Optometry - Journal of the American Optometric Association
Volume 81, Issue 8 , Pages 408-413, August 2010

Ocular pulse amplitude and associated glaucomatous risk factors in a healthy Hispanic population

Pacific University College of Optometry, Forest Grove, Oregon

Article Outline

Abstract 

Background

With increasing evidence that vascular risk factors play a role in the development of glaucoma, it is critical to be familiar with factors related to intraocular blood flow, such as the ocular pulse amplitude (OPA). This study evaluates OPA and factors related to it in a healthy, Hispanic population.

Methods

Refractive error, corneal curvature, Goldmann applanation tonometry (GAT), dynamic contour tonometry (DCT), OPA, axial length, and central corneal thickness (CCT) measurements were obtained on 104 Hispanic subjects recruited from the community.

Results

OPA ranged from 0.7 to 4.7 mmHg (mean, 2.1 ± 0.8 mmHg) and showed a significant correlation with refractive error, axial length, GAT, and DCT (r=0.250, -0.358, 0.460, 0.378; P=0.011, <0.001, <0.001, and <0.001, respectively). Mean intraocular pressure with GAT was 15.6 mmHg. Mean CCT was 541.2 μm. The average refractive error was 0.75 diopters (D) of myopia, with 25% having >1.00 D myopia.

Conclusion

Normal OPA values have not been studied in Hispanic populations. OPA is thought to provide information regarding ocular blood flow; however, more studies are needed to determine its significance in glaucoma treatment.

Keywords: Hispanic population, Goldmann applanation tonometry, Dynamic contour tonometry, Ocular pulse amplitude, Central corneal thickness, Glaucoma

 

Glaucoma is the most common optic neuropathy. Elevated intraocular pressure (IOP) is a major risk factor in the development of glaucoma1, 2, 3, 4; however, it is not present in every type of glaucoma, and it does not necessarily cause the condition.5, 6 The mechanism that causes optic nerve damage is unknown. In addition to IOP, other risk factors play an important role in the development and progression of glaucoma. These include reduced central corneal thickness,2, 3 age,1, 2, 3, 4 race,3, 4, 7 myopia,8, 9 and genetics.3, 4, 10, 11

There is increasing evidence that vascular risk factors play a role in the development of glaucoma. The vascular theory hypothesizes that glaucomatous damage occurs, at least in part, because of inadequate perfusion of the optic nerve. Lower diastolic perfusion pressure (the diastolic blood pressure minus the IOP),1, 2, 3, 4, 6, 12, 13, 14 low systolic blood and perfusion pressure,2, 3 and cardiovascular disease2 have been found to predict glaucoma progression, supporting the vascular theory of glaucomatous damage. In addition, patients with normal-tension glaucoma (NTG) and open-angle glaucoma (OAG) have been found to have reduced ocular perfusion compared with nonglaucomatous patients.15, 16 In comparison, ocular hypertensive patients have increased choroidal perfusion compared with OAG17, 18, 19, 20 and NTG19, 20 patients, which may act as a protective mechanism.

IOP increases with the systolic and decreases with the diastolic pressure of the heart pumping blood into the choroidal vessels. The difference between the systolic and diastolic IOP is the ocular pulse amplitude (OPA). The OPA is thought to provide information about intraocular blood flow and may indirectly measure choroidal perfusion.21, 22 Although little is known about the relationship between OPA and glaucoma, OPA has been shown to be lower in patients with OAG and NTG compared with those with ocular hypertension and control subjects.17, 18, 23, 24, 25 Schwenn et al.26 found OPA to be an independent risk factor for NTG. In addition, Vulsteke et al.27 found a significant correlation between low OPA and visual field loss, and Weizer et al.28 determined that increased OPA correlated with less severe glaucoma.

A literature review found no studies that evaluated the OPA in a Hispanic population. This study was designed to evaluate the OPA as well as other factors associated with glaucoma, such as refractive error, axial length, IOP, central corneal thickness (CCT), and corneal curvature in a healthy, Hispanic population.

