FOVEA: a new program to standardize the measurement of foveal pit morphology

Abstract

The fovea is one of the most studied retinal specializations in vertebrates, which consists of an invagination of the retinal tissue with high packing of cone photoreceptors, leading to high visual resolution. Between species, foveae differ morphologically in the depth and width of the foveal pit and the steepness of the foveal walls, which could influence visual perception. However, there is no standardized methodology to measure the contour of the foveal pit across species. We present here FOVEA, a program for the quantification of foveal parameters (width, depth, slope of foveal pit) using images from histological cross-sections or optical coherence tomography (OCT). FOVEA is based on a new algorithm to detect the inner retina contour based on the color variation of the image. We evaluated FOVEA by comparing the fovea morphology of two Passerine birds based on histological cross-sections and its performance with data from previously published OCT images. FOVEA detected differences between species and its output was not significantly different from previous estimates using OCT software. FOVEA can be used for comparative studies to better understand the evolution of the fovea morphology in vertebrates as well as for diagnostic purposes in veterinary pathology. FOVEA is freely available for academic use and can be downloaded at: .

Shape Decomposition of Foveal Pit Morphology Using Scan Geometry Corrected OCT

“…PC1, which describes the depth of the foveal pit, covers over 80% of the shape variation. This is in line with existing analysis of the foveal pit [7,8], which relies on explicit measurements or modeling of pit depth and diameter. It is reassuring to see that our unsupervised analysis was able to automatically find the same characteristics (PC1 and PC4) of the foveal pit that is deemed important by the community.…”

“…Notably, Wilk et al [3] presented a study using multi-modal imaging to evaluate the relationship between foveal pit morphology from optical coherence tomography (OCT) imaging and cone density measures from adaptive optics scanning laser ophthalmoscopy (AOSLO) from subjects with albinism, showing considerable variation between the two measures. One limitation of these existing studies is their reliance on the evaluation of summary measurements (pit depth, diameter and slope) [7] or parametric models [8] of the foveal pit. Such analysis are restricted by the location of the measurement or the fit of the model, and do not observe the 3D local or spatial relationship of the foveal pit morphology across a population.…”

Spectral‐domain optical coherence tomography imaging of normal foveae: A pilot study in 17 diurnal birds of prey

“…46,47,51 Other parameters that need to be considered when evaluating the fovea include the width of the foveal pit, the curvature, and the steepness of the foveal walls. 52 Despite the coexistence of foveal hypoplasia (or better defined as fovea plana) and other ophthalmic disorders in human medicine, there are no studies that correlate visual acuity with foveal architecture as a primary variable. 53,54 Optical advantages derived per se from the presence of a fovea, results from the cumulative effect of a number of variables.…”

Structure and function of the bird fovea

“…Foveas with all retinal layers in the centre, albeit with smaller thickness than in the surrounding tissue (Duke‐Elder, ; Slonaker, ; Walls, ; Wood, ), are found, for example, in the central retina of American goldfinches, barn swallows, cockatoos, gulls, hummingbirds, pigeons, redshanks, rusty‐margined flycatchers, silvereyes, thornbills and white‐crowned sparrows, as well as in the temporal retina of albatrosses, golden eagles (Figure c) and scops owls (Baumhardt et al, ; Clarke & Whitteridge, ; Coimbra et al, 2014a; Coimbra, Marceliano, Andrade‐da‐Costa, & Yamada, ; Kajikawa, ; Lisney, Wylie, Kolominsky, & Iwaniuk, ; Moore, Yoo, Tyrrell, Benes, & Fernández‐Juricic, ; O'Day, ; Polyak, ; Pumphrey, ). Foveas which lack ganglion cell somata in the foveal centre are present, for example, in the central retina of bank swallows (Figure b), kingfishers (Figure b), golden eagles (Figure a), blackbirds (Figure c), albatrosses (Figure d), black vultures, eastern meadowlarks, red‐backed hawks (Figure a), sparrowhawks, rooks, house sparrows, starlings, laughing kookaburras and great kiskadees in the temporal retina of swifts (Figure b) and in the central and temporal areas of kestrels and buzzards (Figure a; Chievitz, ; Coimbra et al, ; Franz, ; Inzunza, Bravo, & Smith, ; Kajikawa, ; Kolmer, ; Moore et al, ; Moroney & Pettigrew, ; O'Day, ; Oehme, ; Polyak, ; Snyder & Miller, ; Tansley, ; Tyrrell, Moore, Loftis, & Fernández‐Juricic, ; Walls, ).…”