# Optical Forums > Progressive Lens Discussion Forum >  The Office Lens Experiments

## AndyOptom

Good day :)

About two years back, I noticed that the local practitioners were apparently not too keen on dispensing occupational multifocals. Deciding that this would be a decent means of building up a client base, I set about calling up the labs and obtaining more information regarding occupational PALs and also occupational lens fitting in general.

The problem was, most of my lab techs were very cooperative, to the point whereby I was swamped with information and could not pick between lenses. Addition, degression, inset, variable corridors, working distance, induced prism... I'm sure most of you would know how I felt!

So I decided to cut some deals here and there, and put my theoretical knowledge of a few occupational PALs to the test: hypothetically, if a practitioner understands the design of a lens, modifying the Rx submitted to the supplier along with the fitting can convert the lens into a 'normal' PAL... which is what I did with my own prescription. Two years later, here is a current list of my converted office lenses - I hope my observations are of use to someone out there :)

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My Rx:

OD -4.00/-2.00x180 (6/6)
OS -6.25/-1.00x180 (6/6)

From here, I expected all my PALs to present with more swim on the right eye. For control purposes, all of them were ordered to produce an addition of +0.75.

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Lenses used:

Zeiss Office Lens (full Rx on top, add +0.75)
Nikon Home & Office (full Rx on top, add +0.75)
Free form desk lens (from a local lab - full Rx on top, add +0.75)
Sola Access (worn over my CL, plano on top, add +0.75)

And a pair of FT-28 with a blue coat for my music practice, which I shall describe briefly as follows.

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Results:

Zeiss Office Lens - The most noticeable swim and addition progression of all my lenses. Balanced zone width from top to bottom, can function as a general use PAL well enough until the Add reaches +1.50 (from customer feedback). No peripheral distortion above the fitting cross.

Nikon Home & Office - Feels almost like SV sideways and also vertically. Slightly narrower zones than the Zeiss. Cannot be used as a general use PAL since even with Add +0.75, above the fitting cross there is slight temporal blurriness.

Free form desk lens - I suspect this is a design modified from the old Asahi Optical, Pentax, and/or Kodak designs. Feels similar to the Nikon, but stopped using it due to sloppy lab workmanship and also the lab consistently delivering the wrong Rx (by their own admission).

Sola Access - Wanted to try out this golden oldie, and it didn't disappoint. A little hard on the distortion/swim, but fantastic width on the top/bottom. Negligible corridor width, but I've not had a single dissatisfied customer with this one. Have also used it as a 'beginner' PAL for those customers with smaller frames.

Bifocals FT-28 - I play music as a hobby, and since the music stand is on my right and off to the side about 1.5 feet away from me... suffice to say, I usually swap to bifocals if I'm in an Addition mood and it's time to practice on the trombone. Can still see the notes well enough for now, but my Add is a measly +0.75; those customers of mine who are musicians have appreciated the heads-up, and sometimes the switch to bifocals.

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Overall, what I've observed from my own wearing of these lenses and customer feedback on others is that occupational PALs tend to follow three distinct patterns:

- Balanced width from top to bottom (Nikon Home & Office, Hoya TACT/Workstyle, and arguably Sola Access though it's more an hourglass)
- Barrel design with wider middle, narrower top/bottom, mild swim at upper corners (Zeiss Office Lens, Varilux Computer, Tokai Resonas Presso)
- Inverted 'T' with distortion at the upper corners (Nikon Soltes/Online, Tokai Largo, Seiko PC, you could fit Access this way as well)

... and an occupational bifocal is whatever you make of it, haha  :Tongue: 

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So, will be continuing to fit my office lenses to a customer base which seem to appreciate them more than their PALs, for the most part! All my experimenting with lenses has been hugely entertaining, and it's also nice knowing that regardless of the manufacturer's intended design, I can usually obtain an alternate clinical outcome by modifying the Rx and fitting on the order forms  :Wink: 

A gem of advice I got from these boards was to convert normal PALs into office lenses: had a few hiccups initially, but now it's smooth sailing, and of course, it's hard to beat the intermediate clear zone on a converted PAL. I tend to like using Nikon/Hoya/Seiko/Sola for these, since they do produce rather flat lenses for an Rx which is actually over-plussed. Just need to watch the corridor lengths and insets.

