AIM: To analyze changes in the ocular surface parameters of keratoconus after long-term wearing of rigid gas permeable contact lens(RGPCL).

METHODS:Prospective case study. A total of 113 keratoconus patients(213 eyes)fitted with RGPCL in the optometry center of Gansu Provincial Hospital from January 2018 to January 2022 were included. They were divided into three groups according to the severity of keratoconus, including 42 cases(80 eyes)in mild keratoconus group, 54 cases(102 eyes)in moderate keratoconus group and 17 cases(31 eyes)in severe keratoconus group. Furthermore, the non-invasive tear break-up time(NIBUT), non-invasive tear meniscus height(NITMH), red eye index, lipid layer thickness, fluorescent corneal staining, meibomian gland secretory function, Schirmer I test and ocular surface disease index(OSDI)scores were observed by Keratograph analyzer before and after wearing RGPCL for 1 wk, 1, 3, 6, 12 mo, respectively.

RESULTS: There were no statistical significance in the age, NIBUT, NITMH, lipid layer thickness, meibomian gland secretory function and Schirmer I test among the three groups(P>0.05), while there were statistical significance in the sphere, cylinder, spherical equivalent, best corrected visual acuity(BCVA), non-contact intraocular pressure(IOP_NCT), anterior, posterior corneal surface Kmax, corneal surface thickness at the thinnest point, eye redness index, fluorescent corneal staining, and OSDI(P<0.05). In the mild keratoconus group, NIBUT had statistical differences at 3, 6 and 12 mo after wearing RGPCL(P<0.05), NITMH had statistical differences in 6 and 12 mo(P<0.05), the eye redness index, fluorescent corneal staining and OSDI scores had statistical differences in 1 wk and 1 mo(P<0.05), and lipid layer thickness and meibomian gland secretory function had statistical differences in 12 mo(P<0.05). In the moderate keratoconus group, there were statistical differences in NIBUT at 6 and 12 mo after wearing lenses(P<0.05); there were statistical differences in the NITMH, lipid layer thickness and meibomian secretory function at 12 mo after wearing lens(P<0.05); there were statistical differences in the eye redness index at 1 wk, 1 and 3 mo after wearing RGPCL(P<0.05); there were statistical differences in the fluorescent corneal staining at 1 wk after wearing RGPCL(P<0.05); there were statistical differences in the OSDI at 1 wk and 1 mo after wearing RGPCL(P<0.05). In the severe keratoconus group, there were statistical differences in the NIBUT, NITMH and eye redness index at 1 wk, 1, 3, 6 and 12 mo after wearing RGPCL(P<0.05); there were statistical differences in the lipid layer thickness at 6,12 mo after wearing RGPCL(P<0.05); there were statistical differences in the fluorescent corneal staining and OSDI scores at 1 wk, 6 and 12 mo after wearing RGPCL(P<0.05); there were statistical differences in the meibomian secretory function at 6 and 12 mo after wearing RGPCL(P<0.05); and there were statistical differences in the Schirmer I test at 12 mo after wearing RGPCL(P<0.05).

CONCLUSION: Long-term wearing of RGPCL can affect the ocular surface microcirculation in keratoconus patients, thus making differences in patients subjective. However, it has no significant impact on the visual quality of patients. Therefore, long-term wearing of RGPCL is safely to control the progression of keratoconus.