Configuration of sub-basal nerve plexus whorl

1. Configuration of sub-basal nerve plexus whorl Stuti Misra Dipika V. Patel Jennifer P. Craig Charles N.J. McGhee Department of Ophthalmology, New Zealand-National Eye Centre, Faculty of Medical & Health Sciences, University of Auckland, New Zealand Authors have no financial interest to declare

2. Background • Traditionally light and electron microscopy have been used to visualise the cornea at a cellular level but these can be only performed ex-vivo. • In vivo confocal microscopy enables the corneal nerve microstructure to be viewed non-invasively. • To date, published data on the human corneal sub-basal nerve plexus configuration is limited to only 4 eyes. Therefore, the extent of variation between individuals or between the eyes of an individual remains unknown.

3. Purpose • The aim was to compare the configuration of the sub-basal nerve plexus in both eyes of four normal subjects.

4. Materials & Methods • Four participants (2 females, 2 males), age range 25 - 33 years • Laser scanning in vivo confocal microscopy (IVCM) was performed on both eyes of each subject on separate days within two weeks • A contiguous montage of IVCM images was prepared using Macromedia Freehand 10 (Macromedia Inc, USA). • Sub-basal nerve density and angle of nerve rotation were analysed using analySIS 3.1 software (Soft Imaging System, Germany)

5. In vivo Confocal Microscopy • Laser scanning confocal microscope HRTII Rostock Corneal Module (Heidelberg Engineering, Germany) • Non-invasive • Corneal layers visible at a cellular level (a) (b) (c) (d) 400µm Confocal image of a normal eye (a) Epithelium (b) Sub-basal nerve plexus (c) Keratocytes and beaded stromal nerves (d) Keratocytes and thicker stromal nerves in mid stroma (a) HRT base unit (b) Corneal module

6. Preparation of a montage  Four confocal images arranged to demonstrate preparation of montage

7. Results 400µm Sub-basal epithelial nerve plexus map, centred on the whorl region

8. Inter-ocular configuration comparison (a) (b) 400µm Whorl pattern of (a) the right eye and (b) the left eye of the same individual demonstrating a similar clockwise pattern in both

9. Results (continued) • Nerve density (whorl region) • Right eyes 39.17 ± 4.95 mm/mm² • Left eyes 41.36 ± 4.19 mm/mm² (t-test, p=0.59) • Whorl orientation - clockwise in both eyes • Nerve rotational angle • Right eyes 61.0 ± 16.2° • Left eyes 59.2 ± 16.4° (t-test, p=0.45)

10. Conclusion / Discussion • This is the first study to report the sub-basal nerve plexus configuration in paired human eyes. • No statistical difference was observed in nerve density and nerve rotation between the eyes. • The sub-basal nerve plexus whorl demonstrated a clockwise configuration in both the right and left eyes in all subjects in this study.

11. Discussion • Interestingly, the sub-basal corneal nerve plexus in both right and left eyes of all individuals in the current study exhibited a whorl pattern with clockwise orientation similar to previous reports of non-paired right and left eyes (Patel and McGhee 2005; Efron 2007). • The comparable nerve plexus configuration in the right and left eyes suggests that the mirror imaging corneal topographic patterns, typically observed between eyes, is not obeyed in respect to corneal innervation.

12. Acknowledgements • University of Auckland Doctoral scholarship • University of Auckland PReSS account • Study participants