April 2003
Volume 44, Issue 4
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Cornea  |   April 2003
Central Corneal Thickness in Latinos
Author Affiliations
  • Sora Hahn
    From the Department of Ophthalmology and the
  • Stanley Azen
    From the Department of Ophthalmology and the
    Statistical Consultation and Research Center, Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California.
  • Mei Ying-Lai
    Statistical Consultation and Research Center, Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, California.
  • Rohit Varma
    From the Department of Ophthalmology and the
Investigative Ophthalmology & Visual Science April 2003, Vol.44, 1508-1512. doi:10.1167/iovs.02-0641
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      Sora Hahn, Stanley Azen, Mei Ying-Lai, Rohit Varma, the Los Angeles Latino Eye Study Group; Central Corneal Thickness in Latinos. Invest. Ophthalmol. Vis. Sci. 2003;44(4):1508-1512. doi: 10.1167/iovs.02-0641.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

purpose. To characterize central corneal thickness (CCT) in Latinos aged 40 or more years.

methods. A population-based cohort of Latinos from two census tracts in La Puente, California, underwent measurements of CCT and intraocular pressure (IOP). CCT was measured with an ultrasonic pachymeter, and IOP was measured by applanation tonometry. One eye of each of 1699 participants was included in the analyses.

results. The mean (±SD) CCT was 546.9 ± 33.5 μm. Older participants (≥70 years) had significantly thinner CCs compared with participants 40 to 49 years of age (P < 0.05). Eyes with ocular hypertension had thicker CCs than did normal and glaucomatous eyes (P < 0.05). Multivariate adaptive regression spline analyses and analysis of variance contrasting IOP subgroups revealed that eyes with thinner CCs had lower IOP than did eyes with thicker CCs (P < 0.001). The absolute range of interocular differences in CCT in the same subject was as high as 24 μm.

conclusions. On average, CCT in Latinos was less than that previously reported in whites but greater than that reported in African Americans and Asians. Older Latinos had thinner corneas compared with younger Latinos. Asymmetry in CCT of 25 μm or more should be evaluated for potential corneal disease. Spline analyses suggest that although the relationship between IOP and CCT is best explained by a nonlinear equation, when measuring IOP with the Goldmann tonometer, it is likely that IOP is underestimated in eyes with thinner CCs and overestimated in eyes with thicker CCs.

