Unit 4: Optics Flashcards
Equation to calculate contact lens prescription from spectacle prescription
F(new)= F(current) / (1- dF(current))
Where
F= Power
d= vertex in METERS
Plus power lenses produce larger or smaller retinal image compared to no correction
Larger
Minus powered lenses produce a larger or smaller retinal image compared to no correction
Smaller
Plus powered contact lenses produce a larger or smaller retinal image compared to spectacle lenses with the same power
Smaller
Minas powered contact lenses produce a larger or smaller retinal image compared to spectacle lenses with the same power
Larger
The accommodated demand for myopia is reduced or increased with contact lenses compared to spectacle lenses
Increased
The accommodative demand for hyperopia is reduced or increased with contact lenses compared to spectacle lenses
Reduced
The convergence demand for myopia is reduced or increased with Minas powered contact lenses compared to spectacles
Increased
The convergence demand for hyperopia is reduced or increased with plus powered contact lenses compared to spectacles
Reduced
Spherical aberration
A type of Mono chromatic aberration found in contact lenses
Transverse chromatic aberration
Red yellow and blue light focus at separate points in the vertical plane
Longitudinal chromatic aberration
Due to the dispersion properties of the glass that the wavelengths passed through different wavelengths focus at different points
Coma
A type of Mono chromatic aberration found in spectacle lenses
Contact lens magnification (CLM)
The ratio of the image generated with contact lenses divided by the image generated from spectacle lenses
Accommodative demand
The focussing required to view a near object
