Corneal cross-linking for treatment of keratoconus relapse in post-keratoplasty eyes

PURPOSE

Keratoconus relapse after penetrating keratoplasty is a rare condition that may result in severe visual deterioration and corneal graft thinning. Therefore, treatment to stabilize the cornea should be considered. The purpose of this study was to evaluate the safety and efficacy of Corneal Cross-Linking (CXL) in eyes with relapse of keratoconus after penetrating keratoplasty for keratoconus.

MATERIALS AND METHODS

A retrospective review of eyes that developed keratoconus relapse following a penetrating keratoplasty and treated with CXL. The main outcome measures were change in maximal keratometry (Kmax), best-corrected distance visual acuity (BCVA), thinnest corneal thickness (TCT) and central corneal thickness (CCT), and complications.

RESULTS

We identified 10 consecutive eyes of 9 patients. Preoperative median BCVA before the CXL and 1 year after the CXL procedure remained stable (p = 0.68). The median (IQR) of Kmax improved from 63.2 (24.9) D before the CXL procedure to 62.2 (27.1) D at 1 year postoperatively (P = 0.028). Median TCT and CCT also remained with no significant change 1 year after CXL. No complications were noted following the procedure.

CONCLUSION

CXL in eyes with keratoconus relapse after keratoplasty is a safe and effective procedure enabling not only visual stabilization but also might bring keratometry improvement. Routine follow-up after keratoplasty should be performed for early detection of keratoconus relapse and CXL is timely advised when such a relapse is documented.

Evaluation of Biomechanical Changes After Accelerated Cross-Linking in Progressive Keratoconus: A Prospective Follow-Up Study

PURPOSE

The aim of this study was to analyze the biomechanical effect of accelerated corneal cross-linking (9*10) in progressive keratoconus (KC) in comparison to untreated fellow eyes using Scheimpflug-based tonometry (Corvis ST, CVS).

METHODS

Forty-three eyes of 43 patients with KC showed progressive KC and were treated using accelerated corneal cross-linking. Twenty-five untreated fellow eyes were used as the control group. All eyes were examined biomechanically (CVS) and tomographically (Pentacam) at baseline, after 1-month, 6-month, and 12-month follow-up. Statistical analysis was performed using a linear mixed model. A logistic regression was performed to attribute the effects of changes in each parameter to treatment status (treated or untreated).

RESULTS

Maximum keratometry values decreased statistically significantly at 12 months by -1.1 D (95 confidence interval: -2.0 to -0.1, P = 0.025) compared with baseline. Thinnest corneal thickness decreased significantly after 1 month ( P < 0.001) and recovered to baseline after 12 months ( P = 0.752). In the corneal cross-linking (CXL) group, biomechanical changes were observed by an increased bIOP, a shorter A2 time, and a lower integrated radius after 1 month (all P < 0.05). No biomechanical and tomographical changes were observed in the control group (all P > 0.05). Logistic regression pointed out that treated eyes can be separated from untreated eyes by differences in bIOP, corneal thickness, A1 velocity, integrated radius, and Kc mean at 1, 6, and 12 months.

CONCLUSIONS

The alterations in biomechanical parameters indicated a corneal stiffening effect after CXL treatment, which was mostly detectable 1 month after treatment, although corneal thickness was reduced. The logistic regression model showed an adequate separation between CXL-treated and untreated eyes.

Repeatability of corneal deformation response parameters by dynamic ultra-high-speed Scheimpflug imaging before and after corneal crosslinking

PURPOSE

To evaluate the repeatability of deformation corneal response (DCR) parameters before and after corneal crosslinking (CXL) compared with their untreated fellow eyes (uFEs).

SETTING

University Hospital Carl Gustav Carus, Dresden, Germany; IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy.

DESIGN

Multicenter, interventional reliability analysis.

METHODS

53 eyes of 53 patients with keratoconus who received CXL treatment after the disease progression (CXL group) were included. Patients were measured 3 times using a dynamic Scheimpflug analyzer to determine repeatability before and 1 month after CXL treatment. The uFEs were measured in the same way (uFE group). Reliability of DCR parameters was assessed by a coefficient of repeatability, coefficient of variation, and intraclass correlation coefficient (ICC).

RESULTS

The repeatability of DCR parameters did not change after CXL compared with the preoperative values for all investigated DCR parameters ( P > .05). In the uFE group, no statistically significant shift was observed regarding the repeatability ( P > .05). An ICC greater than 0.75 was achieved in both groups for almost all parameters. Concerning the biomechanical stiffening induced by CXL, integrated inverse radius and stress-strain index were found to be statistically significantly decreased and increased ( P < .001), respectively, both indicating stiffening. No changes were observed for the uFE group.

CONCLUSIONS

The study demonstrated highly repeatable measurements of the dynamic Scheimpflug analyzer before and after CXL. The improvement of certain DCR parameters after CXL confirmed the capability of the device to detect the stiffening effect.

Corneal Crosslinking With Riboflavin and UVA Light in Progressive Keratoconus: Fifteen-Year Results

PURPOSE

To analyze the 15-year results of corneal crosslinking (CXL) in progressive keratoconus.

DESIGN

Retrospective follow-up analysis of interventional study patients.

METHODS

This study included keratoconic eyes with progressive disease treated from 2001 to 2006 at the Department of Ophthalmology, Carl Gustav Carus University Hospital, TU Dresden, Germany. CXL was performed by applying riboflavin and ultraviolet A (UVA) light according to a standard protocol. The best-corrected distance visual acuity (BCVA), slitlamp examination, and corneal topography as well as corneal thickness values were recorded preoperatively and 15 years after the treatment.

RESULTS

A total of 42 eyes received a complete follow-up of 15 years. The mean age of the patients at baseline was 26.9 (95% CI: 25.0-28.8) years. The maximum keratometry was 61.6 (95% CI: 58.2 - 64.9) diopters (D) preoperatively and 55.1 (95% CI: 51.6-58.4) D postoperatively; the decrease was statistically significant (P < .001). The mean keratometry value changed from 50.3 (95% CI: 48.3-52.4) D to 47.5 (95% CI: 45.3-49.4) D (P < 0.001). Furthermore, the thinnest corneal thickness decreased statistically significantly by 40 (95% CI: 24-56) µm (P < .001). The BCVA improved statistically significantly from 0.4 to 0.2 logMAR after the treatment. Retreatment was needed in 14% of cases. Mild scarring of the superficial stromal corneal layers was observed in 36% of the eyes, and in 67% of them visual acuity was stable or even improved.

