The Ophthalmic Factors Affecting 3D Asthenopia

Seung-Hyun Kim

Background
Watching 3D image is known to induce more asthenopic symptoms than watching conventional 2D image. If the ophthalmic factors which cause 3D asthenopia are found, we can predict the occurrence of problems and guide people with the ophthalmic factors to watch 3D images adequately, and aid them watch 3D image more comfortably by managing ophthalmic factors.

Methods
One hundred-fifteen volunteers, aged 18 to 55 years and recruited from 3 different centers are enrolled in this study. The 3D images were shown with 3D HDTV for 90 minutes. According to survey, which was performed with questionnaire after watching 3D HDTV, subjects with asthenopic symptoms assigned to asthenopia group (14 subjects). Among subjects without any symptom, subjects recruited from one center were assigned to control group (22 subjects). The ophthalmic factors including visual acuity, refractive errors, interpupillary distance (IPD), intraocular pressure (IOP), tear break-up time (BUT), near point of accommodation (NPA), angle of strabismus, stereoacuity and retinal abnormality were evaluated and compared between both groups.

Results
Mean age and gender distribution was not different between both groups. All subjects showed normal best corrected visual acuity, and no one showed retinal abnormality. Refractive error, stereoacuity at near and distant, IPD, BUT, IOP were not a significant ophthalmic factor related to 3D asthenopia. Six subjects in asthenopia group had exophoria, and 1 subject had constant exotropia in control group, who had not noticed strabismus before. The presence of strabismus was significantly different (P=0.008). All subject in both groups showed normal stereopsis except exotropic subject. The NPA was not different between both groups. However, when compared with age matched mean value, lack of accommodative power was observed in 6 subjects of astenopia group, and in 1 of control group, which was significantly different (P=0.008).

Conclusion
The subjects with exophoria or reduced accommodative ability compared with the average value of the same age group are prone to have 3D asthenopia. 3D TV should be watched with a caution for these group of people.