Central corneal thickness (CCT) is an important indicator of corneal health status. As an estimate of the corneal barrier and endothelial pump function, CCT is an essential tool in the assessment and management of corneal disease. With the advent of laser refractive surgery, there has been an increased interest in CCT, because an accurate measurement of CCT is essential in assessing a patient’s eligibility for laser refractive surgery and in preventing possible surgical complications. 
Also, CCT is a measure of corneal rigidity and consequently has an impact on the accuracy of intraocular pressure (IOP) measurement by applanation tonometry. Numerous studies have demonstrated that thicker corneas with greater rigidity may offer a greater resistance when subjected to applanation, resulting in an artificially higher IOP reading. 1 2 3 4 5 6 7 In fact, many studies have suggested that CCT is greater in patients with ocular hypertension than in the general population. 8 9 10 11 12 13 14 Similarly, applanation IOP measurements in patients after laser-assisted in situ keratectomy have demonstrated that after ablation of the central corneal stroma, there is a decrease in the postablation IOP by as much as 6 mm Hg. 15 16 17 18 19 Changes in the thickness of the cornea after the procedure are suggested to be a primary reason for the change in the IOP readings. These observations further support the assumptions of Goldmann and Schmidt 20 that corneal rigidity (and its surrogate corneal thickness) may affect the accuracy of IOP readings obtained by applanation tonometry. 
CCT in the general population is related to many demographic and ocular factors, and this should be considered when evaluating the health of the cornea. Recent studies have shown that gender, race and/or ethnicity, and age may influence CCT. 21 22 23 24 25 26 27 28 29 30 Specifically, the most consistent relationships suggest that the CC is thinner in older individuals, 22 25 26 27 28 29 Mongolians, 22 and African-Americans than in whites. 8 21 23  
The Los Angeles Latino Eye Study (LALES) is a population-based prevalence survey of ocular disease in Latinos aged 40 or more years and living in the city of La Puente in Los Angeles County, California. As part of the complete ophthalmic examination, measurements of CCT and IOP were obtained. The purpose of this article is to characterize CCTs in Latinos, to compare CCTs across persons with normal, ocular hypertensive, or glaucomatous eyes, and to determine the relationship of CCT with age, gender, and IOP. 
Methods
The study cohort consisted of self-identified Latinos aged 40 or more years and living in two census tracts in the City of La Puente, California. The Institutional Review Board at the University of Southern California approved the study protocol. All study procedures adhered to the Declaration of Helsinki for research involving human subjects. After informed consent was obtained, an in-home interview was conducted to obtain demographic information, ocular and medical risk factors, history of ocular and medical disease, visual acuity, access to care, and insurance status. An appointment was then made for a clinic examination at the local eye examination center for a complete ocular examination by one of three study-certified ocular technicians and an ophthalmologist. The ophthalmic examination included a measurement of visual acuity, slit lamp examination, measurement of IOP and CCT, visual field testing (Visual Field Analyzer; Zeiss-Humphrey Systems, Dublin, CA), indirect and direct ophthalmoscopy, and optic disc and fundus photography. All demographic and ophthalmic data were entered into a database system with built-in range and quality-control checks. 
At the clinic visit, three measurements of IOP by Goldmann applanation tonometry (Haag-Streit, Bern, Switzerland) and three measurements of CCT by an ultrasonic pachymeter (A-Scan; Exton, PA) were obtained in each eye by a single certified technician. Because the three measurements of CCT demonstrated intratechnician reliability (coefficient of variation was obtained by 100 × CCT SD/mean CCT; 100 × 4.65 μm/546.8 μm = 0.85%; intertechnician range, 0.66%–1.11%), the average CCT was used in the statistical analysis as the best estimate of CCT. 
Statistical Analysis
For the purpose of statistical analyses, we excluded participants with a history of corneal disease, ocular trauma, and/or ocular surgery in one or both eyes, as well as participants who had been treated for a prior diagnosis of glaucoma in one or both eyes. These participants were excluded, because either we could not estimate IOP accurately in their eyes (eyes with corneal stromal scars, eyes on treatment for glaucoma) or CCT was likely to be modified by the underlying disease state (e.g., eyes with evidence of Fuchs’ dystrophy, corneal edema, or stromal scarring). For each participant included in the study cohort, we characterized each eye as normal, exhibiting ocular hypertension, or first diagnosed as having glaucoma during the clinic examination (previously untreated glaucoma). Ocular hypertension was defined as IOP of 21 mm Hg or higher, with no evidence of glaucomatous optic nerve damage or glaucomatous visual field loss. Glaucoma was defined by the presence of evidence of characteristic or compatible glaucomatous optic nerve damage and two reliable congruent visual field test results characteristic or compatible with glaucomatous abnormality (after other possible causes for the visual field findings were excluded). Characteristic and/or compatible visual field defects included: nasal steps, paracentral defects, arcuate defects, central islands, temporal islands, and altitudinal loss. Characteristic or compatible glaucomatous optic nerve damage included asymmetric cupping with an interocular difference of 0.3 or more; horizontal or vertical cup-to-disc ratio of 1.0; cup/disc of 0.8 or more and limited loss of neural rim tissue to disc margin, including notching of neural rim tissue, diffuse thinning of neural rim, disc or peripapillary nerve fiber layer hemorrhage, and thinning or defect in the nerve fiber layer in the arcuate areas. IOP was not considered in the diagnosis of glaucoma. Normal eyes had no clinical evidence of glaucoma or ocular hypertension detected in the ophthalmic examination. 
