B1 Cataract Flashcards
define cataract
it is the loss of transparency of the crystalline lens
state aetiologies (manner of causation) of cataract
congenital (physiological or mafan syndrome)
acquired: ageing / senile, primary ocular disease (ie. chronic uveitis), systemic disease (ie. diabetes mellitus), drugs (ie. corticosteroids), trauma (blunt), UV exposure, high myopia
general SSX of cataract
sign: loss of transparency of lens
symptoms: refractive (myopic/hyperopic) shift, reduced (distance/near) vision, glare, desaturation of colours
state risk factors of congenital cataract
hereditary
maternal infections
metabolic changes
chromosomal defects
birth trauma
briefly describe congenital cataract
3 in 10000 births
2/3 bilateral
non progressive
explain management for congenital cataract
treatment: usually detected when very young, early surgery (early 6 weeks old) to prevent deprivation stimulation amblyopia & nystagmus
management: accurate refraction correction pre-post surgery
patient assurance: little impact on vision, usually not progressive or severely dense
patient education: monitor opacity & visual function, regular eye check up
state risk factors for acquired cataract
ageing / senile
primary ocular disease (can cause earlier onset ie. chronic uveitis, retinitis pigmentosa, retinal detachment, high pathological cataract)
systemic disease ie. DM
congenital anomalies ie. marfan syndrome
drug ie. corticosteroids, miotics
trauma (blunt)
others ie. high myopia, UV exposure
name the senile cataracts
nucleus sclerosis
cortical
posterior subcapsular
explain nucleus sclerosis (causation, SSX)
photo-oxidation of the lens protein
signs: yellowing of lens or “lemon drop” appearance, myopic shift (centre part of lens thickens, causing RI to increase, converges light more)
symptoms: reduced distance vision, glare during bright light (constricted pupil affected, nucleus cataract blocks light), desaturation of colours
explain cortical cataract (causation, SSX)
imbalance of electrolytes causing over hydration of cortex
signs: water vacuoles, clefts, spokes & wedges appearance in lens cortex, hyperopic shift (lens thickens in peripheral/sides, light converges less)
symptoms: reduced near vision, glare during night time (dilated pupil affected), affects central vision in the later stage
explain posterior subcapsular (causation, SSX)
migration of epithelial cells toward the posterior pole to replace lens fibre nuclei loss
signs: granular opacity just in front of posterior lens capsule, no refractive change BUT visual acuity drastically affected (visual axis is blocked)
symptoms: severely impaired central vision, Especially in bright light
explain brunescent cataract
advanced type of nucleus cataract that has become brown and opaque
state causative diseases for complicated cataract
chronic anterior uveitis
high myopia (pathological)
retinal detachment
retinitis pigmentosa
explain factors that can lead to secondary cataract
systemic disease (diabetes mellitus): high glucose in AQH, sorbitol build up, osmotic pressure changes cause over hydration of lens, onsets in teens, predispose to senile cataract earlier (PSCC or snowflake -> just behind anterior pole or in front posterior pole)
congenital anomalies (marfan syndrome)
drug-related cataract (corticosteroids, anticholinesterases/mitotics): due to long term systemic or topical use, used in glaucoma treatment respectively (usually PSCC bilateral)
blunt trauma: traumatic cataract/rosette cataract
explain cataract in irradiation exposure
(1) true exfoliation: caused by long term heat exposure ie. glassblower/welder, separation and curling up of anterior lamellae of the capsule
(2) pseudoexfoliation: senile lenticular abnormality, (ocular inflammation) white granular material on anterior pole / ac angle / pupil border / iris / ciliary body / lens, risk of glaucoma
