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1963 censuses of business, manufactures, and mineral industries : Virgin Islands of the United States

Numero de empleados renumerados durante LA SEMANA comprendida entre el
5 y el 1 1 de enero de 1964 c. Remuneraciones pagadas durante la semana com
- prendida entre el 5 y el 1 1 de enero de 1964 d. Propietarios y socios que ...

Creativity and Interactivity

New Ways to Experience, Market and Manage Museums : the 2003 Kenneth Myer Lecture for the George Fairfax Fellowship

Magnitude of Visual Improvement Expected with Supernormal Optics

Purpose: FDA clinical trials are currently testing wavefront guided laser corrections that, when perfected, could provide patients with extraordinary vision called "supernormal vision". Our purpose was to estimate how much visual performance, tested by contrast sensitivity, could be improved in ten subjects with simulated supernormal visual correction. Methods: High contrast gratings were projected onto the retina of one eye for each subject using a Lotmar white-light interferometer. This equipment enabled us to theoretically bypass the optics of the eye to gain estimates of neural limit contrast sensitivity. Another light with variable luminance was superimposed on the grating pattern to alter its contrast on the retina. The contrast threshold was measured at five spatial frequencies (maximum, 24, 12, 6, and 3 cycles/degree), to estimate contrast sensitivity with simulated supernormal vision. These measurements were compared to normally measured contrast sensitivity values to estimate the visual benefit of a perfect optical correction. Results: On average, simulated supernormal correction improved visual acuity to 20/12 : contrast sensitivity improved by factors of 6±2 and 2±1 at 24 and 12 cycles/degree, respectively. Paradoxically, contrast sensitivity at 6 and 3 cycles/degree declined by factors of 0.8±0.4 and 0.3±0.2, respectively. A wide range in benefit ratio measurements was observed at 24 cycles/degree from a factor of 11 to a factor of 1.5. Conclusion: Although supernormal visual correction can improve visual acuity to 20/12+, the most significant improvement may be better contrast sensitivity for medium and small sized objects. The variability in contrast sensitivity improvement show that supernormal visual correction would benefit each patient differently. The decline in visual performance for the lowest spatial frequencies, corresponding to large objects, may be an artifact of our methods for normal contrast sensitivity measurement.

Purpose: FDA clinical trials are currently testing wavefront guided laser corrections that, when perfected, could provide patients with extraordinary vision called "supernormal vision".