... some of the nearby shops have not been amused at eating a pair or several when a patient of mine goes by and they ordered the same lenses without being aware of the need to modify the submitted Rx and/or fitting.

Have a good day, folks!

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## AndyOptom

And a quick skim through my mental notes on occupational PALs reminded me of the following:

- Fitting within the corridor

Most occupational PALs are literally fit in the middle of the corridor. That is to say, the lens Rx continues to change above the fitting point (sometimes to the extent of achieving the full distance Rx). I usually think of these as 'corridor designs', and further categorise them as 'complete' or 'partial' depending on whether or not the complete distance Rx is reached.

E.g. complete corridor: Hoya TACT/Workstyle, Nikon Home & Office, Zeiss Office Lens, Tokai Resonas Presso, Varilux Computer

E.g. partial corridor: Hoya TACT/Workstyle, Nikon Soltes/Online, Tokai Largo, Seiko PC, Sola Access

* TACT/Workstyle could be either depending on which variant you order (4 meters or 2 meters).

Note that a 'partial corridor' lens can also contain a patient's complete Rx if the degression matches their addition. So if you're thinking of converting an office lens into a patient's complete Rx, start with the partial instead of the complete designs. Many of the partial designs also tend to have distortion towards the upper temporal corners of the lens, presumably to prevent practitioners from using them instead of actual PALs (which naturally cost more...)

- Posture and near zone width

I've heard of, and had, patients who were told that they wouldn't have to look as far downwards with an occupational PAL to read. This is not always true, since if you look at the layout charts, most of them still have a corridor length of about 10 mm between the fitting cross to the near circle. So your patient STILL needs to look 10 mm down to get to their full addition, although I'm certain it's a much more comfortable 10 mm than a 10 mm corridor covering their full Add!

So it is noteworthy that when fitting occupational PALs, your promises on what you can deliver should vary with the design. While the near zone width is usually wider than an equivalent progressive's, it is good to keep in mind that many occupational PALs tend to use softer designs, which naturally could affect the perceived near zone width.

In this regard, it is useful to know which designs are bottom-heavy and top-heavy, which would offer wider near and intermediate vision zones, respectively:

E.g. wider near: Sola Access, Nikon Soltes/Online, Tokai Largo, Seiko PC

E.g. wider intermediate: Sola Access, Nikon Soltes/Online, Hoya TACT/Workstyle, Tokai Resonas Presso, Zeiss Office Lens, Varilux Computer

* Sola Access/Nikon Soltes can be either depending on how the fitting height is specified. Access has one fitting point that can be moved, whereas Soltes actually can be edged using either the PRP or the dot found 4 mm above and 2 mm temporal to it (the PRP is for edging using the near PD, and the distance PD can be used if edging with the dot as your blocking point).

- A real bargain buy (?)

Most suppliers tell practitioners that swim is reduced as we ascend the price and design ladder for progressive designs. However, while most labs have numerous progressives for general use, there is rarely more than one occupational PAL design.

Logically, the supplier would have to ensure that the discrepancy in swim between the occupational PAL and their best existing progressive is not so huge that a patient wearing said best progressive would be dissatisfied with the occupational PAL. Which means the occupational PAL should in terms of swim rival the top two progressives offered by a supplier, at the very least. When you look at their price compared to the premium progressives, they may indeed be a best buy when we consider this apparent mismatch of price and design! :P

Conversely, it may also be possible - and it HAS happened to some of my patients - for such a situation to occur whereby a patient feels less swim with the occupational PAL than the actual progressive (if the progressive fitted is an entry-level or mid-range design). This could easily be dismissed as a consequence of the reduced progression below the fitting cross, though, so it's not of great signficance in my book.

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## ThatOneGuy

What do patients appreciate about them?

Virtually any benefit that I'm understanding by reading through your post can be obtained through other means, so I'm curious to understand what the benefit is.

Also, wouldn't not fitting to manufacturer specs (i.e. modifying the rx) mean that you are either a)modifying the written Rx [since you can't use the written rx on those products to obtain a full time use pair], or b)over +ing the rx by having an improper fitting product? Why not simply use a lens design that is made to optimize the target field of view instead of screwing around with potentially providing patients with the wrong rx?

