SENILE CATARACT- Pathophysiology, Symptoms, Complications

Peripheral cortical cataract causes Nyctalopia. Central vitreous opacity, Congenital deficiency of cones and Central nuclear or polar cataracts can cause Hamarlopia (Day blindness).

• Intumescent cataract is a form of cortical cataract where the nucleus is white and the capsular bag is swollen because of fluid absorption. 
• Morgagnian cataract is a hypermature cataract in which entire lens capsule is wrinkled and total liquefaction of the cortex allows the nucleus to move freely in the bag and sink inferiorly due to effects of gravity.

A i.e. Posterior subcapsular cataract 

Steroid induced lens opacities are posterior subcapsularQ. Whereas anterior polar cataract is caused by perforating cornea/ injuriesQ.

Nuclear Cataract:

• Hemeralopia: Day blindness due to pupil constriction.
• Decreased distant vision: Due to index myopia ; (Distant vision > Near vision)
• Second sight phenomenon 

A i.e. Posterior cortical cataract

Ans. Cortical cataract

Ans. Posterior subcapsular cataract

Ans: C i.e. Posterior subcapsular cataract

Cataracts & their effects

• Nuclear cataract manifest as colour shift (more obvious after surgery), second sight/ myopic shift, frequent change of glasses etc.
• Loss of ability to see objects in bright sunlight, blinding by the light of oncoming headlamps when driving at night or glare may be the symptom of posterior subcapsular cataract
• A cortical cataract may manifest as frequent change of glasses, monocular diplopia/ polyopia, glare or coloured halos around light

Ans. A i.e. Nuclear cataract

Symptoms of nuclear cataract

Blurring of distance more than near vision typically, but others may notice worsening of reading more than the distance

Increasing myopia “Second-sight” phenomenon of improved uncorrected distance vision in hyperopes and improved uncorrected near vision in emmetropes

Poor vision in dark settings such as night driving

Decreased contrast and decreased ability to discern colors

Glare

Monocular diplopia

Ans. is ‘b’ i.e., Index myopia

• Nuclear changes of aging induce a modification of refractive index of lens and produce an index myopia.
• “Nuclear cataracts cause a general decrease in the transperancy of the lens nucleus.They are associated

withindexmyopia”                                                                                                  — Ophthalmic study guide

Causes of errors of refraction

• Possible causes of ametropia are : ‑

1) Axial

• It is the commonest form of ametropia (both myopia and hypermetropia). In hypermetropia, there is an axial shortening of eyeball. So, image is formed behind the retina. In myopia, there is an axial lengthening of eyeball. So, image is formed in front of the retina. 1 mm change in axial length leads to ametropia of 3D. For example 1 mm shortening in axial length causes hypermetropia of 3D.

2) Curvature

• Change in the curvature of cornea or lens will cause ametropia. In hypermetropia, the curvature of cornea or lens is lesser than normal. In myopia, there is increase in curvature of cornea or lens./ mm change in corneal curvature leads to 6-7 D ametropia.

3) Index

• If refractive index of optical system is low, it will result in hypermetropia and high refractive index will result in myopia.

4) Positional (Due to relative position of the lens),

• A forward shift of lens causes myopia, backward shift result in hypermetropia. Absence of lens (aphakia) causes hypermetropia.

5) Excessive accommodation

• Excessive accommodation due to spasm of accommodation causes myopia.