Clinical and Morphological in Vivo Confocal Microscopy Findings following a Modified Biphasic Higher Fluence Transepithelial Corneal Crosslinking

Purpose: To compare the refractive efficacy and morphological changes in the cornea following a novel biphasic higher fluence transepithelial corneal crosslinking (BI-TE-CXL) and transepithelial corneal crosslinking (TE-CXL) in adults keratoconus.Methods: Patients with progressive keratoconus who required corneal crosslinking were assigned to the BI-TE-CXL group (32 eyes, phase 1: 7.2 J/cm2 for 5 min and 20 s of pulsed-light exposure, KXL, Glaukos-Avedro; phase 2: 3.6 J/cm2 for 6 min and 40 s of continuous light exposure at the front curvature apex with a 6 mm diameter light spot, UVX-2000, IROC) or the TE-CXL group (32 eyes, uniform 7.2 J/cm2 for 5 min and 20 s of pulsed-light exposure, KXL, Glaukos-Avedro). Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), corneal fluorescein staining (CFS), corneal topography, anterior segment optical coherence tomography (AS-OCT), and in vivo corneal confocal microscopy (IVCM) were performed 3, 6, 12 and 24 months after surgery.Results: The CFS scores in the BI-TE-CXL group were significantly higher than those in the TE-CXL group on the first two days after surgery (p < 0.001). The Kmax (at 12 and 24 months) and CDVA (logMAR) were significantly lower in the BI-TE-CXL group than those in the TE-CXL group (p < 0.05). The corneal demarcation line under AS-OCT was visible in 81.3% of patients in the BI-TE-CXL group and 15.6% in the TE-CXL group. The depth of the demarcation line under IVCM was significantly deeper in the BI-TE-CXL group (248.3 ± 25.0 μm) than that of the TE-CXL group (136.5 ± 15.6 μm) in the central cornea (p < 0.001). The cross-linked collagen structures in the central cornea were still present after 12 months in the BI-TE-CXL group. No significant difference in sub-basal nerve density between the two groups (p > 0.05).Conclusions: Following BI-TE-CXL, CDVA was significantly improved, accompanied by deeper demarcation line depth and persistent crosslinked structures in the central corneal stroma.

Long-term outcomes of tailored stromal expansion with refractive lenticule for crosslinking thin corneas

PURPOSE

To assess the long-term safety and stability of visual outcomes following the modified technique of collagen crosslinking (CXL) using refractive lenticule in eyes with thin corneas (<400 µm) and progressive keratoconus.

SETTING

A tertiary eye care hospital in India.

DESIGN

Prospective, interventional case series.

METHODS

Eyes with progressive keratoconus and thin corneas (<400 µm) underwent CXL with intraoperative stromal augmentation using a refractive lenticule obtained from small-incision lenticule extraction (SMILE). Preoperative and postoperative evaluation (3 months, and then yearly thereafter) included corneal tomography (Oculus Pentacam), uncorrected and corrected distance visual acuity (UDVA and CDVA, respectively), manifest refraction, and endothelial cell count (specular microscopy), and adverse events, if any, were noted. The patients were followed up for a period of 5 years.

RESULTS

Seven eyes were included in the analysis. Mean corneal flattening of -4.29 D was noted from preoperative maximum keratometry (P = 0.018). An improvement in UDVA and CDVA of 0.38 logarithm of minimum angle of resolution (logMAR) and 0.36 logMAR, respectively, was noted at 5 years postoperative visit. Four eyes demonstrated a gain of two lines in CDVA. Mean spherical equivalent improved from -6.85 D preoperatively to -6.05 D at 5 years postoperatively. Clear demarcation line was noted between 230 to 270 µm on anterior segment optical coherence topography. No significant endothelial cell loss was noted postoperatively.

CONCLUSION

Long-term outcomes demonstrated safety and disease stability following lenticule-assisted CXL.

Customized corneal allogenic intrastromal ring segments (CAIRS) for keratoconus with decentered asymmetric cone

Corneal allogenic intrastromal ring segments (CAIRS) refer to the intracorneal placement of fresh, unprocessed, processed, preserved, or packaged allogenic rings/segments of any type/length. We described uniform-thickness CAIRS previously. We now describe a new technique of customized CAIRS to personalize the flattening effect as per individual topography. A prospective interventional case series of patients with pericentral/ paracentral decentered cones and gradation of keratometry with one side steeper than the other was conducted. Individually customized tapered CAIRS with variable volume, arc length, taper length, and gradient of taper were implanted. In total, 32 eyes of 29 patients with at least 1-year follow-up were included. Special double-bladed trephines and a CAIRS customizer template allowed the creation of individually customized CAIRS. Mean uncorrected distance visual acuity (UDVA) and spectacle-corrected distance visual acuity improved from 0.22 to 0.47 (P = 0.000) and from 0.76 to 0.89 (P = 0.001), respectively. Significant improvement was seen in K1, K2, Km, Kmax, topographic astigmatism, Q-value, sphere, cylinder, spherical equivalent, Root Mean Square (RMS), Higher Order Aberrations (HOA), and vertical coma (P < 0.01, 0.05). There was no significant change in the width or height of CAIRS between 1 month and last visit on anterior-segment optical coherence tomography. Five eyes continued to remain at the same UDVA, 27 eyes had at least 2 lines, and 13 eyes had at least 3 or more lines improvement in UDVA. The maximum improvement in UDVA was 7 lines. A significant difference in flattening was obtained at different zones across the tapered CAIRS. Thus, differential flattening was achieved across the cone based on the customization plan. Personalized customization was possible for each cornea, unlike limited models of progressive-thickness synthetic segments. Allogenic nature, greater customizability, efficacy, and absent need for large inventories are advantages compared to synthetic segments.

Recent advances in medicinal compounds related to corneal crosslinking

Corneal crosslinking (CXL) is the recognized technique to strengthen corneal collagen fibers through photodynamic reaction, aiming to halt progressive and irregular changes in corneal shape. CXL has greatly changed the treatment for keratoconus (KCN) since it was introduced in the late 1990's. Numerous improvements of CXL have been made during its developing course of more than 20 years. CXL involves quite a lot of materials, including crosslinking agents, enhancers, and supplements. A general summary of existing common crosslinking agents, enhancers, and supplements helps give a more comprehensive picture of CXL. Either innovative use of existing materials or research and development of new materials will further improve the safety, effectiveness, stability, and general applicability of CXL, and finally benefit the patients.

Keratoconus: A historical and prospective review

This article is a historical and prospective review of keratoconus and ectatic corneal diseases. It covers definitions and terminology, the prevalence of keratoconus, predisposing factors, diagnosis, differential diagnosis, management, classifications, and progression criteria. It highlights other aspects of the disease that are usually over-missed, including the psychological, social, and economic impact. This review presents the information chronically in terms of the first author. It concludes by possessing the challenges and difficulties that are still to be overcome and suggests a plan.

