ABSTRACT
Soft contact lenses (SCLs) are used for therapeutic purposes and correction of refractive errors. They are also an effective treatment method for different types of corneal diseases.The frequent removal of SCLs used for therapeutic purposes indifferent types of corneal diseases negates epithelization and the recovery process. Consequently, where SCLs removal is not desired and frequent intraocular pressure (IOP)measurements are required, the need arises for IOP measurements to be taken with SCLs in situ. However, measuring IOP with SCLs in situ may affect the IOP measurements gotten.Therefore, this study was toinvestigate the effect of soft contact lenses on IOP measurement. A screening exercise was conducted and subjects suitable for SCL wear, without ocular pathologies were selected. 42 subjects, aged 18-35 years (mean age 22.56 ±2.83) were selected.Their baseline IOP was measured in right eye (OD), first with a Goldmann applanation tonometer (GAT). Their baseline IOP was measured again in both eyes using the Keeler non-contact tonometer (NCT). The 42 subjects were then divided into 7 groups, each group comprised 6 subjects. Groups 1, 2, 3, 4, 5, 6, and 7 subjects wore 0.00D, +3.00DS, +6.00DS, +9.00DS, -3.00DS, -6.00DS and -9.00DS Opticom SCLs on their OD (experimental eye) respectively. IOP was measured with NCT after 30 minutes of wearing these SCLs over the cornea of the OD. The IOP of the naked left eyes of the42 subjectswas also measured with NCT after 30 minutes. This served as an internal control. The data obtained was analysed usingIndependent Sample T-Test at 0.05 level of significance. Results showed that the difference between the mean values of baseline IOP measured with NCT and GAT was statistically insignificant. But measuring IOP through SCLs with different refractive powers using NCT showed that the power of the SCLs was a significant predictor of the change in intraocular pressure readings. The mean difference in IOP values was significantly higher (p =0.007; p=0.000) for the groups with plus SCL powers of +6.00D and +9.00D respectively and significantly lower (p =0.019; p=0.005) for the groups with minus SCL powers of -6.00D and -9.00D of Opticom SCLs respectively.
Keywords: Soft contact lenses, intraocular pressure, applanation tonometry, non-contact tonometry.
