Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Objective type
Patent
1999-07-27
2000-08-08
Manuel, George
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Objective type
A61B 312
Patent
active
060991275
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an ophthalmoscope and more particularly to a scanning laser ophthalmoscope.
Various systemic diseases produce visible pathological features in the eye fundus. Thus, viewing of the eye fundus can provide an important indicator of these diseases.
A patient's fundus can be viewed by arranging for an image of the fundus to be directly projected onto an observer's retina. However, the small field of view, poor image quality and the need for correction of ametropia reduces the clinical value of the observation. In an alternative, a patient's fundus can be viewed by arranging for an illuminating beam to pass through the periphery of the pupil with the reflected light emerging through the centre of the pupil to provide an image of the fundus. However, it is necessary to dilate the pupil and use high levels of light which may be uncomfortable for patients.
To obtain a permanent record of the condition of the fundus and to assist in evaluation of the fundus, a so-called fundus camera is used to record the image of the fundus. The fundus camera can employ white light flash photography, but if monochromatic illumination is used instead, the contrast and optical quality is improved enabling better visualisation of certain fundus structures. Nevertheless, because objects of markedly different colours can be distinguished easily using colour information alone, colour photographs of the fundus are preferred with similarly coloured objects being differentiated on the basis of further details such as size, shape, etc.
Problems arise with the fundus camera for the reasons mentioned above. In particular, the high levels of light used reduces patient comfort. Thus, an ideal ophthalmoscope for observing the eye fundus would avoid the need to dilate the pupil and would minimise the intensity of light required to observe the eye fundus.
In the last 15 years, an ophthalmoscope for viewing the eye fundus known as a scanning laser ophthalmoscope (SLO) has been developed which comprises directing a narrow laser beam via a mirror system onto the eye fundus. The light reflected from the fundus is directed to a detector which produces an electrical output proportional to the intensity of the detected light. The electrical output can then be recorded or displayed on a visual display unit. By moving the mirror system according to a scanning sequence in a raster fashion and synchronising the detector to the scanning sequence, it is possible to produce an image of the fundus. Thus, it is not necessary to dilate the pupil. In addition, lower intensity illumination can be employed for viewing the eye fundus. However, care must be taken to ensure that the laser power is within the safety standards for retinal irradiation.
An object of the present invention is to provide an improved scanning laser ophthalmoscope.
According to the present invention there is provided an ophthalmoscope comprising: least three different wavelengths; incident thereon; means; of a patient's eye and for directing at least a portion of light reflected from said selected portion on to said detector means; and provide in sequence a single laser beam pulse of each wavelength and capable of operating said detector means to transfer said electrical signals to said store means at the completion of each laser beam pulse.
In this way, the detector means transfers to the store means the detection of the incident reflected light, from the selected portion of the patient's eye, which results from a single laser beam pulse, that is to say, the laser beam pulse of first one wavelength, then another wavelength and then another wavelength, in a sequence that is periodically repeated whilst the optical system directs the laser beams to scan that selected portion. As a result, an image of the selected portion is built up during a scan which comprises at least three different wavelength elements. By suitable manipulation of the stored electrical signals, the three wavelengths can be combined and if the correct wavelengths are selected, a colour image or
REFERENCES:
patent: 4213678 (1980-07-01), Pomerantzeff et al.
patent: 4781453 (1988-11-01), Kobayashi
patent: 5042939 (1991-08-01), Zayek
patent: 5214455 (1993-05-01), Penney et al.
patent: 5396302 (1995-03-01), Triller et al.
patent: 5943115 (1999-08-01), Ferguson
patent: 5997141 (1999-12-01), Heacock
Goldbaum, Michael H. et al., "The Discrimination of Similarly Colored Objects in Computer Images of the Ocular Fundus", Investigative Ophthalmology & Visual Science, vol. 31, No. 4, Apr. 1990, pp. 617-623.
Manivannan Ayyakkannyu
Sharp Peter Frederick
Aberdeen University
Manuel George
LandOfFree
Scanning laser ophthalmoscope does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Scanning laser ophthalmoscope, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Scanning laser ophthalmoscope will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1143570