Short-Term Effect of Conventional Versus Accelerated Corneal Cross-Linking Protocol on Corneal Geography and Stability

Purpose: To determine the 6-month effect of conventional (CXL30) and accelerated cross-linking with a UVA intensity of 9 mW/cm² (CXL10) on corneal stability and to investigate whether there was a difference in ABCD grading system parameters regarding the two different procedures. Methods: Twenty-eight eyes of 28 patients with a documented keratoconus (KN) progression were included. Patients were selected to undergo either epi off CXL30 or CXL10. At the baseline and the follow-up visits after one (V1), three (V2), and six months (V3), the patients underwent complete ophthalmic examination and corneal tomography. Results: In the CXL30 group, all the parameters from the ABCD grading system significantly changed from baseline to V3; parameter A decreased (p = 0.048), B and C increased (p = 0.010, p < 0.001), and D decreased (p < 0.001). In the CXL10 group, there were no changes in parameters A (p = 0.247) and B (p = 0.933), though parameter C increased (p = 0.001) and D decreased (p < 0.001). After an initial decline after one month, visual acuity (VA) recovered on V2 and V3 (p < 0.001), and median maximal keratometry (Kmax) decreased in both groups (p = 0.001, p = 0.035). In the CXL30 group, there were significant changes in other parameters; average pachymetric progression index (p < 0.001), Ambrósio relational thickness maximum (ARTmax) (p = 0.008), front and back mean keratometry (p < 0.001), pachymetry apex (PA) (p < 0.001), and front elevation (p = 0.042). However, in the CXL10 group, there were significant changes only in ARTmax (p = 0.019) and PA (p < 0.001). Conclusion: Both epi-off CXL protocols showed similar short-term efficacy in improving VA and Kmax, halting the progression of KN, and both similarly changed tomographic parameters. However, the conventional protocol modified the cornea more significantly.

Current clinical practice in corneal crosslinking for treatment of progressive keratoconus in four Nordic countries

PURPOSE

To evaluate clinical practice in the diagnosis and treatment of progressive keratoconus with corneal crosslinking (CXL) in four Nordic countries.

METHODS

A questionnaire was sent to all centres at which keratoconus patients are evaluated and CXL is performed in Sweden, Denmark, Norway and Iceland. Nineteen of 20 centres participated.

RESULTS

CXL is performed approximately 1300 times per year in these four Nordic countries with a population of around 21.7 million (2019). In most cases, progression is evaluated using the Pentacam HR, and the maximum keratometry reading (K_max ) is considered the most important parameter. The most frequently used treatment protocol in Scandinavia is the 9 mW/cm² epi-off protocol, using hydroxylpropyl methylcellulose riboflavin (HPMC-riboflavin). The participants deemed the following areas to be in most need of improvement: adaptation of the CXL protocol to individual patients (5/19), the development of effective epi-on treatment protocols (4/19), optimal performance of CXL in thin corneas (4/19), improvement of the definition of progression (2/19), and diagnosis of the need for re-treatment (2/19).

CONCLUSIONS

We concluded that the diagnosis of progressive keratoconus and the diagnostic equipment used are similar. Treatment strategies are also similar but are suitably different to provide an interesting basis for the comparison of treatment outcomes. The high degree of participation in this survey indicates the possibility of future scientific collaboration on CXL focusing on the areas deemed to need improvement. It would also be of interest to evaluate the possibility of creating a Nordic CXL Registry. The high number of CXL treatments performed ensures sufficient statistical power to solve many questions. Such a registry could be an important contribution to evidence-based care and would allow for longitudinal evaluation.

Clinical Ocular Biomechanics: Where Are We after 20 Years of Progress?

Purpose: Ocular biomechanics is an assessment of the response of the structures of the eye to forces that may lead to disease development and progression, or influence the response to surgical intervention. The goals of this review are (1) to introduce basic biomechanical principles and terminology, (2) to provide perspective on the progress made in the clinical study and assessment of ocular biomechanics, and (3) to highlight critical studies conducted in keratoconus, laser refractive surgery, and glaucoma in order to aid interpretation of biomechanical parameters in the laboratory and in the clinic.Methods: A literature review was first conducted of basic biomechanical studies related to ocular tissue. The subsequent review of ocular biomechanical studies was limited to those focusing on keratoconus, laser refractive surgery, or glaucoma using the only two commercially available devices that allow rapid assessment of biomechanical response in the clinic.Results: Foundational studies on ocular biomechanics used a combination of computer modeling and destructive forces on ex-vivo tissues. The knowledge gained from these studies could not be directly translated to clinical research and practice until the introduction of non-contact tonometers that quantified the deformation response of the cornea to an air puff, which represents a non-destructive, clinically appropriate load. The corneal response includes a contribution from the sclera which may limit corneal deformation. Two commercial devices are available, the Ocular Response Analyzer which produces viscoelastic parameters with a customized load for each eye, and the Corvis ST which produces elastic parameters with a consistent load for every eye. Neither device produces the classic biomechanical properties reported in basic studies, but rather biomechanical deformation response parameters which require careful interpretation.Conclusions: Research using clinical tools has enriched our understanding of how ocular disease alters ocular biomechanics, as well as how ocular biomechanics may influence the pathophysiology of ocular disease and response to surgical intervention.

Subjective and objective evaluation of corneal haze after accelerated corneal crosslinking for corneal ectasias

PURPOSE

To evaluate the relationship between subjective (slit lamp examination [SLE]) and objective (densitometry) measurements of corneal haze after accelerated corneal crosslinking (aCXL), assess the relationship between densitometry and corrected distance visual acuity (CDVA), and determine the effect of baseline characteristics on densitometry after aCXL in eyes with progressive keratoconus and other ectasias.

SETTING

Kensington Eye Institute and Bochner Eye Institute, Toronto, Canada.

DESIGN

Retrospective analysis of a prospective interventional cohort study.

METHODS

Scheimpflug-derived corneal densitometry, CDVA, maximum keratometry (K_max ), and central corneal thickness were measured preoperatively and up to 1 year after aCXL, and post-operative haze was estimated with SLE (n = 483 eyes). A random effect model was used to examine the relationship between post-operative subjective haze with SLE and densitometry. Linear mixed models were used to examine the relationship between densitometry, pre-operative baseline characteristics, and CDVA.

RESULTS

There was a significant association between subjective haze with SLE and densitometry (p < 0.001). There was a significant relationship between CDVA and densitometry: for every 10 GSUs of increased densitometry in the 0-2 mm zone, CDVA worsened by approximately half a Snellen line (p < 0.001). Age and pre-operative K_max were significant predictors of densitometry. For every 10 years of age, densitometry increased by 0.68 GSUs (95% CI [0.27 to 1.07], p < 0.001). For every 10 D of increased preoperative K_max , densitometry increased by 0.69 GSUs (95% CI [0.41 to 0.98], p < 0.001).

CONCLUSIONS

Subjective haze after aCXL estimated with SLE, is significantly associated with densitometry. Increased densitometry after aCXL is associated with a reduction in CDVA.

