Photorefractive keratectomy

Photorefractive keratectomy emerged from the collision of two separate research trajectories: IBM's development of excimer lasers for computer chip manufacturing and ophthalmology's long quest to reshape the cornea for vision correction. The moment of convergence came in 1981 when Rangaswamy Srinivasan at IBM's Thomas J. Watson Research Center discovered that 193nm argon fluoride excimer laser pulses could remove tissue with extraordinary precision—ablating material layer by layer without thermal damage to surrounding tissue.

The adjacent possible crystallized through an unlikely collaboration. Steven Trokel, a Columbia University ophthalmologist, learned of Srinivasan's work through a colleague and immediately recognized its potential for corneal surgery. In 1983, Trokel, Srinivasan, and their colleague Bodil Braren published the foundational paper in the American Journal of Ophthalmology demonstrating that excimer lasers could precisely ablate corneal tissue in cadaver eyes. This wasn't incremental improvement—it was a paradigm shift from mechanical cutting to photochemical ablation.

The 193nm wavelength proved critical. Unlike longer wavelengths that penetrate and heat tissue, the argon fluoride excimer's ultraviolet photons break molecular bonds directly, ejecting material as a fine plume without affecting adjacent cells. Each pulse removes approximately 0.25 micrometers of tissue with sub-micron precision—enabling reshaping of the cornea to correct myopia, hyperopia, and astigmatism.

Theodor Seiler performed the first PRK procedure on a human eye in Berlin in 1987, treating a blind patient's eye to demonstrate safety before proceeding to sighted patients. His systematic clinical trials established the safety profile and predictability that regulatory approval would require. The procedure's elegance lay in its simplicity: remove the epithelium, apply precisely calculated laser pulses to reshape the underlying stroma, and allow natural healing.

Path dependence shaped PRK's trajectory. When LASIK emerged in the early 1990s—creating a corneal flap rather than removing epithelium—it offered faster visual recovery and quickly dominated the market. PRK's longer healing time relegated it to a secondary option, though it retained advantages for patients with thin corneas or those in contact sports where flap displacement posed risks.

The FDA approved the VISX excimer laser system for PRK in October 1995, making the United States one of the last major markets to authorize the procedure. By then, millions of procedures had been performed worldwide. The cascade continues: PRK principles underpin LASIK, LASEK, and surface ablation variants. By 2026, refractive surgery has corrected vision for over 40 million people globally—each one benefiting from Srinivasan's discovery that ultraviolet light could sculpt living tissue with the precision of a master craftsman.