We selected one eye of each participant for the statistical analysis, using the following algorithm: If both eyes were normal, then one eye was chosen at random. If only one eye had ocular hypertension or glaucoma, then that eye was chosen for statistical analysis. If both eyes had ocular hypertension or glaucoma was diagnosed in both eyes, then one eye was chosen at random. 
Statistical analyses were conducted on data from all selected eyes, using this selection algorithm, and was stratified by the subgroups of normal, ocular hypertensive, and glaucomatous eyes. Normal ranges for CCT were calculated in all eyes and in each subgroup of eyes. In addition, age and gender-specific normal ranges of CCT were calculated in all eyes and in the subgroup of normal eyes. A 95% normal range (defined as the mean ± 1.96 SD) summarizes the range of CCTs in 95% of the eyes in the subgroup of interest (e.g., normal eyes, ocular hypertensive eyes, eyes in participants ≥70 years of age). 
The relationship of CCT was contrasted across subgroups using analysis of variance with pair-wise comparisons by the Tukey honest significant different (HSD) procedure. To determine the correlation of CCT with IOP, linear regression and correlational procedures (with and without adjusting for age and gender as covariates) were used. The dependent variable was CCT, and the independent variable was IOP. In addition, the relationship between CCT and IOP was modeled with a multivariate adaptive regression spline (MARS) procedure. All statistical testing was conducted at the 0.05 significance level and was performed on computer (SAS, Cary, NC; MARS, Salford Systems, San Diego, CA). 
Results
Description of Study Cohort
Of the 3090 eligible participants from two census tracts, 2720 (88%) participated in the study. Of these, 2060 (76%) completed both the in-home questionnaire and clinical examination (complete participants), whereas 660 (24%) completed only the in-home questionnaire (partial participants). Compared with the group of complete participants, partial participants were more likely to be men (P = 0.02), less than 60 years of age (P < 0.0001) and employed (P = 0.01), and they were less likely to have a history of hypertension (P < 0.02) or diabetes (P < 0.01). No age and gender differences were found when the participants were compared with nonparticipants. 
Of the 2060 complete participants, 361 (17%) were excluded for not meeting one or more of the study criteria (non-mutually exclusive criteria) in one or both eyes: 222 participants had corneal diseases (e.g., dystrophies, scars, edema), 116 had a history of intraocular surgery, 47 had a history of ocular trauma, and 37 had been treated for glaucoma. 
Table 1 presents the demographic, clinical, and ocular characteristics of the study cohort of 1699 participants. The mean ± SD age of all participants was 53.9 ± 10.5 years, and 59% of study participants were women. The majority (86%; n = 1411) reported themselves to be of Mexican origin. Of the 1699 participants, 1578 (93%) were classified as normal in both eyes, 55 (3%) had ocular hypertension (37 in one eye, 18 in both eyes), and 66 (4%) had glaucoma (31 in one eye, 35 in both eyes). Thus, the cohort of eyes consisted of 1631 randomly selected eyes (1578 normal eyes, 18 ocular hypertensive eyes, and 35 glaucomatous eyes) and 68 specifically selected eyes (37 ocular hypertensive and 31 glaucomatous eyes). 
Comparison of CCT between Complete and Partial Participants
Overall, the average ± SD CCT for complete participants was 546.9 ± 33.5 μm (95% CI: 545.3–548.5 μm). To evaluate selection bias between the two groups of participants, we used a standard imputation procedure for estimating the CCTs of the partial participants only. In brief, for the complete participants, we developed a multiple regression model that related CCT (dependent variable) to those demographic and clinical factors that were significantly different between the two subgroups (gender, age, employment status, history of diabetes, and history of hypertension). From this regression model, we estimated the CCTs in the partial participants. We found that the predicted average CCT in partial participants was 546.9 μm (95% CI: 546.6–547.3), equivalent to that in complete participants (P > 0.99). Thus, no apparent selection bias was found for the complete participants. 
Comparison of CCT between Included and Excluded Eyes
The average CCT in eyes that were excluded was compared with the CCT of eyes that were included in the analysis. On average, eyes that were excluded had significantly thicker CCs than those that were included (551.7 ± 38.7 μm vs. 546.9 ± 33.5 μm, P < 0.04). 
Normal Ranges of CCT
Table 2 presents the means and normal ranges of CCT in the entire cohort and in normal, ocular hypertensive, and glaucomatous eyes. The normal range in normal eyes was 479.7 to 613.4 μm, indicating that 95% of the eyes in the population have CCTs in this range. Analysis of variance revealed statistically significant differences in average CCT across the three subgroups (P = 0.005). On average, eyes with ocular hypertension had thicker corneas than did normal and glaucomatous eyes (P < 0.05; Tukey multiple-comparison procedure). Also shown in Table 2 is the normal range (0.0–24.0 μm) of the absolute value of the interocular difference in CCT in normal eyes. 
