Agreement and repeatability of the Sonogage ultrasound pachometer compared with a Mitutoyo micrometer.

PURPOSE: The agreement and repeatability of the Sonogage ultrasound pachometer was tested by comparing it with a Mitutoyo micrometer. METHODS: The thickness of five polymacon disks with thickness and ultrasonic properties similar to the human cornea and corneal epithelium were measured using both instruments. The mean values obtained using both instruments were compared and analyzed using a two-way analysis of variance, Bland-Altman analysis, and coefficient of variation. RESULTS: The measurements of the Sonogage were found to be statistically indistinguishable from the micrometer for all disks combined (p = 0.25) and for the disks with thicknesses similar to the corneal epithelium (p = 0.10), Bland-Altman analysis reveal limits of agreement for all thicknesses with a lower limit of -4.23 microm and upper limit of 5.27 microm. The coefficient of variation was <4% for each thickness. Bland-Altman plots of thin and thick disks exhibit no systematic difference between the average micrometer and Sonogage measurements. CONCLUSION: The measurements taken with the Sonogage pachometer are comparable with those taken with the micrometer when measuring polymacon disks with properties similar to corneal epithelium and total corneal thickness.

A pre-application drop containing carboxymethylcellulose can reduce multipurpose solution-induced corneal staining.

PURPOSE: Use of polyhexanide based multipurpose solutions (MPSs) for contact lens disinfection has been linked to low-grade corneal staining. In vitro data suggest that carboxymethylcellulose (CMC) may neutralize polyhexanides. The purpose of this investigation was to determine whether a pre-application drop of CMC reduces polyhexanide staining in vivo. METHODS: Thirty adapted soft contact lens (SCL) wearers participated in this investigator-masked, randomized, two-way cross-over study. Subjects wore a new Group II lens (alphafilcon A, 66% water) daily for 4 weeks and disinfected lenses using a MPS containing 0.0001% polyaminopropyl biguanide. A lens lubricant containing either CMC or povidone as the primary viscolyzer was applied to the lens each day before lens wear. Biomicroscopic signs and symptomatology were assessed. The difference in scores, 0 to 4 weeks and the difference between lubricants were analyzed. RESULTS: The cumulative fluorescein staining scores for combined eyes demonstrated a significant increase over time (e.g., cumulative staining score; p=0.004 and p<0.001 for CMC and povidone, respectively, matched pairs t-test, two-tailed), suggesting that for both lubricants the staining worsened with wear. This effect was expected and likely driven by the MPS. However, the mean cumulative staining scores for CMC and povidone were 2.8 and 2.6 out of 20 possible at baseline, increasing to 4.9 and 7.1 at 4 weeks, respectively. The increases were significantly different (p=0.003, matched pairs t-test, two-tailed) suggesting a greater increase in corneal staining for the povidone lubricant. The symptom scores were not significantly different, 0 to 4 weeks by regimen or between preinstillation drops. CONCLUSIONS: These results suggest that a CMC-containing preapplication drop can reduce corneal staining resulting from disinfection with a polyhexanide MPS. This result is consistent with a proposed mechanism for CMC to neutralize cationic disinfectants and may offer clinicians another means to reduce this type of corneal staining.

Overnight orthokeratology: preliminary results of the Lenses and Overnight Orthokeratology (LOOK) study.

BACKGROUND: The Lenses and Overnight Orthokeratology (LOOK) study is a pilot study designed to learn the procedures of orthokeratology lens fitting in preparation for a planned larger clinical trial and to obtain data with which to calculate a sample size for that larger study. Data are presented for the first 3 months of the LOOK study. METHODS: Sixty subjects were enrolled in this multicenter pilot study to evaluate the success and safety of treatment with overnight orthokeratology contact lenses. Refractive error, corneal topography, and biomicroscopic data were collected to determine the amount of refractive error change achieved, corneal changes, and a safety profile of overnight wear of reverse geometry rigid gas permeable lenses for orthokeratology. RESULTS: Of the 60 subjects enrolled, 46 completed the 1-month visit, and 31 completed the 3-month visit. The mean change in spherical equivalent manifest refraction from baseline to the morning 3-month visit was 2.08 +/- 1.11 D in the right eye and 2.16 +/- 1.05 D in the left eye. At the 3-month morning visit, 74% of right eyes and 61 % of left eyes had 20/20 unaided visual acuity. No corneal infiltrates or ulcers were noted in any subjects. Observations of fluorescein staining of the cornea, imprinting, and microcysts were noted in some patients at the 3-month visit. CONCLUSIONS: The preliminary results of the LOOK study indicate that improvement in unaided visual acuity can be attained for at least 6 h after lens removal. The short-term safety and efficacy of the procedure appear to be favorable; however, future studies are needed to determine the long-term outcomes of treatment.