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Methods 

Data were obtained from 220 eyes of 110 Hispanic subjects. Eligible Hispanics in Washington County, Oregon, were invited to attend a Pacific University Eye Clinic. Subjects were recruited by posting informational flyers throughout the community. The Institutional Review Board at Pacific University approved this study, and written informed consent was obtained from all participants. Individuals were screened before the study for the presence of abnormalities that might compromise the results of the study. Those with a history of glaucoma, ocular inflammation, trauma, or procedures that affect corneal thickness were excluded from the study. Pregnant women, patients with sensitivity to anesthetic, and those under the age of 18 years were also excluded from the study.

All procedures were performed by one trained examiner. Automated keratometry and refractive error measurements were obtained using a Canon TX-F Auto Refractor/Auto Keratometer (Lake Success, New York). An anterior segment evaluation was then performed followed by insertion of a drop of sodium fluorescein 0.25% and benoxinate 0.4% (Flurox; OCuSOFT, Richmond, Texas) in each eye. Two Goldmann applanation tonometry (GAT) measurements were obtained using a calibrated Goldmann tonometer and slit lamp (Haag-Streit, Switzerland). Three IOP and OPA readings in each eye were acquired using the Pascal Dynamic Contour Tonometer (DCT; Swiss Microtechnology, Port, Switzerland). After IOP measurements, the examiner performed 2 axial length measurements in each eye with the DGH 5100 A-scan/Pachymeter (DGH Technology Inc., Exton, Pennsylvania) and 6 pachymetry readings in each eye with the Tomey Handy Pachymeter (SP-100; Tomey Corporation, Phoenix, Arizona).

The examiner was not blinded to GAT results. However, to avoid examiner bias, GAT was performed before DCT, OPA, axial length, and pachymeter measurements, which all produce digital readings. Schneider and Grehn29 found no significant difference in GAT readings when repeating the Goldmann procedure after initial GAT and DCT measurements. Similarly, when performing DCT and GAT in random order, Pache et al.30 found that order had no influence on IOP results.

The GAT was set to 10 mmHg before each reading. Two GAT readings were obtained for each eye. If the readings were more than 2 mmHg apart, a third measurement was taken, and the average of the 2 closest readings was used for analysis.

The Pascal DCT is a slit lamp–mounted contact tonometer (see Figure 1) that monitors IOP and OPA simultaneously and continuously. The tonometer tip has a surface contour that is similar to that of the cornea and an embedded pressure sensor, allowing IOP and OPA measurements that are less dependent on corneal properties than GAT.31, 32, 33, 34 At the end of each measurement, the IOP, OPA, and quality score are displayed on a digital monitor. The quality of the DCT reading is graded from 1 to 5. A score of 1 is optimal. Scores of 2 and 3 are acceptable, and scores of 4 and 5 are unacceptable. Three DCT readings with a quality score of 3 or better were obtained. According to manufacturer guidelines, a new protective cover was used on the DCT probe for each patient. The probe was left on the cornea for 8 to 10 seconds to allow for an accurate IOP and OPA measurement. A digital printout, including the IOP, OPA, and quality score was collected for each subject, and the 2 readings with the best quality score were averaged for use in statistical analysis. If all 3 quality scores were the same, all IOP and OPA scores were averaged for statistical use.

Two axial length measurements with a standard deviation <0.15 mm were averaged for statistical analysis. Corneal thickness was measured by placing the ultrasound probe on the center of the cornea. The mean of 6 pachymetry readings was used for statistical analysis.

Statistical analysis was performed using SPSS, version 15.0 (SPSS Inc., Chicago, Illinois). Descriptive statistics, including mean, standard deviation, and percentages, were used to summarize the demographic and vision characteristics of the subjects. Paired t tests were used to compare DCT and GAT. Associations between variables were examined using the Pearson coefficient and P value. A P value <0.05 was considered statistically significant.

