Advanced Cross Linking for Low-grade Myopia
Condition: Myopia; Corneal Crosslinking
MeSH terms: Myopia
Study type: Interventional

Summary: 
      To evaluate the improvement in myopic refractive error and the corneal endothelial safety
      with a corneal crosslinking treatment regimen for mild myopia. The treatment involves a 4-mm
      central treatment zone in high oxygen environment without corneal epithelial debridement.
    

Detailed description: 
      The study is designed as a prospective, single-masked intraindividually comparing randomized
      controlled trial involving healthy volunteers ≥18 years of age of both genders with mild
      myopia, performed at the Department of Clinical Sciences / Ophthalmology, Umeå University
      Hospital, Umeå, Sweden. The study involves 23 persons with a myopia of -0.5 to -2.5 diopters
      (D) and astigmatism of ≤0.75 D. All participants are treated with phototherapeutic
      intrastromal corneal collagen cross-linking (PiXL) without epithelial debridement (epi-on),
      after topical riboflavin. For myopia of less than 1.0D, 10 J/cm2 will be used, for higher
      levels of myopia 15J/cm2 will be used, and the treatment involves continuous delivery of
      oxygen around the eye using an oxygen mask to achieve an oxygen concentration of ≥90% during
      treatment. Participants will be 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. Both eyes will be treated during the same visit.

      Protocol A: UV irradiation in a central 4 mm homogenous zone of the cornea. Protocol B: UV
      irradiation in a central ring-shaped 4 mm area of the cornea. Patients are randomized
      utilizing a computer list of unique random numbers between 1 and 23; an even number will be
      treated with a homogeneous zone in the right eye; an uneven number with a homogeneous zone in
      the left eye. All patients are informed about the procedures and provide oral and written
      consent before inclusion in the study.

      At baseline, before treatment, each eye is evaluated with slit-lamp examination, subjective
      refraction, determination of uncorrected (UCVA) and best corrected (BSCVA) visual acuities
      using the LogMAR fast protocol and intraocular pressure (IOP) using Goldmann applanation
      tonometry. Each eye is photographed using the "25 pictures" program with the Pentacam HR®
      (Oculus, Inc. Lynnwood, WA) under standardized, mesopic light conditions. Keratometry
      readings, central corneal thickness and the average corneal densitometry values (corneal
      light backscatter), expressed as standardized gray scale units, GSU) is determined with the
      Pentacam HR®. Central corneal endothelial photographs are taken with the Topcon SP-2000P
      specular microscope (Topcon Europe B.V., Capelle a/d Ijssel, the Netherlands), and the
      corneal endothelial cell count is calculated from a cluster of 25 cells from each photograph.

      All the above mentioned investigations are repeated at 1, 3, 6,12 and 24 months after the
      treatment. At 1 week after treatment, UCVA is registered and a slit-lamp examination, a
      subjective comparison of discomfort and visual performance in each eye and an
      autorefractometer measurement are performed. One day after treatment the latter 3
      examinations are performed.
    

Intervention name(s): PiXL
Intervention type(s): Procedure
Intervention description(s): Phototherapeutic intrastromal corneal collagen cross-linking (PiXL) performed in a high-oxygen environment without corneal epithelial debridement, for treatment of mild myopia.
Allocation: Randomized
Intervention model: Single Group 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.
Protocol A: UV irradiation in a central 4 mm homogenous zone of the cornea. Protocol B: UV irradiation in a central ring-shaped 4 mm area of the cornea. Patients are randomized utilizing a computer list of unique random numbers between 1 and 23; an even number will be treated with a homogeneous zone in the right eye; an uneven number with a homogeneous zone in the left eye.
Masking: Single (Participant)
Primary purpose: Treatment
Keywords: Myopia; corneal Crosslinking