Directionality of individual cone photoreceptors in the parafoveal region. (December 2015)

• Record Type: Journal Article
• Authors: Morris, Hugh J.; Blanco, Leonardo; Codona, Johanan L.; Li, Simone L.; Choi, Stacey S.; Doble, Nathan
• Is Part Of: Vision research. Volume 117(2015)
• Page Start: 67
• Page End: 80
• Publication Date: 2015-12
• Subjects: SCE-I Stiles–Crawford Effect of the First Kind -- OSCE Optical Stiles–Crawford Effect -- SLO scanning laser ophthalmoscope -- OCT optical coherence tomography -- AO adaptive optics -- SH-WFS Shack–Hartmann wavefront sensor -- DM deformable mirror -- SLD superluminescent diode -- MP moving pupil; Cone photoreceptors -- Stiles–Crawford Effect of the First Kind -- Optical Stiles–Crawford Effect -- In vivo retinal imaging -- Adaptive optics -- Retina; Vision -- Periodicals; 573.88
• DOI: 10.1016/j.visres.2015.10.008
• Languages: English
• ISSNs: 0042-6989

Abstract

Highlights: Subjects had a nasal (0.81 ± 0.30 mm) bias in cone alignment from the pupil center. Cone disarray was less in the horizontal than in the vertical meridian. Cone directionality was anisotropic and decreased with larger eccentricity. The parafoveal cones demonstrate anterior pointing alignment. Abstract: The pointing direction of cone photoreceptors can be inferred from the Stiles–Crawford Effect of the First Kind (SCE-I) measurement. Healthy retinas have tightly packed cones with a SCE-I function peak either centered in the pupil or with a slight nasal bias. Various retinal pathologies can change the profile of the SCE-I function implying that the arrangement or the light capturing properties of the cone photoreceptors are affected. Measuring the SCE-I may reveal early signs of photoreceptor change before actual cell apoptosis occurs. In vivo retinal imaging with adaptive optics (AO) was used to measure the pointing direction of individual cones at eight retinal locations in four control human subjects. Retinal images were acquired by translating an aperture in the light delivery arm through 19 different locations across a subject's entrance pupil. Angular tuning properties of individual cones were calculated by fitting a Gaussian to the reflected intensity profile of each cone projected onto the pupil. Results were compared to those from an accepted psychophysical SCE-I measurement technique. The maximal difference in cone directionality of an ensemble of cones, ρ ¯, between the major and minor axes of the Gaussian fit was 0.05 versus 0.29 mm −2 in one subject. All four subjects were found to have a mean nasal bias of 0.81 mm with a standard deviation of ±0.30 mm in the peak position at all retinal locations with mean ρ ¯ value decreasing by 23% with increasing retinal eccentricity. Results show that cones in the parafoveal region converge towards the center of the pupillary aperture, confirming the anterior pointing alignment hypothesis.