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PubMed1994

[Changes in visual function caused by work at a data display terminal].

Working at video display terminals (VDTs) is particularly demanding in terms of orthopaedic and visual functions. This study was initiated to examine whether, and if so how, VDT work can influence the visual system. It was designed as a 5-year-prospective study based on the matched-pairs technique. The subjects were examined at the beginning and after 5 years of VDT work. The study group consisted of 102 people working at VDTs, and these were paired with 102 other office workers who did not use VDTs. The legally prescribed screening examinations of visual acuity (distance and near vision, phorias, stereopsis, and colour vision) were carried out. We also checked the anterior segments by examination with the slit-lamp and the fundus by ophthalmoscopy. Break-up time, Schirmer-I test, perimetry and tonometry were included in our range of examinations. We found a significant difference in asthenopia and daily hours of VDT work between VDT workers working less than 6 h daily and those working more than 6 h daily. In the study group pre-existing exophoria seemed to increase, but no statistical significance was found on testing. Nor was there any significant difference between the study group and the control group in the parameters examined in the course of the screening examination. In our investigation of monocular VDT workers (n = 3) we could not find any visual problems.

Adult↗
PubMedDate not supplied

[Mean-term variations of visual function of video display terminal operators: observations on 70 cases].

The aim of the study was to evaluate medium-term variations of visual functions in VDT operators and their possible relationship to VDT exposure. The clinical records of 70 VDT operators attending our outpatient service for periodical ergophthalmological evaluation were reviewed in order to evaluate the variation of some visual parameters after a two-years follow-up. These included refraction, phorias, fusional convergence and divergence, stereopsis. The group did not include subjects affected by hyperopia, large ametropias, or binocular vision disturbances and was divided into two subgroups: low exposure group (n = 20; < 4 hours/day) and high exposure group (n = 50; exposure > 4 hours/day). Asthenopia was frequent in both groups. Variation of refraction and binocular vision parameters were absent or rather limited in both exposure groups. This seems to indicate that in subjects without significant ophthalmological problems the risk of permanent functional damage is very low at medium-term.

Adult↗
PubMed1993

[Detection of cerebropathy in neurologic and psychiatric diseases].

The authors made a comprehensive examination of 16 patients--epileptics, alcoholics, psychotic subjects and patients after cerebral contusion. The patients were subjected to a neurological, psychiatric, psychological examination as well as to a morphological examination (X-ray, CT, NMR), physiological examination (EEG, polysomnography, evoked potentials), immunological examination and SPECT. The majority of patients had positive CT and SPECT findings suggesting focal brain damage. These results could be explained only in exceptional cases by injury, the majority was of unknown aetiology. With this corresponded focal EEG abnormalities and in particular sleep disorders, sometimes subjective but always detectable by objective methods. There was always a shortage of REM, sometimes also NONREM sleep. Half the patients were subjected to an immunological examination which was always positive and comprised elevated acute stage proteins and proteins associated with the stress reaction. Numerous data in the literature and the authors' experience indicate that the mentioned pathological findings are not incidental and form, independently on the aetiology, an integrated unit for which the term cerebropathy can be used. A primary role is played by the epileptic focus and its quality, i.e. above all the rate of discharge and site and humoroergic systems of the brain stem, in particular their efficiency and mutual balance. The events have a programmed sequence. At the beginning an epileptic focus develops which influences the surrounding area, secondary and tertiary foci are formed and the thalamo-cortical system is affected. Soon this is followed by an apparent influence of the epileptic activity on structures of the brain-stem. The consequence are changes affecting sleep, mood, mental performance, immunity, endosecretion and paroxysms. Subsequently individual symptoms are already prepared but have a different latency of manifestation and the latter depends also on external provoking influences. The thalamo-cortical reaction is characterized by the manifestation of epileptic paroxysms and sets in after a different interindividual incubation following injury. The same applies to the hippocampal reaction manifested by the organic psychosyndrome. Some symptoms such as changes of immunity, sleep or endosecretory function are not necessarily manifested if the influence of the focus on structures of the brain-stem is not sufficiently intense. Conversely if the effect on the brain-stem and limbic structures is greater and the effect on the thalamo-cortical system smaller, psychotiform behaviour develops. Then there are marked changes of phoria, dynamogeny, rate, affectivity, sleep and hormonal secretion and its equilibrium.