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Results 

Data were collected on 220 eyes of 110 Hispanic participants. One subject chose to stop testing in the middle of the examination, one could not keep his eyes open for the testing, and we were unable to obtain quality DCT values on 4 subjects.

Complete data from 208 eyes of 104 Hispanic subjects were used for analysis. The mean age was 36.2 ± 13.5 years (age range, 18 to 78 years). Sex distribution was 55 women and 49 men. The majority (93%) reported Mexican heritage. Others were from Columbia (1%), Costa Rica (1%), Guatemala (1%), Peru (1%), Puerto Rico (1%), and the United States (2%). Table 1 shows the mean, median, standard deviation, and range of the evaluated parameters for each eye.

Table 1. Descriptive statistics for the right and left eyes
MeanMedianSDMinimumMaximum
Right eye
Flat keratometry (D)42.9942.991.5038.8847.00
Steep keratometry (D)44.2644.181.5241.1148.28
Corneal astigmatism (D)1.261.050.980.116.62
Spherical equivalent (D)-0.75-0.252.57-19.626.12
GAT (mmHg)15.6015.002.9410.0024.00
DCT (mmHg)14.7214.572.1211.3021.80
OPA (mmHg)2.121.920.850.734.70
DCT quality score1.942.000.611.003.00
Axial length (mm)23.7623.671.0220.9527.40
Pachymetry (μm)541.21540.0034.52460.00647.00
Left eye
Flat keratometry (D)43.0642.941.4938.7046.68
Steep keratometry (D)44.1544.001.4640.8147.47
Corneal astigmatism (D)1.090.770.990.066.57
Spherical equivalent (D)-0.470.001.71-6.505.50
GAT (mmHg)15.3615.002.8210.0023.00
DCT (mmHg)14.6914.562.0510.1320.37
OPA (mmHg)2.121.930.820.974.73
DCT quality score1.922.000.631.003.00
Axial length (mm)23.6823.550.9920.7626.56
Pachymetry (μm)542.47539.5034.48463.00650.00

Table 2 shows the correlation coefficients and statistical significance for the measured values. DCT readings were, on average, 0.9 mmHg lower than GAT measurements in the right eye and 0.7 mmHg lower than GAT in the left eye. The 2 devices correlated significantly with each other in the right (r = 0.689, P < 0.0001) and left (r = 0.705, P < 0.0001) eyes. GAT findings showed a significant correlation with CCT in the right (r = 0.334, P < 0.001) and left (r = 0.387, P < 0.001) eyes. DCT did not show a significant correlation with CCT in either the right (r = -0.034, P = 0.730) or left (r = 0.133, P = 0.177) eyes. Neither GAT nor DCT were significantly influenced by corneal curvature or refractive error.

Table 2. Correlation coefficients for the evaluated variables.
Flat K readingCorneal astigmatismSpherical equivalentGATDCTOPAAxial lengthPachymetry
Flat keratometry (D)1-0.368†0.0100.0740.1160.159-0.511†-0.130
Significance 0.0000.9220.4600.2440.1090.0000.189
Corneal astigmatism (D)-0.313†1-0.187-0.0870.052-0.0850.1860.078
Significance0.001 0.0590.3830.5990.3930.0600.436
Spherical equivalent (D)-0.044-0.230∗10.064-0.0690.300†-0.695†0.089
Significance0.6570.019 0.5190.4840.0020.0000.370
GAT (mmHg)0.14-0.132-0.11410.705†0.392†-0.1400.387†
Significance0.1590.1820.251 0.0000.0000.1560.000
DCT (mmHg)0.18-0.018-0.0660.689†10.328†-0.0410.133
Significance0.0680.8560.5050 0.0010.6810.177
OPA (mmHg)0.192-0.1930.250∗0.460†0.378†1-0.331†-0.004
Significance0.0520.0510.01100 .0010.965
Axial length (mm)-0.449†0.148-0.688†-0.062-0.014-0.358†1-0.084
Significance<0.0010.137<0.0010.5310.891<0.001 0.398
Pachymetry (μm)-0.1090.076-0.1040.334†0.034-0.0510.0591
Significance0.2710.4440.2940.0010.730.610.55

Note. Nonboldface numbers correspond to the right eye, and boldface numbers correspond to the left eye.

