effect of yellow-tinted lenses on brightness

Vol. 7, No. 10/October 1990/J. Opt. Soc. Am. A 1905

Effect of yellow-tinted lenses on brightness

Susan A. Kelly

Illinois College of Optometry, 3241 South Michigan Avenue, Chicago, Illinois 60616

Received November 7, 1986; revised manuscript received July 10, 1989, accepted March 26, 1990

Magnitude estimates of brightness were obtained for small (5-deg diameter) and large (15 deg X 20 deg) targetsviewed through yellow-tinted lenses (ytl's) and luminance-matched neutral lenses. The results indicate thatbrightness perception with ytl's is up to 40% greater than that with neutral lenses when the spatial extent of thestimulus exceeds the fovea. The onset of the enhancement effect is coincident with the chromatic threshold, and itsend point is coincident with psychophysical estimates of rod saturation. In a second experiment, brightnessestimates were obtained for the ytl's and neutral lenses during the cone plateau of the dark adaptation curve whenrods, but not cones, were desensitized by bleach. The brightness-enhancement effect was negligible. These resultsconfirm the subjective impression that brightness perception is enhanced by ytl's and indicate that this effect ismediated, in large part, by the contribution of rod signals to the chromatic pathway.

INTRODUCTION

The visual consequences of yellow-tinted lenses (ytl's) havelong been debated. A consensus has yet to be reached as toeither the visual effects of these lenses or their underlyingmechanism(s). Ytl's have been reported to improve visibili-ty in dim light and dull weather",2 and thus to be useful tohunters, sharpshooters, skiers, and aviators. More recently,ytl's have been included in the repertoire of low-vision aids,3

and sports-vision enthusiasts have been recommending yel-low and amber tints to enhance athletic performance.

The bulk of the available evidence, however, fails to sup-port the widespread popularity of ytl's; they have not beenfound to enhance night driving",2 nor to improve visual acu-ity,1 4 stereopsis, 5 or contrast sensitivity. 6 Yet it is consis-tently reported that ytl's produce an increase in brightnessdespite the actual decrease in the percent of light transmit-ted through them.12,7-' 0 This phenomenon was noted byWright, who attributed it to the tendency to associate yellowwith sunlight and its concomitant high level of illumina-tion." Despite these claims, however, no studies have as yetinvestigated their validity.

A number of optical explanations have been offered toaccount for the enhancement of visual function ascribed toytl's. For example, it has been suggested that the selectiveremoval of short wavelengths from the visible spectrum mayreduce Rayleigh scattering in conditions of fog.12 The prac-tical use of these filters by sports enthusiasts under low-visibility conditions suggests this is the case. Also, it hasbeen shown that broadband yellow filters enhance contrastfor medium- and long-wavelength targets viewed against ashort-wavelength background.7

A third possibility is that ytl's may reduce lenticular fluo-rescence.12 Experiments have shown that the fluorescenceis due to chromophore-containing proteins with activationwavelengths of approximately 340-360 and 420-435 nm.13Lenticular fluorescence increases linearly with age. Howev-er, the significance of this effect is not limited to the elderly,since it is manifest after the first year of life.' 4 The negligi-ble transmission of the activation wavelengths by ytl's (seeFig. 1) may thus increase the contrast of the retinal image.

It has also been suggested that ytl's can reduce or elimi-nate chromatic aberration. However, it has been shownexperimentally that visual acuity is independent of wave-length (except for short-wavelength light)4 and not im-proved by the use of either monochromatic targets or anachromatic lens.15 However, Campbell and Gubisch report-ed that contrast thresholds at intermediate spatial frequen-cies improved up to 65% for monochromatic yellow lightcompared with white light.15 These results supported pre-dictions from optical theory that the adverse effects of chro-matic aberration in a diffraction-limited optical system,such as the eye, would occur not at the resolution limit of thesystem but rather at half-maximum frequency transmitted.Interestingly, however, the ytl's that are most widely em-ployed are not narrow-band but, rather, broadband filters.Contrast sensitivity is not enhanced at intermediate spatialfrequencies or, indeed, at any spatial frequency with thesefilters,6 suggesting that the optical properties of broadbandytl's do not have visual consequences.

