Abstract
BACKGROUND/AIMS—Recent studies have revealed patients with ocular hypertension to have thicker than normal central corneas and those with normal tension glaucoma to have thinner than normal ones, as determined by ultrasonic pachymetry. Since corneal thickness measurements and applanation tonometric estimates of intraocular pressure (IOP) correlate positively, monitoring of the former parameter have served as the basis for adjusting readings pertaining to the latter, with the consequence that many patients have had to be reclassified. With a view to validating these pachymetric studies, the central corneal thickness was determined in patients with normal tension glaucoma, primary open angle glaucoma, pseudoexfoliation glaucoma, or ocular hypertension, as well as that of normal subjects, using optical low coherence reflectometry, which is a new and more precise method than ultrasonic pachymetry. METHODS—34 patients with normal tension glaucoma, 20 with primary open angle glaucoma, 13 with pseudoexfoliation glaucoma, and 12 with ocular hypertension, together with 21 control subjects, were included in this observational, concurrent case-control study. One eye per individual was randomly selected for investigation. IOP was measured by Goldmann applanation tonometry and central corneal thickness by optical low coherence reflectometry. RESULTS—Central corneal thickness was significantly higher (p ⩽0.001) in patients with ocular hypertension than in normal individuals or in subjects with either normal tension glaucoma, primary open angle glaucoma, or pseudoexfoliation glaucoma, there being no significant differences between the latter four groups. Patients with ocular hypertension were also significantly younger (p ⩽0.003) than those within any of the three glaucomatous groups. CONCLUSION—This study confirms that a significant number of patients with ocular hypertension have normal IOPs after the appropriate adjustments have been made for deviations from normal in their central corneal thickness. The accurate measurement of this latter parameter is important not only for individual patient care, in permitting more precise estimations of IOP, but also for clinical studies, in assuring a more reliable classification of subjects.
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Selected References
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- Argus W. A. Ocular hypertension and central corneal thickness. Ophthalmology. 1995 Dec;102(12):1810–1812. doi: 10.1016/s0161-6420(95)30790-7. [DOI] [PubMed] [Google Scholar]
- Böhnke M., Chavanne P., Gianotti R., Salathé R. P. High-precision, high-speed measurement of excimer laser keratectomies with a new optical pachymeter. Ger J Ophthalmol. 1996 Nov;5(6):338–342. [PubMed] [Google Scholar]
- Cennamo G., Rosa N., La Rana A., Bianco S., Sebastiani A. Non-contact tonometry in patients that underwent photorefractive keratectomy. Ophthalmologica. 1997;211(6):341–343. doi: 10.1159/000310825. [DOI] [PubMed] [Google Scholar]
- Chatterjee A., Shah S., Bessant D. A., Naroo S. A., Doyle S. J. Reduction in intraocular pressure after excimer laser photorefractive keratectomy. Correlation with pretreatment myopia. Ophthalmology. 1997 Mar;104(3):355–359. doi: 10.1016/s0161-6420(97)30308-x. [DOI] [PubMed] [Google Scholar]
- Copt R. P., Thomas R., Mermoud A. Corneal thickness in ocular hypertension, primary open-angle glaucoma, and normal tension glaucoma. Arch Ophthalmol. 1999 Jan;117(1):14–16. doi: 10.1001/archopht.117.1.14. [DOI] [PubMed] [Google Scholar]
- Doughty M. J., Zaman M. L. Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach. Surv Ophthalmol. 2000 Mar-Apr;44(5):367–408. doi: 10.1016/s0039-6257(00)00110-7. [DOI] [PubMed] [Google Scholar]
- Ehlers N., Bramsen T., Sperling S. Applanation tonometry and central corneal thickness. Acta Ophthalmol (Copenh) 1975 Mar;53(1):34–43. doi: 10.1111/j.1755-3768.1975.tb01135.x. [DOI] [PubMed] [Google Scholar]
- Emara B., Probst L. E., Tingey D. P., Kennedy D. W., Willms L. J., Machat J. Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis. J Cataract Refract Surg. 1998 Oct;24(10):1320–1325. doi: 10.1016/s0886-3350(98)80222-8. [DOI] [PubMed] [Google Scholar]
