Strabismus is not a condition in itself but the consequence of an underlying problem. Eye misalignment can be caused by disease, injury, and/or abnormalities in any of the structures and processes involved in visual perception and oculomotor control, from the extraocular muscles and their innervations to the oculomotor and visual processing areas in the brain. A small percentage of all strabismus cases are the consequence of well-described genetic syndromes, acquired insult, or disease affecting the extraocular muscles (EOMs) or their innervations. We will refer to them as strabismus of peripheral origin since their etiology lies in the peripheral nervous system. However, in most strabismus cases, that is comitant, non-restrictive, non-paralytic strabismus, the EOMs and their innervations function properly. These cases are not related to specific syndromes and their precise causes remain poorly understood. They are generally believed to be caused by deficits in the central neural pathways involved in visual perception and oculomotor control. Therefore, we will refer to them as central strabismus. The goal of this narrative review is to discuss the possible causes behind this particular type of eye misalignment and to raise awareness among eyecare professionals about the important role the central nervous system plays in strabismus etiology, and the subsequent implications regarding its treatment. A non-systematic search was conducted using PubMed, Medline, Cochrane, and Google Scholar databases with the keywords “origins,” “causes,” and “etiology” combined with “strabismus.” A snowball approach was also used to find relevant references. In the following article, we will first describe EOM integrity in central strabismus; next, we will address numerous reasons that support the idea of central nervous system (CNS) involvement in the origin of the deviation, followed by listing several possible central causes of the ocular misalignment. Finally, we will discuss the implications CNS etiology has on strabismus treatment.

Contact lens (CL) wearers often suffer from ocular discomfort, which leads to cessation of CL wear. About 30% to 50% of CL wearers complain of dry eye (DE) symptoms. Meibomian gland dysfunction (MGD) is considered the most common cause of evaporative DE. Numerous studies have investigated whether CL wear might affect the meibomian glands. This manuscript reviews studies examining the relationship between CL use and MGD. A PubMed database search was conducted for studies published between 1980-2021 with one or a combination of search terms related to “meibomian gland”, “meibomian gland dysfunction”, “contact lens”, and/or “dry eye”. Of the 115 papers reviewed, 22 articles were identified that examined the association between CL and MGD. Fifteen showed that CL wear affects the morphology and function of meibomian glands (MGs), while seven reported no significant impact of CL wear on MGs. This review provides an overview of these studies, emphasizing the diagnostic tests of MGD and conclusions. The review highlights the need for longitudinal prospective large cohort studies with control non- CL wearers to clarify the ambiguous relationship between MGD and CL wear, with special attention to varying CL material and wear times in order to identify the long-term impact of CLs on MG.

Dynamic visual acuity (DVA) is defined as the ability to discriminate fine details in a moving target. Albeit a growing interest in DVA, there is a lack of standardized, validated instrumentation and procedures for the assessment of this visual function parameter. The aim of the present study was to analyze qualitative construct validity and test–retest reliability of a novel, computer-assisted instrument (DinVA 3.0) for the measurement of DVA. Two different experiments are presented, involving the participation of 33 subjects. The first experiment aimed at testing qualitative construct validity of the DinVA 3.0 by comparing the outcome of a series of trials consisting in different speeds, contrasts and trajectories of the target stimuli with those reported in the literature. The second experiment assessed test–retest reliability by repeating a series of trials at three different time intervals, at maximum target stimuli contrast and either high or low speed configurations. The results of the first experiment gave support to the qualitative construct validity of DinVA 3.0, as the DVA scores were found to be modulated by the speed of the moving target (high speeds yielded lower DVA), contrast (high contrast resulted in better DVA) and trajectory (DVA was better at horizontal rather than oblique trajectories). Test–retest reliability was found to be good, with a small insignificant trend towards improvement with learning. The DinVA 3.0 proved to be a valid and reliable instrument for the assessment of DVA and may be considered a promising tool for both clinicians and researchers.

Previous research shows that playing action video games seems to modify the behavior of eye movements such as eye fixations and saccades. The aim of the current work was to determine the effect of playing action video games on eye movements behavior such as fixations, saccades and pursuits. A systematic research review in PubMed and Scopus databases was conducted to identify articles published between 2010 and 2022 which referred to action video games and eye movements, including fixations, saccades and pursuits. We included those that were experimental and quasi-experimental, comparing at least two groups between action vs. non-action video games players. All the studies included used an eye tracker to study eye movements. A total of 97 scientific articles were found in the databases. After inclusion criteria, thirteen articles (N=13) were analyzed for the present work, of which ten (n=10) had a cross-sectional design, and three (n=3) were randomized intervention studies. Playing regularly or training with action video games is not likely to produce changes in eye movements, based on the literature research analyzed. For future research, more interventional studies, with less gender bias, more sample participants and general consensus on the distinction between the action and non-action video games is needed.