Vergleich zwischen präoperativer Ultraschallpachymetrie und intraoperativer optischer Kohärenzpachymetrie an 513 Augen

Zusammenfassung

Hintergrund: Die in den Excimerlaser integrierte intraoperative optische Kohärenzpachymetrie (OCP) stellt eine Innovation zur kontinuierlichen Kontrolle der Hornhautdicke während der LASIK-Operation dar. Die Zuverlässigkeit und Genauigkeit dieser Methode sollte durch den Vergleich mit der präoperativen Ultraschallpachymetrie (USP) ermittelt werden. Patienten/Materialien und Methoden: Die OCP und USP-Messungen an 513 konsekutiven Augen von LASIK-Patienten wurden ausgewertet. Vor dem Flapschnitt wurden drei zentrale OCP-Messungen im Strahlengang des Excimerlaser-Mikroskops (Technolas, Bausch and Lomb, Rochester, NY) durchgeführt. Diese wurden mit dem Mittelwert von 10 zentralen USP-Messungen aus den Voruntersuchungen (SP-3000, Tomey, Germany) verglichen. Der statistische Vergleich erfolgte mittels Pearson-Regression und Differenzvergleich nach der Bland-Altman-Methode. Ergebnisse:Die mittlere gemessene Hornhautdicke des OCP betrug 523,1 ± 30,5 µm und die des USP betrug 561,2 ± 32,7 µm. Die Messwerte beider Methoden waren signifikant unterschiedlich (T-Test, p < 0,001). Sie korrelierten mit einem hohen Korrelationskoeffizienten von r = 0,891 (Pearson-Korrelation). Der mittlere Unterschied zwischen beiden Messmethoden betrug 37,9 + 14,8 µm. Schlussfolgerungen: Die intraoperative optische OCP-Messung misst eine um ca. 7 % niedrigere Hornhautdicke im Vergleich zur präoperativen akustischen USP-Messung.

Abstract

Background: The aim of this study was to assess the reliability of online optical coherence pachymetry (OCP) integrated into the Technolas excimer platform by comparing the intraoperative OCP corneal thickness measurement with the preoperative standard ultrasound pachymetry (USP). Patients/Materials and Methods: The mean central corneal thickness of 513 consecutive eyes was measured using OCP and USP. Immediately before starting the LASIK procedure, three OCP measurements of the central cornea (OCPonline, Heidelberg Engineering GmbH, Germany) were done under the microscope of the Excimer laser (Technolas, Bausch and Lomb, Rochester, NY). The mean value of 10 central USP measurements (Sp-3000, Tomey, Japan) was obtained during the preoperative assessment of the patients. The comparison of the two methods was done using Pearson regression analysis and the Bland- Altman method. Results: Mean central corneal thickness of the OCP and the USP were 523.1 ± 30.5 µm and 561.2 ± 32.7 µm, respectively. The correlation coefficient was r = 0.891 for the two methods. The mean difference between USP and OCP was 37.9 ± 14.8 µm. Conclusions: The intraoperative OCP gives 7 % smaller measurements compared with the preoperative USP.

Schlüsselwörter

Optische Online Kohärenzpachymetrie - Ultraschallpachymetrie - Hornhautdicke - LASIK - Messunterschiede

Key words

optical coherence pachymetry - ultrasound pachymetry - corneal thickness - LASIK - differences in measurement

