[ON THE CONDITIONED REFLEX NATURE OF VISUAL IMPRESSIONS WITH SPECIAL REFERENCE TO VISUAL ACUITY].
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Conditioning, Classical↗
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[Effect of the width of a white background of an optotype on visual acuity].
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Color Perception↗
Peripheral visual acuity: Th. Wertheim.
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Germany↗
Visual acuity of the U.S. Navy jet pilot and the use of the helmet sun visor.
Visor wear habits, evaluative comments and vision test data were obtained from interviews of 126 Navy fighter pilots. The interviews revealed that many pilots use their helmet sun visor whenever they fly, some use it only during certain flight operations, and others never use it. Study 1 (conducted at 343 cd/m2) revealed a decrease in low contrast visual acuity attributable to helmet sun visor use in the presence of a glare source. These findings prompted a second study of the visual effects of visor transmittance. Low-contrast spot detection, acuity, and contrast sensitivity were measured at an operationally realistic daytime illumination level (6870 cd/m2) in subjects viewing through filters ranging from 6.3% to 50.1% transmission. (Standard visor transmission is 12 +/- 4%.) Results showed that filter density, and consequently the illuminance reaching the eyes, could be varied over a wide range without critically affecting these visual functions. Prevailing environmental illuminance should be considered when selecting sun visors or sunglasses. These results have implications for optimizing visual performance through visors.
Adult↗
Grating visual acuity testing as a means of psychophysical assessment of progressive addition lenses.
Progressive addition lenses (PAL's) are subject to objectionable astigmatism due to the aspheric nature of their anterior surfaces. Optico-physical assessment of PAL's is commonly undertaken but these measures should be related to the psychophysical responses of patients whilst wearing PAL's. A technique previously used for the psychophysical assessment of contact lenses and spectacle lenses is adapted and demonstrated for the measurement of grating visual acuity (VA) through the aspheric portion of PAL's. The apparatus encompasses an astronomical telescope with magnifying power of unity designed to stabilize accommodation. This paper considers the astigmatism present with three different PAL designs along a horizontal section cutting orthogonally through the umbilical line of each lens. VA was measured, using high contrast vertical and horizontal gratings, along the same horizontal sections of the PAL's studied. A reduction in VA was noted with an increase in the angle of eccentricity from the umbilical line.
Astigmatism↗
Visual acuities and manifest refractions prior to LASIK retreatments.
PURPOSE: To demonstrate that patients undergoing LASIK retreatments generally have good uncorrected vision and small refractive errors prior to retreatment surgery. METHODS: A list was generated of all refractive surgery retreatments performed in our four laser centers from August 2003 to July 2004. From this list, a total of 100 patient charts were randomly chosen. Only eyes that had full distance correction with LASIK as the primary surgery were included. The last uncorrected visual acuity (UCVA) and manifest refraction spherical equivalent (MRSE) prior to retreatment were recorded. RESULTS: For a total of 109 eyes studied, the average UCVA prior to retreatment was 20/36. Eighty-one percent (88/109) of the retreated eyes were already seeing > or = 20/40. The average MRSE prior to retreatment was -0.43 +/- 0.98 D. CONCLUSIONS: The majority of patients receiving LASIK retreatments have relatively good uncorrected vision and minimal refractive errors prior to retreatment.
Adult↗
[Visual acuity and intraocular pressure after surgery in congenital glaucoma (author's transl)].
In 124 eyes (82 patients) a total of 152 trabeculotomies were performed. Re-examinations were done after three and six months and then every year. After at least three years pressure was controlled in 67 out of 80 eyes (84%). Less favorable results were achieved in secondary glaucomas, in cases with previous surgery, if age at surgery was more than one year and in cases of known heredity. Corneal diameter and preoperative pressure did not influence the postoperative pressure. In 24 out of 60 eyes (44%) the final visual acuity was 0.4 or more. Vision and refraction were independent of the corneal diameter.
Female↗
Reduced visual acuity in elderly people: the role of ergonomics and gerontechnology.
