As Anthony clearly pointed out, the standard way of prescribing spectacles or other forms of visual corrections is an instrument called phoropter (and I agree it is quite old fashioned!). This is an instrument from the XIX century that uses wheels with lenses placed in front of the eye. Subjects looked through these lenses that are changed by the doctor until they can read letters projected at a screen. And this is the standard today well into the XXI century.
While other technologies have evolved quite rapidly in the last decades (you can just think in telephone technologies), phoropters are basically as they were more than one hundred years ago.
phones and phoropters: quite a different evolution! but ready to change...
However, today there are available new technologies that can change the way vision is assessed. In particular the most promising is adaptive optics. I have already covered here in some posts how ADAPTIVE OPTICS works: http://pabloartal.blogspot.com/2009/02/adaptive-optics-technology-for.html
Using adaptive 
optics, we are able to produce any optical conditions in the eye of a subject. In our laboratory and in others, we developed instruments to manipulate the optics of one eye. However, vision is binocular!
optics, we are able to produce any optical conditions in the eye of a subject. In our laboratory and in others, we developed instruments to manipulate the optics of one eye. However, vision is binocular! The best approach to assess vision would be going binocular!
We have recently developed a binocular adaptive optics simulator that is just published in the September issue of the journal Optics Letters: OPTICS LETTERS, Vol. 34, No. 17, page 2628, September 1, 2009. Joshua Fernandez and Pedro Prieto are the co-authors of this paper.
The apparatus is capable of measuring and manipulating the aberrations from the two eyes simultaneously for the first time. An additional relay is incorporated for the binocular presentation of stimuli and visual tests through the modified optics. Independent manipulation of the aberrations from each eye is possible with the system, while binocular viewing is still performed. An important feature of the prototype consists in the fact that the measurement and manipulation of the wavefront is accomplished by means of a single wavefront sensor and a single correcting device, respectively. (See picture of a diagram of the system below) The wavefront corrector is a Liquid Crystal on Silicon (LCOS) spatial light modulator (LCOS-SLM X10468-04, Hamamatsu Photonics). This device modulates the incident light by locally varying the refractive index of the liquid crystal.
A possible alternative solution for a binocular system could simply consist on the duplication of the already existing monocular visual simulators, one for each eye. However, our approach is cost effective and relatively simple to operate from a single system without duplicating parts.
In addition of an advance phoropter, this instrument and technique may be of help to better understand the influence and impact of aberrations in binocular vision. The binocular visual simulator also presents a high potential as a tool for the design of advanced or customized ophthalmic elements, and in particular for the systematic search of phase profiles extending depth of focus for correction of presbyopia. ( By the way... some readers ask me often about viable solutions to correct for presbyopia … so I will cover that topic in a future post… I promise!).
Warm summer still here, Omi & Catalina. We are already in the last days of August, but still quite warm here in Murcia. We need to wait for a few more weeks to see some relief in the temperatures. I cannot complain much, since I scaped for some days when I was recently travelling in the US with my family. I visited San Francisco (Stanford), Pasadena and Miami (although here I did not avoid the hot weather!). I will tell you more on this interesting trip perhaps in a future post.
Some readers asked on how my new little dog was doing. Omi (the dog's name) is growing fast but still quite nervous. You can see here a recent picture with Catalina (my cat) just safely observing the dog in the tree (superior part of the picture).
Fernández, E., Prieto, P., & Artal, P. (2009). Binocular adaptive optics visual simulator Optics Letters, 34 (17) DOI: 10.1364/OL.34.002628
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8 comentarios:
AS AN EYE DOCTOR, I WILL BE HAPPY IF PHOROPTERS ARE ACTUALLY REPLACED SOON. BUT CONSIDER THE PRICE OF THE NEW TECHNOLOGY AND WHAT THEY WOULD ADD TO THE PRACTICE. WHY ANYBODY SHOULD CHANGE AN OLD, BUT WORKING, PHOROPTER FOR A NEW AND SOPHISTICATED PIECE OF EQUIPMENT IF SIMPLY THE SAME IS PROVIDED?
THANKS FOR THE INTERESTING POSTS. ANGELO.
Hello Angelo.
You are making here a great point. What new adaptive optics (AO) system will add compared to the current instruments.
To name only a few advantages:
1) With AO you could modify not only defocus and astigmatism (sphere & cylinder), but all the other aberrations. For instance you could customize for spherical aberration in each patient.
2) Size. You would not require a long distance in your room to place the screen. Everything will be in a small box.
3) Versatile. You could do any combination of optics in the two eyes simulating real life visual conditions.
4) You could test for letters or real scenes, stereopsis... whatever you could imagine.
5) You could simulate any optical conditions. For instance you could show a prospective patient the approximate outputs for different situations, far, intermediate, near and different illuminations...
As a non scientist person, but interested in science I like reading your blog. This effort is specially nice. I wish you all the luck to product a new instrument good for patients all over the world. ANA
Sorry to tell you that in my opinion traditional phoropters, relatively inexpensive and simple, will be here for a long, long time despite the new advances in the optoelectronic technology. Amando, Perth
Perhaps Amando is right, but I really appreciate your efforts to advance the field for the future benefit of patients. Thanks. Lora. UT
this is of course important, but better prescriptions will not be only based in better technology, but in good doctors and practicioners.
Quite nice. Congratulations from New York city.
Great post you got here. It would be great to read more concerning that theme. Thanx for posting that data.
Joan Stepsen
Tech gadgets
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