Thermal injury to the retina is more common in short exposures to near infrared radiation.

• A. False
• B. True
• C. Only with long exposures
• D. Only with visible light

Answer: (B)

Thermal damage to the retina from near-infrared light is driven by rapid heating when energy is delivered in a short, high-irradiance burst. Near-IR is absorbed by retinal melanin and tissue water, converting light to heat. The retina can’t dissipate that heat instantly, so a brief, intense exposure causes a rapid temperature rise that can coagulate retinal tissue. If the exposure is longer, heat has more time to diffuse away, raising the injury threshold, so damage is less likely for the same total energy. Because of this, short exposures to near-infrared radiation are more likely to cause thermal retinal injury.