Journal of Refractive Surgery

Original Article Supplemental Data

Measurement of Pupil Center Shift in Refractive Surgery Candidates With Caucasian Eyes Using Infrared Pupillometry

Imene Salah Mabed, MSc; Alain Saad, MD; Emmanuel Guilbert, MD; Damien Gatinel, MD

Abstract

PURPOSE:

To evaluate the effectiveness of the pupil center shift with changes in the state of pupil size and with other ocular variables.

METHODS:

Dynamic pupillometry with the Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX) was performed in 248 eyes of 124 patients scheduled for corneal laser refractive surgery. High-resolution images were obtained using the infrared-sensitive camera (incorporated in the videokeratoscope) under mesopic and photopic conditions. Measurements of pupil diameters, distance between the pupil center and keratoscopic axis, and spatial shift of the pupil center were obtained after analysis.

RESULTS:

The mean distance between the pupil center and the corneal vertex in mesopic and photopic conditions of illumination in myopic eyes was 0.27 ± 0.14 (range: 0.02 to 0.70 mm) and 0.24 ± 0.12 mm (range: 0.06 to 0.65 mm), respectively, whereas it was 0.36 ± 0.15 (range: 0.03 to 0.70 mm) and 0.31 ± 0.16 mm (range: 0.03 to 0.77 mm) in hyperopic eyes, respectively. The mean spatial pupil center shift was significant: 0.11 ± 0.07 mm (range: 0.02 to 0.57 mm) in myopic eyes and 0.12 ± 0.09 mm (range: 0.02 to 0.47 mm) in hyperopic eyes. The pupil center shifted consistently temporally as the pupil dilated. The pupil center shift was not significantly related to sex, age, eye (right or left), or refractive error.

CONCLUSIONS:

The mean distance between the pupil center and the corneal vertex is greater in hyperopic eyes than in myopic eyes, whereas the spatial shift of this pupil center has a temporal direction as the pupil dilates and is constantly small in all groups. However, pupil center shift can be important in a few patients.

[J Refract Surg. 2014;30(10):694–700.]

From the Department of Anterior Segment and Refractive Surgery, Foundation Rothschild, and Center of Expertise and Research in Optics for Clinicians, Paris, France.

Dr. Gatinel is a consultant for Alcon Laboratories, Inc. (Fort Worth, TX). The remaining authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (DG); data collection (ISM); analysis and interpretation of data (ISM, AS, EG, DG); drafting of the manuscript (ISM, DG); critical revision of the manuscript (AS, EG); statistical expertise (DG); supervision (DG)

Correspondence: Damien Gatinel, MD, Fondation Adolphe de Rothschild, 25-29 Rue Manin, 75019 Paris, France. E-mail: gatinel@gmail.com

Received: April 17, 2014
Accepted: June 02, 2014

Abstract

PURPOSE:

To evaluate the effectiveness of the pupil center shift with changes in the state of pupil size and with other ocular variables.

METHODS:

Dynamic pupillometry with the Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX) was performed in 248 eyes of 124 patients scheduled for corneal laser refractive surgery. High-resolution images were obtained using the infrared-sensitive camera (incorporated in the videokeratoscope) under mesopic and photopic conditions. Measurements of pupil diameters, distance between the pupil center and keratoscopic axis, and spatial shift of the pupil center were obtained after analysis.

RESULTS:

The mean distance between the pupil center and the corneal vertex in mesopic and photopic conditions of illumination in myopic eyes was 0.27 ± 0.14 (range: 0.02 to 0.70 mm) and 0.24 ± 0.12 mm (range: 0.06 to 0.65 mm), respectively, whereas it was 0.36 ± 0.15 (range: 0.03 to 0.70 mm) and 0.31 ± 0.16 mm (range: 0.03 to 0.77 mm) in hyperopic eyes, respectively. The mean spatial pupil center shift was significant: 0.11 ± 0.07 mm (range: 0.02 to 0.57 mm) in myopic eyes and 0.12 ± 0.09 mm (range: 0.02 to 0.47 mm) in hyperopic eyes. The pupil center shifted consistently temporally as the pupil dilated. The pupil center shift was not significantly related to sex, age, eye (right or left), or refractive error.

