Which of the following is NOT a known side effect of Isotretinoin (accutane)?

Isotretinoin, commonly known as Accutane, is primarily used for the treatment of severe acne and is known for its range of side effects due to its potent effects on the body.

Cystoid macular edema is not commonly recognized as a direct side effect of isotretinoin. While isotretinoin can lead to various ocular side effects, including dry eye, night blindness (nyctalopia), and even increased intracranial pressure which could lead to papilledema, cystoid macular edema is not a well-documented complication associated with isotretinoin use.

In contrast, dry eye is a common side effect because isotretinoin reduces the production of sebum and can affect the quality and quantity of tears. Night blindness and papilledema can also occur due to the effects isotretinoin has on the retina and intracranial pressure, respectively. Thus, the lack of a direct correlation between isotretinoin and cystoid macular edema supports the choice of that answer as the correct response for the question, as it is the least likely side effect in the context of isotretinoin treatment.