∗Correlations significant at the 0.05 level.

†Correlations significant at the 0.01 level.

The OPA ranged from 0.7 to 4.7 mmHg (mean, 2.1 ± 0.8 mmHg) for the right eyes. The mean of the left eyes was the same (mean, 2.1 ± 0.8 mmHg), and the range was 1.0 to 4.7 mmHg. The OPA showed a significant correlation with refractive error, axial length, GAT, and DCT in right eyes (r = 0.250, -0.358, 0.460, 0.378; P = 0.011, < 0.001, < 0.001, and < 0.001, respectively) and left eyes (r = 0.300, -0.331, 0.392, 0.328; P = 0.002, = 0.001, < 0.001, and = 0.001, respectively). Neither CCT nor age had a statistically significant correlation with OPA (r = -0.051, 0.159; P = 0.61 and 0.108, respectively).

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Discussion 

The Hispanic community is the fastest growing segment of the U.S. population.35 Studies have found that Hispanics are more susceptible to glaucomatous damage than whites.5, 6, 7 Risk factors that help to identify disease in a population facilitate earlier disease detection and aid in selecting the most appropriate therapy. It is important to be familiar with ocular characteristics that may put Hispanic patients at risk for glaucoma, including IOP, CCT, refractive error, and OPA.

The OPA represents the pulsatile passage of blood into the eye and is thought to indirectly measure choroidal perfusion.21, 22, 36 A reduction in blood flow may cause hypoxia and cell death, resulting in diseases like glaucoma. The mean OPA in our study was 2.12 mmHg. Other studies have found an average OPA of 2.09 to 2.8 mmHg in healthy, young subjects,24, 31, 36, 37, 38, 39 but no studies have evaluated OPA specifically in Hispanic patients or other races. Carbonaro et al.,40 who determined that OPA is strongly influenced by genetics, found the highest mean OPA of 2.88 mmHg in 264 white twins (92.5% female, mean age 54 years).

In addition to glaucoma, a familiarity with normal OPA measurements may help to recognize systemic vascular disease, vascular stenosis, or arteriovenous fistulas.41, 42 In a vascular clinic, Perkins42 found that 81% of those with low OPA (<1.5 mmHg for hyperopes or emmetropes and <1.0 mmHg for myopes) or a difference in OPA between the 2 eyes of >0.5 mmHg had evidence of internal carotid artery stenosis on angiography. This study also noted that all patients with 75% to 100% occlusion received the correct diagnosis with the use of OPA. Only 4 subjects in our study had an OPA <1.0 mmHg. These were all myopic patients >1.00 D. There was no difference in the mean OPA between the 2 eyes in this healthy Hispanic population.

There was no correlation between OPA and CCT in this study (r=-0.051, P=0.610). Kaufmann et al.41 found a nonsignificant trend toward higher OPA with thinner corneas. Punjabi et al.19 showed a significant negative association between OPA and CCT. It was speculated that this may be because of thinner corneas potentially having more elasticity. Stalmans et al.25 found no influence of CCT on OPA. We did not find a significant correlation between age and OPA. A similar result was found in other studies.26, 36

OPA correlated significantly with the refractive error, axial length, and IOP in this Hispanic population. These relationships have been reported previously in other populations.18, 31, 39, 40, 41, 43 The OPA is lower in patients with a longer axial length. This is thought to occur because the amount of blood entering a relatively larger eye will result in a smaller change in total volume than if the same amount of blood entered a smaller, shorter eye.41 Additionally, the sclera of myopic eyes may be inherently less rigid because of scleral thinning.44 The correlation between OPA and IOP may be caused by the elastic properties of the eye.45 If the IOP is high, the tension on the sclera increases. An increase in ocular volume will then cause an increase in pressure rather than expansion of the already stretched globe.41

