Mean Pupil Diameter Research Articles

Changes in chromatic and achromatic contrast sensitivities following tropicamide administration

To investigate the effects of tropicamide on chromatic and achromatic contrast sensitivities over the physiological range of spatial frequencies. A total of 26 healthy volunteers, with a mean age of 32 years, were examined with and without one drop of 1% tropicamide being administered 30 min previously. On each occasion, acuity and pupil diameter were recorded, and chromatic and achromatic contrast sensitivities were examined using the Sussex Grating Machine. Following tropicamide administration mean pupil diameter increased from 4.1 mm to 7.2 mm (P<0.001), and mean BCVA was reduced by 0.07 LogMar units (P<0.001). Achromatic contrast sensitivity was significantly reduced following tropicamide administration at 2.20 cycles per degree (cpd) (P=0.01), 3.40 cpd (P=0.01), 10 cpd (P=0.04), 17 cpd (P=0.04), and 25 cpd (P<0.01). There was no difference in contrast sensitivity at lower spatial frequencies (0.33 and 0.66 cpd). Chromatic contrast sensitivity was not significantly altered when tested along the red-green and tritan confusion axes. Achromatic contrast sensitivity is significantly reduced following tropicamide administration at intermediate and high spatial frequencies. No significant changes were seen at low spatial frequencies and in chromatic contrast sensitivities.

Measurement of the spatial shift of the pupil center

Purpose To evaluate the effectiveness of the pupil center as an anatomic landmark for excimer laser treatments. Setting Sekal-Microchirurgia-Rovigo Centre, Rovigo, Italy. Methods Pupillometry with the Costruzione Strumenti Oftalmici S.R.L. (CSO) pupil-measuring module (incorporated in Eye Top videokeratoscope) was performed in 52 patients with a diagnosis of myopia and in 25 patients with a diagnosis of hyperopia. Measurements both in mesopic and photopic conditions consisted of pupil diameters, spatial shift of the pupil center, and the distance between the pupil center and keratoscopic axis. Results The mean pupil diameter in photopic conditions of illumination in myopic eyes was 3.52 mm ± 0.56 (SD), while in mesopic conditions it was 5.37 ± 0.78 mm; in hyperopic eyes the mean photopic pupil diameter was 3.01 ± 0.46 mm, while the mean mesopic diameter was 5.12 ± 0.48 mm. The mean spatial shift of the pupil center in myopic eyes was 0.086 mm (maximum 0.269 mm), while in the hyperopic eyes it was 0.095 mm (maximum 0.283 mm). The mean distance between the pupil center and keratoscopic axis in myopic eyes was 0.226 ± 0.13 mm (maximum 0.75 mm), while in hyperopic eyes it was 0.45 ± 0.19 mm (maximum 0.8 mm). Conclusions The mean of the measured pupil sizes was greater in myopic eyes than in hyperopic eyes. The spatial shift of the pupil center, as the pupil dilates, was relatively small in all groups; therefore, the pupil center is a good anatomic landmark for both traditional refractive surgery and wavefront-guided treatments. The mean distance between the keratoscopic axis and pupil center was greater in the hyperopic group than in the myopic group. Therefore, centration of any laser treatment on the basis of the keratoscopic analysis should be done carefully, especially in hyperopic eyes and in cases in which the pupil center is meaningfully shifted from keratoscopic axis, even in photopic conditions of illumination.