Assessment of Efficacy of a Novel Crosslinking Protocol with Intracameral Oxygen (Bubble-CXL) in Increasing the Corneal Stiffness Using Atomic Force Microscopy

The environmental oxygen level plays a critical role in corneal crosslinking (CXL), a treatment method to increase corneal biomechanical stability. In this study, we introduce a new CXL method (Bubble-CXL), in which intracameral oxygen serves as an additional oxygen source during eye treatment. The efficiency of this new method was compared with the efficiency of the standard CXL method. Three fresh porcine eye pairs were included in this study. One eye of each pair was treated with standard CXL, whereas in the partner eye, intracameral oxygen was injected prior to CXL and removed at the end of the procedure. The Young's modulus of each cornea was measured using atomic force microscopy. All analyzed corneas treated with intracameral oxygen showed significantly higher Young's modulus and thus an increased stiffness compared to the cornea of the partner eye treated with the standard protocol. Using intracameral oxygen in CXL therapy may increase crosslinking efficiency and improve biomechanical corneal properties.

Improving keratoconus management with central cor neal regularization and corneal collagen cross-linking protocol treatment

PURPOSE

To evaluate safety and efficacy of customized central corneal regularization (CCR), together with simultaneous accelerated corneal collagen cross-linking (A-CXL) - CCR-CXL protocol, to treat keratoconus-related corneal ectasia.

DESIGN

Retrospective, comparative observational case series.

METHODS

Patients that had undergone combined CCR-CXL protocol. Main inclusion criteria were keratoconus visual acuity deterioration and contact lens intolerance. All patients underwent complete ophthalmological evaluation, corrected distance visual acuity (CDVA) and Scheimpflug-corneal tomography. Central corneal regularization was performed by ablation using flying spot laser. Subsequently, the stroma was saturated with 0.17% riboflavin-5-phosphate added every 2 minutes, followed by A-CXL 9 mW/cm2 for 10 minutes. CDVA, medium keratometry value (Kmed), and total corneal morphological irregularity index (CMI) of patients were analyzed before surgery and after 1, 3 and 12 months. A P value of .05 or less was considered statistically significant.

RESULTS

46 eyes of 39 keratoconus patients were treated. At 1 month, the mean CDVA (LogMar) increased from 0.19 ± 0.02 to 0.12 ± 0.02 (P < .05), and the difference remained stable at month 12. Kmax decrease was statistically significant from 57.02 ± 5.65 to 50.21 ± 4.48 (P < .05). CMI decreased significantly from 47.8 ± 2.84 to 30.1 ± 2.4 (P < .01).

CONCLUSIONS

CCR-CXL protocol is safe and effective in arresting keratectasia progression and increasing corneal optic regularity in keratoconus. These findings showed a significant improvement in CDVA, keratometry values and corneal optical aberrations after being treated with the CCR-CXL protocol.

Outcomes After Corneal Crosslinking for Keratoconus in Children and Young Adults

PURPOSE

The aim of this study was to assess the effect of corneal crosslinking on vision and keratometry in children and young adults with progressive keratoconus.

METHODS

A retrospective medical records review of patients aged 22 years or younger with keratoconus who underwent corneal crosslinking between January 2013 and November 2019 at Byers Eye Institute at Stanford University was conducted. Outcome measures included logarithm of the Minimum Angle of Resolution corrected distance visual acuity (CDVA); keratometry, including maximum keratometry (Kmax); pachymetry; and total wavefront aberration. Measurements were taken at baseline and at 12 and 24 months postoperatively.

RESULTS

Fifty-seven eyes of 49 patients aged 12 to 22 years were assessed. The mean preoperative CDVA was logarithm of the Minimum Angle of Resolution 0.38 ± 0.32 (20/48), with a mean postoperative CDVA of 0.29 ± 0.31 (20/39) and 0.31 ± 0.31 (20/41) at 12 and 24 months postoperatively, respectively. Compared with preoperative mean Kmax, there was an improvement of -0.8 diopters (D) to a mean postoperative Kmax of 59.1 ± 9.1 D at 12 months and -1.3 D to 59.7 ± 8.8 D at 24 months. Subanalysis excluding the second eye of patients who underwent bilateral crosslinking showed similar results. Linear mixed modeling showed significant improvement in Kmax at both 12 and 24 months postoperatively. Minimum central corneal thickness initially decreased but stabilized at 24 months after crosslinking. Total wavefront aberration remained stable.

CONCLUSIONS

Corneal crosslinking stabilizes, and in some cases improves, visual and corneal parameters in pediatric and young adult patients with keratoconus. The procedure is safe and well-tolerated and may prevent keratoconus progression in young patients.

Delayed Topographical and Refractive Changes Following Corneal Cross-Linking for Keratoconus

Background: The aim of this study was to analyze the long-term topographic and refractive outcomes of corneal cross-linking (CXL) in keratoconus. Methods: We used a retrospective observational study of patients with keratoconus who underwent CXL with a minimum follow-up of 5 years. Patients’ refractive and topography data (corrected distance visual acuity, sphere, cylinder, average and maximum keratometry, and corneal aberrations) were collected. Results: A total of 112 patients/150 eyes (mean age: 33.2 ± 10.7 years; range: 13−61) were included. The mean follow-up was 5.87 ± 1.35 years (range: 5−10). At the last follow-up visit, an improvement in CDVA, spherical and cylindrical refraction, average and steepest keratometry, and corneal aberrations were observed (p < 0.05), with the exception of trefoil. At the last visit, 49 (34.8%) and 31 (22.0%) eyes had an improvement beyond 1D in their spherical and cylindrical power, respectively, and 43 (28.7%) eyes had a flattening of their steepest keratometry. Progressive improvement over time was observed for spherical refraction; max and mean-K; as well as corneal RMS, total, high, coma, and spherical aberrations (p < 0.05). More severe disease at the baseline correlated with an improvement in corneal aberrations over time. Conclusions: In addition to a progressive improvement in refractive and keratometric indices, corneal aberrations also demonstrate a steady decline with long-term follow-up after CXL, which was more pronounced in more severe patients.

Long-Term Follow-Up of Accelerated Transepithelial Corneal Crosslinking for Post-LASIK Ectasia: A Pilot Prospective Observational Study

Background: Keratectasia after corneal refractive surgery is a rare but serious postoperative complication, and reports on accelerated transepithelial corneal crosslinking (ATE-CXL)-based treatment of patients with post-laser-assisted in situ keratomileusis (LASIK) ectasia are limited. Therefore, this study evaluated the long-term efficacy and safety of ATE-CXL for progressive post-LASIK ectasia.

Methods: This prospective observational study was conducted at the Eye and ENT Hospital, Fudan University, Shanghai, China, and 25 eyes from 25 patients with post-LASIK ectasia undergoing ATE-CXL were examined. Clinical examinations were conducted preoperatively and postoperatively to assess parameters such as manifest refraction, corrected distance visual acuity (CDVA), endothelial cell density; keratometry, corneal thickness, posterior elevation and topometric indices were measured using Pentacam; sectoral pachymetry and epithelial thickness were evaluated using optical coherence tomography. A paired t-test, Wilcoxon rank-sum test, Kruskal-Wallis test, and repeated measures analysis of variance were used for statistical analysis.

