Ocular biomechanical measurements on post-keratoplasty corneas using a Scheimpflug-based noncontact device

The short-term effects of wearing swimming goggles on corneal biomechanics

PURPOSE

This study aimed to assess the impact of wearing swimming goggles (SG) on corneal biomechanics.

METHODS

Corneal deformation response, central corneal thickness (CCT), intraocular pressure (IOP) and biomechanically corrected intraocular pressure (bIOP) were measured with the Corvis system (Oculus Optikgeräte GmbH, Wetzlar, Germany) in thirty-one healthy young adults while wearing a drilled SG. All measurements were obtained before, at 30 s, 2 min, 3.5 min and 5 min of wearing SG, just after SG removal and after 2 min of SG removal.

RESULTS

The corneal biomechanics is sensitive to SG wear, observing lower corneal deformability during SG use. Specifically, wearing SG caused an increase in the time and length of the first applanation and radius curvature at the highest concavity, as well as a decrease and in the velocity of the first applanation and time and deformation amplitude of the second applanation (p < 0.001 in all cases). After SG removal, corneal biomechanical parameters showed a rebound-effect, obtaining a higher corneal deformability in comparison with baseline reading (p-corrected < 0.05 in all cases). Additionally, IOP and bIOP significantly increased while wearing SG (p < 0.001 in both cases), whereas CCT remained stable (p = 0.850).

CONCLUSIONS

Wearing SG modifies the biomechanical properties of the cornea, with reduced corneal deformability during SG wear. The outcomes of this study should be taken into consideration when making clinical decisions in subjects at high risk of developing corneal ectasias or glaucoma, as well as in the post-surgical management of these ocular conditions.

Factors predicting change in corneal astigmatism following suture removal in post-penetrating keratoplasty patients

Purpose

To identify factors predicting corneal astigmatic change following suture removal in post-penetrating keratoplasty patients.

Patients and methods

This cross-sectional study included the data of 33 events of corneal suture removal from 27 post-penetrating keratoplasty patients. Sutures were removed from the steep axis of transplanted cornea with 16 interrupted corneal sutures. Corneal astigmatism was measured before and after suture removal using ORBSCAN II. Patients' demographic data and corneal biomechanics parameters obtaining from the Corvis ST were recorded. The changes in corneal astigmatism were calculated using vector analysis. The correlation between changes in corneal astigmatism and the potential factors was evaluated using Spearman's correlation coefficient and linear regression model.

Results

The mean corneal astigmatism before and after suture removal was 7.1±3.7 diopters (D) and 5.5±3.2D, respectively. The mean astigmatic change was 7.0±6.3D (range, 0.3-30.8D) by vector analysis at 9.7±5.5 weeks after suture removal. Change in corneal astigmatism was significantly correlated with pre-suture removal astigmatism (Rs=0.47, P=0.01). There was no correlation between the donor-recipient trephine diameter difference, the duration from corneal transplantation to suture removal, the number of removed sutures with the change in corneal astigmatism, and corneal biomechanics parameters (P>0.05). Linear regression is given by the following equation: astigmatic change (D)=1.05x pre-suture removal astigmatism (D) - 0.43.

Conclusion

The astigmatic change after corneal suture removal in post-keratoplasty patients was significantly correlated with pre-suture removal astigmatism. These findings will permit a validated approach for reducing corneal astigmatism in post-keratoplasty patients.