A note about retinal structure and visual acuity. A light microscopic study of the cones in fovea centralis

Abstract

ABSTRACT.Purpose: Production of reliable sections of fovea centralis of primate retina. Methods: Rhesus monkey eyes were processed using a new technique known to minimize artefacts and cell-shrinkage in other tissues. An in vivo vascular perfusion-fixation technique with an isotonic fixative followed by a process of slow infiltration with small increments in concentrations were used. Results: Tangential 1 mm thick serial-sections showed a very good morphology. An average cone-to-cone-center distance of 3.8 mm in the central part of the fovea centralis was found. A cone-to-cone-center distance of 2.2-2.6 mm is suggested in the literature. Conclusion: In spite of the limited study we believe that the new technique has resulted in less tissue shrinkage. Our results are discussed in relation to maximal possible resolution of the eye. Our calculations (for green light) support the idea that the structure of the fovea centralis and the refractive media of the eye are developed close to perfection.

Eye shape and activity pattern in birds

“…The longer the axial length of the eye and PND, the larger the image projected onto the retina. Since bird photoreceptors are a near-constant size and are packed into the retina in a regular and conservative way, in general a larger retina contains more photoreceptor cells (Snyder & Miller, 1977;Land, 1980;Ali & Klyne, 1985;Rostgaard & Qvortrup, 1999;Land & Nilsson, 2002). An eye with a larger image projected over more photoreceptor cells is capable of perceiving more detail in that image, or heightened visual acuity, because each photoreceptor processes a smaller portion of the image.…”

Evolution of Avian Eye Size Is Associated with Habitat Openness, Food Type and Brain Size

“…For species foraging in a specific environment, the retina has undergone extraordinary The eye's ability to extract visual information from the environment depends on its size and dimensions [9]. A larger eye can accommodate a larger retina, allowing for more photoreceptors due to their organized and densely packed arrangement within the retina [1,10,11]. Thus, larger eyes with larger retinas and more photoreceptors have a greater capacity to capture visual information from the environment [1,2,9,12].…”