Blue cone monochromacy: visual function and efficacy outcome measures for clinical trials

Area of Science:

• Ophthalmology
• Genetics
• Retinal Diseases

Background:

• Blue Cone Monochromacy (BCM) is an X-linked retinopathy affecting L- and M-cone opsins.
• Cone photoreceptors in BCM retain structural integrity, suggesting gene therapy potential.
• Understanding BCM vision is crucial for designing effective clinical trials.

Purpose of the Study:

• To examine vision in Blue Cone Monochromacy (BCM) patients.
• To identify clinically feasible outcome measures for future gene therapy trials.

Main Methods:

• Studied 25 BCM patients (ages 5-72) using kinetic/static chromatic perimetry and eye movement recordings.
• Assessed foveal and parafoveal vision with chromatic microperimetry.
• Evaluated spectral sensitivity functions under dark- and light-adapted conditions.

Main Results:

• BCM patients showed normal S-cone function but reduced light-adapted perimetry.
• Rods mediated vision for stimuli typically perceived by L/M-cones in BCM.
• Chromatic microperimetry revealed significant sensitivity loss to red stimuli in the fovea and parafovea.

Conclusions:

• BCM rods function under conditions usually associated with daylight vision.
• Localized and retina-wide measures were identified to assess L/M-cone vision improvement in BCM gene therapy trials.