metabolic dysfunction, intrauterine infection, and malnutrition).
EPIDEMIOLOGY
Incidence
  • ˜48% of the 37 million cases of blindness worldwide result from cataracts (1,2).
  • Leading cause of treatable blindness and vision loss in developing countries (1,2)
  • Predominant age: depends on type of cataract
  • Predominant sex: male > female
Prevalence
  • Cataract type and prevalence are highly variable based on population demographic.
  • An estimated 50% of people 65 to 74 years of age and 70% of people >75 years of age have age-related cataract.
ETIOLOGY AND PATHOPHYSIOLOGY
  • Age-related cataract:
    • Continual addition of layers of lens fibers throughout life creates hard, dehydrated lens nucleus that impairs vision (nuclear cataract).
    • Aging alters biochemical and osmotic balance required for lens clarity; outer lens layers hydrate and become opaque, adversely affecting vision.
  • Congenital:
    • Usually unknown etiology
    • Drugs (corticosteroids in 1st trimester, sulfonamides)
    • Metabolic (diabetes in mother, galactosemia in fetus)
    • Intrauterine infection during 1st trimester (e.g., rubella, herpes, mumps)
    • Maternal malnutrition
  • Other cataract types:
    • Common feature is a biochemical/osmotic imbalance that disrupts lens clarity.
    • Local changes in lens protein distribution lead to light scattering (lens opacity).
Genetics
  • Congenital (e.g., chromosomal disorders [Down syndrome])
  • Genetics of age-related cataract are not yet established but likely multifactorial contribution.
RISK FACTORS
  • Aging
  • Cigarette smoking
  • Ultraviolet (UV) sunlight exposure
  • Diabetes
  • Prolonged high-dose steroids
  • Positive family history
  • Alcohol
GENERAL PREVENTION
  • Use of UV protective glasses
  • Avoidance of tobacco products
  • Effective control of diabetes
  • Care with high-dose, long-term steroid use (systemic therapy > inhaled treatment)
  • Protective methods using pharmaceutical intervention (e.g., antioxidants, acetylsalicylic acid [ASA], hormone replacement therapy [HRT]) show no proven benefit to date.
COMMONLY ASSOCIATED CONDITIONS
  • Diabetes (especially with poor glucose control)
  • Myotonic dystrophy (90% of patients develop visually innocuous change in 3rd decade; becomes disabling in 5th decade)
  • Atopic dermatitis (AD) (10% of patients with severe AD develop cataracts in 2nd to 4th decades, often bilateral)
  • Neurofibromatosis type 2
  • Associated ocular disease or “secondary cataract” (e.g., chronic anterior uveitis, acute [or repetitive] angle-closure glaucoma or high myopia)
  • Drug induced (e.g., steroids, chlorpromazine)
  • Trauma
image DIAGNOSIS
PHYSICAL EXAM
  • Visual acuity assessment for all cataracts
  • Age-related cataract: lens opacity on eye examination
  • Congenital:
    • Lens opacity present at birth or within 3 months of birth
    • Leukocoria (white pupil), strabismus, nystagmus, signs of associated syndrome (as with Down or rubella syndrome)
    • Note: must always rule out ocular tumor; early diagnosis and treatment of retinoblastoma may be lifesaving
  • Other types of cataract: may present with decreased visual acuity associated with characteristic physical findings (e.g., metabolic, trauma)
DIFFERENTIAL DIAGNOSIS
  • An opaque-appearing eye may be due to opacities of the cornea (e.g., scarring, edema, calcification), lens opacities, tumor, or retinal detachment. Biomicroscopic examination (slit lamp) or careful ophthalmoscopic exam should provide diagnosis.
  • In the elderly, visual impairment is often due to multiple factors such as cataract and macular degeneration, both contributing to visual loss.
  • Age-related cataract is significant if symptoms and ophthalmic exam support cataract as a major cause of vision impairment.
  • Congenital lens opacity in the absence of other ocular pathology may cause severe amblyopia.
  • Note: Cataract does not produce a relative afferent pupillary reaction defect. Abnormal pupillary reactions mandate further evaluation for other pathology.
DIAGNOSTIC TESTS & INTERPRETATION
  • Visual quality assessment: Glare testing, contrast sensitivity is sometimes indicated.
  • Retinal/macular function assessment: potential acuity meter testing
  • Workup of underlying process
P.167

Test Interpretation
Consistent with lens changes found in the type of cataract; however, diagnosis is made by clinical examination.
image TREATMENT
  • Outpatient (usually)
  • ˜1.64 million cataract extractions in the United States yearly (3,4)
GENERAL MEASURES
Eye protection from UV light
MEDICATION
There are currently no medications to prevent or slow the progression of cataracts.
ISSUES FOR REFERRAL
If patient has cataract and symptoms do not seem to support recommended surgery, a second opinion by another ophthalmologist may be indicated.
