Purpose:
To determine the subbasal nerve fibre density (NFD) at two different corneal locations and to investigate the relation between them in various refractive surgical techniques.
Methods:
Prospective and longitudinal study done at a territiary eye centre. Twenty eyes undergoing LASIK using mechanical microkeratome (MM), 18 with LASIK with Femtosecond (FS) assisted flap, 20 eyes undergoing PRK, and 20 eyes of age and gender matched controls were included. NFD was measured in the centre and temporal (5 mm away from the centre in non-surgical area) locations using confocal microscope (Heidelberg Retinal Tomography II with RCM, Heidelberg Engineering, Germany) and subsequently analysed with custom made semi-automated image analysis tool at pre, 1week, 1 and 3 months post-operative visits.
Results:
NFD was significantly different between the visits and was found to be lower inall the post operative visits than the pre-op in both the locations and it was same in all the 3 surgical groups. The mean and SD of NFD for all groups at various time points are shown in the Table1.1 below. The mean NFD of all the surgical groups was comparable at pre, 1 week , 1 month and 3 months post-operatively (ANOVA-P>0.05) except FS group which was significantly different from the other groups at 1 month visit (MM-4989: FS-2631: PRK-5359µm/mm2, p<0.001). At 3 months mean NFD was significantly lower in all surgical groups as compared to the control (Control-16365: MM-8500: FS-8461: PRK-10704 µm/mm2). NFD at pre and 3 months operative visits showed significantly higher values in the central location (Pre-16963µm/mm2 ) than temporal (Pre-14732µm/mm2) however, didnot show any difference at other post operative visits.
Conclusions:
Recovery of corneal nerves in FS group was slower at the early post operative visits. Both the centre and temporal NFD reduced grossly due to refractive surgery. This indicates that the peripheral corneal nerves are affected along with the central nerves, irrespective of surgical techniques applied.
Keywords: refractive surgery • imaging/image analysis: clinical • innervation: sensation