Human photoreceptor cone density measured with adaptive optics technology (rtx1 device) in healthy eyes

Abstract

The anatomic structures of the anterior segment of the eye enable correct reception of stimuli by the retina, which contains receptors that receive light impulses and transmit them to the visual cortex. The aim of this study was to assess the effect of the size of the sampling window in an adaptive optics (AO) flood-illumination retinal camera (rtx1) on cone density measurements in the eyes of healthy individuals and to investigate the differences in cone density and spacing in different quadrants of the retina. Thirty-three subjects with no ophthalmic or systemic disease underwent a detailed ophthalmologic examination. Photographs of retinal fragments 3 degrees from the fovea were taken using the rtx1 AO retinal camera. We used sampling windows with 3 sizes (50 × 50, 100 × 100, and 250 × 250 μm). Cone density, spacing, and shape were determined using AOdetect software. The median (interquartile range) cone density was 19,269 (4964) cones/mm2. There were statistically significant differences between measurements taken with the 50/50 and 250/250-m windows. There were no significant differences in the cone spacing results between any of the windows examined, but the measurements differed according to location between the superior and temporal quadrants. The most common cone shape was hexagonal (47.6%) for all window sizes and locations. These findings may help in the development of a normative database for variation in cone density in healthy subjects and to allow the best window to be chosen for obtain the most correct values for eccentricity measurements of 3 degrees. In our study, the optimal sampling window was 100 × 100 μm.

Cone photoreceptor density in type I diabetic patients measured with an adaptive optics retinal camera

“…Our study confirmed previous findings of the cone parameters differences between diabetic patients and controls [ 13 - 15 , 22 , 23 ]. Lombardo et al [ 14 ] have studied cone parameters differences at 1.5 degrees eccentricities in DM1 patients with no diabetic retinopathy or nonproliferative diabetic retinopathy and controls.…”

Retinal sensitivity and photoreceptor arrangement changes secondary to congenital simple hamartoma of retinal pigment epithelium

“…As expected, inward to two (2°) centered degree the juxta-foveolar unaffected areas from both eyes showed reduced cone-cells detection (Fig. 6E1, F1); not obligatory meaning photoreceptor cell death but reduced regular capability of software cell detection due to excessive packing of cones inner/outer segments in this 2° region [13]. In other words, our report shows that there are cones in good density on an CSHRPE, and maybe the unpacking effect of the lesion on photoreceptors architecture may facilitate cone inner/outer segments detection, leading to higher values of cell density when compared to normal unaffected retina.…”

Assessing Interocular Symmetry of the Foveal Cone Mosaic

“…Square, 35 μm Wilk et al 21 23 (23) 106,700-214,000 147,000 ± 26,800 Square, 37 μm Wang et al 22 28 (16) First, foveal cone spacing can be close to the resolution limit of most AO systems, introducing lateral interference between neighboring cones and causing them to appear as a single blurred structure as opposed to distinct objects. 27 Foveal cones also have highly variable reflectivity, causing algorithms designed to find bright objects to fail and thus requiring more correction from an observer.…”

“…14 Adaptive optics (AO)-based retinal imaging approaches allow for non-invasive visualization of the photoreceptor mosaic with cellular resolution 15 and have expanded the number of subjects for whom the topography of the cone mosaic has been characterized (Table). [16][17][18][19][20][21][22] The symmetry of the parafoveal cone mosaic has been evaluated in normal populations, 18,[23][24][25][26] although data on the center-most foveal cone mosaic are lacking due to challenges in resolving every cone in the fovea. Some studies have reported cross-sectional data on foveal cone topography in subjects with normal vision, [16][17][18][19][20][21][22] but only Zhang et al 18 have examined the interocular symmetry of foveal cone density, although their study was limited to 20 young subjects with small refractive errors, -3.0 diopters (D) to 0.63 D. Difficulties in visualizing the foveal cone mosaic arise from a number of factors.…”