Results: Participants were examined for an average of 46 months. No severe complications occurred during or after ATE-CXL. CDVA improved from 0.25 ± 0.31 preoperatively to 0.15 ± 0.17 postoperatively (p = 0.011). Maximum keratometry decreased from 55.20 ± 8.33 D to 54.40 ± 7.98 D, with no statistical significance (p = 0.074), and the central corneal thickness increased from 414.92 ± 40.96 μm to 420.28 ± 44.78 μm (p = 0.047) at the final follow-up. Posterior elevation, pachymetry, and epithelial thickness remained stable (p > 0.05) throughout the follow-up. No significant differences were noted in topometric indices, except the central keratoconus index, which decreased significantly (p < 0.001) at the final follow-up.

Conclusion: Improvements in CDVA and stabilization in corneal keratometry and posterior elevation after ATE-CXL were noted at the 46-months follow-up, demonstrating that ATE-CXL is a safe and effective treatment for progressive post-LASIK ectasia.

Comparison of efficacy and safety of accelerated trans-epithelial crosslinking for keratoconus patients with corneas thicker and thinner than 380µm

PURPOSE

Accelerated trans-epithelial cross-linking (ATE-CXL), a therapy to halt keratoconus progression, has the merit of widening the indications for thinner corneas (<380 μm). Since a hypotonic solution affects the swollen cornea, corneas of <380 μm thickness at preoperative measurement can be an indication for ATE-CXL. The aim of this retrospective study was to compare the efficacy and safety of ATE-CXL for keratoconus between corneas with thicknesses <380 μm and ≥380 μm.

MATERIALS AND METHODS

Thirty-four eyes of 27 patients who underwent ATE-CXL (30 mW/cm²; 3 minutes) with completion of a 24-month follow-up, were enrolled and divided into two groups: Group 1, thinnest corneal thickness (TCT), <380 μm (n = 10) and Group 2, TCT, ≥380 μm (n = 24). A hypotonic solution was administered to Group 1 until the corneal thickness increased by >380 μm before UV-A irradiation. We measured uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), maximum and average keratometric values (Kmax and AveK), central corneal thickness (CCT), TCT by anterior segment optical coherence tomography, and corneal endothelial cell density (ECD) using specular microscopy. The changes from baseline to 24 months postoperatively between the two groups were compared accordingly.

RESULTS

The changes in Kmax and AveK from baseline to 24 months in Group 1 (ΔKmax: -7.8±7.7 D, ΔAveK: -4.3±6.1 D) showed significant decreases compared to those in Group 2 (ΔKmax: 0.2±3.0 D, ΔAveK: 0.6±2.7 D) (p = 0.004 and p = 0.001), and there were no significant changes from baseline to 24 months postoperatively in UCVA, BCVA, CCT, TCT, and ECD in both groups.

CONCLUSION

ATE-CXL is effective and safe for keratoconic corneas in both groups. The effect of reducing keratometric values was greater in the group with thinner corneas.

Genipin in an Ex Vivo Corneal Model of Bacterial and Fungal Keratitis

Purpose

To determine whether genipin (a natural crosslinker) could reduce the colonization and proliferation of bacteria and fungi in an ex vivo model of corneal infection.

Methods

This study, using an ex vivo model of bacterial and fungal keratitis, investigated the antimicrobial efficacy of genipin crosslinking. Excised corneoscleral buttons were wounded by scalpel incision and subsequently infected with Staphylococcus aureus, Pseudomonas aeruginosa, or Candida albicans. After inoculation, corneas were treated with genipin for 24 hours at 37°C. Histologic examinations were carried out, and the number of viable colony-forming units (CFU)/cornea was determined.

Results

Genipin exerts bactericidal action against S. aureus and P. aeruginosa, as well as fungicidal action against C. albicans and significantly reduced the CFU compared to contralateral eyes that received saline treatment (P < 0.05).

Conclusions

These data identify genipin as a novel ocular antimicrobial agent that has the potential to be incorporated into the therapeutic armamentarium against microbial keratitis.

Translational Relevance

This study provided evidence for the antimicrobial and antifungal properties of genipin as an alternative crosslinker that could be used in the management of infectious keratitis.

Early identification of keratoconus using pachymetric indexes obtained with spectral domain optical coherence tomography

Purpose

To evaluate the diagnostic ability of pachymetric indexes obtained with Spectral Domain Optical Coherence Tomography (SD-OCT) for early detection of keratoconus (Kc).

Methods

64 patients with Kc in at least one eye (95 eyes, 46 men and 18 women, average age 27.84 ±13.50), 59 healthy control subjects (100 eyes, 28 men and 31 women, average age 27.15 ±16.14). All patients underwent detailed clinical examination, topography and anterior segment OCT. 37 subjects (37 eyes, 27 men and 10 women, average age 24.23 ± 14.24) having one eye with manifest Kc and the fellow eye without clinical signs of Kc were identified. We studied two groups of pachymetric indexes: C1-C2, M1-M2, pCLMI, Pmin-P2 (Group 1 indexes) and PPD, PSD, PSSD and PASD (Group 2 indexes). A ROC (Receiver Operating Characteristic) curve was developed to compare the diagnostic accuracy, relative sensitivity and specificity for each index.

Results

In manifest keratoconus, C1-C2, M1-M2, and pCLMI are significantly higher compared to the control group (P<0.0001); for suspect keratoconus, all Group 1 indexes are significantly higher compared to healthy subjects (P<0.0001) excluding M1-M2 obtained using a constant area circle (P = 0.02). Furthermore, for manifest and suspect keratoconus, PPD, PSD, PSSD and PASD are significantly higher compared to the control group (P <0.0001).

Conclusion

The studied pachymetric indexes in patients with Kc have high diagnostic accuracy and are statistically significant when compared with healthy subjects (p<0.0001) and can provide a useful tool for keratoconus screening.

Long-Term Follow-Up of Combined Photorefractive Keratectomy and Corneal Crosslinking in Keratoconus Suspects

Purpose

To present the long-term outcomes of photorefractive keratectomy (PRK) combined with accelerated corneal cross-linking (CXL) for refractive error correction in a series of keratoconus suspects.

Setting

University practice.

Design

Retrospective case series.

Methods

A series of patients with topographic findings suspicious for keratoconus underwent simultaneous PRK and prophylactic accelerated CXL (5 minutes with intensity of 18 mW/cm²) for the correction of their refractive error. The results were recorded for more than 4 years postoperatively.

Results

Ten eyes of 5 patients were included. Mean follow-up was 58.2 months (range from 54 to 62 months). Mean age at presentation was 25 years (range from 22 to 32 years). Mean spherical equivalent (SE) refraction was −2.76 (standard deviation [SD] 0.97D, range from −1.25 to −4.00 diopters [D]), while mean central corneal thickness was 511μm (SD 13μm, range from 485 to 536 μm). At last, follow-up 9 out of 10 eyes had SE refraction within ± 0.50D and all eyes had SE within ± 1.00D. None of the eyes lost any line of corrected distance visual acuity (CDVA), whereas 1 eye gained one line of CDVA. All eyes demonstrated stability of their results during the follow-up period.

