Photorefractive Intrastromal Corneal Crosslinking as a Treatment for Low Grade Myopia
Condition: Myopia; Corneal Crosslinking; Refractive Errors; Eye Diseases
MeSH terms: Myopia; Eye Diseases; Refractive Errors
Study type: Interventional

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.
    

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 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.
    

Intervention name(s): 4.0 mm treatment; 3.5 mm treatment
Intervention type(s): Procedure; Procedure
Intervention description(s): PiXL treatment with UV irradiation in a central 4.0-mm ring-shaped zone of the cornea.; PiXL treatment with UV irradiation in a central 3.5-mm ring-shaped zone of the cornea.
Allocation: Randomized
Intervention model: Parallel Assignment
Intervention model description: Prospective, single-masked intraindividually comparing randomized controlled trial. Participants will be randomized to receive ultraviolet (UV) light according to protocol A in one eye and protocol B in the other, which is masked to the participant. Both eyes will be treated during the same visit. Participants are randomized utilizing a computer list of unique random numbers between 1 and 27; an even number will be treated with the 4.0-mm zone in the right eye; an uneven number with the 4.0-mm zone in the left eye.
Masking: Single (Participant)
Primary purpose: Treatment