CONCLUSIONS

The CXL procedure proved to be an effective method in the treatment of keratoconic eyes in the progressive stage of the disease, and achieved long-term stabilization without the occurrence of serious complications or side effects.

Analysis of riboflavin/ultraviolet a corneal cross-linking by molecular spectroscopy

Corneal cross-linking (CXL) with riboflavin and ultraviolet A light is a therapeutic procedure to restore the mechanical stability of corneal tissue. The treatment method is applied to pathological tissue, such as keratoconus and induces the formation of new cross-links. At present, the molecular mechanisms of induced cross-linking are still not known exactly. In this study, we investigated molecular alterations within porcine cornea tissue after treatment with riboflavin and ultraviolet A light by surface enhanced Raman spectroscopy (SERS). For that purpose, after CXL treatment a thin silver layer was vapor-deposited onto cornea flaps. To explore molecular alterations induced by the photochemical process hierarchical cluster analysis (HCA) was used. The detailed analysis of SERS spectra reveals that there is no general change in collagen secondary structure while modifications on amino acid side chains are the most dominant outcome. The formation of secondary and aromatic amine groups as well as methylene and carbonyl groups were observed. Even though successful cross-linking could not be registered in all treated samples, Raman signals of newly formed chemical groups are already present in riboflavin only treated corneas.

Comparison of corneal tomography using a novel swept-source optical coherence tomographer and rotating Scheimpflug system in normal and keratoconus eyes: repeatability and agreement analysis

Background

To determine the repeatability and agreement using corneal tomography of a swept-source optical coherence tomographer (SS-OCT) compared to a rotating Scheimpflug camera (RSC) in normal eyes and keratoconus (KC) eyes.

Methods

This prospective repeatability analysis was performed at the Department of Ophthalmology of University Hospital Carl Gustav Carus, Dresden, Germany. Forty-three normal and 57 KC eyes were enrolled in the study. Three consecutive measurements were performed by the same operator on each device. Corneal parameters of anterior and posterior corneal surface, such as simulated keratometry (SimK), as well as central and thinnest corneal thickness were evaluated. Repeatability and agreement were assessed by using the coefficient of repeatability and Bland-Altman analysis.

Results

The repeatability of anterior corneal parameters was comparable between RSC and SS-OCT in normal eyes (repeatability < 0.5 D). Repeatability was increased in mild and moderate KC for all parameters using both devices. In moderate KC, repeatability of Kmax was 1.33 D and 0.78 D for RSC and SS-OCT, respectively. Repeatability of posterior corneal parameters was consistently better for SS-OCT. Significant offsets and wide ranges of limits of agreement were found between the devices for SimK and corneal thickness values.

Conclusions

SS-OCT showed highly repeatable measurements of anterior and posterior corneal parameters in normal and KC eyes. Compared to RSC, the SS-OCT had a better repeatability of anterior corneal parameters in mild and moderate KC as well as posterior corneal parameters in all groups. Both devices should not be used interchangeably in the diagnostic process of patients.

Trial registration NCT04251143 at Clinicaltrials.gov, registered on 12 March 2018, https://clinicaltrials.gov/ct2/show/NCT04251143?cond=Keratoconus&cntry=DE&city=Dresden&draw=2&rank=1

Evaluation of Corneal Biomechanical Indices in Distinguishing Between Normal, Very Asymmetric, and Bilateral Keratoconic Eyes

PURPOSE

To evaluate the ability of biomechanical indices provided by the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments) and dynamic Scheimpflug analyzer (Corvis ST; Oculus Optikgeräte GmbH) to distinguish between normal eyes and eyes with very asymmetric ectasia (VAE) and mild and moderate keratoconus.

METHODS

This prospective, observational, and monocentric study included normal eyes (defined as keratoconus percentage index < 60, Belin/Ambrósio total deviation value [BAD-D] < 1.6, inferior-superior keratometry [I-S value] < 1.45 and maximum keratometry [Kmax] < 47) and eyes with clinical bilateral keratoconus (mild and moderate) and VAE (defined as unilateral keratoconus, where one eye showed a clinical keratoconus and the fellow eye was topographically normal [VAE-NT] or topographically and tomographically normal [VAE-NTT]). All eyes were measured by the Pentacam (Oculus Optikgeräte GmbH), ORA, and Corvis ST. Receiver operating characteristic curve analysis was performed to test the diagnostic ability.

RESULTS

Fifty-eight normal eyes and 238 ectatic eyes were included. The highest area under the curve (AUC) was provided by the Corvis Biomechanical Index (CBI) with an AUC of 0.979, followed by ORA corneal resistance factor (0.865), and corneal hysteresis (0.824) separating normal eyes from all ectatic subgroups. The AUC of the CBI was statistically significantly higher than all other parameters (DeLong test, P < .001). A sensitivity of 100% and 70.9%, respectively, and a specificity of 93.1% was found to distinguish normal eyes from VAE-NT and VAE-NTT using a cut-off value of 0.2.

CONCLUSIONS

The assessment of biomechanical properties is an additional important method to evaluate corneal ectasia independent of its stage. The CBI provides further information for ectasia screening in cases where corneal topography and tomography are clinically not suspicious by using a cutoff of 0.2. [J Refract Surg. 2022;38(6):364-372.].

Statistical Evaluation of Correlated Measurement Data in Longitudinal Setting Based on Bilateral Corneal Cross-Linking

PURPOSE

In ophthalmology, data from both eyes of a person are frequently included in the statistical evaluation. This violates the requirement of data independence for classical statistical tests (e.g. t-Test or analysis of variance (ANOVA)) because it is correlated data. Linear mixed models (LMM) were used as a possibility to include the data of both eyes in the statistical evaluation.

METHODS

The LMM is available for a variety of statistical software such as SPSS or R. The application was applied to a retrospective longitudinal analysis of an accelerated corneal cross-linking (ACXL (9*10)) treatment in progressive keratoconus (KC) with a follow-up period of 36 months. Forty eyes of 20 patients were included, whereas sequential bilateral CXL treatment was performed within 12 months. LMM and ANOVA for repeated measurements were used for statistical evaluation of topographical and tomographical data measured by Pentacam (Oculus, Wetzlar, Germany).

RESULTS

Both eyes were classified into a worse and better eye concerning corneal topography. Visual acuity, keratometric values and minimal corneal thickness were statistically significant between them at baseline (p < 0.05). A significant correlation between worse and better eye was shown (p < 0.05). Therefore, analyzing the data at each follow-up visit using ANOVA partially led to an overestimation of the statistical effect that could be avoided by using LMM. After 36 months, ACXL has significantly improved BCVA and flattened the cornea.