Adult↗
PubMed1993

The effects of daily-wear contact lenses on contrast sensitivity in selected professional and collegiate female tennis players.

Contrast sensitivity (CS) has recently emerged as an important predictor of visual performance. Few studies, however, have been published involving CS and its role in vision for sport. The purpose of this investigation was to determine if significant differences occurred in CS between female professional and collegiate tennis players who wore daily-wear soft contact lenses (N = 10) and those players who wore no corrective lenses (N = 10) in competition as measured by the Stereo Optical Optec 2000 Vision Tester. Subjects were between the ages of 18 and 37 years. Mean ages were 21.76 (+/- 4.018) and 25.40 (+/- 5.379) years for those wearing lenses and those not, respectively. Each subject was preliminarily screened for SVA-distance, lateral/vertical phorias, stereopsis, and color perception. All subjects were within accepted limits. CS was assessed at 1.5, 3, 6, 12, and 18 cycles per degree (cpd). Each subject was assessed monocularly; eye initially assessed was determined randomly. A 2 x 2 factorial analysis of variance (alpha = .05) was used to analyze data. No significant differences were found between eyes. Significant differences were found at 3, 6, 12, and 18 cpd. It may be concluded that those female professional and collegiate tennis players wearing no corrective lenses were significantly higher in CS at intermittent and high spatial frequencies than those who wore daily-wear soft contact lenses in competition.

Adolescent↗
PubMedDate not supplied

[Eye-strain symptoms after work with a computer screen].

BACKGROUND: In a laboratory arranged according to ergonomic rules, the influence of the work with screen monitor computer on the visual function was evaluated. MATERIAL AND METHODS: Visual efficiency before and after one-hour reading of a text from monitor was compared in 60 persons. There was 50 women and 10 men, aged 22-47. The research scheme comprised 10 trials. RESULTS: After work with the monitor, the most important changes were the following: diminished power of accommodation, removal of the near point of convergence and deviation of phoria for near vision. Statistical analysis, using Wilcoxon's test revealed significant differences between the results achieved before and after work concerning accommodation and convergence (p < 0.05). CONCLUSION: The results suggest that weakness of these important visual functions could be the cause of eye-strain in computer operators.

Adult↗
PubMed1996

[Effects on visual functions following several hours' usage of a head mounted display].

We investigated the effects of viewing video movies with a head-mounted display (HMD) for 4 to 6 hours on visual functions such as refraction, visual acuity, and accommodation-vergence system. Two or three video movies were watched without any breaks by 13 normal volunteers (age: 22 approximately 40). Measurements were made of (1) objective and subjective refraction, (2) corrected visual acuity, (3) tonic level and step response of accommodation with a computer-assisted infrared optometer, and (4) near and far phorias and AC/A ratio. Significant transient myopia was found following 4 hours' viewing, but not following 6 hours' viewing. Scrutinizing individual data, myopia was consistently found in some subjects, and hyperopia in others. We presumed that many subjects might have been influenced by initial instrumental myopia when they adjusted the focus by using the mechanism built in the HMD. No significant change was observed in any other examination. However, there was a tendency for the AC/A ratio to change after a short time, and then to recover to its original value. Based on the results in this study, it appears that some changes in accommodation and vergence systems are caused by viewing video movies with the HMD. Although the amount of changes was within normal physiological variation in this study, the possibility still remains that usage for a longer time may lead to other changes in visual function. Care is also necessary when using the HMD in subjects with subclinical problems.

Accommodation, Ocular↗
PubMed1996

Gain changes in the accommodative convergence cross-link.

The output of the accommodative vergence cross-link, the AC/A ratio, was measured before and after subjects viewed through a telestereoscope which increased their interocular separation (pd) approximately fourfold. The initial paradigm was designed to force an increase in the AC/A ratio in that subjects alternately fixated targets set at differing distances. In this paradigm, the varying vergence demands could not be met by a constant increase in phasic or tonic vergence responses. In a second paradigm, only one target was viewed at a fixed position from the eye. Now the constant vergence demand could be met by a set increase in phasic and/or tonic vergence. A significant increase in the AC/A ratio was found in the two-target study but not in the single-target study. Increases in the accommodative vergence gain did show considerable individual differences. Tonic vergence changes were interpolated from the data. This parameter increased significantly in both cases but more so when two targets were alternately fixated. This finding is consistent with current near triad models which predict that accommodative convergence input acts along with disparity vergence input to increase tonic levels of convergence. When AC/A ratios were calculated using clinical measures of the phoria at 6 and 0.4 m, increases were found in the two-target study and to a lesser degree in the single-target study. This clinical method of AC/A measure appears to have been confounded by changes in tonic vergence.