Measurement of the spatial shift of the pupil center

To evaluate the effectiveness of the pupil center as an anatomic landmark for excimer laser treatments. Sekal-Microchirurgia-Rovigo Centre, Rovigo, Italy. Pupillometry with the Costruzione Strumenti Oftalmici S.R.L. (CSO) pupil-measuring module (incorporated in Eye Top videokeratoscope) was performed in 52 patients with a diagnosis of myopia and in 25 patients with a diagnosis of hyperopia. Measurements both in mesopic and photopic conditions consisted of pupil diameters, spatial shift of the pupil center, and the distance between the pupil center and keratoscopic axis. The mean pupil diameter in photopic conditions of illumination in myopic eyes was 3.52 mm +/- 0.56 (SD), while in mesopic conditions it was 5.37 +/- 0.78 mm; in hyperopic eyes the mean photopic pupil diameter was 3.01 +/- 0.46 mm, while the mean mesopic diameter was 5.12 +/- 0.48 mm. The mean spatial shift of the pupil center in myopic eyes was 0.086 mm (maximum 0.269 mm), while in the hyperopic eyes it was 0.095 mm (maximum 0.283 mm). The mean distance between the pupil center and keratoscopic axis in myopic eyes was 0.226 +/- 0.13 mm (maximum 0.75 mm), while in hyperopic eyes it was 0.45 +/- 0.19 mm (maximum 0.8 mm). The mean of the measured pupil sizes was greater in myopic eyes than in hyperopic eyes. The spatial shift of the pupil center, as the pupil dilates, was relatively small in all groups; therefore, the pupil center is a good anatomic landmark for both traditional refractive surgery and wavefront-guided treatments. The mean distance between the keratoscopic axis and pupil center was greater in the hyperopic group than in the myopic group. Therefore, centration of any laser treatment on the basis of the keratoscopic analysis should be done carefully, especially in hyperopic eyes and in cases in which the pupil center is meaningfully shifted from keratoscopic axis, even in photopic conditions of illumination.

Oxybutynin appears to decrease accommodation amplitude, tolterodine appears to increase mean pupillary diameter in dim light,

Oxybutynin appears to decrease accommodation amplitude, tolterodine appears to increase mean pupillary diameter in dim light,

Oxybutynin appears to decrease accommodation amplitude, tolterodine appears to increase mean pupillary diameter in dim light,

Oxybutynin appears to decrease accommodation amplitude, tolterodine appears to increase mean pupillary diameter in dim light,

Steepening of corneal curvature with contraction of the ciliary muscle

To measure the changes of corneal curvature during contraction of the ciliary muscle. Department of Ophthalmology, St. Luke's International Hospital, Tokyo, Japan. Twenty-eight eyes of 14 healthy volunteers under 40 years old were enrolled in this prospective randomized controlled study and divided into pilocarpine and control groups. Intraocular pressure (IOP), pupil diameter, and corneal topography were measured before and 40 minutes after instillation of topical pilocarpine 4% or balanced salt solution. Corneal topography was analyzed for the mean ring-power of Placido rings 1 through 25, average corneal power (ACP), and for spherical equivalent, regular astigmatism, asymmetry, and high-order irregularity by Fourier analysis. Pilocarpine had no effect on IOP, but it did cause a significant decrease in mean pupil diameter. Simultaneously, pilocarpine increased the mean ring powers for Placido rings 1 through 4 and the ACP (+0.13 diopters (D) +/- 0.17 [SD]; P=.017). By Fourier analysis, the mean spherical component for the central 3.0 mm of the cornea increased in the pilocarpine group (+0.08 +/- 0.15 D; P=.020). There were no changes in components of regular astigmatism, asymmetry, and high-order irregularity. The central cornea steepened in curvature and increased in power owing to contraction of the ciliary muscle. The results suggest that changes in corneal curvature increase refractive power during accommodation.

Vermessung der skotopischen Pupille im Vergleich zwischen Grünlichttest und Wellenfrontanalyser WASCA

