Evaluation of Change in Stereopsis with Age in Normal Eyes

Author(s): Gurvinder Kaur1 , Anu Liza Joy2 , Amruth Lal Yellamelli3

BACKGROUND Stereopsis is the ability to perceive the depth of field based on the disparity of the images formed by the two eyes; in other words, the fusion of the separated images on the Panum's area in order to form binocular single vision. Depth perception is very important in everyday life tasks such as driving, orientation in space while moving (e.g. descending a flight of stairs) and for fine-motor tasks involving hand eye coordination such as threading a needle. By reducing the amount of scanning necessary to extract spatial information, stereopsis facilitates comprehension of complex visual experiences. While stereopsis is a uniquely binocular phenomenon, there are many monocular clues which can provide information on depth including linear perceptive, shadows, texture and gradients. We wanted to study the change and variation of stereopsis with age in normal eyes. METHODS This prospective study was conducted on the participants attending the Outpatient Department of the Department of Ophthalmology of our hospital. A total of 80 subjects (patients/ their relatives) aged between 7 and 80 years, were included in the study. Informed consent was taken from all the participants. Subjects with strabismus, amblyopia, anisometropia (difference of ≥ 2.5D between both eyes), glaucoma, cataract and with age related macular degeneration and patients with history of eye surgery were excluded from the study. Stereopsis was assessed by TNO random dot stereotest (TNO Test). The participants read the test plates at a distance of 40 cm, wearing polaroid spectacles or red-green goggles, under proper illumination and after correction for any refractive error. RESULTS Data was entered in EpiData entry and analysed using EpiData analysis software v. 3.0. Significance was set at p<0.05. It was observed that the stereopsis remained stable till the age of 30 years. Thereafter there was a decline in the median values of stereopsis with increasing age and this decline became statistically significant after the age of 50 years (p<0.0001). CONCLUSIONS In our study, we found that the stereoacuity decreased as the age increased when assessed by TNO test. Stereopsis has an impact on vision related quality of life. Thus knowledge of the underlying population prevalence of physiological reduction of stereopsis with age can help in assessing its contribution to already reducing quality of life with increasing age.