Surgery – Truss – Pad
Patent
1992-11-02
1994-11-01
Manuel, George
Surgery
Truss
Pad
351221, A61B 313
Patent
active
053600100
DESCRIPTION:
BRIEF SUMMARY
GENERAL
The present application relates to a psychophysical method and apparatus for entoptically evaluating and mapping the human macula area vasculature with respect to the retinal point of fixation (RPF), as well as low-cost, simpler devices (i.e., no automatic hard copy provided) for self-visualization of the retinal vasculature or abnormalities thereof. Both mapping and simpler instruments incorporate similar principles and techniques as described herein to optimize the visual percept of the retinal vasculature and vascular abnormalities. In all embodiments of the Vascular Entoptoscope, light from a short wavelength source enters the eye through a small aperture, moving along a regular or irregular path at an optimized velocity. The essential difference between mapping and simpler instruments lies in the requirement to establish and monitor precise eye-instrument alignment and data display for accurate location of the RPF macular area retinal vascular defects.
MEDICAL APPLICATIONS
Knowing the precise location of the RPF is essential in modern ophthalmic surgery because the RPF can be inadvertently damaged during photocoagulation, resulting in marked vision loss. Unfortunately, the RPF is not visible on direct examination of the eye; its location must be determined subjectively and then related to observable landmarks. The present invention uses well-known techniques of entoptic visualization in a novel way to accomplish this goal.
A therapeutic trend in Ophthalmology is to photocoagulate (treat by burning) retinal abnormalities closer and closer to the retinal point of fixation (RPF). However, since treatment to the RPF can blind the eye, protocols advocate avoiding direct treatment to the RPF if at all possible. Since an examiner can not visualize the exact location of the RPF, protocols advocate using the center of the foveal avascular zone (FAZ) as a guiding landmark for RPF localization. That is, treatment should avoid the center of the FAZ on the assumption that the RPF is located at the center of the FAZ. Recent evidence using a mapping version of the Vascular Entoptoscope revealed that the RPF is not always centered within the FAZ (in fact not all eyes even have a FAZ). As a result, photocoagulation treatment in the foveal area may actually be causing blindness by burning the RPF unintentionally in about 20% of the cases where foveal area photocoagulation is the treatment of choice. This specific application of the Vascular Entoptoscope is discussed in detail in the section labelled "Alternative Methods and Prior Art" on page 10.
An important use for both precise mapping and simpler versions of the present invention will be in monitoring and treatment of diabetic retinopathy. Diabetes is the leading cause of blindness among working-age Americans, causing 8,000 new cases of blindness and 65,000 new cases of proliferative eye disease each year. In 50% to 84% of the cases, laser photocoagulation can prevent (or markedly reduce) adverse consequences of the proliferative stage of diabetic retinopathy. Receiving proper and timely treatment not only saves vision but reduces the socio-economic cost of diabetes-related visual impairment, currently estimated at $75 billion per year.
How is the Vascular Entoptoscope useful in the context of the diabetic? Current recommendations for medical care of diabetics include routine eye exams every 6 months to monitor the state of retinal vascular disease; however, many diabetics do not comply. If patients do not actually experience adverse effects (generally a visual acuity loss), many will assume nothing is wrong and conclude that a routine eye exam is a waste of time and money; this attitude can and often does lead to blindness. By the time a patient notices vision loss, significant damage has usually already occurred. Further, even for patients receiving regular care, the disease may progress undetected between appointments. Regular retinal examinations using the Vascular Entoptoscope, however, could alleviate these problems by allowing both convenient self
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Applegate Raymond A.
Bradley Arthur
Board of Regents , The University of Texas System
Manuel George
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