Intraocular pressure varies with different ethnicities. The average IOP in this nonglaucomatous, Hispanic population was 15.6 mmHg with GAT. This is the same as the mean IOP found in another group of healthy Hispanics (15.6 mm Hg).6 However, this is slightly higher than that found in Dutch (14.6 mmHg),46 Mongolian (12.7 mmHg),47 and white (14.9 to 15.3 mmHg)31, 48 populations. Francis et al.49 obtained an average IOP of 14.4 mmHg in a population of 2,157 Hispanics. However, only those with a history of intraocular surgery were excluded from their study. The values from the current study do not include patients with known or treated glaucoma or those with other ocular conditions that may affect corneal thickness.

In our study GAT readings were, on average, 0.88 mmHg higher than DCT in the right eye and 0.67 mmHg higher than DCT in the left eye. Other studies report GAT being 0.04 to 3.9 mmHg lower than DCT.18, 31, 49, 50, 51, 52 This variation may be because of the difference between GAT and DCT being dependent on the mean and standard deviation of the CCT in each individual study. Alternatively, despite other studies reporting that the order of GAT and DCT to have no impact,29, 30 it is possible that performing GAT before DCT may have lowered the IOP taken with DCT. Also, many of the patients had never had IOP measurements taken before the study. It is possible that patient anxiety while performing GAT caused an increase in IOP. The anxiety may have decreased by the time DCT was performed.

The average CCT in these Hispanic patients was 541 μm. This compares with a mean CCT of 495 to 514 μm in Mongolians,47 534 μm in black Americans,52, 53 537 μm in Europeans,46 and 553 to 556 μm in white Americans.31, 53 Francis et al.49 found a CCT of 550 μm in a Latino population in the Los Angeles area.

Myopic patients are more likely to have glaucoma than nonmyopic patients,8, 9 and increased axial length has been shown to be associated with worsening of the visual field with glaucoma.54 The average refractive error in the current study was 0.75 diopters (D) of myopia, and 25.0% (n = 26) had myopia >1.00 D. Wong et al.9 reported that 23.9% of whites in the United States between 43 and 86 years of age had myopia. Kempen et al.55 found a myopia prevalence of 25.4% in all races of U.S. people over the age of 40 years. Other studies have estimated the prevalence of myopia >1.00 D in Latinos over the age of 40 years to be 16.8%.56 Because hyperopia increases with age,55 the higher prevalence of myopia in the current study is likely caused by the inclusion of younger subjects (18 years or older). When including only subjects 40 years or older (n = 34), 20.6% of the participants in our study had a spherical equivalent >1.00 D of myopia.

A deficit in our study is the lack of blood pressure assessment. The risk of developing glaucomatous damage more than triples when the diastolic perfusion pressure is less than 55 mmHg.1, 2, 12 Additionally, patients with perfusion pressure lower than 50 mmHg have a 4 times greater risk of OAG development than those with perfusion pressure of at least 80 mmHg.6 However, only 23% of patients with glaucoma have ocular perfusion pressure less than 50 mmHg, indicating that this is only one risk factor. These data may warrant the evaluation of perfusion pressure and other vascular risk factors when monitoring OAG. Additionally, a larger sample size would further refine the normative values obtained in this study.

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Conclusion 

Ocular blood flow to the optic nerve is an important factor in the pathogenesis of glaucoma. Our study provides new data on the association between OPA, IOP, and axial length in Hispanic patients and provides normative values for a healthy group of Hispanic patients. The OPA is higher with increasing IOP and lower with increasing myopia and axial length. With the recent re-emergence of vascular disease as an important risk factor for glaucoma, additional studies are warranted to further investigate the relationship between OPA and glaucoma.

