Pleas tell how you do it
How does you fit the progressiv lenses
Pleas tell how you do it
C always
almost always
"A" unless something in the discussion with the patient suggests for the measurement to be lower. Most (maybe all?) of the progressive lens manufactures design their lenses to be measured there. Why do you drop the measurement 2-3 mm's?
To get a wider distance zone, and i almost always use progression length 15 mm
If measured directly in the center of the pupil the fit will be where the the distance rx ends, and the Int. begins. Especially for new wearers' fitting you want to place them in a green zone and have them find their own comfort placement as the go. In theory you would want them to raise their PCs and laptops to a higher level to adjust for the proper fitting technique but they rarely do. It is better to accomodate to your patients immediate needs than to risk over coaching them on how to see.
The place I actually mark is somewhere between B and C through it can be B or C (if not lower then C) and that is because of the conversion of lowering the seg height 1 mm for every 2 degrees of pantoscopic tilt. Since the average value of pantoscopic tilt that I see in the caucasian population (the vast majority of the patients that come into the office I work for) is between 6 and 8 degrees this works out to lowering the seg height by 3-4 mm. The range of the photopic pupil diameters we see are between 2-4 mm and mesopic pupil diameters of between 3-8 mm (which is dependent on age as well as other medical factors) 3-4 mm works out to be at or near the bottom of the pupil at its greatest diameter to 2 mm below the pupil during the day.
And I work backwards if panto is not in the normal range.
With very few exceptions, 'A', which is what the lens designers are asking for (center pupil) to achieve the best vision at all angles of gaze.Originally Posted by Mr.Powers
Pleas tell how you do it
We shouldn't physically lower the lens, or fitting point, just the optical center, which aligns the optical axis of the lens with the center of rotation of the eye. See...
http://www.opticampus.com/cecourse.php?url=lens_design/
Scroll down to the diagram at...
Ensure 1 mm of Optical Center Drop (H) for Every 2° of Pantoscopic Tilt
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Do you use Hoya Lenses? If you do, I would fit it "C" or lower. Most of our customers had problems when we fit the Hoya lenses "A". We fit Essilor glasses like "A" or "B", depends on the customers needs.
"A" unless something in my conversation with the patient would indicate that they do less reading/intermediate. Sunglasses for instance.
we use a lot of zeiss an they have a 6mm drop. i usually end up raising A 1.5mm Its frustrating at times as that 6mm drop is a killer.
I always request that my opticians give me A center of pupil, and if needed i will adjust it at order depending on the lens.
I don't understand how a formulaic approach to corridor length can be appropriate 'almost always'. What about behavioural considerations? I try to profile every patient I dispense in order to correctly work out how they use their spectacles.
I do as well, but it happens for me it usually winds up falling into the 15mm range as well. For disclosure, I usually am working with Auto II/III for my patients, so I have more flexibility when adjusting corridor length.
Since we do mainly Essilor lenses I fit "A" most of the time. With Hoya lenses I drop a mm.
Often I dot their previous glasses and see how they are wearing them. I see some that are too low and also too high. Interestingly, if I just ask people almost always say their current glasses are fine. But if I mark them and see they are too high or too low and then ask if they have to lower their head to see distance or if they have to raise their head to read they tell me the truth!
The correct answer is A, always according to the designers. I adjust which lens I use according to clients visual demands.Pleas tell how you do it
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"The correct answer" you are funny !
A some of the time, C occasionally for those who tend to lean back more (who wants a progressive blur when their sitting at their desk looking at the window anyway LOL).
Curiosities intent, has anyone ELSE ever fit a progressive +1-2MM above pupil center for those modern heavy computer users? I've personally had great luck with this for those who can't/won't pay for that extra pair for the office where they sit at a computer 6+ hours a day. You have to be EXTREMELY careful about posture with this method though, as you're leaving yourself little to no room for error. You have to keep in mind, the progression starts 3-5MM BELOW the fitting cross, so by fitting it center to pupil, you are technically putting the progression at B-C. For sunglasses I've fit as low as C for the fitting cross (motorcycle/professional drivers in particular) that's about it.
You must pick a frame that fits high on the bridge of your nose and as close to your face as possible and before finalizing a progressive fit, you should discuss your lifestyle needs for eye wear with your eye care professional.
Although in ages past we often fudged our fits, its increasingly risky. Many modern lenses will self destruct if not fit on center.
I have a Lab myself and work for the opticians but you should know that there are many different types of progressive lenses, some of them are short programmed which don't work with everyone.
"you should know that there are many different types of progressive lenses, some of them are short programmed which don't work with everyone"
Great to know after being a optometrist for nearly 20 years, first time i hear it
I think everybody on they "Optometrist Geek Forum" ( and that is meant in the nicest way) know that there at different types of progression on all lenses.
Best regards
Peter
What do you mean by 6mm of drop?
The progression starts 2mm below the fitting cross in all of the current Zeiss lenses.
I usually fit at C if they are a Myope, B if they are a Hyperope. I have had fairly good luck with this. When I started, I fit at A, as it is the textbook right answer, but I consistently had people preferring a lower OC in multiple progressive designs. I would fit at A only if they are a Hyperope who spends a lot of time in a intermediate/near environment- but of course this situation is better addressed by an office progressive.
After going to pretty much all Essilor digital lens we have had great success with measuring the center of the pupil. However, is there a recommendation for high hyperopes or high myopes, including which progressives in the Essilor line? That being said I do understand that lifestyle and use play a role but looking for a general rule of thumb. Thank you!
The only 6mm Zeiss thing I know of is the distance from fitting cross to lens etchings, which has nothing to do with the corridor. It's just where they mark them.
I fit @ A - again, unless there is something specific which requres compensation. I would think twice about using any supplier where I have to routinely drop fitting heights to get a positive result. I do this with every manufacturer we use, Ess, Zeis, Hoya, Shamir etc. Never had any serious issues with poor distance performance.
If I did, I would certainly inform the companies I was ordering from.
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