James Sheedy

• Pacific University Oregon

Background: Computer vision syndrome (CVS) is a collection of symptoms related to prolonged work at a computer display. Objective: This article reviews the current knowledge about the symptoms, related factors and treatment modalities for CVS. Methods: Relevant literature on CVS published during the past 65 years was analyzed. Results: Sympt...

At a fixed viewing distance (VD), reading speed increases with print size. It is not known if this holds for computer tasks when postures are not constrained. Reflective glare on a monitor may reduce productivity. The effects of both may be modified by age. We evaluated effects of age, font size, and glare on performance for visually demanding text...

Purpose: The study evaluated the accuracy of depth perception afforded by static and dynamic stereoscopic three-dimensional (S3D) images with proportional (scaled to disparity) and constant size cues. Methods: Sixty adult participants, 18 to 40 years mean, 24.8 years), with good binocular vision participated in the study. For static S3D trials, par...

Purpose: Stereoscopic three-dimensional (S3D) viewing enhances depth perception of two-dimensional (2D) images. The present study measured viewer's ability to discern depth differences and depth change afforded by image disparities presented on an S3D display. Methods: Sixty adults (age 24.8 +/- 3.4 years, 28% male) with binocular acuity better tha...

Nineteen young (18-35 year-old) and seven older presbyopic (55-65 year-old, wearing bifocal or progressive glasses) subjects with the same average visual acuity at near distance participated in this full-factorial, repeated measures study with two trial factors: font size (capital letter heights of 1.78, 2.23, and 3.56 mm) and reflective glare. The...

Purpose: To measure progressive addition lenses (PALs) by three techniques and to compare the differences across techniques. Methods: Five contemporary PALs (Varilux Comfort Enhanced, Varilux Physio Enhanced, Hoya Lifestyle, Shamir Autograph, and Zeiss individual) with plano distance power and a +2.00 diopters (D) add were evaluated under the co...

To help maintain clear vision and ocular surface health, eye blinks occur to distribute natural tears over the ocular surface, especially the corneal surface. Contact lens wearers may suffer from poor vision and dry eye symptoms due to difficulty in lens surface wetting and reduced tear production. Sustained viewing of a computer screen reduces eye...

Stereoscopic 3D displays heighten perceived immersion but elevate viewing symptoms for some viewers. The present study measured prevalence and magnitude of perceived immersion and viewing symptoms in stereoscopic viewing, and related them to viewer's characteristics and viewing position. Two hundred three teens and adults viewed a movie in 2D or 3D...

Asthenopia has been associated with reading under visually stressful conditions. However, it is not known whether increased cognitive load contributes to asthenopic symptoms. The purpose of this study was to evaluate the contribution of increased cognitive load (with or without visual stress inducing conditions) to asthenopic symptoms associated wi...

Transverse chromatic aberration (TCA) smears the retinal image of peripheral stimuli. We previously found that TCA significantly reduces the ability to recognize letters presented in the near fovea by degrading image quality and exacerbating crowding effect from adjacent letters. The present study examined whether TCA has a significant effect on ne...

The objective of this research is to assess the ocular and muscular response to long-duration reading under different visual and cognitive difficulty levels. Thirty-five subjects, with 20/20 vision and without history of ocular pathology or cognitive deficits, participated in the study. Subjects read under different visual and cognitive difficulty...

Background / Purpose: The purpose of this study was to compare acuity measurements with a new visual target compared to Landolt Ring (LR) visual acuity measurements. The new target, named “DyopsTM”, is a donut shaped ring comprised of 8 black and white equally sized segments. The ring slowly spins at 40 rotations/minute and reduced in angular siz...

Vergence and accommodative responses in viewing near objects in the real world are behaviorally coupled to maintain clarity and singularity for the object of regard. However virtual stereoscopic stimuli, such as in 3D displays, create non-normal coupling that may cause improper vergence and accommodative responses, possibly resulting in visual disc...

Musculoskeletal complaint rates are high among those performing low-level static exertions (LLSEs), such as computer users. However, our understanding of the causal mechanisms is lacking. It was hypothesized that myofascial trigger point (MTrP) development might be one causal mechanism to help explain these complaints and that static postural and v...

