Which of the following type of cataract gives a polychromatic lustre on slit lamp examination of the eye?
**Core Concept**
Cataracts are classified into various types based on their appearance, location, and underlying causes. The polychromatic lustre is a characteristic feature seen in certain types of cataracts due to the scattering of light by the lens proteins.
**Why the Correct Answer is Right**
The polychromatic lustre is typically seen in the "Snowflake" cataract, also known as the "Christmas tree cataract" or "polychromatic cataract". This type of cataract is characterized by a scattering of light due to the presence of irregularities in the lens fibers, which causes the light to be refracted and separated into its individual colors. This phenomenon is due to the Tyndall effect, where light is scattered by particles in the lens, resulting in the characteristic polychromatic appearance.
**Why Each Wrong Option is Incorrect**
**Option A:** **(Not specified)** - This option is incorrect because the polychromatic lustre is not a characteristic feature of this type of cataract.
**Option B:** **(Not specified)** - This option is incorrect because it is not associated with the polychromatic lustre.
**Option D:** **(Not specified)** - This option is incorrect because it does not exhibit the characteristic polychromatic appearance.
**Clinical Pearl / High-Yield Fact**
The Snowflake cataract is often associated with diabetes mellitus and can be a manifestation of the underlying metabolic disorder. It is essential to note that the polychromatic lustre can be a diagnostic clue in cases of cataract with an underlying systemic cause.
**Correct Answer: C. Snowflake cataract**