Table 3 presents the means and normal ranges of CCT stratified by gender and age in all eyes and in normal eyes. Compared with the men, the women had significantly thinner CCs (entire cohort of eyes, P = 0.02, and normal eyes, P = 0.006, with and without adjusting for age). Analysis of variance revealed statistically significant differences in average CCT across the four age groups (entire cohort of eyes, P = 0.009 and for normal eyes, P = 0.02). On average, older participants (≥70 years) had significantly thinner CCs than did participants 40 to 49 years of age (P < 0.05; Tukey multiple-comparison procedure). Because samples were small, no age or gender differences were detectable in groups with ocular hypertension or glaucoma (data not shown in table). Finally, linear regression analysis between CCT and age revealed a statistically significant decrease in CCT of 2.9 μm per decade (P = 0.0001). However, age explained less 1% of the variation in CCT. We also used multivariate adaptive regression splines to identify cutpoints at which changes in the slope of the trend line between CCT and age occurred. No cutpoints were identified from these analyses, suggesting no threshold effect of CCT with age. 
Relationship of CCT to IOP
In our population of Latinos, linear regression analysis between CCT and IOP revealed a difference in IOP of 1.4 mm Hg per 100 μm difference in CCT. Although this was statistically significant (P < 0.0001), IOP explained only 2.6% of the variation in CCT (and vice versa). Linear regression analyses between CCT and IOP, adjusting for age and gender, slightly improved the predictive relationship of IOP from 2.6% to 4.1% of the variation in CCT. We also conducted a linear regression analysis comparing CCT with corrected IOP, using data from Ehlers et al. 1 Improvement in the predictive relationship between IOP and CCT was noted; the corrected IOP now explained 15.8% of the variation in CCT. 
We further examined the relationship of IOP to CCT by using MARS. As shown in Figure 1 , one reason for the poor goodness of fit is the nonlinearity of the relationship of CCT with IOP. Break points at which changes in the slope of the trend line between CCT and IOP were identified were at IOPs of 10, 15, and 21 mm Hg. The mean CCT (95% CI) in the four IOP subgroups (Fig. 2) were 535.0 μm (528.8–541.1) in the 10-mm Hg and less subgroup (n = 14); 544.7 μm (542.6–546.7) in the 11- to 15-mm Hg subgroup (n = 1014); 553.2 μm (550.4–556.0) in the 16- to 21-mm Hg subgroup (n = 546), and 550.6 μm (533.2, 567.9) in the more than 21-mm Hg subgroup (n = 22). Because of the large variability in CCT in the more than 21-mm Hg subgroup (Fig. 2) , comparisons in average CCT across subgroups were made with nonparametric analysis of variance with Bonferroni-adjusted pair-wise comparisons. Statistical analyses revealed a statistically significant difference across the four subgroups (P < 0.0001). Pair-wise comparisons revealed a significant difference in average CCT between the less than 10-mm Hg and the 11- to 15-mm Hg and 16- to 21-mm Hg subgroups, and the 11- to 15-mm Hg and the 16- to 21-mm Hg subgroups (P < 0.01). 
Linear regression analysis was also used to evaluate the relationship of the interocular difference in CCT and the interocular difference in IOP. No significant relationship was detected (P = 0.57). 
Discussion
With the introduction of laser refractive procedures, there has been an increasing interest in determining and evaluating differences in normal CCT. Although the Latino population is the fastest growing ethnic minority in the United States, CCT in Latinos has not previously been evaluated. LALES provided us the opportunity to study the CCT in a population-based sample of Latinos. As we did not find any difference between the CCT in the participants, with and without adjustment for nonparticipation, we believe that our data accurately reflect a population-based CCT measurement in Latinos. We found an average CCT of 546.9 μm in Latinos aged 40 years or more. In a meta-analysis of the worldwide literature including various ethnic groups and races (whites, blacks, and Asians), the average normal CCT according to ultrasound pachymetry (544 μm), was similar to the one found in our Latino population. 30  
Previous studies have revealed that there are ethnicity-related differences in the average CCT. 22 23 25 La Rosa et al., 23 using ultrasonic pachymetry, reported that the average CCT in whites (approximately 556 μm) is more than the average CCT in African Americans (approximately 534 μm). Foster et al., 22 using optical pachymetry, reported that the mean right and left eye CCT in Mongolians were 495 and 514 μm, respectively. Our data on Latinos suggest that, on average, normal Latinos have thinner CCs than do whites, but thicker than the average observed in Asians 22 25 and African Americans. 23 However, caution should be exercised in interpreting these conclusions, because variations in the age and gender distribution of the population and differences in CCT measurement methodology (optical versus ultrasonic pachymetry) may contribute to differences in the reported CCTs. Previous studies have shown that optical pachymetry is prone to errors, especially because of misalignment of the device along the visual axis instead of the geometric center of the cornea. This may lead to interobserver differences between and right and left eyes readings when optical pachymetry is used. 22 23 24 25 Such measurement errors can be avoided if ultrasound pachymetry is used. 31  
