2021 ASCRS Annual Meeting

Authors

Presenting Author
Eric D. Rosenberg, DO, MSE    Email the author
Authors
Alanna S. Nattis, DO

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Paper Abstract

Purpose
There is no standard post-crosslinking (CXL) regimen for pain and inflammation. In addition to topical steroid, some surgeons prescribe oral narcotics due to severe pain that may occur. This study compared post-CXL pain scores between patients receiving a tapered topical steroid over 1-month post-CXL vs. an intracanalicular dexamethasone insert.

Methods
This prospective, randomized study investigated the efficacy of a dexamethasone intracanalicular insert on post-CXL inflammation and pain in keratoconus patients. Ten patients (20 eyes) were enrolled; 50% were randomized into a post-CXL 28-day topical tapering steroid regimen vs. 50% randomized into the intracanalicular insert group. All patients were evaluated for pain scores following standard bilateral epithelium-off CXL on postoperative day(POD) 1, POD-3, POD4-7, postoperative week (POW)-1, POW2, POW3 and POW4. Rate of re-epithelialization, need for ‘rescue’ pain medication, and ease of postoperative regimen was assessed between groups.

Results
10 patients (20 eyes) underwent epithelium-off bilateral CXL for progressive keratoconus. 5 patients were randomized to receive prednisolone eye drops on a tapering schedule post-procedure; 5 patients received dexamethasone intracanalicular inserts at time of CXL. Pain scores between groups were comparable with no significant difference from date of surgery though POW4. Rate of re-epithelialization was similar between groups; both groups stated no difficulty with postoperative instructions/regimens. There was no significant difference in use of break-through ‘rescue’ pain medication between groups. No patient experienced any adverse results in relation to treatment or CXL.

Conclusion
Our results demonstrate that utilizing a dexamethasone intracanalicular insert at the time of CXL rather than prescribing a month-long tapering dose of prednisolone drops is safe and efficacious. Use of a dexamethasone-eluting insert can help improve compliance with postoperative eye drop instructions and even comfort.

Authors

Presenting Author
Abby Nieuwsma, MD    Email the author
Authors
John P. Berdahl, MD, Daniel C. Terveen, MD, Mitch J. Ibach, OD

Video Presentation

Paper Abstract

Purpose
Corneal cross-linking (CXL) is used to prevent keratectasia or post-LASIK ectasia progression. Recent studies suggest the conventional minimum corneal thickness guideline may be too conservative. By analyzing outcomes at our institution, we hoped to reassure providers that CXL is safe on thin corneas and can be offered to more patients.

Methods
Retrospective chart review of patients with corneal ectasia that had CXL at our institution. Patients were included if their preoperative thinnest point of the cornea was less than 400µm. Demographics recorded included gender, age, related diagnosis, and which eye underwent surgery. 13 females and 21 males ages 16-69 were eligible for the study. Preoperative and post-operative UVA, BCVA, thinnest point of the cornea, K1, K2, and Kmax were recorded. Pentacam data was used to measure corneal thickness and keratometry. Need for penetrating keratoplasty or scleral contacts and cases of endothelial failure were recorded. Patients were analyzed at 3-month and furthest (6-12 month) follow-ups.

Results
37 eyes of 34 patients were included in the study. 18 eyes (47%) had improved visual acuity after 3-months. Kmax decreased an average of 1.1D at 3-months and 3.4D at furthest follow-up (avg. 10.5-months). At the furthest follow-up 77% had less than 1D of steepening. Average thinnest point of cornea was 328µm pre-operatively and 303µm post-operatively. Change in the thinnest point of the cornea after 3-months was not statistically significant. No patients required penetrating keratoplasty. 23 eyes (61%) required scleral contacts. There were no cases of endothelial failure.

Conclusion
Given the average flattening at both follow-up periods and absence of serious adverse events in our study, current minimum corneal thickness guidelines may be too conservative. Consistent with international literature, our real-world study suggests that CXL provides a low-risk and effective alternative to transplant in patients with thin corneas.

Authors

Presenting Author
Mark C. Lobanoff, MD, ABO    Email the author

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Paper Abstract

Purpose
A device has been designed to allow better saturation of the corneal stroma with riboflavin in 1/3 of the time of the traditional Dresden method. In addition, this device allows for the constant supply of oxygen to the cornea while the UVA is being applied. Oxygen concentrations within the stroma play a critical role in the efficacy of CXL.