I THINK I understand your goal in trying this, but if I understand COMPLETELY, then it seems to me that the endeavor is based on a misunderstanding of the purpose behind any given lens design.

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## LaraBond

AndyOptom,

Congratulations! I am all for having flexible and innovative approach. It is all about making people's life easier, especially those with astigmatism/prisms, who can not adapt.

I use office lenses instead of PALs too for the non-adapt patients. I used only Essilor Computer 2V and Essilor Interview for this purpose - both seem similar but with different adds. I specify distance PD instead of near PD and drop the fitting cross slightly to give better distance field of vision. How much do you drop the fitting cross by?

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## AndyOptom

@ ThatOneGuy - Well, the bulk of my customers who end up purchasing an office lens are those who complained of a) the postural issues you might expect when trying to use a normal PAL to view a desktop monitor, and/or b) prefer to just wear their glasses when indoors and do not really require their distance Rx (e.g. hyperopes).

What you say is very true in that these benefits are more easily obtained with designs intended to correct these problems to begin with.

However, I do get cases as follows, in which case I sometimes put my thinking cap on:

- Customers insist on buying a particular lens brand since they've decided to stick with that brand for whatever reason (e.g. the photographer who only uses Zeiss lenses for his cameras AND his spectacles)

- Or the reverse, customers who dislike particular brands so much they wouldn't wear those lenses again if you paid them to.

- Budget issues with the customer.

- Customer is already wearing lenses from a particular lab, so I'd start fitting something as close to their current lens design as possible. If the occupational PAL offered by, say, Nikon does not accommodate the intermediate range desired by the customer without modification, why not modify it?

- Lab restrictions sometimes, such as when one of the local labs tells me their free form surfacing machine is temporarily non-functional, etc.

- It allows me to boycott a lab if they start showing consistently sloppy workmanship without compromising the types of lenses I can offer my customers.

- ... and this is frankly the flimsiest reason of all! In that I sometimes get bored and/or curious at work XD

All customers who request it are given a printed copy of their prescription without any questions, even if they called and told me they were heading elsewhere for their next pair of glasses. And barring a practitioner who outright tries to duplicate the Rx from focimeter readings, I don't see how this is potentially providing a wrong Rx to customers (which would then be the case with all occupational PALs) :)

End of the day, design specs non-withstanding, lenses are little pieces of plastic/glass that were shaped following the laws of optics - I certainly believe that if those laws remain as the fundamentals behind the fitting and the wearer has comfortable, clear vision for their intended usage of the lens, it's as valid and proper a fitting as any.

And yes, I modify the Rx/fitting parameters on the order form. E.g. I might over/under plus the Rx, or order with a decentered PD/height after I've accounted for the inset/corridor length/etc. Whatever I do to that order form, the end result is still based on what the customer expects the lens to do for them.

@ LaraBond - I rarely do it anymore since for higher addition there tends to be some narrowing of the distance portion of the lens (a safety hazard for many, especially drivers). But when I do, I calculate the drop in height based on the specific design and plus progression on the lens.

I rarely ever encounter a PAL non-adapt, though - perhaps just 1 in 30 pairs of PALs sold. Maybe it's because if a customer wants a segmented multifocal, I give it to them, and first-timers for PALs are briefed thoroughly. Most of the apparent non-adapts get used to it within a week or so, so the actual number of times I've had to switch them out of progressives is still rather small :P

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## LaraBond

Currently comparing office lenses. Can anybody tell the difference between these Essilor lenses: Computer 2V, Interview 0.8 & 1.3, Anti-Fatigue, EyeZen 0.8 and Digitime. 

Used Computer 2V in the past, but it is only available in 1.5 now. Also used Interview but, again, has limited materials options and both lenses will soon be phased out I was told. Hence looking for an updated version with no or minimal swim effect for a PAL non-adapt. One to use for far/intermediate vision - similar to 'blended bifocals' type, another as a computer/reading pair. 

Was thinking of getting EyeZen lens but don't like the blue Prevenzia coating - colours look darker and creamier.

Can anybody tell technical differences such as fitting heights, where progression starts and ends, is there convergence for reading area. Lens maps would be ideal.

Perhaps, other manufacturers and lenses can be recommended? No 'normal' varifocals please, this is for PAL non-adapts.

