why can’t i see out of these glasses! · why can’t i see out of these glasses! trouble shooting...
TRANSCRIPT
WHY CAN’T I SEE OUT OF THESE GLASSES!
Trouble shooting patient complains for progressive
lenses.
David Erickson President ABO Speaker
Objectives:
Identify the most common causes of patient complaints with progressive lenses Give basic trouble shooting tips. Instruct important skills and knowledge for accurately reading progressive lenses. Choosing the right combination of lenses for the patients full range of vision needs
Little Known Facts About Progressive Lens Complaints
Cause of Complaint - Problem with the doctor's prescription – Occurrence – Rare (depending on practice)
Cause of Complaint - "Non-adapt" to progressive lens designs – Occurrence – Rare. Recommending quality
“Brand Name” lenses and Premium “Digital” Progressives will minimize this risk.
Little Known Facts About Progressive Lens Complaints
Cause of Complaint - Improper alignment of the progressive in the patients frame
– Occurrence – COMMON, but often undiagnosed.
Cause of Complaint – Lack of skill and/or knowledge of the fitting optician
– Occurrence – Occasional. Every practice needs a good optician onsite or nearby that they can refer to and consult with.
Cause of Complaint – Patient unable to adapt to a change in progressive lens design
– Occurrence – Occasional. Recommending quality “Brand Name” lenses and Premium “Digital” Progressives will minimize this risk as well.
Did you know………
Studies have shown that 80% of non- adapts can be attributed to poor fitting techniques (both measurements and frame adjustment) as well as lens selection.
Remember….
Always assess the patients old pair of glasses, as the answer may be hidden there. Look for differences in lens design, measurements, frame adjustment etc.
Order Accuracy…a suggested checklist
- Locate the engravings – Check the markings against the chart –
proper centration/layout – Check the fitting height – Check pupillary distances – Use of a lensometer to verify the lenses -
distance first! – lens and coating quality inspection
Specific areas for lens verification are: -Distance Power Verification Circle (used to check Distance power and axis ONLY, Not prism)
-Near Power Verification Circle -Prism Reference Point (used to check for prismatic imbalance only)
Accurate identification of specific areas for progressive lens verification is VERY IMPORTANT!
Power varies in a progressive lens depending on where
you read it. That’s why we call it progressive!
+5.00 PLANO -5.00
Sample Progressive Lens Alignment Chart
Once the markings are accurately spotted use a lens alignment chart to check that fitting cross matches the
patient’s MONOCULAR PD.
Also check the alignment of the progressive in the frame
When properly aligned the progressive markings in a frame will be in a straight line.
If Patient has a split seg ht they will be parallel
“I can only read out of 1 lens”
“I have to move my head to read out of either lens”
“I can’t see out of the distance OR close-up
Distance Power Verification Circle
Near Power Verification Circle
NOTES ON NEUTRALIZING THE READING ZONE OF PROGRESSIVES
The effect of lens tilt can be demonstrated in the lensometer. First, clamp the lens and make a measurement of near power (the result will usually be somewhat “weak,” especially with higher ADDs). Now measure the lens again, but instead of clamping the lens tilt it back to its approximate position when worn – correct Rx will be focused. (Progressive lens addition marks are integrated into the lens molds, if the verification says that it’s a 2.00 add, you can bet it is)
This is a function of Martin’s Tilt formula - as tilt is increased, so will the effect sphere power and induced astigmatism.
Prism Reference Point
Trouble Shooting Frame Adjustment
Pantoscopic Tilt Face Form Vertex Distance
The optical axis of the lens is a line perpendicular to the surfaces of the lens...
...ideally, it should pass through the center of rotation of the eye
Most fits require about 8-12º of pantoscopic tilt to achieve this...
...2º of pantoscopic tilt is required for each mm of decentration
Incorrect pantoscopic tilt creates unwanted astigmatism throughout the lens...
...the tilt also affects the perceived height of the progression
+2º tilt = -1mm height -2º tilt = +1mm height
Faceform (or “wrap”) also determines the relationship of optical and visual axes...
...most frames have a slight amount of “positive” wrap
Although wrap does move the optical axis, it also brings the lens periphery closer...
...if the measurements are accurate, increasing wrap may widen the distance field
Negative wrap should always be avoided as it will give the sensation of extremely narrow fields
Vertex distance should be kept as short as possible...
...a vertex distance of “0mm” eliminates most all optical aberrations
Longer vertex distances also narrow perception of fields...
...decreasing Vertex Distance reduces the area of the lens traversed during eye movements
Lifestyle Factors and Lens Choices
Every pair of glasses involves compromises when correcting presbyopia. It is impossible to address every possible vision need along with every possible light condition with a single pair of glasses. Consider recommending a “system” of eyewear to address multiple needs. Options include but are not limited to: Computer (intermediate/near) lenses, Polarized Sun Lenses, SV readers for the bedroom, etc.. The Doctor should consider writing an RX on more than one script for each need. Many patients believe that they can only get 1 pair of glasses because they only have 1 RX. Progressive lenses are a tool, Make sure to recommend that the patient has the right tool for every vision task that they do.