CONCLUSION

The evaluation of data of both eyes without considering their correlation using classical statistical tests leads to an overestimation of the statistical effect, which can be avoided by using the LMM.

Corneal Biomechanics Differences Between Chinese and Caucasian Healthy Subjects

Purpose

The aim of this study was to evaluate the difference between Caucasian and Chinese healthy subjects with regards to Corvis ST dynamic corneal response parameters (DCRs).

Methods

Two thousand eight hundred and eighty-nine healthy Caucasian and Chinese subjects were included in this multicenter retrospective study. Subsequently, Chinese eyes were matched to Caucasians by age, intraocular pressure (IOP), and Corneal Thickness (CCT) using a case-control matching algorithm. The DCRs assessed were Deformation Amplitude (DA) Applanation 1 velocity (A1v), integrated radius (1/R), deformation amplitude ratio (DAratio), stiffness parameter at applanation 1 (SPA1), ARTh (Ambrósio's Relational Thickness to the horizontal profile), and the novel Stress Strain Index (SSI).

Results

After age-, CCT-, and IOP- matching, 503 Chinese were assigned to 452 Caucasians participants. Statistical analysis showed a statistical significant difference between Chinese and Caucasian Healthy subjects in the values of SPA1 (p = 0.008), Arth (p = 0.008), and SSI (p < 0.001). Conversely, DA, A1v, DAratio, and 1/R were not significantly different between the two ethnical groups (p > 0.05).

Conclusion

We found significant differences in the values of the DCRs provided by the Corvis ST between Chinese and Caucasian healthy subjects.

Risk Factors for Progression of Keratoconus and Failure Rate After Corneal Cross-linking

PURPOSE

To assess the occurrence of risk factors for progression of keratoconus and failure rate after corneal cross-linking (CXL) in patients with progressive keratoconus.

METHODS

This retrospective study observed 230 eyes of 173 patients with a minimum follow-up of 36 months after CXL. A total of 185 eyes underwent CXL once (80%) (control) and 45 (20%) underwent this treatment more than once (Re-CXL-group). Subgroup analysis included standard CXL with the Dresden protocol (S-CXL group, n = 120) and accelerated CXL with a reduced radiation time of 10 minutes and a higher radiation power of 9 mW/cm² (A-CXL group, n = 110). Risk factors of interest were age, maximum keratometry (Kmax), minimum corneal thickness (MCT), sex, and atopy (including allergic bronchial asthma, food allergy, allergic rhinitis, and neurodermatitis).

RESULTS

Follow-up for the control group was 76.0 ± 33.2 months. Re-CXL was performed after 46.2 ± 34.1 months overall and after 62.6 ± 41.9 months in the S-CXL subgroup and 29.2 ± 19.2 months in the A-CXL subgroup (P = .02). Kaplan-Meier analysis revealed a cumulative prediction rate of success after CXL of 92.5% (S-CXL) and 86.4% (A-CXL) after 36 months (P = .103). A high preoperative Kmax value (odds ratio = 1.056, P = .003 and odds ratio = 1.067, P = .028) in both subgroups and the presence of neurodermatitis combined with other atopic diseases in the A-CXL group (odds ratio = 11.662, P = .003) were significant risk factors for new progression of keratoconus after CXL.

CONCLUSIONS

Risk factors for progression of keratoconus after CXL are both high preoperative Kmax values and the presence of neurodermatitis combined with other atopic diseases. Patients with severe atopy should receive the S-CXL procedure. [J Refract Surg. 2021;37(12):816-823.].

[Principles of corneal cross-linking : Presentation based on the development of the various treatment protocols]

BACKGROUND

Corneal cross-linking (CXL) is used to treat corneal ectatic diseases. The aim is to improve the reduced consolidation of the cornea in order to halt further corneal protrusion and therefore subsequent deterioration of the optical imaging proportions.

MATERIAL AND METHODS

In this article the principles of corneal cross-linking based on riboflavin and UV light are presented including recent research results. Furthermore, the most important treatment protocols including standard CXL (S-CXL), accelerated CXL (A-CXL), transepithelial CXL (TE-CXL) and the approach of the CXL procedure for thin corneas are explained.

RESULTS

The CXL method depends on four major components, the riboflavin solution, oxygen, UV light and the availability of cross-linking sites on the collagen tissue. According to the present state of knowledge, the photochemical process of the CXL method induces covalent bonds between the fibrils and proteoglycans and thus stabilizes the collagen fibers, resulting in corneal consolidation. In addition to the S‑CXL, which has proven its effectiveness and safety in a large number of studies, there are other treatment protocols that have been developed based on the Bunsen-Roscoe law of reciprocity. The A‑CXL protocol has the advantage of having a shorter irradiation time but it seems to be less effective than the S‑CXL protocol concerning the increase in corneal stiffness. The use of TE-CXL has so far not yet gained acceptance in the clinical practice.

CONCLUSION

The CXL procedures primarily aim to stabilize the cornea. In the future, in addition to stabilization of the cornea, simultaneous improvement of visual acuity will be the main focus.

Development of a classification system based on corneal biomechanical properties using artificial intelligence predicting keratoconus severity

Background

To investigate machine-learning (ML) algorithms to differentiate corneal biomechanical properties between different topographical stages of keratoconus (KC) by dynamic Scheimpflug tonometry (CST, Corvis ST, Oculus, Wetzlar, Germany). In the following, ML models were used to predict the severity in a training and validation dataset.

Methods

Three hundred and eighteen keratoconic and one hundred sixteen healthy eyes were included in this monocentric and cross-sectional pilot study. Dynamic corneal response (DCR) and corneal thickness related (pachymetric) parameters from CST were chosen by appropriated selection techniques to develop a ML algorithm. The stage of KC was determined by the topographical keratoconus classification system (TKC, Pentacam, Oculus). Patients who were classified as TKC 1, TKC 2 and TKC 3 were assigned to subgroup mild, moderate, and advanced KC. If patients were classified as TKC 1–2, TKC 2–3 or TKC 3–4, they were assigned to subgroups according to the normative range of further corneal indices (index of surface variance, keratoconus index and minimum radius). Patients classified as TKC 4 were not included in this study due to the limited amount of cases. Linear discriminant analysis (LDA) and random forest (RF) algorithms were used to develop the classification models. Data were divided into training (70% of cases) and validation (30% of cases) datasets.

