What Is a Non-Scleral Contact Lens?

How Do "Soft" Non-Scleral Lenses Maintain Eye Hydration?

Standard non-scleral soft lenses are made of hydrogel or silicone-hydrogel materials that are "spongy" and hold water. Because these lenses rest directly on the cornea they must maintain a constant "tear exchange" to keep the eye healthy. Every time you blink the lens shifts slightly allowing fresh tears to circulate beneath the plastic. Data indicates that modern silicone non-scleral lenses allow for nearly 100 percent of the available atmospheric oxygen to reach the eye, which is a primary requirement for preventing "corneal swelling" and chronic redness. [Image showing a soft contact lens resting on the cornea versus a scleral lens vaulting it]

What are the Primary Success Data Trends for "RGP" Lenses?

Rigid Gas Permeable (RGP) lenses are a specific type of non-scleral lens that provides the sharpest vision for astigmatism. Statistics show that 9 out of 10 RGP wearers achieve "sharper than 20/20" vision because the hard plastic creates a perfectly smooth optical surface. However because the lens is small and sits on the cornea it has a "lens awareness" period of nearly two weeks. Data suggest that once adapted RGP wearers have a 30 percent lower risk of "Infectious Keratitis" compared to soft lens wearers because the non-scleral rigid design does not "absorb" bacteria and proteins.

Why Is the "Corneal Diameter" Critical for Fitting?

Fitting a non-scleral lens requires a precise measurement of the "Horizontal Visible Iris Diameter" (HVID). The lens must be large enough to cover the pupil but small enough not to "tuck" under the eyelids or rub against the limbus. Statistics show that nearly 15 percent of "Contact Lens Failure" is caused by an incorrectly sized non-scleral lens that is too tight. Identifying the correct "Base Curve" and "Diameter" using corneal topography is mandatory for ensuring the lens doesn't "choke" the corneal stem cells.

What is the Role of "Daily Disposables" in Non-Scleral Safety?

The newest frontier in non-scleral care is the "Daily Disposable" modality. Because the lens is thrown away every night there is zero opportunity for "biofilms" or allergens to build up on the eye. Data indicates that "Daily" wearers have a 40 percent lower rate of "Giant Papillary Conjunctivitis" (GPC) than those who reuse their lenses for two weeks or a month. This has made the daily non-scleral lens the primary recommendation for any patient with seasonal allergies or a history of "red eye" events.

How Do Clinicians Use "Slit-Lamp" Data to Check Lens Health?

To ensure a non-scleral lens is safe the doctor performs a "Fluorescein Evaluation" during the exam. A yellow dye is added to the eye and the doctor watches how the lens "floats" under a blue light. If the lens is "stuck" and does not move when you blink it is a definitive data point that the eye is "starving" for oxygen. Tracking this "lens lag" in millimeters is a mandatory clinical skill for preventing "Corneal Neovascularization," a condition where blood vessels grow into the clear eye and cause permanent blindness.