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Treatment effect with 2 photorefractive intrastromal cross-linking protocols in low-grade myopia through 24-month follow-up
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.ORCID iD: 0000-0002-1855-3207
Umeå University, Faculty of Medicine, Department of Clinical Sciences, Ophthalmology.ORCID iD: 0000-0002-8456-8036
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 Nursing.
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2021 (English)In: Acta Ophthalmologica, ISSN 1755-375X, E-ISSN 1755-3768, Vol. 99, no 5, p. 519-526Article in journal (Refereed) Published
Abstract [en]

Purpose: To assess the effect of two high-oxygen epi-on PiXL treatments for low-grade myopia.

Methods: This prospective, randomized, intra-individually comparing, single-masked study included 23 healthy volunteers (46 eyes) aged 18-35 years with mild myopia, -0.75 to -2.50 D manifest refractive spherical equivalent (MRSE). One eye was randomized to a 4.0-mm homogenous treatment zone and the fellow eye to a 4.0-mm annular zone (16:40 min at 30 mW/cm(2), fluence 15 J/cm(2)). Uncorrected distance visual acuity (UDVA), MRSE, best spectacle-corrected visual acuity (BSCVA), Scheimpflug light scattering depths, mean keratometry (K-mean) and endothelial cell count (ECC) were assessed through 24 months.

Results: Similar improvements in UDVA were seen for the homogeneous and annular protocols at 1 month: -0.52 (-0.59, -0.39) and -0.49 (-0.59, -0.39) logMAR, respectively (medians and interquartile ranges, IQR), p = 0.91, and MRSE: +1.0 D (0.94, 1.31) and +1.0 D (0.69, 1.25), p = 0.17. Light scattering depths were 496 (465, 527) and 349 (247, 378) mu m, respectively, and the reduction in mean keratometry was -0.8 D (-1.1, -0.7) and 0 D (-0.1, 0.1), p < 0.001. The treatment effect remained stable throughout 24 months. At 1 week, the participants reported less ocular discomfort with the annular protocol. No reductions were seen in BSCVA or ECC. No adverse events were reported.

Conclusion: PiXL can reduce low-grade myopia and improve uncorrected vision in healthy eyes. The initial ocular discomfort may be reduced with an annular treatment zone. Further studies are needed to optimize PiXL treatment parameters.

Place, publisher, year, edition, pages
John Wiley & Sons, 2021. Vol. 99, no 5, p. 519-526
Keywords [en]
Myopia, corneal collagen cross-linking, refractive cross-linking, PiXL
National Category
Occupational Therapy Nursing Ophthalmology
Identifiers
URN: urn:nbn:se:umu:diva-177733DOI: 10.1111/aos.14669ISI: 000589575600001PubMedID: 33196146Scopus ID: 2-s2.0-85096693590OAI: oai:DiVA.org:umu-177733DiVA, id: diva2:1511352
Available from: 2020-12-18 Created: 2020-12-18 Last updated: 2024-11-11Bibliographically approved
In thesis
1. Advanced crosslinking for keratoconus and low-grade myopia
Open this publication in new window or tab >>Advanced crosslinking for keratoconus and low-grade myopia
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Avancerad crosslinking för keratokonus och låggradig myopi
Abstract [en]

Corneal crosslinking (CXL) is an established treatment for progressive keratoconus (KC). In this thesis, Advanced CXL refers to a further development of conventional CXL, which aims to improve the treatment outcomes in KC and can also be used as a refractive treatment for low-grade myopia (near-sightedness). Transepithelial (epi-on) CXL with high oxygen has emerged as an approach to reduce the post-treatment inconveniences. The aim of the three prospective, randomized, intra-individually compared, single-masked studies in this thesis was to continue developing advanced CXL for KC and low-grade myopia.

Studies I and II sought to assess the treatment effects and subjective ocular discomforts in epi-on photorefractive intrastromal crosslinking (PiXL) in high oxygen as a refractive treatment for low-grade myopia using three different illumination protocols. In Study I, 23 healthy subjects (46 eyes) were randomized to a central 4.0 mm homogeneous illumination zone (area) in one eye and a 4.0 mm annular zone with a central 2.0 mm sparing (ring) in the fellow eye. Both protocols improved uncorrected distance visual acuity (UDVA) and manifest refractive spherical equivalent (MRSE) at 1 month, which remained stable throughout 24 months. The ring protocol was reported to cause less ocular discomfort at 1 week. In Study II, 27 healthy subjects (54 eyes) were randomized to the previous ring protocol in one eye and a 3.5 mm annular protocol with a central 1.5 mm sparing (small ring) in the fellow eye. The small ring rendered less ocular discomfort the first day post-treatment and slightly better improvements in UDVA and MRSE, but there was a transient reduction in low-contrast visual acuity (LCVA). In both Studies I and II, no changes in endothelial cell count (ECC) and best corrected visual acuity (BCVA) were seen and no adverse events were registered.

Study III aimed to compare the treatment effect and subjective ocular discomfort scores of customized topography-guided epi-on CXL in high oxygen with customized topography-guided epi-off CXL in room air for KC. At 24 months, both treatments had halted the disease progressions and had improved UDVA and BCVA. LCVA at 10% contrast improved for both protocols, but LCVA at 2.5% contrast improved for epi-on CXL only. No changes were seen in ECC, and no adverse events were registered. The epi-on eyes were reported to have less ocular discomfort throughout the first week post-treatment.

In conclusion, advanced CXL can be used to improve vision and halt progressive KC, and it also improves uncorrected vision and reduces low-grade myopia in healthy eyes. In low-grade myopia, the initial ocular discomfort may be reduced with a ring illumination PiXL protocol. A larger treatment effect may be seen with a smaller treatment zone, but likely at the expense of a transient decrease in LCVA. In KC, customized topography-guided epi-on CXL in high oxygen is a viable alternative to customized topography-guided epi-off CXL in room air, with faster improvements in BCVA and LCVA and less early ocular discomfort.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2024. p. 85
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 2328
Keywords
Keratoconus, Myopia, Corneal Cross-linking, Transepithelial CXL, Oxygen, Topography-guided CXL, Visual acuity, Corneal topography
National Category
Ophthalmology
Research subject
ophthalmology
Identifiers
urn:nbn:se:umu:diva-231668 (URN)9789180705134 (ISBN)9789180705141 (ISBN)
Public defence
2024-12-06, Hörsal B, målpunkt 1D T9, Norrlands universitetssjukhus, Umeå, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2024-11-15 Created: 2024-11-11 Last updated: 2024-11-12Bibliographically approved

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Näslund, SofieFredriksson, AnneliBeckman Rehnman, JeannetteBehndig, Anders

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