Original Article

Comparison of Central Corneal Thickness Measurements by Ultrasonic Pachymetry and Orbscan II Corneal Topography and Evaluation of Ultrasonic Pachymetry Repeatability

10.4274/tjo.44711

  • Semra Tiryaki Demir
  • Mahmut Odabasi
  • Mehmet Ersin Oba
  • Ayse Burcu Dirim
  • Efe Can
  • Orhan Kara

Received Date: 21.08.2012 Accepted Date: 19.02.2014 Turk J Ophthalmol 2014;44(4):263-267

Objectives:

Comparison of central corneal thickness (CCT) measurements by ultrasonic pachymetry and Orbscan II corneal topography and evaluation of ultrasonic pachymetry repeatability for same observer.

Materials and Methods:

The study included 132, 82, and 80 eyes of 66 patients with primary open-angle glaucoma (POAG), 41 patients with ocular hypertension (OHT), and 40 controls, respectively. All subjects were subjected to routine ophthalmic examination. Orbscan II (Bausch&Lomb) corneal topography and ultrasonic pachymetry (Nidek Ultrasonic Pachymetry UP-1000) were used for measurement of CCT. ANOVA (Turkey test) was used for variable distribution, paired sample t-test was used for repeated measurements, and the analyses were done by SPSS 20.0.

Results:

Mean CCT was 558.9±37.2 µm by ultrasonic pachymetry and 553.4±37 µm by corneal topography. There was a significant difference between the two measurements (p<0.0001). CCT was mean 5.55±8.28 µm thicker by ultrasonic pachymetry compared to corneal topography. There was no significant difference between the two genders (p>0.05). CCT was 555±39.2 µm, 564.3±28.4 µm, and 559.7±41.5 µm by ultrasonic pachymetry in POAG, OHT, and control subjects, respectively; CCT was 550.3±38.3 µm, 558.5±28 µm, and 553.2±42.5 µm by Orbscan II corneal topography in POAG, OHT, and control subjects, respectively. There was a significant linear correlation between Orbscan II corneal topography and ultrasonic pachymetry in CCT measurements (r=0.975, p<0.0001). Repeatability of ultrasonic pachymetry for same observer was (ICC value) 0.990.

Conclusion:

There is a significant correlation between Orbscan II corneal topography and ultrasonic pachymetry in CCT measurements. These two methods of measurements should not be substituted for each other, since ultrasonic pachymetry measures CCT greater than Orbscan II corneal topography. Repeatability of ultrasonic pachymetry for same observer is very high.

Keywords: Central corneal thickness, ultrasonic pachymetry, Orbscan II corneal topography

Full Text (Turkish)