Anterior Biometry After Phakic Intraocular Lenses. Comparison of 3 Different Technologies: Ultrasound Biomicroscopy, Pentacam HR, and Slit lamp OCT Vicente J. Correa-Gomez MD, Guillermo Tapia MD, Oscar Macias Manuel MD, Alejandro Navas Perez MD, Gilberto Islas MD, Tito Ramírez-Luquin MD, Enrique O. Graue-Hernandez MD Institute of Ophthalmology “Fundacion Conde de Valenciana” , Mexico City , Mexico. Department of Cornea and ExternalDiseases. Authors have no financial interest.
Introduction • Ultrasound Biomicroscopy (UBM) has brought about improvements in viewing the anterior chamber, allowing for a high level of spatial resolution and objective measuring capacity of the anterior chamber structures • UBM is a contact exploration technique with an immersion system which requires patients to be in recumbent position. • Non-contact imaging technologies like OCT and Pentacam are available to anterior chamber biometry • These devices are becoming more popular as they are more comfortable for the patient and decrease the risk of corneal abrasions or infections due to direct corneal contact.
Optical coherence tomography (OCT) is a non-contact high resolution (2 to 20 μm) imaging technology that provides detailed cross-sectional images (tomography) of internal structures. • Optical coherence tomography (OCT) is a non-contact high resolution (2 to 20 μm) imaging technology that provides detailed cross-sectional images (tomography) of internal structures. • The Pentacam is a Scheimpflug camera based imaging system, which rotates about the eye and collects 50 scans of the anterior chamber in less than 2 seconds.
Purpose • To evaluate and compare three different instruments in the biometry of the anterior chamber and after Implantable Collamer Lens (ICL) .
Methods • We analyzed 9 eyes from five patients. • After surgery values for central anterior chamber depth (ACD), vault, and pachymetry were obtained with ultrasound biomicroscopy , Pentacam HR (Pcam, Oculus) and slit lamp optical coherence tomography (SL-OCT, Heidelberg engineering). • Results were analysed by paired T-test , one-way ANOVA, and Pearson correlation coefficient
SL-OCT • PENTACAM • UBM
Differences in ACD and Vault measured by OCT and Pentacam Vs UBM were statistically significant (p< 0.05). • One-way ANOVA revealed that the differences in pachymetry, and anterior chamber depth as measured with AC-OCT and Pcam were statiscally signficant when compared to UBM (p< 0.05). • Pearson correlation coefficient was > 0.85 with all tests.
Conclusions • Excellent correlation between these 3 instruments was observed. • OCT & Pentacam had similar results Vs UBM. • The measurements with UBM were smaller in comparison with pentacam and OCT, therefore they offer a range of greater security. • However in order to increase the safety of ICL phakic IOL implantation, ACD and vault safety values need to be standardized to each equipment.
References • JL Branco, Yan Li, D Huang, MD . Clinical and research applications of anterior segment optical coherence tomography – a review Clin Experiment Ophthalmol. 2009 January ; 37(1): 81–89. • Muriël Doors et al. Comparison of central corneal thickness and anterior chamber depth measurements using three imaging technologies in normal eyes and after phakic intraocular lens implantation. Graefes Arch Clin Exp Ophthalmol (2009) 247:1139–1146 • Lara-Medina et al. Exploration of the anterior segment by optical coherence tomography . Arch Soc Esp Oftalmol. 2006; 81: 647-652 • J. Woodmass, G. Rocha. A comparison of Scheimpflug imaging simulated and Holladay equivalent keratometry values with partial coherence interferometry keratometry measurements in phakic eyes. Can J Ophthalmol 2009;44:700–4