Literatur

• 1 Ackermann H. BiAS. für Windows. epsilon, Hochheim, Germany 1989 – 2008; Programmversion 8. 
• 2 Aurich H, Wirbelauer C, Jaroszewski J. et al . Continuous measurement of corneal dehydration with online optical coherence pachymetry.  Cornea. 2006;  25 182-184
• 3 Binder P S. Analysis of ectasia after laser in situ keratomileusis: risk factors.  J Cataract Refract Surg. 2007;  33 1530-1538
• 4 Bland J M, Altman D G. Statistical methods for assessing agreement between two methods of clinical measurement.  Lancet. 1986;  1 307-310
• 5 Bolton C, Herman W. Corneal thickness changes during ultrasound pachymetry for radial keratotomy.  J Refract Surg. 1986;  2 221-222
• 6 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;  44 367-408
• 7 Genth U, Mrochen M, Wälti R. et al . Optical low coherence reflectometry for noncontact measurements of flap thickness during laser in situ keratomileusis.  Ophthalmology. 2002;  109 (5) 973-978
• 8 Haw W W, Manche E E. Latrogenic keratectasia after a deep primary keratotomy during laser in situ keratomileusis.  Am J Ophthalmol. 2001;  132 920-921
• 9 Iskander N G, Anderson Penno E, Peters N T. et al . Accuracy of Orbscan pachymetry measurements and DHG ultrasound pachymetry in primary laser in situ keratomileusis and LASIK enhancement procedures.  J Cataract Refract Surg. 2001;  27 681-685
• 10 Kim H Y, Budenz D L, Lee P S. et al . Comparison of central corneal thickness using anterior segment optical coherence tomography vs ultrasound pachymetry.  Am J Ophthalmol. 2008;  145 228-232
• 11 Kohnen T, Thomala M C, Cichocki M. et al . Internal anterior chamber diameter using optical coherence tomography compared with white-to-white distances using automated measurements.  J Cataract Refract Surg. 2006;  32 1809-1813
• 12 Li H, Leung C K, Wong L. et al . Comparative study of central corneal thickness measurement with slit-lamp optical coherence tomography and visante optical coherence tomography.  Ophthalmology. 2008;  115 796-801 e792
• 13 Li Y, Shekhar R, Huang D. Corneal pachymetry mapping with high-speed optical coherence tomography.  Ophthalmology. 2006;  113 792-799 e792
• 14 Miyata K, Tokunaga T, Nakahara M. et al . Residual bed thickness and corneal forward shift after laser in situ keratomileusis.  J Cataract Refract Surg. 2004;  30 1067-1072
• 15 Neuhann I M, Lege B A, Bauer M. et al . Online optical coherence pachymetry as a safety measure for laser in situ keratomileusis treatment in 1859 cases.  J Cataract Refract Surg. 2008;  34 1273-1279
• 16 Reinstein D Z, Srivannaboon S, Archer T J. et al . Probability model of the inaccuracy of residual stromal thickness prediction to reduce the risk of ectasia after LASIK part II: quantifying population risk.  J Refract Surg. 2006;  22 861-870
• 17 Villasenor R A, Santos V R, Cox K C. et al . Comparison of ultrasonic corneal thickness measurements before and during surgery in the prospective evaluation of radial keratotomy (PERK) study.  Ophthalmology. 1986;  93 327-330
• 18 Jagow von B, Kohnen T. Corneal architecture of femtosecond laser and microkeratome flaps imaged by anterior segment optical coherence tomography.  J Cataract Refract Surg. 2009;  35 35-41
• 19 Wildner K, Muller M, Dawczynski J. et al . Comparison of the corneal thickness as measured by Visante anterior segment OCT versus ultrasound technique.  Klin Monatsbl Augenheilkd. 2007;  224 832-836
• 20 Wirbelauer C, Pham D T. Intraoperative optical coherence pachymetry during laser in situ keratomileusis--first clinical experience.  J Refract Surg. 2003;  19 372-377
• 21 Wirbelauer C, Scholz C, Haberle H. et al . Corneal optical coherence tomography before and after phototherapeutic keratectomy for recurrent epithelial erosions (2).  J Cataract Refract Surg. 2002;  28 1629-1635
• 22 Wirbelauer C, Scholz C, Hoerauf H. et al . Noncontact corneal pachymetry with slit lamp-adapted optical coherence tomography.  Am J Ophthalmol. 2002;  133 444-450
• 23 Wirbelauer C, Pham D T. Continuous monitoring of corneal thickness changes during LASIK with online optical coherence pachymetry.  J Cataract Refract Surg. 2004;  30 2559-2568
• 24 Wirbelauer C, Häberle H, Pham D T. Optische Online-Pachymetrie bei Laser-in-situ-Keratomileusis.  Ophthalmologe. 2004;  101 140-145
• 25 Wong A C, Wong C C, Yuen N S. et al . Correlational study of central corneal thickness measurements on Hong Kong Chinese using optical coherence tomography, Orbscan and ultrasound pachymetry.  Eye. 2002;  16 715-721