4.2 Retinal Image Size

What is retinal image size?

distance between 2 image points that correspond to 2 known object points

What is the chief ray?

ray that passes through center of entrance pupil

Why can we use the chief ray to find the RIS?

because blur does not affect RIS

What angle gives us RIS?

angle between incident chief ray and optic axis

Where is the angle formed that gives RIS?

at center of entrance pupil

What is RIS proportional to?

chief ray angle

axial length of the eye

How does the RIS compare for an axial hyperope to an emmetrope?

smaller RIS

How does the RIS compare for an axial myope to an emmetrope?

larger RIS

How does increasing axial hyperopia affect RIS?

the larger the hyperopia the smaller the retinal image

How does increasing axial myopia affect RIS?

the larger the myopia the larger the retinal image

Rank the RIS from largest to smallest for axial RE.

1. axial myope

2. emmetrope

3. axial hyperope

How does refractive ametropia affect retinal image size?

it doesn't, RIS is the same across all refractive ametropia

What is Knapp's plane?

plane containing the primary focal point of the eye

For a spec corrected (at 1º focal plane) axial myope, how does their RIS compare to them uncorrected?

RIS is smaller corrected than uncorrected

For a spec corrected (at 1º focal plane) axial hyperope, how does their RIS compare to them uncorrected?

RIS is larger corrected than uncorrected

For a spec corrected (at 1º focal plane) axial myope, how does their RIS compare an emmetrope?

same size

For a spec corrected (at 1º focal plane) axial hyperope, how does their RIS compare to an emmetrope?

same size

For a spec corrected (at 1º focal plane) refractive hyperope, how does their RIS compare to them uncorrected?

RIS is larger than uncorrected

For a spec corrected (at 1º focal plane) refractive hyperope, how does their RIS compare to an emmetrope?

RIS is larger than an emmetrope

For a spec corrected (at 1º focal plane) refractive myope, how does their RIS compare to them uncorrected?

RIS will be smaller than uncorrected

For a spec corrected (at 1º focal plane) refractive myope, how does their RIS compare to an emmetrope?

RIS will be smaller than uncorrected

How do CLs change RIS?

they dont

What is spectacle magnification?

magnification due to spec lens

What are you comparing withs spectacle magnification?

RIS with vs without lens

What causes spectacle magnification?

lens power and lens form

What is the relative spectacle magnification comparing?

RIS with correcting lens to the RIS of an emmetrope