The Keystone View VS-V Standard Vision Screener, Model #1155, is a compact and self-contained instrument designed for standardized and confidential vision screening. It incorporates over 80 years of vision testing research and expertise, utilizing reflected light rather than backlit targets to simulate everyday visual function. The device measures 10 inches wide, 15.5 inches long, and 7 inches tall, weighing less than 11 pounds, making it suitable for desktop use. It operates from a standard or 220-volt AC power outlet, converting power to 12 volts DC to ensure safety. The recommended operating temperature is 32 to 104°F, with a storage temperature range of -4 to 158°F.
Function Description:
The VS-V performs 18 tests that screen 10 vision functions in approximately 3-5 minutes. The subject sits or stands with their head in the headrest, viewing target slides and lamps. The examiner controls the procedure via a hand control or Keystone View Software, explaining targets and recording responses. All tests, including monocular acuity, are performed with both eyes open to replicate natural visual function and detect issues like suppression.
Key Vision Functions Tested:
- Binocular Testing: All tests are given with both eyes open to mimic natural vision.
- Suppression: Detects if a subject blocks vision in one eye, which standard wall charts cannot diagnose.
- Far-point Acuity: Replicates a 20-foot distance using a unique bifocal lens system.
- Near-point Acuity: Replicates a 16-inch "reading distance."
- Intermediate-point Acuity: Includes two tests at 26 inches and 39 inches, using a supplemental lens system for assessing vision fatigue in computer users and for those operating machinery.
- Phoria: Uses stereoscopic targets and prism diopters to gauge eye balance, comfort, and efficiency.
- Stereopsis: Measures depth perception with a 3-D target.
- Fusion: Tests the ability to merge two images into one clear, coherent image.
- Color Perception: Screens for severe (red/green) and mild (blue/violet) color deficiencies.
- Horizontal Peripheral Visual Field: Identifies "tunnel vision" by measuring the extent of peripheral vision using miniature LED target lamps.
- Low Light/Night Vision: Can simulate low lighting conditions for night driving vision assessment.
Usage Features:
The VS-V features an automated lens system that allows easy switching between far, near, and intermediate distances using push-button controls. The unit pivots through a 63-degree arc to adjust to the subject's eye level. A magnetic catch holds the unit closed when not in use. The headrest accommodates various eyeglass frames, with a specially-designed strip for comfortable forehead rest.
The Elliptech Soft-Touch hand control unit facilitates easy operation, suitable for hand-held or desktop use. It allows advancing/reversing stereo tests, selecting distances, occluding either eye, selectively lighting peripheral vision test lamps, and performing night-vision tests. The hand control cannot be used simultaneously with the Keystone View Visionary Software.
Test Administration Guidelines:
- Posture: Maintain erect back and head, with the forehead resting lightly against the headrest. Avoid tilting the head or pulling away from the instrument.
- Corrective Lenses: Tests should be conducted with lenses worn as usual. Lenses for specific distances (reading or far) should be removed when testing other distances. Caution is advised when testing individuals recently fitted with new glasses, with a retest recommended after two months if scores are poor.
- Procedure: Follow an organized procedure with standardized questions. Responses should be prompt (5-10 seconds). Acknowledge responses without indicating approval or disapproval.
- Recording: Responses are recorded on an included record form or via software. Shaded columns on the form indicate potential unsatisfactory performance.
- Environment: Conduct tests in a reasonably quiet room with subdued lighting to avoid glare and distractions. Test subjects individually to prevent sharing information.
- Medico-legal Records: Special tests may be required for medico-legal purposes, such as distance acuity without corrective lenses or eye occlusion.
Interpretation of Test Scores:
Results should be considered holistically to indicate visual efficiency. Subjects scoring in the "unacceptable" area or with peripheral vision less than 70 degrees should be referred for a full eye examination. Scores in the lightly shaded area indicate "doubtful performance" and warrant referral for occupations requiring good vision. Failure in stereopsis or color vision tests does not always require referral but subjects should be made aware of deficiencies. Phoria readings are important indicators of headaches and fatigue. Periodic retesting (annually) is recommended due to vision changes over time.
Maintenance Features:
The VS-V requires minimal maintenance, with operating components protected and solid-state circuitry ensuring high reliability.
- Cleaning: Disconnect from power supply before cleaning. Dust the housing and control unit with a soft cloth or brush. Lenses can be cleaned with a soap-and-water dampened cloth and dried with a soft cloth or tissue. For heavy soiling, a mild soap-and-water or general-purpose cleaner can be used.
- Lamp Replacement: The two Nichia NSPW515BS Daylight LED lamps for stereo targets are long-life rated but may eventually need replacement. Contact a local distributor for replacement LEDs and follow instructions carefully. Peripheral vision test targets and signal lights on the control panel are LEDs designed for extremely long life and should not require replacement.
- Troubleshooting (No Power): If the instrument does not turn on due to a blown fuse on the mother card, a connector inside the machine needs to be moved to a backup fuse. This involves removing the top cover, locating the black and white cable from the on-off switch to a white connector with 3 terminals, and then moving the specified connector one position to the right on the red mother card.
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