Recent evidence suggests that other, nonoptical factorsmay be involved. Kinney and co-workers8 have hypothe-sized that tasks mediated by the chromatic pathway may beenhanced by ytl's because the elimination of short wave-lengths could actually increase the output of the opponentchannels. Results from Kinney's laboratory show that thereaction time to low-contrast, low-spatial-frequency targetsis enhanced with ytl's, as is the perception of depth contours.These data are the first experimental evidence that indicateytl's affect visual performance. The purpose of the presentpaper is to report the effects of ytl's on magnitude estimatesof brightness.

The first experiment contrasted the effect of ytl's andluminance-matched neutral lenses on brightness as a func-tion of target size. The impetus for this parametric manipu-lation arose from a consideration of the practical use of theselenses. The entire visual field is affected by the applicationof yellow goggles or tinted lenses. Laboratory experimentsthat employ small targets that only stimulate the foveal areado not simulate the actual visual experience with theselenses. In addition, the positive reaction time results ofKinney et al. were dependent on spatial frequency and the

0740-3232/90/101905-07$02.00 © 1990 Optical Society of America

Susan A. Kelly

1906 J. Opt. Soc. Am. A/Vol. 7, No. 10/October 1990

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improved depth judgments involved in full-field stimula-tion. 8

The results of this first experiment revealed that bright-ness is indeed affected by ytl's. In order to determine themechanism mediating this effect, an additional experimentwas conducted. In the second experiment, brightness per-ception with the yellow and luminance-matched neutrallenses was measured during the cone plateau of the dark-adaptation curve. The results of these experiments indicatethat the signals from rods are affecting brightness judg-ments and that, when these signals are absent or minimized,ytl's no longer enhance perceived brightness.

METHODS

Experiment I-Effect of Target Size

SubjectsSixty subjects participated in the first experiment. Mostwere third-year students at the Illinois College of Optometryand had participated in a magnitude estimation experimentonce before, during their second year. The remainder wererecruited from the college faculty and support staff. Allsubjects were between 20 and 40 years old with correctedacuity of at least 20/20. They were screened for normalcolor vision with Ishihara pseudoisochromatic plates andhad good binocular vision according to the Wirt dot test.The subjects wore their normal correction during the experi-ment unless a tint was present, in which case the requiredcorrection was placed in a trial frame.

ApparatusThe yellow-tinted lenses were Norton Visitor Wraparoundglasses; the luminance-matched neutral pair were plasticsafety glasses with 93% transmittance. The spectral trans-mission curves were measured for each goggle pair with aspectroradiometer (Universal) and are given in Fig. 1. Thechromaticity coordinates of the yellow and neutral lensesilluminated by a tungsten-halogen bulb were x = 0.47-y =0.49 and x = 0.4 0-y = 0.40, respectively. The dominantwavelength was 578 nm for the ytl's. Luminance values ofthe tungsten white targets were measured with the lumi-

nance probe of a Tektronix photometer (J16). The ytl'swere luminance matched to the neutral lenses by hetero-chromatic flicker photometry. This procedure was carriedout for both small and large targets. The luminance decre-ment necessary for minimal flicker was obtained from theauthor as well as from two naive observers.

Stimuli were projected by a Kodak random-access projec-tor onto a flat matte screen. The illuminant was a tungsten-halogen bulb. The small-field targets were circular aper-tures that held neutral filters (Wratten #96) of varyingdensity (Life Sciences Associates). The target diametersubtended 5 deg at the eye. Nine circular targets were used,ranging from 0.2 to 80 cd/M2 . These targets ranged fromapproximately 1 to 4 log units above the absolute conethreshold. The edges of the target were blurred to eliminateboth slight variations in each target and possible opticalfactors that might contribute to enhanced brightness. Thelarge-field targets were constructed by mounting Wrattenneutral-density filters into rectangular slide holders. Thetarget subtended 15 deg X 20 deg at a distance of 2 m. Ninedifferent targets were constructed, covering the same lumi-nance range as the small target series. There was approxi-mately a 0.3-log-unit difference in luminance between eachpair of stimuli. A Uniblitz shutter that interfaced with aGerbrands digital timer was mounted on the random-accessprojector and used to control target duration.

ProcedureSubjects were tested two at a time, with one wearing yellowand one wearing neutral lenses. Testing was performed in adark room illuminated by two small red lamps and somestray light from the random-access projector. Instructionswere read to the subjects during a 5-min. adaptation period.

