Advances in the Technology of Corneal Cross-Linking for Keratoconus

Long-term changes in crystalline lens transparency after accelerated transepithelial corneal cross-linking in patients with keratoconus

PURPOSE

To investigate the long-term clinical outcomes and changes in crystalline lens transparency after accelerated (45 mW/cm2) transepithelial corneal cross-linking (ATE-CXL) using the Pentacam imaging system in patients with progressive keratoconus.

METHODS

The study prospectively included 44 keratoconus eyes of 40 patients (mean age: 24.39  ±  5.61 years) who underwent ATE-CXL. The examinations, including assessment of uncorrected distance visual acuity, corrected distance visual acuity, corneal topography, and corneal endothelial cell density count, were conducted preoperatively and 1 month, 3 months, 6 months, 1 year, and 5 years postoperatively. Measurement of crystalline lens density using Pentacam images was also performed pre- and postoperatively.

RESULTS

All surgeries were uneventful with no postoperative complications. All keratometry values and corneal thickness remained stable during the 5-year follow-up period (all p > 0.05). There were no significant differences in corneal endothelial cell density count, visual acuity, and anterior average lens density in the 0.5-, 1.0-, and 1.5-mm depth zones during the 5-year follow-up period compared with the preoperative values (all p > 0.05).

CONCLUSION

The results of this study suggest that ATE-CXL at 45 mW/cm2 is safe and effective for the treatment of progressive keratoconus in terms of both crystalline lens density and endothelial cell density.

Transepithelial accelerated corneal crosslinking for keratoconus eyes with maximum keratometry values larger than 58 diopters

PURPOSE

To evaluate the safety and efficacy of transepithelial accelerated corneal crosslinking (CXL) for advanced keratoconus eyes with maximum keratometry (Kmax) values >58 diopters (D).

SETTING

Department of Ophthalmology, Eye and ENT Hospital, Fudan University, Shanghai, China.

DESIGN

Prospective parallel control study.

METHODS

41 keratoconus eyes from 41 patients (mean age, 21.93 ± 5.48 years) who underwent transepithelial accelerated CXL were included prospectively. The enrolled eyes were divided into 2 groups according to their Kmax values (Group A, Kmax ≥58.0 D; Group B, Kmax <58.0 D). The examinations including assessment of uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal topography, and corneal endothelial cell density count were conducted preoperatively, at 1 day, 1 month, 3 months, 6 months, and 1 year postoperatively.

RESULTS

All 41 eyes finished 1 year follow-up. No statistical difference was noted between the mean UDVA and CDVA in both groups throughout the follow-up duration. At 1-year postoperative follow-up, the CDVA increased by ≥2 lines in 45% (9/20) and 28.6% (6/21) eyes in Groups A and B, respectively. The mean preoperative Kmax in Groups A and B were 62.51 ± 3.34 D and 49.98 ± 4.32 D, respectively, and that at postoperative 1-year follow-up were 61.94 ± 4.11 D and 50.24 ± 4.72 D, respectively. The Kmax values of 30% (6/20) eyes in Group A and 4.8% (1/21) eyes in Group B decreased by more than 1 D. Deduction of flat K, steep K, mean K, and Kmax showed no significant difference between the 2 groups at 1-year postoperative follow-up. Moreover, 20% (4/20) and 23.8% (5/21) of eyes in Groups A and B, respectively, showed progress at postoperative 1-year follow-up.

CONCLUSIONS

Transepithelial accelerated CXL can safely treat advanced keratoconus eyes with Kmax values ≥58.0 D with some extent of efficacy and has similar progressive rate as Kmax values <58.0 D.

Visual and Topographic Improvement with Epithelium-On, Oxygen-Supplemented, Customized Corneal Cross-Linking for Progressive Keratoconus

Customized cross-linking has been proposed as an alternative to conventional cross-linking in patients with progressive keratoconus, targeting greater flattening of the cone region and improved visual function. Epithelium-on cross-linking aims to reduce complications associated with epithelial removal, while the addition of oxygen aims to maintain treatment effect. Our study evaluates the combination of these novel treatment strategies to achieve a minimally invasive treatment targeting maximal functional outcomes. This prospective study included 42 eyes undergoing epithelium-on, accelerated, oxygen-supplemented, customized corneal cross-linking for progressive keratoconus. Outcome measures, including refraction, visual acuity, and corneal tomography were obtained at baseline and at 1, 3, and 6 months, and 1 year postoperatively. Logarithm of the minimum angle of resolution (logMAR) uncorrected visual acuity was significantly improved, from 0.87 ± 0.53 preoperatively, to 0.78 ± 0.56 1 year postoperatively (Wilcoxon rank sum test, p = 0.016). LogMAR best spectacle-corrected visual acuity was also significantly improved, from 0.19 ± 0.36 preoperatively, to 0.11 ± 0.33 postoperatively (p = 0.004). Manifest refractive cylinder was significantly decreased, from 4.50 ± 2.96 D preoperatively, to 3.27 ± 2.61 D postoperatively (p = 0.004). The baseline maximum keratometry (Kmax) was 53.04 ± 7.91 D, significantly flattening to 52.25 ± 7.31 D by 1 month, and remaining relatively stable at 1 year postoperatively (52.31 ± 7.50 D) (p < 0.001). No significant adverse events occurred in any eye. Epithelium-on, accelerated, oxygen-supplemented, customized corneal cross-linking is a promising new treatment approach, with reduced maximum keratometry, reduced astigmatism, and improved visual acuity at 1 year, with a favorable safety and patient comfort profile.

