As some of you may have seen in the lens ordering world, stock options are only so plentiful. When you are looking at ordering lenses in the -10.00 range stock options skip quarter powers and go by half diopters.
My question is: If you are ordering a stock lens for a script that calls for -13.25, which direction should you round? The ANSI math tells us that this IS within tolerance, so does it matter?
Thought? Concerns? Math?
Have I told you today how much I hate poly?
Generally, If I have to use stock for a power like that, I'll comp the vertex and then pick the best power to equal as close to the -13.25 as possible. If the vertex doesn't compensate, I generally will go the .25 stronger rather than weaker.
-Poly is the best substrate for coatings.
-Poly is extremely scratch resistant.
-Poly is extremely impact resistant.
-Poly is unparalleled in clarity.
-Poly is much lighter than traditional crown glass.
Like poly, you can trust me about 40% of the time.
Originally Posted by Quince
Are you saying you are purposely ordering the wrong power in a stock lens instead of grinding the lens?!?! I assume the only reason here could be cost. Did you ask the patient, or the prescriber, if they were OK with this. I would have to assume they are not. Also, ANSI gives tolerance for finished lenses vs ordered lenses. Not prescribed power vs finished power. You can't order a .25 Diopter off power. The finished lens has a .25(.265 in this case) Diopter tolerance to what you ordered. So, if you order .25 off power and the lens is manufactured .25 off power from what you ordered(within tolerance), your lens might be .50 diopters away of prescribed power.
OR it could be right on! It is best to go more minus less plus.
McAnerin- Thanks for the input! I don't have a vertex measurement to utilize, but I lean towards going stronger as well.
Kwill212- Not only does this save cost but it saves time as well as offering a better looking finished product. If the lens received is off- and therefore out of tolerance it can be rejected. This is not a new practice. There options are limited after a certain power because it makes less of a difference at this strength.
As an office that duplicates and utilized 10 year old RXs (per request by the patient), this is not out of our realm. When a patient has a problem with a quarter difference in their -13.25 script, I will happily remake it as a surfaced job. But we have yet to have that happen. We've only had to adjust a handful of times over the years, but it has been successful for us and those wearing what we've made.
Have I told you today how much I hate poly?
Been a while since I practiced in Maine (35 + years) but is there no default expiration dates for Rx's ?
Most of our doctors put a 1 year expiration date especially if they are older and have medical problems. I know some doctors put a 2 year expiration date. If we get an outside prescription that has been awhile (usually over a year), we usually call the doctors office and check to see if it's okay to use.
Contact lenses expire every year, glasses have a date one to two years out, but there is no law prohibiting it's use. Maine is unregulated (retail is not bound by optometry laws) and we are about 20/happy.
Don't get the wrong idea, most of our long-term Rx users (using the same Rx each year) still have exams. They just like a specific Rx. We thoroughly encourage bi-yearly exams to anyone wanting to reuse RXs.
I also wouldn't be surprised if the online 'boom' will make this more common practice.
Last edited by Quince; 11-28-2017 at 04:28 PM. Reason: clarification
Have I told you today how much I hate poly?
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