Accommodation, Ocular↗
PubMed1995

[Disparity of fixation in asthenopic syndrome].

This study provides the first description of a test of fixation disparity that can be used in daily clinical practice. Exploration of this problem lays a basis for understanding, and allows rational prescription of the use of small prisms for the treatment of asthenopia associated with horizontal heterophoria. The fixation disparity is opposite to the heterophoria in almost 30% of cases. The test has a specificity of 71,5% for a study population of 55 patients. When the disparity test was abnormal, use of this examination demonstrated that the prescription of an adapted prism was effective in all cases in eliminating the disparity. This prescription usually involved asymmetric prisms. We also found that complaints of non-specific neck and back pains tended to improve in parallel to the improvement in the asthenopia and the elimination of the disparity. We feel that these postural pains ares part of the asthenopia related to symptomatic heterophoria. The ability to study disparity in daily clinical practice will also provide the physician with a means to study the genetic relationships underlying tropias and phorias when disparity is abnormal.

Adolescent↗
PubMed1996

Aircrew fatigue monitoring during sustained flight operations from Souda Bay, Crete, Greece.

BACKGROUND: Operational flight surgeons are often responsible for determining aeromedical readiness of aircrew members whose accumulated flight time exceeds standard limitations. Realizing that operational reports of excessive flight time in aircrew are limited, we used Rayman's 1975 study of fatigue during Cambodian airlift missions as a model to evaluate 42 U.S. Navy EP-3E aircrew members flying reconnaissance missions from Souda Bay, Crete, Greece. Measured parameters focused on information accessible to operational flight surgeons. METHODS: Hoping to identify early indices of fatigue, the aircrews were monitored using anonymous questionnaires, physiologic data (mean arterial pressure, pulse, pulse pressure), and hematologic measurements (CBC, sedimentation rate). RESULTS: As suspected, no physiologic parameter indicated early fatigue. However, some aircrew demonstrated small changes in measured visual phorias as compared to prior evaluations. Anonymous questionnaires and subjective evaluation of crewmembers appeared most valuable in assessing fatigue. CONCLUSION: Incorporating previously reported recommendations for fatigue surveillance, the Souda Bay experience is an example of successful fatigue monitoring in aircrews who accumulate flight time beyond standard restrictions.

Adult↗
PubMed1997

[Studies on ocular positions at close distance with a new system of measuring ocular positions].

The purpose of our study was to develop a new system of measuring ocular positions and to assess its clinical applicability. This system is derived from that of the Hess coordimeter and is used at a distance of 40 cm. Our system enables us to distinguish tropia from phoria by testing the ocular positions both with and without a fusional target which can be seen by both eyes. All devices are installed in one structure and it can be used in a lighted room. The system was checked in 10 normal subjects by plotting the data of the charts onto a graph and deriving a static eye position curve. There was no significant vertical deviation, and there was an exodeviation of 5.32 +/- 3.78 (mean +/- standard deviation) degrees without a fusional target, but no significant deviation occurred when the fusional target was lighted. In 37 of the 38 patients with ocular motor disturbance, the results with this system corresponded well with those obtained by the Hess coordimeter or prism cover test. One particular case with extraocular myositis involving more than two extraocular muscles showed an atypical complicated pattern. We believe that our system is simple and easy for clinical evaluation of ocular movement abnormality in ophthalmic diagnosis.

Adolescent↗
PubMed1998

[Anisometropia and presbyopia: prescription of progressive lenses, a new approach].

