Abstract
Purpose::
To evaluate the correlation between central corneal thickness and certain anatomical structures of the posterior segment in normal individuals.
Methods::
Study data was gathered during a community-based glaucoma screening clinic conducted in Montreal, Canada between October 2003 and July 2006. Two hundred and twenty patients were interviewed for demographic data assessment, underwent perimetry by frequency doubling technology (FDT C-20-5), a complete ophthalmic examination, axial length measurement, automated refraction, ultrasonographic corneal pachymetry and one or more imaging techniques- confocal scanning laser ophthalmoscopy (HRTII), optical coherence tomography (OCTIII) and scanning laser polarimetry (GDx VCC).Using data from normal individuals, the correlation between central corneal thickness (CCT) and the following variables was analyzed: disk area, cup area, rim area, cup volume, rim volume, cup/disk area ratio, linear cup/disk ratio, mean cup depth, maximum cup depth, cup shape measure, height variation contour, mean RNFL thickness- imagery parameters from HRTII- cup to disk area ratio, average RNFL thickness, superior average, inferior average- from OCTIII- Nerve Fiber Index (NFI)- from GDx VCC- and other variables including optic nerve appearance using the DDLS classification, intraocular pressure (IOP), axial length, spherical equivalent, sex, age and ethnicity. Statistical analyses included student t-test and Pearson correlation coefficient and were conducted using SPSS software and Excel.
Results::
Eighty-five patients remained, inclusion criteria being normal FDT, IOP and optic nerves. A total of 170 eyes were included in the study, out of which 164 eyes underwent OCTIII, 160 eyes HRTII, and 69 eyes GDx. Preliminary results point to a moderate positive correlation between CCT and IOP (r=0.424, p=0.01 OD and r=0.288 p=0.072 OS) and to a moderate negative correlation between CCT and cup volume (HRTII/OD r=-0.31, p=0.055), between CCT and disk area (HRTII/OS r=-0.351, p=0.031) and between CCT and NFI (GDx/OD r=-0.224, p=0.05).
Conclusions::
In normal individuals, a thin cornea could be associated to a larger disk area, to a fuller excavation, and to a higher NFI; thus it is suggested these imagery parameters can contribute to routine patient evaluation, as does CCT.
Keywords: imaging/image analysis: clinical • optic disc • nerve fiber layer