Prospective two year study of changes in corneal density following transepithelial pulsed, epithelium-off continuous and epithelium-off pulsed, corneal crosslinking for keratoconus

Corneal Crosslinking: Present and Future

Keratoconus is a progressive corneal thinning disorder that can lead to vision loss. In the last 2 decades, corneal crosslinking (CXL) has emerged as an effective method to halt the progression of keratoconus and reduce the number of patients requiring keratoplasty. The procedure has been adopted globally and has evolved to become a part of combination treatments to regularize the cornea and improve visual outcomes. CXL has even been extrapolated in managing other ocular pathologies such as progressive myopia, infectious keratitis, and bullous keratopathy. This review aims to summarize the current role of CXL in keratoconus and its alternative uses, and provide insights into future developments in this fast-developing field.

Corneal epithelial remodeling after femtosecond laser-assisted in situ keratomileusis combined with intraoperative accelerated corneal collagen crosslinking for myopia: a retrospective study

Background

This study analyzed regional corneal thickness remodeling, biomechanical properties, and visual outcomes after femtosecond laser-assisted in situ keratomileusis combined with intraoperative accelerated corneal collagen crosslinking (LASIK Xtra) for myopia.

Methods

This retrospective study analyzed 21 consecutive patients (18 women, three men; 42 eyes) who were treated with LASIK Xtra. All treatments were performed with ultraviolet-A (energy, 2.7 J/cm2; irradiance, 30 mW/cm2), using continuous (90 s) illumination. Postoperative values of corneal biometrics and visual outcomes were compared with preoperative values. Corneal thickness changes were evaluated using anterior segment optical coherence tomography. All patients were followed up for 12-month postoperatively. Preoperative and postoperative data were compared statistically using the paired t-test for normally distributed parameters and the Wilcoxon rank-sum test and Friedman analysis of variance with Bonferroni correction for non-normally distributed data.

Results

Uncorrected distance visual acuity (UDVA) significantly improved at 6-month after surgery (P < 0.001). The central and inner regional corneal epithelial thickness significantly increased after LASIK Xtra (P < 0.05 for all), while the peripheral corneal epithelial thickness remained stable at 12-month after surgery. There was also a statistically significant decreased in the stromal thickness at most locations (P < 0.05 for all), except in the outer superior and outer superior-temporal regions.

Conclusions

LASIK Xtra provided improvement in UDVA, corneal curvature, and corneal biomechanical stability. Because the results of this retrospective study results depended on the cohort members’ past information, it was inferred and confirmed that regular corneal thickness remodeling occurred after treatment.

Flattening of Central, Paracentral, and Peripheral Cones After Non-accelerated and Accelerated Epithelium-off CXL in Keratoconus: A Multicenter Study

PURPOSE

To assess the flattening of central, paracentral, and peripheral cones following non-accelerated (non-A-CXL) and accelerated (A-CXL) epithelium-off corneal cross-linking with 10 times higher intensity.

METHODS

In this multicenter study of 200 eyes (100 in each group), following 10 minutes of soak time with riboflavin 0.1%, continuous CXL was performed for 30 minutes (intensity: 3 mW/cm², fluence: 5.4 J/cm²) in the non-A-CXL group and 3 minutes (intensity: 30 mW/cm², fluence: 5.4 J/cm²) in the A-CXL group. Anterior and posterior cone flattening were compared at 12 months. Multiple regression analysis was performed to establish correlation of age, sex, cone location, and preoperative maximum keratometry (Kmax) values with postoperative flattening at 12 months.

RESULTS

In the non-A-CXL and A-CXL groups, central cones were the steepest, followed by paracentral and peripheral cones. Both groups showed significant flattening in central (1.54 ± 1.94 and 1.09 ± 1.79 diopters [D]) and paracentral (0.62 ± 1.59 and 0.55 ± 0.98 D) cones only. In the non-A-CXL group, there was a positive correlation between postoperative flattening and preoperative Kmax values, whereas paracentral and peripheral cone locations were negatively related. In the A-CXL group, only paracentral location was negatively correlated to postoperative flattening and showed posterior cone steepening at 12 months.

CONCLUSIONS

Although central cones were the steepest in both groups, there was no difference in postoperative flattening between the groups for all cone locations. In the non-A-CXL group, postoperative flattening was proportional to preoperative Kmax values in central cones and was less with paracentral and peripheral locations. With A-CXL, postoperative flattening was less only with paracentral location. In the A-CXL group, significant posterior cone steepening was noticed only in paracentral cones. [J Refract Surg. 2022;38(5):310-316.].

