Photorefractive Intrastromal Corneal Crosslinking as a Treatment for Low Grade Myopia

Myopia Clinical Trial

Official title:

Comparison of a 4-mm Ring Shaped and 3.5-mm Ring Shaped PiXL Protocol for Low Grade Myopia

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT03987880
• Other study ID #: PiXLMYOP-II
• Status: Completed
• Phase: N/A
• Start date: January 22, 2018
• Est. completion date: October 15, 2020

Study information

• Verified date: December 2020
• Source: Umeå University
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

To assess the improvement in refractive error and the corneal endothelial safety with a customized corneal crosslinking treatment regimen for low grade myopia. The study compares two treatment protocols, a 4.0-mm central ring-shaped zone with a 3.5-mm central ring-shaped zone in high oxygen environment without corneal epithelial debridement.

Description:

The study design is a prospective, single-masked intraindividually comparing randomized controlled trial, conducted at the Department of Clinical Sciences / Ophthalmology, Umeå University Hospital, Umeå, Sweden. The study includes healthy men and women with low grade myopia, aged between 18-35 years and involves 27 participants with a myopia of -0.5 to -2.5 diopters (D) and astigmatism of ≤0.75D. All participants are treated with phototherapeutic intrastromal corneal collagen cross-linking (PiXL) without epithelial debridement (epi-on), after topical riboflavin. Both eyes are treated and randomized to receive ultraviolet (UV) light according to PiXL 4.0 mm treatment zone in one eye and PiXL 3.5 mm treatment zone in the other, which is masked to the participant. For myopia <0.75D, 10 J/cm^2 is used and for higher levels of myopia 15J/cm^2 is used. Throughout the treatment, humidified oxygen is continuously delivered around the eye using an oxygen mask to achieve an oxygen concentration of ≥95 percentage. All participants are informed about the procedures and provide oral and written consent before inclusion in the study. At baseline, each eye is examined with slit-lamp microscopy, subjective refraction, determination of uncorrected (UCVA), low contrast visual acuity at 2.5 percentage and 10 percentage contrast and best corrected (BSCVA) visual acuities using the LogMAR fast protocol and intraocular pressure (IOP) using Goldmann applanation tonometry. Under standardized, mesopic light conditions each eye is evaluated by keratometry readings, central corneal thickness and after treatment also the depth of demarcation lines, extracted from Schemipflug camera measurements, Pentacam HR® (Oculus, Inc. Lynnwood, WA). Central corneal endothelial photographs are taken with the Topcon SP-2000P specular microscope (Topcon Europe B.V., Capelle a/d Ijssel, the Netherlands), from which the corneal endothelial cell count is manually calculated from a cluster of 25 cells from each photograph. Total ocular wavefront is measured with iTrace (Tracey Technologies, Inc.). All the above mentioned examinations are reassessed at 1, 3 and 6 and 12 months after treatment. At 1 day and 1 week after treatment, solely UCVA, Auto refractor measurements, slit-lamp examination and a subjective comparison of discomfort and visual performance in each eye are evaluated.

Recruitment information / eligibility

• Status: Completed
• Enrollment: 27
• Est. completion date: October 15, 2020
• Est. primary completion date: October 15, 2020
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 18 Years to 35 Years

Eligibility

Inclusion Criteria:

Spherical equivalent on distance subjective refraction between -0.50D and -2.50D.

• Astigmatism = 0.75D
• Stable myopia. Maximum change in refraction of 0.50D in the last 2 years.
• Best corrected visual acuity of at least 0.00 logMAR (ETDRS chart).
• Thinnest pachymetry reading = 440 µm.
• No previous ocular surgery.
• No cognitive insufficiency interfering with the informed consent.

Exclusion Criteria:

• History of or current condition, disease, surgery or medication with ocular effects that could affect the outcomes of the treatment.
• Allergy to any substance or device used in the study.
• Cognitive insufficiency interfering with the informed consent.

Related Conditions & MeSH terms

• Corneal Crosslinking
• Eye Diseases
• Myopia
• Refractive Errors

Intervention

Procedure:
• 4.0 mm treatment
PiXL treatment with UV irradiation in a central 4.0-mm ring-shaped zone of the cornea.
• 3.5 mm treatment
PiXL treatment with UV irradiation in a central 3.5-mm ring-shaped zone of the cornea.

Locations

Country	Name	City	State
Sweden	Department of Clinical Sciences/Ophthalmology, Umeå University	Umeå

Sponsors (2)

Lead Sponsor	Collaborator
Umeå University	Avedro, Inc.

Country where clinical trial is conducted

Sweden, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Change from baseline in uncorrected visual acuity	Change from baseline in distance uncorrected visual acuity	1, 3, 6, 12 and 24 months after treatment
Primary	Change from baseline in spherical equivalent	Change from baseline in spherical equivalent on subjective distance refraction	1, 3, 6, 12 and 24 months after treatment
Secondary	Change from baseline in corneal endothelial cell density	Change from baseline in central corneal endothelial cell density	12 and 24 months after treatment
Secondary	Change from baseline in best corrected visual acuity	Change from baseline in best spectacle corrected distance visual acuity	1, 3, 6, 12 and 24 months after treatment