If ‘new-onset’, consider the possibility of corneal disease or anterior uveitis. Conduct slit-lamp evaluation and tonometry to rule it out.
Usually reported to be longstanding. Often reported by patients with emotion-based problems. My own experience of patients with this symptom is of female teenagers with difficult family/home conditions. It may also be reported by patients with personality disorders.
Rule out ocular diseases.
Try and provide reassurance.
Recommend UV absorbing coated eyewear.
Recommend effective, dark tint, UV absorbing coated sunglasses.