ACOD WS1 Astigmatic

According to toric expression, the number on the bottom left side of the expression represents

• The cross curve on the back surface

• The base curve on the back surface

• The sphere curve on the front surface

• The base curve on the front surface

A prescription reads -2.50 / -1.75 x 60. The type of astigmatism corrected by this prescription is

• Mixed astigmatism

• Simple myopic astigmatism

• Compound myopic astigmatism

• Compound hyperopic astigmatism

A lens prescription reads -3.00 / -1.75 x 45. The 45 represents:

• The sphere power of the prescription

• The axis of the prescription

• The cylinder power of the prescription

• 
  

  The prism power of the prescription

A lens prescription reads -3.00 / -1.50 x 180. The principal powers are

• • -3.00 and -4.50

• -1.50 and -4.50

• -3.00 and 180

• 
  

  -3.00 and -1.50

Standard Axis Notation operates from 0º to 180º and involves

• Right to left movement

• Clockwise rotation

• 
  

  Left to right movement

• Anti-clockwise rotation

The lens type needed to correct an astigmatism is

• Plano-cylindrical or sphero-cylindrical

• Aspheric

• Double Aspheric

• Double Spherical

An optical cross represents

• The two principal meridians of an astigmatic lens

• One principal meridian of an astigmatic lens

• Two focal points of a astigmatic lens

• The two principal meridians of a spherical lens

In the Thin Lens Formula, the Symbol F1 stands for

• Total lens power

• Front surface power

• Formula One

• Focal Point

Changing the written expression of a prescription from plus cylinder form to minus cylinder form is known as

• Simple transposition

• Prentice’s Rule

• Snell’s Law

• 
  

  Toric transposition

A sphero-cylindrical lens can correct

• Compound myopic astigmatism

• Compound hyperopic astigmatism

• Mixed astigmatism

• 
  All of the above