Conclusion

Simultaneous PRK followed by prophylactic accelerated CXL (PRK plus) appeared to be a safe and effective option for the correction of the refractive error in this series of keratoconus suspect patients, without compromising corneal stability for up to 5 years postoperatively.

Corneal Crosslinking Biomechanics Evaluated by a Novel and Easily Implemented Differential Tonometry Method

Purpose: Evaluate potential corneal biomechanical changes following corneal crosslinking (CXL) by paired differential tonometry intraocular pressure (IOP) measurements with a Goldmann tonometer (GAT) prism and corneal compensating, correcting applanation tonometry surface (CATS) prism.Methods: IOP was measured prospectively on 23 unique eyes undergoing CXL for keratoconus with a GAT using a standard flat GAT prism and a curved corneal error correcting CATS prism before treatment and at 2 weeks, 2 months and 6 months after treatment. Concurrent measurements of central corneal thickness (CCT) and corneal hysteresis (CH) were completed.Results: Paired IOP measurements with standard GAT and corneal correcting CATS prisms indicated a significant sustained relative increase in the differential IOP between the two prisms after CXL (p = .002,0.051,0.062). CH initially decreased at two weeks post-CXL then returned to sustained pre-op levels (p = .033,0.20,0.20). CCT progressively decreased following CXL (p = .005).Discussion: Differential tonometry between standard GAT and corneal biomechanical compensating CATS prisms indicates findings consistent with increased corneal rigidity following CXL and may demonstrate a simple and sensitive method for measurement of relative corneal biomechanical changes due to pharmacologic agents and procedures.

The Effect of Sodium Iodide on Stromal Loading, Distribution and Degradation of Riboflavin in a Rabbit Model of Transepithelial Corneal Crosslinking

Purpose

To evaluate effects of sodium iodide (NaI) on riboflavin concentration in corneal stroma before and during ultraviolet A (UVA) light exposure using a novel transepithelial corneal collagen crosslinking (CXL) procedure (EpiSmart CXL system, CXL Ophthalmics, Encinitas CA).

Methods

Riboflavin solutions with NaI (Ribostat, CXL Ophthalmics, Encinitas CA) and without NaI were used for CXL in rabbits using EpiSmart. A pilot study determined sufficient riboflavin loading time. Four rabbits were dosed and monitored. Riboflavin fluorescence intensity was assessed from masked slit-lamp photos. A 12 min loading time was selected. Sixteen additional rabbits received the two formulae in contralateral eyes for CXL. Riboflavin uptake was assessed at 0, 10, 15, 20, 25, and 30 min of UVA exposure using a scale for riboflavin fluorescence previously validated against stromal concentration. Post sacrifice, corneal stromal samples were analyzed for concentrations of riboflavin and riboflavin 5ʹ-phosphate.

Results

Eyes dosed with NaI riboflavin had higher riboflavin grades compared to eyes dosed with the NaI-free riboflavin formulation immediately after riboflavin loading and persisting throughout UVA exposure, with significantly higher (P < 0.01 to < 0.05) riboflavin grades from 15 through 25 min of UVA exposure. Riboflavin grades decreased more slowly in eyes dosed with NaI riboflavin through 25 minutes of UVA exposure. Minor conjunctival irritation was noted with or without NaI.

Conclusion

The addition of NaI to riboflavin solution is associated with increased riboflavin concentration in corneal stroma throughout a clinically relevant time course of UVA exposure. This effect may be a combination of enhanced epithelial penetration and reduced riboflavin photodegradation and should enhance intrastromal crosslinking.

A review of corneal biomechanics: Mechanisms for measurement and the implications for refractive surgery

Detailed clinical assessment of corneal biomechanics has the potential to revolutionize the ophthalmic industry through enabling quicker and more proficient diagnosis of corneal disease, safer and more effective surgical treatments, and the provision of customized and optimized care. Despite these wide-ranging benefits, and an outstanding clinical need, the provision of technology capable of the assessment of corneal biomechanics in the clinic is still in its infancy. While laboratory-based technologies have progressed significantly over the past decade, there remain significant gaps in our knowledge regarding corneal biomechanics and how they relate to shape and function, and how they change in disease and after surgical intervention. Here, we discuss the importance, relevance, and challenges associated with the assessment of corneal biomechanics and review the techniques currently available and underdevelopment in both the laboratory and the clinic.

Outcomes of Conductive Keratoplasty Combined with Corneal Crosslinking in Advanced Ectatic Corneal Disease

Purpose

To assess the effectiveness of a novel treatment for patients with advanced corneal ectasia and loss of visual acuity (VA). Conductive keratoplasty (CK) is performed to improve VA followed by epithelium-on (epi-on) corneal crosslinking (CXL) to stabilize the cornea after CK.

Methods

Retrospective, exploratory cohort study. Patients with keratoconus or postsurgical ectasia and best spectacle-corrected distance VA (CDVA) ≤ 20/40 were included. Conductive keratoplasty was performed (ViewPoint CK System, Refractec, Inc., Bloomington, MN); followed a day later by epi-on CXL (CXLUSA/CXLO, Bethesda, MD/CXLO Encinitas, CA). Measures included uncorrected distance visual acuity (UDVA) and CDVA, as well as refractive and tomographic measures and tomographic indices.

Results

Data from 50 eyes of 45 patients were analyzed. Mean follow-up was 15.1 ± 12.2 months (range: 2 to 51). Overall, UDVA and CDVA improved postoperatively. Subjective refraction and tomographic metrics did not show consistent changes, but changes in tomographic indices were associated with treatment follow-up time. At the 1-year visit, mean UDVA significantly improved over baseline (P = 0.009) by approximately 3 lines; mean CDVA improved significantly (P = 10⁻⁵) by approximately 2 lines. No eye lost lines of CDVA. Change in the Index of Surface Variance (ISV) was associated with treatment, and the D-Index trended over follow-up time.

Conclusion

Conductive keratoplasty with a proprietary epi-on CXL treatment improved vision in patients with advanced ectasia This CK/epi-on CXL treatment offers the possibility of improved VA for patients with compromised vision due to ectasia.

Case Report: Successful Management of Refractory Keratomycosis in an Alpaca Using Penetrating Keratoplasty and Combination Antifungal Therapy (Caspofungin 0.5% and Terbinafine 1%)

Fungal keratitis is a common disease in certain parts of the world and affects several species, including equids, camelids, and homo sapiens, leading to blindness or loss of the eye if the infection is not adequately controlled. Reports of clinical use of antifungals caspofungin and terbinafine are limited across both veterinary and human medical literature. The alpaca presented in this case demonstrates that deep keratomycosis can be caused by Scopulariopsis brevicaulis and Fusarium verticillioides, two previously unreported fungi to cause keratomycosis in camelids. This report demonstrates successful management with a combination of surgery and topical ophthalmic treatment with caspofungin 0.5% solution and terbinafine 1% dermatologic cream, after initially failing treatment with topical voriconazole 1% solution. Combination therapy appears more effective than monotherapy with some fungal organisms, and synergy between antifungal agents is thought to play a role in the success of combination therapy. Surgery to remove the bulk of the fungal infection is especially helpful in cases that fail initial medical therapy.

