factors influencing central corneal thickness in a turkish population

Current Eye Research, 32:413–419, 2007Copyright ©c Informa HealthcareISSN: 0271-3683 print / 1460-2202 onlineDOI: 10.1080/02713680701344361

Factors Influencing Central CornealThickness in a Turkish Population

A. Altinok,E. Sen, andA. YaziciM.D. Ulucanlar Eye Educationand Research Hospital, Ankara,Republic of Turkey

F. N. AksakalM.D. Gazi University Faculty ofMedicine, Department ofPublic Health, Ankara, Republicof Turkey

H. Oncul andG. KokluM.D. Ulucanlar Eye Educationand Research Hospital, Ankara,Republic of Turkey

ABSTRACT Purpose: The aim of this study is to find out the central cornealthickness (CCT) values for a Turkish patient group and to investigate the possi-ble influences of age, sex, IOP, refractive status, keratometry readings, systemicdisorders (hypertension, diabetes mellitus, hyperlipidemia, heart disease andasthma) on CCT values. Materials and Methods: Six hundred twenty five sub-jects (276 male (44%), 349 female (56%)) of ages 6 to 88 years were recruited.Subjects who had corneal diseases, purulent conjunctivitis or blepharitis wereexcluded. Refraction and keratometry readings were made by MRK-3100 pre-mium auto-ref/keratometer, IOP was measured by Reichert AT-555 auto non-contact pnomotonometer. Results: Mean age was 44.1 ± 16.6 years ± SD formale subjects, 41.0 ± 16.9 for females. Mean CCT ± SD values for male was552.2 ± 35.9 μm, for female was 552.3 ± 35.4 μm, respectively. There wasno significant difference between right and left eye CCT values for both gen-ders. Age and CCT was not correlated for the whole study group but there wasa slight negative correlation in male subjects. IOP and CCT had moderatelysignificant correlation for males and females. There was a slight significant cor-relation between Kh-Kv and CCT values for the whole group. In a multivariateregression model only Kv values seemed to affect CCT values. Discussion: Thereare studies showing the variation of CCT values among different nations andethnicities. There is no aggreement about the relationship between age, IOP,Kh-Kv, spherical equivallance of refractive error, systemic disorders, menapouseand CCT. In our study CCT was correlated with Kh-Kv and IOP in correlationanalysis but in multivariate regression analysis only Kv appeared to influencecorneal thickness.

KEYWORDS central corneal thickness; intraocular pressure; keratometry; Turkish

INTRODUCTIONCentral corneal thickness (CCT) has been the subject of many studies since

1970.1−4 When Goldmann and Schmidt first described the applanation tonome-ter, they assumed a standard CCT, and theorized that CCT might influenceapplanation readings.5 Later on, the effect of CCT variation on intraocularpressure (IOP) readings, achieved by Goldmann applanation tonometry, wasreported in a number of studies.6−9 With the increasing popularity of corneal

Received 29 August 2006Accepted 13 March 2007

Correspondence: Alper Yazici, M.D.,Ugur mumcu mah. Detca 1 sitesino: 333 06370 Batikent, Ankara,Republic of Turkey.E-mail: [email protected]

413

Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

refractive surgery, CCT has become an important clini-cal concern with regard to the amount of laser ablationand residual corneal stromal thickness.

As a result of its effects on IOP, CCT is alsoan important concern in the diagnosis and treatmentof glaucoma. Studies have shown that less thickenedcorneas are associated with lower IOP readings and,similarly, higher IOP readings are observed in thickercorneas.10−13 Because there are, however, limitationsattached to IOP measurement methods, and becauseIOP measurement is particularly important in glaucomapractice, CCT has been studied in glaucoma patientswhose CCT measurements might be affected by glau-coma medications.14,15 Studies comparing CCT valuesof persons of different nationalities and ethnicities havealso been performed.4,16−20

The objectives of this study were to examine CCTvalues of a Turkish patient population as well as to inves-tigate the possible influences of age, sex, IOP, refractivestatus, keratometry readings, and systemic disorders-hypertension (HT), diabetes mellitus (DM), hyperlipi-demia, heart disease, and asthma—on CCT values.

MATERIALS AND METHODSA total of 625 subjects were recruited from among

patients admitted to our clinic between March 2005and February 2006. All subjects were informed of thestudy objectives and their oral consent obtained. Nosubject was a contact lens wearer. Excluded from thestudy were those with corneal disease, prurulent con-junctivitis, blepharitis, or glaucoma.