Gerontology is the scientific study of the ageing process and special problems of aged people. Ergonomics is an applied science for optimizing performance and productivity and reducing the risks of injury, discomfort and illness. Gerontechnology is concerned with fundamental and applied research on the complex interaction of elderly people with technological products and the built environment. It has the potential to improve the capability of people confronted by the challenges of ageing. We suggest that gerontechnology may have a particular role in relation to the reduction of visual acuity, and can improve the comfort and safety of older people.
Aged↗
[Visual acuity and binocular vision following surgery of extreme retinal detachment].
Retinal surgery with implantation of silicone oil was performed in 33 patients presenting with idiopathic or traumatic proliferative vitreoretinopathy. Following removal of the oil patients were on average followed-up for 6 to 29 months (14 months). Sixteen patients had had buckling procedures prior to endosurgery. Improvement of vision up to 4 rows of optotypes was noted in 21 patients following silicone oil removal. Three cases showed a large, organic, central scotoma. Ten patients suffered from diplopia; 3 of whom were known to have had a preexisting strabismus. Suppression of the visual impression of the operated eye was seen in 4 cases. Eye muscle surgery was necessary in 4 cases. Sixteen patients demonstrated normal binocular vision as far as possible taking the visual acuity into account.
Adolescent↗
Likelihood-based modelling of age-related normal ranges for ordinal measurements: changes in visual acuity through early childhood.
This paper investigates the construction of age-related standards for ordinal outcome data. Asymmetric logistic models are used to describe the age-related changes in the cumulative probabilities for each ordinal level. Maximum likelihood estimation of model parameters allows the use of likelihood ratio tests to ascertain the appropriate model complexity. In contrast to methodologies for constructing age-related standards where the outcome is continuous, we show how the methodology leads directly to centile estimation for individuals. The method is illustrated using visual acuity measurements collected from 2968 children between 2 and 9 years of age made on a 30-point ordinal scale. We show how, in this instance, smoothing of parameters across ordinal categories leads to reduced validity of the centiles, justifying the need for specialized methodology for non-continuous outcomes.
Age Factors↗
The effect of vitreous presentation during extracapsular cataract surgery on the postoperative visual acuity at one year.
PURPOSE: The purpose of this study was to determine the effects that vitreous presentation (VP) during extracapsular cataract surgery has on patients' 1-year postoperative vision. DESIGN: The study was a prospective, long-term, clinical trial. METHODS: The study took place at 19 Department of Veterans Affairs medical centers. Patients having VP during cataract surgery and receiving a posterior chamber (PC) intraocular lens (IOL) (230 patients) were prospectively compared with a 5% random sample of nonvitreous presentation (NVP) cataract surgery patients (521 patients). Best-corrected visual acuity (BCVA) at 1 year was obtained by a masked, certified examiner. RESULTS: There was no statistical difference (P = .089) between the VP patients receiving PC IOL and the NVP patients in percentage of patients having BCVA of 20/40 or better at 1 year (91.1% vs 94.9%). There were significantly more PC IOL VP patients than NVP patients with BCVA of 20/50 or worse at some time during the first postoperative year (21.6% vs 10.9%; P = .0003), significantly fewer with BCVA of 20/20 or better at 1 year (27.8% vs 38.8%; P = .013), and significantly more with cystoid macular edema (11.5% vs 3.6%; P = .0002), retinal detachment (4.3% vs 0.2%; P = .0002), and uveitis (3.4% vs 0.6%; P = .012). The NVP patients rated their vision as very good or excellent significantly more often than the VP patients (71% vs 58%; P = .025). CONCLUSIONS: Vitreous presentation during extracapsular cataract surgery leads to somewhat worse overall outcomes in patients, although the majority of patients with VP do reasonably well.
Aged↗
The relationship between corneal eccentricity and improvement in visual acuity with orthokeratology.
