GP Products

Spherical, Standard & Custom

Variable Focus Corneal Lens

VFL3 lenses provide an ideal balance of distance, intermediate, and near vision.

This design provides a progressive range of focal powers enabling the presbyopic eye to selectively focus at any distance within the power range of the VFL3 optical system. These lenses are not translating bifocals but rather simultaneous multifocals. Simultaneous in that multiple images are being focused on the back of the eye at one time. The human eye and brain, working together, are capable of interpreting these multiple images. A mental selection takes place and the object being viewed comes into focus, whether at near, intermediate or far. These lenses are capable of focusing at any distance from 40 cm to 20 feet and beyond. Your patients will be able to focus on near reading tasks, or their computer screen, or an object across the street. The lens optical center must be positioned directly in front of the pupil for best results at all distances.

 

VFL3 multifocals do not have a single add power, but rather a progressive range of add powers from approximately +0.75 to +2.00. This multifocal or variable focus power range will normally satisfy the add requirements of emerging and moderate presbyopes. For advanced presbyopes, VFL 3 with HD Optics, HD-AP or HD-CAP front surface geometry will extend the total add power. 

The progressive power gradient of a VFL3 lens is derived from a progressive flattening posterior surface combined with a single spherical anterior surface. The aspheric posterior surface not only contributes to the progressive power effect but significantly influences the fitting approach required to achieve a successful lens to cornea fitting relationship. The sagittal depth of a VFL3 lens is greatly reduced due to the progressive flattening of the posterior surface. Axial edge lift increases as the posterior surface flattens. In order to offset this rapid flattening the apical radius (base curve at it's steepest point) must be fit considerably steeper than the flattest corneal meridian. Most patients are fit approximately 2.75 to 3.00 diopters steeper than the flattest corneal meridian.

 

In the example, a base curve has been selected 3.00 diopters steeper than the flat "K". A VFL3 lens fit 3.00 diopters steep will align with the intermediate and peripheral corneal surface. A small area of central clearance is characteristic of a normal VFL3 fit. This central clearance forms a significant plus tear lens between the base curve of the contact lens and the anterior surface of the cornea. This plus tear lens must be neutralized by adding an equal amount of minus power to the contact lens. An over-refraction is the most accurate way to determine the required lens power. An approximation of the anticipated lens power can be made by using normal SAM/FAP rules. This plus tear lens compensation is the reason why the power of a VFL3 lens is normally 2.25 to 2.75 diopters more minus than the patient's refractive error.

Example: 43.00@180 / 44.50@090 Keratometer

                  "K" 43.00 +3.00 = 46.00 D or 7.33mm

SAM/FAP Rules

SAM = Steeper Add Minus

FAP = Flatter Add Plus

Fitting VFL3 Lenses

Steep Fit: Unacceptable

Flat Fit: Unacceptable

Good Fit: Acceptable

 

Slight inferior position

• Pronounced central pooling

• Harsh intermediate bearing

• Inadequate peripheral clearance

• Flatter base curve indicated

Superior

• Thin pattern over pupil due to decentration

• Excessive peripheral clearance (stand-off)

• Steeper base curve indicated

Well centered

• Slight central pool

• Uniform mid-peripheral alignment

 

VFL3 Multifocal

without HD Optics

VFL3 Multifocal

with HD Optics

Conforma HD Optics

VFL3 lenses provide an ideal balance of distance, intermediate, and near vision.

In recent years Conforma has developed aspheric anterior surfaces to compliment the optics and expand the add power capability of our traditional VFL3 Multifocals. HD Optics was the first stage in development of our front surface technology. HD Optics minimizes aberrations and maximizes optical quality resulting in improved visual acuity for your patients. 

Read the HD OPTICS™ article in Contact Lens Spectrum »

 
Troubleshooting Lens Position

Select VFL 3 trial lenses based on the preceding base curve chart. VFL3 must center well to achieve best-fit and visual results. If the trial lens doesn't center or moves excessively, steepen the base curve .10mm.

 

If unable to achieve acceptable centration through the suggested corrective action below, or you would like to discuss other potential parameter changes call Conforma at: 1-800-426-1700

Lens Position:

High Riding VFL3

Superior Position

LENS

LENS

LENS

Lens Position:

Low Riding VFL3

Inferior Position

Lens Position:

Nasal/Temporal

Decentration

Lateral/Medial Position

Cause

Correction

Verify with Fluorescien & Steepen Base Curve .10mm

 

Lenticular Plus Carrier or C/N

Reduce diameter by .4mm

Add 1.0 Prism BD

Flatten Base Curve .10mm

Flat Base Curve

 

Thick Minus Edge

 

Large Diameter & Narrow Aperture

 

Corneal Topography & Steep Base Curve

Cause

Correction

Verify with Fluorescien & Steepen Base Curve .10mm

 

Lenticular Minus Carrier

Increase diameter .4mm

Verify with Fluorescien & Steepen Base Curve .10mm

Steep Base Curve

Center Thickness

Small Diameter

Flatten Base Curve

Cause

Correction

Steepen Base Curve .10mm & increase diameter .4mm 

Toric PC

Reduce diameter .4mm & steepen Base Curve .10mm

A/R Astigatism

Narrow aperture

Lens Position:

Down & In/Out

Oblique Position

LENS

Cause

Correction

Steepen Base Curve .10mm & increase diameter .4mm 

Toric PC

Oblique astigmatism

Additional Reading Materials

VFL3 Fitting Procedure Guide

Base curve computation, Select Diameter, Power Computation Peripheral Curve Selection, Trouble shooting lens position cause and corrective action.

VFL3 Fit Evaluation Guide

Central Postition, High Position, Low Position, Nasal/Temporal Position, Lens Movement and Fluoroscein Dye Pattern Evaluation.

VFL3 Over-Refraction Guide

Over-refraction procedure and examples.

 

Parameter Change Effect

Parameters

Parameter Change Effect

Base Curve:

Diameter:

Optic Zone:

Peripheral Curve:

Blends:

Center Thickness:

Edge Thickness:

To Tighten Fit

 

Steeper

Larger

Larger

Steeper

Light

Thin

Thin

To Loosen Fit

 

Flatter

Smaller

Smaller

Flatter

Heavy

Thick

Thick

 

Over Refraction Evaluation

VFL 3 Over-Refraction Procedures:

  1. Allow at least 15 minutes for VFL 3 trial lens to equilibrate. Trial lenses must center well in order to achieve an accurate over-refraction.

  2. Over-refract with phoropter to determine best binocular distance correction.

  3. Transfer distance over-refraction to a trial frame and test the patient's distance and near vision, binocularly.

  4. Add additional plus power to the trial frame, binocularly, in +0.25 increments to enhance near vision as needed. As each increment of plus is added, ask the patient to refer back to the distance chart. This will enable you to determine the maximum plus your patient will accept at distance.

  5. It is important to work in +0.25 increments in order to achieve the best near vision without overplussing distance. The near / far balance is critical to the success of your patient. Most patients will accept more minus at distance and more plus at near than should be prescribed. Your objective is to find the balance that satisfies both distance and near. Caution - If the patient's vision is plussed to an unacceptable level in order to achieve acceptable vision at near, call consultation to discuss the additional add capabilities of the VFL 3 HD-AP.

  6. Combine all add powers for each eye as follows:

 

                                  OD          OS

VFL 3 trial lens    -3.00       -3.00

Distance OR        -0.75        -1.00

Near OR               +0.25       +0.50

Power to order   -3.50        -3.50