The Aotearoa Research Into Keratoconus Study: Geographic Distribution, Demographics, and Clinical Characteristics of Keratoconus in New Zealand

PURPOSE

To investigate the epidemiologic, demographic, and basic clinical characteristics of individuals with keratoconus managed by optometrists in New Zealand (NZ)/Aotearoa.

METHODS

A prospective, longitudinal, nationwide, survey protocol was completed for every patient with keratoconus who underwent a consultation with participating optometrists in a 2-year period. Data for each patient included date of birth, sex, self-reported ethnicity, new or previous diagnosis, uncorrected (UCVA) and best-corrected visual acuity (BCVA), type of refractive correction required to obtain BCVA and keratometric readings obtained using keratometry or computerized topography.

RESULTS

One thousand eight hundred sixty-nine cases were identified, with a mean age of 41.0 ± 15.7 years, 56.4% being men, and 87.3% with previous diagnosis. The distribution of cases was skewed toward Auckland (41.6%), Waikato (21.3%), Wellington (16.8%), and Bay of Plenty (13.3%). Self-reported ethnicities were predominantly NZ European (54.4%), Māori (24.7%), and Pacific Peoples (15.5%), disproportionate to the general population profile (74.0%, 14.9%, and 7.4% respectively). Most eyes (64.3%) were managed with rigid contact lenses (corneal lens in 34.2%). The mean K-mean was 49.0 ± 5.7 D. The mean UCVA was 6/42 and BCVA was 6/9. Māori and Pacific Peoples had both the highest K-mean and proportions of eyes graded stage IV on the Amsler-Krumeich scale.

CONCLUSIONS

The results indicate that keratoconus is relatively common in NZ with at least 1869 patients managed by optometrists in 2 years. Most eyes had mild to moderate disease; however, Māori and Pacific Peoples seem to have greater disease severity. An ethnic predilection is apparent, with Māori and Pacific Peoples overrepresented relative to their population proportions, reinforcing a long-held clinical suspicion.

Update on corneal collagen crosslinking for ectasia

PURPOSE OF REVIEW

Corneal collagen crosslinking (CXL) is a minimally invasive treatment that can stabilize corneal ectatic disorders including keratoconus, pellucid marginal degeneration, or postrefractive surgery ectasia. The benefits of CXL have been well documented. New research is focused on modifying current treatment protocols with the goals of maximizing corneal stability while also shortening overall procedure time.

RECENT FINDINGS

Accelerated CXL protocols have the goal of delivering the same ultraviolet A intensity as conventional protocols, but over a shorter time period. Accelerated protocols have shown success to date, but there are concerns for long-term corneal stability. Pulsed protocols may increase the long-term efficacy of the accelerated designs. In addition, transepithelial crosslinking protocols have been designed with the goal of reducing postoperative pain and lower the risk of infectious complications of epithelial-off conventional protocols.

SUMMARY

Newer CXL protocols attempt to make the procedure safer and more effective. Current research is promising, but long-term studies are essential to understand how the new protocols may affect corneal stability.

Accelerated Epithelium-off Corneal Cross-linking With High Ultraviolet Energy Dose (7.2 J/cm2) for Progressive Keratoconus: 2-Year Results in a Chinese Population

PURPOSE

To evaluate the results of epithelium-off continuous light accelerated corneal cross-linking (CXL) with a total dose of 7.2 J/cm² for treating progressive keratoconus in a Chinese population during 24 months of follow-up.

METHODS

In this retrospective, interventional case series, 45 eyes of 31 consecutive patients with progressive keratoconus were evaluated. All patients underwent accelerated CXL with settings of 30 mW/cm² for 4 minutes, corresponding to a total dose of 7.2 J/cm². Visual acuity, manifest refraction, epithelial thickness, topography, tomography, aberrometry, endothelial cell count, and intraocular pressure were evaluated at baseline and at 1, 3, 6, 12, 18, and 24 months postoperatively.

RESULTS

Progressive keratoconus was stabilized in 91.11% and 93.33% of the patients at 12 and 24 months, respectively. The improvement in corrected distance visual acuity was significant throughout the postoperative follow-up period (P < .05), excluding month 1. A significant decrease in the maximum keratometric values (0.67 ± 1.68, 0.92 ± 1.78, and 0.97 ± 1.73 D) was observed at months 12, 18, and 24, respectively (P < .05 for all). Corneal irregularity improved, particularly total root mean square and higher order aberrations at 12 to 24 months after CXL. In bilateral CXL, the progression of the first eye was highly predictive of the outcome of the second eye.

CONCLUSIONS

CXL with a total dose of 7.2 J/cm² maintains long-term results in halting the progression of keratoconus, with significant improvement in the corrected distance visual acuity and stability of keratometric values. Further clinical studies with longer follow-up periods and larger samples are necessary to confirm these results. [J Refract Surg. 2020;36(11):731-739.].