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Human gamma-D crystallin (HGD) is a major constituent of the eye lens. Aggregation of HGD contributes to cataract formation, the leading cause of blindness worldwide. It is unique in its longevity, maintaining its folded and soluble state for 50-60 years. One outstanding question is the structural basis of this longevity despite oxidative aging and environmental stressors including ultraviolet radiation (UV). Here we present crystallographic structures evidencing a UV-induced crystallin redox switch mechanism. The room-temperature serial synchrotron crystallographic (SSX) structure of freshly prepared crystallin mutant (R36S) shows no post-translational modifications. After aging for nine months in the absence of light, a thiol-adduct (dithiothreitol) modifying surface cysteines is observed by low-dose SSX. This is shown to be UV-labile in an acutely light-exposed structure. This suggests a mechanism by which a major source of crystallin damage, UV, may also act as a rescuing factor in a finely balanced redox system. Understanding the stability of the eye lens protein human gamma-D crystallin (HGD) is essential to developing tools to prevent the formation of cataracts, however, structural investigations of the response of HGD to ultraviolet radiation are lacking. Here, the authors use continuous illumination serial crystallography to directly probe the mechanism of R36S HGD in response to ultraviolet radiation damage. [ABSTRACT FROM AUTHOR]

Digital eye strain (DES) is an entity encompassing visual and ocular symptoms arising due to the prolonged use of digital electronic devices. It is characterized by dry eyes, itching, foreign body sensation, watering, blurring of vision, and headache. Non-ocular symptoms associated with eye strain include stiff neck, general fatigue, headache, and backache. A variable prevalence ranging from 5 to 65% has been reported in the pre-COVID-19 era. With lockdown restrictions during the pandemic, outdoor activities were restricted for all age groups, and digital learning became the norm for almost 2 years. While the DES prevalence amongst children alone rose to 50–60%, the symptoms expanded to include recent onset esotropia and vergence abnormalities as part of the DES spectrum. New-onset myopia and increased progression of existing myopia became one of the most significant ocular health complications. Management options for DES include following correct ergonomics like reducing average daily screen time, frequent blinking, improving lighting, minimizing glare, taking regular breaks from the screen, changing focus to distance object intermittently, and following the 20-20-20 rule to reduce eye strain. Innovations in this field include high-resolution screens, inbuilt antireflective coating, matte-finished glass, edge-to-edge displays, and image smoothening graphic effects. Further explorations should focus on recommendations for digital screen optimization, novel spectacle lens technologies, and inbuilt filters to optimize visual comfort. A paradigm shift is required in our understanding of looking at DES from an etiological perspective, so that customized solutions can be explored accordingly. The aim of this review article is to understand the pathophysiology of varied manifestations, predisposing risk factors, varied management options, along with changing patterns of DES prevalence post COVID-19. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the effectiveness of an ergonomic intervention program based on the PRECEDE–PROCEED model in terms of improving exposure risks and work-related health problems in emergency medical dispatchers. Methods: This quasi-experimental study used an interrupted time series design. Participants were 55 employees working in an Emergency Medical Communications Center in Iran. The intervention program was based on the PRECEDE–PROCEED model and included five face-to-face training sessions and installing auxiliary equipment according to best ergonomic principles. Direct observations of the emergency medical dispatchers' working postures using the Rapid Office Strain Assessment and a survey which included a modified Nordic Questionnaire, Work Ability Score, Visual Fatigue Questionnaire, and a Behavioral Factors Questionnaire were used at three time points: baseline, 1 month post-intervention, and 3 months post-intervention. Results: The modified Nordic Questionnaire showed significant reductions in pain intensity scores for neck, lower back, knee and ankle after the ergonomic intervention program. In addition, there were considerable post-training improvements in behavioral factors (knowledge and enabling factors) and working postures. No significant changes were observed in Work Ability Scores, or visual symptoms. Conclusions: An ergonomic intervention program based on a systematic framework such as the PRECEDE–PROCEED model and on-site interventions can be effective in improving and enhancing the working conditions of emergency medical dispatchers. Therefore, it is suggested that ergonomic interventions be implemented based on standard and valid behavioral change models such as PRECEDE–PROCEED model in other work environments in which musculoskeletal pain and digital eye strain are common. [ABSTRACT FROM AUTHOR]