CONCLUSIONS:

The mean distance between the pupil center and the corneal vertex is greater in hyperopic eyes than in myopic eyes, whereas the spatial shift of this pupil center has a temporal direction as the pupil dilates and is constantly small in all groups. However, pupil center shift can be important in a few patients.

[J Refract Surg. 2014;30(10):694–700.]

From the Department of Anterior Segment and Refractive Surgery, Foundation Rothschild, and Center of Expertise and Research in Optics for Clinicians, Paris, France.

Dr. Gatinel is a consultant for Alcon Laboratories, Inc. (Fort Worth, TX). The remaining authors have no financial or proprietary interest in the materials presented herein.

AUTHOR CONTRIBUTIONS

Study concept and design (DG); data collection (ISM); analysis and interpretation of data (ISM, AS, EG, DG); drafting of the manuscript (ISM, DG); critical revision of the manuscript (AS, EG); statistical expertise (DG); supervision (DG)

Correspondence: Damien Gatinel, MD, Fondation Adolphe de Rothschild, 25-29 Rue Manin, 75019 Paris, France. E-mail: gatinel@gmail.com

Received: April 17, 2014
Accepted: June 02, 2014

The entrance pupil of the human eye is formed by the image of the aperture stop of the iris through the cornea.1,2 The human eye is an optical system affected by variable amounts of regular and irregular aberrations,3,4 which is affected greatly when the pupil dilates,5,6 influencing the quality of the retinal image.7

The role of the size and location of the pupil with respect to the centration strategy of refractive surgery treatment receives increasing attention.8–10 Pupil tracking in refractive surgery relies on the assumption that the pupil center location does not shift during pupil movements.11,12 Indeed, if the corneal ablation is well centered when the pupil is small and off center when the pupil dilates, the patient can experience light halos, complain of glare in low-light conditions, and present a decrease in visual acuity and contrast sensitivity.13 Precise centration and positioning is also important in cataract surgery, especially with regard to the aspheric and multifocal intraocular lenses.14,15

The purpose of this study was to evaluate whether there is a systematic variation of the position of the pupil center when the diameter of the pupil varies in relation to various parameters (eg, age, sex, and refractive error). We used an infrared dynamic pupillometry device (Topolyzer Vario; Alcon Laboratories, Inc., Fort Worth, TX) in mesopic and photopic conditions to record the distance between the corneal vertex (first Purkinje image) and the pupil center.

Patients and Methods

Patients

This study included 248 eyes of 124 patients presenting for refractive surgery from February to May 2013 at Foundation Rothschild, Paris, France. All patients received a complete ocular assessment prior to surgery, including cycloplegic refraction and slit-lamp and fundus examinations.

All patients with a history of ocular surgery, corneal diseases, or other ocular pathologies (ie, amblyopia, glaucoma, cataract, retinopathy, and strabismus), and suspected keratoconus on corneal topography were excluded. We included patients older than 17 years with healthy eyes. The study and data accumulation were achieved with approval from the Rothschild Foundation Institutional Review Board. Informed consent was obtained from all patients and the study adhered to the tenets of the Declaration of Helsinki.

Instrument and Measurement Procedure

Pupillometry of each eye was performed using the dynamic pupil measurement module (Wavelight Topolyzer Vario software, Alcon Laboratories, Inc.) incorporated in the videokeratoscope and equipped with an infrared illumination and camera device (Figure A, available in the online version of the article). The instrument measures and records the changes in pupil size during the transition from mesopic to photopic conditions. Three successive cycles were performed during 60 seconds (during each cycle, the Placido rings turn off and on successively). Red and green points were used to show the pupilc enter and the vertex, respectively (Figure B, available in the online version of the article). The distance between the pupil center and the keratometric axis (corneal vertex) in both mesopic and photopic conditions were provided.

