Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2000-04-27
2001-09-25
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
Reexamination Certificate
active
06293675
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to portable visual examination apparatus and, in particular, to a hand-held instrument for bleaching the macula of the human retina and measuring its recovery time.
2. Description of the Prior Art
The retina of the human eye consists of several layers, including a layer of nerve cells and fibers and a deeper layer of rods and cones. Cones differ from rods in that the cones provide a human with color and detailed vision, whereas rods differentiate black/white and motion. This layer of rods and cones is the light-sensitive layer. Located in a small central area of the retina is the macula, which houses the higher concentration of cones. Further, within the macula, the highest concentration of cones resides in the fovea.
Macular photostress testing is a sensitive method for detecting patients with macular disturbances, such as cystoid macula edema, central serous choroidopathy and senile macular degeneration. These disturbances have been shown to cause a significantly prolonged recovery from photostress.
It is well known in the art that exposing the macula of the human retina during an ophthalmoscopic examination to a bright light requires a certain amount of time for the human eye to recover useable visual acuity. This return time is commonly referred to as “recovery” time and varies from individual to individual. In many individuals, an unusually long recovery time is encountered after this photostressing or bleaching. This lengthened recovery time may be an indication of subliminal or developing maculopathy or other retinal disease. A recovery rate longer than normal helps the doctor identify persons at risk for developing macular degeneration or other retinal disease. In addition, a photostress test is particularly helpful in following intra-ocular surgery when cystoid macular edema is suspected. An increase in or lengthy recovery time indicates a maculopathy and helps to rule out other complicating factors, such as irregular astigmatism, early capsular opacification or optic nerve disease.
In assessing recovery time, there are various methods for definitively marking the point of re-focus (or recovery). A Snellen Eye Chart or an Amsler grid are two examples of tools used in marking the point of re-focus. A Snellen Eye Chart is a well-known chart consisting of lines of gradually reduced-sized letters. Typical Amsler grids, with focusing improvements, are disclosed in U.S. Pat. No. 5,646,710 to Caskey and U.S. Pat. No. 5,838,422 to Caskey. Further, U.S. Pat. No. 5,139,030 to Seay, Jr. discloses an Amsler grid with an illuminated center to assist the patient in focusing on the center of the grid. A Snellen Eye Chart may be utilized in determining the recovery time between bleaching of the retina to the return of visual acuity. While the Amsler grid may be used to assess recovery time, it is typically used as a screening device to ascertain loss or distortion of central or macular vision.
A flash unit, a timer and a focusing device have been previously combined together to create a visual examination apparatus for testing for macular degeneration. For example, U.S. Pat. No. 4,545,658 to Weiss discloses the use of such a combination for administering the photostress recovery test. However, the disadvantage of the Weiss apparatus is its requirement to be housed in a large, non-portable cabinet. While this cabinet-enclosed photostress instrument assists in normalizing the photostress procedure and simplifying the focusing process, the overall unit is large, cumbersome and is burdened with a split imaging mirror. In addition, such an instrument requires standalone optotype slides and continual administrative interaction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a portable, hand-held combined photostress testing apparatus that is easy and inexpensive in its manufacture. It is another object of the present invention to provide an apparatus that can be mass-distributed for use in both clinical and research situations. It is a further object of the present invention to provide an apparatus that is standardized to assist in advancing the art and determining retinal diseases.
The present invention is a hand-held, portable photostress visual examination device including a housing or body, which contains a controllable flash unit, a controllable timing unit, an optional back-lighting unit for an optotype chart, a controllable power source and electronic circuitry associated with these units. Connected to the housing may be an on/off switch, simultaneous flash and timer switch, a timer stop switch, a visual timing display for the timing unit and the recovery chart. Further, an Amsler or other grid may be provided on the body as an auxiliary tool. The recovery chart can be a Snellen Eye Chart or any suitable optotype chart for assessing an eye's return to a state of visual acuity. In addition, a color discrimination or contrast sensitivity test can be used. A measuring unit, such as retractable tape or string, may be attached to the top of the housing, allowing the examiner to quickly and accurately measure the appropriate distance between the device and the eye.
To use the invention, one of the patient's eyes is occluded and the patient reads, at a standard reading distance of 13-16 inches, the smallest definable line on the optotype chart on the face of the housing, using the patient's best optical reading correction. The measurement is recorded in near point Snellen or other standard ophthalmic terms. The patient's optical reading correction is removed, if such correction was required. The invention is moved to a closer, standardized distance from the non-occluded eye, using the measuring device, e.g., the retractable tape or string. The patient then gazes at the center of the flash unit, as viewed from the front side of the device. Next, the simultaneous flash and timer button is actuated, flashing the flash unit and starting the timing unit. Once “flashed”, the patient replaces any spectacle correction and attempts to read the line of optotypes immediately above the initially read line at the original reading distance. When the line of optotypes immediately above the initially read line is readable, the timer stop button is actuated, the timing unit ceases and the examiner reads the time from the visual timing display.
These and other advantages of the present invention will be clarified in the brief description of the preferred embodiments taken together with the attached figures wherein like reference numerals represent like elements throughout.
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Severin, Capt Sanford L. et al., “Photostress Test for the Evaluation of Macular Function,” Arch of Ophthalmology, Nov. 1963 70 (5), pp. 593-597.
Severin, Sanford L., M.D., “Macular Function and the Photostress Test 1,” Arch Ophthal, vol. 77, Jan. 1967, pp. 2-7.
Severin, Sanford L., M.D., “Macular Function and the Photostress Test 2,” Arch Ophthal, vol. 77, Feb. 1967, pp. 163-167.
Glaser, Joel S., M.D., “The Photostress Recovery Test in the Clinical Assessment of Visual Function,” Am J of Ophthalmology, Feb. 1977, 83 (2), pp. 255-260.
Gomez-Ulla, F. et al., “Macular dazzling test on normal subjects,” British Journal of Ophthalmology, Mar. 1986, 70(3)., pp. 209-213.
Zabriskie, Norman A., M.D., “The Pupil Photostress Test,” Ophthalmology, Jun. 1994; 101 (6), pp. 1122-1130.
Eger Elmer H.
Manuel George
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
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