Assessment of stereoacuity (3D vision) using TNO random dot stereo acuity chart in medical undergraduate students: A cross-sectional study

The study aimed to estimate the level of stereoacuity in medical undergraduate students, factors associated with reduced stereoacuity, and time taken to interpret plates. Cross-sectional study was done at the Medical College of South Gujarat from April 2021 to June 2022, enrolling 400 consenting students. Detailed ocular history was taken; best corrected visual acuity was assessed for distance and near after cycloplegic refraction for cases with subnormal visual acuity and power of glasses documented. Level of Stereopsis was assessed using TNO random dot stereoacuity chart and time taken to read plates 1 and 5 was recorded. Data were entered and appropriate statistical tests were applied. Out of 400 students, 64.25% had a refractive error. Simple myopia was most prevalent refractive error (43.25%), followed by compound myopic astigmatism (19.5%). Seven students had anisometropic amblyopia and two had strabismic amblyopia. 19.75% cases had subnormal stereopsis. Among them, 10.25% cases had simple myopia, 7.25% had high compound myopic astigmatism, 1.75% had anisometropic amblyopia and 0.5% cases had strabismic amblyopia. Average time taken by emmetrope to read plate 1 and plate 5 was 13.93 ± 14.03 and 19.03 ± 20.66 respectively and for cases with refractive errors, time taken was 17.59 ± 13.95 and 27.83 ± 20.77 respectively. This was statistically significant (P <0.05). Most of the students had good stereoacuity as they were already wearing refractive correction. Commonest cause of subnormal stereopsis ware simple myopia, compound myopic astigmatism and amblyopia. Time taken to read the plates is more for refractive error as compared to emmetropes.