Robert E. Fusaro

Accuracy of videokeratography for instantaneous radius in keratoconus

PURPOSE Present videokeratographs provide corneal radius of curvature measurements in terms of axial (sagittal) radius and, for some instruments, instantaneous (tangential) radius. The EyeSys videokeratograph allows conversion from axial to instantaneous radius based on an algorithm, which assumes a basic corneal shape of elliptical form. METHOD We tested the accuracy of the EyeSys instantaneous radius algorithm for 29 keratoconic corneas using the criterion that instantaneous radius of the cone apex could be determined accurately by aligning the cone apex with the optic axis of the videokeratoscope. RESULTS There was a close relation between the instantaneous values obtained from the regular and apex alignments for the 17 eyes with cone apices below 55 D (95% limits of agreement -0.39 to 1.49 D), but not for the 12 eyes above 55 D (95% limits of agreement -4.87 to 6.61 D). The mean distance of the cone position from the center of the map was 1.16 mm for the instantaneous map and 1.59 mm for the axial map. CONCLUSION Assuming the criterion for accuracy to be the corneal radii found when the videokeratograph was aligned with the cone apex, the instantaneous map for the EyeSys videokeratograph at regular alignment provided reasonably valid measurements for corneas up to 55 D, but large errors existed for some corneas of higher power.

Epithelial permeability reflects subclinical effects of contact lens wear.

AIMS Recently, it was reported by the authors that a single drop fluorophotometric technique for estimating corneal epithelial permeability (Pdc) to fluorescein is not sufficiently precise for monitoring permeability changes in individual patients, but may be useful for evaluating mean differences in Pdc in population based research. To determine whether this technique provides a more sensitive index of epithelial integrity compared with conventional clinical assessments, the effects of mild corneal trauma on Pdc, the slit lamp appearance of the cornea, and corneal thickness (CT) were assessed. METHODS After baseline slit lamp examinations (SLE) and CT measurements, one randomly chosen eye of each of 32 normal subjects underwent 1 hour of closed eye soft contact lens (CL) wear while the fellow eye served as a control (no CL). After removing the CL, the SLE and CT measurements were repeated. Then, Pdc to fluorescein was assessed using a single drop fluorophotometric method refined to enhance feasibility, precision, and accuracy. RESULTS The mean (95% confidence interval) difference in natural log (Pdc) between 32 pairs of eyes (CL minus no CL) was 0.341 (0.069, 0.613), p = 0.016. By contrast, none of the 32 subjects exhibited corneal epithelial disruption upon SLE with white light following the closed eye period. Also, no substantial differences were apparent in the corneal swelling response between paired eyes, mean ΔCT (95% CI) = −2.31(−7.53, 2.91) μm, p=0.37. CONCLUSIONS Pdc measurements, used in studies of modest sample size, appear capable of detecting average differences in corneal barrier function that remain undetectable by SLE or pachymetry.

Cofactors for HIV disease progression in a cohort of homosexual and bisexual men.

Summary: To evaluate cofactors for progression of HIV infection, the authors identified 370 men with well‐defined seroconversion dates and cofactor data among participants in the San Francisco City Clinic Cohort (SFCCC). Postseroconversion substance use, sexual behavior, and sexually transmitted diseases were assessed using multivariate proportional hazards models. Weekly use of hallucinogens strongly and independently predicted death (relative hazard [RH], 2.59; 95% confidence interval [CI], 1.56‐4.28), as well as diagnosis of AIDS; weekly cocaine use also predicted mortality. Receptive anal intercourse with ejaculation was independently associated with mortality risk (RH, 1.45; 95% CI, 1.02‐2.04) and AIDS. The associations of accelerated progression with weekly use of recreational drugs and unprotected receptive anal intercourse need to be confirmed in other prospective cohorts.

Contact lens base curve prediction from videokeratography

Purpose To assess whether the contact lens to cornea-bearing relationship, as determined from the fluorescein pattern, can be predicted from videokeratography. Methods Nineteen non-rigid gas permeable (RGP) lens wearers were each tested for fluorescein patterns with a series of seven RGP contact lenses of different base curves, and compared to a theoretical estimate of the fitting relationship from videokeratography. The experimentally determined alignment lens was then compared to the theoretical alignment (TA) value as determined from the central curvature and eccentricity. Results The mean difference in lens choice between the TA and experimental alignment (EA) values was —0.01 ± 0.04 mm and between the simulated keratometric (KA) readings and the EA choice was 0.11 ± 0.05 mm. Conclusion A knowledge of the eccentricity value from videokeratography allowed a better prediction of the base curve to cornea relationship than was provided by only a central corneal measurement.