The aim of this retrospective chart review study was to evaluate the 5-year trend of ocular surface examination results in participants who visited the eye clinic from 2015 to 2019, underwent corneal and lacrimal examinations, refraction, and intra-ocular pressure measurements, and reported six dry eye-related symptoms. A total of 1468 patients were analyzed. Tear break-up time (BUT) decreased continuously for five consecutive years: 4.76 ± 1.84 s in 2015, 4.57 ± 1.70 s in 2016 (p = 0.999, vs 2015), 4.35 ± 2.06 s in 2017 (p = 0.662), 3.83 ± 2.18 s in 2018 (p < 0.001), and 3.63 ± 2.10 s in 2019 (p < 0.001). The decrease of BUT was more prominent in women than men (p < 0.001) and the correlation coefficient between calendar year and BUT was greater in women than men (p = 0.002). Schirmer test value, strip tear meniscometry value, and corneal staining score did not exhibit significant changes. Prevalence of blurring, photophobia, and pain increased toward 2019 among symptoms surveyed (eye fatigue, blurring, photophobia, dryness, irritation, and pain) and regression analysis indicated blurring (p < 0.001), photophobia (p < 0.001), and pain (p < 0.001) were correlated with BUT. In conclusion, BUT decreased continuously for five consecutive years from 2015 to 2019 and was associated with dry-eye related symptoms. [ABSTRACT FROM AUTHOR]

Augmented reality (AR) devices, as smart glasses, enable users to see both the real world and virtual images simultaneously, contributing to an immersive experience in interactions and visualization. Recently, to reduce the size and weight of smart glasses, waveguides incorporating holographic optical elements in the form of advanced grating structures have been utilized to provide light-weight solutions instead of bulky helmet-type headsets. However current waveguide displays often have limited display resolution, efficiency and field-of-view, with complex multi-step fabrication processes of lower yield. In addition, current AR displays often have vergence-accommodation conflict in the augmented and virtual images, resulting in focusing-visual fatigue and eye strain. Here we report metasurface optical elements designed and experimentally implemented as a platform solution to overcome these limitations. Through careful dispersion control in the excited propagation and diffraction modes, we design and implement our high-resolution full-color prototype, via the combination of analytical–numerical simulations, nanofabrication and device measurements. With the metasurface control of the light propagation, our prototype device achieves a 1080-pixel resolution, a field-of-view more than 40°, an overall input–output efficiency more than 1%, and addresses the vergence-accommodation conflict through our focal-free implementation. Furthermore, our AR waveguide is achieved in a single metasurface-waveguide layer, aiding the scalability and process yield control. [ABSTRACT FROM AUTHOR]

Undetected refractive errors (REs) in children can lead to irreversible vision loss. This study aimed to show the proportions of REs in French children using cycloplegic refraction. Multicentre cross-sectional retrospective study including children with cycloplegic refraction and without associated ocular conditions from 2015 to 2018 in French eye clinics. The following data were collected: age, symptoms of eye strain, best-corrected visual acuity (BCVA), cycloplegic refraction. The analysis included 48,163 children (mean age: 7.75 years, range: 2 to 12 years). The proportion of each RE was as follows: emmetropia (− 0.50 < Spherical Equivalent (SE) ≤ + 2.0; 58.3%), hyperopia (+ 2.0 < SE ≤ +5; 17.2%), myopia (− 6 ≤ SE ≤ − 0.50; 15.5%), high myopia (SE < − 6; 0.5%), high hyperopia (SE > + 5; 3.6%), mixed astigmatism (4.9%). Anisometropia (SE difference ≥ 1.5) was found in 5.0%. Functional amblyopia in children attending primary school (aged over 6 years) was encountered in 2.7%. Symptoms of eye strain were frequent (70%) but not specific to any RE. REs are frequently found in French children and may remain undetected in the absence of symptoms of eye strain. Few studies have investigated REs in children using cycloplegic refraction, which has been shown to be the gold standard for RE assessment. [ABSTRACT FROM AUTHOR]