Subjects were told to fixate between two long-wavelengthLEDs and that a test target would be presented for 3 sec.every 15 sec. Subjects fixated on the visual target for thefull exposure duration and then recorded their magnitudeestimations. The subjects began by looking at the firsttarget and assigning a number that seemed to stand for themagnitude of the brightness. They then judged each suc-ceeding target with respect to the first so that, if the secondappeared twice as bright as the first, it was given a numbertwice as great, etc. A moderate stimulus luminance wasalways used first, since extremes have been shown to influ-ence the magnitude ofthe judgments made.' 6 Subjects wereallowed to use any positive number, including fractions anddecimals. Each of the nine target intensities was presentedtwice in a pseudo-random fashion (a moderate stimulus in-tensity was always presented first, and the dimmer targetsnever followed the most intense target). After 18 judgmentswere made, the subjects swapped goggles, and the experi-ment was repeated. Subjects were unaware of each other'sjudgments.

For all experiments, data were analyzed as follows: first,the two judgments made at each luminance were averagedfor a given subject, then the geometric mean and standarddeviations were calculated across subjects for each targetluminance.

Results and DiscussionThe brightness estimates obtained through the yellow andneutral lenses are plotted on log-log coordinates in Fig. 2(a)for the small field (n = 44) and Fig. 2(b) for the large field (n

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Susan A. Kelly


= 16). Magnitude estimates are plotted on the ordinate as afunction of stimulus luminance. Open symbols in this fig-ure and subsequent figures indicate results obtained withneutral lenses; closed symbols are results obtained with theytl's. Error bars here and in all subsequent figures indicate+1 standard deviation. Data obtained with the neutrallenses are well described by a power function with an expo-nent of 0.51.

Inspection of Fig. 2(a) indicates that, at the lower lumi-nance levels, brightness perception through the neutrallenses results in consistently higher magnitude estimations,but this difference is not statistically significant. At sevencd/M2 this trend reverses, and perceived brightness becomesgreater with ytl's. These data were analyzed by a 2 X 9repeated-measures analysis of variance. The interactioneffect of goggle X luminance was statistically significant (F

= 2.658, p = 0.007). Inspection of Fig. 2(a) indicates thatthe ytl's have a small effect over a 0.3-log-unit range ofstimulus luminance. The percent brightness difference be-tween the lenses is plotted in the upper panel as a function ofstimulus luminance. In this and subsequent figures, posi-tive values indicate that perceived brightness was greaterwith the ytl's; negative values indicate perceived brightnesswas greater with the neutral lenses.

Results obtained with the large field are plotted in Fig.2(b). The power function that describes the neutral lens

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data has an exponent of 0.37. The magnitude estimatesobtained with the ytl's systematically deviate from thoseobtained with neutral lenses over a range of -1 log unit atmoderate luminance levels. These data were also analyzedwith a 2 X 9 repeated-measures analysis of variance. Theinteraction effect of goggle X luminance was again statisti-cally significant (F = 2.308, p = 0.019). The percent-bright-ness difference between the lenses, plotted in the upperpanel, indicates that the effectiveness of the ytl's peaks at40% at approximately 10 cd/M2 then falls to an insignificantlevel near 80 cd/M 2.

These results reveal that the brightness of targets viewedthrough ytl's can be enhanced in comparison with lumi-nance-matched neutral stimuli. However, the enhance-ment effect is limited to the 1-log-unit range from 7 to 76 cd/m2 and is much more evident with the large field.

The abrupt appearance of the enhancement effect at sev-en cd/M2 is most likely due to the large energy differencebetween the cone achromatic and chromatic thresholds foryellow light.'7 It has been shown that, in the fovea, theenergy requirement for the chromatic threshold of a spec-trally saturated light is little more than that needed for theabsolute threshold, whereas for 570-nm light, the chromaticthreshold is approximately 10 times the absolute thresh-old.18 Although in the present study color appearance wasnot systematically investigated, a number of subjects volun-

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Fig. 2. Magnitude estimations of brightness as a function of stimulus luminance. Foveal fixation. Error bars, +1 standard deviation.Where the magnitude of the standard deviation exceeds the graph, only the upper limit is shown. The upper panel in both figures representsthe percent difference in magnitude estimates between ytl's and neutral lenses. (a) Magnitude estimates obtained with circular targets 5 deg indiameter, n = 44. (b) Magnitude estimates obtained with a 20 deg x 15 deg field, n = 16.

