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Electronic displays, including laptops, tablets, and smartphones, have dramatically altered the way information is accessed and become significant factors in human daily life. They interfere with the blink rate and increase dry eye symptoms, which lead to more discomfort compared to hard copy while reading. Digital eye strain occurs when an individual suffers from symptoms, or they are exacerbated, while performing a task requiring digital screen viewing. This study assessed the tear film status immediately following reading on a laptop computer screen versus an identical hard copy. Thirty young adults with normal ocular health and reporting no significant symptoms of dry eye (ocular surface disease index (OSDI) score < 13 and non-invasive tear break-up time (NITBUT) > 10 seconds) read a text as hard copy and on a laptop computer screen for 30 min on separate days in a random sequence in a controlled reading experimental condition. The texts were matched in size and contrast and presented at a viewing distance of 40 cm. The NITBUT and strip meniscometry tube tests were administered at baseline and after reading in both conditions. The median baseline NITBUT decreased from 13.0 s to 10.0 s (P < 0.001) after hardcopy reading and to 7.0 (P < 0.001) after reading from a laptop computer screen, with a significant difference between the task medium (P = 0.001). The baseline strip meniscometry tube results decreased from 6.7 mm to 5.0 mm (P < 0.001) after hardcopy reading and to 5.0 mm (P < 0.001) after reading from a laptop computer screen, but there was no significant difference with the task medium (P = 0.085). Reading in both conditions led to tear film instability in terms of the tear film quality and quantity. Additionally, the computer screen has a greater impact on the TBUT compared to hardcopy reading, while these two reading mediums had a similar effect on the tear volume. [ABSTRACT FROM AUTHOR]

Purpose: The possible effects of refractive errors on vestibulo-ocular reflex (VOR) has been a conflicting issue. The aim of this study was to evaluate the effects of induced myopia on VOR using the ocular Vestibular Evoked Myogenic Potential (oVEMP). Methods: In this cross-sectional quasi-experimental study, 35 emmetropic and normal subjects with the mean age of 23.89 ± 3.93 (range, 20-40 years) without any ocular, nervous system, and vestibular disorders, underwent the oVEMP test in the comprehensive rehabilitation center of Mashhad University of Medical Sciences. The oVEMP was performed under five different conditions of testing binocularly, monocularly, and when myopia was induced with the use of spherical lenses of +1.00, +3.00, and +5.00 diopters, respectively. There were 2 to 5 min of rest with closed eyes after each condition to avoid adaptation, fatigue, and any other sources of bias. Mean latencies of oVEMP waves (N1 and P1) and amplitudes of N1-P1 complex were measured. Results: There was no significant difference between the right and left sides (P > 0.05). The induced myopia significantly increased the N1 and P1 latencies using lenses of +1.00, +3.00, and +5.00 diopters but the amplitudes of N1-P1 complex were not influenced by the different amounts of induced myopia. There was no significant difference among the different conditions of induced myopia either (P >0.05). Conclusion: Induced myopia could affect the VOR due to prolonging the latencies of oVEMP waves. However, the amplitudes were not affected and the effects of multiple degrees of induced myopia were not significantly different. [ABSTRACT FROM AUTHOR]

Aim and Background: Due to the relatively high prevalence of binocular vision anomalies, a regular examination including tests for assessment and determination of these anomalies is necessary. The aim of this study was to assess the relationship between near point of convergence (NPC) and near binocular vision symptoms and finding of an NPC cutoff point for symptoms in university students. Materials and Methods: In this cross-sectional study, 124 students of different majors of Zahedan University of Medical Sciences were randomly selected. If they met the inclusion criteria, they were divided into two groups (symptomatic and asymptomatic) according to the convergence insufficiency symptom survey questionnaire. For NPC measurement, a small isolated letter "E" of approximately 20/30 size on a metal rod was used. After data collection, data were analyzed in SPSS.17 software (SPSS for Windows, SPSS Inc., Chicago, IL) using descriptive and analytical statistics, including Mann-Whitney U test and receiver operating characteristic (ROC) curve. Results: The mean NPC findings in the symptomatic and asymptomatic groups were 11.7 ± 5.0 and 8.4 ± 3.4 cm, respectively, with a significant difference between the two groups (P < 0.001). The ROC curve suggests an NPC cutoff point of 9.5 cm for the presence of symptoms with the testing procedures used in this study. Conclusion : The determination of NPC is helpful in the differentiation of symptomatic from asymptomatic subjects.