Corneal thickness results in the Menicon Z 30-day continuous wear and ACUVUE 7-day extended-wear contact lens clinical trial

Contact lens-induced corneal peripheral swelling differences with extended wear

PURPOSE

To compare central and peripheral corneal swelling with high-Dk (lotrafilcon A) and low-Dk (etafilcon A) contact lenses (CLs) during extended wear (EW).

METHODS

Corneal thickness was measured in 5 corneal locations (central, superior, inferior, nasal, and temporal) with Orbscan II pachymetry 1 week before the wearing of CLs and after 1 week of EW. High-Dk (lotrafilcon A) and low-Dk (etafilcon A) soft CLs were randomly fitted for EW in the right and left eyes of 20 subjects with normal ocular health. Orbscan was also performed before CL removal after 3 and 7 days of EW.

RESULTS

Lotrafilcon A induced a lower percentage of corneal swelling in all 5 corneal locations than etafilcon A (P < 0.05, paired t test). Lotrafilcon A swelling percentages were as follows: central (1.67% +/- 2.22%), superior (2.04% +/- 3.25%), inferior (1.38% +/- 1.74%), nasal (1.50% +/- 2.00%), and temporal (1.27% +/- 1.47%). Etafilcon A swelling percentages were as follows: central (4.98% +/- 3.07%), superior (6.62% +/- 8.39%), inferior (5.24% +/- 5.54%), nasal (3.41% +/- 3.14%), and temporal (4.46% +/- 3.32%). Differences between the central and peripheral corneal swelling during EW of both types of lenses were not significant (P > 0.05, repeated-measures analysis of variance).

CONCLUSIONS

Central and peripheral corneal thicknesses increase more with etafilcon A than with lotrafilcon A during EW, as measured by Orbscan pachymetry.

Investigation of the performance of the Menifocal Z gas-permeable bifocal contact lens during continuous wear

PURPOSE

The Menifocal Z is an alternating vision, concentric, bifocal gas-permeable (GP) contact lens; center distance is connected to near periphery by a smooth transition zone. The lens is produced using tisilfocon A (Menicon Z material), which is approved for up to 30 days of continuous wear (CW). The aim of this study was to evaluate the clinical performance of the Menifocal Z when worn for up to 30 days of CW for 6 months.

METHODS

Thirty-five existing GP lens wearers were enrolled in the study. Subjects were fitted with Menifocal Z lenses and follow-up visits were conducted after 2 weeks of daily wear and 1 day, 1 week, 6 weeks, 3 and 6 months of CW. A range of objective and subjective clinical performance measures were assessed, including distance and near visual acuity, the physiological response to CW, and subjective evaluation of vision and comfort.

RESULTS

Twenty-seven subjects (77%) completed the study and eight (23%) discontinued: five (14%) as a result of lens-related problems (four vision, one comfort) and three (9%) as a result of non-lens related reasons. Average CW time achieved by the subjects was 22 +/- 2 days. Mean binocular logarithm of the minimum angle of resolution (logMAR) acuities at 6 months were: high contrast distance 0.03 (20/20-), low contrast distance 0.63 (20/80-), and high contrast near 0.26 (20/25, N4). Adverse responses and lens binding were minimal, and there were no significant increases in corneal staining, corneal vascularization, or superior palpebral conjunctival papillae over time (p > 0.05). Problems with night vision (distance and near) with the lenses were the most common difficulties reported by the subjects.

CONCLUSIONS

The Menifocal Z appears to be a promising option for presbyopic vision correction, providing successful correction of distance and near vision in a group of experienced GP lens wearers. The hyper Dk tisilfocon A (Menicon Z) material allowed for safe wear of the lenses on a CW basis.

Short-Term Adaptation of the Human Corneal Endothelium to Continuous Wear of Silicone Hydrogel (Lotrafilcon A) Contact Lenses After Daily Hydrogel Lens Wear

PURPOSE

The purpose of this study is to assess whether improved oxygen availability to the cornea resulted in changes in the corneal endothelium.

METHODS

Eighteen adult (average age 25.3 +/- 5.1 years) hydrogel lens wearers (average of 5.5 years prior daily lens wear, range 3-9 years) were refitted with silicone hydrogel lenses (Focus Night and Day) for continuous wear over 30 days and nights. They were assessed in detail immediately before the refit (baseline measures) and again after 6 months of wear with lens replacement every 30 days. Assessments included slit biomicroscopy (for grading of limbal and bulbar redness), corneal staining with fluorescein, and then by noncontact specular microscopy for central corneal thickness (CCT) and endothelial cell layer images. The endothelial images exported as JPEG files and printed at 7000x magnification. The cell-cell borders were marked and then the areas of an average of 255 cells/image measured with a digitizer pad in stream mode. The number of cell sides was also counted.

