Observation of corneal nerve density for soft contact lens wearers with dry eye symptom using in vivo confcal microscopy

Objective To analyze the relationship between symptoms of dry eye and corneal subepithelial nerve density observed by in vivo confocal microscopy (IVCM).Methods It was a prospective clinical study.Group 1 consisted of 20 soft contact lens (SCL) wearers (40 eyes) with self-reported dryness.Group 2 consisted of 20 asymptomatic wearers (40 eyes).Control group was composed of 17 non-lens wearers (34 eyes).IVCM were used to get corneal subepithelial nerve density on the central cornea,the temporal side and nasal side.Ocular surface disease index (OSDI) dry eye questionnaire was given to each subject.The OSDI dry eye questionnaire score,corneal fluorescein staining score,tear film break up time (BUT) and Schirmer [ test results were recorded.Data were analyzed with a one-way ANOVA.Results Significane differences among three groups were found in BUT (F=9.04,P＜0.01) and corneal fluorescein score (F=3.21,P＜0.05).Schinner Ⅰ test result of group 2 was decreased compared with the control group (P＜0.05).There were no significant differences of corneal nerve density in different directions among the groups.Corneal nerve density on the nasal cornea is statistically significant compared with the central and the temporal cornea (P＜0.05).There was no significant difference in corneal nerve density between the central and the temporal cornea.Conclusion Objective dry eye assessment index of asymptomatic SCL wearers is increased compared with the non-lens wearers,but no difference between symptomatic SCL wearers and with self-reported dryness SCL wearers is found.The dry eye symptoms in SCL wearers are not associated with corneal nerve density.Corneal nerve density of the nasal cornea is less than either the central or the temporal cornea,but there is no significant difference between the central and the temporal comea. Key words: Contact lenses; hydrophilic;  Xerophthalmia;  Confocal microscopy; in vivo;  Nerve density; cornea