The aim of this study was to compare the accuracy and the reproducibility of scotopic pupil measurements using 2 different methods. Scotopic pupil diameter was measured in 56 eyes of 28 volunteers and the results were compared between the green light test at the slit lamp (Haag-Streit, Switzerland) and the automatic measurements of the wave-front analyser WASCA (Carl-Zeiss-Meditec) by 2 independent examiners. Non-parametric sign test as well as All Pairwise Multiple Comparison Procedures (Student-Newman-Keuls method) were performed for the comparison of means for each individual eye as well as the results of both eyes tested by both examiners. Mean age of the subjects was 34.9 years. The colour of iris was green or blue in 22 cases and brown in 6 cases. REPRODUCIBILITY: For the green light test we found for the first investigator in the right eye a mean pupil diameter of 6.58 mm (SD 0.68). The measurement of the second investigator for the same eye was 6.64 mm (SD 0.61). The left eye values were as follows: 6.36 mm (SD 0.68) and 6.75 mm (SD 0.68). For WASCA we found for the first investigator in the right eye 6.33 mm (SD 0.64) vs. 6.30 mm (SD 0.64) for the second investigator, in the left eye 6.39 mm (SD 0.69) vs. 6.36 mm (SD 0.60). There was a statistically significant difference between the two investigators when the green light test was used (6.47 mm vs. 6.69 mm for both eyes). No difference was found using the WASCA integrated pupillometer (6.35 mm vs. 6.33 mm). There was a significant difference between the means of combined data for both measurement methods: 6.58 mm for the green light test (SD 0.57) vs. 6.34 mm for WASCA (SD 0.62). The integrated pupillometry of the WASCA analyser showed better reproducibility of measurements than the green light test. The green light test measures a slightly larger diameter (in the mean by 0.25 mm) than WASCA. Because of the fair and clinically sufficient reproducibility as well as virtually non-existing additional costs the green light test can be strongly recommended to referring ophthalmologists and low-volume refractive surgeons.

Scotopic measurement of normal pupil size with the Colvard pupillometer and the Nidek auto-refractor

Purpose: To compare prospectively, pupil size with the Nidek AR700A auto-refractor and the Colvard pupillometer. Methods: Pupil diameter was measured in 46 eyes at 2 min intervals in a low mesopic and under photopic light conditions. Results: The mean pupil diameter was 4.8 ± 1.0 mm with the Colvard pupillometer and 4.8 ± 0.9 mm with the Nidek auto-refractor in low mesopic light conditions. The mean photopic pupil diameter was 3.3 ± 0.8 mm with the Colvard pupillometer and 3.9 ± 0.8 mm with the Nidek auto-refractor. Conclusion: The pupil sizes are very similar with both instruments.

Duration of pupillary constriction in response to a photographic flash

Reply: We are pleased to receive insightful comments on our work by Brown and coauthors. They raise several important methodology issues with respect to studies of pupil measurement that deserve further discussion and wider consideration. Brown and coauthors suggest that our study was intended to measure the pupil under dark-adapted conditions. This, however, was not our intent. We make a strict distinction between the dark-room conditions described in our study and true dark adaptation, which we reserve for the unique physiological state of rod-driven retinal sensitivity occurring after approximately 35 minutes of complete darkness in the normal eye.1 Brown and coauthors are rightly concerned that the time interval between the first flash exposure and subsequent measurements by the second examiner could have been insufficient for full pupil recovery. If the order of examiner was not randomized, this would lead to a sequence effect whereby the second examiner would measure a consistently smaller pupil size. They provide a plot of pupil size as a function of time in 2 eyes photographed using their recently published technique2 to illustrate this point. In our original publication, we reported that examiner order was arbitrary. In fact, 1 examiner was first in all but 2 cases. This provided an opportunity to test Brown and coauthors' hypothesis. Using a 2-way repeated measures analysis of variance (ANOVA) model, we compared the mean pupil size measured at each light level across examiners and also tested for an interaction between examiner and light level for the digital photographic method of measurement. If the concerns expressed by Brown and coauthors were a factor in our experiments, we would expect to find a significant interaction between these 2 variables. We found no interaction between light level and examiner (Figure 1; P=.09) and no difference between the 2 examiners in pupil size measurements (P=.20).Figure 1.: Mean measured pupil diameter by examiner as a function of light level for the photographic measurement method.Because any observed differences in pupil size could be due to examiner effects or sequence effects, we further explored their concern by testing for differences between examiners in mean pupil diameter with a 2-way ANOVA comparing light level across methods of measurement for each examiner sequence (examiner 1 then examiner 2; examiner 2 then examiner 1). We did not find a significant sequence effect on pupil size when we compared light levels by method interactions or method of measurement for either test sequence and show the comparison of pupil size by light level for each examiner (Figure 1). These findings should satisfy the concerns expressed by Brown and coauthors. Although the concern about an examiner sequence effect is valid and they identify a methodological weakness of our design, it did not influence our reported results. Brown and coauthors suggest that the time between photographs was not controlled or measured. Although we elected not to report these data, they were recorded and provide further evidence to allay their concerns. We show the difference between examiners for pupil diameter measurements as a function of time (Figure 2). The slope of this function was not significantly different than zero by linear regression (−0.018 mm/min; 95% confidence interval −0.050 to +0.014). The time between pupil measurements was 3.5 minutes at the medium light level (5 lux) and 4.3 minutes at the low light level (<0.63 lux).Figure 2.: Difference in measured pupil diameter between examiner 1 and examiner 2 as a function of the time difference between the 2 measurements. Number = 45 (×3 light levels); r 2 = 0.00, P = .98, Y = (0.130)X. The slope of this function was not statistically different than zero.A second hypothesis proposed by Brown and coauthors is that the variations observed in pupil size measurements with the Colvard pupillometer were possibly due to a prolonged tonic proximal accommodative response, and they suggest that we repeat our study with a randomized examiner order to address this issue. This raises another important concern of any pupil measurement study; namely, control of accommodation. The normal time course of pupil recovery from a convergent accommodative stimulus is seconds.3 Given that more than 2 minutes had passed between each examiner's measurements, the pupil should have had sufficient time to completely recover from an accommodative stimulus. We are grateful for the comments of Brown and coauthors and appreciate the opportunity to respond to their concerns. Michael Twa OD Melissa Bailey OD, PhD Mark Bullimore MCOptom, PhD John Hayes PhD

