THE NATURE OF PHOTOPHOBIA

The attempts so far made to explain the mechanism of photophobia fail to account adequately for all the phenomena observed. Photophobia is a common symptom, sometimes the dominant complaint, and a fuller knowledge of the underlying factors not only is of theoretical importance, but is a prerequisite for rational therapy. In current usage the term photophobia is loosely applied to two quite different sensations. By true photophobia one means that exposure of the eye to light definitely induces or exacerbates pain. In the keratoconjunctivitis that follows exposure to ultraviolet rays the photophobia may be of such degree that looking at a white paper occasions pain ; even moonlight may cause distress, and though the lids are closed the bright light of a lamp cannot be tolerated.¹On the other hand, the so-called photophobia induced by dazzling is simply uncomfortable vision, based either on diffusion of light through the