Introduction: Dry eye is a multifactorial condition of the eye caused by insufficient tear production and imbalance in tear composition leading to faster evaporation of tear fluid. It is also associated with inflammation that often leads to ocular surface damage. Symptoms of dry eyes include itchiness, soreness, red eyes, a burning sensation, eye fatigue and blurred vision. The objective of this study was to evaluate the efficacy and safety of our multi-ingredient supplement in subjects with dry eye syndrome (DES). Methods: We recruited 60 subjects with mild to moderate DES who were randomized in a 1:1 ratio in a single-center study to receive LCD (lutein 20 mg, zeaxanthin 4 mg, curcumin 200 mg curcuminoids, vitamin D3 600 IU) or placebo (soybean oil) capsules for 8 weeks. The primary outcomes evaluated were changes in tear volume by Schirmer's test and ocular symptoms by the Ocular Surface Disease Index (OSDI); secondary outcomes included evaluation of changes in Standard Patient Evaluation of Eye Dryness (SPEED) questionnaire, tear film break-up time (TBUT), corneal and conjunctival staining, tear osmolarity, matrix metalloproteinase-9 (MMP-9), artificial tear use and safety assessments. The outcomes were compared between the LCD and placebo groups at baseline and day 56 of supplementation. Results: Fifty-nine subjects, 30 from LCD and 29 from placebo group, completed the study. The LCD group showed significant improvements (P < 0.0001) for Schirmer's test, OSDI, TBUT, SPEED, ocular staining scores, tear osmolarity (P = 0.0005), MMP-9 (P = 0.0017) and reduced artificial tear use (P = 0.0004) and its frequency of use (P < 0.0001) in subjects compared to placebo from baseline to day 56. No safety issues were observed in the study. Conclusion: The LCD supplement showed significant improvements in the production, stability and quality of tears by reducing ocular surface damage and tear inflammation and can be used as an adjuvant to artificial tears in subjects with DES. Trial Registration: Clinical Trials Registry of India (http://ctri.nic.in/) identifier: CTRI/2021/01/030493. [ABSTRACT FROM AUTHOR]

Only a few studies in the literature have focused on the effects of age on fatigue susceptibility and hand operation performance in virtual environments, and even less research has been carried out focusing on older adults. This study aimed to assess the hand movement performance in a virtual environment with two group measures, including visual fatigue and depth perception. A total of 10 adults (5 young adults and 5 older adults) participated in this study. This study was conducted in the following order: pre-CFF measurement, performance of a Fitts' Law task with stereoscopic viewing, post-CFF measurement every 10 min (during task), and recording of task movement time and error rate after each condition of the task. This study found significant effects of age and task index of difficulty on hand movement. Compared to the older adults, the young adults appeared to have better hand movement performance. Regarding eye fatigue, eye fatigue was significantly higher at binocular parallax of 9 cm than at 6 cm and 3 cm. Surprisingly, age had a significant effect on hand movement performance but not on visual fatigue. This study suggests that the operation time should be less than 20 min and that parallax should be 6 cm (visual angle = 1.38 degrees) to prevent visual fatigue when movement tasks are performed in a virtual environment. These data highlight the potential for age-related differences in hand movement performance during the performance of tasks in which fast and accurate selection are required in combination with the manipulation of 3D objects in a virtual environment, and the study provides directions for further exploration. [ABSTRACT FROM AUTHOR]

Advances in information technologies have resulted in people spending increasing amounts of time staring at electronic screens. Long-term use of computers, mobile phones, and tablets can cause eye soreness and fatigue, but can also cause more serious conditions including myopia, cataracts, and glaucoma. This study assesses changes in brain wave activity detected by eight electrodes targeting different brain regions to identify and assess the brain wave patterns in the regions associated with visual fatigue under various visual presentation methods. Furthermore, linear discriminant analysis and Min–Max scaling techniques are applied to develop a visual fatigue assessment model to quantify visual fatigue. Finally, experiments are run to assess the impact of screen size (smartphone, tablet, computer) and visual presentation mode (2D, 3D, AR, VR) on visual fatigue. This study finds that (1) the brain wave features which influence the reaction to 2D and 3D imaging are the delta and theta waves at the prefrontal Fp1 and Fp2 poles. When viewing AR images, the alpha bands at the O1 and O2 poles of the occipital lobe show a relatively clear impact, while the delta and theta waves at the C3 pole in the left center area are associated with VR images; (2) larger screens cause greater visual fatigue, indicating that excessive visual stimulation will increase visual loading and thus produce greater visual fatigue; (3) the results show that VR can cause quite severe visual fatigue, along with motion sickness passed on sensory mismatch. Therefore, it is recommended to avoid viewing experiences that are inconsistent with the brain's physiological experience, such as walking while viewing a mobile phone, or reading in a moving car. The proposed visual fatigue assessment model provides easy and objective quantification of visual fatigue indicators, contributing to the reduction of risk for eye injury and disease. [ABSTRACT FROM AUTHOR]