Many thanks

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## AndyOptom

If you're trying to solve a PAL non-adapt problem by changing designs, you need to first understand *why* they could not adapt to the PAL. Otherwise, 'normal' PAL or not, your refitting might still go nowhere.

The technical stuff you requested is relevant, yes, but it would be more practical to first identify the cause of your non-adapts :)

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## LaraBond

These problems have been identified, and among them are high/different astigmatism, one lazy/one dominant eye, etc. The fact is that Computer 2V and Interview worked very well for them in the past , that's why I am trying to find similar products. It won't hurt though if I have good understanding how they are made to be able compare to those.

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## AndyOptom

With regards to those issues you've mentioned:

- High cylinders will typically cause more swim regardless of the design, but I've had appreciable feedback for the softer designs by Nikon/Seiko/Hoya/Tokai (progressives and also office lenses)

- Lazy/dominant eyes can be tricky since the so-called lazy eye might still retain enough binocularity to trigger headaches if the balance lens is not done properly. Would suggest refining the monocular Rx to the best possible VA, comparing it to the current Rx for the eye, and then proceeding from there.

Computer 2V/Interview are not available locally, cannot comment on them, myself. So I would suggest asking the patients what exactly felt good about those lenses. From their feedback, you should be able to deduce if it's a design difference, fitting difference, etc., and choose an appropriate lens. e.g. if the lenses worked well due to softer swim, almost anything by Hoya/Seiko/Nikon/Tokai should be decent.

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## davidscarlet

Around two years back, I saw that the neighborhood experts were obviously not very excited about administering word related multifocals.

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## Chris Ryser

> Perhaps, other manufacturers and lenses can be recommended? No 'normal' varifocals please, this is for PAL non-adapts.



I am not a PAL non adapt, I am just a no PAL lover and enthusiast. I have several pairs of PALs and might wear them occasionally on some dress up occasion.

When working 10 hours a day on my computer they would drive me nuts and I really prefer a good ST35 to have 2 clear vision areas and I use many of them that I have accumulated over the years.

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## golfnut

Has anyone experimented with converting some of the anti fatigue lenses for cpu, certainly you would be slightly limited because of the addition but would work for quite a few...or the shamir duo would be a great alternative to a lined bifocal..

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## Quince

I have a set of Essilor Anti-Fatigue(+0.60), Hoya Sync 8(+0.88), and Identity Optical's Serenity Now (+0.75). The Serenity Now is by far my favorite, probably due to the fact that my actual Rx calls for +0.75, but all pairs are mainly used for computer. I did not comp my Rx because the DVO is so ridiculously minimal, but AF lenses are my go-to. Love, love, love em'!

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## AndyOptom

For those enquiring about converting anti-fatigue designs into office lenses, I would agree that the limited addition options leave few options... but this is not so much a limiting factor as is the variable distance from the fitting cross to the full Add! Notice that most designs save for Hoya's tend to utilise differing lengths from the fitting cross to the full Add depending on your distance Rx and fitting height (I will not use the term 'corridor' or 'umbilic' since there isn't a true one here, so to speak...). So your near Rx could easily be compromised on these.

Anyway, more results from my current batch of office lens experiments! More to observations and customer feedback this time, specifically with regards to manually converting general purpose PALs into intermediate-near prorgessives.

- Back surface addition designs seem to work best if the distance Rx is minus, even AFTER you do your conversion to intermediate Rx at the top half. e.g. distance Rx is -3.00, Add +2.00, and the lens was fitted for intermediate-near as -2.00 on top with Add +1.00.

- Similarly, front surface designs, which I usually favour for hyperopes, seem to work appreciably well for low myopes whose intermediate Rx is a low plus. e.g. distance -0.50, Add +2.00, where the intermediate-near was fitted as +0.50 with Add +1.00.

- When converting general purpose PALs, it is better to fit 'backwards', with reference to the reading zones. I measure the distance and near mono PDs, then I check the PAL designs available to me based on near inset (assuming fixed inset). By adding the inset to the near PDs, I see which PAL design offers reading zones aligned with the near PD and yet gets as close to the distance PD as possible. A must especially for hyperopes. Mirror trick works as well.

- Regarding front/dual addition designs: I am leaning more and more towards these for occupational PAL conversions, as patient feedback and adaptation has been noticeably positive as compared to when I started off using back surface designs (ostensibly for the wider near zones). Which leads to the next point...

