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S. Schneider, T. Simpson, D. Fonn; Observations of Inferior and Central Corneal Subbasal Nerve Orientation Obtained Using Confocal Microscopy. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3859.
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To compare predictions of subbasal corneal nerve orientation in "traditional" radial nerve orientation descriptions to more recent models of nerve distribution, by measuring corneal nerve orientation at the corneal apex and 6 o’clock position.
The right eyes of 10 participants (age 31.3±9.9 years; males=3; females=7) were imaged using confocal microscopy (ConfoScan3, Nidek Technologies, Italy). Images at the corneal apex were taken with the confocal microscope set on full examination mode. In order to control fixation, participants were asked to look at a red LED attached to the chin-rest with a height adjustable rod. Moving the fixation target upwards enabled image capturing at the 6 o’clock position (approx. 3mm above the limbus). Images showing subbasal nerves were imported into image processing software (ImageJ). Orientation of the nerves was obtained with a protractor tool within ImageJ by measuring the angles with respect to the vertical meridian (90°). The absolute difference from 90° was calculated to compensate for angle orientations in either direction. For each participant the mean angle of each position was determined by measuring two different nerves three times, respectively. Statistical significance was determined using a paired t-test.
Analysis showed a statistically significant difference (p<0.001) between the absolute angle orientation (mean±SE) of subbasal nerves at the corneal apex (15.9±2.5° away from the vertical (90°) meridian) and the 6 o’clock position (54.9±6.2° away from the vertical (90°) meridian).
The results support the findings that the subbasal corneal nerve orientation is disordered in the inferior cornea close to the limbus, as reported by Patel and McGhee (IOVS, 46(12), 2005) rather than having the same orientation as at the apex.References:Patel DV, McGhee CN. Mapping the corneal sub-basal nerve plexus in keratoconus by in vivo laser scanning confocal microscopy. Invest Ophthalmol Vis Sci. 2006 Apr:47(4):1348-51.
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