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tarily noted that the stimulus first appeared chromatic atseven cd/M2 . This was verified by observation. Thus theytl's did not enhance brightness until a chromatic perceptwas present.

That more extensive stimulation of the peripheral retinaresults in more extensive brightness enhancement suggestsseveral possible underlying mechanisms. The differentialeffects of field size could be due to changes in the pattern ofneural connections or changes in spatiotemporal responseproperties. It is also possible that the increased brightnessof the larger yellow field (with respect to the small field) isdue to the changes in saturation that accompany changes infield size.'9 However, it is also possible that the additionalstimulation of rods by the enlarged field is responsible forthe brightness enhancement. This possibility is strength-ened by noting that the end point of the enhancement effect(at approximately 80 cd/M 2 or 2.7 log scotopic Td) is coinci-dent with the psychophysical estimate of rod saturation.2 0

Experiment II was designed to evaluate the contributionof rods to the brightness-enhancement effect. Magnitudeestimates of brightness through ytl's and neutral lenses wereobtained during the cone plateau of the dark-adaptationcurve, when rod signals are assumed to be suppressed orabsent. These results were compared with the brightnessestimates obtained from the same observers in the un-bleached condition.

Experiment II-Brightness Estimates Obtained During theCone Plateau

SubjectsTwenty new subjects participated in Experiment II. Allwere recruited from the student body at the Illinois Collegeof Optometry. Their ages ranged from 22 to 30 years, andtheir eyesight was correctable to at least 20/20 with goodstereopisis and normal color vision.

ApparatusThe equipment used in this experiment was the same as thatdescribed above, with the exceptions of the tungsten lightsource, filters, and diffusing screen used to bleach the sub-jects. These materials are described below.

ProcedureSubjects were instructed to estimate the brightness of thesame 20 deg X 15 deg field using the magnitude estimationtechnique described above. These estimates were obtainedunder two conditions that differed only with respect to theadaptive state of rods. In the unbleached condition, sub-jects made brightness estimates through yellow and neutrallenses following a 20-min dark-adaptation period. In thebleached condition, subjects estimated brightness throughytl's and neutral lenses during the cone plateau of the long-term dark-adaptation curve. Before this, however, theywere exposed for 2.5 min to a 200-cd/M 2 adapting field illu-minated by a 100-W tungsten bulb. Subjects viewed theadapting field through a diffusing screen, infrared filter, andbroadband yellow filter (Kodak #9). Head position wasstabilized with a chin rest. Subjects then dark adapted forthe 3 min required to reach the cone plateau. The 15 deg X20 deg rectangular stimuli from Experiment I were used withthe exception of the dimmest target. The targets were pre-sented for 3 sec, with a 17-sec interstimulus interval. Each

of the eight targets was presented twice, resulting in sixteentrials per lens type. Thirty-two estimates were made inboth the bleached and unbleached conditions, resulting in atotal of sixty four brightness estimates per subject. The testsequence was counterbalanced so that half the subjects firstmade brightness estimates in the bleached condition whilethe remaining half first made brightness estimates in theunbleached condition.

Results and DiscussionThe results of this experiment are shown in Fig. 3. Figure3(a) plots brightness estimates obtained with the ytl's andneutral lenses in the unbleached condition. Figure 3(b)plots the results obtained from the same subjects throughthe same two pairs of lenses during the cone plateau. Eachdata point is the geometric mean of 20 magnitude estimates.The error bars indicate +1 standard deviation from themean. The top function in each panel plots the percentdifference between the yellow and neutral lenses as a func-tion of stimulus luminance. Perceived brightness is greaterwith the ytl's than with the neutral lenses at moderate lumi-nance levels in the unbleached condition. The enhance-ment effect of ytl's is minimal in the bleached condition. A2 X 2 X 8 repeated-measures analysis of variance revealedthat the main effects of lens type and adaptive state are notstatistically significant. However, the interaction effect be-tween adaptive state and luminance level was statisticallysignificant (F = 5.952, p < 0.001). This result indicates thatthe effect of bleaching depends on the luminance level of thestimulus. The data were further analyzed by comparing thedifference between yellow and neutral lenses under bleachedand unbleached conditions. A 2 X 8 repeated measuresanalysis of variance was used to evaluate each data set. Thisanalysis indicated that the goggle X luminance term wasstatistically significant in the unbleached condition (F =2.013, p = 0.057) but not in the bleached condition (F =0.602, p > 0.05). Thus the ytl's produced an enhancementeffect over a limited luminance range only in the unbleachedcondition.