The purpose of this study was to use the International Classification of Functioning, Disability and Health (ICF) to identify physical and psychosocial problems associated with symptoms of Behçet's disease (BD) in Japanese patients. Thirty patients with BD were interviewed in a pilot study using the "ICF Checklist", and a team of medical experts selected categories related to physical and psychosocial aspects of BD. To identify specific physical and psychosocial problems of Japanese patients with BD, 100 new patients were interviewed using the selected categories. Among the 128 categories in the original ICF Checklist, 80 categories were identified as impaired, and another 12 ICF categories were added based on expert discussion of patients input. The number of problem categories was significantly greater in patients with BD with eye involvement and fatigue (eye involvement, 25.7 categories; fatigue, 25.2 categories; both P < 0.001). Specifically, patients with eye involvement had more difficulties with problems in daily life, such as writing (odds ratio 4.2), understanding such nonverbal messages as gestures and facial expressions (13.7), moving (5.7), walking in intense sunlight and bright light (17.6), and patients with fatigue had more difficulties with climate problems such as symptoms getting worse at the turn of the seasons or on cold days (2.5), compared to those without these symptoms. This study demonstrated that support focusing not only on physical symptoms but on other aspects of life as well is necessary for patients with BD, particularly patients with eye involvement and fatigue. [ABSTRACT FROM AUTHOR]

Purpose: Exposure to additional environmental stress during computer work, such as visual and psychological demands, is associated with increased eye and neck discomfort, altered moods, and reduced well-being. The aim of this study is to elucidate further how subjective responses in healthy, young females with normal binocular vision are affected by glare and psychological stress during computer work, and to investigate possible associations between trapezius muscle blood flow and neck pain development. Methods: 43 females participated in a laboratory experiment with a within-subject design. Four 10-min computer work conditions with exposure to different stressors were performed at an ergonomically optimal workstation, under the following series of conditions: no additional stress, visual stress (induced as direct glare from a large glare source), psychological stress, and combined visual and psychological stress. Before and immediately after each computer work condition, questionnaires regarding different visual and eye symptoms, neck and shoulder symptoms, positive and negative state moods, perceived task difficulty, and perceived ambient lighting were completed. Associations between neck pain and trapezius muscle blood flow were also investigated. Results: Exposure to direct glare induced greater development of visual/eye symptoms and discomfort, while psychological stress exposure made participants feel more negative and stressed. The perception of work lighting during glare exposure was closely related to perceived stress, and associations between visual discomfort and eyestrain, and neck pain were observed in all conditions. Furthermore, participants with high trapezius muscle blood flow overall reported more neck pain, independent of exposure. Conclusions: Exposure to visual and psychological stresses during computer work affects the development of symptoms and negative moods in healthy, young females with normal binocular vision, but in different ways. The results also demonstrate the complex interactions involved in symptom development and lighting appraisal during computer work. When optimizing computer workstations, the complexity of the field must be taken into account, and several factors, including visual conditions, must be considered carefully. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the changes in spherical equivalent and pupil response during near viewing in patients with intermittent exotropia (IXT) who have complaints of blurred vision or asthenopia from near viewing in daily life using a novel binocular wavefront aberrometer. Study design: A cross-sectional study. Methods: Ten IXT patients and ten healthy subjects wearing full-correction lenses at far sight (5 m) were instructed to fixate on a near target at 67 cm, which was then moved to 40 cm three times. Serial changes in the spherical equivalent (SE) refractive error (SE) were measured during this task using a laboratory-made open-field binocular Hartmann–Shack wavefront aberrometer and compared between patients and healthy subjects. In the IXT patients, regression analysis was performed between ∆SE and exodeviation angles, as measured by an alternate prism and cover test. Pupil-diameter and pupil-constriction ratios were also compared between patients and healthy subjects, and the correlation of constriction ratio with ∆SE was calculated for both groups. Results: Compared to healthy subjects, IXT patients demonstrated significantly lower ∆SE of convergence (mean ± SD, 0.91 ± 0.26 D vs. 1.15 ± 0.19 D; P < 0.05) and divergence (0.93 ± 0.28 D vs. 1.16 ± 0.20 D; P < 0.05). Angle of exotropia was negatively correlated with ∆SE during far-sight and near-sight convergence and divergence (P < 0.05). Pupil-constriction ratio was also reduced in patients compared to healthy subjects (6.67% ± 3.31% vs. 11.9% ± 5.96%; P<0.05). Pupil-constriction ratio was positively correlated with ∆SE during convergence in both groups (P < 0.05). Conclusion: Insufficient accommodation and pupil constriction during near viewing were observed in patients with IXT who had complaints of blurred vision or asthenopia from near viewing. These conditions might contribute to symptoms, such as fatigue, eye strain and impaired visual performance. [ABSTRACT FROM AUTHOR]

