NCLE Math formulas exam questions
and answers2
Vertex formula - ANSWERS-F = D/(1-dD)
Used to solve for F whether it is from the spectacle Rx to contact lens Rx or vice versa
F=converted diopter power corrected for vertex distance
D= original lens power in diopters (whether it is the contact lens Rx or spectacle Rx
d=distance in meters the lens is moved. The distance between where the current Rx sits and
where you now want it to be in relation to the front surface of the eye
when converting to Spectacle Rx to CL Rx, add plus power regardless if it is a + or - spectacle
power
Radius to diopters - ANSWERS-337.5 / radius in mm
Diopters to radius - ANSWERS-337.5 / diopters
Dk value - ANSWERS-Dk/t
T=thickness
Dk (oxygen permeability) - ANSWERS-D = diffusion coefficient of oxygen movement in a material
(how effective it it to allow oxygen to go through lens from atmosphere to eye)
K = solubility constant of oxygen in the lens material(how long it would remain in material)
and answers2
Vertex formula - ANSWERS-F = D/(1-dD)
Used to solve for F whether it is from the spectacle Rx to contact lens Rx or vice versa
F=converted diopter power corrected for vertex distance
D= original lens power in diopters (whether it is the contact lens Rx or spectacle Rx
d=distance in meters the lens is moved. The distance between where the current Rx sits and
where you now want it to be in relation to the front surface of the eye
when converting to Spectacle Rx to CL Rx, add plus power regardless if it is a + or - spectacle
power
Radius to diopters - ANSWERS-337.5 / radius in mm
Diopters to radius - ANSWERS-337.5 / diopters
Dk value - ANSWERS-Dk/t
T=thickness
Dk (oxygen permeability) - ANSWERS-D = diffusion coefficient of oxygen movement in a material
(how effective it it to allow oxygen to go through lens from atmosphere to eye)
K = solubility constant of oxygen in the lens material(how long it would remain in material)