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References 

  1. Leske MC, Wu SY, Nemesure B, et al. Incident open-angle glaucoma and blood pressure. Arch Ophthalmol. 2002;120(7):954–959
  2. Leske MC, Heijl A, Hyman L, et al. Predictors of long-term progression in the early manifest glaucoma trial. Ophthalmology. 2007;114(11):1965–1972
  3. Leske MC, Wu SY, Hennis A, et al. Risk factors for incident open-angle glaucoma: the Barbados eye studies. Ophthalmology. 2008;115(1):85–93
  4. Sommer A. Glaucoma risk factors observed in the Baltimore eye survey. Curr Opin Ophthalmol. 1996;7(2):93–98
  5. Varma R, Ying-Lai M, Francis BA, et al. Prevalence of open-angle glaucoma and ocular hypertension in Latinos: the Los Angeles Latino eye study. Ophthalmology. 2004;111(8):1439–1448
  6. Quigley HA, West SK, Rodriguez J, et al. The prevalence of glaucoma in a population-based study of Hispanic subjects: Proyecto VER. Arch Ophthalmol. 2001;119(12):1819–1826
  7. Tielsch JM, Sommer A, Katz J, et al. Racial variations in the prevalence of primary open-angle glaucoma. The Baltimore eye survey. JAMA. 1991;266(3):369–374
  8. Mitchell P, Hourihan F, Sandbach J, et al. The relationship between glaucoma and myopia: the Blue Mountains eye study. Ophthalmology. 1999;106(10):2010–2015
  9. Wong TY, Klein BE, Klein R, et al. Refractive errors, intraocular pressure, and glaucoma in a white population. Ophthalmology. 2003;110(1):211–217
  10. Tielsch JM, Katz J, Sommer A, et al. Family history and risk of primary open angle glaucoma. The Baltimore eye survey. Arch Ophthalmol. 1994;112(1):69–73
  11. Doshi V, Ying-Lai M, Azen SP, et al. Sociodemographic, family history, and lifestyle risk factors for open-angle glaucoma and ocular hypertension. The Los Angeles Latino eye study. e2 Ophthalmology. 2008;115(4):639–647
  12. Bonomi L, Marchini G, Marraffa M, et al. Vascular risk factors for primary open angle glaucoma: the Egna-Neumarkt study. Ophthalmology. 2000;107(7):1287–1293
  13. Tielsch JM, Katz J, Sommer A, et al. Hypertension, perfusion pressure, and primary open-angle glaucoma. A population-based assessment. Arch Ophthalmol. 1995;113(2):216–221
  14. Hulsman CA, Vingerling JR, Hofman A, et al. Blood pressure, arterial stiffness, and open-angle glaucoma: the Rotterdam study. Arch Ophthalmol. 2007;125(6):805–812
  15. Meyer JH, Brandi-Dohrn J, Funk J. Twenty four hour blood pressure monitoring in normal tension glaucoma. Br J Ophthalmol. 1996;80(10):864–867
  16. Yin ZQ, Vaegan , Millar TJ, et al. Widespread choroidal insufficiency in primary open-angle glaucoma. J Glaucoma. 1997;6(1):23–32
  17. Kerr J, Nelson P, O'Brien C. A comparison of ocular blood flow in untreated primary open-angle glaucoma and ocular hypertension. Am J Ophthalmol. 1998;126(1):42–51
  18. Halkiadakis I, Patsea E, Chatzimichali K, et al. Comparison of dynamic contour tonometry with Goldmann applanation tonometry in glaucoma practice. Acta Opthalmologica. 2009;87(3):323–328
  19. Punjabi OS, Ho HK, Kniestedt C, et al. Intraocular pressure and ocular pulse amplitude comparisons in different types of glaucoma using dynamic contour tonometry. Curr Eye Res. 2006;31(10):851–862
  20. Schmidt KG, von Ruckmann A, Mittag TW. [Ocular pulse amplitude in ocular hypertension and open-angle glaucoma]. Ophthalmologica. 1998;212(1):5–10
