Acquired Cataract Topic 36
= degeneration of the already formed normal fibres ;the exact reasons and mechanism is unclear but any factor physical ,chemical or biological disturbing the intra and extracellular equilibrium of water and electrolytes or deranging the colloid system within the lens fibres
1) Senile cataract
- -age-related cataract , bi lateral but one is affected earlier than the other
- Commonest type of acquired cataract (over 70=90%)
- Two types : soft (cortical) or hard (nuclear) or both
- Cause : heredity (determines onset &development ),UV, dietary deficiency (vit E&c) Dehydration crisis ,smoking ,{ DM myotonic dystrophy &atopic dermatitis in <50 years}
- Mechanism : Cortical→ decreased proteins, AA &K+ thus denaturation of lens protein
- Nuclear→ nuclear sclerosis thus hard cataract
- Types are according to different MATURITY LEVELs for each cortical &nuclear
- Stages of cortical type of senile
- a) Lamellar separation : reversible demarcation of cortical fibres with fluid separating them
- b) immature :detectable opacities with clear areas between them cupuliform (saucer pan opacity below the capsule ), Cuneiform→ strikes radiating radially around circumference
- c) Mature : opacification complete not only strikes involving entire cortex → pearly white
- d) Hyper mature : Morgagnian cataract → liquefying of cataract thus lens = milky fluid bag
Stages of nuclear senile cataract
Sclerotic process → lens inelastic &hard ; nucleus may become diffusely cloudy (greyish) or tinted (yellow /black) due to deposition of pigment; in practice amber, brown, black seen
Symptoms & signs of cataract
Symptoms : maybe no harm but common Glare (intolerance of bright light) , polyopia (irregular refraction ) Coloured halos (as fluid in cataract breaks down white light ) , Black spots (stationary) , Image blur In senile→ painless and gradually progressive but cupuliform (central) earlier loss of vision & better in dim light as pupil dilate, In peripheral (cuneifo.) better vision , nuclear sclerosis → index myopia (bad distant)
Signs : visual acuity decrease, Oblique illumination (colour of cataract ), Test of iris shadow (present), distant direct ophthalmoscopy ( red/yellow fundal normally; abnormal= red /black or just black shadow) Slit lamp most important → reveals full morphology (site, size, shape, colour &hardness)
Complications : hypermature cataract leakage as protein enter anterior chamber ; inducing antigen-antibody reaction leading to uveitis, Induced glaucoma → swelling of lens/ leakage blocking filtration , Subluxation
Other types of acquire cataracts :
- 1) Metabolic : due to endocrine disorder & biochemical abnormalities