- ... I have said this before, will say it again! I find it works better when I explain occupational multifocals as being better for near working posture as opposed to wider reading zones. While the width of the intermediate and/or near usually are superior to a full-Rx PAL, the postural advantage is much more obvious for the patient. This is especially true when you consider that most PAL conversions would be a step or two downward (e.g. patient is wearing Physio, and the converted lens is a Comfort), so the PAL design might already alter the zone width. But of course, the occupational progressive will beat the full-Rx PAL for ergonomics hands down, if fitted correctly.

- Again! If the customer wants a wider near, fit an actual office lens suited to that (one of the 'inverted T' designs such as Nikon Online, Seiko PC Wide, Tokai Largo, Sola Access, etc), or fit them with a segmented multifocal (as I'm sure Mr. Ryser would agree). I even use executive bifocals for maximal reading zone area, and the customers have been very satisfied with the results (a blue coat or mild tint helped to mask the line's appearance).

- For converting PALs into occupational progressives, the usual correlation between corridor length and panto applies: more panto, shorter corridor to reduce the wearer's required downgaze for reading. The expected increase in swim should not be of great significance as these lenses are mainly used at a desk, and perhaps just for limited indoor mobility.

- Fitting inverted multifocals with the reading on top and intermediate at bottom: either use zero inset designs, or flip a segmented multifocal. Very difficult for the wearer to adapt to the inverted corridors if at all, and the only time I did fit an inverted progressive, I resorted to a short corridor with front surface addition (since the eyes can't roll up as much as they can look down). Frame had a huge B (40 mm), with 22 mm above the pupil center when the patient was gazing straight ahead. PDs were fitted 'backwards' (see one of the previous points). Patient was happy with the result, but noticed that he needed to avoid tipping his chin down as the swim became rather noticeable.

- For multifocals mounted at an oblique angle or sideways (e.g. for artists, musicians, etc) stick to segmented multifocals or zero inset designs. Best to get the patient to bring their easel/music stand/etc. for simulation of their actual viewing situation.

- Segmented multifocals beat PALs for wearers who are VERY mobile at work (teachers, nurses, etc.) due to their lack of swim. The reduced Add they are wearing for the occupational multifocal sometimes allows for the lack of a progression to slip by almost unnoticed.

- For materials: as most occupational lenses are overplussed on one end and reading Rx at the other, thickness is not usually a major concern. My usual materials for these lens conversions would be 1.50/1.56, 1.60, Trivex, and occasionally polycarbonate (for the higher Rx patients who request impact resistance). I rarely have to go beyond 1.60 due to the relatively lower Rx range at hand, but otherwise, I do fit a fair amount of 1.70/1.74 (rarely ever 1.67). For lenses I sell as impact-resistant, I usually request the labs to make the thinnest part 3.0 mm (center for minus, edge for plus). Patients are advised that a proper impact resistant lens has to be of adequate thickness to meet industrial standards, and I do not refer to lenses not ordered to fit these criteria as 'impact resistant'.

- All prism orders are either 1.50/1.56, 1.60, 1.70, or Trivex. No polycarbonate, 1.67, or 1.74. I try to maximise the Abbe since these lenses are expected to perform off-center, and low Abbe just messes with the underlying condition. As with impact resistance, I make the call on this, and expect them to trust my professional opinion on the matter.

- Coatings: usually a blue coat as the patients report more comfort when using VDUs, although those who need fine colour perception (designers, doctors, chemists, etc.) usually receive normal AR or even uncoated lenses subject to their working environment. All lenses I sell as impact resistant or for working environments featuring heat/fume exposure are uncoated. Have yet to do a glass multifocal, though!

End of the day, do bear in mind that the actual office lens designs are themselves decent products, but sometimes fall short - all these observations were intended for those 'rare' occasions. As Mr. Martellaro has pointed out repeatedly, multiple monitors or wider working spaces are becoming more common, and I do feel office lens designs have not caught up to this yet.

Sorry for the long post, but I do love occupational fitting, and I sincerely believe this branch of dispensing has not yet reached its full potential! Most of the local ECPs seem less inclined to fit these lenses, or show a shocking lack of knowledge - as well as initiative in seeking understanding of these things - for handling them.

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