June 2022
Volume 63, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2022
Cone spectral composition in the fovea
Author Affiliations & Notes
  • Vimal Prabhu Pandiyan
    Ophthalmology, University of Washington School of Medicine, Seattle, Washington, United States
  • Sierra Schleufer
    Ophthalmology, University of Washington School of Medicine, Seattle, Washington, United States
  • Palash Bharadwaj
    Ophthalmology, University of Washington School of Medicine, Seattle, Washington, United States
  • Ramkumar Sabesan
    Ophthalmology, University of Washington School of Medicine, Seattle, Washington, United States
  • Footnotes
    Commercial Relationships   Vimal Prabhu Pandiyan University of Washington, Seattle, Code P (Patent); Sierra Schleufer None; Palash Bharadwaj None; Ramkumar Sabesan University of Washington, Seattle, Code P (Patent)
  • Footnotes
    Support  NIH grants U01EY032055, EY029710, P30EY001730, Research to Prevent Blindness Career Development Award, Burroughs Wellcome Fund Careers at the Scientific Interfaces, DOD Air Force Office of Scientific Research FA9550-21-1-0230
Investigative Ophthalmology & Visual Science June 2022, Vol.63, 4552 – F0466. doi:
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    • Get Citation

      Vimal Prabhu Pandiyan, Sierra Schleufer, Palash Bharadwaj, Ramkumar Sabesan; Cone spectral composition in the fovea. Invest. Ophthalmol. Vis. Sci. 2022;63(7):4552 – F0466.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose : The fovea subserves high acuity vision by virtue of its densest packing of cone photoreceptors in the retina. Recent advances in high-resolution adaptive optics (AO) imaging have enabled detailing the distribution of foveal cones in humans, but their differentiation by spectral type has remained elusive. While it is known from anti-S-opsin staining that the proportion of short-wavelength (S-) cones decreases towards the foveal pit, the lack of immunostains for differentiating long and middle-wavelength (LM-) cones has made it impossible to ascertain their foveal distribution. Here we explore the spectral composition of the human fovea using an AO line-scan OCT-based optoretinogram.

Methods : A reflective mirror-based line-scan AO-OCT was used to image the fovea in two subjects. Volumes were recorded after 1-3 minutes of dark adaptation and a 660±10 nm bleach. The B-scan rate was 12 kHz and the field of view ranged from 1-1.6°. The volumes were reconstructed and registered. The optical phase change between the two reflections encasing the outer segment - the inner-outer segment junction, and outer segment tips - was calculated for each cone, and converted to optical path length (OPL). The change in OPL due to bleach was subjected to clustering analysis to distinguish cone spectral types. L:M-cone ratios and percent S-cones were calculated in the steps of 0.2° by 0.7° rectangular regions-of-interest in the range between 0.3° to 0.9° eccentricity along the 4 cardinal meridians.

Results :
The resolution was sufficient to visualize and spectrally classify cones 0.3° from the foveal center. Within 1° eccentricity, 9253 and 9115 cones were typed for subjects S1 and S2 respectively, with high accuracy. The proportion of S-cones increased with eccentricity; S1 : 2.2 to 6% and S2 : 3 to 8.9%. The rate of increase in S-cone proportion was the same in both, equal to 2.5 % per deg. The L:M cone ratio remained relatively stable within 1° eccentricity; S1 : 1.8 to 2.4 (Mean= 2.0), and S2: 1.2 to 2.0 (Mean = 1.5). No systematic difference was observed across the 4 cardinal meridians.

Conclusions : The first view of the human trichromatic cone mosaic in the fovea reveals an increasing S-cone proportion in line with prior reports, and a relatively stable L:M cone ratio. This has important implications for understanding the genetic mechanisms that control the photopigment expressed in cones and cell migration processes that occur during foveal development.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.


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