Optics Lecture 4 Flashcards
Can we prescribe refractive correction from wf measurements
No
Gold standard method of refraction
Clinical phoroptor method
Give the comprehensive description of eyes optical aberrations from which the retinal image can be computed using the theory of physical or geometrical optics
Shack-Hartmann aberrometry
What types of aberrations to we fix w/o surgery
Astigmatism and defocus
How do we correct HO aberrations
Surgery
How are subjective a objective refraction different in terms of chromatic aberrations
By wavelength used
- Obj - IR light
- sub - white light
How are subjective a objective refraction different in terms of stiles-Crawford effect
PR are fine tuned toward center of pupil
- light from periphery isnt caught by cones
How are subjective a objective refraction different in terms of max plus technique
Obj - give max +
Sub - give mean
How are subjective a objective refraction different in terms of measurement plane of the instrument
Sub - spectacle place
Obj - corneal plane
What must you do to compare obj (wf) with sub (va)
Make all factors the same
- wavelength
- Pupil size
- Plane of measure
- Accommodation
- Measurement technique
What is the population mean for subjective refraction for 3mm pupil
.19D
What is the population mean for subjective refraction for 6mm pupil
.23D
Does the refractive error for subjective method change when the pupil dilates
No
What is the population mean for objective refraction for 3mm pupil
Hyperopic relative to subjective mean
What is the population mean for objective refraction for 6mm pupil
Myopic relative to subjective
When HO aberration are small, how do all of the metrics relate
They are the same
When HO aberrations are large, how do all the metrics relate
Different metrics give different refraction
Are many objective refracts accurate/precise
Yes
Is zernike accurate and precise
No, too myopic
Is paraxial accurate/precise
No, too hyperopic