OBJECTIVE OF THE STUDY: To show that anisometropia does not absolutely preclude the prescription of progressive lenses. MATERIALS AND METHODS: Forty-one anisometropes and presbyopes were selected for a prolonged trial of visual correction using progressive lenses. The congenital or acquired type of their anisometropia and its particular form were also studied. Each patient was submitted to a protocol comprising of a series of ophthalmologic and orthoptic tests so as to evaluate the patient's subjective far and near refraction, with measurement of phorias and of horizontal and vertical ductions, visual acuity, and the quality of binocular vision while looking in different directions. A preliminary trial of correction in actual situation was done in order to check fusion in near vision. The entire range of tests was repeated two months after the patient was provided with the lenses. The tolerance for progressive lenses during the different activities of daily life was evaluated after the second and the sixth months. RESULTS: Seven patients presenting an associated strabismus were not provided with the lenses because the initial pre-lens trial revealed a total inability to read within the near-vision zone. Among the 34 patients provided with the lenses, 21 constantly wore their progressive lenses and said that they were satisfied, 6 wore their progressive lenses during daily activities but preferred to use their unifocal lenses for prolonged reading, and 7 abandoned their progressive lenses because they could not tolerate them. Association with a strabismus is not synonymous with an initial impossibility or with abandonment because of the 27 patients who constantly wore their progressive lenses 9 were strabismic. The best results were obtained in the age range of 45 to 52 years old, for visual acuity for > 20/40, and in cases of congenital anisometropia with intermittent or permanent unilateral neutralization. On the other hand, patients presenting an acquired anisometropia, particularly postoperative, proved to be poor candidates. CONCLUSION: Weak and strong anisometropia does not absolutely preclude the prescription of progressive lenses except for certain strabismic subjects with an abnormal lateral-oriented posture.

Activities of Daily Living↗
PubMedDate not supplied

[Oculomotor risk after trans-palpebral bony decompression for thyroid-related orbitopathy].

PURPOSE: To study oculomotor disorders after transpalpebral bony orbital decompression (TPBOD) for dysthyroid orbitopathy. Pathophysiology, risk factors, preventive and therapeutic care were examined. MATERIAL AND METHODS: Forty-four patients were included in this retrospective study (76 orbits). Thirteen patients underwent surgery for severe orbital inflammation or optic neuropathy and 31 for cosmetic rehabilitation. 21 previously had orbital radiotherapy. Class IV of NOSPECS classification, primary position of gaze, diplopia and Lancaster coordimetry were studied comparatively pre and postoperatively. RESULTS: Diplopia appeared in 23.6% of the cases without deviation before surgery (tropia or phoria-tropia). Predictive factors were age and amblyopia whereas amount of retrodisplacement of the globe and radiotherapy were not. Lack of oculomotor restriction did not prevent from diplopia but may decrease its incidence. Unilateral decompression is more likely to create a vertical disorder. Pathophysiology is discussed. CONCLUSION: Oculomotor disorders can be explained by several mechanisms. Some of them can be prevented. Each patient should be aware of the risk of diplopia.

Adult↗
PubMed1998

The effect of relative spectacle magnification on aniseikonia.

PURPOSE: The purpose of this article is to study the effects of modifying relative spectacle magnification to determine what effect this has on aniseikonia, binocularity, and visual comfort. METHODS: A prospective analysis of 34 aniseikonic patients was undertaken. The etiology of aniseikonia varied from physiologically occurring to induced. Aniseikonic screening included manifest refraction, keratometry, axial length, Randot stereoacuity, associated phoria, and Keystone space eikonometry. A modified pair of spectacles was fabricated on the basis of magnification principles for iseikonic lenses. Each patient was also given a control pair of conventional spectacles. A 4-week trial period was allowed for each pair of spectacles, pertinent examination measurements were repeated, and a patient survey was administered. Data were analyzed by t-test and chi-square. RESULTS: Modifying relative spectacle magnification reduced mean aniseikonic error by 1.06% (P < 0.0001). A difference was found between the control and modified spectacles for subjective reports of visual comfort, performance, and eye-strain (P < 0.05). There was no difference between the two groups for stereoacuity or cosmetic appearance of lenses. At the conclusion of the study, 93% of patients preferred the modified lenses in direct comparison. CONCLUSIONS: Our results confirm that modification of lens designs to equalize relative spectacle magnification reduces aniseikonia and improves subjective comfort and performance of anisometropic spectacles.

Adult↗