The pupillometries were performed in a closed, dark room (1 lux illumination or lower). The patient’s head was covered with a thick black clouding cloth, lowering the lighting conditions from 1 to 0.4 lux. The acquisitions were made first with the Placido disc’s light off in low mesopic conditions (0.4 lux), then with the light on to provide photopic lighting conditions (120 lux). Illuminance values were obtained with a BM3 Topcon light meter (Topcon, Tokyo, Japan). Three consecutive acquisitions were performed (each acquisition included three cycles of mesopic and photopic conditions) for both eyes to assess the repeatability of the instrument. Both eyes were tested consecutively, starting randomly with the right or left eye. All of the measurements were performed by the same operator (ISM). All images were analyzed by computer software for data collection and data analysis. Pupil diameters, pupil center shifts, and distances between pupil centers and corneal vertex measurements were represented in Cartesian coordinates (Figure 1).

Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX) analysis software output screen and graphic representation of pupil center shift.

Figure 1.

Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX) analysis software output screen and graphic representation of pupil center shift.

Statistical Analysis

Statistical analyses were performed with SPSS version 13.0 (SPSS, Inc., Chicago, IL). We used the following statistical analysis: paired t test, unpaired t test, general linear model (analysis of covariance [ANCOVA]), and Pearson correlation analysis. A P value less than .05 was considered statistically significant. Data are presented as the mean ± standard deviation.

Results

Demographics

Patient demographics are represented in Table 1.

Demographic Data

Table 1:

Demographic Data

Pupil Diameter

The mean pupil diameters obtained on the studied population (all groups) in mesopic and photopic conditions were 5.90 ± 0.95 (range: 2.72 to 7.91 mm) and 3.06 ± 0.57 mm (range: 1.66 to 4.89 mm), respectively. There was a significant difference between the pupil diameters obtained in the two illumination conditions (paired t test, P < .0001). Figure C (available in the online version of the article) shows the negative correlation between age and pupil diameter under both conditions of illumination (mesopic conditions r = −0.575, P < .01; photopic conditions r = −0.418, P < .01).

There was no significant difference in the pupil diameter between myopic and hyperopic eyes when age was taken into account, whether in mesopic (ANCOVA, P = .580) or photopic (ANCOVA, P = .424) conditions or between highly astigmatic eyes and others (unpaired t test, t = −0.819, P = .413 in mesopic conditions, t = −0.577, P = .564 in photopic conditions). There was no significant difference in pupil diameter between right and left eyes in both illumination conditions (unpaired t test in mesopic conditions t = 0.618, P = .537 and photopic conditions t = 0.479, P = .633). We did not find a significant difference between male and female pupil diameters under photopic conditions (unpaired t test, t = −1.602, P = .111).

Magnitude of the Pupil Dilatation

The magnitude of the pupil dilatation is defined as: pupil diameter in mesopic condition – pupil diameter in photopic condition. In our sample, the mean magnitude of the pupil dilatation was 2.84 ± 0.59 mm (range: 0.65 to 4.14 mm). Figure C shows the negative correlation between age and magnitude of pupil dilatation between the two conditions of illumination (r = −0.521, P < .01).

There was no significant difference in the magnitude of the pupil dilatation between myopic and hyperopic eyes when age was taken into account (ANCOVA, P = .972) or between highly astigmatic eyes and others (unpaired t test, t = 0.749, P = .455). There was no significant difference in pupil dilatation between right and left eyes (unpaired t test, t = −0.526, P = .600). We did not find a significant difference between males and females when age was taken into account (ANCOVA, P = .827).

Pupil Center Position

The pupil center locations with respect to the corneal vertex are shown in Figure 2. The mean distance between pupil center and vertex in mesopic and photopic conditions were 0.29 ± 0.14 (range: 0.02 to 0.70 mm) and 0.26 ± 0.14 mm (range: 0.03 to 0.77 mm), respectively. There was a significant difference between the positions of the pupil centers in the two illumination conditions (paired t test, P < .0001). The pupil center was located temporally in relation to the corneal vertex for the right (94% mesopic conditions; 90% photopic conditions) and left (93% mesopic conditions; 81% photopic conditions) eyes.

