Visual outcomes after three different surgical procedures for correction of refractive error in patients with thin corneas

How long does the recovery of corneal sensitivity in different corneal regions take after LASEK?

AIM

To determine the corneal sensitivity recovery period after laser-assisted sub-epithelial keratectomy (LASEK) refractive surgery and investigate the effects of ablation depth on it.

METHODS

In this study examinations were performed on 90 right eyes of 90 people (34 males and 56 females) with an age range of 20-35 and an average of 22.26±3.8 years old. A sensation of 5 corneal regions, including the center and 4 mid-peripheral regions, i.e., nasal, inferior, temporal, and superior, each at a distance of 2 mm from the center of the cornea were measured with a Cochet-Bonnet esthesiometer device in 3-time points including before LASEK, 1 and 3mo after the surgery, respectively. LASEK was performed on individuals with stabilized myopia of -1.00 to -7.00 diopters and astigmatism of less than 2.00 diopters. Furthermore, the individuals were divided into three groups regarding ablation depth.

RESULTS

The highest level of corneal sensitivity before surgery was related to the center of the cornea (59.1±7.76), and the highest level of corneal sensitivity loss was also related to this region. The sensation of all measured corneal regions significantly reduced 1mo postoperatively and returned to their preoperative levels 3mo after surgery (mean of 5 corneal regions in levels of preoperation: 58.2±6.48, 1mo postoperation: 57.3±5.84, 3mo postoperation: 58.2±5.49; P<0.05). A significant relationship was found between ablation depth and corneal sensitivity changes in the center and temporal regions (P<0.05).

CONCLUSION

Corneal sensitivity in myopia and low astigmatism decreases after LASEK and reaches the preoperative level within 3mo. The depth of ablation during surgery affected the recovery of corneal sensitivity.

Machine learning predicting myopic regression after corneal refractive surgery using preoperative data and fundus photography

PURPOSE

Myopic regression after surgery is the most common long-term complication of refractive surgery, but it is difficult to identify myopic regression without long-term observation. This study aimed to develop machine learning models to identify high-risk patients for refractive regression based on preoperative data and fundus photography.

METHODS

This retrospective study assigned subjects to the training (n = 1606 eyes) and validation (n = 403 eyes) datasets with chronological data splitting. Machine learning models with ResNet50 (for image analysis) and XGBoost (for integration of all variables and fundus photography) were developed based on subjects who underwent corneal refractive surgery. The primary outcome was the predictive performance for the presence of myopic regression at 4 years of follow-up examination postoperatively.

RESULTS

By integrating all factors and fundus photography, the final combined machine learning model showed good performance to predict myopic regression of more than 0.5 D (area under the receiver operating characteristic curve [ROC-AUC], 0.753; 95% confidence interval [CI], 0.710-0.793). The performance of the final model was better than the single ResNet50 model only using fundus photography (ROC-AUC, 0.673; 95% CI, 0.627-0.716). The top-five most important input features were fundus photography, preoperative anterior chamber depth, planned ablation thickness, age, and preoperative central corneal thickness.

CONCLUSION

Our machine learning algorithm provides an efficient strategy to identify high-risk patients with myopic regression without additional labor, cost, and time. Surgeons might benefit from preoperative risk assessment of myopic regression, patient counseling before surgery, and surgical option decisions.

Alternative Indications for Corneal Crosslinking

ABSTRACT

Corneal crosslinking (CXL) is the current mainstay treatment for progressive keratoconus. In the past 15 years, a variety of other indications have been tested. A systematic review was conducted to examine these alternative indications for CXL. In total, of 143 papers on crosslinking as a treatment for infectious keratitis, bullous keratopathy, pellucid marginal degeneration, post- laser in situ keratomileusis (LASIK) ectasia, and as a way to improve vision either on its own or in combination with other interventions were included. Post-LASIK ectasia is a definite indication for crosslinking. Surprisingly, only limited research has been performed on pellucid marginal degeneration, with no randomized trials available to date. Other interesting applications are the combined use of refractive lasers and crosslinking for suspicious or ectatic corneas and crosslinking as a standalone intervention for minor refractive errors. CXL might offer a solution for refractory bacterial keratitis. In bullous keratopathy, it seems to offer only a transient benefit.