Focusing Light on the Retina and Vision Physiology

These flashcards cover key vocabulary and concepts related to the physiology of vision, light focusing, and the function of the human eye.

Lens

A transparent structure in the eye that adjusts its curvature to help focus light on the retina.

Accommodation

The process by which the lens changes shape to focus light for near or distant vision.

Presbyopia

A condition associated with aging, where the eye loses its ability to accommodate.

Refraction

The bending of light rays as they pass from one transparent medium to another.

Convex Lens

A lens that is thicker in the center than at the edges, converging light rays.

Concave Lens

A lens that is thicker at the edges than in the center, dispersing light rays.

Myopia

Nearsightedness, a condition where light is focused in front of the retina due to an elongated eyeball.

Hyperopia

Farsightedness, a condition where light is focused behind the retina due to a shortened eyeball.

Astigmatism

A condition caused by unequal curvatures in different parts of the cornea or lens.

Electromagnetic Radiation

Energy waves that includes visible light, with a range from long radio waves to short X-rays.

Visible Light

The portion of the electromagnetic spectrum that is perceived by the human eye, with wavelengths between 400 and 700 nm.

Pupil Constriction

The process mediated by the parasympathetic nervous system to reduce divergent light rays entering the eye.

Convergence of Eyes

The medial rotation of eyeballs to focus on a near object.

Far Point of Vision

The distance beyond which the lens does not need to change shape for focusing.

Ciliary Muscles

Muscles that control the shape of the lens for focusing.

Photoreceptors

Specialized neurons in the retina that respond to light, including rods and cones.

Rods

Photoreceptors that are highly sensitive to light and provide vision in low-light conditions.

Cones

Photoreceptors that are less sensitive to light and enable color vision in bright light.

Rhodopsin

A light-sensitive pigment found in rods that absorbs light photons.

Vitamin A

A nutrient necessary for the synthesis of visual pigments in photoreceptors.

Color Blindness

A hereditary condition characterized by the lack of one or more cone pigments.

Phototransduction

The process through which light is converted into electrical signals in the retina.

11-cis Retinal

The bent form of retinal that is involved in light absorption.

All-trans Retinal

The straight form of retinal that occurs after light absorption.

Visual Cycle

The metabolic pathway that regenerates photopigments in the photoreceptors.

Bleaching Phenomenon

The fading of color in the photoreceptors when exposed to bright light.

Ciliary Zonule

Fibers that connect the ciliary muscles to the lens, affecting its shape.

Neural Layer of Retina

The innermost layer of the retina containing photoreceptors and other retinal neurons.

Visual Acuity

The sharpness or clarity of vision, often associated with the density of cones.

Photopigments

Molecules in the photoreceptors that change shape upon absorbing light.

Ganglion Cells

Retinal neurons that collect visual information and transmit it to the brain.

Macula Lutea

The area of the retina responsible for high acuity vision.

Fovea Centralis

The part of the retina with the highest density of cones, crucial for sharp vision.

Somatic Motor Neurons

Nerves that innervate the muscles controlling the convergence of the eyes.

Wavelength

The distance between successive peaks of a wave, determining color in light.

Color Spectrum

The range of colors produced when light is dispersed, visible as a rainbow.

Phagocytized

The process by which dead or damaged photoreceptor tips are consumed by neighboring cells.

Outer Segment of Photoreceptors

The part of photoreceptors that contains the light-absorbing pigments.

Cilium

A cellular structure that connects the inner and outer segments of photoreceptors.

Clinical Homeostatic Imbalance

Conditions that result from changes in vision mechanics, such as refractive errors.

Wavelength Absorption

The specific wavelength of light that a photopigment can absorb.

RPE65 Enzyme

An enzyme crucial for converting all-trans retinal back to 11-cis retinal.

Pigment Regeneration

The process of converting bleached photopigments back to their original form.

Wavelength Overlap

When different cone types react to similar wavelengths of light, enabling a range of colors.

Enzymatic Steps

Chemical reactions that facilitate the regeneration of visual pigments.

Dark Adaptation

The process by which eyes adjust to darkness, requiring time for pigment regeneration.

Camera Flash Effect

Temporary blindness caused by sudden bright light overwhelming photoreceptors.

Retinal Pigment Epithelium (RPE)

A layer of cells supporting photoreceptors and involved in the visual cycle.

Vitreous Humor

The clear gel that fills the space between the lens and the retina.