Measurements of Dynamic Contour Tonometry After Penetrating Keratoplasty and Epi-LASIK

Seung-Jin Lee; Hyun Soo Lee; Choun-Ki Joo

doi:10.3341/jkos.2009.50.5.749

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Lee, Lee, and Joo: Measurements of Dynamic Contour Tonometry After Penetrating Keratoplasty and Epi-LASIK

Original Article

J Korean Ophthalmol Soc 2009;50(5):749-755.

Published online: 7 September 2009

DOI: https://doi.org/10.3341/jkos.2009.50.5.749

Measurements of Dynamic Contour Tonometry After Penetrating Keratoplasty and Epi-LASIK

Seung-Jin Lee, MD, Hyun Soo Lee, MD, PhD, Choun-Ki Joo, MD, PhD

Department of Ophthalmology and Visual Science, College of Medicine, The Catholic University of Korea, Seoul, Korea

Address reprint requests to Choun-Ki Joo, MD, PhD Department of Ophthalmology, Seoul St. Mary's Hospital #505 Banpo-dong, Seocho-gu, Seoul 137-701, Korea Tel: 82-2-2258-7621, Fax: 82-2-533-3801, E-mail: ckjoo@catholic.ac.kr

Received 13 June 2008 Accepted 9 December 2008

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

To analyze the clinical results of Goldmann applanation tonometry (GAT) and Pascal dynamic contour tonometry (PDCT) and the influences of central corneal thickness and keratometric power in eyes that underwent Epi-LASIK or penetrating keratoplasty.

Methods

Measurements of intraocular pressure by GAT and PDCT as well as keratometric power and central corneal thickness were measured in 45 eyes that underwent penetrating keratopasty and 63 eyes that underwent Epi-LASIK. These parameters were also measured in healthy eyes with no specific disorders to create a control group.

Results

In the keratoplasty group, the PDCT results were significantly higher than the GAT results by 1.22±2.84 mmHg (p=0.006), but neither method showed a significant correlation with CCT or keratometric power. In the Epi-LASIK group, PDCT was higher as 3.45±2.35 mmHg than GAT, and the corrected results of GAT were not different from the results of PDCT. In the control group, GAT was affected by central corneal thickness and keratometric power, but PDCT showed no significant relationship with these two factors.

Conclusions

After Epi-LASIK or penetrating keratoplasty, both of which change CCT and keratometric power, IOP cannot be accurately measured by GAT. In these patients, PDCT may play an important clinical role since it is less affected by corneal properties.

Keywords: Epi-LASIK, Intraocular pressure, Keratoplasty, Pascal dynamic contour tonometry

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Figure 1.

Schematic diagram of Non-applanating contour-matched tip of the Pascal tonometer. When the match is achieved, the sensor tip embeddd in tip measures³⁸

Figure 2.

Difference between PDCT and GAT IOP measurements, plotted against the mean of the two measurements. The measurements obtained by these two techniques were found to be within ±5.61 mm Hg of each other in 95% of cases (PPKP group).

Figure 3.

Effect of CCT on PDCT and GAT in Epi-LASIK group Cross and dotted line represents PDCT result and its estimated regression line according to CCT. PDCT does not correlate with CCT in contrast to GAT. Dotted line (PDCT); IOP=0.005× CCT+13.725 (R²=0.009, p-value=2.479), Solid line (GAT); IOP= 0.029× CCT–0.597 (R²=0.266, p-value=0.000).

Figure 4.

Difference between PDCT and GAT IOP measurements, plotted against the mean of the two measurements. The measurements obtained by these two techniques were found to be within ±4.62 mmHg of each other in 95% of cases (EpiLasik group).

Table 1.

Subject characteristics

	Number of case	s Sex (M:F)	Age	CCT (μm) K	Keratometric power (D)
PPKP group	45	21:24	41.55±18.14	514.80±46.13	44.20±2.04
Epi-LASIK group	63	21:42	29.82±7.26	449.14±44.15	40.00±1.77
Control group	38	17:21	42.26±16.40	545.10±29.24	43.85±1.22

Table 2.

Methods of IOP measurements in PPKP group

Method	GAT	PDCT	Corrected GAT 5 mmHg/70 μm	Corrected GAT 0.027 mmHg/1 μm	Corrected GAT Equation^†
Mean (mm Hg)	15.99±3.59	17.22±3.73	16.36±4.89	16.13±3.81	16.65±3.56
t-test with GAT (p-value)		0.006^*	0.117	0.010^*	0.177

^* p –value<0.05

^† Equation; IOP (real)=IOP (measured by GAT)+(540-CCT)/71+(43-Kvalue)/2.7+0.75 mmHg.

Table 3.

Correlation of methods and Keratometry or CCT (Pearson correlation)

	GAT coefficient (p-value)	PDCT coefficient (p-value)
Keratometry (p-value)		
PPKP	0.260 (0.084)	0.201 (0.186)
Epi-Lasik	0.488 (0.000)^*	0.158 (0.216)
Control	−0.026 (0.875)	−0.100 (0.550)
CCT(p-value)		
PPKP	−0.008 (0.958)	−0.249 (0.098)
Epi-Lasik	0.515 (0.000)^*	0.093 (0.469)
Control	0.376 (0.020)	0.185 (0.265)

^* p-value<0.05.

Table 4.

Mean of IOP measurements in Epi-Lasik group

Method	GAT	PDCT	Corrected GAT 5 mmHg/70 μm	Corrected GAT 0.027 mmHg/1 μm	Corrected GAT CA equation
Mean (mmHg)	12.60±2.51	16.06±2.47	17.64±2.84	14.50±2.15	15.72±2.08
t-test with GAT (p-value)		0.000^*	0.000^*	0.000^*	0.216

^* p-value<0.05.

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