using rigid gas permeable (rgp) hard contact lenses in improvement of involuntary eye movements and visual function in patients with hyperopic astigmatism and congenital nystagmus

purpose: to determine the effect of using rigid gas permeable (rgp) contact lenses in improvement of involuntary eye movements and visual functions in hyperopic astigmatism patients with congenital nystagmus. methods: this prospective interventional case series study was conducted on patients with congenital nystagmus and hyperopia equal or more than +0.5 d and astigmatism more than -1 d, who were referred to our clinic over a period of 2 years. all ophthalmological exams including visual acuity, contrast sensitivity and video nystagmography were performed for all of the patients before and after contact lens fitting and were compared with each other. results: in this study 32 eyes of 16 patients were entered with mean age of 18.6±4.9 years. in these cases, mean sphere was 2.45±2.44 (range +0.5 to +7.5), spherical equivalent of refraction was +1.5±2.35 (range -1 to +6.25) and mean astigmatism was -1.90±0.83 (range -1 to -4). the level of visual acuity changes in log mar improved monocularly from 0.56±0.23 to 0.51±0.23 and binocularly from 0.54±0.25 to 0.48±0.24 which was statistically significant (p=0.007).improvement of contrast sensitivity were statistically significant in low (p=0.02) and intermediate (p< 0.001) frequencies but not in high frequencies (p=0.7). frequency, amplitude and intensity of nystagmus were decreased significantly after contact lens usage (p< 0.001). conclusion: using rgp contact lenses in patients with congenital nystagmus increase monoocular and binocular vision. also contrast sensitivity and motor indices of nystagmus (frequency, amplitude and intensity) were significantly improved after contact using lens.