Pupil center location in mesopic and photopic conditions in (A) right and (B) left eyes.

Figure 2.

Pupil center location in mesopic and photopic conditions in (A) right and (B) left eyes.

Figure D (available in the online version of the article) shows the mean distances between the pupil center and the vertex in mesopic and photopic conditions as a function of age. There was a significant positive correlation between the distance between the pupil center and the vertex and the age of patients in both mesopic (r = 0.206, P < .01) and photopic (r = 0.188, P < .01) conditions.

Table 2 shows the distances between pupil centers and vertex in different ametropic groups. There was a significant difference in the distance between the pupil center and the vertex between myopes and hyperopes when age was taken into account in mesopic (ANCOVA, P = .001) and photopic (ANCOVA, P = .017) conditions. There was no significant difference in the distance between the pupil center and the vertex between highly astigmatic eyes and others (unpaired t test, t = −1.594, P = .112 in mesopic conditions; t = −0.966, P = .335 in photopic conditions).

Distance Between the Pupil Center and the Vertex According to Ametropia

Table 2:

Distance Between the Pupil Center and the Vertex According to Ametropia

There was no significant difference in the distance between pupil center and vertex between the right and left eyes in both mesopic (unpaired t test, t = 0.618, P = .537) and photopic (unpaired t test, t = 0.479, P = .633) conditions or between men and women (unpaired t test, t = 1.571, P = .117).

The mean displacement of the pupil center between mesopic and photopic conditions was 0.11 ± 0.08 mm (range: 0.02 to 0.57 mm). There was no correlation between the length of the pupil center shift and the magnitude of the dilation of the pupil, which averaged 2.84 ± 0.59 mm (range: 0.65 to 4.14 mm) (r = −0.120). There was no significant difference in pupil center shift between men and women (unpaired t test, t = −1.126, P = .261). The pupil center moved temporally as the pupil dilated and this motion was not significantly different between the right and the left eyes (unpaired t test, t = 0.729, P = .467). There was no correlation between pupil center shift and age (r = 0.083).

Table A (available in the online version of the article) presents the results obtained for the pupil center shift in the different ametropic groups. We found no relationship between pupil center shift and refraction (no significant difference between myopes and hyperopes [unpaired t test, t = 0.152, P = .879] or between highly astigmatic eyes and others [unpaired t test, t = 0.177, P = .860]).

Discussion

To our knowledge, we have studied the pupil center location in the largest sample of eyes published to date. As in previous studies,16,17 we found significant differences in the pupil diameter values obtained in the two illumination conditions, and a negative correlation between pupil size and age. The difference in the pupil diameter values between photopic and mesopic conditions is also reduced with age. These results confirm those published by Winn et al.18 We did not find a significant correlation between pupil diameter and refractive error when age was taken into account in either lighting condition. These results are consistent with those found by Yang et al.16

Because the pupil possesses a slightly irregular elliptical geometry, its center must be determined using some geometrical assumptions.19 The corneal vertex (corneal light reflex) is the reflection of a light source by the anterior surface of the cornea and corresponds to a virtual image behind the cornea, also known as the first Purkinje–Sanson image. The distance between the pupil center and vertex is a consequence of the kappa angle, which is formed by the intersection of the visual axis with the pupillary axis. Described by Artal et al.,20 this angle is smaller in myopic than in hyperopic eyes, which implies that the distance between the pupil center and the vertex is smaller in myopic eyes in comparison to hyperopic eyes. Camellin et al.21 found a mean distance between the pupil center and the keratoscopic axis greater in hyperopic eyes (0.45 ± 0.19 mm [maximum: 0.8 mm]) than in myopic eyes (0.226 ± 0.13 mm [maximum: 0.75 mm]). When the cornea is illuminated by a light whose rays are parallel, the curvature causes the formation of an image at the focal point of the corneal diopter.22–24 Like other instruments, the Topolyzer Vario uses the vertex to reference the pupil center coordinates, whereas the pupil center serves as a landmark for referring the laser ablation and tracking the eye because current excimer lasers cannot track the target corneal zone. Theoretically, there should be no change in the position of the first Purkinje image (vertex) according to the center of the limbus in the dilation of the pupil if there is no change in the sighting direction with respect to the pupillometer optical axis. Yang et al.16 showed that the vertex position referred from the center of the cornea was substantially identical in mesopic and photopic conditions.

