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JUN. 7.2004 1:00PM LEROY SIGNS N0.2ee P.3i11 <br /> Normal Visual Acuity <br /> Another Ivey facxor to be considered in understanding how <br /> the eye perceives information is visual acuity, the sharpness or clarity of <br /> normal vision. Dr. Sheldon Weschler, of the School of Optometry at the <br /> University of Houston has studied the subject of visual acuity in reference <br /> to signs. He has been interested in establishing optimum standards for sign <br /> Size and sign visibility. Sign visibility is directly related to visual acuity <br /> and other principles of vision and suggests that minimal sign standards <br /> could be applied to signs, especially those intended to be read by the <br /> motoring public. Signs, after all, must be readlble by the largest number <br /> of viewers possible in order to be effective advertising. <br /> Table 8 presents ilie minimum size at which letters can be <br /> read at varying distances and by people with different measures of visual <br /> acuity- Weschler qualifies the numbers listed in this table in the following <br /> statements: <br /> "Snellen letters are most often used as the pat- <br /> terns for visual acuity measurement. The record- <br /> ing method is written as if the measure of visual <br /> acuity is a fraction (e.g., 20/20), although that is <br /> not the actual case. The upper figure is merely a <br /> notation of zhe distance from the _eye to the <br /> visual task (the letter). The lower figure repre- <br /> sents the size of the visual task. This minor point <br /> becomes important in understanding, for in- <br /> stance, that 20/40 visual acuity is not SO°io vision <br /> but merely a shorthand notation relating to the <br /> distance at which a measurement is made (20 <br /> feet) and the size of Snellen letter (.35 inches) <br /> that is just recognizable at that distance . . <br /> The standard visual acuity for a `normal' eye is <br /> considered to be 20/20. The standard frequently <br /> used as vision requirement for driVers is 20/40. <br /> But the 20/40 standard is a visual acuity level <br /> to be attained at the time of licensure, During <br /> the four-year period between. drivers license <br /> Visual acuity measurements the visual acuity of <br /> drivers frequently drops to lower levels. For that <br /> reason it may be wise to set signage standards <br /> that are based on visual acuities lower than <br /> 20/40" (Weschler, unpublished manuscript). <br /> 152 The Slgn User's Guider A Marheting Ald <br />