Mild pain, soreness or grittiness usually affecting both eyes is seen in blepharitis, with poor tear film (dry eye), and in contact lens over-wear.
More specific discomfort giving a sensation of something in the eye, usually unilaterally, is seen with eyelash disorder (trichiasis), and in-turn of the eyelid (entropion)
Severe deep pain, often sufficient to impair sleep, suggests scleritis. Additional impairment of vision, nausea and vomiting may indicate acute glaucoma.
