Purpose:
Evaluation of ocular surface integrity involves the grading of the corneal staining with sodium fluorescein and of the conjunctival staining with lissamine green. The data is usually reported as the severity of the staining observed without information as to its geographic distribution. Increased staining is postulated to be associated with contact lens wear. The aim of the current investigation was to quantify in a large population of non wearers and contact lens wearers who attended OTG R&C clinic the prevalence and geographic distribution of staining and its association with contact lens wear.
Methods:
The study population of 270 consecutive patients (116 Male, 154 Female) age 18 to 66 years included non contact lens wearers (NonCL)(n=128) and contact lens wearers (CL)(n=142). Conjunctival staining with lissamine green dye was rated subjectively on a 5 point scale (0= None 4 = Severe) for each quadrant independently. Corneal staining using sodium fluorescein dye was reported on a 10 point scale (0= None, 1-3 = Micropunctate, 4-5 = Macropunctate, 7-9= patch) in each of the five corneal zones.
Results:
The results obtained showed that:i. Corneal staining was more frequent in CL (Prevalence: 79%) than in NonCL (Prevalence: 54%) (p<0.001).ii. For the NonCL group, corneal staining was present in less than 18% of eyes in all zones except in the inferior (Prevalence: 45%).iii. For the CL group, corneal staining in the central, nasal and temporal zones was similar and present in approximately 20% of cases. Staining was maximal in the inferior (Prevalence: 56%) and superior zones (Prevalence: 47%).iv. Conjunctival staining prevalence was similar to that of corneal staining for both groups and again greater in the CL (73%) than NonCL ( 51%) group (p<0.001)v. Conjunctival staining was lowest in the superior (CL 5% NonCL 3%) and inferior quadrants (CL 13% NonCL 7%) and significantly greater in the temporal (CL 47% NonCL 28%) and nasal (CL 67% NonCL 43%) quadrants.vi. For the CL group, there was no correlation between corneal and conjunctival staining (p=0.102). For the NonCL group, the correlation between corneal and conjunctival was of low clinical predictability (p <0.001 r2 = 0.077).
Conclusions:
The study confirmed the greater prevalence of both corneal and conjunctival staining in contact lens wearers than non wearers. Further it revealed a different geographic distribution, maximal staining occurrence being observed in the inferior zone for the cornea and in both the temporal and nasal regions for the conjunctiva.
Keywords: cornea: clinical science • contact lens • conjunctiva