Photopsia is the subjective perception of light arising in the absence of light stimuli and is a common symptom encountered by ophthalmologists. Diagnoses such as posterior vitreous detachment (PVD), retinal breaks and detachment, and migraine will account for a large proportion of patients presenting with photopsia, but beyond these there remains a long list of differential diagnoses. The aim of this article is to highlight the wide variety of conditions that may give rise to photopsia and to highlight differentiating characteristics of this symptom that may help ophthalmologists to consider and identify the underlying pathology.