All measurements were made between 9 a.m. and 12p.m., and all were made by the same technician. CCTwas evaluated after IOP, autorefractometry, and ker-atometry measurements had been completed. Refrac-tometry and keratometry readings were accomplishedusing an MRK-3100 premium auto-ref/keratometer(Huvitz Company, Gyeonggi-do, Korea). IOP was mea-sured using a Reichert AT-555 noncontact tonometer(Reichert Ophthalmic Instruments, New York, USA)and the mean of four consecutive readings recorded.CCT was measured using a Tomey AL-1000 ultrasoundbio-pachymeter (Tomey Corporation, Nagoya, Japan)and the average of four consecutive readings recorded.Both hypermetropic and myopic readings were clas-sified into dioptrical groups. All subjects were ques-tioned with regard to any systemic diseases they mighthave.

Differences between the mean values of CCT, age,IOP, keratometer horizontal (Kh), keratometer vertical(Kv), and comparative CCT values for left and right eyeswere evaluated by Student’s t test with respect to gen-der. CCT values with respect to systemic diseases wereevaluated by Student’s t and Mann-Whitney U tests.Pearson correlation analysis was performed to evalu-ate the relationship between CCT and age, IOP, Kh,and Kv; Spearman’s correlation analysis was used toevaluate the relationship between CCT and refractivestatus.

Possible factors affecting CCT were estimated bymultivariate regression analysis. Age, sex, existence ofDM, HT, or hyperlipidemia, and Kh-Kv parameterswere included in the regression model. p values of <0.05were considered statistically significant. All statisticalanalyses were performed using SPSS Version 13.0 sta-tistical analysis software.

RESULTSA total of 625 subjects, comprising 276 (44%) men

and 349 (56%) women, aged 6–88 years, were recruitedinto the study. Our male and female subjects had anage profile (mean ± SD) of 44.1 ± 16.6 and 41.0 ±16.9 years, respectively. Mean CCT ± SD values formale right and left eyes were 552.2 ± 35.9 and 553.4 ±36.3 μm, respectively; and those for female right andleft eyes were 552.3 ± 35.4 and 553.9 ± 35.9 μm, respec-tively. Mean Kh-Kv values of male and female subjectswere 43.5 ± 1.6/42.9 ± 1.7 and 43.7 ± 1.6/43.4 ± 2.4,respectively. Values for mean and standard deviationby gender for age, CCT, IOP, Kh, and Kv are shown inTable 1 for the right eye only.

There were no significant differences between rightand left eye CCT values for either gender (Student’s ttest, p > 0.05).

Because there was a very strong correlation betweenright and left eye CCT values (Pearson correlation test,r = 0.945, p = 0.000) and Kh-Kv readings (Pearsoncorrelation test, r = 0.847, p = 0.000), only CCT andKh-Kv values for the right eye were used for analy-sis in this study. Correlation coefficients and corre-sponding significance levels (p values) of CCT and age,IOP, Kh-Kv, myopia, and hypermetropia are shown inTable 2.

Age and CCT were not correlated for the entirestudy group (Pearson correlation test, r = −0.073, p =0.069). In male subjects, however, there was a slight

A. Altinok et al. 414

Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

TABLE 1 Correlation coefficients (r) and probability values (p) of CCT with age, IOP, Kh, Kv, and myopic andhypermetropic refractive errors

Pearson r (p) Spearman r (p)

CCT vs.age

CCT vs.IOP

CCT vs.Kh

CCT vs.Kv

CCT vs. myopicspherical equivalents

CCT vs. Hypermetropicspherical equivalents

Male (n = 276) −0.183(0.002) 0.342(0.000) −0.226(0.000) −0.214(0.000) 0.044(0.502) 0.096(0.349)Female (n = 349) 0.014(0.799) 0.445(0.000) −0.069(0.197) −0.113(0.035) 0.019(0.771) −0.063(0.498)Total (n = 625) −0.073(0.069) 0.397(0.000) −0.139(0.000) −0.147(0.000) 0.028(0.566) −0.007(0.922)

but statistically significant (Pearson correlation test,r = −0.183, p = 0.002) negative correlation betweenage and CCT. Male subjects’ right eye CCT values de-creased 0.4 μm per year (Fig. 1); however, there was nosuch correlation for female subjects (Pearson correlationtest, r = 0.014, p = 0.799).

There were no statistically significant differences be-tween age groups with respect to CCT [analysis ofvariance (ANOVA) test, F = 1.038, p = 0.403] whenage was grouped by decade.

