Question

Which morphological type of cataract is most visually handicapping?

• A. Cortical
• B. Nuclear
• C. Posterior subcapsular
• D. Zonular

Hint:

A small opacity right on the visual axis, where light rays converge, causes bigger visual trouble than a similar sized opacity elsewhere in the lens.

Answer 1

The Correct Option is C

Step 1: Recall where light converges in the eye.
Light rays entering the eye pass through the lens and converge toward a point near the back of the lens, close to the visual axis, before reaching the retina. Any opacity sitting right in this converging pathway blocks a disproportionately large share of the light.

Step 2: Locate the posterior subcapsular cataract.
A posterior subcapsular cataract sits just in front of the posterior capsule, directly in the path where light rays are bunching together on their way to the retina and right on the visual axis. Even a small opacity here blocks a large amount of light and scatters it badly, especially under bright light or when the pupil constricts, such as in daylight or while reading.

Step 3: Compare with cortical cataract.
Cortical cataracts start as wedge or spoke shaped opacities in the peripheral lens cortex. Early on, the visual axis is spared, so vision is often preserved until the wedges extend further inward, making this type slower to disturb central vision.

Step 4: Compare with nuclear cataract.
Nuclear cataracts affect the central lens nucleus and progress slowly over years, gradually yellowing or browning. Visual loss develops gradually and mainly affects distance vision, taking a long time to become handicapping, and it can even temporarily improve near vision by increasing lens power.

Step 5: Compare with zonular cataract.
Zonular, or lamellar, cataract is a specific layer of opacity, often congenital or metabolic in origin, and does not typically produce the severe, rapid visual disability seen with posterior subcapsular opacities.

Step 6: Final answer.
Because it sits exactly at the point where light rays converge on the visual axis, even a small posterior subcapsular cataract causes marked glare and loss of near vision out of proportion to its size.
\[ \boxed{\text{Posterior subcapsular cataract}} \]