Predicting Keratoconus Progression and Need for Corneal Crosslinking Using Deep Learning

We aimed to predict keratoconus progression and the need for corneal crosslinking (CXL) using deep learning (DL). Two hundred and seventy-four corneal tomography images taken by Pentacam HR^® (Oculus, Wetzlar, Germany) of 158 keratoconus patients were examined. All patients were examined two times or more, and divided into two groups; the progression group and the non-progression group. An axial map of the frontal corneal plane, a pachymetry map, and a combination of these two maps at the initial examination were assessed according to the patients’ age. Training with a convolutional neural network on these learning data objects was conducted. Ninety eyes showed progression and 184 eyes showed no progression. The axial map, the pachymetry map, and their combination combined with patients’ age showed mean AUC values of 0.783, 0.784, and 0.814 (95% confidence interval (0.721–0.845) (0.722–0.846), and (0.755–0.872), respectively), with sensitivities of 87.8%, 77.8%, and 77.8% ((79.2–93.7), (67.8–85.9), and (67.8–85.9)) and specificities of 59.8%, 65.8%, and 69.6% ((52.3–66.9), (58.4–72.6), and (62.4–76.1)), respectively. Using the proposed DL neural network model, keratoconus progression can be predicted on corneal tomography maps combined with patients’ age.

Efficacy of two silicone-hydrogel bandage contact lenses after corneal crosslinking

Silicone-hydrogel (SiH) contact lenses are frequently used as a bandage after anterior segment surgical procedures. Several types of lenses may exhibit clinical performances with different characteristics. This study aims to evaluate the efficacy of two SiH contact lenses following corneal crosslinking (CXL). Forty-nine keratoconus patients scheduled for consecutive CXL surgery in both eyes were included in this comparative, double-blind, prospective study. A Balafilcon A (Pure Vision 2 HD, Bausch+Lomb, Rochester, NY, USA) or Lotrafilcon B (Air Optix Aqua, Ciba Vision, Duluth, GA, USA) lens was fitted in a randomised fashion in the eyes at the end of the CXL. Remaining epithelial defect area measured by slitlamp biomicroscopy, subjective level of pain and discomfort with visual analogue scale (VAS) and total number of oral analgesics taken were evaluated and compared at post-operative days 0, 1, 2 and 3. The average epithelial defect size was significantly smaller in the eyes with Lotrafilcon B than the eyes with Balafilcon A at post-operative Day 1 (31.2 ± 4.3 mm² and 33.8 ± 5.2 mm², respectively, p < 0.001) and Day 2 (8.2 ± 3.6 mm² and 10.5 ± 5.4 mm², respectively, p = 0.039). There was no statistically significant in the average epithelial defect size between the groups at Day 3 (p = 0.859). Re-epithelialisation time was similar in both groups (p = 0.317) There was no statistically significant difference in VAS scores regarding the lens type in any post-operative follow-up. The mean oral analgesic numbers were similar in both groups (p = 0.217). SiH contact lenses can be used as an effective bandage for corneal re-epithelialisation after CXL. The material and features of bandage contact lens used after CXL may affect the corneal re-epithelialisation process. Lotrafilcon B lens showed faster re-epithelialisation at post-operative days 1 and 2 after CXL.

Ocular Pulse Elastography: Imaging Corneal Biomechanical Responses to Simulated Ocular Pulse Using Ultrasound

Purpose

In vivo evaluation of corneal biomechanics holds the potential for improving diagnosis and management of ocular diseases. We aimed to develop an ocular pulse elastography (OPE) technique to quantify corneal strains generated by naturally occurring pulsations of the intraocular pressure (IOP) using high-frequency ultrasound.

Methods

Simulated ocular pulses were induced in whole porcine and human donor globes to investigate the effects of physiologic variations in baseline IOP, ocular pulse amplitude, and frequency on corneal strains. Ocular pulse-induced strains were measured in additional globes before and after UVA-riboflavin-induced corneal crosslinking. The central cornea in each eye was imaged with a 50-MHz ultrasound imaging system and correlation-based speckle tracking of radiofrequency data was used to calculate tissue displacements and strains.

Results

Ocular pulse-induced corneal strains followed the cyclic changes of IOP. Both baseline IOP and ocular pulse amplitude had a significant influence on strain magnitude. Variations in pulse frequency within the normal human heart rate range did not introduce detectable changes in corneal strains. A significant decrease of corneal strain, as quantified by the OPE technique, was observed after corneal crosslinking. The extent of corneal stiffening (i.e., strain reduction) seemed to correlate with the initial strain magnitude.

Conclusions

This ex vivo study demonstrated the feasibility of the OPE method to quantify corneal strains generated by IOP pulsation and detect changes associated with corneal crosslinking treatment.

Translational Relevance

Integrating in vivo measurement of IOP and ocular pulse amplitude, the OPE method may lead to a new clinical tool for safe and quick biomechanical evaluations of the cornea.

Treatment-Resistant Bacterial Keratitis: Challenges and Solutions

Bacterial keratitis is an important ophthalmic emergency and one of the most common causes of corneal blindness. The main causes of treatment resistance in bacterial keratitis are failure to eliminate predisposing factors, misdiagnosis and mistreatment. At first, exogenous, local and systemic predisposing factors that disturbing ocular surface must be eliminated to improve corneal ulcers and to prevent recurrences. Smears and scrapings for staining and culture are indispensable diagnostic tools for cases of sight-threatening keratitis (centrally located, multifocal, characterized by melting, painful). Main treatment agents in bacterial keratitis treatment are topical antibiotics. Until the results of culture antibiograms reach the ophthalmologist, empirical antibiotic selections based on direct microscopic examination and gram stain findings are the most appropriate initial treatment approach currently. S. aureus and coagulase-negative staphylococci (CoNS), the most common gram-positive agents, have resistance rates of more than 30% for fluoroquinolone and methicillin. Multidrug resistance rates are similarly high in these microorganisms. P. aeruginosa is the most common gram-negative micro-organism, in case of multidrug-resistant isolates, both functional and anatomical prognosis of the eyes are very poor. In cases of sight-threatening and resistant keratitis, antibiotic susceptibility testing containing imipenem, colistin, and linezolid is seeming to be an important requirement. Despite its efficiency limited to superficial cases, a nonpharmaceutical anti-infective treatment option such as corneal crosslinking for bacterial keratitis is an emerging hope, while antibiotic resistance increases.

