28 terms

Lens 2: Presenile Cataract

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Diabetes Mellitus
Systemic Disease Related

Hyperglycemia causes high levels of glucose in the aqueous humour
-diffuses into the lens, metabolized into sorbitol & accumulates
-alters the refractive index of the lens
a. ref error changes (myope), cataracts, amplitude of accommodation changes

Classic diabetic cataract (rare)
-snowflake cortical opacities in young diabetics
-may resolve spontaneously or resolve in a few days

Age related cataract
-occur earlier, progress more rapidly
-nuclear opacities are common
Myotonic Dystrophy
Systemic Disease Related

90% develop fine cortical opacities (3rd decade)
-may resemble xmas tree cataract initially

Evolve into cortical and subcapsular opacities by 5th decade
-may have stellate (star like) appearance
(Severe) Atoptic Dermatitis
Systemic Disease Related

-10% develop cataract in 2nd to 4th decade
-Shield like, dense anterior subcapsular plaque --> wrinkles anterior capsular surface, mature quickly
Neurofibromatosis Type 2
Systemic Disease Related

-60% develop cataract before age 30
-posterior subcapsular or capsular, cortical or mixed
Traumatic Cataract
Most common cause of unilateral cataract in young people.
Degree and location depends upon cause.

Penetrating trauma causes major damage.

Blunt trauma
a. Classic rosette (flower shape) opacity; usually subcapsular
b. May see a Vossius ring; pigment ring on lens from pupil margin
c. Look for other signs of traumatic damage

Also caused by:
1. Electric shock/ lightning (rare)
-diffuse milky white opacification and multiple snowflake opacities
2. Ionizing radiation to ocular tumours
-posterior sub-capsular cataracts (months to years later)
3. Infrared radiation (glassblowers cataract)
-true exfoliation or delamination of the anterior capsule
Drug Induced Cataract: Steroids
Both systemic and topical.

Initial opacities are posterior subcapsular.
-anterior subcapsular affected later.

May be genetic susceptibility
-may not be related to dosage
-dosage may need to be reduced if cataract forms
Drug Induced Cataract: Chlorpromazine
May cause deposits of fine granules on anterior lens capsule.
-also deposits on posterior cornea

Dose related and irreversible.
Drug Induced Cataract: Amiodarone
Used to treat cardiac arrhythmia.

50% show anterior subcapsular deposits
-vision not affected
-also look for corneal deposits
Drug Induced Cataract: Allopurinol
Treats gout
-increase risk of cataract in elderly patient.
Secondary to Ocular Disease: Chronic Anterior Uveitis
Most common cause of secondary cataract
-incidence related to duration & activity of inflammation

S: Initial: Polychromatic lustre at posterior pole of lens
- progresses to posterior and anterior opacities if untreated
-progression is more rapid with posterior synechiae
Secondary to Ocular Disease: Acute Angle Closure Glaucoma
May cause small anterior subcapsular or capsular opacities within the pupillary area
-"glaucomflecken"
-grey white focal infarcts of lens epithelium

Pathognomonic of past acute angle closure.
Secondary to Ocular Disease: Pathological Myopia
S: posterior sub-capsular opacities and early onset nuclear sclerosis
-nuclear sclerosis may increase myopia

Not associated with simple myopia.
Secondary to Ocular Disease: Hereditary Fundus Dystrophies
Hereditary fundus dystrophies may be associated with posterior subcapsular cataract.
-Retinitis pigmentosa
-Leber congenital amaurosis
-Gyrate atrophy
-Stickler syndrome

Cataract surgery may improve VA with severe retinal disease.
Congenital Cataract
E: 3/ 10, 000 births
-2/3 of cases are bilateral

Most common cause is genetic mutation (AD)
-chromosomal abnormalities (eg. Down syndrome)
-metabolic disorders (eg. galactosemia)
-intrauterine infections (eg. rubella)

Morphology may be indicative of a etiology mode of inheritance and effect on vision