Results

LDA model predicted healthy, mild, moderate, and advanced KC eyes with a sensitivity (S_n)/specificity (S_p) of 82%/97%, 73%/81%, 62%/83% and 68%/95% from a validation dataset, respectively. For the RF model, a S_n/S_p of 91%/94%, 80%/90%, 63%/87%, 72%/95% could be reached for predicting healthy, mild, moderate, and advanced KC eyes, respectively. The overall accuracy of LDA and RF was 71% and 78%, respectively. The accuracy for KC detection including all subgroups of KC severity was 93% in both models.

Conclusion

The RF model showed good accuracy in predicting healthy eyes and various stages of KC. The accuracy was superior with respect to the LDA model. The clinical importance of the models is that the standalone dynamic Scheimpflug tonometry is able to predict the severity of KC without having the keratometric data.

Trial registration

NCT04251143 at Clinicaltrials.gov, registered at 12 March 2018 (Retrospectively registered).

Supplementary Information

The online version contains supplementary material available at 10.1186/s40662-021-00244-4.

Long term results of accelerated 9 mW corneal crosslinking for early progressive keratoconus: the Siena Eye-Cross Study 2

Purpose

To assess clinical results of the 9 mW/5.4 J/cm² accelerated crosslinking (ACXL) in the treatment of progressive keratoconus (KC) over a span of 5 years.

Methods

The prospective open non-randomized interventional study (Siena Eye-Cross Study 2) included 156 eyes of 112 patients with early progressive KC undergoing the Epi-Off 9 mW/5.4 J/cm² ACXL at the Siena Crosslinking Centre, Italy. The mean age was 18.05 ± 5.6 years. The 20-min treatments were performed using the New KXL I (Avedro, Waltham, USA), 10 min of 0.1% HPMC Riboflavin soaking (VibeX Rapid, Avedro, Waltham, USA) and 10 min of continuous-light UV-A irradiation. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), Kmax, coma, minimum corneal thickness (MCT), surface asymmetry index (SAI), endothelial cell count (ECC) were measured, and corneal OCT performed.

Results

UDVA and CDVA improved significantly at the 3rd (P = 0.028), Δ + 0.17 Snellen lines and 6th postoperative month, respectively (P < 0.001), Δ + 0.23 Snellen lines. Kmax improved at the 6th postoperative month (P = 0.03), Δ − 1.49 diopters from the baseline value. Also, coma aberration value improved significantly (P = 0.004). A mild temporary haze was recorded in 14.77% of patients without affecting visual acuity and without persistent complications. Corneal OCT revealed a mean demarcation line depth at 332.6 ± 33.6 μm.

Conclusion

The 5-year results of Epi-Off 9 mW/5.4 J/cm² ACXL demonstrated statistically significant improvements in UCVA and CDVA, corneal curvature and corneal higher-order aberrations which confers a long-term stability for progressive ectasia. Based on the results of the Siena Eye-Cross Study 2, the 9 mW/5.4 J/cm² ACXL is a candidate to be  the natural evolution of Epi-Off CXL treatment for the management of early progressive corneal ectasia, and thus optimize clinic workflow.

Repeatability and reproducibility of corneal deformation response parameters of dynamic ultra-high-speed Scheimpflug imaging in keratoconus

PURPOSE

To assess the repeatability and reproducibility of dynamic corneal response (DCR) parameters obtained by ultra-high-speed Scheimpflug imaging (Corvis ST); in keratoconic patients.

SETTING

Clinics in Germany, Italy, and Brazil.

DESIGN

Prospective, observational study.

METHODS

Patients were examined 3 times using 2 different dynamic Scheimpflug analyzers (Corvis ST) to obtain repeatability and reproducibility. The reliability of intraocular pressure (IOP), biomechanically corrected IOP (bIOP), pachymetry, and DCR parameters were assessed by the coefficient of repeatability, coefficient of variation (CoV), intraclass correlation coefficient (ICC), and within-subject standard deviation (sw).

RESULTS

Ninety-eight eyes from 98 KC patients were included. The sw of the IOP and bIOP did not exceed 1.1 mm Hg. A CoV less than 10% was found in all DCR parameters and had a good to excellent accordance regarding the ICC. The Corvis Biomechanical Index showed an excellent repeatability and interdevice reproducibility of 0.918 and 0.827, respectively. Also, the tomographic biomechanical index showed an excellent repeatability of 3 Corvis ST and Pentacam measurements (ICC = 0.997). With regard to keratoconic severity, a significant increase in the CoV was found between mild and moderate stages compared with the advanced stage. Nevertheless, it did not exceed 10% of the CoV in severe keratoconic eyes.

CONCLUSION

Corvis ST measurements in keratoconic eyes were highly repeatable and reproducible.

Comparison of waveform-derived corneal stiffness and stress-strain extensometry-derived corneal stiffness using different cross-linking irradiances: an experimental study with air-puff applanation of ex vivo porcine eyes

Purpose

To assess corneal stiffening of standard (S-CXL) and accelerated (A-CXL) cross-linking protocols by dynamic corneal response parameters and corneal bending stiffness (Kc[mean/linear]) derived from Corvis (CVS) Scheimpflug-based tonometry. These investigations were validated by corneal tensile stiffness (K[ts]), derived from stress-strain extensometry in ex vivo porcine eyes.

Methods

Seventy-two fresh-enucleated and de-epithelized porcine eyes were soaked in 0.1% riboflavin solution including 10% dextran for 10 min. The eyes were separated into four groups: controls (n = 18), S-CXL (intensity in mW/cm²*time in min; 3*30) (n = 18), A-CXL (9*10) (n = 18), and A-CXL (18*5) (n = 18), respectively. CXL was performed using CCL Vario. CVS measurements were performed on all eyes. Subsequently, corneal strips were extracted by a double-bladed scalpel and used for stress-strain measurements. K[ts] was calculated from a force-displacement curve. Mean corneal stiffness (Kc[mean]) and constant corneal stiffness (Kc[linear]) were calculated from raw CVS data.

Results

In CVS, biomechanical effects of cross-linking were shown to have a significantly decreased deflection amplitude as well as integrated radius, an increased IOP, and SP A1 (P < 0.05). Kc[mean]/Kc[linear] were significantly increased after CXL (P < 0.05). In the range from 2 to 6% strain, K[ts] was significantly higher in S-CXL (3*30) compared to A-CXL (9*10), A-CXL (18*5), and controls (P < 0.05). At 8% to 10% strain, all protocols induced a higher stiffness than controls (P < 0.05).

