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Initial results from mechanical compression of the cornea during crosslinking for keratoconus
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: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 92, no 7, 644-649 p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014. Vol. 92, no 7, 644-649 p.
Keyword [en]
cornea, corneal crosslinking, keratoconus, refractive errors
National Category
Ophthalmology
Identifiers
URN: urn:nbn:se:umu:diva-97010DOI: 10.1111/aos.12380ISI: 000344162700028PubMedID: 24628999OAI: oai:DiVA.org:umu-97010DiVA: diva2:769544
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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