It has been debated whether to use the entrance pupil center or the corneal vertex as the ideal reference for ablation centration.25–27 Using a modified autokeratometer to photograph the corneas of 50 patients, Pande and Hillman28 concluded that the coaxially sighted corneal light reflex (vertex) was the closest to the corneal intercept of the visual axis. They proposed the use of the vertex for centration instead of the entrance pupil.

Some studies consider that the pupil center is a good anatomical landmark for centering customized refractive surgery treatments (rather than the line of sight) because its movement is relatively small between the different illumination conditions.9,17,29,30 Other studies have shown that even though it was small, the systematic displacement of the center of the pupil was sufficient to degrade the optical quality of the eye.17 According to Tabernero et al.,17 a pupil center shift of 0.07 mm is sufficient to degrade the visual quality of an eye with a pupil mydriasis (7 mm). The pupil center shift degrading the visual quality of a pupil of 3 mm (in photopic conditions) is 0.2 mm. In our sample, 26% of the eyes described a movement less than 0.07 (66 eyes of 248, including 5 presbyopic myopes and 15 presbyopic hyperopes [older than 40 years], 42 non-presbyopic myopes, and 2 non-presbyopic hyperopes). Ninety-two percent of our eyes presented a pupil center shift less than 0.20 mm (21 eyes of 248 presented a movement greater than 0.2 mm). Thus, we concluded that the quality of vision can be affected in 8% of cases in photopic conditions and in 75% of cases in mesopic conditions. In addition, previous studies have recommended a treatment centered on the corneal vertex, which is a stable landmark and may be closer to the visual axis.8,31,32 Methods for centering ablation profiles considering pupil center and corneal vertex information simultaneously have also been proposed.

Our results suggest that the surgeon should adjust the laser illumination system intensity until the pupil diameter value would be close to the pupil diameter measured at the time of wavefront acquisition, and that constant lighting intensity should be maintained throughout the excimer laser deliverance.

Our results confirm that regardless of the preferred centration strategy, using the photopic pupil center to reference the treatment centration may incur the risk of a mismatch between the treated zone at the corneal plane and the entrance pupil in mesopic conditions because the direction of the pupil center shift is temporal during dilation.

We found that the pupil center is generally located temporally from the corneal vertex and describes a small but significant displacement of 0.11 ± 0.08 mm (range: 0.02 to 0.57 mm) when the pupil dilates. The average magnitude of the pupil center shift during dilatation was 0.07 ± 0.05 mm (range: 0.00 to 0.29 mm) horizontally and was directed temporally in 91% of 124 right eyes and in 87% of 124 left eyes. Vertical movement was, on average, 0.06 ± 0.07 mm (range: 0.00 to 0.47 mm), with no clear apparent direction (51% and 49% respectively in the upper and lower quadrant for the left eyes and 44% and 56%, respectively, in the upper and lower quadrant for the right eyes). The average absolute magnitude of the pupil center that we measured was between the values reported by Wyatt33 and Walsh,34 but was lower than those reported by Tabernero et al.17 (significant movement of 0.21 ± 0.11 mm) and Wilson et al.35 (significant movement, up to 0.6 mm). Although we found few eyes presented an important movement of the pupil center between photopic and mesopic conditions, individual differences may explain the differences in the values we have with Wilson et al.35 The change in the position of the pupil center during the transition from photopic to mesopic conditions was substantially similar in all patients and seems unrelated to any factor studied. We found that the distance between the pupil center and the vertex for highly astigmatic eyes was not significantly different from other groups in either lighting condition. There was a significant positive correlation between the pupil center–vertex distance and age of patients in both conditions of illumination. We cannot conclude whether age may play a role in increasing the distance between the pupil center and the vertex because this result could be explained by the fact that, in our study, presbyopic (older) eyes were mostly hyperopic.

