Contact Lens 1: SCL Parameters

Question 1

Brand

1. There are 4 main Manufacturers. What are they?

Answer 1

1. a. Alcon/Ciba
   b. Bausch + Lomb
   c. Coopervision
   d. Vistakon

Question 2

Power

1. Vertex power can be measured using a LENSOMETER in what?
2. Specified the same way as what?
3. Power varies with what?

Answer 2

1. In Air or in a WET Cell
2. As Glasses
3. with Lens Hydration

Question 3

Measuring SCL BVP in Air

1. Blot the SCL Dry with what?
2. Place CL Stop on what?
3. Place SCL on Lensometer Table with what Surface Facing away from you?
4. Determine Power how?
5. Measurement should be taken w/in how much time of the Lens being DRIED?

Answer 3

1. a PAPER TOWEL
2. on the Lensometer
3. with Posterior Lens Surface Facing away from you.
4. As you normally would
5. Within 1 Minute

Question 4

Measuring Back Vertex Power of a SCL in a Wet Cell

1. Fill Wet cell with 1 of 2 things?
2. Place what in it?
3. Place Wet Cel on lensometer table with what lens surface facing away from you?
4. Determine Power how?
5. Multiply the drum by what to get your Power? (Approximate Correction Factor)

Answer 4

1. Saline or MPS
2. Lens in it
3. With Posterior Lens surface facing away from you.
4. As you normally would
5. By 4 x’s.

Question 5

Wet Cell Measurements

1. What happens to Image Quality?
2. Conversion Factor depends on what?
   a. Greater for what?
3. What 2 things affects results?
4. Multiplies what?

Answer 5

1. It’s Much Improved
2. on Lens Water Content
   a. Greater for HIGH WATER
3. Sagittal Height and Lens Thickness
4. Measurement Error

Question 6

Base Curve

1. What is the Base Curve Radius? (BCR or BC)
2. Record in what?
   a. To what Decimal place?
3. Most manufacturers specify Base Curve how?
   a. Some do what?

Answer 6

1. Spherical Radius of Curvature of the Posterior Surface Optic Zone
2. in mm
   a. to 1 Decimal Place in SCL
3. Numerically
   a. Some use “Flat”, Median or Steep

Question 7

Base Curve (2)

1. Base curve of a lens (Spectacle or contact), is the surface that becomes the Basis from which what will be calculated?
2. Usually specified in what for Spectacles?
3. May be specified in 1 of 2 things for CLs?

Answer 7

1. the Remaining Curves will be calculated
2. in DIOPTERS
3. Diopters or in Millimeters

Question 8

BCR in mm vs. Diopters

1. BCR can be converted to mm from D and vice versa. What’s the Eqn?
2. BCR can be converted to Meters from D and vice versa

Answer 8

(n’-n)/r

n’ = 1.3375

n = 1 (air)

2. 0.3375/(r: in meters)

Question 9

Converting from MM to Diopters?

Answer 9

337.5/r (in mm)

Question 10

Converting from Diopters to MM

Answer 10

337.5/D

Question 11

Base Curve Terminology

1. Proper Terminology about Base Curves?
2. DO NOT USE what TERMS?

Answer 11

1. FLATTER or STEEPEN a base curve

2. Increasing or decreasing a base curve

Question 12

Relationship b/w BC in MM and Diopters

1. Increasing BC could mean Flattening or Steepening depending on what?

Answer 12

1. On whether u r referring to a number in millimeters or Diopters

Question 13

Verifying BCR

1. Not usually done for what?
2. Can be done using what 3 things?

Answer 13

1. for SCL
2. a. Keratometer (use Wet Cell or Modified Scale or Conversion Table)
   b. Radiuscope (Time consuming, cumbersome)
   c. Profile Matching

Question 14

Profile Matching

1. What is it?
2. Lens Steeper than Dome = ?
3. Lens Flatter than Dome = ?

Answer 14

1. Projection Magnifier, in combo w/templates of known BCR
2. –> Air Bubble (Centrally)
3. –> Edge Lift (Edges will lift AWAY from the Dome)

Question 15

Soft Lens Analyzer (Projection Magnifier)

1. Can also be used to measure what 2 things?
2. And to Examine what 2 things?

Answer 15

1. Diameter and Center Thickness

2. the Surface and Edge of the Lens

Question 16

Overall Diameter (OAD)

1. Diameter of a SCL is what?
2. Measured in mm to what?

Answer 16

1. is the LINEAR Chord from Edge to Edge of the Lens

2. in mm to 1 decimal place for SCL (Ex: 14.0)

Question 17

Verifying Diameter

1. Hand held Magnifier
   a. How do you do it?
2. Projection Magnifier: What do you do?

Answer 17

1. Blot lens DRY w/Towel, Place POSTERIOR LENS SURFACE on Scale, look thru Eyepiece at a FLUORESCENT LIGHT, Center Lens Vertically, then Read to nearest 0.1 mm
2. Lens is Placed in Wet Cell and Projected onto the Screen

Question 18

Sagittal Depth

1. What is it?

Answer 18

1. Perpendicular Distance b/w Geometric Center of the Back Lens surface and the Diameter of the Lens

Question 19

SCL Design

1. OZD = ?
2. PCW = ?
3. OAD = ?
4. in a SCL, the OAD = ?

Answer 19

1. Optic Zone Diameter
2. Peripheral Curve Width
3. Overall Diameter
4. OAD = OZD + 2PCW

Question 20

SCL Design

1. OZD is what portion of the lens?
2. Outside the OZD is what portion of the Lens?
3. Peripheral System is what?
   a. What does this help improve?
4. In a SCL, the OAD = ?

Answer 20

1. the Usable Optical Portion of the Lens
2. the Fitting Portion of the Lens, made up of Peripheral Curve(s)
3. is FLATTER than the Base curve of the lens.
   a. Improve Comfort, Control lens movement and Control Lens Centration
4. OAD = OZD + 2PCW

Question 21

Why are Peripheral Curves Flatter than Base Curves?

Answer 21

IDK. Listen to the Lecture at Slide 35 and see what she says.