9- Visual Acuity and Optical Principles

These flashcards cover key concepts of visual acuity and optical principles, including definitions, physiological details, and implications for vision assessment.

Where is the entrance pupil located?

About 3mm behind the corneal vertex.

What is diffraction?

Limitations of the aperture that causes a spread of light.

At what pupil diameter does diffraction occur?

2mm

At what pupil diameter do aberrations become a problem?

5mm.

What happens to the spread of the image when the pupil is larger than 5mm?

It increases because the peripheral regions of the cornea and lens are often afflicted with optics aberrations

What pupil size does image quality not improve much beyond?

2.5mm.

How does scatter affect image quality?

Ocular media has microscopic structure, causing light to scatter.

What happens to scatter with age?

It increases.

What wavelength is scattered most in the eye?

Blue light.

What is night myopia?

Minimal light in the dark & not having a good target to focus on in the dark causes increased accommodation, leading pt to be more myopic

How many diopters does vision change during night myopia?

Approximately -0.75D.

What is instrument myopia?

AR machine tries to stimulate a balloon far away but the brain realizes that it is not that far, and stimulates accommodation

How many cones are connected to bipolar cells in the fovea?

One cone.

What is the minimum angle of resolution in a normal healthy eye?

30 seconds of arc to 1 minute arc.

At what duration in the dark does rod-cone break occur?

6 minutes.

What is the critical period in vision development?

Time span needed for visual functional integrity for normal adult vision.

What is NOT amblyopia?

Time span during which visual functional integrity is needed for subsequent development of normal adult vision

Which stream is smaller in LGN of an amblyope?

Parvocellular stream.

Which acuity is immune to decrease exposure duration?

Vernier acuity.

Which acuity is NOT immune to decreased exposure duration?

Stereoscopic acuity.

Which acuity is resistant to decreased contrast?

Vernier alignment acuity.

What acuities are NOT resistant to decreased contrast?

D) Both A & B