Cling film as a barrier against CJD in Goldmann-type applanation tonometry

Repeatability, reproducibility, agreement, and safety of Tono-Pen tip cover for intraocular measurement using latex and polyethylene wrap

PURPOSE

To evaluate repeatability, reproducibility, and agreement of intraocular pressure measurement with Tono-Pen using Ocufilm and polyethylene wrap tip cover in human eyes.

METHODS

This is a cross-sectional, experimental study. A gas-sterilized, polyethylene wrap was used as an alternative for Tono-Pen tip cover. For the right eye, 4 measurements using polyethylene wrap tip cover were done by two examiners (A and B) in random order to assess intra-observer repeatability and inter-observer reproducibility. For the left eye, 4 measurements were done by examiner A using both polyethylene wrap tip cover and Ocufilm in random order to assess intra-observer repeatability and agreement. Bland-Altman plot and intraclass correlation coefficient (ICC) were used in all analyses. Cost minimization analysis was evaluated.

RESULTS

For examiner A, the repeatability of polyethylene wrap tip cover was -0.34, 95% limits of agreement (LOA) were -3.04 to 2.36, and ICC was 0.93 in the right eyes. As for the left eyes, the repeatability of polyethylene wrap tip cover was -0.33, 95% LOA were -3.01 to 2.36, and ICC was 0.93. For examiner B, the repeatability of polyethylene wrap tip cover was -0.02, 95% LOA were -2.88 to 2.83, and ICC was 0.92. The inter-observer reproducibility of polyethylene wrap tip cover was 0.36, 95% LOA were -3.34 to 4.07, and ICC was 0.90. The repeatability of Ocufilm was -0.42, 95% LOA were -2.75 to 1.91, and ICC was 0.95. The agreement of polyethylene wrap tip cover and Ocufilm was -0.71, 95% LOA were -5.18 to 3.76, and ICC was 0.83. There were no allergic reactions or serious complications. From the cost minimization analysis, the local cost for polyethylene tip cover was approximately 8 times lower compared to Ocufilm.

CONCLUSIONS

Tono-pen with Ocufilm and polyethylene wrap tip cover were used to measure the intraocular pressure. The polyethylene wrap tip cover demonstrated acceptable repeatability, reproducibility, and agreement with Ocufilm in normotensive eyes, and had a good safety profile.

Ocular Tonometry and Sporadic Creutzfeldt - Jakob Disease (sCJD): A Confirmatory Case-Control Study

AIMS

To evaluate the hypothesis that sporadic Creutzfeldt-Jakob disease (sCJD) may be transmitted through ocular tonometry.

BACKGROUND

The infectious agent of sCJD may be present in the cornea prior to clinical symptoms. Cornea infectiousness has been documented by cornea transplants in guinea pigs and humans. sCJD is resistant to complete inactivity by conventional sterilization techniques. Thus contact tonometry equipment is not disinfected sufficiently to kill sCJD. We previously hypothesized that contact tonometry is a sCJD risk factor.

STUDY DESIGN

Population-based case-control study.

PLACE AND DURATION OF STUDY

Department of Neurology, School of Medicine, Loma Linda University, Loma Linda, CA, USA; 4 years.

METHODOLOGY

An 11-state case-control study of pathologically confirmed definite sCJD cases, individually matched controls, and a sample of control surrogates was conducted. Ocular tonometry histories were obtained from case-surrogates, controls, and a sample of control-surrogates.

RESULTS

The odds ratio (OR) for ever vs never having had an ocular tonometry test was statistically significant for matched and unmatched analyses for 15 through 3 years prior to disease onset, using both control self-responses and control surrogates: ORs were ∞ and 19.4 with 1-sided P-values <0.0001 and 0.003 and ORs=∞ and 11.1 with 1-sided P-values <0.003 and 0.02, respectively. ORs increased as the number of tonometry tests increased during this age period: trend test, 2-sided P-value < 0.0001. For ≥5 vs <5 tonometry tests, the OR was 5.8 (unmatched) and 3.7 (matched), 2-sided P-value<0.00005. Respondents generally could not specify the type of tonometry. There was no indication of increased tonometry testing among cases within 2 years of disease onset.