Age-related differences in CCT have also been noted in some ethnic groups, particularly later in life when the CC appears to be thinner. 22 23 25 In whites, however, there is no substantial evidence demonstrating differences in CCT related to age. In fact, studies in whites have reported contradictory results, suggesting that older whites may have either thicker or thinner CCs than younger whites. 2 21 25 28 32 In Asians (including Japanese, Chinese, Eskimos, and Mongolians) a difference of 3 to 7 μm per decade was found, with older individuals having thinner CCs than younger individuals. 22 25 We found similar results in our group of Latinos. In the normal group, we found that compared with those aged 40 to 49 years, individuals aged 50 to 59 and 60 to 69 years had, on average, a moderately thinner CC (3.4 and 4.1 μm, respectively, Table 3 ). However, the most clinically significant finding was in those aged 70 or more years. When compared with normal Latinos aged 40 to 49 years, Latinos aged 70 or more years had substantially thinner corneas on average (9.0 μm, P < 0.05, Table 3 ). These age-related differences have also been observed in other ethnic groups and have two possible explanations. The first explanation, and in our view the more probable, supported by histologic evidence, is that older individuals have thinner CCs because of a decline in the density of keratocytes and a probable breakdown in the collagen fibers in the aging cornea. 29 Second, we cannot exclude the possibility that a cohort effect is responsible for this finding—perhaps an environmental factor that older individuals may have been exposed to longer than younger ones may have and that could have affected the structure or the integrity of the cornea. 
There is no general consensus on the gender-related differences in CCT. Most studies have shown no gender-related differences. 9 11 22 25 27 In our cohort of normal Latinos, we found small (but statistically significant) gender-related differences, with men having thicker CCs than did women (4.6 μm, Table 3 ). However, we believe that these differences are not clinically significant. 
The intraocular variability in three CCT determinations was found to be 4.65 μm (see the Methods section), which suggests that an observed intraocular change in CCT over time greater than 2 × 4.65 μm = 9.3 μm may be of clinical relevance. In addition, the upper limit of the 95% normal range for the interocular difference was 24.9 μm (Table 2) , suggesting that a per-patient interocular difference in CCT greater than 24.9 μm (as measured by the average of three determinations per eye) may be of clinical importance. 
IOP, measured by applanation tonometry, has also been demonstrated to correlate with CCT. In fact, the idea that CCT may influence the accuracy in the readings of the IOP is not recent. The relationship of IOP to CCT was first introduced by Goldmann and Schmidt 20 when they designed the applanation tonometer. Although Goldmann and Schmidt acknowledged that changes in CCT could theoretically change the reading of IOP, a tonometer head with a diameter of 3.06 mm was designed to indent an area of the cornea with a central corneal thickness of 520 μm. The clinical implication of the relationship of IOP to CCT relates to the fact that IOP readings measured by applanation tonometry may depend on the rigidity of the cornea, which is related to CCT. 20 As a result, some studies have indicated the need for a CCT-related adjustment in applanation tonometry readings when measuring IOP. 1 2 3 4 5 6 Indeed, studies have confirmed the relationship between CCT and IOP in normal subjects, demonstrating a positive association between IOP and CCT. The difference in IOP ranged from 1.1 to 3.2 mm Hg per 100 μm difference in CCT. 5 9 21 In our sample of Latinos with normal eyes, we found a difference in IOP of 1.4 mm Hg per 100 μm difference in CCT. However, it is important to point out that CCT explained only between 2.6% (regression analysis) and 15.8% of the variation in CCT (IOP-adjusted analysis). For this reason, we believe that CCT-related adjustments in the applanation tonometry readings are needed when examining individuals. 
The strengths of our study are that it was a population-based study with a large sample of participants (n = 1699) who underwent standardized methods of examination, including ultrasonic pachymetry and Goldmann applanation tonometry. Thus, the selection biases of a clinic-based sample are not likely to be present in our study. However, a potential weakness of our study is that we were unable to comment on the CCT in individuals younger than 40 years and older than 80 years. In addition, due to small sample sizes, we were unable to make robust conclusions on the relationship between IOP and CCT in eyes with IOP of 10 mm Hg or less or more than 21 mm Hg. Furthermore, because this was a prevalence study in which examinations were performed at a single time point, we were unable to comment on the association of changes in CCT with changes in age or IOP. 
The purpose of this study was to characterize the CCT in an adult population of Latinos. We found that, although the variation in CCT in this group was large, there were moderate age-related differences in CCT. We also found a significant correlation between CCT and IOP. However, we believe that although the CCT and IOP correlated highly, the relationship is not a linear one but is complex and that it varies with the different levels of IOP. We found that individuals with lower IOPs had thinner corneas, whereas participants with higher IOPs had thicker corneas, on average. This observation supports the hypothesis that, when measured by an applanation tonometer, IOP is overestimated in eyes with thicker corneas and underestimated in eyes with thinner corneas. 
We believe that CCT should be measured along with IOP in all patients and especially in individuals with low or high IOP and in individuals with inconsistent IOP readings and clinical presentation (glaucomatous optic disc changes and visual field loss). 
Appendix 1
The Los Angeles Latino Eye Study Group
LaVina Abbott, Elisa Arevalo, Stanley P. Azen, Lupe Cisneros, Elizabeth Corona, Carolina Cuestas, Denise R. Globe, Sora Hahn, Ronald Klein, Mei Lai, George Martinez, Marta Mora, Sylvia Paz, Susan Preston-Martin, Ronald E. Smith, Mina Torres, Natalie Uribe, Rohit Varma, and Myrna Zuniga. 
 