When severe, congenital cataracts appear as white reflex in pupil
-Leukocoria
-usually unilateral: must check red reflex of all neonates & children
Nuclear Congenital Cataract
-Opacities are confined to the nucleus
-Associated with microphthalmos
a. also rubella (in mother during pregnancy)
Lamellar Congenital Cataract
Opacities affecting a particular lamella of the lens
-anterior or posterior
-"riders" (radial extensions)

AD inheritance (isolation), metabolic disorders, intrauterine infection
-galactosemia, hypoglycaemia, hypocalcaemia
Anterior Polar Congenital Cataract
Flat or conical (pyramidal) opacities
-flat tend to be visually insignificant; conical can cause visual impairment

Associations: persistent pupillary membrane, aniridia, Peters anomaly, anterior lenticonus
Posterior Polar Congenital Cataract
Associations: posterior hyaloid remnants (Mittendorf dot), posterior lenticonus, persistent hyperplastic vitreous
Blue Dot Opacities: Congenital Cataract
Common and innocuous
-not sight threatening
-may coexist with other opacities
Sutural Congenital Cataract
Congenital and familial (X linked inheritance)
-cataract more prominent in males

S: opacities follow Y sutures
-vision is not usually affected (except in males with marked cataract)
Leukocoria
Common causes of Leukocoria
a. congenital cataract
b. retinoblastoma (retinal cell tumour): most common malignant tumour of eye in children
c. persistent hyperplasia of primary vitreous
d. retinal detachment; trauma, retinopathy of prematurity
e. toxocariasis (nematode infection)
f. posterior uveitis
Congenital Cataract Important Facts
33% Idiopathic- unilateral or bilateral
33% inherited- bilateral
33% % associated with systemic disease- usually bilateral
Other ocular anomalies present in 50% of cases
Causes of Cataracts in a Healthy Neonate
Hereditary
-usually AD

Idiopathic

Ocular Anomalies
-PHPV
-aniridia
-coloboma
-microphthalmos
-buphthalmos
Causes of Cataract in an Unhealthy Neonate
Intrauterine infections
a. Rubella
b. Toxoplasmosis
c. Cytomegalovirus
d. Varicella

Metabolic Disorders
a. Galactosaemia
b. Hypoglycaemia
c. Hypocalcaemia
d. Lowe Syndrome

Chromosomal Abnormalities
a. Down syndrome (trisomy 21)
b. Edwards syndrome (trisomy 18)
c. Cri du chat Syndrome (partial deletion of 5p)
Rubella
Results from transplacenta transmission of virus to the fetus from an infected mother
a. usually during 1st trimester
b. severe, chronic fetal infection and malformation

Systemic associations
a. spontaneous abortion
b. still birth
c. heart problems
d. deafness
e. neurological issues
f. mental handicap
g. liver, spleen, and lung issues

Ocular associations
a. cataract (15%)- unilateral or bilateral, pearly nuclear or diffuse (may be present at birth or develop several weeks or months later)
b. also: microphthalmos, glaucoma, anterior uveitis, iris atrophy, retinopathy, pendular nystagmus, strabismus, extreme refractive errors & poor vision
Metabolic Disorders: Galactosaemia
D: AR condition, inability to use galactose from milk
a. initially presents with failure to thrive lethargy, vomiting and diarrhoaea in infancy
b. if untreated: hepatosplenomegaly, renal disease, anaemia, deafness, mental handicap, early death

Ocular features
-central 'oil drop' opacity in the first few days or weeks of life
Metabolic Disorders: Lowe Syndrome
D: X- linked recessive condition causing an error in amino acid metabolism
-neuromuscular, renal and other manifestations

Cataract is universal
-also microphakia and glaucoma (50%)
Down syndrome
Trisomy Chromosome 21

Systemic associations:
-learning difficulties, characteristic facial features, thyroid dysfunction, cardiorespiratory disease, reduced life span

Ocular associations:
a. cataract (75%)- often symmetrical and develop in late childhood: varied morphology
b. chronic blepharitis, myopia, strabismus, keratoconus, anomalous optic disc vasculature, iris Brushfield spots