  21. Schmidt KG, Pillunat LE, Kohler K, et al. Ocular pulse amplitude is reduced in patients with advanced retinitis pigmentosa. Br J Ophthalmol. 2001;85(6):678–682
  22. Schmidt KG, von Ruckmann A, Kemkes-Matthes B, et al. Ocular pulse amplitude in diabetes mellitus. Br J Ophthalmol. 2000;84(11):1282–1284
  23. Schmidt KG, Ruckmann AV, Mittag TW, et al. Reduced ocular pulse amplitude in low tension glaucoma is independent of vasospasm. Eye. 1997;11(Pt 4):485–488
  24. Perkins ES. The ocular pulse. Curr Eye Res. 1981;1(1):19–23
  25. Stalmans I, Harris A, Vanbellinghen V, et al. Ocular pulse amplitude in normal tension and primary open angle glaucoma. J Glaucoma. 2008;17(5):403–407
  26. Schwenn O, Troost R, Vogel A, et al. Ocular pulse amplitude in patients with open angle glaucoma, normal tension glaucoma, and ocular hypertension. Br J Ophthalmol. 2002;86(9):981–984
  27. Vulsteke C, Stalmans I, Fieuws S, et al. Correlation between ocular pulse amplitude measured by dynamic contour tonometer and visual field defects. Graefes Arch Clin Exp Ophthalmol. 2008;246(4):559–565
  28. Weizer JS, Asrani S, Stinnett SS, et al. The clinical utility of dynamic contour tonometry and ocular pulse amplitude. J Glaucoma. 2007;16(8):700–703
  29. Schneider E, Grehn F. Intraocular pressure measurement-comparison of dynamic contour tonometry and Goldmann applanation tonometry. J Glaucoma. 2006;15(1):2–6
  30. Pache M, Wilmsmeyer S, Lautebach S, et al. Dynamic contour tonometry versus Goldmann applanation tonometry: a comparative study. Graefes Arch Clin Exp Ophthalmol. 2005;243(8):763–767
  31. Erickson DH, Goodwin D, Rollins M, et al. Comparison of dynamic contour tonometry and Goldmann applanation tonometry and their relationship to corneal properties, refractive error, and ocular pulse amplitude. Optometry. 2009;80(4):169–174
  32. Siganos DS, Papastergiou GI, Moedas C. Assessment of the Pascal dynamic contour tonometer in monitoring intraocular pressure in unoperated eyes and eyes after LASIK. J Cataract Refract Surg. 2004;30(4):746–751
  33. Kaufmann C, Bachmann LM, Thiel MA. Intraocular pressure measurements using dynamic contour tonometry after laser in situ keratomileusis. Invest Ophthalmol Vis Sci. 2003;44(9):3790–3794
  34. Pepose JS, Feigenbaum SK, Qazi MA, et al. Changes in corneal biomechanics and intraocular pressure following LASIK using static, dynamic, and noncontact tonometry. Am J Ophthalmol. 2007;143(1):39–47
  35. Bureau of the Census. Current population reports: population projections of the United States by age, sex, race, and Hispanic origin: 1995 to 2050. Available at http://www.census.gov/prod/1/pop/p25-1130/p251130.pdf. Last accessed May 20, 2009.
  36. Pourjavan S, Boelle PY, Detry-Morel M, et al. Physiological diurnal variability and characteristics of the ocular pulse amplitude (OPA) with the dynamic contour tonometer (DCT-Pascal). Int Ophthalmol. 2007;27(6):357–360
  37. Read SA, Collins MJ, Iskander DR. Diurnal variation of axial length, intraocular pressure, and anterior eye biometrics. Invest Ophthalmol Vis Sci. 2008;49(7):2911–2918
  38. Hamilton KE, Pye DC, Kao L, et al. The effect of corneal edema on dynamic contour and Goldmann tonometry. Optom Vision Sci. 2008;85(6):451–456
