phoropters vs wavefront

[noughtme]

i will preface my questions by stating i am merely a consumer of corrective lenses and not in the eye care profession, but i was wondering why there hasn't been more discussion here about the wavefront system as a replacement for phoropters for general diagnostic and prescriptive purposes (and not just with regards to laser eye surgery)?

ever since my first experience with the phoropter, i've found them to be a frustrating and clunky device. i can never tell whether a or b is more clear. ignoring higher order aberrations, which i understand can only be corrected surgically or MAYBE with contact lenses) does the wavefront system provide a better measurement of spherical and cylindrical aberrations?

also, why is the precision of phoropters limited to 1/4 of a diopter? (ignore the following question if it's stupid) why is it not possible to have something that's continuously adjustable, by the patient, so they can just turn the knob until everything is clear?

[Ory]

Ah, so many answers......


I've seen a lot of wavefront results converted into spectacle prescription form. Just for fun I've put them in front of my patients on occasion and found they don't always see better. There's a lot to be said for subjective responses.

An objective test of acuity works by using light reflected off the retina. The light reflected is from a different layer that where light is absorbed and turned into visual information so there is an inherent error there.

Wavefront certainly can give better than average results however. iZon is pushing this idea by putting aberrometers into offices and having people order (very expensive) wavefront-guided lenses. Currently this is a niche market because most people aren't willing to pay that kind of money. I'm sure it will become more mainstream in the future.

When you can't tell the difference between lenses in the phoropter you're actually almost done. By the end we're splitting hairs about what gives you the best acuity. A lot of research has shown that the average person has a just noticable difference (JND) of more than 0.25D so measuring in 0.25D steps is plenty accurate enough for the typical person. We can fine-tune to 0.125D steps if we really want to but it is usually pointless.

A continuously adjustable system would be difficult to build first off. The greater concern however is the under-45 set who constantly want more myopia correction (or less hyperopia correction) than they need. Everything becomes smaller but the contrast looks sharper. If we actually gave out that prescription the patient would likely get headaches and blurry vision on occasion.

Wow, long post. Hope this answers a few questions for you!

[noughtme]

thanks a lot for your detailed and lengthy response. it was very helpful in clearing up the questions i had (and probably saved me a few days worth of googling). you've also helped to aleviate a certain amount of buyers regret concerning an order for new lenses i just put in yesterday. i would be curious to try out the izon system in the future (i don't think they're in Canada yet), but for the time being i'll be happy with my standard prescription.

[Graduate]

Try the new generation of phoropters like TOPCON CV-3000 Compu Vision phoropter which combines a new design with modern technologies. It furthers ensures the operator improved efficiency and optimum performance utilising the very latest in refraction techniques.
In addition to the existing functions as 1 dial controller, color coded cross cylinder and illuminated PD setting, the CV-3000 has incorporates new functions such as a motorized mechanical convergence system enabling the 21 step routine and a wider visual field which may leads to examinations with less accommodation.

The CV-3000 Compu Vision is unique in offering a variety of controls and combinations with Topcon Chart projectors ACP and Mirror Chart system MC.
The ergonomic switch lay out and software design ensures fast and smooth operation and lens rotation.
Program and connection facilities are the finishing touch for this new CV-3000 Compu Vision.

The CV-3000 can easily be connected to refractions units.It is cream in refraction.My office has installed one recently and I fall in love immediately with it.

[Framebender]

you can go to www.theoptom.com . In the members list you'll find Gogs. Gordon is a bigwig in that company.

[noughtme]

Try the new generation of phoropters like TOPCON CV-3000 Compu Vision phoropter which combines a new design with modern technologies.

while dispensers always seem to be pushing for the latest and greatest in lens technology, what's the best way for consumers to know their optometrists are using up to date technology? is it unheard of to contact distributors of medical diagnostic equipment to track down which practices are using a particular device or system?

[Dave Nelson]

Don't make the common mistake of assuming technology is a substitute for skill and training. A really skilled refractionist on a clunky phoropter can produce really finely tuned prescriptions. Of course, health professionals should also be willing to accept new technologies, but for heavens sakes don't think technology alone will ever replace skill and clinical judgement.

[noughtme]

i would never make that mistake, which is why i made the distinction between "latest and greatest" and up-to-date. going back to my original question, i was wondering if most practitioners feel that the standard phoropter is more than adequate or if they would move to basing prescriptions primarily on wavefront analysis, and if this would provide any benefit?

[Barry Santini]

we are emabraking on a period where we will leave traditional refraction /phoropter use behind. When the wavefront-translation algorithms are more refined with clinical experience, and auto refractor utilizing this new technologies will produce a more *satisfactory* correction for many people than is done today.


I, for one, can't wait!