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Corneal crosslinking in a case with Axenfeld-Rieger syndrome and unilateral pellucid marginal degeneration

A 31-year-old male patient presented with the complaint of progressive vision loss in his left eye. Slit-lamp examination showed posterior embryotoxon, iris hypoplasia, and iridocorneal adhesion in both eyes, corectopia in the right, and peripheral inferior thinning and ectasia in the left eye. Corneal topography showed slightly asymmetric bowtie pattern in the right eye and crab-claw pattern in the left eye. Topographic examination was compared with his previous topography. The comparison showed 1.6-D steepening of maximum keratometry (K_max) and 22-µm decrease of thinnest corneal pachymetry. Corneal crosslinking treatment was performed on the left eye. At the postoperative 28-month follow-up visit, K_max decreased from 54.1 to 53.0 D and corrected distance visual acuity improved to 20/20 with scleral lens. This is the first reported a case with Axenfeld–Rieger syndrome and pellucid marginal degeneration association. We suggest that corneal crosslinking can be useful for management of pellucid marginal degeneration and longer follow-up might be needed in order to corroborate the effectiveness of the corneal crosslinking procedure.

Characterization of Corneal Epithelial Cells in Keratoconus

Purpose

We studied the cellular characteristics of epithelial cells in the cone and extraconal periphery of corneas in keratoconus eyes.

Methods

This prospective observational study was conducted at Narayana Nethralaya Eye Institute. A total of 83 and 42 eyes with keratoconus and normal topography, respectively, were included in the study. Corneal epithelial cells were collected and analyzed for apoptosis, proliferation, epithelial-mesenchymal transition, and differentiation status using molecular and biochemical tools. Statistical analysis was performed using the Student's t-test.

Results

Corneal epithelial cells from the cone showed significantly higher expression of proapoptotic marker BAX (P < 0.005) compared to controls. Significantly elevated expression of cell cycle markers CYCLIN D1 (P < 0.005) and Ki67 (P < 0.005) were noted in the extraconal region compared to controls. Cells of the cone showed significantly higher ZO-1 (P < 0.005) and lower vimentin (P < 0.005) compared to controls. Significantly lower expression of the differentiation marker CK3/12 (P < 0.05) was observed in cones compared to controls.

Conclusions

Cones of keratoconic corneas show enhanced cell death, poor differentiation, proliferation and epithelial-mesenchymal transition. The cellular changes of the corneal epithelial cells in the cone and extraconal region differ significantly in a keratoconus corneas.

Translational Relevance

Characterization of patient-specific corneal epithelial cellular status in keratoconus has the potential to determine the optimal treatment and therapeutic outcomes paving the way towards personalized treatment in the future.

Differential Gene Transcription of Extracellular Matrix Components in Response to In Vivo Corneal Crosslinking (CXL) in Rabbit Corneas

Purpose

We studied changes in gene transcription after corneal crosslinking (CXL) in the rabbit cornea in vivo and identified potential molecular signaling pathways.

Methods

A total of 15 corneas of eight male New-Zealand-White rabbits were de-epithelialized and equally divided into five groups. Group 1 served as an untreated control. Groups 2 to 5 were soaked with 0.1% riboflavin for 20 minutes, which in Groups 3 to 5 was followed by UV-A irradiation at a fluence of 5.4 J/cm². Ultraviolet A (UVA) irradiation was delivered at 3 mW/cm² for 30 minutes (Group 3, standard CXL protocol), 9 mW/cm² for 10 minutes (Group 4, accelerated), and 18 mW/cm² for 5 minutes (Group 5, accelerated). At 1 week after treatment, corneal buttons were obtained; mRNA was extracted and subjected to cDNA sequencing (RNA-seq).

Results

A total of 297 differentially transcribed genes were identified after CXL treatment. CXL downregulated extracellular matrix components (collagen types 1A1, 1A2, 6A2, 11A1, keratocan, fibromodulin) and upregulated glycan biosynthesis and proteoglycan glycosylation (GALNT 3, 7, and 8, B3GALT2). Also, CXL activated pathways related to protein crosslinking (transglutaminase 2 and 6). In 9.1% of the significantly different genes, CXL at 3 mW/cm² (Group 1) induced a more distinct change in gene transcription than the accelerated CXL protocols, which induced a lower biomechanical stiffening effect.

Conclusions

Several target genes have been identified that might be related to the biomechanical stability and shape of the cornea. Stiffening-dependent differential gene transcription suggests the activation of mechano-sensitive pathways.

Translational Relevance

A better understanding of the molecular mechanisms behind CXL will permit an optimization and individualization of the clinical treatment protocol.

[Results of corneal crosslinking for pellucid marginal corneal degeneration]

AIM

to evaluate the clinical effectiveness of crosslinking in patients with progressive pellucid marginal corneal degeneration (PMCD).

MATERIAL AND METHODS

A total of 9 patients (16 eyes) with progressive PMCD were treated by standard crosslinking. The cornea was saturated with Dextralink solution and UV-A irradiated at 3 mW/cm2 for 30 minutes. The follow-up period was 12 months.

RESULTS

One month after treatment, there was a slight decrease in uncorrected and best corrected visual acuity (UCVA and BCVA) - from 0.08±0.03 and 0.4±0.15 preoperatively down to 0.06±0.02 and 0.3±0.07, respectively, caused by pseudohaze of the cornea. Keratometric parameters (the average refractive power of the cornea, corneal astigmatism, and corneal thickness) did not change significantly. The demarcation line was identified in 56% of cases. By the 3-month follow-up, UCVA and BCVA improved up to 0.1±0.07 and 0.52±0.1, respectively. The refractive power of the cornea decreased by 2.0 diopters and corneal astigmatism - by 0.7 diopters reaching 46.8±2.7 and 5.1±1.3 diopters, respectively (p≤0.04). Central corneal thickness decreased by an average of 29 microns. The demarcation line remained visible in 25% of cases. At 6 months, BCVA averaged 0.58±0.13, at that, 56% of eyes gained 1 line and 31% - 2 lines. The refractive power of the cornea decreased down to 45.7±1.6 diopters, corneal astigmatism - down to 4.8±1.5 diopters. The demarcation line was not detected. At 1 year, there were no significant changes in the average values of optometric indices as compared to the 6-month period. Сonclusion. Pellucid marginal corneal degeneration should be regarded as a kind of primary ectasia, often bilateral and notable for its characteristic clinical picture and late onset. In progressive disease, photochemical crosslinking of the cornea contributes to the improvement of optometric parameters and stabilization of the process.

Outcomes of corneal crosslinking for central and paracentral keratoconus

BACKGROUND

The aim of the study was to compare the therapy of corneal collagen crosslinking (CXL) for central and paracentral keratoconus.

METHODS

64 eyes of 43 central keratoconus patients whose highest power of the cornea located in the central 3 mm zone and 24 eyes of 16 paracentral keratoconus patients whose highest power located out of the central 3 mm zone received standard corneal CXL were included. Maximum keratometry (Kmax) and astigmatism according to topography, uncorrected distant visual acuity (UDVA), corrected distant visual acuity (CDVA) were studied preoperatively and 2 years postoperatively.