Duration of pupillary constriction in response to a photographic flash

We read with interest the recent article by Twa et al.1 concerning the clinical measurement of pupil diameter (PD) using digital flash photography. Although not explicitly stated, it appears that the authors' intention was to measure the dark-adapted pupil diameter (DAPD) at <1 lux and at 5 lux. Digital photography was performed with the Nikon CoolPix 990 camera using the auto-flash setting at 17 cm. First, a 10-second infrared video clip was taken followed by a flash photograph; the subject was allowed to readapt for 2 minutes, and then another examiner repeated the video and photograph. It is unlikely that the second digital photograph was taken exactly 2 minutes and 10 seconds after the first one, but the interval between them was not measured. We were concerned that incomplete dark adaptation at the time of the second photograph might be a source of experimental error. Two of us (J.C.B., A.M.K.) conducted the following experiment: After dark adaptation at 5 lux for 5 minutes, an infrared still digital photograph of 1 eye was taken with an infrared-capable digital video camera using our customary technique2; following this, a Nikon CoolPix 990 camera was held 17 cm from the subject and an auto-flash photograph was taken, although no effort was made to focus it. At 2, 5, and 10 minutes after the flash, infrared photographs were repeated (Figure 1).Figure 1.: Pupil diameter plotted as a function of the timing of the infrared photograph after the digital camera flash. Neither pupil returned to baseline by 10 minutes. The measurement errors induced by incomplete readaptation at 5 minutes were 0.18 mm and 0.35 mm. Multiple flashes (required in 4% of subjects tested by Twa et al.) would exacerbate the problem. Baseline = dark adaptation at 5 lux for 5 minutes.In Twa et al., 2 investigators tested subjects in an “arbitrary” examiner order and the results of examiner 1 versus examiner 2 were statistically analyzed. Analysis of the first versus the second examination for each test would be interesting. If the examiner order was not randomized, a test performed by examiner 1 might frequently also be examination 1, which could induce systematic inter-examiner errors related to the unrecognized duration of the flash-induced PD reduction (Figure 2).Figure 2.: Measured mean pupil diameter plotted in the (speculative) test sequence, in which examiner 1 performed a nonrandom majority of the photographic testing before examiner 2. For measurements taken at 0.63 lux, a steady downward trend can be identified. Measurements at 5 lux do not show this trend, but they would if the examiners had reversed order so examiner 2 was more frequently performing the examination first (data from Table 3, Twa et al.1).This is speculative analysis, but it deserves further consideration by the authors because it illustrates 2 major sources of test artifact when measuring the DAPD: incomplete retinal dark adaptation, especially after brief exposure to a bright light source, and involuntary accommodation or psychogenic awareness of near. Along the same line, might the consistently smaller Colvard pupillometer measurements of examiner 2 be due to residual accommodative miosis induced by the first pupillometer measurement? Although the authors took pains to discourage accommodation, randomized examiner sequence is the only way to rule out accommodation as a confounding variable. We encourage the authors to analyze and report their data based on the examination sequence and also to repeat the Colvard pupillometer measurements with a randomized examiner order. Sandra M. Brown MD Jay C. Bradley MD Arshad M. Khanani MD Lubbock, Texas, USA