Methods
The design of the device will be reviewed along with early clinical outcomes. Patients with progressive keratoconus will be treated using the device to apply both riboflavin and oxygen during the cross linking treatment. An Avedro unit will be used to supply the UVA light. Oxygen levels in the cornea and riboflavin levels in the cornea will be measured.

Results
The prototypes show good suction attachment to the eye. Patients report they are comfortable. The riboflavin achieves complete saturation of the corneal stroma at 10 minutes as apposed the the 30 minutes of application required by the traditional Dresden method. The device uses 50% less riboflavin than the Avedro method. We have successfully filled the sealed chamber with 100% oxygen. (Photographs and videos of this will be shown in the talk)

Conclusion
The novel silicone device is showing promise.It increases the efficiency of the CXL procedure, reducing the riboflavin application time by 2/3. It allows 100% oxygen to be maintained above the stroma which should increase stromal oxygen concentrations and in turn improve accelerated crosslinking reactions.

Authors

Presenting Author
Tanner J. Ferguson, MD    Email the author
Authors
Sanjai Jalaj, MD, Srinidhi Singuri, Matthew R Ford, PhD, William J. Dupps Jr., MD, MS, PhD, ABO, Vinicius S. De Stefano, MD, PhD

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Paper Abstract

Purpose
To evaluate depth-dependent changes of corneal biomechanical properties in eyes with keratoconus following corneal cross-linking (CXL) using optical coherence elastography (OCE)

Methods
In a prospective series of eyes with keratoconus (KC), a custom high-speed SS-OCT system was used to image the cornea before and at least 3 months after CXL during an applanating deformation while monitoring applanation force. Cross-correlation was applied to track frame-by-frame 2D OCT speckle displacements, and the slope of force vs. local axial displacement behavior during the deformation was used to produce a map of axial stiffness (k). These values were averaged for anterior (ka) and posterior (kp) stromal regions and expressed as a ratio (ka/kp) to assess depth-dependent differences in stiffness. CXL was performed according to the Dresden protocol with an FDA-approved system.

Results
5 eyes from 5 patients with keratoconus underwent OCE before and after CXL. The mean ka/kp was 1.03 ± 0.05 prior to CXL compared to 1.22 ± 0.15 following the CXL procedure (p <0.001).

Conclusion
As measured with OCE, CXL produces a preferential stiffening of the anterior stroma in eyes with keratoconus compared to baseline. The results of this study support the use of OCE as a tool to evaluate biomechanical changes in the cornea following tissue-altering procedures.

Authors

Presenting Author
Steven A. Greenstein, MD    Email the author
Authors
Steven Huang, OD, John D. Gelles, OD, Peter S. Hersh, MD, FACS

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Paper Abstract

Purpose
Epi-off corneal cross-linking (CXL) has been shown to be a safe and effective intervention to slow progression of keratoconus (KC) and post refractive ectasia (EC). The US phase III pivotal trials followed patients through 12 months. This study aims to report the long term (10-year) outcomes of patients treated as part of the US pivotal trial.

Methods
Patients treated at a single center as part of the US phase III multicenter pivotal trials for CXL were contacted and invited to participate in an additional 10-year follow up exam. LogMar lines (LL) of uncorrected (UCVA) and best corrected (BCVA) visual acuity, maximum keratometry (Kmax), and thinnest pachymetry (Pthin) were evaluated and compared to pre-operative values.

Results
19 patients (29 eyes) agreed to participate and completed the 10-year follow-up visit. 7 eyes were excluded secondary to additional corneal surgical interventions between 1 and 10-year CXL exams. 15 KC & 7 EC eyes were included. There were no significant changes in UCVA, BCVA, Kmax, and Pthin, 10 years after CXL (UCVA 0.05±0.4,p=0.5; BCVA-0.07±0.4,p=0.4; Kmax 0.1±6.4D,p=0.9; Pthin -0.4±37µm, p=0.9). Compared to pre-op measurements, 86.7% KC and 42.9% of EC patients showed less than 2D steepening in KMax as compared to preop measurements. Untreated fellow eyes (n=6) steepened by +7.1±11.9D

Conclusion
CXL-treated KC eyes generally remained stable through 10 years post-op. Although not statistically significant, eyes in the KC cohort showed less progression than EC eyes. Some untreated fellow eyes showed substantial clinical progression, corroborating the long-term advantage of cross-linking in decreasing progression of ectatic corneal disorders.