The results of this second experiment indicate that theenhancement effect obtained with the large targets cannotbe attributed to cones. The many consequences of in-creased field size, such as changes in neural connections andsaturation, were present in both the bleached and the un-bleached conditions. The only difference between the twoconditions was the adaptive state of the rods. In one case,the rod system was desensitized by a bleaching exposure,and in the other, it was not. Thus it appears that theobserved enhancement effect is dependent on rod signals.However, the stimuli employed in this experiment were su-prathreshold, and it is possible that the most intense stimulicould have exceeded the scotopic threshold in the bleachedas well as the unbleached conditions. That this in fact didoccur however, is unlikely, since both the brightness andchromaticities of monochromatic lights have been reportedto remain invarient during the cone plateau, even with stim-uli four log units above the absolute cone threshold.2 Inaddition, the spectral sensitivity of parafoveal regionsmatched that of the rod-free fovea with the exception of therange of macular pigment absorption.2 1 Thus it seems un-likely that the brightness judgments made during the coneplateau were affected by rod stimulation.

Susan A. Kelly


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Fig. 3. Magnitude estimations of brightness as a function of stimulus luminance. Error bars, 41 standard deviation. Where the standard

deviation exceeds the graph, only the upper limit is shown. Upper panels in both figures represent the percent difference in magnitude

estimates between ytl's and neutral lenses. (a) Magnitude estimates obtained with the 20 deg X 15 deg field in the unbleached condition, n =

20. (b) Magnitude estimates for the 20 deg X 15 deg field obtained during the cone plateau for the long-term dark adaptation curve.

Brightness estimates were obtained between 3 and 9 min after the adapting light was extinguished, n = 20.

THEORETICAL IMPLICATIONSThe results of this study reveal that ytl's enhance brightnessby as much as 40%, once the chromatic threshold of the ytl'sis exceeded and the peripheral retina is stimulated. Theeffectiveness of these absorptive lenses is reduced if thetarget is decreased in size or presented while rods are desen-

sitized by exposure to a bleaching field. The enhancementeffect is also luminance dependent; its onset is coincidentwith the chromatic threshold, and its offset is coincidentwith rod saturation. These results suggest that rod signalsare responsible for the brightness enhancement since thereduction or elimination of rod signals results in the ineffec-tiveness of ytl's.

These data also indicate that activation of the chromaticpathway is important. The enhancement effect is initiatedonly once the chromatic threshold for the ytl's has been

exceeded. Indeed, ytl's and neutral lenses differ mainlywith respect to their effects on the chromatic pathway.Ytl's and neutral lenses were equated by heterochromaticflicker photometry and thus assumed equally to stimulatethe achromatic (luminance) channel. In addition, thebroadband yellow filter was equally effective for rods as for

the neutral pair. The difference in scotopic efficiency be-tween these lenses was less than 0.2 log unit. Thus any

difference in visual effectiveness between the yellow andneutral lenses must result from their differential effects onthe chromatic pathway.

Two stimuli that differ in chromaticity but are luminancematched by heterochromatic flicker photometry need notappear equally bright.2 2 23 The brightness of a chromaticstimulus that has been luminance matched to a standardwhite will be most underestimated when the chromatic stim-ulus is highly saturated or from the spectral extremes.24

Vector models of color vision, such as that of Guth and hiscolleagues, propose that luminance is mediated by the out-put of the achromatic channel, whereas brightness is mediat-ed by the chromatic channels as well.2 5 However, it is un-likely that the brightness enhancement observed in thepresent study is due to stimulation of the chromatic channelper se. The chromatic signal generated in response to amidspectral stimulus, such as yellow, is known to be theweakest in the spectrum. Indeed, when a yellow stimulus ismatched to a standard white, there is only a minimal differ-ence between the results obtained with heterochromaticflicker photometry and direct brightness matching.2 2

