Mapping the Corneal Sub-Basal Nerve Plexus in Orthokeratology Lens Wear Using in vivo Laser Scanning Confocal Microscopy

Abstract

PURPOSE. This study was designed to map the sub-basal nerve plexus (SBNP) in the cornea of orthokeratology (OK) lens wearers.METHODS. Laser scanning confocal microscopy (LSCM) was performed in vivo on three subjects: a non-lens wearer and two OK lens wearers. Scans were performed on the right eye while the left eye fixated a moving target. A total of 575, 430, and 676 contiguous images of the SBNP were taken from the non-lens wearing and the OK lens wearing subjects, respectively, and used to construct maps of the central to midperipheral SBNP.RESULTS. In the non-lens wearing eye, nerves radiated towards a whorl-like complex centered nasally and inferiorly in an overall pattern consistent with previously reported studies. In the OK lens wearing eyes, this whorl pattern was absent, replaced by a tortuous network of nerve fibers centrally, and thicker curvilinear fibers mid-peripherally, particularly in the nasal, inferior, and temporal regions.CONCLUSIONS. This study maps the corneal SBNP in OK lens wearers and provides compelling evidence that OK lens wear alters the normal SBNP distribution observed in healthy, nonlens wearing eyes. (Invest Ophthalmol Vis Sci.

Short-Term Effects of Overnight Orthokeratology on Corneal Sub-basal Nerve Plexus Morphology and Corneal Sensitivity

“…a downward trend in this factor using the same procedure to assess nerve density although we used an objective tool (NeuronJ) for this purpose. This finding is consistent with observations by Lum et al 14 who described the redistribution of subbasal nerve fibers toward the periphery leaving a sparsely populated central cornea. In line with this finding, the number of fibers in the midperipheral cornea showed an upward trend yet this increase was not significant possibly because our midperipheral measurements were made close to the return zone.…”

“…14 In this study, we examined this living nerve structure in normal corneas and in the corneas of individuals who had worn OK lenses for a shortterm period using objective procedures to assess several variables. Although the size of the corneal area observed by IVCM was smaller than that examined by others, 14,28 the large sample considered here provides evidence that overnight OK lens wear alters some parameters observed in healthy eyes. Moreover, our findings indicate that these changes may vary for different OK lens designs.…”

“…This study reported corneal structural and optical changes. The irreversible thinning of the Bowman layer and subbasal nerve plexus (SBNP) observed by these authors prompted a further study 14 which indicated that wearing OK lenses modifies the normal distribution of subbasal nerves. In addition, it has been confirmed that the tissue redistribution observed during OK treatment leads to increased levels of proinflammatory molecules.…”

Tear Film Osmolarity in Response to Long-Term Orthokeratology Treatment

“…5 The success of OK has been accompanied by a need to address the corneal response to treatment. Recent research efforts have examined changes in corneal morphology and physiology by assessing the effects of treatment on cell density, [6][7][8] thicknesses of the corneal layers, [9][10][11] subbasal nerve plexus (SBNP) distribution, 7,12 and corneal biomechanics. [13][14][15] Some studies have also determined OK effects on tear film components, 16 such as inflammatory mediators.…”

“…[13][14][15] Some studies have also determined OK effects on tear film components, 16 such as inflammatory mediators. 17 These studies conducted both in animals [18][19][20] and humans 6,7,12 have identified corneal changes produced in stromal and epithelial cell density, SBNP thickness and distribution, 7,12 and epithelial layer thickness ans also changes in the levels and distribution of proinflammatory mediators in the tear film samples of OK wearers. 17,21 To date, however, the effects of OK treatment on tear film osmolarity (TFO ) have not yet been examined.…”