Lens 1 Final Exam Showdown

Properties of Lenses and Focal Length

100

This lens converges light

Plus lens

200

This lens produces a virtual image

Minus Lens

300

This lens increases in power as it moves away from the eye

Plus lens

400

This lens decreases power as it moves away from the eye

Minus Lens

500

The focal length in cm of a 50D lens is?

2cm

Astigmatism and Optical Cross

100

This condition can be attributed to the cornea being more oval shaped than circular resulting in two focal points

Astigmatism

200

This ongoing condition resulting in the thinning of the cornea causing a bulge known as a "cone" and may eventual require a corneal transplant is?

Keratoconus

300

This condition of the eye is the result of the meridians being greater or less than 90 degrees

irregular astigmatism

400

This diagram is used to show the two main meridians and the cylinder power

Optical Cross

500

Opticians and Optometrists must transpose prescriptions given by Ophthalmologists into the following type of prescription format

Minus Cylinder Format

Ophthalmic Lens Prescription

100

This is the curve around which all other curves are based

Base Curve

200

This is the formula that demonstrates the relationship between the front and back curves of the lens to achieve the final prescription

Nominal Lens Formula

300

Vogels rule states that for plus spherical lenses you must?

Add +6.00D

400

To achieve the base curve of a spherocylinder lens what is the first thing you need to do after you transpose the prescription?

Get the spherical equivalent 

500

The best base curve for the following Rx is?

-4.00 -2.00 x 180?

+3.50

Abbe, Spec Grav, Index of Refraction

100

This designation describes the density of a material and it's relationship to light dispersion 

Abbe Number

200

This designation describes the weight of a material

Specific Gravity

300

This designation describes the behavior of light as it moves through a material and the way it will bend or refract. 

Index of Refraction 

400

This material has an index of refraction of 1.53

Crown Glass

500

This material has the lowest Abbe value

Hi-Index Glass

Lens Materials

100

This was the first material used for lenses

Glass

200

This material was developed by the military and is known for its low specific gravity and tensile strength

Trivex

300

This material is incredibly dense and therefore lenses made with it can be thin but often requires anti-reflective coatings

Hi-Index Plastic

400

This process involves molten salt and results in an ion exchange which results in a strong bond between glass molecules 

Chemical Tempering

500

This element is used to tint glass and turns red when it cools

Gold