Light and the Eye

Flashcards covering vocabulary related to light and the eye, including properties of light, components of the eye, vision conditions, photoreceptors, and phototransduction.

Short Wavelengths

A range of the electromagnetic spectrum including ultraviolet and visible light up to 500 nm.

Visible light

The portion of the electromagnetic spectrum typically ranging from 400 nm to 700 nm.

Long Wavelengths

A range of the electromagnetic spectrum including infrared and visible light from 600 nm.

Ultraviolet

A type of electromagnetic radiation with wavelengths shorter than visible light.

Infrared

A type of electromagnetic radiation with wavelengths longer than visible light.

Quantum Mechanics

A scientific theory describing the dual nature of light.

Wave properties of light

Characteristics of light, such as wavelength.

Particle properties of light

Characteristics of light, such as intensity.

Reflection

When light hits a surface and is not absorbed.

Refraction

When light travels through a surface and is bent.

Refraction Index

A measure of how much light is bent when passing through a medium (e.g., Vacuum: 1.00000, Water: 1.333).

Illuminance (lux)

A physical measurement representing the amount of light falling on a surface.

Luminance (cd/m2)

A physical measurement representing the amount of light coming off of a surface.

Reflectance

The proportion of illuminance reflected, calculated as Luminance / Illuminance.

Lightness

A subjective measurement referring to the perceived reflectance of a surface.

Brightness

A subjective measurement referring to the perceived luminance off of a surface.

Optics

The science concerned with the properties of light, its refraction and absorption, and the refracting media of the eye.

Eye

An optical system designed to focus light onto the retina.

Cornea

Part of the eye with a refractive index of 1.38, located at the front.

Aqueous Humour

Part of the eye with a refractive index of 1.33.

Lens

Part of the eye with a refractive index of 1.41, responsible for focusing light.

Vitreous Humour

Part of the eye with a refractive index of 1.34.

Iris

The colored structure in the eye that controls the size of the pupil.

Pupil

The opening in the center of the iris that regulates the amount of light entering the eye.

Circular muscles of iris

Muscles that contract to cause a constricted pupil.

Radial muscles of iris

Muscles that contract to cause a dilated pupil.

Pinhole Camera Principle

A principle illustrating how a small aperture leads to sharper focus.

Ciliary muscle

A muscle connected to the lens that aids in accommodation.

Accommodation

The process by which the lens changes shape to focus objects at different distances onto the retina.

Emmetropia

A lens condition where the eye is relaxed and light focuses correctly on the retina.

Myopia

A lens condition (nearsightedness) where light focuses in front of the retina.

Hyperopia

A lens condition (farsightedness) where light focuses behind the retina.

Presbyopia

A lens condition listed as one of the common eye conditions.

Astigmatism

A lens condition listed as one of the common eye conditions.

Retina

The light-sensitive layer at the back of the eye where light is focused.

Photoreceptors

Cells in the retina that convert electromagnetic energy into neural energy; includes rods and cones.

Bipolar Cells

Cells in the retina that transmit signals from photoreceptors to retinal ganglion cells.

Retinal Ganglion Cells

Cells in the retina that receive signals from bipolar cells and send them to the brain.

Phototransduction

The conversion of electromagnetic energy into neural energy, occurring in photoreceptors.

Rod Photoreceptors

Achromatic, highly light sensitive photoreceptors found in the periphery, responsible for night vision, low acuity, sluggish response, approximately 120 million.

Cone Photoreceptors

Chromatic, not very light sensitive photoreceptors largely Foveal, responsible for day vision, high acuity, rapid response, approximately 5 million.

Fovea

The central part of the retina with a high concentration of cones for high-acuity vision.

Blind spot

An area on the retina (where the optic nerve exits) with no receptors.

Rod vision

Vision primarily mediated by rods, with peak sensitivity around 500 nm.

Cone vision

Vision primarily mediated by cones, with peak sensitivity around 560 nm.

Dark Adaptation

The process where the light detection threshold decreases over time in the dark.

Light Detection Threshold

The minimum amount of light energy required for detection.

Rod/Cone Break

The point during dark adaptation (around 7 minutes) where rod sensitivity surpasses cone sensitivity.

Trichromatic Cone System

A system involving three types of cones: Short (S), Medium (M), and Long (L).

Short (S) Cones

Cones peaking in sensitivity at 419 nm.

Medium (M) Cones

Cones peaking in sensitivity at 531 nm.

Long (L) Cones

Cones peaking in sensitivity at 558 nm.

Tetrachromacy

A normal animal cone system involving four types of cones.

Trichromacy

A normal animal cone system involving three types of cones, typical for humans.

Dichromacy

A normal animal cone system involving two types of cones.

Monochromacy

A normal animal cone system involving one type of cone.

Deuteranopia

An abnormal human cone system.

Protanopia

An abnormal human cone system.

Tritanopia

An abnormal human cone system.

Rhodopsin

A visual pigment molecule found in the outer segment of rod photoreceptors.

Retinal (11-cis)

A component of the rhodopsin molecule.

G protein (transducin)

A protein involved in the cascade of events during phototransduction.

cGMP Phosphodiesterase

An enzyme involved in the cascade of events during phototransduction.

cGMP-gated channel

A channel on the outer segment membrane that is regulated by cGMP.