ABSTRACT
The hydrogel contact lenses are efficient in the transmittance of ultraviolent radiation which may be hazardous to the human body. Purpose of study: This study was aimed at the evaluation of spectral transmittance of ultraviolet radiation (i.e. UVC, UVB and UVA) through five brands of hydrogel contact lenses (Freshcon, Freshlook, Polymacon, Opticon and Emcol) with the spectrophotometer. Material and methods: A total of 300 volunteers of myopes from both sexes, aged between 18 - 30 years with mean age +- years were selected from the University of Benin community with the aid of questionnaires. The refractive errors of all the subjects were in six refractive powers i.e. -1.00DS, -2.00DS, -3.00DS, -4.00DS, -5.00DS and -6.00DS and these were sub-divided into 5 study groups that were represented by the 5 brands of contact lenses. The study was carried out within a period of six months, from November, 2021, through April, 2022, in collaboration with three postgraduate research units in the University of Benin: Postgraduate research laboratory of Optometry Department; the Environmental and Toxicology unit of Animal and Environmental Biology (AEB); and the National Centre for Energy Study. The spectral transmittance of ultraviolet radiation (UVR) was compared within the visible spectrum from 200nm to 700nm using a T80 double beam UV-Vis spectrophotometer which was equipped with an integrating sphere. Results: The baseline transmittance (before wear) of the three wavebands (UVC, UVB, UVA) through the five brands showed that UVC had the least mean transmittance of 22.4667± 8.09 through Emcol across the brands. This was statistically significant using ANOVA: F4,175 = 14.790, p=.000; while the UVAhad the highest mean transmittance of 73.7812± 14.44 through Freshcon with 64.0748+9.96. This was also statistically significant using ANOVA: F4,175 = 6.76, p=.000. After wear, UVC had the least mean transmittance with 11.655±3.75 through Emcol. This was statistically significant using ANOVA: F4,175 = 14.790, p=.000; while UVA had the highest mean transmittance with 64.0748± 9.96 through Polymacon. This was also statistically significant using ANOVA: F4,175 = 13.123, p=.000. Comparing the mean transmittance before and after wear UVA had the highest transmittance of 95% through Freshlook while UVC had the least level of transmittance (15%) through Emcol brand. The result also showed that the transmittance decreased from the month of November to February and increased from March to April. There was however slight variation in transmittance across the refractive powers. Thus, UVA is the most transmitted band of UVR while UVC is the least and Polymacon is most efficient in transmittance than the other brands of contact lenses used for the study. Conclusion: Despite the protective covering of the ozone layer, harmful radiations such as UVC and UVB, were transmitted through the eye, hence it is advisable that UV- blockers should be incorporated in all contact lenses to protect the eyes from the harmful effect of these radiations. Contribution to Knowledge: The results of the study showed that Polymacon contact lenses had the highest UVA mean transmittance; while Emcol was lowest in mean transmittance. This showed that the various brands of contact lenses have different capacities for transmittance of UVR. Thus, optometric practioners should endeavour to advise contact lens wearers on the use of good quality products.
Key Words: Transmittance; ultraviolet radiation; visible spectrum; hydrogel contact lenses; spectrophotometer.