RESULTS

After 6 months of silicone hydrogel lens wear, most subjects showed an improvement in mean bulbar (1.1 to 0.9) and limbal redness (1.0 to 0.6, p < 0.001) and epithelial fluorescein staining (0.5 to 0.3) grades, and the mean CCT values decreased slightly in most subjects (0.527 to 0.520 mm), although the decrease was not statistically significant (p = 0.565). The mean endothelial cell area also increased slightly (358 to 363 microm2; p nonsignificant [NS] = 0.701), whereas the mean coefficient of variation (COV) decreased slightly (30.2 to 29.1%, p NS = 0.357). The calculated mean endothelial cell density (ECD; area/1000000 microm2) also decreased slightly from 2821 to 2774 cells/mm, but this change also was not statistically significant (p = 0.620). However, the changes in ECD showed a very substantial relationship to the changes in CCT, i.e., as CCT decreased, so the apparent ECD decreased; this change was highly significant (r = 0.747, p < 0.001). This relationship was slightly stronger still when possible image magnification differences were corrected for. The percentage of six-sided ("hexagonal") cells increased slightly (58.3 to 60.1%).

CONCLUSION

The results indicate that, in silicone hydrogel lens wearers exhibiting positive external eye signs thought to be associated with improved oxygen availability, subtle morphologic changes (marginally decreased polymegethism and pleomorphism) in the central region of the corneal endothelium can occur. It remains to be established, however, whether these changes can be directly attributed to oxygen effects (reduced hypoxia and hypercapnia altering the endothelial cells) or to a mechanical effect (in which changes in corneal thickness result in a reorganization of the corneal endothelium).

A 6-month follow-up of successful refits from daily disposable soft contact lenses to continuous wear of high-Dk silicone-hydrogel lenses

PURPOSE

To compare, in routine optometric practice, the outcome of keeping successful soft contact lens (SCL) wearers in their lenses to re-fitting them with continuous wear of silicone hydrogel (SiH) lenses.

METHODS

Forty-nine successful daily disposable lens wearers were recruited; 19 continued to wear daily SCLs and 30 were refitted with high-Dk SiH lenses on a 30-day/night schedule. Patients were assessed at baseline, 3 and 6 months by slit lamp examination along with the Efron grading scales, and central corneal thickness (CCT) and the corneal endothelium were assessed by non-contact specular microscopy.

RESULTS

No substantial changes in subjective vision, refraction, visual acuity or overall lens comfort occurred for those completing the study, although five SiH lens wearers did discontinue due to reduced comfort, eyelid problems or seasonal allergy. Contact lens induced peripheral ulcers (CLPU) were observed in three patients in the first 3 months in the SiH lens group and these were also discontinued. Over the 6 month period, a complete set of records was obtained for 16 in each group. For those completing the study, lens dryness scores were variable, but there was a slight improvement in favour of SiH lenses. Small, but statistically significant, reductions in corneal staining, bulbar hyperaemia, and limbal neovascularisation in favour of the SiH lenses were also evident but mainly because of further increases in the daily lens wearers. Contact lens induced papillary conjunctivitis (CLPC) and corneal endothelial polymegethism were mild to moderate and showed slight increases in the daily lens wearers at 6 months.

CONCLUSIONS

The present studies confirm that the continuous wear of SiH lenses for up to 30 days can be considered as an alternative to daily disposable soft lens wear, but is not suitable for everyone.

Effects of Contact Lenses on Corneal Thickness and Corneal Curvature During Usage

PURPOSE

To investigate the effects of contact lenses on corneal thickness and curvature.

METHODS

Eighty-four eyes of 45 patients (26 female and 19 male) wearing contact lens for the first time with a median age of 23.04 +/- 7.2 years (range, 15-44 years) were included in the study. After all patients had undergone a routine ophthalmic examination, corneal thickness measurements in nine regions and corneal topography were performed before wearing contact lenses and after 1 month, 6 months, and 12 months. Patients were classified into three groups according to duration of wear. Groups were also classified into two subgroups according to the lens type (rigid gas-permeable and soft contact lenses).

RESULTS

Mean visual acuity was 0.82 +/- 0.26 with spectacles and 0.92 +/- 0.26 with contact lenses. At the end of 1 month, statistically significant corneal thinning and thickening were noted in different regions in group 1. In group 2, statistically significant corneal thinning was noted in all regions with soft contact lenses and rigid gas-permeable contact lenses except in the inferior temporal region at the end of 6 months. In group 3, corneal thinning was noted in all regions with soft contact lenses and rigid gas-permeable contact lenses. This corneal thinning was statistically significant in all regions with the soft contact lenses except in the inferior nasal region and with rigid gas-permeable contact lenses except in the central region. When corneal curvatures were examined, corneal flattening was seen in groups 1 and 2. In group 3, corneal steepening was noted.

CONCLUSIONS

Soft contact lenses and rigid gas-permeable contact lenses cause corneal thickening and corneal flattening in the first months, but they cause corneal thinning and corneal steepening with time. These alterations can be evaluated as evidence that contact lenses negatively influence corneal physiology.