BACKGROUND: Due to the renewed attention given to reduction of myopia, interest in orthokeratology has dramatically increased. This study was performed to determine whether or not a predictor for orthokeratologic changes can be identified. METHODS: Fifteen subjects enrolled in the study. For each subject, corneal eccentricity (e) was measured, subjective refraction and autorefraction were performed, and intraocular pressures were taken. Each subject was then fitted with a rigid contact lens for orthokeratology and followed for a minimum of 16 weeks. Eleven subjects completed the study. RESULTS: No correlation between corneal eccentricity and improvement in visual acuity was found. Correlations were found between e and changes in subjective refraction, and between e and changes in autorefraction. There was also correlation between lower intraocular pressure and changes in subjective refraction, and between lower intraocular pressure and changes in autorefraction. CONCLUSIONS: These findings suggest that corneal eccentricity and lower intraocular pressures may be predictors of orthokeratologic changes. A longitudinal study with a larger subject size will be needed to conclusively determine if these two measurements are predictors of orthokeratologic changes.
Contact Lenses↗
Familial exudative vitreoretinopathy: surgical intervention and visual acuity outcomes.
BACKGROUND: Familial exudative vitreoretinopathy (FEVR) is a hereditary condition that may lead to vitreous hemorrhage and traction retinal detachment necessitating surgical intervention. In this paper we review the results of surgery on seven such patients (eight eyes). METHODS: Seven patients (eight eyes) were followed up after surgery that had been performed because of vitreous hemorrhage and/or traction retinal detachment due to FEVR, in an effort to evaluate outcomes. Parameters that were noted were the current age, gender, age at the time of first surgery, length of follow-up and postoperative retinal status and visual acuity. RESULTS: Seven patients (eight eyes) ranging in age from 6 months to 44 years with a mean of 24.7 and a median of 26 years were followed. There were three females and four males. The lowest age at which surgery was first performed was 6 months and the highest was 28 years, with a mean of 14.7 and a median of 17 years. Six of the 8 eyes were reattached following surgery, although some required multiple procedures. CONCLUSION: Vitreoretinal surgery may be of benefit in helping to preserve some degree of vision in eyes of patients with FEVR who develop vitreous hemorrhage and/or retinal detachment.
Adolescent↗
Contrast sensitivity function and visual acuity of the opossum.
The Modulation Transfer Function (MTF) of the visual system of the opossum, D. marsupialis aurita, was determined using the amplitude of Visually Evoked Cortical Potentials (VECP) as response indicator. Stimuli consisted of a 180 degrees phase reversal of sinusoidally modulated gratings with an average luminance of 2.4 cd/m2. Contrast sensitivity was determined for various spatial frequencies and the MTF was calculated by the least square fit of an exponential function. The average acuity value obtained was 1.25 c/deg. The Fourier transform of the MTF was considered an approximation of the Line Spread Function of the visual system. The lowest value observed was 14 min of arc. The visual acuity observed in the mesopic range was not altered when stimulus intensity was raised to photopic levels.
Animals↗
Visual acuity for moving objects in first- and second-order neurons of the fly compound eye.
The early stages of visual systems contain a variety of components that limit both the spatial resolution and the temporal resolution of vision. When an animal sees a moving object, or moves relative to its environment, both spatial and temporal factors contribute to its ability to resolve the movement. In the present work we have combined currently available knowledge about the early stages of fly vision (optical system, photoreceptors, and large monopolar cells) to predict the resolution of the first two cell layers to moving point objects. These calculations included recent measurements of nonlinear light responses. Because background light level has a strong effect on the temporal behavior of these early visual layers, we examined the effects of light level on motion resolution. We also studied the effect of position within the eye, which is known to affect the static resolution of vision. Our results indicate that responses in large monopolar cells to moving point objects are maximal at angular velocities of 100-200 degrees/s. The resolution of point objects by both these early stages of the visual system is similar from stationary to an angular velocity of approximately 200 degrees/s. Above this, resolution deteriorates approximately linearly with velocity.
Animals↗
Stabilization of visual acuity with photodynamic therapy in eyes with chorioretinal anastomoses.
PURPOSE: (1) To evaluate, in a non-randomized, institutional, prospective study, the efficacy of photodynamic therapy with Visudyne (PDT) in neovascular age-related macular degeneration (AMD) eyes with chorioretinal anastomoses (CRA). (2) To review, in a retrospective study and for comparison, the natural evolution of neovascular AMD eyes with CRA. METHODS: Prospective clinical and angiographic study of 17 consecutive eyes with CRA, treated with PDT. Retrospective clinical and angiographic study of the natural course of 17 consecutive patients with CRA. Masked best-corrected visual acuity (VA) and angiographic features at baseline and during the period of one year were evaluated. RESULTS: The two groups presented similar characteristics at baseline regarding age, sex, initial VA, duration of follow-up and angiographic features. PDT-treated eyes showed, at 1-year follow-up, VA stabilization or improvement in 73.3% of the eyes, no cases with very severe VA loss, and no fluorescein leakage in 46.6% of the eyes. In contrast, at 1-year follow-up the natural evolution of CRA was characterized by severe or very severe VA loss in 69% of the eyes and statistically significant mean VA loss (P=0.001) with persistence of fluorescein leakage in all cases. CONCLUSION: The natural history of AMD eyes with CRA leads to progressive and dramatic VA loss, which is associated with blindness in most of the cases. PDT with verteporfin can offer some benefit to these patients, allowing VA stabilization or improvement in more than two thirds of the cases, at one year.
Aged↗
[Visual evoked potentials in the evaluation of visual acuity in infants].
Vision acuity was assessed by visual evoked potentials (VEP) in response to low-frequency chess pattern reversion in 31 full-term healthy babies aged 6 to 28 weeks. The mean vision acuity of babies aged 6 to 9 weeks was 0.5 +/- 0.01, of those aged 16 to 18 weeks 0.1 +/- 0.01; in babies aged 24 to 26 weeks vision acuity was at least 0.14, but still lower than in normal-sighted adults. The authors emphasize the advantages of low-frequency chess pattern reversion in assessment of vision acuity from VEP in babies.
Adult↗
Multifocal choroiditis with panuveitis incidence of ocular complications and of loss of visual acuity.
PURPOSE: To estimate the incidences of ocular complications and vision loss in patients with multifocal choroiditis with panuveitis (MFCPU) and to describe the association between therapy and the incidences thereof. DESIGN: Retrospective cohort study. PARTICIPANTS: Sixty-six patients (122 eyes) with MFCPU evaluated from January 1984 through June 2005 at a single-center academic practice. METHODS: Demographic and clinical information on patients diagnosed with MFCPU was collected and entered into a computerized database for statistical analyses. MAIN OUTCOME MEASURES: Development of ocular complications, including choroidal neovascularization, epiretinal membrane, and cystoid macular edema (CME), and loss of visual acuity (VA) to 20/50 or worse and to 20/200 or worse. RESULTS: Among affected eyes of patients with MFCPU, frequencies of VAs of 20/50 or worse and of 20/200 or worse at presentation were 55% and 38%, respectively. Choroidal neovascularization was observed in 22% of affected eyes at presentation and was the leading cause of poor VA at presentation. The incidence rates of vision loss to 20/50 or worse and to 20/200 or worse were 0.19/eye-year (EY) and 0.12/EY in affected eyes and 0.07/person-year (PY) and 0.04/PY in better-seeing eyes. Choroidal neovascularization was the most common cause of incident vision loss, with approximately 45% of incident vision loss attributed to new-onset or recurrent choroidal neovascularization. Presence of epiretinal membrane and CME also was associated with the development of vision loss during follow-up. When taken in combination, the incidence of any posterior pole complication was 0.13/EY in affected eyes. Use of immunosuppressive drug therapy (but not low-dose corticosteroid therapy) was associated with an 83% reduction in the risk of posterior pole complications (P = 0.004) and with a 92% reduction in the risk of 20/200 or worse VA in affected eyes (P = 0.05). Of the 6 eyes with recurrent choroidal neovascularization, only one recurrence was observed, in a patient receiving immunosuppressive drug therapy. CONCLUSIONS: Treatment with immunosuppressive drugs may improve VA outcomes among patients with MFCPU by reducing the risk of sight-threatening posterior pole complications, including new-onset choroidal neovascularization and recurrent choroidal neovascularization among eyes with existing choroidal neovascularization.
Adolescent↗