Clinical trial NCT04663048: PiXL as a Treatment for Low Grade Myopia
Official title: Evaluation of a Reduced Photorefractive Intrastromal Corneal Crosslinking Illumination Protocol. A Randomized Controlled Trial.
Study type: INTERVENTIONAL
Overall status: ACTIVE_NOT_RECRUITING
Phase: NA
Conditions: Myopia
Refractive Errors
Keywords: Corneal Crosslinking
Lead sponsor: Umeå University
Sponsor class: OTHER
Collaborators: name: Glaukos Corporation
First posted: 2020-12-10
Enrollment: 26
Sex: ALL
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: TREATMENT

Brief summary: To assess the improvement in myopia with phototherapeutic intrastromal corneal collagen cross-linking (PiXL) without epithelial debridement (epi-on) in high oxygen environment for low grade myopia. The study compares two 3.5-mm central ring-shaped zone protocols; 10 min illumination time vs 16:40 min illumination time.

Detailed 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 25 participants with a myopia of -0.50 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 Protocol A in one eye and PiXL Protocol B in the other, which is masked to the participant. Throughout the treatment, humidified oxygen is continuously delivered around the eye using an oxygen mask to achieve an oxygen concentration of ≥95 percentage. Prior to inclusion all participants are informed about the procedures and provide oral and written informed consent.

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, 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.

Eligibility criteria: 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

Primary outcomes:
measure: Uncorrected distance visual acuity (UDVA)
timeFrame: 1, 3, 6 and 12 months after treatment.
measure: Manifest Refractive Spherical Equivalent
timeFrame: 1, 3, 6 and 12 months after treatment
Secondary outcomes:
measure: Best spectacle corrected visual acuity (BSCVA)
timeFrame: 1, 3, 6 and 12 months after treatment
measure: Endothelial cell density (ECC)
timeFrame: 1, 3, 6 and 12 months after treatment
measure: Low contrast visual acuity at 10% and 2.5% (LCVA)
timeFrame: 1, 3, 6 and 12 months after treatment
Other outcomes:
Locations:
city: Umeå
country: Sweden
facility: Umeå University Hospital
Study officials:
affiliation: Umeå University Hospital
name: Anders Behndig, MD, PhD
role: PRINCIPAL_INVESTIGATOR
References: