Optics of Vision

Light refraction

Optics of Vision

Optics of Vision

Refraction power a lens “Diopter” = 1 m / focal length

Optics of Vision

Optics of Vision

Picture Formation

cataracts (opacities in the lens)

Picture Formation

• Lens accommodation

• Pupil adjustment

• Fusion of the two eyes

Optics of Vision

Optics of Vision

Accommodation

Accommodation

Accommodation

Vision problemsAmetropia : refraction error, inabiulity of properly focusing light on the retina, a frequent reason for reduced visual acuity

Vision problems

Accommodation

Presbyopia: Loss of accommodation by the lens

Vision problemsAstigmatism : irregular curvature of either the cornea or the lens, which lead to blurred or distorted vision due to parts of the image are out of focus.

Accommodation and parasympathetic

Pupillary Adjustment

Pupillary Adjustment

Visual acuity

Normally , people has the ability to distinguish contours that are approximately 1.75 mm apart at 6 meters distance from the eye

Visual acuity

Normally , people has the ability to distinguish contours that are approximately 1.75 mm apart at 6 meters distance from the eye

Photoreceptors

Cones

Rods

Color Blindness

Color Blindness

Red-green color blindness

Color Blindness

Red-green color blindness X linked

Color Blindness Red-green color blindness

X linked Deuteranope >>> green Protanope >>> red

Tritanopia >>> Blue Chromosome 7

***anomaly : shift in the spectrum of one of the proteins i.e. Deuteranomaly, Protanomaly, Tritanopia

Color Blindness

Tritanopia

Protanopia

Deuteranopia

Color Blindness

Tritanopia

Protanopia

Deuteranopia

Color Blindness

Tritanopia

Protanopia

Deuteranopia

Color Blindness

Color Blindness

Type Problematic colors

Deuteran (green)

Green/red, green/blue, green/gray, green/brown, blue/purple, orange/red, yellow/orange.

Protan (red)

purple/dark blue, orange/green, brown/dark green, red/brown, green/yellow, gray/purple

Tritan (blue)

blue/yellow, violet/yellow-green, red/red-purple, dark blue/black, yellow/white

Color Blindness

Type Prevalence

Deuteranomaly (green) 4.63%

Deuteranopia (green) 1.27%

Protanomaly (red) 1.08%

Protanopia (red) 1.01%

Tritanomaly (blue) 0.02%

Tritanopia (blue) 0.03%

Color Test Chart

74 VS 21

Color Test Chart

42 VS 4 “green” / 2 “red”

In conclusion

The colorblind have a narrowed color perception. Green is still green and red stays red most of the time, but not as vibrant or bright as a non colorblind would see it. Colors lie closer to each other, especially shades of colors.

VISUAL PATHWAY

The retinohypothalamic pathway• day/night cycle• Melanopsin ganglionic cells

Visual Pathways

The optic nerve has two principle branches

Right hemisphere

Hemi - anopia

Right hemisphere

Quadrant - anopia

Light Adaptation

Pupillary size

Pupillary LightReflex

Olivary pretectal nucleus

Edinger-Westphal nucleus

Edinger-Westphal nucleus

Light Adaptation

Pupillary size

Neural adaptation

Photoreceptor adaptation

Light Adaptation Pupillary size Neural adaptation Photoreceptor adaptation

Night blindness

Retinitis pigmentosa

Ganglionic Cells Subtypes

XY

XY

Position Receptive field Details movement

XY

Position Receptive field Details movement

W

Primary visual cortex

Lateral geniculate nucleus

Lateral geniculate nucleus

Lateral geniculate nucleus

Lateral geniculate nucleus

Lateral geniculate nucleus

Parvocellular systemMagnocellular system