  39. Grieshaber MC, Katamay R, Gugleta K, et al. Relationship between ocular pulse amplitude and systemic blood pressure measurements. Acta Opthalmologica. 2009;87(3):329–334
  40. Carbonaro F, Andrew T, Mackey DA, et al. The heritability of corneal hysteresis and ocular pulse amplitude: a twin study. Ophthalmology. 2008;115(9):1545–1549
  41. Kaufmann C, Bachmann LM, Robert YC, et al. Ocular pulse amplitude in healthy subjects as measured by dynamic contour tonometry. Arch Ophthalmol. 2006;124(8):1104–1108
  42. Perkins ES. The ocular pulse and intraocular pressure as a screening test for carotid artery stenosis. Br J Ophthalmol. 1985;69(9):676–680
  43. James CB, Trew DR, Clark K, et al. Factors influencing the ocular pulse–axial length. Graefes Arch Clin Exp Ophthalmol. 1991;229(4):341–344
  44. McBrien NA, Gentle A. Role of the sclera in the development and pathological complications of myopia. Progress in Retinal & Eye Research. 2003;22(3):307–338
  45. Silver DM, Geyer O. Pressure-volume relation for the living human eye. Curr Eye Res. 2000;20(2):115–120
  46. Wolfs RC, Klaver CC, Vingerling JR, et al. Distribution of central corneal thickness and its association with intraocular pressure: the Rotterdam study. Am J Ophthalmol. 1997;123(6):767–772
  47. Foster PJ, Baasanhu J, Alsbirk PH, et al. Central corneal thickness and intraocular pressure in a Mongolian population. Ophthalmology. 1998;105(6):969–973
  48. Klein BE, Klein R, Linton KL. Intraocular pressure in an American community. The Beaver Dam eye study. Invest Ophthalmol Vis Sci. 1992;33(7):2224–2228
  49. Francis BA, Hsieh A, Lai MY, et al. Effects of corneal thickness, corneal curvature, and intraocular pressure level on Goldmann applanation tonometry and dynamic contour tonometry. Ophthalmology. 2007;114(1):20–26
  50. Doyle A, Lachkar Y. Comparison of dynamic contour tonometry with Goldman applanation tonometry over a wide range of central corneal thickness. J Glaucoma. 2005;14(4):288–292
  51. Grieshaber MC, Schoetzau A, Zawinka C, et al. Effect of central corneal thickness on dynamic contour tonometry and Goldmann applanation tonometry in primary open-angle glaucoma. Arch Ophthalmol. 2007;125(6):740–744
  52. Medeiros FA, Sample PA, Weinreb RN. Comparison of dynamic contour tonometry and Goldmann applanation tonometry in African American subjects. Ophthalmology. 2007;114(4):658–665
  53. La Rosa FA, Gross RL, Orengo-Nania S. Central corneal thickness of Caucasians and African Americans in glaucomatous and nonglaucomatous populations. Arch Ophthalmol. 2001;119(1):23–27
  54. Congdon NG, Broman AT, Bandeen-Roche K, et al. Central corneal thickness and corneal hysteresis associated with glaucoma damage. Am J Ophthalmol. 2006;141(5):868–875
  55. Kempen JH, Mitchell P, Lee KE, et al. The prevalence of refractive errors among adults in the United States, western Europe, and Australia. Arch Ophthalmol. 2004;122(4):495–505
  56. Tarczy-Hornoch K, Ying-Lai M, Varma R, et al. Myopic refractive error in adult Latinos: The Los Angeles Latino eye study. Invest Ophthalmol Vis Sci. 2006;47(5):1845–1852

PII: S1529-1839(10)00249-6

doi:10.1016/j.optm.2010.02.012

Optometry - Journal of the American Optometric Association
Volume 81, Issue 8 , Pages 408-413, August 2010

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