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Year 1 Physiology of Vision > Contrast Sensitivity > Flashcards

Contrast Sensitivity Flashcards

1
Q

What is illuminance?

A

The amount of light landing on a surface

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2
Q

What is luminance?

A

The amount of light coming from a surface (emitted or reflected)

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3
Q

What is the contrast threshold for photopic conditions?

A

2% difference

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4
Q

What is the contrast threshold for scotopic conditions?

A

14% difference

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5
Q

What is the high-frequency cut-off of the CSF?

A

60 c/deg

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6
Q

What is the low-frequency roll-off of the CSF?

A

0.3 c/deg

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7
Q

What’s the peak frequency of the CSF?

A

3-6 c/deg

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8
Q

Why does the high-frequency cut-off occur?

A

Optics of the eye limit the detail that can be resolved

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9
Q

Why does the low-frequency roll-off occur?

A

Lateral inhibition (objects so large that they inhibit receptive fields of surrounding retinal cells)

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10
Q

What factors affect CSF?

A

Age
Optics of the eye
Retinal illuminance
Retinal eccentricity
Receptive fields
Pupil diameter
Spatial frequency channels

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11
Q

What is a spatial frequency channel?

A

Different areas of sensitivity to spatial frequency which together make up the CSF when combined

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12
Q

What does a Fourier analysis do?

A

Separates the CSF into SF channels

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13
Q

What charts can be used to measure contrast sensitivity?

A

Pelli-Robson
Low contrast Bailey-Lovie
Vistech

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14
Q

What pathologies can affect the CSF?

A

Cataract
Diabetic retinopathy
Retinitis pigmentosa
AMD
Glaucoma
Optic neuritis/atrophy
Uncorrected refractive error
Keratoconus
Iritis
CLs
Recovery from refractive surgery
Amblyopia

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15
Q

What can low contrast sensitivity affect?

A

Facial recognition
Reading
Mobility
Viewing low contrast objects

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16
Q

How can the issues caused by low contrast sensitivity be helped?

A

Improved lighting
CCTV system with contrast enhancement
Higher contrast on objects (e.g. when reading)

17
Q

How does age affect contrast sensitivity?

A

For babies: very low, so more sensitive to lower spatial frequencies (can’t detect detail). 2-3 c/deg. Has a much flatter curve. Improves with age.
Peak of CSF at age 20.
Older people: lose high spatial frequencies (can’t detect detail and contrast sensitivity reduced)

Year 1 Physiology of Vision (5 decks)

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