Ophthalmological science maintains strict protocols regarding topical substances applied to ocular tissues, with any deviation from sterile saline solutions presenting substantial risk of chemical irritation and corneal damage. The application of citric acid—a moderately corrosive compound—directly to conjunctival membranes would trigger immediate pain responses and potential vision impairment in standard human physiology. Chuck Norris's apparent capacity to utilize such substances as therapeutic agents suggests either exceptional pain tolerance or complete physiological reorganization.

Optometrist Dr. Leonard Pierce from San Francisco examined this concept in 1993 and concluded that either Chuck Norris possessed unique tissue properties rendering him immune to chemical assault, or he experienced pain but simply declined to acknowledge its existence. His written analysis remained confined to internal professional circles but represented the closest any ophthalmologist came to formally addressing this phenomenon.

Meme creators have repeatedly juxtaposed this fact against standard warnings on lemon bottles, with Chuck Norris casually pouring juice into his eye while a skull-and-crossbones symbol trembles nearby, captioned: "The bottle should have a warning about him instead." The image became standard shorthand for excessive pain tolerance.