Conclusion

Several CVS parameters and Kc[mean] as well as Kc[linear] verify corneal stiffening effect after CXL on porcine eyes. S-CXL seems to have a higher tendency of stiffening than A-CXL protocols have, which was demonstrated by Scheimpflug-based tonometry and stress-strain extensometry.

[Scedosporium apiospermum-a rare pathogen of keratomycosis]

This article presents the case of a 44-year-old contact lens wearer who presented with acute keratitis resistant to antibacterial treatment in the right eye. The anterior segment of the eye showed circular conjunctival hyperemia, a corneal white cell infiltrate with radiating margins and a central corneal erosion. Microbiological investigation of a corneal scraping revealed growth of Scedosporium apiospermum. Intensive antimycotic treatment and several corneal collagen crosslinking procedures were performed; however, because of rapidly evolving necrotizing ulcerative keratitis, a keratoplasty à chaud was carried out.

Influence of the beam profile crosslinking setting on changes in corneal topography and tomography in progressive keratoconus: Preliminary results

PURPOSE

To evaluate the effect of accelerated corneal crosslinking (CXL) with a "higher peripheral intensity" profile setting compared with a standard "top hat" profile setting performed using different CXL systems.

SETTING

Department of Ophthalmology, University Hospital Carl Gustav Carus, Dresden, Germany.

DESIGN

Retrospective case series.

METHODS

Eyes from patients with progressive keratoconus were included. Group 1 included eyes treated with the higher peripheral intensity profile. Group 2 included eyes treated with the top hat profile. Accelerated CXL was performed based on the modified Dresden protocol (9 mW/cm², 10 minutes). Corneal-topography and tomography are characterized using the Pentacam Scheimpflug system.

RESULTS

The study comprised 45 eyes (25 eyes in Group 1, 20 eyes in Group 2) from 45 patients. The keratometry (K) at the apex (maximum K) decreased significantly from 54.95 diopters (D) ± 6.73 (SD) to 53.21 ± 6.05 D for Group 1 (P < .001) and from 57.29 ± 7.16 D to 56.48 ± 6.88 D for Group 2 (P = .01). In Group 1, flat K (K1) and steep K (K2) decreased significantly after treatment (P < .05). The thinnest corneal thickness decreased significantly by -17.5 ± 21.9 μm (P = .001) in Group 1. In Group 2, no significant flattening was observed in K1 and K2 (P > .05), and the thinnest corneal thickness showed a slight but not significant thinning (P = .097).

CONCLUSIONS

In Group 1 (the higher peripheral intensity group), the corneal topographic and tomographic parameters improved significantly after accelerated CXL. The higher peripheral intensity profile effect on keratoconic cornea flattening seemed to be more pronounced compared with the top hat profile.

Keratokonus: heutige Therapieoptionen

Die Inzidenz des Keratokonus wird in aktuellen Studien deutlich höher geschätzt als bisher angenommen, somit wird diese Hornhautektasie nicht mehr zu den seltenen Erkrankungen gezählt. Als einer der bedeutendsten Risikofaktoren für die Entstehung des Keratokonus wurde neben Atopie und Down-Syndrom das chronische Augenreiben definiert. Dies ist der durch Verhaltenstraining und konsequente Aufklärung einzig wirklich modifizierbare Risikofaktor. Weitere Therapieoptionen beinhalten Maßnahmen zur Visusverbesserung wie die Anpassung von Brillen und formstabilen Kontaktlinsen, die Implantation kornealer Ringsegmente oder phaker intraokularer Linsen. Im Falle einer Krankheitsprogression bietet das korneale Crosslinking ein effektives und sicheres Verfahren, sodass das Erfordernis einer Hornhauttransplantation in dieser Indikation immer seltener wird. Neuere Studien sehen auch einen positiven Effekt einer Kombination der bisher bei Keratokonus kontraindizierten photorefraktiven Keratektomie und dem Crosslinking. Die perforierende Keratoplastik stellt allerdings weiterhin den Goldstandard der chirurgischen Behandlung des Keratokonus im fortgeschrittenen Stadium dar, wobei in den letzten Jahren auch die lamellären Verfahren immer mehr in den Vordergrund rücken.

[Treatment of Keratoconus by Accelerated Cross-linking]

This study evaluates the efficacy of treatment of progressive keratoconus using Accelerated Corneal Collagen cross-linking (ACXL) method. Patients underwent ACXL at the Dept. of Ophthalmology of University Hospital in Hradec Králové between 2012 - 2013. Uncorrected distance visual acuity, best corrected distance visual acuity, keratometry (K1, K2, Kmax), corneal astigmatism and corneal pachymetry were measured preoperatively and in 6 months, 1year, 2 and 3 years after the surgery. The results were statistically analysed by non-parametric Wilcoxon test. There were found statistically significant changes in K2 values and values of corneal thickness postoperatively.Key words: keratoconus, ectasia, accelerated corneal cross-linking.

[Severe Eyeball and Facial Skeletal Injuries Caused by Firefighting Sport]

The aim of this work is to draw attention to possible injuries of the eye and the facial skeleton caused by firefighting sport. There was a group of 9 patients presented who were treated from 2006 to 2015 in the Department of Ophthalmology at the University Hospital in Pilsen and diagnosed with severe eyeball contusion after being hit by a jet of water and/or a water pipe. Three cases are presented in detail.

[Cross-Linking in Keratoconus: "Epi-off" or "Epi-on"?]

Corneal cross-linking can halt the progression of keratoconus, but what is the best approach for treatment? There are a number of treatment options for keratoconus, but only corneal cross-linking (CXL) appears to halt the progression of the disease. To guarantee effective cross-linking, CXL treatment involves removal of the corneal epithelium prior to riboflavin application and ultraviolet light illumination - "epi-off" CXL. Several methods of "epi-on" (transepithelial) CXL have been proposed, such as keeping the corneal epithelium intact which should be less painful and help avoid other CXL-associated adverse events. The evidence so far is that epi-off CXL remains the most effective method of strengthening the cornea and slowing keratoconus progression - but transepithelial methods are gaining ground.

Corneal collagen crosslinking with riboflavin and ultraviolet-A light in progressive keratoconus: ten-year results

PURPOSE

To analyze the 10-year results of corneal collagen crosslinking (CXL) for keratoconus.

SETTING

Department of Ophthalmology, University Hospital, Dresden, Germany.

DESIGN

Retrospective interventional case series.

METHODS

The study included eyes treated for progressive keratoconus from 2000 to 2004. Corneal collagen crosslinking was performed by applying riboflavin and ultraviolet-A. The corrected distance visual acuity (CDVA), corneal topography, and endothelial cell count (ECC) were recorded preoperatively and 10 years postoperatively.

