Hi guys, Im a eyecare student and I hope you can help me with a fool question.
Its ok to use -0.5/-1 sphere in high prescriptions for a glasses to work long time on PC (60-80cm distance)? It will be more healthiest for the eye?
I have read different opinions and Im a little lost. Sorry if its not the place for this, Im pretty new as you can see hehe.
Last edited by Manu90; 05-31-2016 at 03:15 PM.
Welcome, Manu!Originally Posted by Manu90
Your question is a little difficult to answer since it's not 100% clear what you're asking. If you're meaning 'will subtracting -0.50 to -1.00 Diopters from the full add power produce the correct intermediate power for any given patient?' then the answer is "probably not."
If a patient with mature presbyopia needs a +2.50 add for 40cm, [40cm=0.4m; 1/.4m =2.50 Diopters] then for 80cm [=.8m; 1/.8m =1.25D]: a difference of -1.25D.
For 60-70cm, the range you mentioned becomes more likely, but we're still making a lot of assumptions about your patient and his/her degree of presbyopia and working accommodation. Assumptions will get us into trouble very quickly.
If you're referring to modifying a single-vision script for extended computer use, your range of -.50 to -1.00 looks very erroneous, but I won't type a novel why until you have a chance to clarify what you're looking for.
Welcome to optics! Loads of fun to learn--which is good because there's Always more to learn!
Have fun, and good luck!
Thank you very much for the great response and the welcome!
I meant the second case, a person with monofocal lenses and (-8)+ sphere who work long hours in front of the screen. As I said, I can not stop reading about it contradictory recommendations, all with questionable real basis.
Regards!
I see where you're coming from--'will subtracting power off a myopic lens help a patient at the computer?'
Your range of +0.50 to +1.00 covers the 'computer vision' anti-fatigue add powers that I'm familiar with. Typically +0.50 to +0.75, although I've heard the new Essilor 'Zen lenses' go down to as little as +0.40.
When these sorts of lenses were new, we were told not to sell them at all without a specific doctor's Rx for it. While I gather there's far less restraint in the market these days, I still prefer to tread lightly--patients without considerable presbyopia, particularly myopes, run a very high risk of disliking these lenses.
So does knowing these 'computer vision' lenses rely on a default range of add powers make it tempting to just put a default power modification on a single vision script and call them 'computer glasses?' No, not really. The patient's doctor may have some strong opinions as to whether it's warranted. They may intend the patient to use his/her accommodation more or less than a different patient. There could be a medical complication that throws our refractive assumptions out the window.
CVS is a real issue and I admire your vigilance. If the patient seems to be giving me clues that his/her distance Rx isn't going to help at the computer, I'd ask for (or take) a measurement of how far the patient is from their monitor, and give their doc a call to clarify their individual needs. The doc will appreciate you not trying to do their job. 4 times out of 5, the patient neglected to tell you some important information, or else didn't talk to the doctor at all about something s/he should have. Even if you end up with the doc writing you a revised computer script exactly as you anticipated, you helped ensure your patient's continuity of care as well as meet their vision needs.
Thank sa lot!
I routinely make SV computer eyewear at +0.50 or +0.75 over DV Rx. I like the anti-fatigue/eyezen, but if you put a full DV Rx in them they aren't very useful on desktop monitors for the same reason progressives aren't ideal for that. They key with this is determining the patient's monitor viewing distance and tolerance for DV blur, and this is simply accomplished with flippers of DV Rx. This is useful for everyone, even 20 year olds with perfect accommodation will find +0.50 for the computer immensely relaxing.
Thanks for the repply DanLiv
When you say +0.5 do you mean -5 sphere instead -5.5, in a single-vision normal glasses?
In all honesty, I'm sure Dan's process is very reliable. It's the exceptions that worry me, granted the 20-somethings will have fewer of them.
e.g. high cylinders, which are infrequently but occasionally modified by a doc when shortening a focal length. When even ODs have differing approaches of choosing to do this, or by how much, I have no desire to risk stepping into the middle of it.
If you're filling for a doc with whom you already have a trusting relationship, go for it. If not, in the absence of a prescribed computer Rx, why not make that courtesy call & start forming a new one?
It doesn't hurt the eyes to accommodate. Go ahead and read War and Peace. However, if the text looks blurred, and/or mild headaches/eye pain and fatigue, call your eye doctor.
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.
The "cleanest" method on how to Rx and add for a theoretical desktop computer is merely the "1/2 of add" i.e. "50% TF" method!
Add @ 40cm:
+1.00
+1.50
+2.00
+2.50...
gives...
Add @ "intermediate"
+0.50
+0.75
+1.00
+1.25
Simplicity itself.
But the basic reality is this: EXCEPT FOR THOSE SPECIAL PETITE FLOWERS THAT HAVE NON-AGE-RELATED ACCOMMODATIVE FATIGUE...
...People need desktop computer glasses at age 50 when they're a +2.00 add. Then they need about a +1.00D. (I like +0.75D. Is nice.) Put it in a multifocal and they'll wear them forever.
Last edited by drk; 06-01-2016 at 01:20 PM.
Drk, I love simplicity! (Actually, if that were true I'd be in the entirely wrong line of work....)
Truer to say I occasionally respect and admire simplicity. Yet back in my big box days I remember well being chastised by a prescriber for automatically cutting the add of his Px in half for his computer. Like Einstein said, 'as simple as is true, but no simpler.' I have the OD administered whip scars to suggest the 1/2 rule is too simple!
I'd be lying if I said I didn't compute intermediates myself, at least for the scripts of those doctors with whom I work closely and trust me to do it--or if all the math swooshes in 'nothing but net.' Still, I have a tape measure handy trying to find a problem...and if it was your patient I had the slightest question or intuitive unrest, you'd be getting a call or email from me on how to round it.
Back to non-presbyopes, most of the docs I talk to think like you and Robert...accommodation is to be used if they have it. If a computer intensive patient is a special petite flower, the doc ought to be in the loop before we opticians start 'treating' it.
I'd get my glasses from Dan in a heartbeat, his +0.50 would suit my middle-aged, low/moderate cyl, computer fatigued eyes just fine. I trust his competence to spot when there might be an exception to methodology. Would I trust anybody to take simple rules and run with it? Not so much.
Welcome Manu,
Since you are an eyecare student I hope you will now start using standard optical lens power notation in your future posts. Notice in all OptiBoarders' responses seen below... they all write optical Rx power to two (2) decimals.
So -0.5 needs to be written as -0.50 , and -1 to be written as -1.00. Axis is written to 3 numbers... x70 is written as x070, and x5 is written as x005. x180 is of course x180
There... we are now all on the same page and now your posts will be much easier on the eye. (That's the instructor in me coming out)
Agree completely with this
I find it interesting that we dedicate so much of our time discussing the pros and cons of Blue Blockers and where they fit in at the dispensing table when so many of our patients are experiencing CVS. The sage advice handed out; take more breaks, drink more water, divert your fixed eye from the screen to another position, and blink more. The reality is that students and tech employees have neither the time nor the inclination to follow through. Remedy, some form of multi-focal; including anti-fatigue or task specific lenses. For those non-presbyopic folk +0.50 over their distance is usually all they require. The conversation regarding specialized eyewear needs to happen and don't forget your emmetropes. Coating application discussion can then take place.
I didn't attend the funeral, but I sent a nice letter saying I approved of it. Mark Twain
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