- Clinical science
Cataract is a condition characterized by clouding of the lens of the eye. This condition most frequently occurs due to age-related degenerative processes in the lens, but can also be associated with ocular trauma, metabolic disorders, side-effects of drugs, or congenital infections. The clouding causes distortion of light, as it passes through the lens, resulting in visual impairment and glare. Initially, a cataract presents discretely and may even go unnoticed, but the visual impairment worsens as the cataract grows larger. Diagnosis is typically established on the basis of a thorough history and direct visualization of the cataract (by means of slit-lamp microscopy). Surgery is indicated with significant visual impairment and involves lens extraction and implantation of an artificial lens. Untreated cataracts eventually lead to complete blindness.
- Leading cause of visual impairment and blindness in the world
Prevalence of acquired cataracts
Increases with age
- 40–80 years: ∼ 17.5 %
- > 80 years: ∼70 %
- Sex: ♀ > ♂
- Increases with age
Epidemiological data refers to the US, unless otherwise specified.
Clouding of the lens may be congenital or acquired.
- Congenital cataracts (< 1%)
Acquired cataracts (> 99%)
- Age-related (> 90%)
- Associated with comorbidities/syndromes
- Diabetes mellitus
- Renal insufficiency (dialysis)
- Tetany (hypocalcemia)
- Myotonic dystrophy
- Wilson's disease
- Skin diseases
- Trisomy 21 (in early childhood)
- Alport syndrome
- Neurofibromatosis type 2
- Galactokinase deficiency
- As a result of ocular diseases (complicated cataract)
- After intraocular surgeries
- Traumatic (traumatic cataract)
- Bruise injuries
- Perforation injuries
- Physically related conditions
- Radiation (X-ray, radioactive radiation)
- Excessive sunlight or UVB exposure
- High-voltage current, lightning
- Infrared radiation (glassblower's and glass worker's cataract)
- Posterior capsule opacification (PCO; or secondary cataract)
In industrialized countries, cataract is typically age-related! Other causes are rare!
- Cataracts may be classified according to etiology (as above) or morphology
Morphological classification .
- Anterior/posterior cortical cataract (approx. 50%) :
- Nuclear cataract (approx. 30%) :
- Anterior/posterior subcapsular cataract (approx. 20%)
- Mature senile cataract
- Hypermature cataract
General clinical features
Clinical features usually develop gradually and depend on the localization and cause(s) of corneal clouding.
- Reduced visual acuity: blurred, clouded, or dim vision
- The impairment of vision is usually painless and often bilateral.
- Glare: in daylight, in low sunlight, and from car headlights; associated with halos around lights .
- Second sight
- Opacities within the red reflex, darkening of the red reflex, or obscuration of ocular fundus detail during opthalmoscopy
- Grey, white, yellow, or brownish clouding of the lens
- Monocular diplopia
- Hyperopia (in cortical cataract)
- Change in color perception
- Special features in traumatic cataract
Special features in congenital cataract
Congenital cataracts usually present with different symptoms than acquired cataracts.
- Delay in motor skill development
There are different stages of senile cataract:
- Incipient cataract
- Intumescent cataract
- Immature cataract
- Mature/hypermature cataract
- Special type: Morganian cataract
- Primarily a clinical diagnosis
- Ocular imaging studies: ultrasonography, computed tomography (CT) scanning, or MRI
- In most cases conservative treatment and drug therapy for cataract does not exist
Indications for surgical treatment
- To improve vision in cases with significant cataract-related visual disturbances (by far the most frequent indication)
- Medical indication (e.g., imminent phacolytic glaucoma, or in ocular fundus diseases in order to gain clear insight of the ocular fundus)
Extracapsular cataract extraction (ECCE)
- Method of choice globally
- Removal of the lens nucleus by anterior capsulotomy (a surgical opening in the anterior capsule) with retention of posterior capsular integrity, and placement of the intra-ocular lens (IOL) in the posterior chamber.
- Removal of the lens nucleus in ECCE can be performed manually in standard surgical ECCE or by phacoemulsification:
Intracapsular cataract extraction (ICCE, former method of choice):
- Involves removal of the entire lens, including the posterior capsule. The IOL is implanted in the anterior chamber, sutured to the iris, or surgically fixated in the posterior chamber.
- More invasive procedure (requires a larger incision) associated with high rate of complications like delayed wound healing, corneal edema, iris incarceration, etc.
- Can be performed in cases with subluxated or luxated lenses (posttraumatic and hypermature cataracts) or if advanced surgical equipment is unavailable.
- Extracapsular cataract extraction (ECCE)
Cataract surgery does not require any anticoagulative measures!
- Phacolytic glaucoma
- in congenital cataract
- Complications after cataract surgery are rare
We list the most important complications. The selection is not exhaustive.