RESULTS

The study enrolled 24 patients (34 eyes). The mean age of the 18 men and 6 women was 28.4 years ± 7.3 (SD) and the mean follow-up, 131.9 ± 20.1 months. The mean apical keratometry (K) value was 61.5 diopters (D) preoperatively and 55.3 D 10 years postoperatively; the decrease was statistically significant (P<.001). The mean values for maximum K (53.2 D and 49.56 D, respectively) and minimum K (47.5 D and 45.5 D, respectively) were also significantly lower (P<.001). The preoperative and postoperative CDVA were statistically significantly different (P=.002). The mean CDVA improved by 0.14 logMAR over preoperatively; the change was statistically significant (P=.002). The ECC was unchanged.

CONCLUSIONS

Corneal CXL was effective in treating progressive keratoconus, achieving long-term stabilization of the condition. It was easy to perform, had a good safety profile, and reduced the need for corneal transplantation.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

[Corneal collagen cross-linking with riboflavin and ultraviolet-A light in progressive keratoconus. Results after 10-year follow-up]

PURPOSE

Riboflavin and ultraviolet-A induced cross-linking (CXL) is a promising therapeutic option to halt the progression of keratoconus. The aim of the study was to prove a long-term stabilizing effect of riboflavin and ultraviolet-A induced collagen CXL in young and otherwise healthy patients with progressive keratoconus and a corneal thickness of at least 400 μm on average 10 years after treatment.

METHODS

Corneal CXL was performed after removing epithelial tissue by instilling riboflavin 0.1% solution for 30 min before and during 30 min of ultraviolet-A irradiation (370 nm, 3 mW/cm(2)). This long-term retrospective study included 30 eyes of 20 patients with progressive keratoconus. Preoperative and postoperative examinations on average 10 years after treatment included best corrected visual acuity (BCVA), corneal topography (keratometry values KMAX, KMIN and KApex), corneal thickness (CT) and if available endothelial cell density.

RESULTS

The mean preoperative age was 28 ± 7 years (range 14-42 years), 4 patients were female (7 eyes) and 16 patients (23 eyes) were male. Preoperatively, the mean K-value on the apex of keratoconus was 62 ± 13.2 dpt which showed a statistically significant reduction after 10 years to 55 ± 8.1 dpt (p = 0.001). The mean KMAX (53 ± 8.2 versus 49 ± 6.6 dpt) and KMIN values (48 ± 5.5 vs. 45 ± 5.1 dpt) also showed a statistically significant decrease (p = 0.001). In comparison BCVA also showed a statistically significant preoperative and postoperative difference (p = 0.005). There was a significant improvement of BCVA by a mean of - 0.13 ± 0.25 logMAR. The mean change in corneal thickness at the 10-year follow up was 46 μm (p = 0.001). Bias possibly occurred because of a change of the measurement method from ultrasound pachymetry to optical pachymetry with Oculus Pentacam®. Neither corneal endothelium nor deeper structures suffered any damage. Only two patients had continuous progression of keratoconus and needed a reapplication of CXL.

CONCLUSION

The results of this study indicate that riboflavin and ultraviolet-A induced corneal CXL is a promising therapeutic option for progressing keratoconus to obtain long-term stabilization. There was a sustained improvement of all K-values and BCVA 10 years after treatment and CXL is minimally invasive and easy to handle. Side effects, such as endothelial damage did not occur.

First identification of a triple corneal dystrophy association: keratoconus, epithelial basement membrane corneal dystrophy and fuchs' endothelial corneal dystrophy

Purpose

To report the observation of a triple corneal dystrophy association consisting of keratoconus (KC), epithelial basement membrane corneal dystrophy (EBMCD) and Fuchs’ endothelial corneal dystrophy (FECD).

Methods

A 55-year-old male patient was referred to our cornea service for blurred vision and recurrent foreign body sensation. He reported bilateral recurrent corneal erosions with diurnal visual fluctuations. He underwent corneal biomicroscopy, Scheimpflug tomography, in vivo HRT confocal laser scanning microscopy and genetic testing for TGFBI and ZEB1 mutations using direct DNA sequencing.

Results

Biomicroscopic examination revealed the presence of subepithelial central and paracentral corneal opacities. The endothelium showed a bilateral flecked appearance, and the posterior corneal curvature suggested a possible concomitant ectatic disorder. Corneal tomography confirmed the presence of a stage II KC in both eyes. In vivo confocal laser scanning microscopy revealed a concomitant bilateral EBMCD with hyperreflective deposits in basal epithelial cells, subbasal Bowman's layer microfolds and ridges with truncated subbasal nerves as pseudodendritic elements. Stromal analysis revealed honeycomb edematous areas, and the endothelium showed a strawberry surface configuration typical of FECD. The genetic analysis resulted negative for TGFBI mutations and positive for a heterozygous mutation in exon 7 of the gene ZEB1.

Conclusion

This is the first case reported in the literature in which KC, EBMCD and FECD are present in the same patient and associated with ZEB1 gene mutation. The triple association was previously established by means of morphological analysis of the cornea using corneal Scheimpflug tomography and in vivo HRT II confocal laser scanning microscopy.

Corneal crosslinking with riboflavin and ultraviolet A. Part II. Clinical indications and results

Changes in the biomechanical properties of the human cornea play an important role in the pathogenesis of corneal ectatic diseases. A variety of conditions in primary acquired (keratoconus and pellucid marginal degeneration) or secondary induced (iatrogenic keratectasia after excimer refractive laser surgery) corneal ectatic disorders lead to reduced biomechanical resistance. Corneal collagen crosslinking (CXL) has emerged as a promising technique to slow or even to stop the progression of these corneal ectatic pathologies. In this procedure, riboflavin (vitamin B2) is administered in conjunction with ultraviolet A light (UVA, 365 nm). This interaction causes the formation of reactive oxygen species, leading to the formation of additional covalent bonds between collagen molecules, with consequent biomechanical stiffening of the cornea. Although this method is not yet accepted as an evidence-based medicine modality for the treatment of corneal primary or secondary ectasias, the results of prospective, randomized studies of CXL used in the treatment of these pathologic entities show significant changes in the properties of corneal tissue. This procedure is currently the only etiopathogenetic approach in ectatic eyes that can delay or stop the process of cornea destabilization, reducing the necessity for keratoplasty. Despite promising results, CXL is associated with issues that include long-term safety and duration of the stabilizing effect. Combination of CXL with vision-improving procedures, such as topography-guided custom ablation and implantation of intracorneal ring segments of phakic intraocular lenses, may expand the indications for this procedure.

