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Jennifer R Chao, Xiaoyun Jiang, James A Kuchenbecker, Anna-Lisa Doebley, Maureen Neitz, Jay Neitz, Ramkumar Sabesan; S-cone function in Blue Cone Monochromacy. Invest. Ophthalmol. Vis. Sci. 2019;60(9):585.
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© ARVO (1962-2015); The Authors (2016-present)
To determine the structure of foveal cones and S-cone visual acuity in blue cone monochromacy (BCM) compared to normal controls
L and M opsin genes were sequenced in the BCM subject. S-cone and L/M-cone isolating tumbling ‘E’ visual acuity was measured in one BCM patient and 4 normal controls. Cone-isolating stimuli were generated by a customized Maxwellian view visual simulator and projected onto the retina through a 1 mm artificial pupil. The simulator consisted of an adjustable spectral light source (380-780 nm)and high-resolution digital light projector that generated spatial patterns, enabling precise control of spatiochromatic stimuli. A custom adaptive optics SLO (AOSLO) with 840 nm light in reflectance was used to obtain photoreceptor images in the central 6 degrees. These images were registered, montaged and assessed for the locus of fixation relative to the anatomical foveola.
Genetic testing of a 27 yo male with a history of high myopia (SE -11.50D OU) and Snellen VA of 20/50 OD and 20/70 OS revealed LIAVA and MIAVA haplotypes in OPN1LWand OPN1MW, respectively. These haplotypes result in complete exon 3 skipping and the absence of red and green photopigment expression. AOSLO imaging revealed that fixation of the BCM subject was located 0.5 deg infero-temporal to the anatomical fovea. At this retinal location, an abundance of larger bright punctate spots (presumably S-cones) were visualized within a mosaic of smaller diameter rods and darker gaps, presumably housing non-waveguiding L and M cone inner segments. S cone isolating visual acuity of the BCM subject was 20/69.5±3.4 OD, which was noted to be significantly higher than normal controls who obtained 20/167.3±16.1under the same conditions. Under L and M cone isolating conditions, the largest Snellen E (20/2784) was beyond visibility, demonstrating the absence of L/M cone vision in the BCM subject.
The BCM subject demonstrated greater S-cone isolating visual acuity compared to normal controls. This is likely due to an increased density of S-cones at fixation, which was noted to be slightly offset from the fovea.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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