Measurement of central corneal thickness using Orbscan 3, Pentacam HR and ultrasound pachymetry in normal eyes

The effect of pterygium on front and back corneal astigmatism and aberrations in natural-light and low-light conditions

BACKGROUND

To investigate the effect of different sizes of pterygium on the front and back corneal topography, refractive changes and aberrations in natural-light and low-light conditions.

METHODS

Sixty subjects with unilateral primary nasal pterygium were enrolled in this study. All the patients' uncorrected, best spectacle-corrected visual acuity, corneal topographic aberration data in 3 mm and 7 mm areas were collected. The pterygium size was evaluated by the slit-lamp photography and Sirius Scheimpflug Analyzer.

RESULTS

The front topographic astigmatism values, corneal total aberrations, and higher-order aberrations in 3 mm and 7 mm areas were higher in the pterygium group than those in the control group. The pterygium horizontal length and thickness were moderately to strongly correlated with astigmatism and RMS of aberrations, while pterygium vertical length showed no or just mild correlation with the corneal astigmatism and aberrations. Compared to the readings in 3 mm area, the front and back corneal astigmatism and aberrations were larger in 7 mm area.

CONCLUSIONS

Pterygium led to visual impairment by inducing astigmatism and aberrations. In low-light condition, the visual function worsened due to increased corneal astigmatism values and aberrations.

Investigation of the Sectorized Corneal Thickness of Eyes With Corneal Endothelial Dysfunction Using Anterior-Segment Optical Coherence Tomography

PURPOSE

The aim of this study was to investigate the sectorized corneal thickness of eyes with corneal endothelial dysfunction using anterior-segment optical coherence tomography.

METHODS

We retrospectively collected anterior-segment optical coherence tomography data conducted before endothelial keratoplasty on 53 eyes of 53 patients with corneal endothelial dysfunctions including Fuchs endothelial corneal dystrophy, bullous keratopathy (BK) after trabeculectomy, and BK after laser iridotomy and from 18 normal eyes of 18 subjects. The imaging points were divided into 17 sectors. The mean for each sector was calculated and compared with the corresponding superior/inferior and temporal/nasal sectors.

RESULTS

In the normal eyes, the superior sectors were thicker than the inferior and the temporal sectors thinner than the nasal. In the diseased eyes, the superior sectors were thicker than the inferior in all subgroups; however, this tendency was no longer observed after the values were divided by the mean for the normal eyes. No significant differences were found on horizontal comparisons; however, after the values were divided by the mean for the normal eyes, the temporal sectors were thicker than the nasal. When comparing the values between the with-hole and the without-hole sides in the BK after laser iridotomy eyes, the sectors on the with-hole side were thicker than the other side.

CONCLUSIONS

Corneal thickness of endothelial dysfunction was thicker in the superior sectors than the inferior but at a similar level to normal eyes. No significant differences were found for horizontal comparisons but, based on comparison with the normal eyes, the temporal sectors were thicker than the nasal.

Agreement of anterior segment measurements between four diagnostic imaging devices in myopic patients

PURPOSE

To compare the inter-device agreement of anterior chamber depth (ACD), central corneal thickness (CCT), flat keratometry (K1), steep keratometry (K2), corneal astigmatism (ΔK), and white-to-white (WTW) measurements.

METHODS

This is a retrospective study with 73 myopic patients (142 eyes). We extracted and compared anterior segment measurements (ACD, CCT, K1, K2, ΔK, and WTW) of four devices (OPD-Scan III, Pentacam HR, Lenstar LS 900, and Galilei G4), and performed pairwise agreement comparisons between them.

RESULTS

Agreement analyses revealed that the most agreement occurred: in Pentacam HR and Galilei G4 for ACD measurements, in Pentacam HR and Lenstar LS 900 for CCT measurements, in OPD-Scan III and Galilei G4 for WTW measurements, in OPD-Scan III and Pentacam HR for K1 and K2 measurements, and OPD-Scan III and Galilei G4 for ΔK measurements.

CONCLUSION

OPD-Scan III is interchangeable with both Galilei G4 and Lenstar LS 900 for WTW measurements. OPD-Scan III and the Pentacam-HR are interchangeable in K1, K2, and ΔK measurements. OPD-Scan III and Lenstar LS 900, and OPD-Scan III and Galilei G4 are interchangeable in K1 and ΔK measurements, respectively.

Sirius Scheimpflug-Placido versus ultrasound pachymetry for central corneal thickness: meta-analysis

Background

To compare the difference in central corneal thickness (CCT) measurements in normal eyes between a rotating Scheimpflug camera combined with a Placido-disk corneal topographer (Sirius, CSO, Italy) and ultrasound pachymetry (USP).

Methods

A systematic literature search was conducted for relevant studies published on PubMed, Medline, EMBASE, and the Cochrane Library and ClinicalTrials.gov from inception to August 1st, 2019. Primary outcome measures were CCT measurements between Sirius and USP. A random effects model was used to pool CCT measurements.

Results

A total of twelve studies involving 862 eyes were included in this meta-analysis. The meta-analysis found CCT measurements between Sirius and USP to be statistically significantly different (P < 0.0001). The mean difference between Sirius and USP was −11.26 μm with a 95% confidence interval (CI) (−16.92 μm, −5.60 μm). The heterogeneity was I² = 60% (P = 0.004).

Conclusion

CCT measurements with the Sirius Scheimpflug-Placido topographer were statistically significantly lower than USP. However, it may be argued that the mean difference of 11.26 μm is not a clinically significant difference.