Corneal crosslinking with riboflavin and ultraviolet A. I. Principles

Changes in the biomechanical properties of the human cornea play an important role in the pathogenesis of corneal ectatic diseases. Biomechanical investigation shows significant differences between human ectatic corneas and normal corneas, including decreased stiffness and reduction of collagen crosslinks in the ectatic cornea. Induction of crosslinks is a well-established procedure in polymer chemistry to increase the elastic modulus of materials. Crosslinking (CXL) in connective tissue can occur during aging and as a side effect of diabetes mellitus. CXL has been used medically to increase stability and reduce the biodegradation of collagen-based biomaterials for bioprostheses. CXL of the cornea using riboflavin and UVA light with a wavelength of 370 nm and a dosage of 5.4 J/cm² is a new approach that increases the mechanical and biochemical stability of stromal tissue. This technique combines the principles of CXL (chemical and nonenzymatic) and the biochemical mechanisms of photo-oxidative CXL with riboflavin as a photosensitizer. In this review, the enrichment of riboflavin in the stroma by standard (epi-off) and transepithelial (epi-on) CXL is discussed. The theoretical and experimental measurements of the absorption of UV light explain the stronger CXL effect in the anterior stroma and its importance for the prevention of damage to the endothelial cells. UV devices are described. Changes of the physical properties after CXL, as well as the cellular changes, are discussed. From these basic investigations, treatment parameters for effective and safe CXL are identified.

Riboflavin osmolar modification for transepithelial corneal cross-linking

PURPOSE

To investigate the influence of osmolarity on the transepithelial permeability of riboflavin solutions in a cross-linking procedure.

METHODS

Several riboflavin 0.1% solutions that contained different NaCl and benzalkonium chloride (BAC) concentrations were applied to 36 rabbit eyes for 30 min. To serve as a control, the epithelium was removed in group A (standard protocol). The groups then received the following solutions: (A) riboflavin 0.1% in NaCl 0.9% solution; (B) riboflavin 0.1% in NaCl 0.44% solution with BAC 0.02%; (C) riboflavin 0.1% in NaCl 0.44% solution with BAC 0.01%; (D) riboflavin 0.1% in NaCl 0.44% solution without BAC; (E) riboflavin 0.1% in NaCl 0.9% solution with BAC 0.02%; and (F) riboflavin 0.1% in NaCl 0.9% solution without BAC. Six eyes in each group were treated. The absorption coefficients of the corneas were measured to characterize the riboflavin penetration into the cornea.

RESULTS

There is a large difference in the transepithelial riboflavin penetration of riboflavin 0.1% + BAC 0.02% solutions that contain different NaCl concentrations (NaCl 0.9% versus NaCl 0.44%). The absorption coefficients differed by more than a factor of two (P = 0.004). No statistically significant difference was found between riboflavin 0.1% in NaCl 0.44% solution containing BAC 0.02% and BAC 0.01%. Compared to the standard protocol, these solutions resulted in an absorption coefficient of 37% (BAC 0.02%) and 33% (BAC 0.01%) of the standard epithelium-off procedure.

CONCLUSION

The transepithelial riboflavin solution should contain no dextran, but it should include 0.01% BAC and 0.44% NaCl to promote the permeability of riboflavin through the epithelium, resulting in a sufficient concentration of riboflavin in the corneal stroma.

[Bilateral visual loss in a young male patient]

We present the case of a 36-year-old male patient who presented with an increasing bilateral loss of vision which had existed for several years. Slit-lamp examination revealed a conical anterior protusion of the lens and funduscopy showed a discreet perimacular dot and fleck retinopathy. In consideration of all clinical findings the patient was diagnosed with anterior lenticonus as an ocular manifestation of an Alport's syndrome which is a rare X-linked disease. Besides renal failure and hearing loss which occur early, ocular changes usually manifest later on. Patients with a anterior lenticonus can be effectively treated with phacoemulsification and intraocular lens implantation. The visual outcome after surgery is excellent.

Hydrogel probe for iontophoresis drug delivery to the eye

The aim of this study was to evaluate the use of a solid hydrogel loaded with a drug solution as a probe for ejecting drugs to the eye upon application of low current iontophoresis. Hydroxyethyl methacrylate (HEMA), cross-linked with ethylene glycol dimethacrylate (EGDMA), and cross-linked arabinogalactan or dextran were prepared to form solid hydrogels. The hydrogels were examined for their mechanical suitability, absorption of drug solution and in vitro release properties when applying an iontophoretic current through the drug-loaded hydrogel into a solid-agar surface. Transconjunctival and transscleral iontophoresis of gentamicin sulfate was studied in healthy rabbits using drug-loaded disposable HEMA hydrogel disc probes. Gentamicin concentrations in different eye segments were assayed using a fluorescence polarization immunoassay. Preliminary corneal toxicity was examined in rabbits using a current intensity of 2.5 and 5.1 mA/cm2 for 60 and 120 s. The most appropriate hydrogel is composed of HEMA, 2% EGDMA and 75% water. lontophoresis onto agar gel was found indicative for the evaluation of iontophoretic activity of a hydrogel. Transscleral iontophoretic treatment resulted in high concentrations of drugs in the posterior segments of the eye. Application of iontophoresis onto the rabbit eye caused a reversible swelling of the cornea which lasted a few hours after application. Low current iontophoresis using drug-loaded hydrogel has a potential clinical value in obtaining high drug concentration at posterior segments of the eye.

Corneal cross-linking with hypo-osmolar riboflavin solution in thin keratoconic corneas

PURPOSE

To evaluate the 1-year results of keratoconic eyes with thin corneas that were treated by a hypo-osmolar riboflavin solution and ultraviolet A collagen cross-linking (CXL).

DESIGN

Retrospective, nonrandomized study.

METHODS

setting: Department of Ophthalmology, Carl Gustav Carus University Hospital, Dresden, Germany. study population: Thirty-two eyes of 29 patients with progressive keratoconus and a corneal thickness of less than 400 μm (without the epithelium). intervention: Application of a hypo-osmolar riboflavin solution to the cornea after its de-epithelization followed by ultraviolet A collagen cross-linking. main outcome measures: Thirty-two eyes with a follow-up within 1 year were evaluated before and after the procedure. Examinations comprised an evaluation of visual acuity, corneal topography, slit-lamp microscopy, and corneal thickness measurements.

