The mechanical complications with silicone hydrogel lenses

Purpose: To report on the incidence and clinical characteristics of mechanicalcomplications observed with silicone hydrogel contact lenses worn on a 29 night continuouswear basis, and to determine risk factors if any for the development of these events.Materials and Methods: Two hundred and ten participants were enrolled in a prospectiveclinical trial to wear silicone hydrogel contact lenses on a 29 night continuous wear schedule.The study was conducted for 6 months. Adverse events seen during the study period werecategorised as infective, inflammatory and mechanical events. The time in lens wear at timeof event, signs and symptoms of the condition were documented and the events monitoreduntil resolution. The severity of the events as an eye disease were rated on a scale of 0-4. Theincidence of adverse events were calculated as number of events per 100 patient eye years.Univariate analysis using ANOVA followed by multivariate analysis using logistic regressionwas performed to determine the risk factors. Significance was set at p<0.05.Results: A single infective event (microbial keratitis), 33 inflammatory and 46 mechanicalevents were observed during the study period. The incidence was 27 and 19 per 100 patienteye years for mechanical and inflammatory events respectively. The mechanical events seenwere 16 events of corneal erosions, 15 events of Superior Epithelial Arcuate Lesions (SEAL)and 16 events of Contact Lens Papillary Conjunctivitis (CLPC) and accounted for anincidence of 9.4, 8.2 and 9.4 events per 100 patient eye years respectively. When only thefirst events were considered, the incidence was 7.0, 7.6 and 8.2 for erosions, SEALs andCLPC respectively. A greater number of mechanical events (26%) were asymptomaticcompared to inflammatory events (3%), however these were mostly SEALs. Events ofCorneal erosions presented as acute events with symptoms of pain and watering and CLPCevents presented with itching, discomfort and blurred vision with lenses. When rated forseverity as an eye disease, inflammatory events were found be more severe (mean: 2.01 ±0.53) compared to mechanical events (mean: 1.48 ± 0.51). Of the mechanical events, amajority of the erosions (70%) and SEALs (62%) were observed in the first month of lenswear. There were more local events of CLPC (75%) than generalised CLPC (25%). Agreater number of mechanical events were observed in males and all the mechanical eventswere managed just by temporary interruption in lens wear. SEALs and erosions are found toresolve much faster compared to CLPC. When all mechanical events were grouped together,reduced bulbar redness at baseline, an increase in palpebral roughness prior to event, cornealstaining in the superior quadrant of the cornea and contamination of lower lid with grampositive bacteria were found to be significant risk factors. Of these, increased palpebralredness prior to the event was significant for events of CLPC , increased extent and depth ofcorneal staining in the superior quadrant was significant for SEALs and gram positivebacteria at lower lid was significant for events of corneal erosions (p