We found that the pupil center described a small but significant shift between the two illumination conditions.

References

  1. Atchison D, Smith G. Optics of the Human Eye. Edinburgh: Elsevier Science; 2002.
  2. Lowenfeld IE. The Pupil: Anatomy, Physiology, and Clinical Applications. Ames, IA: Iowa State University Press; 1993.
  3. Ivanoff A. About the spherical aberration of the eye. J Opt Soc Am. 1956;46:901–903. doi:10.1364/JOSA.46.0901_1 [CrossRef]
  4. Jenkins TCA. Aberrations of the eye and their effects on vision. Br J Physiol Opt. 1963;20:59–91.
  5. Walsh G, Charman WN. The effect of pupil centration and diameter on ocular performance. Vision Res. 1988;28:659–665. doi:10.1016/0042-6989(88)90114-9 [CrossRef]
  6. Martínez CE, Applegate RA, Klyce SD, McDonald MB, Medina JP, Howland HC. Effect of pupillary dilation on corneal optical aberrations after photorefractive keratectomy. Arch Ophthalmol. 1998;116:1053–1062. doi:10.1001/archopht.116.8.1053 [CrossRef]
  7. Artal P, Navarro R. Monochromatic modulation transfer function of the human eye for different pupil diameters: an analytical expression. J Opt Soc Am A Opt Image Sci Vis. 1994;11:246–249. doi:10.1364/JOSAA.11.000246 [CrossRef]
  8. Arbelaez MC, Vidal C, Arba-Mosquera S. Clinical outcomes of corneal vertex versus central pupil references with aberration-free ablation strategies and LASIK. Invest Ophthalmol Vis Sci. 2008;49:5287–5294. doi:10.1167/iovs.08-2176 [CrossRef]
  9. Kermani O, Oberheide U, Schmiedt K, Gerten G, Bains HS. Outcomes of hyperopic LASIK with the NIDEK NAVEX platform centered on the visual axis or line of sight. J Refract Surg. 2009;25:S98–S103.
  10. Park CY, Oh SY, Chuck RS. Measurement of angle kappa and centration in refractive surgery. Curr Opin Ophthalmol. 2012;23:269–275. doi:10.1097/ICU.0b013e3283543c41 [CrossRef]
  11. Gobbi PG, Carones F, Brancato R, et al. Automatic eye tracker for excimer laser photorefractive keratectomy. J Refract Surg. 1995;11:S337–S342.
  12. Bueeler M, Mrochen M. Limitations of pupil tracking in refractive surgery: systematic error in determination of corneal locations. J Refract Surg. 2004;20:371–378.
  13. Fay AM, Trokel SL, Myers JA. Pupil diameter and the principal ray. J Cataract Refract Surg. 1992;18:348–351. doi:10.1016/S0886-3350(13)80069-7 [CrossRef]
  14. Atchison DA. Design of aspheric intraocular lenses. Ophthalmic Physiol Opt. 1991;11:137–146. doi:10.1111/j.1475-1313.1991.tb00213.x [CrossRef]
  15. Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby NE. A new intraocular lens design to reduce spherical aberration of pseudophakic eyes. J Refract Surg. 2002;18:683–692.
  16. Yang Y, Thompson K, Burns SA. Pupil location under medopic, photopic and pharmacologically dilated conditions. Invest Ophthalmol Vis Sci. 2002;43:2508–2512.
  17. Tabernero J, Atchison DA, Markwell EL. Aberrations and pupil location under corneal topography and Hartmann-Shack illumination conditions. Invest Ophthalmol Vis Sci. 2009;50:1964–1970. doi:10.1167/iovs.08-2111 [CrossRef]
  18. Winn B, Whitaker D, Elliott DB, Phillips NJ. Factors affecting light-adapted pupil size in normal human subjects. Invest Ophthalmol Vis Sci. 1994;35:1132–1137.
  19. Fedtke C, Manns F, Ho A. The entrance pupil of the human eye: a three dimensional model as a function of viewing angle. Opt Soc Am. 2010;18:21.
  20. Artal P, Benito A, Tabernero J. The human eye is an example of robust optical design. J Vision. 2006;6:1–7. doi:10.1167/6.1.1 [CrossRef]
