Australian researchers have developed a test that uses holograms to diagnose the astigmatic error of the human eye. 'In this new test, patients view a hologram consisting of sunburst patterns; by reporting which sunburst lines appear clearest, the eye doctor can obtain information he or she can use in determining the correct prescription for the patient.' This approach still needs more testing, but apparently it's cheaper than other techniques and it could be used in remote areas and regions where standard facilities and number of optometrists are limited.
Here is how the system works. "The hologram contains the images of 16 integer numbers from -10 to + 5 placed at various distances from it. The hologram was recorded using a specially designed three dimensional object and an imaging lens." This is shown on the figure above, which describes the interference between the object wave (image forming wavefronts emerging from the lens) and the plane reference wave recorded on the holographic plate. (Credit: School of Optometry and Vision Science, University of New South Wales, Sydney, Australia)
This system has mainly been developed by Dr Kodikullam Avudainayagam and Dr Chitralekha Avudainayagam who both are researchers at the School of Optometry and Vision Science mentioned above.
This research work has been published by Optics Letters under the name "Holographic multivergence target for subjective measurement of the astigmatic error of the human eye" (Volume 32, Issue 13, pages 1926-1928, July 2007). Here is a link to the abstract and a quote from it. "We have now developed a holographic target consisting of sunburst patterns to measure the astigmatic error of the human eye as well. Apart from being simple, quick, and low cost, holography offers the advantage of being an open field refraction system that is devoid of the problem of proximal accommodation. We describe the holographic target, its working principles, the measurement procedure, and the initial results obtained."
The researchers went further and measured the performance of their installation. This new work will soon be published by the Journal of the Optical Society of America A -- probably under the name "Performance of the holographic multivergence target in the subjective measurement of spherical refractive error and amplitude of accommodation of the human eye." Here is a link to a preview version of this paper (PDF format, 29 pages, 1.16 MB). The above figure has been extracted from this working document.
Here is the last paragraph of the introduction. "Recently, we suggested the use of a holographic multivergence target to measure both the spherical refractive error and the amplitude of accommodation of the human eye. The holographic target offers a very simple means of measuring the spherical refractive error and the amplitude of accommodation. We now report the performance of such a target in measuring the spherical refractive error and the amplitude of accommodation of 20 young non-astigmatic subjects. The results are very encouraging.
Let's jump to the conclusions. "The method compares well with existing methods in the measurement of spherical refractive error. The measurement method is very simple. Further, the holograms are portable and inexpensive. [...] The holographic technique is an attractive alternative to existing methods for the measurement of amplitude of accommodation. The holographic method presented here can be extended to measure astigmatism as well. We are currently investigating the feasibility of such an extension.
The researchers also think their holographic method could be "particularly useful in remote areas and regions where standard facilities and number of optometrists are limited."
Sources: Optical Society of America news release, via EurekAlert!, July 5, 2007; and various websites
You'll find related stories by following the links below.
6:49:03 PM
Permalink
|