Vergleich verschiedener Pupillometrieverfahren unter mesopischen und skotopischen Bedingungen

The aim of the study was to compare different methods for pupillometry, namely the Goldmann perimeter (gp), the Colvard pupillometer (cp) and the Procyon Video pupillometer (pvp). For the pvp three different illuminations were available: mesopic high, mesopic low, and scotopic. The size of the pupil was measured in 100 eyes (50 healthy subjects) with the three different methods. We examined 29 females (58 %) and 21 males (42 %) with an average age of 25.16 years, ranging from 18 to 30 years. For the Goldmann perimeter, a mean pupil diameter of 4.39 mm +/- 0.62 mm was found under mesopic conditions (1.40 lux). For the Colvard pupillometer for scotopic conditions (0 lux), a mean pupil diameter of 6.80 mm +/- 0.81 mm was found. For pvp the pupil diameter ranged from 7.06 mm +/- 0.71 mm for scotopic (0.04 lux), over 6.24 mm +/- 0.80 mm for mesopic low (0.40 lux) to 4.65 mm +/- 0.73 mm for mesopic high conditions (4.00 lux). The comparison of the results showed a high correlation between the Goldmann perimeter and the Procyon Video Pupillometer for mesopic high with a minimum difference of 0.25 +/- 0.69 mm. By addition of 2.67 mm to the mesopic measurement of the Goldmann perimeter, the results for the Procyon Video pupillometer at the scotopic level, by addition of 2.4 mm the scotopic measurement of the Colvard pupillometer could be achieved.

Static and dynamic analysis of the anterior segment with optical coherence tomography

To study biometric modifications of the anterior segment with accommodation and age and determine possible applications in areas of anterior segment surgery, particularly implantation of refractive lenses. Clinique Monticelli, Marseille, France. The study comprised subjects between 7 years of age and 82 years of age in whom anterior chamber biometry was evaluated using 1,310 nm wavelength optical coherence tomography (OCT). The equipment has a fixation target that can be focused and defocused with negative lenses to stimulate natural accommodation. All measurements were performed by the same operator. The horizontal diameter of the AC, the anterior chamber depth (ACD), the horizontal pupil diameter, and the horizontal radius of curvature of the crystalline lens' anterior pole were measured in the unaccommodated state and after stimulating accommodation. Fifty-six subjects (104 eyes) were included; the refractions ranged from +5.0 diopters (D) to -5.0 D. The static and dynamic measurements were compared with ametropia, age, and accommodation. At rest, the mean AC diameter was 12.334 mm, the mean ACD was 3.106 mm, and the mean pupil diameter was 4.258 mm. With 1.0 D of accommodation, the anterior pole moved forward by a mean of 30 microm, the radius of curvature decreased 0.3 mm, and the pupil diameter decreased 0.15 mm. The AC OCT is a user-friendly instrument for evaluating the anterior segment and examining the AC (cornea, iris, crystalline lens, and iridocorneal angle). The 1,310 nm light wavelength is blocked by pigments, preventing examination behind the iris. However, the AC OCT is capable of good image quality and visualization of the anatomical relationships in the anterior segment, even behind an opaque cornea.