  21. Camellin M, Gambino F, Casaro S. Measurement of the spatial shift of the pupil center. J Cataract Refract Surg. 2005;31:1719–1721. doi:10.1016/j.jcrs.2005.04.027 [CrossRef]
  22. Barry JC, Branmann K, Dunne MC. Catoptric properties of eyes with misaligned surfaces studied by exact ray tracing. Invest Ophtalmol Vis Sci. 1997;38:1476–1484.
  23. Barry JC, Pongs UM, Hillen W. Algorithm for Purkinje images I and IV and limbus centre localization. Comput Biol Med. 1997;27:515–531. doi:10.1016/S0010-4825(97)00023-1 [CrossRef]
  24. Cornsweet TN, Crane HD. Accurate two dimensional eye tracker using first and fourth Purkinje images. J Opt Soc Am A. 1973;63:921–928. doi:10.1364/JOSA.63.000921 [CrossRef]
  25. Applegate RA, Thibos LN, Twa MD, Sarver EJ. Importance of fixation, pupil center, and reference axis in ocular wavefront sensing, videokeratography, and retinal image quality. J Cataract Refract Surg. 2009;35:139–152. doi:10.1016/j.jcrs.2008.09.014 [CrossRef]
  26. Salz JJ, Stevens CALADARVision LASIK Hyperopia Study Group. LASIK correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision excimer laser system. Ophthalmology. 2002;109:1647–1656. doi:10.1016/S0161-6420(02)01133-8 [CrossRef]
  27. Schwiegerling JT. Eye axes and their relevance to alignment of corneal refractive procedures. J Refract Surg. 2013;29:515–516. doi:10.3928/1081597X-20130719-01 [CrossRef]
  28. Pande M, Hillman JS. Optical zone centration in keratorefractive surgery. Entrance pupil center, visual axis, coaxially sighted corneal reflex, or geometric corneal center?Ophthalmology. 1993;100:1230–1237. doi:10.1016/S0161-6420(93)31500-9 [CrossRef]
  29. Applegate RA, Thibos LN, Bradley A, et al. Reference axis selection: subcommittee report of the OSA working group to establish standards for measurement and reporting of optical aberrations of the eye. J Refract Surg. 2000;16:S656–S658.
  30. Reinstein DZ, Cremonesi E. Should LASIK sphero-cylindrcal treatments be centred on the pupil? Presented at the International Society of Refractive Surgery Annual Meeting. . November 15–18, 2002. ; Orlando, FL. .
  31. Okamoto S, Kimura K, Funakura M, Ikeda N, Hiramatsu H, Bains HS. Comparison of avefront guided aspheric laser in situ keratomilesis for myopia: coaxially sighted corneal-ligh-reflex versus line-of-sight centration. J Cataract Refract Surg. 2011;37:1951–1960. doi:10.1016/j.jcrs.2011.05.040 [CrossRef]
  32. Reinstein DZ, Gobbe M, Archer TJ. Coaxially sighted corneal light reflex versus entrance pupil center centration of hyperopic corneal ablations in eyes with small and large angle kappa. J Refract Surg. 2013;29:518–525. doi:10.3928/1081597X-20130719-08 [CrossRef]
  33. Wyatt HJ. The form of the human pupil. Vision Res. 1995;35:2021–2036. doi:10.1016/0042-6989(94)00268-Q [CrossRef]
  34. Walsh G. The effect of mydriasis on the pupillary centration of the human eye. Ophthalmic Physiol Opt. 1988;8:178–182. doi:10.1111/j.1475-1313.1988.tb01034.x [CrossRef]
  35. Wilson MA, Campbell MC, Simonet P. Change of pupil centration with change of illumination and pupil size. Optom Vis Sci. 1992;69:129–136. doi:10.1097/00006324-199202000-00006 [CrossRef]
Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX). Dynamic pupillometer included in the Placido discs topographer. Two sets of infrared light-emitting diodes are circled in red.

