Corneal swelling caused by conventional and new-design low-Dk soft contact lenses following a 10-day daily wear trial regime

Regional variations in corneal oedema during open-eye fenestrated scleral lens wear

PURPOSE

To compare the magnitude of central, mid-peripheral and peripheral stromal corneal oedema induced during short-term fenestrated and non-fenestrated scleral lens wear.

METHODS

Nine healthy participants wore a non-fenestrated and a fenestrated (0.3-mm diameter limbal fenestration) scleral lens (KATT™, Capricornia Contact Lenses), hexafocon B material (Dk 141 × 10-11 cm3 O2(cm)/[(s) (cm2) (mmHg)]) in one eye under open-eye conditions for 90 min on two separate days. Scleral lens thickness, fluid reservoir thickness and stromal corneal oedema were measured using high-resolution optical coherence tomography. Stromal oedema was quantified across the central (0-2.5 mm from the corneal apex), mid-peripheral (-3.0 to -1.0 mm from the scleral spur) and peripheral (-1.0 to 0 mm from the scleral spur) cornea with the lens in situ. The magnitude of oedema was corrected based on variations in fluid reservoir thickness between the lens conditions.

RESULTS

There was a significant effect of lens type (p = 0.04) on stromal oedema, with less oedema observed with the fenestrated (0.36 ± 0.45%) compared to the non-fenestrated lenses (1.24 ± 0.27%), averaged across all corneal locations. A significant lens type by corneal location interaction was also observed (p = 0.05), with less oedema observed in the peripheral region for the fenestrated (-0.15 ± 0.98%) compared to the non-fenestrated lenses (1.81 ± 0.57%) (p = 0.048). A fenestration location by corneal location interaction was also observed (p = 0.02), indicating a greater reduction in oedema closer to the fenestration.

CONCLUSIONS

Central and mid-peripheral stromal oedema was similar during fenestrated and non-fenestrated lens wear; however, fenestrated lenses displayed significantly less oedema in the peripheral cornea. This is most likely due to increased oxygen delivery in proximity to the fenestration.

Contact lens fenestrations and channels in relation to tear exchange and corneal oedema

Oxygen delivery and tear exchange are considered essential to maintain corneal homoeostasis during contact lens wear. Since the 1940s, fenestrations and back surface channels have been utilised in scleral, corneal rigid, and soft contact lenses in an attempt to enhance corneal oxygen transmission, facilitate the removal of carbon dioxide from the post-lens tear layer, minimise corneal oedema and prevent post-lens tear stagnation. This review examines the use of contact lens fenestrations and channels in both clinical and laboratory settings, and the effect of these modifications upon tear exchange and corneal oedema. Despite almost a century of modifying contact lenses to alter tear dynamics and promote corneal health, the evidence regarding the efficacy of fenestrations and channels is mixed.

Corneal oedema during open-eye fenestrated scleral lens wear

INTRODUCTION

Studies examining the effect of fenestrating soft and corneal rigid contact lenses upon corneal oedema have yielded conflicting results. Although often utilised in clinical practice, no studies have quantified the effect of fenestrating a scleral contact lens upon corneal oedema. Therefore, the aim of this experiment was to examine the effect of incorporating a single peripheral fenestration on central corneal oedema during short-term open-eye scleral lens wear, while controlling for potential confounding variables.

METHODS

Nine participants (mean age 30 years) with normal corneas wore a fenestrated (1 × 0.3 mm limbal fenestration) and non-fenestrated scleral lens (both lenses manufactured using a material Dk of 141 × 10-11  cm3 O2 (cm)/[(sec.)(cm2 )(mmHg)]) under open-eye conditions on separate days. Scleral lens thickness profiles were measured using a high-resolution optical coherence tomographer (OCT). Epithelial, stromal and total central corneal oedema were also measured using the OCT immediately after lens application and following 90 min of wear, prior to lens removal.

RESULTS

After adjusting for differences in initial central fluid reservoir thickness and scleral lens thickness between the two lens conditions, the mean (standard error) total corrected central corneal oedema was 0.50 (0.36)% for the fenestrated lens and 0.62 (0.16)% for the non-fenestrated lens. This small difference was not statistically significant (t8  = 2.31, p = 0.81) and represents a 19% relative reduction in central corneal oedema. Similarly, epithelial (t8  = 2.31, p = 0.82) and stromal (t8  = 2.31, p = 0.92) corneal oedema were not significantly different following the fenestrated and non-fenestrated wearing conditions.

CONCLUSION

Central corneal oedema in healthy corneas was comparable between fenestrated and non-fenestrated high Dk scleral lenses under short-term open-eye conditions when controlling for lens oxygen transmissibility and initial central fluid reservoir thickness.

Evaluation of corneal optical properties in subjects wearing hydrogel etafilcon A contact lenses and the effect of administering mannitol-enriched sodium hyaluronate ophthalmic solution

BACKGROUND

The purpose of this study was to evaluate the effect of daily administration of mannitol-enriched sodium hyaluronate ophthalmic solution on the corneal optical properties of subjects wearing low Dk hydrogel (etafilcon A) contact lenses (CLs).

METHODS

Forty-five subjects wearing etafilcon A CLs daily for more than 6 months were recruited into this pilot study. Fifteen of the subjects administered a 10% mannitol-enriched 0.05% sodium hyaluronate solution (study group) once daily and 30 subjects did not administer any ophthalmic solution (control group). The subjects were examined at baseline and one month after recruitment. Changes in central corneal thickness (CCT) and corneal light backscatter were evaluated by Scheimpflug imaging (Pentacam HR). Changes in corneal total high-order aberration, corneal spherical aberration, coma, and trefoil were evaluated using the OPD scan II.

RESULTS

At one month, corneal light backscatter decreased significantly in the study group (≤18.30 arbitrary units; P<0.05) and this was highly correlated with a decrease in CCT (R=0.81; P=0.04). The decrease in corneal total high-order aberration, spherical aberration, and coma was significantly higher in the study group than in the control group (P<0.05). No changes in corneal light backscatter or CCT were found in the control group during follow-up.

CONCLUSION

Once-daily administration of a mannitol-enriched lubricant ophthalmic solution was effective for improving the corneal optical quality and reducing corneal swelling in subjects wearing low Dk hydrogel (etafilcon A) CLs during one month follow-up.