This public health report leverages 3D/VR/AR to advance principals that inform a unique secondary prevention 3D vision model that can identify vision disorders in otherwise asymptomatic individuals. Once identified and diagnosed these disorders can be successfully treated to enhance learning and promote vision health justice.

Purpose: Two types of asthenopia (internal and external) have been previously identified: internal asthenopia is a pain or ache inside the eye caused by accommodative and convergence stress; external asthenopia is dry eye-like symptoms (irritation and burning) caused by adverse visual stimuli such as glare or reading compromised images. This study...

Purpose: To determine the feasibility of collecting accurate, continuous accommodative data during reading. Methods: Real-time accommodative measures were measured on nine subjects (5 female, 4 male) under three conditions while accommodative measurements were collected at 5 Hz with the Grand Seiko WAM-5500 open-field autorefractor. The first two c...

Transverse chromatic aberration (TCA) smears retinal images of peripheral stimuli. In reading, text information is extracted from both foveal and near fovea, where TCA magnitude is relatively small and variable. The present study investigated whether TCA significantly affects near foveal letter identification. Subjects were briefly presented a stri...

Purpose: To determine the difference, if any, in text legibility and the accommodative response between hard copy, LCD desktop, and handheld video displays, and how it affects users’ accommodative responses. Introduction: Many users report greater comfort reading on a handheld device than on a desktop monitor. We postulated that this was because ha...

Determine the effects of display viewing distance on both the visual and musculoskeletal systems while the text height is held constant across viewing distances. The distance from the eyes to a computer display may affect visual and neck comfort. If the angular size of the characters remains the same, it is recommended that the display be placed at...

To model the effects of computer use on reported visual and physical symptoms and to measure the effects upon quality of life measures. A survey of 1000 university employees (70.5% adjusted response rate) assessed visual and physical symptoms, job, physical and mental demands, ability to control/influence work, amount of work at a computer, compute...

To study the orbicularis oculi muscle response to asthenopia-inducing conditions. Twenty subjects (18-36 years) screened for 20/20 vision in each eye participated in the study. Subjects read passages under different asthenopia-inducing conditions. The inducing conditions were glare, low contrast, small font size, refractive error, up gaze, accommod...

To determine the sensitivity of the electromyography (EMG) response of the orbicularis oculi muscle to selected lower-level visually stressful conditions to establish the extent to which it can be used as a measure of visual discomfort. Thirty-one subjects (18 years or older) with 20/20 vision, without history of ocular pathology, oculomotor limita...

Eyestrain, or asthenopia, can be categorized into 2 types: an internal type consisting of sensations of strain and ache felt inside the eye and caused by stress of the accommodative and convergence mechanisms; and an external type consisting of sensations of dryness and irritation on the front of the eye and caused by compromised conditions in the...

The mechanism of musculoskeletal pain underlying low level static exertions, such as those experienced during computer work, is poorly understood. It was hypothesized that static postural and visual stress experienced during computer work might contribute to trigger point development in the trapezius muscles, resulting in myofascial pain. A study w...

The near visual acuity (400 mm distance) of 27 children aged 10-11 years old was measured by a licensed optometrist under two common fluorescent lamps of CCT 3600 K and 5500 K. Acuities were measured for three lighting conditions, either both lamps providing equal task luminance or a condition where the task and room luminance from the 5500 K lamps...

Previous studies have shown that, when presented in rapid stream (i.e., RSVP paradigm), word recognition speed for strings of three-letter words increases approximately 10% with large letter spacing, both in the fovea and the periphery (up to 10° eccentricity). A possible explanation is that small spacing may cause features of individual characters...

The Minkwitz theorem, which can be proven to apply to the immediate surface surrounding a line of umbilics, states that astigmatism perpendicular to the line changes twice as quickly as the rate of change of power along the line. Our objective is to test how the Minkwitz theorem applies to the design of progressive addition lenses (PALs). Our prima...

We hypothesize that eyelid squint inhibits blink rate. This is part of a larger hypothesis that, because eyelid squint improves vision under conditions of optical defocus and/or glare, and reduced blink rate is assumed to contribute to dry eye symptoms, eyelid squint is part of the mechanism resulting in asthenopia. This study investigates the effe...