Background and Objectives: Conventional endoscopy provides two-dimensional (2D) information without depth information. This study compared three-dimensional (3D) endoscopy and 2D endoscopy using an endoscopic submucosal dissection (ESD) training model to evaluate the utility of 3D endoscopy.Methods: Porcine stomach specimens (7 × 7 cm) were prepared from commercially available resected porcine stomachs and a 10-mm hypothetical lesion was marked at the center of each specimen. Specimens were individually placed in an ESD training model, and subjected to either 2D or 3D ESD. En bloc resection rate, perforation rate, incision time, dissection time, and levels of five eyestrain symptoms (fatigue, pain, blurred vision, head-heaviness, and headache; 100-mm visual analog scale) were compared between the 2D and 3D procedures. In a crossover design, 8 endoscopists each performed two 2D and two 3D procedures.Results: All 32 lesions were resected en block, but perforation occurred in one 2D procedure. Incision time was significantly shorter in 3D ESD than in 2D ESD (102.8 ± 42.1 s vs. 135.8 ± 65.7 s, p < 0.05). Dissection time was also significantly shorter in 3D ESD than in 2D ESD (366.3 ± 187.6 s vs. 517.8 ± 282.3 s, p < 0.05). Differences in levels of all symptoms except blurred vision between before and after ESD were larger in 3D ESD than in 2D ESD.Conclusions: Incision time and dissection time were significantly shorter in 3D ESD compared with 2D ESD, but eyestrain was increased. Depth information from 3D images appears to facilitate rapid and stable ESD maneuvers. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate and compare tear film changes and ocular symptoms after reading an electronic book (e-book) and a printed book.Study design: Clinical and experimental.Methods: Crossover study was conducted in 30 healthy volunteers, some of whom read an e-book and others a printed book for 20 minutes and then switched the following week. Tear meniscus height (TMH), non-invasive break-up time (NIBUT), fluorescein break up time (FBUT), corneal and conjunctival staining score, and questionnaires about seven ocular symptoms were evaluated before and after reading by both reading methods.Results: After reading an e-book, FBUT and NIBUT were significantly decreased (p<0.001for both). Similar to printed book readers (p=0.006, p=0.04, respectively). TMH and corneal and conjunctival staining score showed no significant differences in either group. Comparing the two groups, the e-book group showed more decrease in TMH, FBUT, and NIBUT (p>0.05). Ocular symptoms were significantly increased in both groups. The e-book group showed more increase in all symptoms, but only tearing (p=0.03) and burning sensation (p=0.02) were significantly different.Conclusions: Reading an e-book affected tear film instability and significantly increased burning sensation and tearing to a larger extend than reading a printed book. [ABSTRACT FROM AUTHOR]