Table 1.
 
Demographic and Ocular Characteristics in Study Cohort
Table 1.
 
Demographic and Ocular Characteristics in Study Cohort
Characteristics n (%)
Gender
 Male 692 (41)
 Female 1007 (59)
Age (y)*
 40–49 714 (42)
 50–59 491 (29)
 60–69 330 (19)
 70+ 164 (10)
National origin
 Mexican, Mexican American, Chicano 1411 (86)
 Puerto Rican 11 (<1)
 Cuban 6 (<1)
 Other Spanish/Hispanic/Latino 209 (13)
Ocular diagnosis
 Normal 1,578 (93)
 Ocular hypertension 55 (3)
 Glaucoma 66 (4)
Table 2.
 
Normal Ranges for CCT in Latinos
Table 2.
 
Normal Ranges for CCT in Latinos
Subgroup Frequency (%) Mean (Normal Range)*
CCT in selected eye
 Entire cohort 1699 (100) 546.9 (480.0–613.9)
 Normal 1578 (93) 546.5 (479.7–613.4)
 Ocular hypertensive 55 (3) 561.2 (492.0–630.4)
 Glaucoma 66 (4) 544.6 (481.0–608.2)
Interocular difference in CCT (absolute value)
 Normal 1578 (93) 7.7 (0.0–24.9)
Table 3.
 