Occupational progressive lenses (OPLs) utilize progressive power optics and are designed primarily to meet near and intermediate viewing needs such as working at a computer workstation for presbyopic patients. OPLs are fabricated to have the prescribed near power in the lower part of the lens and the power in the upper portion of the lens is determ...

The luminance surrounding a computer display can potentially reduce visibility of the display (disability glare), result in sensations of discomfort (discomfort glare) and result in transient adaptation effects from fixating back and forth between the two luminance levels. The study objective was to measure the effects of surround luminance levels...

Effects of font design and electronic display parameters upon text legibility were determined using a threshold size method. Participants' visual acuity (inverse of the minimum detection size, representing the threshold legibility for each condition) was measured using upper- and lowercase letters and lowercase words in combinations of 6 fonts, 3 f...

To test the validity and repeatability of an automated subjective refractor compared with subjective refraction performed by clinicians. Corrected visual acuity was used to compare the validity of each technique. On each of two visits separated by at least 1 week, the following were measured in 60 naive subjects (mean age, 33 +/- 11 years): automat...

To investigate the relations between selected key optical parameters and the sizes of the clear viewing areas of progressive addition lenses (PALs). The optics of 28 PALs (plano with +2.00 D add) currently on the market were measured with a Rotlex Class Plus lens analyzer. Horizontal cross sections were analyzed in 1 mm vertical steps with respect...

The objective of this study was to use state-of-the-art methods to measure the optical characteristics of commonly available progressive addition lenses (PALs) and to develop derivatives of the optical measurements that can be used as guidelines in selection of lenses based on patients' visual needs. The optics of 28 PALs currently on the market we...

Ultraviolet radiation (UVR) can cause damage to the eyes. Some of the damage is acute, with immediate signs and symptoms, while some of the damage is the result of cumulative or long-term UVR exposure. Because the most common source of UVR is the sun, individuals who are exposed to sunny environments should be advised to protect themselves properly...

Any of several conditions can cause asthenopia. The purpose of this study was to determine whether the particular sensations or their location vary dependent on the symptom-inducing condition. Twenty subjects with good vision performed eight reading tasks in random order during different conditions. Each condition used different stimuli to induce a...

We propose that eyelid squint can reduce the impact of several conditions known to cause eyestrain such as uncorrected refractive error, accommodative dysfunction, presbyopia, and glare. Clinicians commonly accept that squint improves visual acuity (VA) in the presence of refractive error, and even though the benefit of eyelid squint in bright ligh...

The hypothesis is that using a contrast-enhancing filter (CEF) on a computer display will improve display legibility, reading speed and visual comfort. Twenty subjects performed reading tasks, letter counting tasks, and legibility measurements on eight display conditions: a cathode ray tube (CRT) and liquid crystal display (LCD) matched for size an...

Extremely well known for his work in VDT-related syndromes, James Sheedy writes for the optometrist in practice. Diagnosing and Treating VDT-Related Visual Problems addresses the visual and environmental factors that cause the visual problems experienced by computer users.

Vision problems and eye-related symptoms are common among computer users. The causes of the symptoms can be diagnosable eye conditions and/or workplace ergonomic problems that are difficult to evaluate during an eye examination. An on-site evaluation of computer use in the workplace can be effective in improving workplace ergonomics and in screenin...

Very small high-resolution displays (SVGA, 800 x 600 pixels) worn near the eye and imaged to create a virtual image have potential as alternatives to traditional computer displays. Twenty-two subjects performed text-based tasks on five displays: monocular virtual, binocular head-mounted virtual, hard copy, flat panel, and a small format portable di...

Computer workers with presbyopia are at greater risk for the development of symptoms with a conventional prescription vs. a computer prescription because general-wear multi-focal corrections often do not provide adequate correction for the viewing distances and angles needed at the computer workstation. "Computer glasses," as defined by the America...

Vision and eye problems at computers are widespread and have become known as Computer Vision Syndrome (CVS). Symp- toms include eyestrain, blurred vision, dry eyes, irritated eyes, eye fatigue, neck ache and backache. Symptoms can result from vision and eye disorders and/or from envi- ronmental disorders. Treatment often re- quires more critical te...

