Rehabilitating the Hypoxic Cornea: Transitioning from PMMA to High Dk Contact Lens Materials

The introduction of oxygen-permeable rigid gas permeable (RGP) lenses marked a significant turning point in the history of contact lens wear. Prior to their development in the late 1970s, polymethyl methacrylate (PMMA) lenses dominated clinical practice. PMMA is entirely impermeable to oxygen, and while its optical clarity and mechanical durability were unmatched for decades, the physiological burden placed on the cornea by prolonged wear of these lenses became increasingly evident. Chronic corneal hypoxia was an inevitable consequence of PMMA lens wear, leading to a series of metabolic, structural, and functional changes in the cornea that persist long after lens removal.When transitioning a long-term PMMA wearer to a modern high Dk RGP material, the clinician must not only consider the optics and fit but also the underlying metabolic state of the cornea. Understanding the cellular and biochemical consequences of hypoxia—and the challenges associated with sudden reoxygenation—is essential to ensuring a successful and comfortable adaptation to new lens materials.