★ This paper won Best Paper of Session (BPOS) at the 2021 ASCRS Annual Meeting

Authors

Presenting Author
Emilio A. Torres-Netto, MD, PhD    Email the author
Authors
Sabine Kling, PhD, Francesca Gilardoni, MD, Reyhaneh Abrishamchi, MD, Hormoz Abdshahzadeh Sr., MD, Nikki L. Hafezi, MA, Farhad Hafezi, MD, PhD

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Paper Abstract

Purpose
In 2017, we published a new algorithm: rather than modifying corneal thickness, we adapt the total irradiation to every patient’s individual stromal thickness (sub400 protocol). In this prospective study, we analyzed whether CXL with individualized fluence is able to stop keratoconus progression in ultra-thin corneas with a follow-up of 1 year.

Methods
A total of 47 progressive keratoconus (KC) eyes with corneal thicknesses between 214 μm and 398 μm at the time of UV irradiation were enrolled. Following a standardized riboflavin application for 20 minutes, UV irradiation was performed at 3 mW/cm2 with individualized irradiation times. CDVA, manifest refractive sphere, cylinder, Kmax, thinnest corneal thickness and densitometry were evaluated preoperatively, and at 6 and 12 months postoperatively. Corneal demarcation line was assessed with anterior segment OCT at 1 month after surgery. Keratoconus progression was defined as increase of Kmax by >1.0 D within 1 year.

Results
5 of 47 eyes showed progression within 12 months. A significant correlation was found between demarcation line depth and irradiation time (r=+0.423, p=0.003), however not between demarcation line depth and change in Kmax (r=-0.129, p=0.387). On average, there was a significant change from baseline at 12 months in thinnest thickness (-16.8±23.9 μm, p<0.05), in Kmax (-2.15±3.60 D, p<0.05) and in densitometry (+2.00±2.07 GSU, p<0.05). No significant changes were found in CDVA (p=0.471), sphere (p=0.206) and cylinder (p=0.753).

Conclusion
The “sub400” individualized fluence CXL protocol standardizes the treatment in ultra-thin corneas and halted KC progression with a success rate of 89% at 12 months. The sub400 protocol allows treatment of corneas as thin as 215 µm of stroma, extending the clinical range of cases that can be safely cross-linked to far progressed keratoconus stages.

Authors

Presenting Author
Emilio A. Torres-Netto, MD, PhD    Email the author
Authors
Michael W. Belin, MD, ABO, Mark Borgstrom, PhD, Francesca Gilardoni, MD, Hormoz Abdshahzadeh Sr., MD, Joerg Iwanczuk, BEng, Nikki L. Hafezi, MA, Farhad Hafezi, MD, PhD

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Paper Abstract

Purpose
The current ABCD progression display was designed to monitor changes in ectatic disease. Currently, measurements are limited to keratoconic eyes prior to treatment. Progression parameters post-CXL were not established. Here we measured noise of post-CXL eyes and evaluate whether these measurements can serve as progression determinants after CXL.

Methods
Patients from ELZA Institute with a minimum of 9 months post-crosslinking were enrolled. Patients had a preoperative diagnosis of keratoconus, without other comorbidities. All patients discontinued contact lens wear at least one week prior to measurements. Three separate Pentacam measurements were taken, removing the patient from the Pentacam device between each measurement. A minimum of 7.5 mm of corneal coverage and an acceptable Pentacam quality score were required. At the conclusion of enrollment, U12 data files were exported for analysis. Both pooled variance estimates and one-sided confidence intervals were computed using SPSS version 23 and STATA 13 statistical software.

Results
41 eyes of 41 patients (avg age 32.9 (range 11-63)) were enrolled with an average follow-up of 13.5 months (range 9 – 23). The average final “D” from the Belin/Ambrosio Enhanced Ectasia Display was 9.26 ± 4.37 (range 1.12 – 18.91). 80% and 95% one-sided confidence intervals for the “A” variable (anterior radius of curvature) were 0.170 and 0.261 respectively. 80% and 95% one-sided confidence intervals for “B” variable (posterior radius of curvature) were 0.136 and 0.208 and for minimal pachymetry 4.5 and 6.9 respectively. Significant differences in the range of follow-up (9-23 months) were not observed.

Conclusion
Corneal crosslinking (CXL) has had a major impact on the treatment of ectatic disease. However, less is known about the tomographic changes after CXL and what would be considered documentation of continued progression with the possibility of a retreatment. The above parameters allow for analysis of both the pre- and post-crosslinking cornea.