RESULTS

Central group: Preoperative UDVA and CDVA were 0.9 ± 0.4 and 0.5 ± 0.4 logMAR, respectively. At 2 years, UDVA and CDVA significantly improved to 0.8 ± 0.4 and 0.4 ± 0.3 logMAR(P < 0.01). Preoperative Kmax and astigmatism were 61.5 ± 14.7 diopter (D) and 4.0 ± 2.9 D, respectively. At 2 years, Kmax and astigmatism significantly decreased to 57.0 ± 10.4 and 3.0 ± 2.2 D (P < 0.01). Paracentral group: preoperative UDVA and CDVA were 0.8 ± 0.7 and 0.2 ± 0.4 logMAR, respectively. At 2 years, UDVA significantly improved to 0.4 ± 0.4 logMAR(P < 0.01), whereas CDVA remained 0.2 ± 0.3 logMAR(P > 0.05). Preoperative Kmax and astigmatism were 50.3 ± 5.3 and 2.4 ± 1.7 D, respectively. At 2 years, Kmax significantly decreased to 48.8 ± 4.6 (P < 0.01), whereas astigmatism remained 2.2 ± 1.8 D (P > 0.05).

CONCLUSION

This study indicated that CXL was more effective for central keratoconus than paracentral keratoconus.

Phototoxic Effect of Topical Fluoroquinolones Administered Before Corneal Crosslinking in a Murine Model

PURPOSE

Corneal crosslinking by UV light (UV-CXL) has become a popular treatment for keratoconus and corneal ectasia. Fluoroquinolones (FQs), commonly administered topically before UV-CXL, are known to be phototoxic to the skin and lens. The purpose of this study was to investigate phototoxic effects of topical FQ treatment on murine corneas before UV-CXL, in which the corneal epithelium was kept intact.

METHODS

Murine corneas were treated with various antibiotics with or without riboflavin before UV-CXL. At 24 h, the animals were sacrificed, and the corneas were analyzed for histologic evidence of inflammation and apoptosis and for expression of apoptosis markers BAX and caspases 3 and 9 and for expression of matrix metalloproteinase 9 (MMP-9). Spectrofluorometric analysis was performed.

RESULTS

Corneas treated with topical FQ with or without riboflavin before UV-CXL showed mild corneal stromal inflammation, apoptosis by both terminal deoxynucleotidyl transferase dUTP nick end labeling staining and increased expression of BAX gene and caspases 3 and 9 by densitometric analysis. Untreated corneas, corneas treated with azithromycin before UV-CXL, and corneas undergoing UV-CXL without any antibiotic or riboflavin pretreatment showed normal histology, no staining for apoptosis, and no increased production of apoptosis markers by polymerase chain reaction.

CONCLUSIONS

The phototoxic effects of FQs on the cornea may lead surgeons to consider another antibiotic class for prophylaxis against infectious keratitis in UV-CXL. These effects, along with the known cytotoxic effects of FQs independent of UV radiation, may contribute to some of the complications of corneal UV-CXL. Dosage studies may be warranted.

Therapeutic and inducing effect of corneal crosslinking on infectious keratitis

The corneal crosslinking (CXL) with riboflavin and ultraviolet-A (UVA) is a new therapy method to successfully treat infectious keratitis in clinical practice. However, there are rare reports on the complications of CXL such as the secondary keratitis. The diverse clinical outcomes on keratitis have highlighted the necessity to further evaluate the efficacy and complications of CXL. We reviewed the positive and negative reports on UVA/riboflavin related with keratitis and provided our opinion on the therapeutic and side effect of UVA/riboflavin crosslinking on keratitis.

Combining corneal crosslinking and phakic toric Implantable Collamer Lenses for the treatment of keratectasia: A case report

The present study reports the use of a phakic toric Implantable Collamer Lens (ICL) that improved the refraction correction of high myopia and astigmatism in a case of keratectasia following corneal cross-linking. A 31-year-old male was diagnosed with keratectasia 12 years after laser-assisted in situ keratomileusis (LASIK). Following LASIK, the manifest refraction was -3.50-2.25×90 [0.1 logarithmic expression (LogMAR) best corrected visual acuity (BVCA)] in the right eye and -8.00-3.50×175 (0.3 LogMAR BCVA) in the left eye, with a LogMAR uncorrected distance visual acuity (UDVA) of 0.8 and a 'counting fingers' value of 3 ft (CF @3 ft) in the left and right eyes, respectively. Riboflavin/ultraviolet A light (UVA) corneal crosslinking (CXL) was conducted on both eyes. Seven months after cross-linking, LogMAR UDVA was 0.4, the manifest refraction was -2.75-2.50×85 and LogMAR BCVA was 0.1 in the right eye. In the left eye, LogMAR UDVA was CF @3 ft, the manifest refraction was -15.00 and LogMAR BCVA was 0.3. The corneal topography was stable 7 months after CXL. Phakic toric ICL was implanted to correct the refractive error, following which the LogMAR UDVA improved to 0.1 in the right eye and 0.3 in left eye, and visual acuity remained stable for 6 months after ICL implantation. In conclusion, combining riboflavin/UVA corneal cross-linking and phakic toric ICL implantation may be an alternative in the correction of high refractive error in patients with keratectasia.

Initial results from mechanical compression of the cornea during crosslinking for keratoconus

PURPOSE

To compare refractive changes after corneal crosslinking with and without mechanical compression of the cornea.

METHODS

In a prospective, open, randomized case-control study conducted at the Department of Ophthalmology, Umeå University Hospital, Sweden, sixty eyes of 43 patients with progressive keratoconus aged 18-28 years planned for corneal crosslinking and corresponding age- and sex-matched control subjects were included. The patients were randomized to conventional corneal crosslinking (CXL; n = 30) or corneal crosslinking with mechanical compression using a flat rigid contact lens sutured to the cornea during treatment (CRXL; n = 30). Subjective refraction and ETDRS best spectacle-corrected visual acuity (BSCVA), axial length measurement, keratometry and pachymetry were performed before and 1 and 6 months after treatment.

RESULTS

The keratoconus patients had poorer BSCVA, higher refractive astigmatism and higher keratometry readings than the control subjects at baseline (p < 0.01). In the CXL group, BSCVA increased from 0.19 ± 0.26 to 0.14 ± 0.18 logMar (p = 0.03), and the spherical equivalent improved from -1.9 ± 2.8 D to -1.4 ± 2.4 D (p = 0.03). Maximum keratometry readings decreased after CXL from 53.1 ± 4.9 D to 52.6 ± 5.2 D (p = 0.02), and the axial length decreased in the CXL group, likely due to post-treatment corneal thinning (p = 0.03). In the CRXL group, all the above variables were unaltered (p > 0.05).

CONCLUSION

At 6 months, the refractive results from CRXL did not surpass those of conventional CXL treatment. Rather, some variables indicated a slightly inferior effect. Possibly, stronger crosslinking would be necessary to stabilize the cornea in the flattened configuration achieved by the rigid contact lens.