Significance. There are many environmental considerations which may or may not lead to the development of faulty cervical mechanics. The design of near-vision lenses could contribute to the development of such cervical dysfunction and consequently neck pain. Decision-making regarding the proper type of lens prescription seems important for presbyopic individuals. Purpose. To investigate the effect of unifocal and multifocal lenses on cervical posture. Methods. Thirty subjects (18 females and 12 males) participated in the study with an age range from 40 to 64 years. Each subject wore consequently both unifocal and multifocal lenses randomly while reading. Lateral cervical spine X-ray films were taken for each subject during each lens wearing. X-ray films were analyzed with digital software (AutoCAD 2D version 22) to measure segmental angles of the cervical vertebrae (occiput/C1, C1/C2, C2/C3, C3/C4, C4/C5, C5/C6, C6/C7, C3/C7, C0/C3, and occiput/C7). Results. Higher significant extension angles were observed in the segments C0/C7, C1/C2, C5/C6, C6/C7 and C3/C7 (p < 0.05) during multifocal lens wearing, in contrast to higher flexion angles between C3/C4 and C4/C5 (p < 0.05) when wearing unifocal lenses. Conclusion. Multifocal lens spectacles produce increased extension in the cervical vertebrae angles when compared with the use of unifocal lenses.
Keywords: cervical posture; cervical spine; ergonomics; multifocal lenses; presbyopia; unifocal lenses.