RESULTS

Before surgery, the mean corneal thickness (with the epithelium) was 382.3 ± 41.9 μm, and after the removal of epithelium, the thickness of the cornea was reduced to 337.0 ± 51.9 μm. After the application of the hypo-osmolar riboflavin solution, this value increased to 451.8 ± 46.7 μm. Before surgery, the mean K-value of the apex of the keratoconus was 65.6 ± 11.2 diopters, and 1 year after treatment, this value remained unchanged at 64.9 ± 11.0 diopters (P = .839). Mean best-corrected visual acuity at the time of the treatment was 0.63 ± 0.37 logarithm of the minimal angle of resolution, and 1 year after the treatment, this value was not statistically different (0.59 ± 0.42 logarithm of the minimal angle of resolution; P = .662). At the last follow-up examination, which was 1 year after the procedure, all corneas were transparent, without any scarring lesions in the stroma.

CONCLUSIONS

The results of our study, using hypo-osmolar riboflavin solution in a cross-linking procedure of thin corneas, show a stability of keratoconus one year after cross-linking. Application of the hypo-osmolar riboflavin solution preserved cross-linked corneas from developing stromal scars.

Corneal cross-linking and safety issues

Purpose:

To compile the safety aspects of the corneal collagen cross-linking (CXL) by means of the riboflavin/UVA (370 nm) approach.

Materials and Methodology:

Analysis of the current treatment protocol with respect to safety during CXL.

Results:

The currently used UVA dose density of 5.4 J/cm² and the corresponding irradiance of 3 mW/cm² are below the known damage thresholds of UVA for the corneal endothelium, lens, and retina. Regarding the photochemical damages due to the free radicals the damage threshold for endothelial cells is 0.35 mW/cm². In a 400μm thick corneal stroma saturated with riboflavin, the irradiance at the endothelial level is about 0.18 mW/cm², which is a factor of 2 smaller than the damage threshold.

Conclusion:

As long as the corneal stroma treated has a minimal thickness of 400 microns (as recommended), neither corneal endothelium nor deeper structures such as lens and retina will suffer any damages. The light source should provide a homogenous irradiance avoiding hot spots.

Detection of biomechanical changes after corneal cross-linking using Ocular Response Analyzer software

PURPOSE

To investigate biomechanical changes after corneal cross-linking (CXL) with riboflavin/ultraviolet-A (UVA) in keratoconus using the recently developed Ocular Response Analyzer (ORA, Reichert Technologies) software.

METHODS

Through use of the new ORA software (version 2.04), 37 new parameters derived from the best measurement signal with the highest wavescore of 4 measurements from 50 eyes of 46 patients with keratoconus were obtained before and 1 year after CXL. The parameters of 96 eyes from 96 age-matched, healthy individuals with a spherical equivalent refraction <3.00 diopters served as controls.

RESULTS

Corneal hysteresis (CH) and corneal resistance factor (CRF) before CXL were 7.38±1.42 mmHg and 6.16±1.42 mmHg, respectively, compared to 7.37±1.26 mmHg (P=.971) and 6.16±1.50 mmHg after CXL (P=.997), respectively. Based on these 37 new parameters, the area under peak 2 (p2area) showed a statistically significant increase from 1262.3±623.1 before CXL to 1704.3±732.3 1 year after CXL (35%; P=.001). The related value for the p2area of the healthy control group was 3374.9±1099.9. A significant negative correlation was observed between the p2area and the difference in CH-CRF values (r=-0.29, P=.001).

CONCLUSIONS

The area under peak 2 appears to be a more sensitive parameter to detect biomechanical changes after CXL than CH or CRF alone. After CXL, keratoconic corneas display altered biomechanical properties, which remain different to those observed in healthy corneas.

Permanent corneal haze after riboflavin-UVA-induced cross-linking in keratoconus

PURPOSE

Retrospective evaluation of haze development after riboflavin-ultraviolet (UV) A-induced corneal collagen cross-linking (CXL).

METHODS

One hundred sixty-three eyes of 127 patients with stage 1-3 keratoconus according to Krumeich's classification were included in this retrospective analysis. Follow-up was 1 year. Preoperatively and at all follow-up examinations uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), slit-lamp microscopic findings, corneal topography, and corneal thickness were recorded.

RESULTS

At 1 year after CXL, 149 (91.4%) eyes of 114 patients had a clear cornea without stromal haze (control group), whereas 14 eyes (8.6%) of 13 patients developed clinically significant stromal haze (haze group). Preoperatively, the mean keratometry (K) value of the apex was 62.1+/-13.8 diopters (D) in the control group and 71.1+/-13.2 D in the haze group (P=.02). The mean corneal thickness before the procedure was 478.1+/-52.4 mum in the control group and 420.0+/-33.9 mum in the haze group (P=.001). Uncorrected visual acuity and BSCVA, which were similar between groups preoperatively (P=.59 and P=.75, respectively), were improved in the control group (P=.023 and P=.001, respectively), but reduced in the haze group (P=.012 and P=.004, respectively) postoperatively.

CONCLUSIONS

The parameters defining the stage of keratoconus, such as K-value and corneal thickness, could be considered predicting factors for possible development of corneal haze after riboflavin-UVA-induced CXL. Advanced keratoconus should be considered at higher risk of haze development after CXL due to low corneal thickness and high corneal curvature.

Early Transient Visual Acuity Loss After LASIK Due to Steroid-induced Elevation of Intraocular Pressure

PURPOSE

To report the clinical course of early transient reduction of uncorrected visual acuity (UCVA) after LASIK surgery resulting from steroid-induced elevation of intraocular pressure (IOP).

METHODS

Twenty-nine eyes of 15 patients who received topical corticosteroids after uneventful myopic LASIK surgery and had a decrease in UCVA within the first 3 weeks were evaluated retrospectively.

RESULTS

Intraocular pressure increased by 4 to 30 mmHg from preoperative to postoperative days 4 to 20. Twenty-seven of 29 eyes had a decrease in UCVA and/or best spectacle-corrected visual acuity (BSCVA). All eyes, except one, had edema without evidence of inflammation in the interface or the remainder of the cornea. Discontinuation of topical corticosteroids and application of anti-glaucoma medications resulted in a decrease of IOP to normal levels, reduction or disappearance of the edema, and recovery of BSCVA.

CONCLUSIONS

Early onset steroid-induced elevation of IOP after LASIK may cause corneal edema and a sudden decrease in UCVA. Rapid diagnosis and treatment can control IOP and recover the visual loss.