SURGERY/OTHER PROCEDURES
  • Age-related cataract:
    • Surgical removal is indicated if visual impairment-producing symptoms are distressing to the patient, interfering with lifestyle or occupation, or posing a risk for fall or injury (3,4)[A].
    • Because significant cataract may develop gradually, the patient may not be aware of how it has changed his or her lifestyle. Physician may note a significant cataract, and patient reports “no problems.” Thus, evaluation requires effective physician-patient exchange of information.
    • Surgical technique: Cataract extraction via small incisions, followed by implantation of a prosthetic intraocular lens; lenses have power calculated based on size of the eye and curvature of cornea usually to correct for distance vision; surgery performed on one (worse) eye, with contralateral surgery only after recovery and if deemed necessary; generally takes <1 hour depending on surgical technique
    • Anesthesia: usually regional injection or topical with sedation and monitoring of vital signs
    • Preoperative evaluation: by the primary care physician:
      • Patients on anticoagulants may need to be temporarily discontinued 1 to 2 weeks before surgery if possible (but not always necessary; thus, need to discuss with ophthalmologist).
      • Patients who have ever taken an α-blocker such as tamsulosin (Flomax) should alert their ophthalmologist (increased risk of intraoperative floppy iris syndrome [IFIS] even in patients who no longer use these drugs).
    • Postoperative care: usually protective eye shield as directed, topical antibiotic, NSAIDs, and steroid ophthalmic medications; avoid lifting or bending over for a few weeks.
  • Congenital cataract:
    • Treatment is surgical removal of cataract. Newborns may require surgery within days to reduce risk of severe amblyopia. Use of lens implants is controversial because the eyes are growing.
    • Postoperative care: long-term patching program for good eye to combat amblyopia; refractive correction of operative eye, with multiple repeat examinations; challenging for physician and parents
image ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
Patient Monitoring
  • As cataract progresses, an ophthalmologist may change spectacle correction to maintain vision. When this is no longer successful and interferes with patient's activities of daily living, surgery is indicated.
  • Following surgery, spectacle correction may be required to maximize near and/or far visual acuity. Refraction is usually prescribed several weeks after surgery.
PATIENT EDUCATION
Medline Plus on cataracts at: https://www.nlm.nih.gov/medlineplus/cataract.html
PROGNOSIS
  • Ocular prognosis is good after cataract removal if no prior or coexisting ocular disease: 94.3% of otherwise healthy eyes achieve best corrected visual acuity of 20/40 or better. Success rates are lower with comorbidities such as diabetes and glaucoma (5).
  • In congenital cataracts, prognosis often is poorer because of the high risk of amblyopia.
REFERENCES
1. Asbell PA, Dualan I, Mindel J, et al. Age-related cataract. Lancet. 2005;365(9459):599-609.
2. Abraham AG, Condon NG, West Gower E. The new epidemiology of cataract. Ophthalmol Clin North Am. 2006;19(4):415-425.
3. Riaz Y, Mehta JS, Wormald R, et al. Surgical interventions for age-related cataract. Cochrane Database Syst Rev. 2006;(4):CD001323.
4. Fedorowicz Z, Lawrence D, Gutierrez P. Day care versus in-patient surgery for age-related cataract. Cochrane Database Syst Rev. 2005;(1):CD004242.
5. Biber JM, Sandoval HP, Trivedi RH, et al. Comparison of the incidence and visual significance of posterior capsule opacification between multifocal spherical, monofocal spherical, and monofocal aspheric intraocular lenses. J Cataract Refract Surg. 2009;35(7):1234-1238.
6. Findl O, Buehl W, Bauer P, et al. Interventions for preventing posterior capsule opacification. Cochrane Database Syst Rev. 2010;(2):CD003738.
7. Lundström M, Barry P, Henry Y, et al. Visual outcome of cataract surgery; study from the European Registry of Quality Outcomes for Cataract and Refractive Surgery. J Cataract Refract Surg. 2013;39(5):673-679.
8. Lundström M, Goh PP, Henry Y, et al. The changing pattern of cataract surgery indications: a 5-year study of 2 cataract surgery databases. Ophthalmology. 2015;122(1):31-38.
See Also
  • Algorithm: Cataracts
  • Floppy Iris Syndrome
Codes
ICD10
  • H26.9 Unspecified cataract
  • H25.9 Unspecified age-related cataract
  • Q12.0 Congenital cataract
Clinical Pearls
  • Cataracts are the leading cause of blindness worldwide; 90% are age-related.
  • Primary indication for cataract surgery is visual impairment leading to significant lifestyle changes for the patient.
  • For congenital cataracts, must always rule out ocular tumor because early diagnosis and treatment of retinoblastoma may be lifesaving.
  • Before prescribing an α-blocker for an older adult with hypertension or a prostate or urinary retention problem, consider whether the patient has cataracts (due to increased risk of IFIS).