Correlation of central corneal thickness measurements using Topcon TRK-1P, Zeiss Visante AS-OCT and DGH Pachmate 55 handheld ultrasonic pachymeter

Comparison of central corneal thickness measured by automatic and manual analysis of optical coherence tomography

PURPOSE

To compare central corneal thickness (CCT) measured with optical coherence tomography (OCT) using an automatic algorithm (A-OCT) vs. manual measurements (M-OCT) with respect to the gold standard ultrasound pachymetry (USP).

METHODS

CCT measurements were performed on both eyes of 28 healthy subjects at four times of the day. A-OCT used an automatic software analysis of the corneal image, M-OCT was performed by two operators by setting a digital calliper on the corneal borders, and USP was performed after corneal anesthesia. Measurements were compared using a three-way repeated measures ANOVA. Bland-Altman plots were used to evaluate the agreement between OCT measurements and USP.

RESULTS

Both A-OCT and M-OCT significantly underestimated the USP measures, with the mean difference, i.e., the systematic error, being larger for A-OCT (- 19.0 µm) than for M-OCT (- 6.5 µm). Good reproducibility between the two operators was observed. Bland-Altman plots showed that both OCT methods suffered from proportional errors, which were not affected by time and eye.

CONCLUSIONS

Measuring CCT with OCT yielded lower values than USP. Therefore, clinicians should be aware that corneal thickness values may be influenced by the measurement method and that the various devices should not be used interchangeably in following up a given patient. Intriguingly, M-OCT had less systematic error than A-OCT, an important outcome that clinicians should consider when deciding to use an OCT device.

Comparison of Central Corneal Thickness Measurements by Contact and Non-contact Pachymetry Devices

AIM AND OBJECTIVE

To compare central corneal thickness (CCT) measurements obtained by handheld contact ultrasound pachymetry (HCUP) and non-contact pachymetry devices.

MATERIALS AND METHODS

Ninety eyes of 90 patients (52 male and 38 female) were included in the study. Measurements from two non-contact devices, -specular microscopy (SM, Konan Medical, CA, USA) and Oculus Pentacam (Oculus Inc., Germany)-were compared against HCUP (Pachmate 2, DGH Technology, Inc, PA, USA). Ultrasound measurements were obtained 3 times by the same user and averaged. The differences were calculated by one-way ANOVA. Agreement between measurements were assessed by Bland-Altman plots and intraclass correlation coefficient tests. Coefficient of repeatability (%, CR) was defined as 1.96*standard deviations of the differences between pairs of measurements divided by the average of the means.

RESULTS

The mean age was 34.31 ± 14.39 (14-74) years, and the mean intraocular pressure was 16.48 ± 2.63 mm Hg (12-21). Mean CCT measured by HCUP, SM, and Pentacam was 557.76 ± 36.76 μm, 550.29 ± 43.74 μm, and 541.41 ± 35.7 μm, respectively (p < 0.05). In the Bland-Altman plot, 95% limit of agreements were 19.5 and 14.18 μm among HCUP measurements, 34.55 μm between HCUP and Pentacam, 41.49 μm between SM and Pentacam, and 46.98 μm between HCUP and SM. CR values (%) were 3.49, 2.54, 6.28, 7.68, and 8.47, respectively.

CONCLUSION

There were significant differences between the mean CCT values of the measurement devices.

CLINICAL SIGNIFICANCE

Contact and non-contact devices may not interchangeable in the clinical assessment of CCT.

HOW TO CITE THIS ARTICLE

Mayali H, Altinisik M, Diri I, et al. Comparison of Central Corneal Thickness Measurements by Contact and Non-contact Pachymetry Devices. J Curr Glaucoma Pract 2021;15(1):28-31.

EFFECT OF LUBRICANTS ON CORNEAL THICKNESS AFTER VITRECTOMY

PURPOSE

This study examines the impact of corneal surface lubricants used during pars plana vitrectomy on corneal edema.

METHODS

This prospective, observational, clinical study occurred at an academic institution. Participants were individuals aged 18 years and older who had already consented to undergo pars plana vitrectomy, without pre-existing corneal pathology. A corneal lubricant was chosen by the surgeon. Corneal thickness was measured preoperatively and postoperatively using pachymetry and anterior segment optical coherence tomography (AS-OCT). Main outcome measure was change in corneal thickness as measured by pachymetry.

RESULTS

Forty-one patients completed the study protocol. The 23 subjects in the SHCS group had a significantly smaller increase in corneal thickness as measured by pachymetry compared with the 18 subjects in the HPMC group (29.9 μm vs. 58.1 μm, P value 0.02). When measured by anterior segment optical coherence tomography, the SHCS group had a smaller increase in corneal thickness compared with the HPMC group (0.04 mm vs. 0.06 mm, P value 0.09) but did not reach significance.

CONCLUSION

SHCS is associated with reduced postoperative increase in corneal pachymetry as compared to HPMC.