Diurnal variations in vision have been reported in radial keratotomy (RK) patients. Applicants to certain professions may meet an uncorrected vision standard at the time of testing but fail to meet that standard at another time. Ten firefighter applicants who had undergone RK and nine normal subjects attended for two morning visits, and two afterno...

Background. Diurnal variations in vision have been reported in radial keratotomy (RK) patients. Applicants to certain professions may meet an uncorrected vision standard at the time of testing but fail to meet that standard at another time. Methods. Ten firefighter applicants who had undergone RK and nine normal subjects attended for two morning vi...

A particular problem in the display of scanned text is the fact that, given current technology limitations, images can be scanned at a much higher pixel density than they can be displayed on the monitor. Therefore one pixel on the monitor must be used to represent a block of pixels in the scanned image. Most commonly a reduction algorithm is applie...

We studied whether task performance improves during the initial wearing period of selected presbyopic contact lens corrections. In three previous studies significant decreases in performance on three selected tasks were measured before and after initial wearing periods to monovision contact lenses (N = 18, 8 weeks of wear), concentric bifocal lense...

One thousand three hundred seven optometrists responded (25.3 percent response rate) to a mail questionnaire concerning VDT patients in their practice. On the average, 14.25 percent of optometric patients present with symptoms primarily associated with use of the VDT, or almost 10 million examinations annually when projected to the U.S. population....

Reading performance, measured by lines of text read during 30-min sessions, and visual comfort, measured with a questionnaire at the end of each trial, were compared for a group of 15 subjects, with four trials on each of three monitor conditions: a VGA monitor where a mouse and scroll bar were used to advance the text (VGA Scroll), an experimental...

We measured vision and task performance on 26 presbyopes, ages 46 to 65 years, fitted with diffractive bifocal contact lenses (BFCL) and monovision contact lenses (MVCL). Distance contact lenses combined with reading spectacles (DCL) served as the control condition. Twenty subjects completed the 6-week study. All subjects wore BFCL and MVCL daily f...

Occupational hazards to vision, hearing, balance, olfaction, and taste typically constitute a small fraction of specialty medical practices in ophthalmology and otolaryngology. With the possible exception of noise-related hearing loss and VDT eye hazards, the scientific literature regarding these hazards tends to be scattered and variably accessibl...

This is an introduction to the joint feature on noninvasive assessment of the visual system and ophthalmic and visual optics.

Previous studies found task and vision performance differences between presbyopic contact lens corrections and distant contact lenses combined with reading spectacles. The present study was designed to compare task and vision performance with single vision contact lenses and spectacles. Eighteen soft (SCL) and seventeen rigid gas permeable (RGP) su...

We evaluated the effects of concentric simultaneous vision bifocal contact lenses on task performance, visual acuity, and stereopsis. Forty extensively screened presbyopes were fitted with CIBA Spectrum center-near bifocal contact lenses (BCL) and with distant contact lenses combined with reading spectacles (DCL) which served as the control. Thirty...

We evaluated the visual results and success rate with a center-near concentric simultaneous vision bifocal contact lens. Forty subjects (screened from 175 presbyopic applicants) entered the study and were fitted with the CIBA Spectrum bifocal lenses (BCL) and also with single vision distance contact lenses combined with reading glasses (DCL). Visua...

Automated focimeters can be used to make quick, precise measurements of off-axis power and prismatic effects corresponding to an eye rotating behind a spectacle lens. An automated focimeter, the Humphrey Lens Analyzer, was assessed in this regard. The Humphrey Lens Analyzer can be used to give a valid measure of off-axis power of lenses with low po...

An important function of vision is to provide us with sensory information to efficiently perform tasks - especially occupational-type tasks. In the research laboratory and the clinic we often measure and quantify various aspects of the visual sense such as visual acuity, stereoacuity, contrast sensitivity, amplitude of accommodation, etc. These and...

Performance was measured on an editing task which required counting the number of occurrences of an assigned letter in a paragraph of random letters. The task was presented in three different display modes: (a) a video display (VDT) with white characters on a black background, (b) a white-on-black photograph of the VDT display, and (c) a black-on--...

The Video Display Terminal Eye Clinic was designed to relieve the symptoms of video display terminal users by diagnosing and treating visual problems and by analyzing the patients' work station environment through an in-office simulation and making suggestions for improvements. The Clinic was open to the public and patients were therefore self-sele...