A Competing Risks Analysis of Presenting AIDS Diagnoses Trends

The proportions of gay men presenting with various AIDS diagnoses display temporal trends. In particular, the proportion of initial diagnoses reported as Kaposis sarcoma (KS) has declined over time. Epidemiologists have hypothesized that (a) KS may require a cofactor, whose prevalence has declined over time, or (b) KS may have a shorter incubation period than other presenting diagnoses. We examine whether this latter hypothesis, considered in a competing risks framework, could account for the observed decline in KS. We nonparametrically estimate the relevant cause-specific hazard functions from the doubly-censored data of the San Francisco City Clinic Cohort by maximizing a roughness penalized likelihood using an EM algorithm. These estimates suggest that differences in the underlying cause-specific hazard functions account for a substantial portion of the observed diagnoses trends.

The Berkeley Contact Lens Extended Wear Study: Part II: Clinical results

OBJECTIVE To describe the principal clinical outcomes associated with 12 months use of rigid gas-permeable (RGP) extended wear contact lenses and address two primary study questions: (1) does extended wear (EW) of high oxygen transmissibility (Dk/t) RGP lenses reduce the incidence of ocular complications, and (2) does the wearing of high-Dk/t lenses reduce the rate of failure to maintain 6-night RGPEW over 12 months? DESIGN A randomized, concurrently controlled clinical trial. INTERVENTION Subjects who adapted to EW with high Dk (oxygen permeability) RGP lenses were randomized to either high Dk or medium-Dk RGP lenses for 12 months of 6-night EW. MAIN OUTCOME MEASURES Contact lens-associated keratopathies (CLAK), changes in refractive error and corneal curvature, and survival in EW. RESULTS Two hundred one subjects were randomized to medium or high-Dk lenses for 12 months of EW. Sixty-two percent of the subjects in each group completed 12 months of EW; however, the probability of failure was significantly greater for the medium-Dk group. Although the risk of complications was similar for the two groups, the number of CLAK events that led to termination were 16 versus 5 for the medium-Dk and high-Dk groups, respectively. This suggests that the type of adverse response or the inability to reverse an adverse event was different for the group being exposed to the lower oxygen dose. CONCLUSIONS The level of oxygen available to the cornea has a significant impact on maintaining successful RGP extended contact lens wear, but not on the initial onset of CLAK. The number of clinical events leading to termination was substantially higher for the medium Dk group, which suggests that corneal hypoxia is an important factor in the development of CLAK. Although overnight contact lens wear should be recommended with caution and carefully monitored for early detection of ocular complications, it appears that high-Dk RGP lenses can be a safe and effective treatment for correction of refractive error for most individuals who can adapt to EW.

The Berkeley Contact Lens Extended Wear Study: part I: Study design and conduct

OBJECTIVE The primary aim of the Berkeley Contact Lens Extended Wear Study (CLEWS) was to test the hypotheses that extended wear of rigid gas-permeable (RGP) contact lenses with greater oxygen permeability (Dk) reduces the incidence of contact lens-associated keratopathy (CLAK) and increases the survival rate in RGP extended wear (EW). In this article we describe the clinical trial design in detail, present the results of subject recruitment and retention, and provide the baseline demographic and ocular characteristics of the CLEWS subjects, whose data will be analyzed to address the study aims in a companion article. DESIGN A randomized, concurrently controlled clinical trial. INTERVENTION Subjects were fitted with day wear (DW) high-Dk RGP lenses and then adapted to EW. Subjects who adapted to EW were then randomly assigned to either high- or medium-Dk RGP lenses for 12 months of 6-nights/week EW. MAIN OUTCOME MEASURES Slit-lamp assessment and grading of 17 possible keratopathies, measurement of refractive error and corneal curvature, and symptoms. Follow-up data were collected every 3 months. RESULTS From 545 subjects entering the DW adaptation phase, 201 adapted to EW and were randomly assigned to medium- or high-Dk lenses for 12 months of EW. The baseline characteristics of the two study groups were similar and did not differ from the 344 DW subjects who failed to adapt to EW. The distributions of oxygen transmissibility for the two study groups were disjoint, indicating that each group received distinctly different levels of hypoxia. CONCLUSIONS We show that CLEWS was appropriately designed to address the study hypotheses, was conducted with regard for the safety of the subjects, and adhered to rigorous protocols designed to control for bias and ensure the integrity of study data. We establish the internal validity of between-group statistical comparisons and characterize our study population to permit informed evaluation of the applicability of our results to the contact lens-wearing population in general.