2 SCL Intro

Contact lenses match the shape of the cornea, which is naturally __

Prolate

Overall Diameter (OAD)

Total diameter of lens, typically 14.0-14.5 of hydrogel/SCL

Peripheral Curve Width (PCW)

A back surface zone that aligns with flatter limbus and sclera

Optic Zone Diameter (OZD)

The central optical zone created on the back surface when a peripheral curve is added

Base Curve Radius (BCR)

Radius of curvature for OZD, may be aspheric

Is the BCR flatter or steeper than the central corneal curvature?

Flatter, 8.0-9.2

Peripheral Curve Radius

Radius of curvature for the PCW

Lenticular

A peripheral curve on the front of the lens that decreases the edge center thickness

Anterior Optic Zone (AOZ or OZ)

Diameter of zone inside the lenticular zone on anterior of lens

Power Curve or Front Curve

Provides sphere correction of the Rx, can also provide multifocal/bifocal correction

• may be the entire front surface in lower powers (no lenticular zone)

What curve provides sphere correction of the Rx?

Power or Front curve

Which do soft lens manufacturers report, the OZD (back surface) or AOZ (front surface)?

AOZ

What 3 things does the thickness of SCL influence?

1. Dk/t

2. Handling (thicker is easier to handle)

3. Movement with blink

Thickness is a function of what other parameters? (What things influence thickness of a lens)

1. Power

2. Lenticular design

More minus power = thicker center or edges?

Thicker edges

As the power increases in magnitude, thickness increases or decreases?

Increases

As diameter (OAD or OZD) increases, does thickness decrease or increase?

Increases

What power SCL are plano shape?

-2 to -3

Are plano SCL plus or minus shaped?

Plus

What powers of SCL are plus shaped?

-1 and more plus (including PL)

What SCL powers are minus shape?

-4 and more negative

Indications of spherical soft lenses

• good tear quality and quantity

• Low astigmatism

• Athletes or others where GPs will be dislodged

• Unable to adapt to GPs

• Motivated (they should want CLs)

Contraindications of spherical soft lenses

• inflammation, dry eye, or ant seg disease

• Poor hygiene (including military)

• Not motivated

• Chronic allergies/antihistamine use

• Autoimmune disease/immunocompromised

• Irregular astigmatism

• Radial keratotomy

• GPC/CL Papillary Conjunctivitis

Soft Lens Advantages

• Excellent comfort, minimal adaptation

• Part-time wear, frequent replacement possible

• Minimal corneal distortion and spectacle blur

• Dislocation uncommon

• Can fit and dispense from inventory

• Change/enhance eye color

• Therapeutic use possible

Soft lens disadvantages

• reduced VA with uncorrected cyl

• Limited durability

• Poor O2 transmission with hydrogels

• Deposit formation/GPC/CLPC

• Increased risk of bacterial infection

• More difficult to verify

• Limited parameters available