Mean and standard deviation values for IOP for maleand female subjects were 13.2 ± 3.1 and 13.6 ± 2.9mmHg, respectively. IOP and CCT had moderatelysignificant correlations for men and women (Pearsoncorrelation test, r = 0.342, p = 0.000 and r = 0.445,p = 0.000, respectively). An increase of 1 mmHg IOPcorresponded with 3.89 and 5.34 μm increases in CCTvalues for the right eyes of male and female subjects,respectively. Figure 2 shows the relationship betweenIOP and CCT.

There was a weak but statistically significant correla-tion between Kh and Kv, and CCT values for the groupas a whole (Pearson correlation test, r = 0.139, p = 0.000and r = 0.147, p = 0.000, respectively).

There was no statistically significant correlationbetween spherical equivalence and CCT (Spearmancorrelation test: myopia, r = 0.019, p = 0.566;hypermetropia, r = −0.007, p = 0.922). For my-opic patients of ≥6 D and <6 D, there was still

TABLE 2 Mean and standard deviation values of age, CCT, IOP,Kh, and Kv by gender

Male Female pa

Age ± SD (yr) 44.1 ± 16.6 41.0 ± 16.9 0.021CCT ± SD (μm) 552.2 ± 35.9 552.3 ± 35.4 0.962IOP ± SD (mmHg) 13.2 ± 3.1 13.6 ± 2.9 0.068Kh ± SD (dioptry) 43.5 ± 1.6 43.7 ± 1.6 0.133Kv ± SD (dioptry) 42.9 ± 1.7 43.4 ± 2.4 0.015

aStudent’s t test.

no statistically significant difference (Student’s t test,p = 0.532).

With regard to female subjects, 155 (44.4%) werepostmenopausal, although the presence of menopausedid not seem to affect CCT values (Student’s t test,p = 0.45).

When questioned as to systemic disorders, patientsreported having DM (n = 28), HT (n = 48), asthma (n =1), heart disease (n = 2), and hyperlipidemia (n = 25).HT (Student’s t test, p = 0.945), DM (Mann-WhitneyU test, p = 0.294), and hyperlipidemia (Mann-WhitneyU test, p = 0.359) did not seem to affect CCT values.Because the number of patients who reported havingheart disease and asthma was so small, these diseaseswere not included in analyses.

In a multivariate regression model, we investi-gated the relationship of age, sex, DM, HT, lipi-demia, spherical equivalence of refractive error, Kh,and Kv. Only Kv values seemed to affect CCT values(p = 0.039).

DISCUSSIONBecause of both the effect of CCT on IOP

and the increasing popularity of corneal refractivesurgery, researchers have come to understand the im-portance of investigating factors that can potentiallyaffect CCT measurements. Variation in CCT val-ues among different nationalities and ethnicities hasbeen reported.4,16,18,21−23 Moreover, when comparingCCT values, the instruments used for measurementmust be taken into account. For example, ultrasoundpachymetry seems to give higher (∼23–39 μm) valuesthan do other measurement modalities. However, mostinvestigators accept this modality as giving the moreaccurate and reliable results.25,27

In a meta-analysis of 80 studies in which CCTmeasurements were made by ultrasonic pachymetry,Doughty and Zaman reported the mean ±SD CCTto be 544 ± 34 μm.28 In our study, CCT values were

415 Factors Influencing Central Corneal Thickness in a Turkish Population

Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

FIGURE 1 Relationship between age and CCTR for male and female subjects.

FIGURE 2 Relationship between IOPR and CCTR for male and female subjects.


Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

552.2 ± 35.9 and 552.3 ± 35.4 μm for men and women,respectively. In their study of a Hong Kong Chinesepopulation, Cho et al. obtained CCT values of 574 ±33 and 575 ± 31 μm for male and female subjects,respectively.20 In a Japanese population, Nomura et al.found CCT values of 518.3 ± 33.2 and 511.1 ± 32.5μm for men and women, respectively.19 Patel et al. stud-ied Caucasian subjects and found a mean CCT valueof 506 ± 39 μm for the group as a whole.22 All of thesedissimilar mean values point out the variation of CCTamong diverse ethnicities and nationalities.

The Ocular Hypertension Study Group had ac-cepted CCT as an independent risk factor for glau-coma progression.29 Shildkrot et al. emphasized theimportance of having more than one measurementof CCT for glaucoma patients and recommended re-peating not only CCT measurements but also otherfollow-up parameters.30 These recent findings increasedthe importance of CCT, making it of paramount im-portance to study different nationalities’ normativevalues for CCT. With the appreciation of the sig-nificance of CCT, elucidating other factors poten-tially influencing CCT measurements has gained moreattention.

