Ocular surface assessments
corneal hypoaesthesia, trigeminal damage, redness, corneal sensation
CORNEA
The diagnosis of NK was based on the history of trigeminal damage after neurosurgical interventions, which mainly showed ipsilateral corneal hypoaesthesia or anaesthesia. The severity of NK was graded according to the classification described by Dua [All participants underwent best-corrected visual acuity (BCVA) and corneal sensation examinations. The BCVA was converted to the logarithm of the minimum angle of resolution (logMAR) value. Among these values, counting fingers (CF) before the eye was transformed as a logMAR value of 1.85 and light perception (LP) as a logMAR value of 2.7 [Flow chart of study selection processCorneal sensation was evaluated bilaterally using a Cochet-Bonnet aesthesiometer (Luneau Ophthalmlogie, Chartres, France). This test applies different pressures to different regions of the cornea (superior, inferior, nasal, temporal, and central) using a retractable 6 cm monofilament nylon thread with a diameter of 0.12 mm. If a patient did not feel the filament at 60 mm, the filament length was reduced at 5 mm intervals until the filament was felt. The corneal threshold (inverse of sensitivity) is defined by the length of the longest filament necessary to obtain at least two positive responses in three stimulations.Tear film function was evaluated using Keratograph 5 M (Oculus GmbH, Wetzlar, Germany). The first non-invasive tear breakup time (NITBUT-f) and the average non-invasive tear breakup time (NUTBUT-av) were described as the real time between the last complete blink and distortion of the placido rings. The tear meniscus height (TMH) and bulbar redness were also detected using Keratograph 5 M.The LipiView interferometer (TearScience Inc., Morrisville, NC) can automatically evaluate lipid layer thickness (LLT) and partial blinking rate (PBR). A 20-s video documented the interference pattern of the tear film for each eye. We then analysed the interferometric colour units (ICUs) for each eye recorded in the video. One ICU reflects approximately 1 nm of LLT [Corneal nerve measurements were performed using IVCM (Heidelberg Retinal Tomograph, Heidelberg, Germany; HRT II) from the central cornea corresponding to the site of assessment of sensation. Five non-overlapping images of the sub-basal nerve were randomly selected from the IVCM for nerve density calculation. Sub-basal corneal nerve density was defined as the total length of the nerves visible within an image frame (expressed in μm/mm