Physiology of visual acuity
Human visual acuity depends on several sizes: Physically the size of the pupil limits the resolution of the eyeball, physiologically the resolution is determined by the density of the receptors (rods and cones) and the signal processing of the receptive fields of the retina. The resolution reaches its maximum value when the pupil is maximally dilated and there is sufficient brightness in the area of the fovea centralis retinae (central point of sharpest vision on the retina).
- Resolving power of the eyeball
- Image quality on the retina (determined by the refractive media of the eye – cornea, aqueous humor, lens and vitreous body)
- Optical properties of the object and its surroundings (contrast, color, brightness)
- Shape of the object: horizontal straight lines, vertical straight lines and right angles can resolve the retina and central nervous system higher than the eyeball alone.