Gender-and Age-Specific Normal Ranges for CCT in Latinos
Table 3.
 
Gender-and Age-Specific Normal Ranges for CCT in Latinos
Entire Cohort (n = 1699) Normals (n = 1578)
Gender
 Male 549.2 (482.3–616.0) 549.3 (481.6–617.1)
(n = 692) (n = 634)
 Female 545.4 (478.5–612.3) 544.7 (478.7–610.6)
(n = 1007) (n = 944)
P 0.02 0.006
Age group (y)
 40–49 549.5 (482.4–616.7)* 549.1 (481.8–616.4)*
(n = 714) (n = 684)
 50–59 546.8 (482.0–611.6) 545.7 (481.6–609.8)
(n = 491) (n = 460)
 60–69 544.7 (475.7–613.6) 545.0 (475.3–614.6)
(n = 330) (n = 295)
 70+ 540.7 (474.0–607.4)* 540.1 (474.5–605.6)*
(n = 164) (n = 139)
P 0.009 0.02
Figure 1.
 
Spline graph of CCT in relation to IOP.
Figure 1.
 
Spline graph of CCT in relation to IOP.
Figure 2.
 
Average (95% CI) CCT in Latinos, stratified by IOP group.
Figure 2.
 
Average (95% CI) CCT in Latinos, stratified by IOP group.
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Figure 1.
 
Spline graph of CCT in relation to IOP.
Figure 1.
 
Spline graph of CCT in relation to IOP.
Figure 2.
 
Average (95% CI) CCT in Latinos, stratified by IOP group.
Figure 2.
 
Average (95% CI) CCT in Latinos, stratified by IOP group.
Table 1.
 
Demographic and Ocular Characteristics in Study Cohort
Table 1.
 
Demographic and Ocular Characteristics in Study Cohort
Characteristics n (%)
Gender
 Male 692 (41)
 Female 1007 (59)
Age (y)*
 40–49 714 (42)
 50–59 491 (29)
 60–69 330 (19)
 70+ 164 (10)
National origin
 Mexican, Mexican American, Chicano 1411 (86)
 Puerto Rican 11 (<1)
 Cuban 6 (<1)
 Other Spanish/Hispanic/Latino 209 (13)
Ocular diagnosis
 Normal 1,578 (93)
 Ocular hypertension 55 (3)
 Glaucoma 66 (4)
Table 2.
 
Normal Ranges for CCT in Latinos
Table 2.
 
Normal Ranges for CCT in Latinos
Subgroup Frequency (%) Mean (Normal Range)*
CCT in selected eye
 Entire cohort 1699 (100) 546.9 (480.0–613.9)
 Normal 1578 (93) 546.5 (479.7–613.4)
 Ocular hypertensive 55 (3) 561.2 (492.0–630.4)
 Glaucoma 66 (4) 544.6 (481.0–608.2)
Interocular difference in CCT (absolute value)
 Normal 1578 (93) 7.7 (0.0–24.9)
Table 3.
 
Gender-and Age-Specific Normal Ranges for CCT in Latinos
Table 3.
 
Gender-and Age-Specific Normal Ranges for CCT in Latinos
Entire Cohort (n = 1699) Normals (n = 1578)
Gender
 Male 549.2 (482.3–616.0) 549.3 (481.6–617.1)
(n = 692) (n = 634)
 Female 545.4 (478.5–612.3) 544.7 (478.7–610.6)
(n = 1007) (n = 944)
P 0.02 0.006
Age group (y)
 40–49 549.5 (482.4–616.7)* 549.1 (481.8–616.4)*
(n = 714) (n = 684)
 50–59 546.8 (482.0–611.6) 545.7 (481.6–609.8)
(n = 491) (n = 460)
 60–69 544.7 (475.7–613.6) 545.0 (475.3–614.6)
(n = 330) (n = 295)
 70+ 540.7 (474.0–607.4)* 540.1 (474.5–605.6)*
(n = 164) (n = 139)
P 0.009 0.02
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