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Increased corneal hysteresis after corneal collagen crosslinking: a study based on applanation resonance technology
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
Umeå University, Faculty of Medicine, Department of Radiation Sciences.ORCID iD: 0000-0003-2055-576X
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.
2014 (English)In: JAMA ophthalmology, ISSN 2168-6165, E-ISSN 2168-6173, Vol. 132, no 12, 1426-1432 p.Article in journal (Refereed) Published
Abstract [en]

Importance: A reliable tool for quantification of the biomechanical status of the cornea in conjunction with corneal collagen crosslinking (CXL) treatment is needed.

Objective: To quantify the biomechanical effects of CXL in vivo.

Design, Setting, and Participants: A prospective, open, case-control study was conducted at the Department of Ophthalmology, Umeå University, Umeå, Sweden. Participants included 28 patients (29 eyes) aged 18 to 28 years with progressive keratoconus and corresponding age- and sex-matched healthy individuals serving as controls. All participants were monitored during a 6-month period between October 13, 2009, and November 5, 2012.

Main Outcomes and Measures: Corneal hysteresis after CXL for keratoconus.

Results: A difference in corneal hysteresis between the control group and the patients with keratoconus was found at baseline, both with an applanation resonance tonometer (ART) and an ocular response analyzer (ORA), at mean (SD) values of -1.09 (1.92) mm Hg (99% CI, -2.26 to 0.07; P = .01) and -2.67 (2.55) mm Hg (99% CI, -4.05 to -1.32; P < .001), respectively. Increased corneal hysteresis was demonstrated with an ART 1 and 6 months after CXL, at 1.2 (2.4) mm Hg (99% CI,-0.1 to 2.5; P = .02) and 1.1 (2.7) mm Hg (99% CI, -0.3 to 2.6; P = .04), respectively, but not with ORA. A decrease in corneal thickness was seen 1 and 6 months after treatment (-24 [26] µm, P < .001; and -11 [21] µm, P = .01, respectively), and a corneal flattening of -0.6 (0.7) diopters was seen at 6 months (P < .001). No significant change in intraocular pressure was identified in patients with keratoconus with any method, except for an increase at 1 month with Goldmann applanation tonometry (P = .005).

Conclusions and Relevance: To our knowledge ART is the first in vivo method able to assess the increased corneal hysteresis after CXL treatment. Given the large-scale use of CXL in modern keratoconus treatment, a tool with this capacity has a great potential value. Refinement of the ART method of measuring and quantifying corneal biomechanical properties will be a subject of further studies.

Place, publisher, year, edition, pages
American Medical Association , 2014. Vol. 132, no 12, 1426-1432 p.
National Category
Ophthalmology
Identifiers
URN: urn:nbn:se:umu:diva-97009DOI: 10.1001/jamaophthalmol.2014.3029ISI: 000346176400008PubMedID: 25171564OAI: oai:DiVA.org:umu-97009DiVA: diva2:769539
Available from: 2014-12-08 Created: 2014-12-08 Last updated: 2017-12-05Bibliographically approved
In thesis
1. New methods to evaluate the effect of conventional and modified crosslinking treatment for keratoconus
Open this publication in new window or tab >>New methods to evaluate the effect of conventional and modified crosslinking treatment for keratoconus
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Today corneal crosslinking with ultraviolet-A photoactivation of riboflavin is an established method to halt the progression of keratoconus. In some cases, when the refractive errors are large and the visual acuity is low, conventional corneal crosslinking may not be sufficient. In these cases it would be desirable with a treatment that both halts the progression and also reduces the refractive errors and improves the quality of vision.

Aims:  The aims of this thesis were to determine whether mechanical compression of the cornea during corneal crosslinking for keratoconus using a sutured rigid contact lens could improve the optical and visual outcomes of the treatment, and also to find methods to evaluate the effect of different corneal crosslinking treatment regimens.

Methods: In a prospective, open, randomized case-control study, 60 eyes of 43 patients with progressive keratoconus, aged 18-28 years, planned for routine corneal crosslinking, and a corresponding age- and sex-matched control group was included. The patients were randomized to conventional corneal crosslinking (CXL; n=30) or corneal crosslinking with mechanical compression of the cornea during the treatment (CRXL; n=30).

Biomicroscopy, autorefractometry, best spectacle corrected visual acuity, axial length measurement, Pentacam® HR Scheimpflug photography, pachymetry, intraocular pressure measurements and corneal biomechanical assessments were performed before treatment (baseline) and at 1 month and 6 months after the treatment.

One of the articles evaluated and compared the optical and visual outcomes between CXL and CRXL, while the other three articles focused on methods to evaluate treatment effects. In Paper I, the corneal light scattering was manually quantified from Scheimpflug images throughout the corneal thickness at 8 measurements points, 0.0 to 3.0 mm from the corneal centre, in patients treated with CXL. In Paper IV the corneal densitometry (light scattering) was measured with the Pentacam® HR software, in 4 circular zones around the corneal apex and at 3 different depths of the corneal stroma, in both CXL and CRXL treated corneas. Paper III quantified the biomechanical effects of CXL in vivo.

Results: Corneal light scattering after CXL showed distinctive spatial and temporal profiles and Applanation Resonance Tonometry (ART) -technology demonstrated an increased corneal hysteresis 1 and 6 months after CXL. When comparing the refractive and structural results after CXL and CRXL, CRXL failed to flatten the cornea, and the treatment did not show any benefits to conventional CXL treatment, some variables even indicated an inferior effect. Accordingly, the increase in corneal densitometry was also less pronounced after CRXL.

Conclusions: Analysis of corneal light scattering/densitometry shows tissue changes at the expected treatment location, and may be a relevant variable in evaluating the crosslinking effect. ART -technology is an in vivo method with the potential to assess the increased corneal hysteresis after CXL treatment. By refining the method, ARTmay become a useful tool in the future. Unfortunately, CRXL does not improve the optical and visual outcomes after corneal crosslinking. Possibly, stronger crosslinking would be necessary to stabilize the cornea in a flattened position.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2015. 57 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1746
Keyword
Keratoconus, crosslinking, light scattering, densitometry, keratometry, hysteresis, intraocular pressure
National Category
Ophthalmology
Research subject
Ophtalmology
Identifiers
urn:nbn:se:umu:diva-110531 (URN)978-91-7601-336-6 (ISBN)
Public defence
2015-11-20, Hörsal 914, Unod B 9, Norrlands universitetssjukhus, Umeå, 09:00 (Swedish)
Opponent
Supervisors
Available from: 2015-10-30 Created: 2015-10-22 Last updated: 2015-10-30Bibliographically approved

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