Optics 1

A lens has two meridians with powers as shown. What would be the sphere in the negative spherocylindrical form?

• -3D

• -2D

• -1D

• +3D

Answer explanation

In the power cross, the more positive meridian becomes the sphere. I this case, -2 is more positive than -3

What is the most commonly used material to make spectacles?

• Glass

• CR-39

• Polycarbonate

• Trivex

Answer explanation

CR-39 is a plastic most commonly used to make spectacles. Trivex is also a plastic more superior than polycarbonate

A patient is fully corrected at -10.00+1.00x20 with vertex distance of 1mm. What is its negative cylinder form?

• -9.00-1.00x20

• -10.00-1.00x20

• -9.00-1.00x110

• -10.00-1.00x110

Answer explanation

To convert to negative cylinder:

New Sphere: is algebraic sum of orig sphere and orig cylinder

New cylinder: just change the sign of the orig cylinder

New axis: add 90 to orig axis

How much total prism is induced if your glasses are too small and you are looking 5mm temporal to the optic center of each -6.00D lens?

• 3D

• 6D

• 12D

• 20D

Answer explanation

To calculate induced prism:

Prentice rule!

PD = h (in cm) x F (lens power)

In our case, 0.5cm x 6D = 3D per eye

Since deviation is in opposite directions (base out in each eye since looking temporally), cumulative induced prism is ADDITIVE

Which of the ff wavengths is diffracted the most by a small pupil?

• Red

• Orange

• Yellow

• Blue

Answer explanation

Longer wavelengths are diffracted more than shorter wavelengths.

Therefore,

BLUE BENDS BEST

RED SPREADS DEAD