CONCLUSIONS

The a priori hypothesis was supported. Contact tonometry, preferred by ophthalmologists, may be capable of transmitting sCJD. Consideration should be given to using disposable instrument covers after each use. The use the disposable covers or non-contact tonometry is preferable in the absence of effective disinfectant processes at this time.

Does rebound tonometry probe misalignment modify intraocular pressure measurements in human eyes?

Purpose. To examine the influence of positional misalignments on intraocular pressure (IOP) measurement with a rebound tonometer. Methods. Using the iCare rebound tonometer, IOP readings were taken from the right eye of 36 healthy subjects at the central corneal apex (CC) and compared to IOP measures using the Goldmann applanation tonometer (GAT). Using a bespoke rig, iCare IOP readings were also taken 2 mm laterally from CC, both nasally and temporally, along with angular deviations of 5 and 10 degrees, both nasally and temporally to the visual axis. Results. Mean IOP ± SD, as measured by GAT, was 14.7 ± 2.5 mmHg versus iCare tonometer readings of 17.4 ± 3.6 mmHg at CC, representing an iCare IOP overestimation of 2.7 ± 2.8 mmHg (P < 0.001), which increased at higher average IOPs. IOP at CC using the iCare tonometer was not significantly different to values at lateral displacements. IOP was marginally underestimated with angular deviation of the probe but only reaching significance at 10 degrees nasally. Conclusions. As shown previously, the iCare tonometer overestimates IOP compared to GAT. However, IOP measurement in normal, healthy subjects using the iCare rebound tonometer appears insensitive to misalignments. An IOP underestimation of <1 mmHg with the probe deviated 10 degrees nasally reached statistical but not clinical significance levels.

Clinical evaluation of rebound tonometer

PURPOSE

To evaluate the reliability and repeatability of intraocular pressure (IOP) measurements using a new rebound tonometer.

METHODS

Intraocular pressure was measured in 42 healthy human eyes of subjects aged 18-30 years (mean +/- standard deviation [SD] 21.5 +/- 3.2 years) using the ICare Rebound and Goldmann tonometers in two separate sessions.

RESULTS

Intraocular pressure measurements were found to read slightly, but not significantly, higher with the ICare tonometer compared with the Goldmann instrument in both sessions (first session: mean bias +/- SD + 0.50 +/- 2.33 mmHg; second session: mean bias +/- SD + 0.52 +/- 1.92 mmHg). Limits of agreement between repeated readings were +/- 5.11 mmHg for measurements taken with the ICare tonometer, compared with +/- 3.15 mmHg for measurements taken with the Goldmann method.

CONCLUSION

Measurement of IOP in normal, healthy subjects using the ICare rebound tonometer produced a small, statistically insignificant, positive bias when compared with the Goldmann tonometer. Intersessional repeatability of IOP taken with the ICare is poorer than that of IOP taken with the Goldmann tonometer, but is comparable with that of other non-Goldman-type tonometers currently available.

Three portable tonometers, the TGDc-01, the ICARE and the Tonopen XL, compared with each other and with Goldmann applanation tonometry*

Three portable tonometers, the TGDc-01, the ICARE and the Tonopen XL, were compared with each other and to Goldmann applanation tonometry in a large group of healthy subjects and patients with ocular hypertension or glaucoma (n = 103). Measurements performed with the ICARE and the Tonopen XL were in good agreement with that of the Goldmann tonometer. Intraocular pressure (IOP) values measured with the TGDc-01 were significantly lower and showed more variability. The 95% limits of agreement (portable tonometer - Goldmann) were -17 to +10 mmHg for the TGDc-01, -6 to +7 mmHg for the ICARE and -6 to +8 mmHg for the Tonopen. Corneal thickness could not explain the differences between an IOP measured with the portable tonometers and an IOP measured with the Goldmann tonometer. Patient comfort was slightly higher for ICARE when compared with the Tonopen.