In their study, du Toit et al. emphasized that cornealthickness is greater when a person awakens, as result ofpossible corneal swelling during the night. However, 2hr after the eyes have opened, the cornea returns to itsnormal thickness.31 Our measurements are most likelyfree from the effect of diurnal variation, as they weremade between 9 a.m. and 12 p.m.

In our study, there was no statistically significant dif-ference between CCT values of the right and left eyes,a finding similar to those of other studies.19,20 A fewstudies found CCT values of the left eye to be greaterthan those of the right eye.16,18 In our study, genderdid not seem to affect CCT as it did in several otherstudies.1,15,16,32,33 Brandt et al. found greater CCT val-ues for women than for men.18 In the study of Alsbirket al., CCT readings of Caucasian men and Eskimowomen were found to be greater than those of theirgender counterparts.4

A association between IOP and CCT has been shownin many studies.18−20,34−36 Although Goldmann appla-nation tonometry is the gold standard for IOP mea-surements, noncontact tonometers are being used morefrequently for screening purposes. The relationship ofIOP and CCT is different when IOP measurements areperformed by Goldmann applanation tonometry ver-

sus non-contact tonometry. In our study, an increaseof 1 mmHg IOP corresponded with 3.89 and 5.34 μmfor men and women, respectively. In their study, whichwas performed using noncontact tonometry, Cho et al.found an increase of 4.38 and 3.78 μm per 1 mmHgIOP increase for men and women, respectively.20 Koet al., in comparing the influence of CCT on IOPmeasurements using Goldmann applanation tonome-try and noncontact tonometry, found a range of 0.47–0.98 mmHg differences for every 10-μm change in CCTfor non-contact tonometry.37 They emphasized that theinfluence of CCT on IOP readings is greater with non-contact tonometry than with Goldmann applanationtonometry. We must note here that the relationshipbetween CCT and IOP might also be affected by in-strument variation, ethnicity of study participants, andobserver.

There was no negative correlation between age andCCT for the group as a whole. However, the CCT formen decreased significantly with age. In their study, No-mura et al. found similar results in that only male CCTvalues tended to decrease.19 On the other hand, Choet al. found that CCT decreases with age for the groupas a whole and for female subjects, but not for malesubjects alone.20 While Alsbirk,4 Olsen,31 and Brandt16

supported a negative correlation between CCT andage, studies suggesting that there is no relationship alsoexist.14,29,38,39

There was a slight but significant correlation betweenKh-Kv values and CCT. This finding is similar to that ofGiasson et al., who showed that both of the keratomet-ric values correlated with CCT.40 Conversely, Kiely etal.31 and Howding et al.21 found a correlation of CCTwith either only Kh or Kv, respectively. Still other inves-tigators found no significant relationship between CCTand Kh-Kv.4,20,37

No statistically significant correlation was found be-tween spherical equivalence and CCT, findings sim-ilar to those of several previous studies.1,20 Somestudies41,42 reported the corneas of high myopic(>–9 D) subjects to be thinner, while another study43

found the corneas of hypermetropic subjects to bethicker. When we compared myopic subjects >–6D with those <–6 D, no significant difference wasfound.

All subjects with DM were type II diabetics, andtheir CCT readings were not significantly different fromthose of nondiabetic subjects. Inoue et al.44 and Larssonet al. (45) found no difference between CCT values


Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

among type II diabetic persons, but Larsson et al. em-phasized that type I diabetic persons had significantlyhigher CCT values. Roszkowska et al. measured sig-nificantly thicker corneas in both type I and type IIdiabetics.46 In our study, HT had no influence on CCTreadings, a finding in agreement with results of Brandtet al.18 In that study, in which the investigators foundno significant relationship between HT and CCT, therewas a racial difference in the HT-CCT relationship.18 Inour study, CCT measurements of hyperlipidemic sub-jects did not differ from those of normal subjects; how-ever, we found no other study with which to comparethis result.

Postmenopausal females subjects’ CCT values wereno different from those of premenopausal female sub-jects. Studies of postmenopausal females have been per-formed frequently because of the effects of dry eye orhormone replacement on CCT. However, we were un-able to find any data in the literature for comparison.

In conclusion, correlation analysis revealed thatCCT was correlated with Kh-Kv and IOP but, in mul-tivariate regression analysis, only Kv appeared to influ-ence corneal thickness. There was no significant differ-ence in CCT when correlated with age, sex, sphericalequivalence of refractive status, disease (DM, HT, orhyperlipidemia), menopause, or between right and lefteyes.

