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a
Expert Advice on Progressive Lenses
Carl Zeiss Progressive lenses show a nearly 100% success rate. However, even with Zeiss GT2 you will occasionally have a patient that cannot adapt to progressives. The reason for this can be quite diverse. The suggestions in the following trouble shooting guide are designed to find out the real cause of the problem, solve it and satisfy your customer.
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First Step - General Evaluation
Always check the following
a
 Fit of the frame
a
 Prescription / optical power of distance and near zone
a
 Height measurement
a
 Frame tilt
a
 Corneal vertex distance
a
 Inter-pupillary distance (PD)
a
 Prismatic balance (R / L) in prismatic measurement point
a
Where does the problem occur
a
In the distance zone
a
In a certain area of the lens
a
In the intermediate zone
a
Across the entire lens
a
In the near zone
 
When does the problem occur
a
During day or night
a
During a hobby activity
a
While driving
a
At work
a
During a sport

After evaluation of these issues refer to the next steps for recommended solutions.
   
Second Step – Detailed Evaluation and Problem Solution
 

Issues concerning the DISTANCE ZONE

Problem: Blurred vision when standing. Patient has to tilt head down to see clearly.
Everything clear when sitting.
Cause: Solution:
a
 Error in vertical fitting height (too high).
b
 Check vertical height measurement for accuracy*.
       
Problem: Marked improvements occur in distance vision when frame is tilted.
Cause: Solution:
a
 Patient has uncorrected / under corrected astigmatism.
b
 If necessary, recommend new refraction with special emphasis on the cylinder.
a
 Cylinder axis is off.
b
 If necessary, recommend new refraction with special emphasis on the cylinder axis.
   
 
a · Error in vertical fitting height (too high).
b
 Check vertical height measurement for accuracy*.
Problem: Vision good through center, poor through periphery
Cause: Solution:
a
 Patient is overcorrected for distance vision (too much plus / too little minus).
b
 If necessary, recommend new refraction with special emphasis on the distance power.
a
 Patient has uncorrected / under corrected astigmatism.
b
 If necessary, recommend new refraction with special emphasis on the cylinder.
a
 Error in vertical fitting height (too high).
b
 Check vertical height measurement for accuracy*.
a Corneal vertex distance is too small
b
 Check corneal vertex distance (recommended: 12mm to 16mm).
Problem: Patient locates certain area on the lens where he can see more clearly
Cause: Solution:
a
 Distance prescription is off
b
 Recommend new refraction with special emphasis on the distance power.

 

Issues concerning the PROGRESSIVE ZONE

Problem: Crisp vision through progressive zone of one lens only
Cause: Solution:
a
 Error in vertical fitting height (too high).
b
 Check vertical height measurement for accuracy*.
       
Problem: Marked improvements occur in distance vision when frame is tilted.
Cause: Solution:
a
 Patient has uncorrected / under corrected astigmatism.
b
 If necessary, recommend new refraction with special emphasis on the cylinder.
a
 Patient needs prismatic prescription.
b
 Recommend new refraction with special emphasis on binocular testing.
a
 Patient needs different near powers for both eyes.
b
 If necessary, recommend new refraction with special emphasis on the near
power.
a
 · Error in centration (horizontal and / or vertical).
b
 Check horizontal and vertical measurements for accuracy*.
Problem: Crisp distance vision through progressive zone rather than through distance portion
Cause: Solution:
a
 Patient is overcorrected for distance vision (too much plus / too little minus).
b
 If necessary, recommend new refraction with special emphasis on the distance power.
a
 Patient has uncorrected / under corrected astigmatism.
b
 If necessary, recommend new refraction with special emphasis on the cylinder.
Problem: Intermediate field of vision appears to be too small
Cause: Solution:
a
 Addition is too strong.
b
 If necessary, recommend new refraction with special emphasis on the near
power.
a
 Patient needs prismatic prescription.
b
 Recommend new refraction with special emphasis on binocular testing.
a
 Error in horizontal centration.
b
 Check horizontal measurement for accuracy*.
a
 Corneal vertex distance is too large.
b
 Check corneal vertex distance (recommended: 12mm to 16mm).
a
 Frame tilt is too small.
b
 Check frame tilt (recommended: 8° to 12°).
 

Issues concerning the NEAR ZONE

Problem: Field of near vision appears to be too small (too narrow)
Cause: Solution:
a
 Addition is too strong, patient is reading in the progressive zone.
b
 If necessary, recommend new refraction with special emphasis on the near
power
a
 Error in vertical fitting height (too low).
b
 Check vertical height measurement for accuracy*.
a
 Corneal vertex distance is too large.
b
 Check corneal vertex distance (recommended: 12mm to 16mm).
a
 Frame tilt is too small.
b
 Check frame tilt (recommended: 8° to 12°).
Problem: Wide field of vision monocularly, restricted binocularly
Cause: Solution:
a
 Patient needs prismatic prescription.
b
 Recommend new refraction with special emphasis on binocular testing.
a
 Error in horizontal centration.
b
 Check horizontal measurement for accuracy*.
* Fitting cross and center of pupils have to be in coincidence when patient looks horizontally straight ahead.