Illumination levels and eyestrain in workers from a pharmaceutical company in Mexico City

Introduction
There are few studies about eyestrain in the Mexican and international pharmaceutical industry. Eyestrain or asthenopia is a functional, reversible change, due to visual overexertion with symptoms like as visual discomfort and disturbances. At work eyestrain may be related to poor lighting, improper contrast, and bad position design. This study evaluates the association between eyestrain symptoms and levels of lighting in the conditioning area in a pharmaceutical company from Mexico City.

Methods
We performed a cross-sectional study of 34 workers from the conditioning area. Lighting levels were measured at the workplaces. Workers vision was examined and information about sex, age, medical history and seniority was collected. Data was analyzed using the SPSS-19 software and the Odds Ratio of having visual complains in low lighting areas was calculated.

Results
In some linews from the conditioning department had low light levels lower than 200 lux, and the low light levels did not influence the reflection factor as were within normal limits. Workers in those positions with a low light level workers had a significant increase risk of having eyestrain symptoms such as eyelid twitch (OR=22.16), headaches (OR=12.8), eye redness (OR=10.2), and itching (OR=12.7). The most common problem of refraction in this population was astigmatism.

Discussion
Visual problems such as astigmatism and myopia, nearsightedness, compound myopic astigmatism, with inadequate lighting can alter the accommodative state of the eye, thus producing asthenopia or eyestrain. Based on this study results we can conclude that workers eyestrain symptoms in the conditioning department is related to low levels of illumination. If this situation neither is nor solved it may impact in workers health and company´s productivity.