The effects of base-in (BI) and base-out (BO) prism upon performance of four occupational-like tasks were measured on a group of 10 subjects who had normal binocular vision. Performance on tasks which required depth perception was significantly poorer when subjects wore prism glasses with 8 and 12 delta BI and BO, whereas 4 delta BI and BO did not...

The effects of monovision (MV) contact lens wear on the performance of occupational-type nearpoint tasks was evaluated on 18 presbyopic subjects (ages 44 to 67 years) by comparing MV performance (MV condition) to that with distance contact lenses with reading glasses (BV condition). Each subject had correctable distance visual acuity of 6/6 (20/20)...

Color constancy refers to the phenomenon that the perceived colors of objects are largely unaltered by changes in the illuminant or by viewing through colored filters. Deviations from perfect constancy, induced by filters similar to ophthalmic tints, were investigated in this study. Munsell color chips were forced-choice categorized into R, Y, G, o...

The optical characteristics of the major progressive addition lenses were measured using an automated lensometer with a specially designed lens holder to simulate eye rotation. Measurements were made every 3 degrees (about 1.5 mm) and graphs of isospherical equivalent lines and isocylinder lines were developed. Generally the near zone of these lens...

Vertical yoked prism is sometimes incorporated into multifocal lenses to obtain a thinner lens, or prescribed for oculomotor deficiencies, or occurs if the vertical placement of spectacle lenses before the eyes is inappropriate. Patient acceptance of and postural and perceptual adaptation to such prism were studied. Twenty-three subjects wore spect...

Functional advantages of binocularity were investigated by having 13 subjects perform a group of occupational-type tasks under monocular and binocular conditions. Significant binocular advantages ranging from 29.5% (pointers in straws) to 3.7% (reading speed) were measured. Tasks with many disparity cues showed the greatest binocular advantage. Thi...

Most municipalities require that police officer applicants have a minimum level of uncorrected visual acuity. The primary basis for the uncorrected acuity standards is that an officer can have spectacles forcibly removed and would need a minimum level of vision to continue performing his/her duties. This article discusses the pros and cons of allow...

Clinical measurements of fixation disparity made with the disparometer have used a 1.5 degree diameter peripheral fusion stimulus. The addition of a central fusion stimulus decreases the variability of test measurements and more closely simulates everyday visual tasks. However, this also changes the fixation disparity measurement, associated phoria...

Fixation disparity (FD) measurements were made with a 1.5 degree diameter fusional stimulus both with and without a central fusion stimulus. Measurements were made at 40 cm with no prism, 5 delta base-in (BI) and base-out (BO), and 10 delta BI and BO, on a group of asymptomatic subjects. The central fusion stimulus results in less variable measurem...

It is desirable to standardize the conditions under which visual acuity is measured because of its importance in determining whether subjects meet occupational vision standards and as an indicator of the extent or stability of pathological conditions. The chart luminance is one parameter which needs to be standardized, and the effect of the luminan...

A selective filter, such as the X-chrom lens, which is placed before one eye, serves to create a luminance difference between the two eyes. The amount of the luminance difference is dependent upon the wavelength distribution of the stimulus and could therefore serve as a clue to assist color discrimination. The ability to detect and discriminate le...

Fire fighting is a physically and visually demanding occupation. Because of the severe visual demands and the high costs of nonperformance it is necessary to establish minimum vision levels that become requirements for new fire fighters. These vision standards must be based as nearly as possible upon the specific visual needs of the occupational ta...

A recommended vision standard for police officers is presented. The visual capabilities needed to perform various police duties are described. A specific vision standard, along with criteria for screening referral or screening failure are given for each category of visual skills required for police work.

Three sets of pseudoisochromatic plates were evaluated by photometry and colorimetry. The luminance contrast between the figure and background was measured and compared with a contrast detection threshold. The chromaticity coordinates of the figure and background were evaluated on the basis of how closely they approached a dichromatic line of confu...

Despite the small eye movements, we perceive a stable visual world and a relatively fixed fixation within that stable world. This study demonstrates a method by which we can be made aware of instability of the direction of fixation and it is also shown that we do not have a fixation "point," but rather a fixation "area." Analysis of the results sho...