REFERENCES[1] Martola E, Baum JL. Central and peripheral corneal thickness. A

clinical study. Arch Ophthalmol. 1968;79:28–30.[2] Hansen FK. A clinical study of the human central corneal thickness.

Acta Ophthalmol (Copenh). 1971;49:82–89.[3] Ehlers N, Hansen FK, Aasved H. Biometric correlations of corneal

thickness. Acta Ophthalmol (Copenh). 1975;53:652–659.[4] Alsbirk PH. Corneal thickness. 1. Age variation, sex differnce and

oculometric correlations. Acta Ophtalmol. 1978;56:95–103.[5] Goldmann H, Schmidt T. Applanation tonometry. Ophthalmologica.

1957;134:221–242.[6] Whitacre MM, Stein R. Sources of error with the Goldmann-type

tonometers. Surv Ophthalmol. 1993;38:1–30.[7] Whitacre MM, Stein R, Hassanein K. The effect of corneal thickness

on applanation tonometry. Am J Ophthalmol. 1993;115:592–596.[8] Ehlers N, Thorklid B, Sperling S. Applanation tonometry and central

corneal thickness. Acta Ophthalmol. 1975;53:34–43.[9] Argus WA. Ocular hypertension and central corneal thickness. Oph-

thalmology. 1995;102:1810–1812.[10] Cennamo G, Rosa N, La Rana A, et al. Non-contact tonometry in

patients that underwent photorefractive keratectomy. Ophthalmo-logica. 1997;211:341–343.

[11] Chatterjee A, Shah S, Bessant DA, et al. Reduction in intraocularpressure after excimer laser photorefractive keratectomy. Ophthal-mology. 1997;104:355–359.

[12] Fournier AV, Podtetenev M, Lemiere J, et al. Intraocular pres-sure change measured by Goldmann tonometry after laser

in situ keratomileusis. J Cataract Refract Surg. 1998;24:905–910.

[13] Zadok D, Tran DB, Twa M, et al. Pneumotonometry versus Goldmanntonometry after laser in situ keratomileusis for myopia. J CataractRefract Surg. 1999;25:1344–1348.

[14] Liu Y, Yanai R, Lu Y, et al. Effect of antiglaucoma drugs on collagengel contraction mediated by human corneal fibroblasts. J Glaucoma.2006;15:255–259.

[15] Lass JH, Eriksson GL, Osterling L, et al. Comparison of the cornealeffects of latanoprost, fixed combination of latanoprost-timolol, tim-olol. Ophthalmology. 2001:108:264–271.

[16] Herse P, Yao W. Variation of corneal thickness with age in youngNew Zealanders. Acta Ophthalmol. 1993;71:360–364.

[17] Swann PG, Yap M, Wong E, et al. Intraocular pressure measurementsand corneal center thickness in Chinese and Caucasian populations.Proceedings of the Ninth Asian-Pacific Optometric Congress. HongKong; 1993:66–69.

[18] Brandt JD, Beiser JA, Kass MA, Gordon MO, and Ocular Hy-pertension Treatment Study (OHTS) Group. Central corneal thick-ness in the Ocular Hypertension Study (OHTS). Ophthalmology.2001;108:1779–1788.

[19] Nomura H, Ando F, Niino N, et al. The relationship between ageand intraocular pressure in a Japanese population: the influence ofcentral corneal thickness. Curr Eye Res. 2002;24:81–85.

[20] Cho P, Lam C. Factors affecting the central corneal thickness of HongKong-Chinese.Curr Eye Res. 1999;18:368–374.

[21] Hovding G. A clinical study of the association between thickness andcurvature of the central cornea. Acta Ophthalmol. 1983;61:461–466.

[22] Patel S, Stevenson RWW. Clinical evaluation of a portable ultrasonicand a Standard optical pachometer. Optom Vis Sci. 1994;17:43–46.

[23] Reinstein DZ, Silverman RH, Rondeau MJ, et al. Epithelial and cornealthickness measurements by high frequency ultrasound digital signalprocessing. Ophthalmology. 1994;101:140–146.

[24] Suzuki S, Oshika T, Oki K, et al. Corneal thickness measure-ments: scanning-slit corneal topography and noncontact specularmicroscopy versus ultrasonic pachymetry. J Cataract Refract Surg.2003;29:1313–1318.

