American journal of optometry and physiological optics最新文献

The 2 degree color mixture data of Stiles and Burch have been analyzed to study the differences between individual subjects and the lack of precision at the blue end of the spectrum. The luminous efficiency data have been compared to those of Judd's 1951 observer and the 1931 standard observer. The mixture data have been compared to those of Wright and Guild and have been related to mixture data of dichromats. One of the ten observers was found to have a luminous efficiency curve similar to that of a protanope and was excluded from the average data.

Visual acuity was estimated by making amplitude measurements of the transient visually evoked response (VER) wave to pattern reversal using check sizes of 5.5, 7.5, 8.5, and 9.5 min arc. As in previous studies the 5.5 min arc check produced a response which reflected the visual acuity of the high acuity subjects, but often failed to produce a VER wave at the low acuity end. The proposal is made that where the 5.5 min arc check produces an acceptable wave (amplitude greater than 1.5 microV) then the regression line for the 5.5 check can be used to predict visual acuity. Where the VER amplitude is below 1.5 microV for this small check size then a second recording must be made using the 9.5 min arc check and the visual acuity predicted from the 9.5 check regression line.

We studied the wearing of hard gas permeable contact lenses during decompression in a hyperbaric environment. Twenty-four exposures of three different lens materials were carried out in a hyperbaric chamber. The dry air dive profiles were: 45.72 m (150 ft) for 30 min and 15 min; 22.86 m (75 ft) for 15 min; and 11.43 m (37.5 ft) for 15 min. Bubbles occurred under all lens types; they were seen at simulated depths as shallow as 1.98 m (6.5 ft) after the least stressful exposure. Due to the tissue offgassing half-time of the eye, it is unlikely that the bubbles are a result of nitrogen from the eye. They probably arise from the tear layer.

Local stereoacuity was reduced when red-green anaglyph glasses were worn. Glasses were from the TNO stereotest. Without these glasses, all 15 subjects had good or almost good local stereoacuity. With the glasses, all stereoacuities were reduced but one subject still had a good stereoacuity of 8 sec arc. Reductions with the TNO anaglyph glasses ranged from 2 to 34 sec arc. The TNO test was also performed to see if there was a difference between local and global stereoacuity while wearing the glasses. Results were similar for 6 subjects, all of whom had the best TNO stereoacuity of 15 sec arc. Global (TNO) stereoacuity was worse than local stereoacuity for the other subjects with the most extreme difference being 464 sec arc. If aniseikonia was induced by the red-green glasses, this could not have contributed to a reduction in either local or global stereoacuity.

Contrast sensitivity was measured at near using the Vistech 6000 Contrast Test System (VCTS) in 287 persons aged 4 to 87 years. Obtained data compared well with those previously reported for the Vistech charts. Results indicate an age-related loss in sensitivity to intermediate and higher spatial frequencies. This is consistent with the age trends observed using other methods for measuring contrast sensitivity functions (CSFs). However, the Vistech charts yield contrast sensitivity values which are lower than those obtained previously with the Nicolet system. These between-method differences are greatest at lower spatial frequencies, and are attributed to the small number of grating cycles in the Vistech charts. The data are used to develop provisional age norms for the Vistech charts which allow the assessment of an individual's performance relative to their age cohort. Recommendations for use and future development of the Vistech charts are also given.