Figure A. Topolyzer Vario (Alcon Laboratories, Inc., Fort Worth, TX). Dynamic pupillometer included in the Placido discs topographer. Two sets of infrared light-emitting diodes are circled in red.

Image of the dynamic pupillometer showing the pupil center (in red) and the corneal vertex (in green).

Figure B. Image of the dynamic pupillometer showing the pupil center (in red) and the corneal vertex (in green).

(A) Pupil diameter (mm) as a function of age (years) in (A) mesopic and (B) photopic conditions. (C) Magnitude of pupil dilatation (mm) as a function of age (years).

Figure C. (A) Pupil diameter (mm) as a function of age (years) in (A) mesopic and (B) photopic conditions. (C) Magnitude of pupil dilatation (mm) as a function of age (years).

Distance between pupil center and vertex (mm) as a function of age in (A) mesopic and (B) photopic conditions.

Figure D. Distance between pupil center and vertex (mm) as a function of age in (A) mesopic and (B) photopic conditions.

Table A: Pupil Center Shift According to Ametropia

Demographic Data

Parameter Total Myopes Hyperopes Weak Astigmatism (Cylinder < 0.75 D) Strong Astigmatism (Cylinder > 1.50 D)
No. of patients 124 93 34 49 26
No. of eyes 248 183 64 59 (44 myopes/15 hyperopes) 35 (29 myopes/6 hyperopes)
Right eye/left eye 124/124 93/90 32/32 26/33 19/16
Age (y)
  Mean ± SD 36.9 ± 12.4 32.5 ± 8.1 49.2 ± 14.3 36.7 ± 11.9 34.1 ± 8.3
  Minimum/maximum 20.5/70.6 20.5/56.3 22.1/70.6 20.5/69.8 23.5/54.3
Male/female (%) 36/64 39/61 32/68 37/63 54/46
Mean refractive sphere (D)
  Mean ± SD −3.6 ± 2.0 2.7 ± 1.4
  Minimum/maximum −9.5 ± −0.3 0.0/6.0
Average cylinder (D)
  Mean ± SD −0.8 ± 0.8 −0.6 ± 0.8
  Minimum/maximum −4.5/0.0 −4.3/0.0
Mean refractive SEQ (D)
  Mean ± SD −4.0 ± 2.0 2.4 ± 1.5
  Minimum/maximum −11.3/−0.5 −1.1/5.3

Distance Between the Pupil Center and the Vertex According to Ametropia

Parameter Total Myopes Hyperopes Weak Astigmatism (Cylinder < 0.75 D) Strong Astigmatism (Cylinder > 1.50 D)
No. of patients 124 93 34 49 26
No. of eyes 248 183 64 59 (44 myopes/15 hyperopes) 35 (29 myopes/6 hyperopes)
Right eye/left eye 124/124 93/90 32/32 26/33 19/16
Distance pupil center – vertex in mesopic condition (mm)
  Mean ± SD 0.29 ± 0.14 0.27 ± 0.14 0.36 ± 0.15 0.28 ± 0.15 0.33 ± 0.15
  Minimum/maximum 0.02/0.70 0.02/0.70 0.03/0.70 0.02/0.59 0.09/0.70
Distance pupil center – vertex in photopic condition (mm)
  Mean ± SD 0.26 ± 0.14 0.24 ± 0.12 0.31 ± 0.16 0.25 ± 0.14 0.28 ± 0.14
  Minimum/maximum 0.03/0.77 0.06/0.65 0.03/0.77 0.03/0.77 0.10/0.65

10.3928/1081597X-20140903-07

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