Kinney et al. suggested that ytl's achieve their beneficialeffects by enhancing the output of the chromatic channels incomparison to the neutral lens condition.5'8 The present

Susan A. Kelly

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results are consistent with this interpretation. However,the data from the present study also indicate that the rodsignals carried by the chromatic pathway mediate the en-hancement effect; stimulation of the chromatic channels perse is not a sufficient condition for brightness enhancement.Ytl's have minimal beneficial effect, following a strongbleach, with small targets or at luminance levels that exceedrod saturation, despite the presence of a chromatic percept.

There is experimental evidence to support the hypothesisthat rod signals contribute to or modulate the output of thechromatic channels, although the mechanism remains un-clear.2 6,27 The intrusion of rod signals has been shown toaffect the chromatic response by decreasing saturation,2 8

shifting hues,28,29 altering wavelength-discrimination func-tions,3 0 and elevating the specific (chromatic) threshold.3 'In addition, the large-field trichromatic color matches ofprotanopes and deuteranopes indicate that rod signals arecarried on the same channels that carry cone-chromatic in-formation.3 0 The magnitude estimation data reported inthis paper support this hypothesis but do not allow an inter-pretation of how rod and cone signals actually combine with-in the chromatic channels.

This question was specifically investigated by Benifmoffet al., who compared the brightness of either a rod-mediatedor a cone-mediated stimulus with the brightness of a combi-nation target that stimulated both rods and cones.32 Theirresults ruled out inhibitory interactions between rods andcones in the mediation of brightness. They reported a sum-mation of rod and cone signals that was greater than thatpredicted by probability summation. The data could befitted fairly well by assuming a vector addition between twoindependent channels (i.e., rods and cones). The data fromthe present study also indicate some type of summationbetween the rod and cone systems. Perceived brightnessincreases abruptly as the chromatic channels are stimulatedand then declines as the rods saturate. However, the specif-ic nature of the additivity between the rod and cone systemsmust await further investigation.

SUMMARY

The results support the long-reported subjective impressionthat ytl's enhance brightness. The conclusion that rod sig-nals are involved in the brightness-enhancement effect de-rives from three aspects of the experimental results: (1) theenhancement effect is more pronounced with a target thatstimulates the peripheral retina, (2) the enhancement effectdisappears at approximately 3 log scotopic Td, and (3) theenhancement effect is not evident when brightness is mea-sured while rods are desensitized by a bleach and cones arefully recovered.

The results also suggest that the rod signals generated inresponse to the ytl's are carried along one or both of thechromatic channels. The ytl's and neutral lenses were lumi-nance matched and had almost the same scotopic efficiency;thus any difference in visual consequence was ascribed toactivity within the chromatic channels. The combination ofrod and cone signals within this channel was additive ratherthan inhibitory, since magnitude estimates of brightnessincreased whenever the chromatic channels and the rodswere simultaneously stimulated. However, the nature of

the additivity and the locus of the enhancement effect can-not be determined from these results.

ACKNOWLEDGMENTS

The author gratefully acknowledges the comments on themanuscript made by Joel Pokorny. I thank Kenneth Alex-ander for several insightful discussions. I also thank DavidTanouye, Teresa Cuccia, and John Knuth for their assis-tance in data collection and analysis. This research wassupported by the Illinois College of Optometry Faculty Re-search Fund.

REFERENCES

1. B. A. J. Clark, "Color in sunglass lenses," Am. J. Optom. Arch.Am. Acad. Optom. 46, 825-840 (1969).

2. I. M. Borish, Clinical Refraction, 3rd ed. (Professional Press,Chicago, Ill., 1975), Vol. VII, pp. 1127-1130.

3. R. T. Jose, Understanding Low Vision (American Foundationfor the Blind, New York, 1983), p. 236.

4. J. Pokorny, C. H. Graham, and R. N. Lanson, "Effect of wave-length on foveal grating acuity," J. Opt. Soc. Am. 58, 1410-1414(1968).

5. J. Kinney, C. Schlichting, D. Neri, and S. Kindness, "Variousmeasures of the effectiveness of yellow goggles," Rep. 941 (Na-val Submarine Medical Research Laboratory, Groton, Conn.,1980).