Efficacy of pulsed-light accelerated crosslinking in the treatment of progressive keratoconus: Two-year results

PURPOSE

The aim of this study was to evaluate the 2-year results of epithelium-off pulsed-light accelerated corneal collagen crosslinking treatment in progressive keratoconus using 30 mW/cm² ultraviolet A light for 6 min with a total dose of 5.4 J/cm².

METHODS

A total of 30 eyes of 22 patients with documented progressive keratoconus and treated with epithelium-off pulsed-light accelerated corneal collagen crosslinking using the KXL® crosslinking device (Avedro Inc, Waltham, MA, USA) were included in this retrospective study. Corneal tomographic measurements and best spectacle-corrected visual acuity were compared using analysis of variance with repeated measurements between the baseline visit (before the corneal collagen crosslinking treatment), and the sixth month, first, and second year visits.

RESULTS

Flat keratometry (K1), steep keratometry (K2), and mean keratometry (Km) decreased significantly at sixth month, first, and second years (p < 0.001, p = 0.001, and p < 0.001, respectively). Maximum keratometry (Kmax) decreased from 55.40 ± 4.90 D at baseline to 54.82 ± 4.68 D, 54.80 ± 5.12 D, and 54.65 ± 5.36 D at sixth month, first year, and second year, respectively (p = 0.007). The best spectacle-corrected visual acuity improved from 0.34 ± 0.24 logMAR at baseline to 0.25 ± 0.16 logMAR, 0.22 ± 0.15 logMAR, and 0.17 ± 0.13 logMAR at sixth month, first year, and second year, respectively (p < 0.001). At the second year visit, best spectacle-corrected visual acuity remained stable (no lines lost) with respect to the baseline in 8 eyes and increased 1 or more lines in 22 eyes.

CONCLUSION

Pulsed-light accelerated corneal collagen crosslinking using 30 mW/cm² ultraviolet A light for 6 min with a total dose of 5.4 J/cm² is an effective treatment modality in cases with progressive keratoconus-it stops progression at 2 years also regresses some of the cases.

Corneal Stiffening by a Bacteriochlorophyll Derivative With Dextran and Near-Infrared Light: Effect of Shortening Irradiation Time up to 1 Minute

PURPOSE

The aim of this study is to determine the effect of variation of the exposure time of near-infrared irradiation on corneal stiffening after a bacteriochlorophyll derivative (WST11) with dextran (WST-D) application.

METHODS

One hundred four paired eyes of 3-month-old New Zealand White rabbits were included in this study. Fifty-two eyes (ex vivo n = 34, in vivo n = 18) were mechanically deepithelialized, treated topically with WST-D, and irradiated at 10 mW/cm using a diode laser at 755 nm for 1, 5, or 30 minutes. Untreated fellow eyes served as controls. Corneoscleral rings were removed immediately after treatment (ex vivo), or 1 month after treatment (in vivo). Corneal strips were cut and underwent biomechanical stress-strain measurements.

RESULTS

Ex vivo, the mean tangent elastic modulus was significantly higher in the treatment groups than in the control groups for 1, 5, and 30 minutes of irradiation, respectively, 6.06 MPa, 95% confidence interval (CI, 4.5-7.6) versus 14.02 MPa, 95% CI (10.2-17.8), n = 11, 4.8 MPa, 95% CI (3.9-5.7) versus 15.03 MPa, 95% CI (12-18.1), n = 11, and 7.8 MPa, 95% CI (5.6-10.02) versus 16.2 MPa, 95% CI (13.6-18.9), n = 11; P < 0.001 for all comparisons. In vivo, the mean elastic moduli in the treatment groups were significantly higher for 5 and 30 minutes of irradiation but not for 1 minute of irradiation, respectively, 11.4 MPa, 95% CI (8.5-14.2), versus 17.1 MPa, 95% CI (14.5-19.7), n = 5; P < 0.001, and 9.4 MPa, 95% CI (5.1-13.8) versus 16 MPa, 95% CI (13.1-19), n = 5; P < 0.01, and 11.3 MPa, 95% CI (6-16.6) versus 12.2 MPa, 95% CI (7.5-16.8), n = 5; P = 0.7.

CONCLUSIONS

WST-D/near-infrared treatment using shortened irradiation time (1 minute ex vivo and 5 minutes in vivo) results in significant corneal stiffening, and this might provide an alternative to the currently applied riboflavin/ultraviolet A cross-linking.

Lasik Xtra® Provides Corneal Stability and Improved Outcomes

A new procedure which combines LASIK and corneal cross-linking (Lasik Xtra®) has been proposed as an alternative to traditional LASIK. It is aimed at restoring strength to the cornea, increasing stability in visual outcomes, increasing the accuracy of the refractive correction, and potentially lowering enhancement rates. This article reviews the current clinical evidence which has been published on the topic and reviews both the safety and efficacy argument for the procedure.