What is a characteristic sign of blepharitis?

Blepharitis is an inflammation of the eyelid margins, and a characteristic sign of this condition is indeed itchy, scaly eyelid margins. The inflammation can lead to the crusting of the eyelids, redness, and irritation. This symptom is due to the accumulation of debris, oil, and bacteria along the eyelid margins, which causes discomfort and itchiness, making the eyelids feel irritated and sensitive.

In contrast, increased tear production typically indicates conditions like dry eye syndrome rather than blepharitis. Clear vision is not directly associated with blepharitis as the inflammation can lead to discomfort that may temporarily affect visual clarity, although it does not inherently cause vision problems. Night blindness is unrelated to blepharitis and usually pertains to issues with the retina or a deficiency in vitamin A. Therefore, the itching and scaly appearance of the eyelid margins are the definitive signs that highlight blepharitis.