Reduction of pupil size and halos with minus lenses after laser in situ keratomileusis.

To evaluate the amount of miosis induced by over-minused lenses and to assess subjective reduction of halos following laser in situ keratomileusis (LASIK) with such lenses. Part I: Infrared pupil diameter was assessed in 14 patients who had not had ocular surgery. The accommodative/miotic reflex was stimulated with concave trial lenses in -1.00-D increments up to -4.00 D while viewing the 20/40 acuity line. Part II. Subjective halos around a distant light were assessed in 14 patients following LASIK for myopia, with and without a -1.00-D lens over manifest refraction. Part I: 100%, 79%, and 64% of patients clearly saw the 20/40 line with a -1.00-D lens, -2.00-D lens, and -3.00/-4.00-D lens, respectively. Mean pupil diameter decreased by 0.2 mm with the -1.00-D lens (P = .02), 0.5 mm with the -2.00-D lens (P = .003), 0.9 mm with the -3.00-D lens (P = .008,), and 1.1 mm with the -4.00-D lens (P = .008). Part II: 11 of 14 patients (79%) noticed a decrease in the size of the halo (30% average reduction) when over-minused by -1.00 D. Pupil diameters and halos decreased with a -1.00-D overcorrection in patients following LASIK. Patients with pupil-dependent night halos after LASIK may benefit from mildly over-minused lenses.

Effect of pupillary dilation on retinal nerve fiber layer thickness measurements using optical coherence tomography.

To evaluate the effect of pupillary dilation on retinal nerve fiber layer thickness (RNFL) measurements using optical coherence tomography (OCT-3). Randomly chosen eyes of healthy individuals were scanned before and after pupillary dilation by two trained operators (R.G.O., R.V.) using OCT-3 (Carl Zeiss Meditec, Inc., Dublin, CA). Fast and regular RNFL (256 A-scans) OCT-3 protocols (software version A1.1) were used in each scanning session. RNFL thickness measurements before and after dilation were compared. Ten eyes of 10 subjects (6 females, 4 males) were enrolled. Mean age was 32.0 +/- 11.2 years (range, 21 to 52 years). Mean pupillary diameter before and after dilation was 2.9 +/- 0.6 mm and 7.6 +/- 0.8 mm, respectively (P < 0.0001, paired t-test). There was no significant difference in RNFL thickness measurements before and after dilation using both fast and regular RNFL protocols (P > or = 0.05 for all comparisons, paired t-test). Mean coefficients of variation for mean RNFL thickness measurements were 15.3% before and 13.7% after dilation for operator 1; and 10.8% before and 12.7% after dilation for operator 2 for the fast RNFL protocol and 11.3% versus 10.4% and 12.9 versus 11.1%, respectively, for the regular RNFL protocol. Pupillary dilation is not necessary in all subjects to obtain reproducible RNFL thickness measurements using OCT-3.

Double-pass measurement of retinal image quality in the chicken eye.

The chicken, Gallus gallus domesticus, is used as an animal model to study the development of refractive error. Although vision is important in determining the eye's refractive state, relatively little is known about the retinal image quality of the chicken eye. An objective double-pass technique was used to measure the optical quality of the eyes of White Leghorn chickens. Measurements were made on 21 eyes of six untreated birds and eight experimental birds that were members of a study of refractive development. Ages ranged from 3 to 6 weeks, and refractions ranged from -1.29 to +0.58 D in the untreated eyes and -4.58 to +10.17 D in the experimental eyes. The measurements were made under general anesthesia combined with either cycloplegia or ciliary nerve section. Proper optical alignment of the eye was achieved with the aid of a TV monitor, CCD camera, and an infrared source. A 543-nm laser point source was focused on the retina, and the double-pass aerial image was collected by a high-resolution CCD camera. Refractive errors were corrected with trial lenses, using a bracketing method to optimize the retinal images. Both the full width at half-maximum of the double-pass aerial image and the single-pass modulation transfer function were used as objective estimates of the optical quality. The mean full width at half-maximum value in eyes of the untreated birds was 1.60 min arc for a 4.50-mm mean pupil diameter. Optical quality tended to be worse in the experimental myopic eyes. The optical quality of the chicken eye measured under monochromatic conditions meets or may even exceed the neural limits of spatial acuity based on anatomical estimates of ganglion cell spacing. The data also suggest that optical quality is worse in myopic eyes, which is consistent with studies of human eyes.

