Article
Intraocular pressure and corneal thickness : a comparision between applanation tonometry and pneumatic tonometry
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Authors
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N. Domke
- Abteilung für Augenheilkunde, Klinikum Nord-Heidberg, Hamburg
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A. Hager
- Abteilung für Augenheilkunde, Klinikum Nord-Heidberg, Hamburg
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W. Wiegand
- Abteilung für Augenheilkunde, Klinikum Nord-Heidberg, Hamburg
| Published: | September 22, 2004 |
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Outline
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Objective
Corneal thickness and corneal deformation potentiality seem to have an enormous influence on intraocular pressure measurement. Due to the differences in corneal deformation potentiality in either applanation tonometry or pneumatic tonometry, both methods should be compared in the same patient group depending on central corneal thickness.
Methods
In 65 eyes of 35 patients (12 males, 13 females, age 17-89 years, mean 50,5 years) with glaucoma and central corneal thickness between 409μm and 638μm (orbscan-II-pachymetry) intraocular pressure was measured in each eye with pneumatic tonometry (Reichert AT 550) and after 30 minutes with Goldman applanation tonometry.
Results
Applanation tonometry as well as pneumatic tonometry showed a positive correlation between measured intraocular pressure and corneal thickness. The steepness of the line of regression was 0.2mmHg/10μm of corneal thickness in applanation tonometry and 0.4mmHg/10μm of corneal thickness in pneumatic tonometry. The lines of regression crossed at a corneal thickness of 400μm.
Conclusions
Independently of the large differences of the individual pressure measurements between applanation tonometry and pneumatic tonometry we found higher IOP values with pneumatic tonometry in thickner corneas as compared with applanation tonometry. In thinner corneas there was a better correspondence between both the measuring methods.Thus, it seems very likely that corneal rigidity increases with corneal thickness.
