Tearing up when the eyes see sunlight indicates an ocular surface disease causing corneal irritation, photophobia, pain, and tearing, which may be associated with various factors, such as inflammation, foreign bodies, trauma, physical or chemical irritation, resulting in conjunctival congestion and corneal epithelial detachment in the eye. The more common ones in clinical practice are conjunctivitis, keratitis, conjunctival sac foreign body, corneal foreign body, eyelid conjunctival stones, and inverted eyelashes. If the pupil is dilated for various reasons, discomfort and even tearing may also occur when encountering sunlight stimulation. If you stay up late and work late and lack sleep frequently, it may lead to visual fatigue or dry eye, and similar symptoms may occur. In the case of iridocyclitis, painful ciliary nerves are formed, and there will also be obvious symptoms of photophobia and tear irritation.