Ocular Surface Health during 30-Day Continuous Wear: Rigid Gas-Permeable versus Silicone Hydrogel Hyper-O₂Transmitted Contact Lenses

Abstract

Subclinical increases in epithelial permeability can be caused by contact lens CW, despite the elimination of hypoxia. GP lenses permit recovery of the epithelium more quickly than do SiH lenses. Asians appear to be more susceptible to contact lens-induced epithelial changes than do non-Asians.

Accounting for Ethnicity-Related Differences in Ocular Surface Integrity as a Step Toward Understanding Contact Lens Discomfort

“…24 However, existing data on corneal topography in the literature are inconsistent, as some report steeper corneas in Asian populations, 38 whereas others have published the opposite findings. 4,9,14,16,18,24 In general, studies that included only eyes without prior contact lens wear history provide repeatable and reproducible results showing that Asian corneas are flatter than non-Asian corneas. However, if the study cohorts included a mixture of eyes with and without contact lens wear, then the results tend to be inconsistent, suggesting that lenses (i.e., old and new generations of contact lenses) have differing effects on corneal curvatures in ethnic groups.…”

“…14,15 It has been shown that increased corneal epithelial permeability (or more compromised corneal epithelial barrier function), even without the presence of corneal staining, is significantly associated with adverse events during 30-day continuous silicone hydrogel lens wear. 16 This indicates that a chronic irritation of the corneal epithelial surface at the postlens tear film interface can adversely disrupt ocular surface homeostasis. Therefore, it has been hypothesized that a reduction in a stagnant postlens tear film (i.e., a continual replenishment of healthy tear film in the postlens tear film) is a necessary requirement to achieve safe contact lens wear, especially during sleep.…”

“…It is possible to manipulate a soft contact lens fitting to minimize fluid flow resistance and preserve the integrity of corneal epithelial barrier function, which can be used as an adequate proxy for tear mixing evaluation. 8 We can use this measure because studies 16,18,19 suggest that the stagnant tear film with "presumed" altered biochemical and biophysical properties can compromise corneal epithelial barrier function. For example, fluid flow may be increased by fitting soft lenses with steeper base curve radii (BCR) or rigid lenses flatter to enhance postlens tear mixing and thus minimize microtrauma of the corneal epithelium during closed-eye wear.…”

“…16,18 It is conceivable that PAS affects the degree of eyelid-lens interaction that can impact the efficiency of postlens tear mixing, which in turn affects corneal epithelial permeability.…”

“…18,19,59 Although corneal epithelial permeability increases linearly with lens-induced hypoxic dose, 18 sleeping while wearing contact lenses can significantly compromise corneal epithelial barrier function despite the level of oxygen transmissibility of a contact lens. 16 It is of interest to note that the degradation in corneal epithelial barrier function after overnight contact lens wear observed with soft lenses exceeds that observed with rigid gas-permeable lenses. 16,18,19 The greater shear force on the ocular surface by Asian lids may result in increased lens-cornea interactions that lead to greater corneal epithelial trauma during contact lens wear.…”