Comparison of scotopic pupil measurement with slitlamp-based cobalt blue light and infrared video-based system

Purpose To determine the accuracy and reproducibility of scotopic pupil measurements with a slitlamp-based cobalt blue light. Setting University of Texas Health Science Center−San Antonio, San Antonio, Texas, USA. Methods In a prospective experimental study, 2 independent observers measured 16 subjects’ pupils with a standard slitlamp-based cobalt blue light. In the same setting, the accuracy and reproducibility of the measurements were compared with those obtained with an infrared video-based system. Results Measurements of pupil size using the infrared video−computer system were highly reproducible. With the slitlamp-based cobalt blue light, the 2 measurements obtained by observer 2 (n = 16) were very close to each other (mean difference 0.09 mm ± 0.23 [SD]; P = .12), whereas those obtained by observer 1 (n = 16) were slightly different from each other (mean difference 0.18 ± 0.33 mm; P = .043). The mean pupil diameter measured with cobalt blue light was not significantly different between the 2 observers ( P > .05), and the measurements were highly correlated with each other ( r = 0.96, P < .01). The mean difference between the measurements using cobalt blue light and the infrared video−computer system was 0.21 ± 0.54 mm for observer 1 ( P = .47) and 0.06 ± 0.47 mm for observer 2 ( P = .85). Good correlation was noted between the measurements taken from each measuring device for both observers ( r = 0.87 and 0.90, P < .01). Conclusion Slitlamp-based cobalt blue light provided a reasonably good measurement of scotopic pupil size. It correlated well with the infrared video system when used at the lowest setting by experienced personnel. However, the observed difference between the measurements obtained by the 2 devices indicates that the cobalt blue light should be used cautiously in the refractive surgery preoperative evaluation of patients with large pupils.

The impact of dark adaptation on photoscreening

Purpose: Some previous studies have used different dark adaptation periods to achieve adequate pupil dilation for photo refraction. Because efficient use of time is important in screening programs, we investigated how dark adaptation affects the quality of eye photographs. Methods: This prospective study was done on 2 groups. In the first group (40 patients), 1 horizontal flash and 1 vertical flash photograph were taken as soon as the room lights were turned off, and a second set of photographs was taken after 10 minutes of dark adaptation. In the second group (37 patients), sets of photographs were taken after 1, 5, and 15 minutes of dark adaptation. Pupillary diameters were measured by an observer who was masked to the timing of the photographs. The findings were compared using the Wilcoxon signed rank test and the Student t test for paired data. Results: Compared with the results at 1 minute, mean pupillary diameter was significantly decreased after 10 minutes of dark adaptation, both with the horizontal (Z = -4.723; P <.001) and the vertical flash (Z = -4.668; P <.001) in the first group. In the second group, the mean pupillary diameters at 1, 5, and 15 minutes in the horizontal flash photos were 5.78 ± 1.03 mm, 5.35 ± 1.10 mm, and 5.04 ± 1.05 mm, respectively, and were 5.70 ± 0.95 mm, 5.21 ± 1.09 mm, and 4.86 ± 0.95 mm, respectively, in the vertical flash photos at these stages. These diameters were all significantly different (P <.001). Conclusion: The results indicated that dark adaptation is not a prerequisite for photoscreening, and that, in fact, it might have an adverse effect on pupillary diameter. (J AAPOS 2002;6:315-8)

Pupil size following dark adaptation in patients with retinitis pigmentosa.