- Fournier A. V., Podtetenev M., Lemire J., Thompson P., Duchesne R., Perreault C., Chehade N., Blondeau P. Intraocular pressure change measured by Goldmann tonometry after laser in situ keratomileusis. J Cataract Refract Surg. 1998 Jul;24(7):905–910. doi: 10.1016/s0886-3350(98)80041-2. [DOI] [PubMed] [Google Scholar]
- GOLDMANN H., SCHMIDT T. Uber Applanationstonometrie. Ophthalmologica. 1957 Oct;134(4):221–242. doi: 10.1159/000303213. [DOI] [PubMed] [Google Scholar]
- Gräf M. Zur Bedeutung der Hornhautdicke bei der Non-Contact-Tonometrie. Klin Monbl Augenheilkd. 1991 Sep;199(3):183–186. doi: 10.1055/s-2008-1046068. [DOI] [PubMed] [Google Scholar]
- Hansen F. K., Ehlers N. Elevated tonometer readings caused by a thick cornea. Acta Ophthalmol (Copenh) 1971;49(5):775–778. doi: 10.1111/j.1755-3768.1971.tb08677.x. [DOI] [PubMed] [Google Scholar]
- Herndon L. W., Choudhri S. A., Cox T., Damji K. F., Shields M. B., Allingham R. R. Central corneal thickness in normal, glaucomatous, and ocular hypertensive eyes. Arch Ophthalmol. 1997 Sep;115(9):1137–1141. doi: 10.1001/archopht.1997.01100160307007. [DOI] [PubMed] [Google Scholar]
- Johnson M., Kass M. A., Moses R. A., Grodzki W. J. Increased corneal thickness simulating elevated intraocular pressure. Arch Ophthalmol. 1978 Apr;96(4):664–665. doi: 10.1001/archopht.1978.03910050360012. [DOI] [PubMed] [Google Scholar]
- Lewis R. A. Refractive surgery and the glaucoma patient. Customized corneas under pressure. Ophthalmology. 2000 Sep;107(9):1621–1622. doi: 10.1016/s0161-6420(00)00318-3. [DOI] [PubMed] [Google Scholar]
- Morad Y., Sharon E., Hefetz L., Nemet P. Corneal thickness and curvature in normal-tension glaucoma. Am J Ophthalmol. 1998 Feb;125(2):164–168. doi: 10.1016/s0002-9394(99)80086-5. [DOI] [PubMed] [Google Scholar]
- Shah S., Chatterjee A., Mathai M., Kelly S. P., Kwartz J., Henson D., McLeod D. Relationship between corneal thickness and measured intraocular pressure in a general ophthalmology clinic. Ophthalmology. 1999 Nov;106(11):2154–2160. doi: 10.1016/S0161-6420(99)90498-0. [DOI] [PubMed] [Google Scholar]
- Simon G., Small R. H., Ren Q., Parel J. M. Effect of corneal hydration on Goldmann applanation tonometry and corneal topography. Refract Corneal Surg. 1993 Mar-Apr;9(2):110–117. [PubMed] [Google Scholar]
- Sommer A., Tielsch J. M., Katz J., Quigley H. A., Gottsch J. D., Javitt J., Singh K. Relationship between intraocular pressure and primary open angle glaucoma among white and black Americans. The Baltimore Eye Survey. Arch Ophthalmol. 1991 Aug;109(8):1090–1095. doi: 10.1001/archopht.1991.01080080050026. [DOI] [PubMed] [Google Scholar]
- Stodtmeister R. Applanation tonometry and correction according to corneal thickness. Acta Ophthalmol Scand. 1998 Jun;76(3):319–324. doi: 10.1034/j.1600-0420.1998.760313.x. [DOI] [PubMed] [Google Scholar]
- Tanaka G. H. Corneal pachymetry: a prerequisite for applanation tonometry? Arch Ophthalmol. 1998 Apr;116(4):544–545. [PubMed] [Google Scholar]
- Wheeler N. C., Morantes C. M., Kristensen R. M., Pettit T. H., Lee D. A. Reliability coefficients of three corneal pachymeters. Am J Ophthalmol. 1992 Jun 15;113(6):645–651. doi: 10.1016/s0002-9394(14)74788-9. [DOI] [PubMed] [Google Scholar]
- Whitacre M. M., Stein R. A., Hassanein K. The effect of corneal thickness on applanation tonometry. Am J Ophthalmol. 1993 May 15;115(5):592–596. doi: 10.1016/s0002-9394(14)71455-2. [DOI] [PubMed] [Google Scholar]
- Whitacre M. M., Stein R. Sources of error with use of Goldmann-type tonometers. Surv Ophthalmol. 1993 Jul-Aug;38(1):1–30. doi: 10.1016/0039-6257(93)90053-a. [DOI] [PubMed] [Google Scholar]
- Wolfs R. C., Klaver C. C., Vingerling J. R., Grobbee D. E., Hofman A., de Jong P. T. Distribution of central corneal thickness and its association with intraocular pressure: The Rotterdam Study. Am J Ophthalmol. 1997 Jun;123(6):767–772. doi: 10.1016/s0002-9394(14)71125-0. [DOI] [PubMed] [Google Scholar]
- Zadok D., Tran D. B., Twa M., Carpenter M., Schanzlin D. J. Pneumotonometry versus Goldmann tonometry after laser in situ keratomileusis for myopia. J Cataract Refract Surg. 1999 Oct;25(10):1344–1348. doi: 10.1016/s0886-3350(99)00202-3. [DOI] [PubMed] [Google Scholar]