Optics: eye examining – vision testing and correcting – Eye examining or testing instrument – Subjective type
Reexamination Certificate
2001-10-09
2003-11-25
Manuel, George (Department: 3737)
Optics: eye examining, vision testing and correcting
Eye examining or testing instrument
Subjective type
Reexamination Certificate
active
06652101
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to visual screening systems and methods, and more particularly, to a method and apparatus screening monocular visual acuity to detect vision disorders, such as amblyopia.
BACKGROUND INFORMATION
It is recommended to screen children at an early age for vision disorders. The American Academy of Pediatrics, along with other medical professional organizations, recommend that children have their visual acuity quantified at least by age four. In many instances, it may be possible to correct a child's vision if problems are detected during early childhood.
Amblyopia is the leading cause of reversible blindness in children in the United States, affecting approximately 2-4% of the population. In order to successfully treat amblyopia, a child must be diagnosed with this condition at an early age. If the condition is detected sufficiently early, it is often possible to completely, or at least substantially, correct the child's vision. However, if left untreated by seven to nine years of age, it may only be possible to slightly improve a child's vision, if at all.
Amblyopia, also known as “lazy eye,” is a condition in which a patient's brain processes substantially more visual information from one eye than the other, such that the patient is only “seeing” with one eye. This typically develops during early childhood, when a child compensates for reduced vision in one eye by neurodevelopmentally learning to see only through the other eye. Amblyopia may result from a misalignment of a child's eyes, known as “crossed eyes.” Amblyopia can also be caused by a marked difference in visual acuity between a child's eyes, causing the child to focus through only one eye. This is called anisometropic amblyopia. For more information about amblyopia, see http://www.preventblindness.org/children/amblyopiaFAQ.html.
If detected at an early age, the debilitating effects of amblyopia may be avoided in many circumstances by training a child's visually immature brain to process images from the affected eye. The amblyopic eye is commonly treated by using a patch to cover a patient's “stronger” eye, which forces the patient to use the weaker eye. Another alternative method to “patching” is to use eye drops to “blur” the vision in a child's stronger eye. For a patient with anisometropic amblyopia, who is unable to see normally through one or both eyes due to an uncorrected refractive error, proper spectacle correction (glasses) is also prescribed to be worn full time, simultaneously with the “patching” or “blurring” treatment, to focus the blurred image on the retina of the affected eye (at the back of the eye). The use of the patch, or eye drops, is gradually tapered off, usually over the course of several months or even years, depending upon the severity of the problem.
Unfortunately, it can be difficult to diagnose vision disorders such as amblyopia in children of early age. A child may not realize, or otherwise not be able to communicate, that the child's eyesight is outside of a normal range. A child with normal vision in one eye may not notice a vision problem, even if the child's other eye is severely visually impaired. Parents are also often unable to detect that a child is suffering from a vision disorder. For example, although a child with anisometropic amblyopia may be legally blind in the affected eye, the condition often may be overlooked because the child's eyes are properly aligned, and so the child may not appear to be having vision difficulties.
There are several methods and systems that presently exist for examining a child's vision. Assessing monocular visual acuity (checking visual acuity in one eye at a time) is the best indicator of amblyopia. Monocular visual acuity assessment is the best indication of any eye pathology in children of pre-school age.
The most common method of screening vision in children of pre-school age is through the use of an eye chart. This is typically performed by positioning a wall chart across a room, at least ten feet from a child to be examined. An examiner points to optotypes (letters or symbols) that are displayed on the chart while the child covers one eye with her hand or some other type of cover. To reliably test the child's vision in one eye at a time, an adhesive patch may be used to ensure the child does not try to compensate for poor vision in one eye by “cheating” with the other eye. If the test indicates that the child can see much more clearly from one eye than the other eye, then the child may be suffering from amblyopia.
Although a vision chart can be an effective tool for measuring visual acuity, there are several disadvantages to its use for screening pre-school aged children for vision disorders. First, wall charts are not easily portable and require a special room or hallway to use. Secondly, a second examiner is usually required when using a vision chart if the child is too young to read letters or describe the appearance of the “optotype” symbols, or if the child otherwise cannot verbalize the correct response due to shyness or lack of understanding of the test. As one examiner stands at the chart and points to certain optotypes (symbols) on the chart, the second examiner holds a second chart at a closer proximity to the child. The second chart contains the same optotypes, but in a different arrangement. With one eye covered at a time, the child points to the optotypes on the second chart that correspond with the optotypes that the first examiner points to on the first chart. The second examiner is needed to monitor the child's responses while simultaneously monitoring the child to detect squinting or if the child is otherwise “cheating” on the vision exam.
A photoscreener can also be used for detecting vision disorders in very young children. A portable camera (such as the MTI PhotoScreener, by Medical Technology and Innovations, Inc., of Lancaster, Pa.) takes a photograph of a child's eyes. In the photographs, strabismus (misalignment of the eyes) and conditions that lead to amblyopia such as astigmatism, cataracts and refractive errors show up as crescents on the child's pupils. A photoscreening test is quick, noninvasive and painless, and may be useful as a high-volume initial screening method in schools. However, most photoscreeners that are presently available provide many false results (both false negatives and positives), and are not reliable for predicting visual acuity. Photoscreeners also require subsequent film processing, and may be too expensive to be used by primary care physicians or parents.
An electronic vision screener is another device that is available for performing children's vision screening. To use a vision screener (such as the Titmus Vision Screener), a child peers into a portable box and is asked to identify optotypes that are displayed on a screen in the box. Using a separate controller, an examiner can control the display of the optotypes on the screen. A vision screener can be used to test for acuity (near and far), depth perception, color perception, muscle balance (lateral and vertical phoria), and horizontal visual fields (peripheral vision of 130 degrees in each eye).
While these electronic vision screeners can be useful for screening adults' vision (and are commonly used as part of a driver's exam by local departments of motor vehicles), there are several disadvantages to using the device for screening children's vision for disorders, such as amblyopia. To use a vision screener, the child is required to recognize and identify the optotypes displayed on the screen by speaking aloud, which may not be possible for young children (as opposed to matching optotypes from an image to an optotype card). The mirrors and lighting in the device may confuse a young child, and generate less accurate results. In addition, although the device is designed to be able to separately measure the visual acuity in each eye, a young child with poor vision in one eye may shift
Manuel George
Shaw Pittman LLP
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