Used as a photochromic dye in ophthalmic lenses and specialty optical materials. It exhibits a reversible color change when exposed to UV light, making it ideal for transition lenses that darken in sunlight and return to clear indoors. The compound provides fast response time, good fatigue resistance, and a neutral gray or brown hue in its activated state, which is desirable for accurate color perception. Also employed in novelty items, sensors, and adaptive coatings where light-responsive behavior is needed.