Purpose: Among computer workers, visual complaints, and neck pain are highly prevalent. This study explores how occupational simulated stressors during computer work, like glare and psychosocial stress, affect physiological responses in young females with normal vision.Methods: The study was a within-subject laboratory experiment with a counterbalanced, repeated design. Forty-three females performed four 10-min computer-work sessions with different stress exposures: (1) minimal stress; (2) visual stress (direct glare); (3) psychological stress; and (4) combined visual and psychological stress. Muscle activity and muscle blood flow in trapezius, muscle blood flow in orbicularis oculi, heart rate, blood pressure, blink rate and postural angles were continuously recorded. Immediately after each computer-work session, fixation disparity was measured and a questionnaire regarding perceived workstation lighting and stress was completed.Results: Exposure to direct glare resulted in increased trapezius muscle blood flow, increased blink rate, and forward bending of the head. Psychological stress induced a transient increase in trapezius muscle activity and a more forward-bent posture. Bending forward towards the computer screen was correlated with higher productivity (reading speed), indicating a concentration or stress response. Forward bent posture was also associated with changes in fixation disparity. Furthermore, during computer work per se, trapezius muscle activity and blood flow, orbicularis oculi muscle blood flow, and heart rate were increased compared to rest.Conclusions: Exposure to glare and psychological stress during computer work were shown to influence the trapezius muscle, posture, and blink rate in young, healthy females with normal binocular vision, but in different ways. Accordingly, both visual and psychological factors must be taken into account when optimizing computer workstations to reduce physiological responses that may cause excessive eyestrain and musculoskeletal load. [ABSTRACT FROM AUTHOR]

This study was conducted to investigate ocular complications and their relationship with sleep problems between IT students at Shahroud University of Technology as professional computer users and public health students at Shahroud University of Medical Sciences as non-professional computer users. This descriptive, cross-sectional study was conducted in 2014-2015 on 290 students, including 145 IT and 145 public health students. The students were selected by simple random sampling. Data were collected using five questionnaires, including a demographic questionnaire, the Ocular Surface Disease Index (OSDI), the Visual Fatigue Questionnaire, the Epworth Sleepiness Scale (ESS) and the STOP-BANG, and an examination for visual acuity. Data were analyzed in SPSS-22 using descriptive and inferential statistics and the level of statistical significance was set at P < 0.05. The comparisons showed a significant difference in the mean scores of the OSDI, VFQ and ESS between the male and female students, as all these scores were higher in the female students; however, no significant differences were observed in these scores between the professional and non-professional users. Given the significant direct relationships between the scores of the four questionnaires, it can be argued that sleep disorders and ocular disorders have reciprocal effects on each other. Sleepiness, dry eye and eye strain were not different between the groups of professional and non-professional computer users, but long hours of computer and cellphone use were observed so all students need to receive further education and correct ergonomics regardless of their field of study. [ABSTRACT FROM AUTHOR]

Background: It is commonly believed that robotic surgery systems provide surgeons with an ergonomically sound work environment; however, the actual experience of surgeons practicing robotic surgery (RS) has not been thoroughly researched. In this ergonomics survey study, we investigated surgeons' physical symptom reports and their association with factors including demographics, specialties, and robotic systems.Methods: Four hundred and thirty-two surgeons regularly practicing RS completed this comprehensive survey comprising 20 questions in four categories: demographics, systems, ergonomics, and physical symptoms. Chi-square and multinomial logistic regression analyses were used for statistical analysis.Results: Two hundred and thirty-six surgeons (56.1 %) reported physical symptoms or discomfort. Among those symptoms, neck stiffness, finger, and eye fatigues were the most common. With the newest robot, eye symptom rate was considerably reduced, while neck and finger symptoms did not improve significantly. A high rate of lower back stiffness was correlated with higher annual robotic case volume, and eye symptoms were more common with longer years practicing robotic surgery (p < 0.05). The symptom report rate from urology surgeons was significantly higher than other specialties (p < 0.05). Noticeably, surgeons with higher confidence and helpfulness levels with their ergonomic settings reported lower symptom report rates. Symptoms were not correlated with age and gender.Conclusion: Although RS provides relatively better ergonomics, this study demonstrates that 56.1 % of regularly practicing robotic surgeons still experience related physical symptoms or discomfort. In addition to system improvement, surgeon education in optimizing the ergonomic settings may be necessary to maximize the ergonomic benefits in RS. [ABSTRACT FROM AUTHOR]

CONCLUSIONS:Ahmed Glaucoma Valve implantation is an effective and relatively safe therapy for the treatment of refractory glaucoma in Indians.Eye (2005) 19, 183-190. doi:10.1038/sj.eye.6701447 Published online 16 July 2004 [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article on Dante and asthenopia visual problem during the Middle Ages.