According to the equivalent light hypothesis, molecular defects in the photoreceptor lead to a continuous activation of the photoreceptor cascade in a manner equivalent to real light. The consequences in diseases such as retinitis pigmentosa (RP) are as disruptive to the cells as real light. Two forms of the equivalent light hypothesis can be distinguished: strong - mutations in rhodopsin or other cascade proteins in some forms of RP continuously excite the visual phototransduction cascade; weak - disruption of outer segments in all patients with RP eliminates circulating dark current and blocks neurotransmitter release in a manner similar to real light. Both forms of the equivalent light hypothesis predict that pupils of patients with RP will be constricted like those of normal subjects in the light. The purpose of this study was to test the equivalent light hypothesis by determining whether steady-state pupil diameter following full dark adaptation is abnormally small in any of a sample of patients with RP. Thirty-five patients with RP and 15 normal subjects were tested. Direct steady-state pupillometric measures were obtained from one eye in a full-field dome after 45 min of dark adaptation by videotaping the pupil with an infrared camera. Mean pupil diameter in the dark was comparable (t = -0.15, P = 0.88) between patients with RP (6.85 +/- 0.58 mm) and normal subjects (6.82 +/- 0.76 mm). The results of the present study are clearly counter to the prediction of the second (weaker) form of the equivalent light hypothesis.

Eye Activity Correlates of Workload during a Visuospatial Memory Task

Changes in six measures of eye activity were assessed as a function of task workload in a target identification memory task. Eleven participants completed four 2-hr blocks of a mock anti-air-warfare task, in which they were required to examine and remember target classifications (friend/enemy) for subsequent prosecution (fire upon/allow to pass), while targets moved steadily toward two centrally located ship icons. Target density served as the task workload variable; between one and nine targets were simultaneously present on the display. For each participant, moving estimates of blink frequency and duration, fixation frequency and dwell time, saccadic extent, and mean pupil diameter, integrated over periods of 10 to 20 s, demonstrated systematic changes as a function of target density. Nonlinear regression analyses found blink frequency, fixation frequency, and pupil diameter to be the most predictive variables relating eye activity to target density. Participant-specific artificial neural network models, developed through training on two or three sessions and subsequently tested on a different session from the same participant, correlated well with actual target density levels (mean R = 0.66). Results indicate that moving mean estimation and artificial neural network techniques enable information from multiple eye measures to be combined to produce reliable near-real-time indicators of workload in some visuospatial tasks. Potential applications include the monitoring of visual activity of system opetators for indications of visual workload and scanning efficiency.

Scotopic measurement of normal pupils: Colvard versus Video Vision Analyzer infrared pupillometer

Purpose To prospectively measure the scotopic pupil diameter in a normal population and to compare 2 infrared pupillometers for these measurements. Setting Johann Wolfgang Goethe-University, Department of Ophthalmology, Frankfurt am Main, Germany. Methods The Colvard infrared pupillometer was compared to the Video Vision Analyzer (VIVA) infrared pupillometer under scotopic light conditions in 33 participants (aged 19 to 55 years). Reliability was assessed by 2 independent examiners (E1, E2). Statistical analysis was performed using a comparison method by Bland and Altman. Results Mean pupil diameter was 6.16 mm ± 1.20 (SD) (range 3.20 to 9.00 mm) with all measurements taken under scotopic illumination. The mean scotopic pupil diameter was 6.08 ± 1.16 mm (range 3.2 to 8.4 mm) with the Colvard pupillometer and 6.24 ± 1.28 mm (3.5 to 9.0 mm) with the VIVA pupillometer. The mean differences between the Colvard and VIVA were −0.27 mm (E1) and −0.05 mm (E2). Limits of agreement ranged from 1.4 (Colvard) to 2.4 (VIVA). The coefficients of repeatability ranged from 0.7 (Colvard) to 1.1 (VIVA). Conclusions A mean scotopic pupil diameter of 6.15 mm with a maximal pupil size of 9.00 mm can be expected in a normal population; this should be considered in refractive corneal and refractive lens surgery. Measurements with the Colvard pupillometer were more reliable and precise than those with the VIVA pupillometer.