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Medical Forum / General / Vision / January 2008Calculating Add for computer work
I made it clear to my optometrist that I would probably get less strain if I wore glasses for computer work. So he gave me what now turns out to be a reading prescription. It didn't dawn on me at the time when he said "hold this book in front of you while I put this in front of your lens", that they would be no good for computer work (unless I get much closer to the screen) My Add is +1.00 so is there a rule for working this out for computer work with a screen that's about 70cm away?  SignatureMike News > My Add is +1.00 so is there a rule for working this out for computer work > with a screen that's about 70cm away? To say your "add is +100" doesn't tell us much if we don't know what distance it's calculated for. I'd guess you held the book about 50 cm. As for the "rule", halving the add doubles the distance. If your +1.00 was measured at 20" (50cm) then +050 should give 100 cm and +075 about 70 cm. If the quarter-diopter step size forces you to choose between too much add and too little, then less is better. Especially for younger presbyopes, eg 40-45 years old. -MT, OD In message <3uGdnfI8Hpcq3AfanZ2dnUVZ_hSdnZ2d@giganews.com> at 14:06:21 on Fri, 25 Jan 2008, Mike Tyner <mtyner@mindspring.com> wrote >> My Add is +1.00 so is there a rule for working this out for computer work >> with a screen that's about 70cm away? [quoted text clipped - 4 lines] >As for the "rule", halving the add doubles the distance. If your +1.00 was >measured at 20" (50cm) then +050 should give 100 cm and +075 about 70 cm. Thank you SignatureMike News >I made it clear to my optometrist that I would probably get less strain if >I wore glasses for computer work. So he gave me what now turns out to be a [quoted text clipped - 5 lines] > My Add is +1.00 so is there a rule for working this out for computer work > with a screen that's about 70cm away? For some computer lenses like the Zeiss Gradal RD, you just give them your regular progressive Rx, and they automatically adjust it for computer use. This is typically done by adding +.5 to your distance vision and subtracting .5 from the add power (so that the reading power is actually the same as it would have been with regular progressives). This makes your distance power about the right power for computer distance (you don't get a true distance power and you cannot drive a car with these lenses). The .5 is just an example (don't recall what Zeiss uses), and sometimes you can choose between different adjustments (such as .5 and .75 ). See an optician for details. > power and you cannot drive a car with these lenses). I do it all the time. -MT > > power and you cannot drive a car with these lenses). > > I do it all the time. > > -MT So do I. My Zeiss computer glasses are more comfortable than my other pair that's supposed to provided me the needed 20/20 for driving. >So do I. My Zeiss computer glasses are more comfortable than my other >pair that's supposed to provided me the needed 20/20 for driving. Probably because your eyes have gotten a bit weaker, and you really need a new Rx with additional power in the distance area (which the computer glasses give you). If you look at Zeiss informational material (or any other vendor who sells computer glasses) they are quite clear (no pun intended) that computer glasses are not for driving (because the lens does not contain a viewing area with your distance Rx). > If you look at Zeiss informational material (or any other vendor who sells > computer glasses) they are quite clear (no pun intended) that computer > glasses are not for driving (because the lens does not contain a viewing > area with your distance Rx). I'm sure you're right about what it says, but a half diopter of blur doesn't normally reduce vision to 20/40, even at night, so there are people driving lawfully with worse vision than you get from a little extra plus. IMO there's more danger in those 1/2-inch "fashion" temples that California outlawed in 1959. -MT >> If you look at Zeiss informational material (or any other vendor who sells >> computer glasses) they are quite clear (no pun intended) that computer [quoted text clipped - 4 lines] >normally reduce vision to 20/40, even at night, so there are people driving >lawfully with worse vision than you get from a little extra plus. True, but a half diopter is a room distance lens, not a computer lens. Or as Jon Stewart might say, it's more like a gratuity, and a cheap one at that. Kidding aside, the "office" type lenses made by Zeiss and other companies put about 50% to 70% of the Add on the distance gaze. Because I don't start thinking about computer glasses until the Add is above +1.75 (assuming typical work distances and healthy eyes), that places anywhere from one, to as much as one and a half diopters of plus on the distance, more than enough to cause blurring of road signs and other distance objects. To the OP: If the +1.00 Add was for about 40cm, then you should have enough reserve accommodation to see the screen comfortably and clearly at 70cm when you look through the distance portion of the glasses, or without glasses if there is no distance Rx, sans accommodative or vergence dysfunctions. >IMO there's more danger in those 1/2-inch "fashion" temples that California >outlawed in 1959. > >-MT I didn't know that. Most folks don't seem to ever look in their mirrors anyways. In Texas, you can keep a loaded gun under the seat or in your pocket, pull up to a drive up window and buy a bottle of Jack, and until a few years ago, you could drink it and drive, as long as you were not "impaired". Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman > True, but a half diopter is a room distance lens, not a computer lens. Or > as Jon > Stewart might say, it's more like a gratuity, and a cheap one at that. But the doctor wrote +1.00 for 20 inches. That suggests the OP is 45 or less, with considerable accommodation remaining. Even at 53, I use +050 in my distance portion and VDTs are quite legible at 30 inches or so through that. Not "crisp" but not so blurry that I habitually tilt back. Even when accommodation is gone, depth-of-field and tolerance for blur allow a range. MT >>IMO there's more danger in those 1/2-inch "fashion" temples that California >>outlawed in 1959. > > I didn't know that. Most folks don't seem to ever look in their mirrors > anyways. It interferes enormously looking over your shoulder to back up, and obliterates the "corner of your eye" vision used for that 18-wheeler sneaking up in your blind spot. -MT >> True, but a half diopter is a room distance lens, not a computer lens. Or >> as Jon >> Stewart might say, it's more like a gratuity, and a cheap one at that. > >But the doctor wrote +1.00 for 20 inches. I don't think we know that. The OP said the Add was for reading. You surmised "To say your "add is +100" doesn't tell us much if we don't know what distance it's calculated for. I'd guess you held the book about 50 cm". >That suggests the OP is 45 or >less, with considerable accommodation remaining. Right. He shouldn't need computer glasses. >Even at 53, I use +050 in my distance portion and VDTs are quite legible at >30 inches or so through that. Not "crisp" but not so blurry that I >habitually tilt back. I have clients who look at the monitor for hours at a time, reporting an average monitor distance of 24". They need and want crisp. >Even when accommodation is gone, depth-of-field and >tolerance for blur allow a range. I've found that this varies from one person to the other, probably related to pupil diameter and maybe changes in the lens. A +2.50 Add client I saw yesterday could see my monitor comfortably at 25". I didn't expect that- most people struggle and have to tip their head back, shocked at how much clearer the text looks when +1.50 is placed over the glasses. Her reaction was the opposite, not much better with than without. Although she uses her computer a moderate amount of time, I didn't recommend separate glasses because she was non-symptomatic and comfortable with the existing quality of vision. BTW, my office monitor is at 32", and unless I bump the font good and plenty I see a lot of blur. My home monitor is at 25" and I don't even try to look at it with my everyday glasses. (Add is +2.25 at 40cm.) >MT >>IMO there's more danger in those 1/2-inch "fashion" temples that >California [quoted text clipped - 8 lines] > >-MT Now, if we can only get urban drivers to recognize that an automobile isn't their living room on wheels! Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman > In Texas, you can keep a loaded gun under the seat or in your pocket, pull > up to [quoted text clipped - 3 lines] > > Robert Martellaro 1. You need a license to carry a gun in Texas. 2. Regarding having a open bottle of alcohol in your car, it has been more than 6 years that this has been illegal in Texas. Mississippi still allows drivers to consume alcohol while driving (as long as the driver stays below the 0.08% blood alcohol content limit for drunk driving), and seven states (Arkansas, Connecticut, Delaware, Mississippi, Missouri, Virginia, and West Virginia) allow passengers to consume alcohol while the vehicle is in motion. However, local laws in these states may limit open containers in vehicles, as was the case is some localities in Texas prior to 2001. 3. The sale of liquor is controlled locally in Texas. More than 50 counties are completely "dry". In some areas of major cities (such as Dallas) there are no liquor stores allowed. Some localities in Texas even prohibit the sale of beer and wine in grocery and convenience stores. 4. You may thing that Texas is the wild west, but I would bet you that there are a lot less car jackings there, perhaps because criminals understand that a driver "might" have a gun. 5. Drivers are more polite in Texas than in most states, especially compared to northern states. 6. You don't know Jack about Texas. >> In Texas, you can keep a loaded gun under the seat or in your pocket, pull >> up to [quoted text clipped - 5 lines] > >1. You need a license to carry a gun in Texas. Not in your vehicle, as long as it's concealed. http://www.legis.state.tx.us/tlodocs/80R/billtext/html/HB01815F.htm >2. Regarding having a open bottle of alcohol in your car, it has been more >than 6 years that this has been illegal in Texas. Mississippi still allows [quoted text clipped - 4 lines] >motion. However, local laws in these states may limit open containers in >vehicles, as was the case is some localities in Texas prior to 2001. I said a few years. Few means not many. Six years is not many years, unless you're a sixteen year old. Why the nitpicking? >3. The sale of liquor is controlled locally in Texas. More than 50 counties >are completely "dry". In some areas of major cities (such as Dallas) there >are no liquor stores allowed. Some localities in Texas even prohibit the >sale of beer and wine in grocery and convenience stores. There are drive through liquor stores in Texas. Maybe not in every friggin town, village, and city. Is it really necessary to rebut this? >4. You may thing that Texas is the wild west, but I would bet you that there >are a lot less car jackings there, perhaps because criminals understand that >a driver "might" have a gun. Maybe. I do believe I have the right to defend myself from the bad guys, and that the laws should make it easier, not harder to do so. >5. Drivers are more polite in Texas than in most states, especially compared >to northern states. Yeah, it sure couldn't be any worse than Milwaukee, except for Chicago, where they're not rude per se, just crazy. >6. You don't know Jack about Texas. I know that what I posted is accurate. What makes me think you're from Texas? Regardless, my point wasn't to judge Texas law, it was to provide perspective to what I believe is a silly California law regarding temple widths, and that it's usually folly to try to control peoples behavior to the nth degree. Robert Martellaro ~~~~~~~~~~~~~~~~~~ Optician/Owner Roberts Optical Wauwatosa Wi. ~~~~~~~~~~~~~~~~~~ "Science is a way of trying not to fool yourself." - Richard Feynman On Jan 25, 12:56 pm, Mike <turnpike_user@turnpike_REMOVEuser.THIScomANDTHIS> wrote: > I made it clear to my optometrist that I would probably get less strain > if I wore glasses for computer work. So he gave me what now turns out [quoted text clipped - 7 lines] > -- > Mike News For most people an add of +1.00, if over the distance Rx should be clear at 70cm, clear out to 1M. Return to your optometrist with the distance to your computer in hand and have him work out the add in space with hand held lenses. You obviously have eyes that don't react in the usual way. Dr Judy |
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