The Distribution of Keratometry in a Population Based Study

The Significance of Dry Eye Signs on Preoperative Keratometry Measurements in Patients Scheduled for Cataract Surgery

Purpose

The primary objective was to investigate if subjects with dry eyes had increased variability of keratometry measurements prior to cataract surgery compared to subjects with non-dry eyes. Secondary objectives were to determine which separate signs affected keratometry.

Patients and Methods

This study was part of a prospective interventional randomized controlled trial. After dry eye diagnostics were performed (signs only) subjects were divided into sign of dry eye (SDE) positive and negative groups. To investigate variability, we performed two keratometry measurements for each subject with three different optical biometers: Anterion (OCT optical biometer), Eyestar (combined OCT and reflection-based optical biometer), and Lenstar (reflection based-optical biometer).

Results

One hundred and thirty-one subjects were available for analysis. The variability of astigmatism was significantly higher for subjects with hyperosmolarity compared to normal eyes for the Lenstar, as was the percentage of eyes with variability of astigmatism greater than 0.25 D. The percentage of eyes with variability of average K greater than 0.25 D was higher for subjects with non-invasive keratograph break-up time <10 seconds (NIKBUT positive) compared to normal eyes for the Lenstar.

Conclusion

Combined diagnostic criteria (signs only) showed no statistically significant differences for keratometry measurements between SDE positive and negative. Eyes with hyperosmolarity and NIKBUT positive showed statistically higher variability of keratometry measurements compared to normal eyes for Lenstar, but not for the Anterion or Eyestar biometers.

Distribution and Characteristics of Ocular Biometric Parameters among a Chinese Population: A Hospital-Based Study

INTRODUCTION

This study aimed to describe the distribution and characteristics of ocular biometric parameters among a large Chinese population.

METHODS

This retrospective cross-sectional study included 146,748 subjects whose ocular biometric parameters were measured at the ophthalmology clinic of West China Hospital, Sichuan University, and recorded in the hospital database. Ocular biometric parameters, including axial length, anterior chamber depth, corneal keratometry, and keratometric astigmatism, were recorded. Only monocular data for each subject were analyzed to avoid bias.

RESULTS

Valid data from 85,770 subjects (43,552 females and 42,218 males) aged 3-114 years were included in this study. The mean axial length, mean anterior chamber depth, average corneal keratometry, and mean keratometric astigmatism were 24.61 mm, 3.30 mm, 43.76 D, and 1.19 D, respectively. The stratification of the ocular parameters by age and gender showed significant inter-gender and inter-age differences.

CONCLUSIONS

Analysis of a large population of subjects in western China aged 3-114 years showed that the distribution and characteristics of ocular biometric parameters, including axial length, anterior chamber depth, corneal keratometry, and keratometric astigmatism, differed by age and gender. This study is the first to describe ocular biometric parameters in subjects aged > 100 years.

Swept-source OCT for corneal graft quantitative evaluation in the eye bank and the correlation of the measurements to pre-excision values

Quantitative evaluation of the human corneal grafts stored in the tissue banks is usually limited to endothelial cell density and central thickness. Swept-source OCT (SS-OCT) is capable of measuring the central curvatures of the corneal tissue prepared for transplantation without loss of sterileness, providing insights on its refractive state. The aim of the paper is to compare in vitro SS-OCT measurements with pre-excision values. Hand-held keratometry and ultrasound pachymetry was performed on 22 corneas before excision of corneoscleral button and insertion in the vial with Eusol-C solution (AlchimiaS.r.l, Nicolò, Italy). After 12 to 36 h of hypothermic storage the corneas were examined within the vials with custom built SS-OCT system maintaining a sterile environment. The anterior and posterior central curvatures, and central corneal thickness (CCT) were measured. Rotation of the corneoscleral button was controlled by making a 6-o'clock mark during excision. Mean pre-excision CCT was 626.45 ± 28.71 µm and 468.05 ± 52.96 µm when measured with SS OCT (r = 0.55; p < 0.001). Respective values for average keratometry were 7.74 ± 0.39 mm and 7.92 ± 0.57 mm (r = 0.6; p = 0.22). Although high differences were observed in corneal thickness, keratometric radius of curvature at the flat (r = 0.42; p < 0.001) and steep (r = 0.62; p = 0.014) meridian of the anterior corneal surface, as well as corneal anterior astigmatism (r = 0.3; p < 0.001), showed good correlation with pre-excision values. SS-OCT is capable of providing quantitative evaluation of the human corneal grafts in hypothermic storage. Good correlation between curvature measurements before excision and during banking in the vial indicates its clinical utility.