6. S. Kelly, S. Goldberg, and T. Banton, "Effect of yellow tintedlenses on contrast sensitivity," Am. J. Optom. Physiol. Opt. 61,657-662 (1984).

7. S. M. Luria, "Vision with chromatic filters," Am. J. Optom.Arch. Am. Acad. Optom. 49, 818-829 (1972).

8. J. Kinney, C. L. Schlichting, D. Neri, and S. W. Kindness,"Reaction time to spatial frequencies using yellow and lumi-nance-matched neutral goggles," Am. J. Optom. Physiol. Opt.60, 132-138 (1983).

9. M. Yap, "The effect of a yellow filter on contrast sensitivity,"Ophthalmol. Physiol. Opt. 4, 227-232 (1984).

10. A. Bennett, "Tinted lenses to prescription," Optician, SpecialSuppl. (March 6, 1964), pp. 27-36.

11. W. D. Wright, Photometry and the Eye (Hatton, London,1949), pp. 62-63.

12. D. Miller, "The effect of sunglasses on the visual mechanism,"Surv. Ophthalmol. 19(1), 38-44 (1974).

13. S. Lerman, "Lens proteins and fluorescence," Isr. J. Med. Sci. 8,8-9 (1973).

14. S. Lerman, Radiant Energy and the Eye (Macmillan, NewYork, 1980), Vol. 1, 142-143.

15. F. Campbell and R. Gubisch, "The effect of chromatic aberra-tion on visual acuity," J. Physiol. 192, 345-358 (1967).

16. L. E. Marks, Sensory Processes: The New Psychophysics (Ac-ademic, New York, 1974), 131-133.

17. J. Pokorny, R. Bowen, D. Lindsey, and V. Smith, "Durationthresholds for chromatic stimuli," J. Opt. Soc. Am. 69, 103-106(1979).

18. C. H. Graham and Y. Hsia, "Saturation and the foveal achro-matic interval," J. Opt. Soc. Am. 59, 993-997 (1969).

19. L. Hurvich, Color Vision (Sinauer, Sunderland, Mass., 1981), p.162.

20. M. Aguilar and W. Stiles, "Saturation of the rod mechanism ofthe retina at high levels of illumination," Opt. Acta 1, 59-65(1954).

21. U. Stabell and B. Stabell, "Absence of rod activity from periph-eral vision," Vision Res. 16, 1433-1438 (1976).

22. G. Wagner and R. Boynton, "Comparison of four methods ofheterochromatic photometry," J. Opt. Soc. Am. 62, 1508-1555(1972).

23. P. Kaiswer and J. Comerford, "Flicker photometry of equallybright lights," Vision Res. 15, 1399-1402 (1975).

Susan A. Kelly


24. S. Burns, V. Smith, J. Pokorny, and A. Elsner, "Brightness ofequal-luminance lights," J. Opt. Soc. Am. 72, 1225-1231 (1982).

25. S. Guth and H. Lodge, "Heterochromatic additivity, foveal

spectral sensitivity, and a new color model," Vision Res. 17,450-462 (1977).

26. V. Smith and J. Pokorny, "Large-field trichromacy in prota-nopes and deutranopes," J. Opt. Soc. Am. 67, 213-220 (1977).

27. K. H. Ruddock, "Parafoveal colour vision responses of fourdichromats," Vision Res. 11, 143-156 (1971).

28. U. Stabell and B. Stabell, "The effect of rod activity on colourmatching functions," Vision Res. 15, 1119-1123 (1975).

29. B. Stabell and U. Stabell, "Rod and cone contributions to pe-ripheral colour vision," Vision Res. 16, 1099-1104 (1976).

30. U. Stabell and B. Stabell, "Wavelength discrimination of pe-ripheral cones and its change with rod intrusion," Vision Res.17, 423-426 (1977).

31. B. Stabell and U. Stabell, "Effects of rod activity on colorthreshold," Vision Res. 16, 1105-1110 (1976).

32. N. Benimoff, S. Schneider, and D. Hood, "Interactions betweenrod and cone channels above threshold: a test of various mod-els," Vision Res. 22, 1133-1140 (1982).

Susan A. Kelly

effect of yellow-tinted lenses on brightness

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