Effects of flurbiprofen and indomethacin on acute cystoid macular edema after cataract surgery: functional vision and contrast sensitivity.

We examined the effect of acute cystoid macular edema (CME) on contrast sensitivity. Eyedrops were instilled into the surgically treated eye f1p4 times daily for two days preoperatively and for three months postoperatively. Angiographic and clinical CME were measured, as were contrast sensitivity and Snellen acuity. Jaeger visual acuity equivalents were calculated and digital imaging techniques used to simulate visual function. We found that angiographic CME reduces functional vision as measured by contrast sensitivity and visual acuity over a large range of sizes. In patients treated with the flurbiprofen vehicle, those without CME had higher mean contrast sensitivity scores than those with CME; this increased over time. Those treated with flurbiprofen and indomethacin had slightly higher contrast sensitivity scores than vehicle-treated patients; this also increased over time, most notably in the higher spatial frequencies. Flurbiprofen treatment improved contrast sensitivity in patients with and without CME significantly at 12 cycles per degree. Flurbiprofen-treated patients with CME in general had higher contrast sensitivity scores than vehicle-treated patients. In this population of patients having cataract surgery, treatment with flurbiprofen or indomethacin reduced the loss of functional vision associated with CME.

Contrast sensitivity under photopic conditions in the Prospective Evaluation of Radial Keratotomy (PERK) Study.

We studied the effect of radial keratotomy on contrast sensitivity in 69 individuals with one eye operated and one eye unoperated in the Prospective Evaluation of Radial Keratotomy (PERK) Study, with a mean follow-up time of 13.8 months (range 6 months to 31 months). We tested contrast sensitivity under normal daylight conditions using both photographic plates and a computer-video apparatus. On average, we found no clinically meaningful loss of contrast sensitivity in eyes after radial keratotomy. However, eyes with radial keratotomy showed a statistically significant decrease in contrast sensitivity at the higher spatial frequencies of 12 and 18 cycles per degree, although all values were within the previously established normal range. Specifically, 44% of the patients had approximately the same contrast sensitivity in both eyes; 40% of the patients had 50% less contrast sensitivity in the operated eye than in the unoperated eye; 16% of the patients had 50% more contrast sensitivity in the operated eye than in the unoperated eye. Contrast sensitivity improved gradually in operated eyes between 6 months and 2 years after surgery. Eyes with radial keratotomy, in which the diameter of the pupil was the same size as or larger than the central clear zone, had slightly decreased contrast sensitivity compared to eyes in which the pupil was smaller than the clear zone.

Photoaversion in retinitis pigmentosa.

Photoaversion, or light-induced interference with visual comfort and performance, has been a recognised but poorly documented symptom in retinitis pigmentosa (RP). We found that a majority of our RP patients complained of photoaversion even in the absence of significant cataract. RP patients had reduced contrast sensitivity relative to normal people, but the decrement in their visual performance as a result of glare or photostress was only slight. RP patients had raised short-term adaptation and increment threshold levels, but their rate of short-term or photopic adaptation was normal. Photoaversion in RP may result because a small interference with contrast sensitivity or adaptation can place patients in a range of functional disability, or it may derive from a combination of minor aberrations.

A new contrast sensitivity vision test chart.

A new contrast sensitivity vision chart has been tested and compared to an automated video-based vision tester on 83 observers whose ages ranged from 9 to 75 years. Good agreement was found between the contrast sensitivity measurements obtained from the vision chart and the automated tester for similar population and age variations. These results suggest that vision test charts can be developed to provide useful contrast sensitivity psychometric functions and yet be as simple to use as present eye charts.

Large-sample norms for contrast sensitivity.

A portable microprocessor-controlled instrument automatically measured the static and dynamic contrast sensitivity functions (CSF's) of 265 observers for a normal population at the Dayton Air Fair and Air Force Museum. Repeat measures for six observers taken 6 months later show small, nonsystematic differences from original measurements. Median values of contrast sensitivity as well as regions encompassing 75 of 90% of our sample are shown.

Comparison of three methods for rapid determination of threshold contrast sensitivity.

Threshold contrast sensitivity functions for 13 subjects were determined on 5 consecutive days using three psychophysical methods. Each method was implemented on a microprocessor controlled display system and considered as a possible candidate for a rapid visual screening test. The methods used were Bekesy tracking, method of adjustment, and method of increasing contrast. The method of increasing contrast proved superior to the other methods in repeatability, speed, and the preservation of individual differences in contrast sensitivity over the testing period.

Low spatial frequencies dominate apparent motion.

Experiments are reported which have been designed to establish what features of a pair of figures can be used as an input for apparent motion. The display consisted of a central figure, A, which appeared briefly and was followed immediately afterwards by two figures, B and C, which appeared on either side of the original location of A. Figure A can thus move towards either B or C. When A was a low-pass filtered square it moved towards C (a low-pass filtered square that was similar to A but 'rotated' by 45 degrees) rather than toward B (a high-pass filtered square identical to A in orientation and size). When A was an unfiltered square it moved towards C (a low-pass filtered square of identical orientation) rather than towards B (a high-pass filtered square of identical orientation). Lastly, when A was a 'solid' square it moved towards C (a solid circle) rather than towards B (an outline square). All three experiments suggest that the direction of perceived movement is determined exclusively by low spatial frequencies rather than by similarity of oriented edges, especially when speed of alternation is rapid.

Contrast sensitivity predicts pilots' performance in aircraft simulators.

Contrast sensitivity was found to be better than visual acuity for predicting a pilot's ability to detect a small, semi-isolated, air-to-ground target. Eleven instructor pilots had their acuity measured by both conventional and contrast sensitivity methods. Scotopic contract sensitivity showed the highest correlation with slant detection range (0.83). Conventionally determined visual acuity proved to be a poor predictor of a pilot's ability to detect a small low contrast target.

Suprathreshold processing of complex visual stimuli: evidence for linearity in contrast perception.

Magnitude estimation experiments show that perceived contrast for both sine and square waves is a linear function of stimulus contrast. The suprathreshold sine:square ratio required for equal perceived contrast derived from these data was verified by contrast matching experiments. These findings imply a high degree of linearity in suprathreshold visual processing of contrast.