[25] McLaren JW, Nau CB, Erie JC, et al. Corneal thickness measurementby confocal microscopy, ultrasound, and scanning slit methods. AmJ Ophthalmol. 2004;137:1011–1020.

[26] Bovelle R, Kaufmann SC, Thompso SW, et al. Corneal thicknessmeasurements with the Topcon SP-2000P specular microscope andultrasound pachymeter. Arch Ophthalmol. 1999;117:868–870.

[27] Miglior S, Albe E, Guareschi M, et al. Intraobserver and interobserverreproducibility in the evaluation of ultrasonic pachymetry measure-ments of central corneal thickness. Br J Ophthalmol. 2004;88:174–177.

[28] Doughty MJ, Zaman ML. Human corneal thickness and its impacton intraocular pressure measures: A review and meta-analysis ap-proach. Surv Ophthalmol. 200;44:367–408.

[29] Gordon MO, Beiser JA, Brandt JD, et al. The Ocular HypertensionTreatment Study. Baseline factors that predict the onset of primaryopen-angle glaucoma. Arch Ophthalmol. 2002;120:714–720.

[30] Shildkrot Y, Liebmann JM, Fabijanczyk B, et al. Central corneal thick-ness measurement in clinical practice. J Glaucoma. 2005;14:331–336.

[31] du Toit R, Fonn D, Simpson T. Diurnal variation of corneal sensitivityand thickness. Cornea. 2003;22:205–209.

[32] Kiely PM, Carney LG, Smith G. Diurnal variatons of corneal topog-raphy and thickness. Am J Optom Phsyiol Opt. 1982;59:976–982.

[33] Olsen T, Ehlers N. The thickness of the human cornea as determinedby a specular method. Acta Ophthalmol. 1984;62:859–871.

[34] Jordan JF, Joergens S, Dinslange S, et al. Central and paracen-tral corneal pachymetry in patients with normal tension glau-coma and ocular hypertension. Graefes Arch Clin Exp Ophthalmol.2006;244:177–182.


Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

[35] Singh RP, Goldberg I, Graham SL, et al. Central corneal thickness,tonometry, and ocular dimensions in glaucoma and ocular hyper-tension. J Glaucoma. 2001;10:206–210.

[36] Shah S, Chatterjee A, Mathai M, et al. Relationship between cornealthickness and measured intraocular pressure in a general ophthal-mology clinic. Ophthalmology. 1999;106:2154–2160.

[37] Ko YC, Liu CJ, Hsu WM. Varying effects of corneal thickness onintraocular pressure measurement with different tonometers. Eye.2005;19:327–332.

[38] Lowe RF. Central corneal thickness. Ocular correlations in normaleyes and those with primary angle-closure glaucoma. Br J Ophthal-mol. 1969;53:824–826.

[39] Wolfs RCW, Klaver CCW, Vingerling JR, et al. Distribution of centralcorneal thickness and its association with intraocular pressure. AmJ Ophthalmol. 1997;123:767–772.

[40] Giassson C, Forthomme D. Comparison of central corneal thicknessmesurements between optical and ultrasound pachometers. OptomVis Sci. 1992;66:236–241.

[41] Tanaka HM, Mori ES, Maia N, et al. Corneal thicknessin high myopes. Invest Ophthalmol Vis Sci. 1996;37:560.

[42] Nemesure B, Wu SY, Hennis A, et al. Corneal thickness andintraocular pressure in Barbados Eye Studies. Arch Ophthalmol.2003;121:240–244.

[43] Rabsilber TM, Becker KA, Auffart GU. Reliability of Orbscan II to-pography measurements in relation to refractive status. J CataractRefract Surg. 2005;31:1607–1613.

[44] Inoue K, Kato S, Inoue Y, et al. The corneal endothelium and thick-ness in type II diabetes mellitus. Jpn J Ophthalmol. 2002;46:65–69.

[45] Larsson LI, Bourne WM, Pach JM, et al. Structure and function ofthe corneal endothelium in diabetes mellitus type I and type II. ArchOphthalmol. 1996;114:9–14.

[46] Roszkowska AM, Tringali CG, Colosi P, et al. Corneal endotheliumevaluation in type I and type II diabetes mellitus. Ophthalmologica.1999;213:258–261.


Cur

r E

ye R

es D

ownl

oade

d fr

om in

form

ahea

lthca

re.c

om b

y T

ufts

Uni

vers

ity o

n 11

/04/

14Fo

r pe

rson

al u

se o

nly.

factors influencing central corneal thickness in a turkish population

Documents