Accuracy of Cirrus HD-OCT and Topcon SP-3000P for measuring central corneal thickness

PURPOSE

To compare and analyze the interchangeability of three measuring systems, each based on a different technique, for central corneal thickness (CCT) analysis.

METHODS

CCT measurements were measured using optical coherence tomography (OCT), non-contact specular microscopy (NCSM), and ultrasonic pachymetry (USP) in 60 eyes of 60 healthy patients with a mean age of 66.5±15.0 years and a mean spherical equivalent of 0.43±1.14 D. Analysis of variations in measurement concordance and correlation among the three different methods were performed. Comparison of CCT measurements were done using Bland-Altman plots (with bias and 95% confidence intervals), intraclass correlation coefficient (ICC), and paired t-student analysis.

RESULTS

Mean CCT values were: 549.20±26.91μm for USP (range 503-618μm), 514.20±27.49μm for NCSM (range 456-586μm) and 542.80±25.56μm for OCT (range 486-605μm). CCT values obtained with NCMS were significantly lower than those obtained with OCT and USP methods. NCMS CCT value was 36.08±10.72μm lower than USP value (p<0.05), and NCMS CCT value was 7.88±8.86μm lower than OCT value (p<0.05). ICC between USP-NCSM pair was 0.488 and 0.909 between USP-OCT pair.

CONCLUSION

OCT and UPS offered highly comparable results, whereas NCSM offered lower mean CCT values compared to the other two methods. Therefore, NCSM should not be considered a reliable method for measuring CCT and should rather be considered for assessing longitudinal changes in the same patient.

No differences in central corneal thickness between open-angle and pseudoexfoliation glaucoma patients

Introduction

Measurements of intraocular pressure (IOP) with Goldmann applanation tonometry are affected by central corneal thickness (CCT), as thinner corneas underestimate and thicker corneas overestimate the true IOP value. The literature is controversial regarding CCT values in patients with primary open-angle glaucoma (POAG) and exfoliation glaucoma (XFG). The aim of this study was to evaluate CCT in patients with XFG and POAG.

Methods

CCT was evaluated with optical coherence tomography (OCT). All participants who were previously diagnosed with either POAG or XFG underwent ophthalmological examinations. Contact lens users and patients with corneal diseases were excluded.

Results

Totally, 145 patients were enrolled in this study. The mean CCT was 535±30.4 µm in patients with POAG and was 536±33.7 µm in patients with XFG. The result was not statistically significant (P=0.98). The mean age for all participants was 73.8±7.7 years. The study included totally 61 women and 84 men. The two groups were similar in their demographic data, and mean deviation was the only parameter that differed statistically when comparing POAG with XFG (P=0.02).

Conclusion

Our data indicate that patients with XFG do not have thinner corneas than those with POAG, and therefore, CCT can not explain why they progress differently.

Accuracy of optical coherence tomography (OCT) in pachymetry for glaucoma patients

Background

Central corneal thickness (CCT) measurement has become an important test in the diagnosis and management of glaucoma. Currently, ultrasound corneal thickness measurement (pachymetry) is the most frequently used clinical technique and the gold standard to assess CCT. Newer instruments are currently available including the optical coherence tomography (OCT) instrument. The aim of the present study was therefore to evaluate the accuracy of the CCT measurements performed by three different observers, both with the OCT and ultrasound pachymetry (USP), in patients suffering from glaucoma.

Methods

Patients who had been previously diagnosed with glaucoma participated in this cross-sectional study. Glaucoma was defined as patients who had at least two repeatable Humphrey visual fields showing glaucoma damage using the software 24–2, and with the optic nerve showing typical glaucoma damage. The patients CCTs were measured with OCT and USP by three different examiners.

Results

Seventy eyes of 35 patients were included. The average age was 74 ± standard deviation (SD) 10.88, the average pachymetry value with OCT was 536 ± 29 μm, and the average pachymetry with USP was 532 ± 32 μm. The differences between OCT and USP were not significant (t-test, p = 0.32). The intraclass correlation coefficients were, for OCT, 0.99 [confidence interval (CI): 0.98–0.996], and for USP, 0.97 (CI: 0.95–0.98).

Conclusions

Agreement among the three observers using OCT or USP for pachymetry measurements was good. OCT might be used as an alternative method for pachymetry in glaucoma patients.

Central corneal thickness measurements in premature infants

AIM

To evaluate the central corneal thickness (CCT) measurements of premature infants.

METHODS

The premature infants who were born between 25-34wk of gestational age (GA) were retrieved for the study. All CCT measurements were performed within the first 2d of their life under topical anesthesia by using an ultrasonic pachymeter.

RESULTS

The mean CCT of 200 eyes was 647.79±63.94 µm. The mean CCT of the right and left eyes were similar (647.30±64.72 µm and 648.29±63.47 µm consecutively). The mean CCT of the girls was 642.08±54.89 µm and the boys was 653.07±71.14 µm, with no statistically significant difference (P>0.05). But there was a negative correlation of the CCT with GA and birth weight (BW) (P<0.01).

CONCLUSION

The CCT values of premature babies were negatively correlated with GA and BW.