This study aimed to understand the changes occurring in accommodation and vergence when a myopic patient changes from spectacles to contact lenses.
A prospective, non randomized study was carried out in a group of 25 subjects whose average age was of 23.16 ± 4.41 years. It included a group of habitual myopic contact lens wearers and some fresh wearers as well.
All the subjects underwent a thorough optometric examination. Subsequently a full binocular vision evaluation was performed with spectacles and contact lenses on the same day.
Several visual parameters that characterize the accommodative (accommodative amplitude, accommodative stimulus and accommodative facility) and binocular function (stereo acuity, cover test, horizontal dissociated phoria, vertical dissociated phoria, stimulus AC/A ratio, near point of convergence, negative relative accommodation, positive relative accommodation, positive fusional reserve, negative fusional reserve and vergence facility) were measured with myopic spectacles and contact lenses in these subjects.
The following statistically significant differences were found with the use of spectacles and contact lenses in the accommodative and binocular function: increase in accommodative lag in both the eyes (p < 0.005), increase in accommodative facility (p < 0.005), objective near point of convergence advancing closer to the eye (p < 0.005), increase in negative relative accommodation (p < 0.005) and increase in vergence facility (p < 0.005) with contact lenses in comparison to the spectacles. No statistical differences were found in other accommodative and convergence parameters.
From results obtained in this study, we can conclude that when one changes from spectacles to contact lenses, there is an increase in demand for accommodation and convergence which is in accordance with the theory that myopes who wear contact lenses accommodate more and converge more than spectacle wearers.
Myopia, Contact lenses, Spectacles, Accommodation, Convergence
