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Helen A. Swarbrick, Renee Gunn, Meesha Babhoota, Blanka Golebiowski, Edward Lum; The Effects Of Mechanical Force On Corneal Sensitivity In Short Term Contact Lens Wear. Invest. Ophthalmol. Vis. Sci. 2012;53(14):4731.
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© ARVO (1962-2015); The Authors (2016-present)
The relative contributions of hypoxia and mechanical force to changes in corneal sensitivity during contact lens wear are currently unclear. This study investigates the influence of mechanical force exerted by contact lenses on central corneal sensitivity in the short term.
Eighteen subjects (7M, 11F, age 23.6±4.8 yrs) were recruited for this study. Subjects wore either a silicone hydrogel (SCL), rigid (RGP) or orthokeratology (OK) contact lens. Lenses were matched in Dk/t (46 ISO units) but assumed to exert different levels of mechanical force on the corneal surface. Lenses were worn for a single overnight wear (8 hrs) in the right eye only. Data were collected at baseline (BL), and after each overnight lens wear by an investigator masked to the lens type, approximately 3 hrs after waking and lens removal. Subjects wore all lens types in a randomized order with a minimum wash out period of 3 days between overnight wear sessions. Central corneal sensitivity thresholds were obtained using two instruments; Cochet-Bonnet (COBO) and non-contact corneal aesthesiometers (NCCA). Corneal topographic changes (apical radius, asphericity, refractive power) were measured using the Medmont E300 corneal topographer. ANOVA and post hoc paired t-tests were used to compare changes from baseline and between treatment groups.
There were significant differences in topographic change from baseline between the lens types for apical radius (ANOVA, p<0.001), asphericity (ANOVA, p<0.001), and refractive power (ANOVA, p<0.05). There were also significant differences in corneal sensitivity between lens types using the COBO (BL: 5.69±0.60cm, SCL: 5.58±0.67cm, RGP: 5.64±0.74cm, OK: 5.00±1.16cm; ANOVA, p<0.05). A significant decrease in threshold from BL was only seen in the OK lenses (post hoc t-test, p<0.05). There was no difference in sensitivity thresholds between BL and any lens type using the NCCA (ANOVA, p>0.05).
Central corneal sensitivity is reduced after a single overnight wear of OK lenses as measured using the COBO aesthesiometer. This suggests that the mechanical force exerted by contact lenses may be a key influence on corneal sensitivity. It also indicates that COBO and NCCA instruments may measure different aspects of corneal sensitivity.
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