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At least 793 records · Page 44Linked to original sources
PubMed1998

Retrospective study on the evolution of visual acuity after external beam radiotherapy (20 Gy, 2 Gy fractions) for subfoveal choroidal neovascular membranes in ARMD.

This is a retrospective study of 104 patients with a total follow-up between 12 and 48 months (mean follow-up of 24 months), in which the effect of External Beam Radiotherapy with a total dose of 20 Gy (2 Gy fractions) on the visual acuity of eyes affected by subfoveal choroidal neovascularization is evaluated. The evolution of the visual acuity of the irradiated eyes is compared with the evolution of the visual acuity of their fellow eyes which were also affected by choroidal neovascularization but were not treated or treated by laser photocoagulation. This study suggests that the effect of radiotherapy, with a total dose of 20 Gy, on the visual acuity of eyes affected by subfoveal choroidal neovascularization, seems to be not better than the natural course of choroidal neovascularization or the evolution after laser therapy.

Adult↗
PubMed2006

The correlation between optical coherence tomographic features and severity of retinopathy, macular thickness and visual acuity in diabetic macular edema.

PURPOSE: To investigate the correlation between the features of optical coherence tomography (OCT) and the severity of concurrent retinopathy, central macular thickness (CMT), and best-corrected visual acuity in clinically significant diabetic macular edema. METHODS: In a prospective study, OCT was performed in 55 eyes of 55 patients with clinically significant diabetic macular edema, in 58 eyes of 30 patients with diabetes without retinopathy, and in 40 eyes of 21 healthy control subjects. The OCT features were categorized into: type 1, sponge-like retinal swelling; type 2, cystoid macular edema; type 3, serous retinal detachment; and type 4, vitreofoveal traction. RESULTS: The CMT in eyes with diabetic macular edema was significantly higher than in eyes of healthy controls or in eyes of diabetic patients without retinopathy (P < 0.001). Visual acuity correlated with CMT in diabetic macular edema (r = 0.558, P < 0.001). The prevalence of OCT type 1 was significantly higher in eyes with mild-to-moderate non-proliferative retinopathy (NPDR) than in eyes with severe NPDR to proliferative retinopathy (PDR) (P = 0.0069). The prevalence of OCT types 3 and 4 was significantly higher in eyes with severe NPDR to PDR than in eyes with mild-to-moderate NPDR (P = 0.0056). OCT type 1 showed the least CMT (P < 0.001) and the best visual acuity (P = 0.002). CONCLUSIONS: There was a significant correlation between OCT patterns of clinically significant diabetic macular edema and severity of retinopathy, CMT, and visual acuity.

Adult↗
PubMed1990

Measuring visual acuity in children using preferential looking and sine wave cards.

Preferential looking using square waves is commonly used to measure visual acuity of infants. Since sine-wave gratings have the advantage of presenting only a single spatial frequency, we completed a study to develop and validate a set of acuity cards using sine waves. The subjects were 83 children (mean age = 41.5 months, range = 3 to 69 months). The sine-wave cards were compared with Teller cards. Identical visual acuity was determined in 83% of the cases. Wilcoxon non-parametric analysis provided no evidence to reject the null hypothesis of equal visual acuities between the two methods. We conclude that sine-wave cards may be used to measure the preferential looking acuity of children.

Child↗
PubMed1992

[Clinical index for prediction of visual acuity after cataract surgery--personal experience].

The authors are giving an account of their own experience with the clinical index for prediction of the visual acuity after cataract surgery. The index uses the following data - age, visual acuity before operation, number of regularly taken drugs and frequency of reading before operation. In 171 eyes of patients operated on account of cataract by different techniques (the patients were not specially selected and some suffered from other eye diseases), the authors found a close agreement between the vision predicted by means of the clinical index and the final visual acuity after operation. Agreement was recorded in 68%. The authors recommend the clinical index for more extensive clinical tests.

Aged↗
PubMed2003

The accuracy of the amblyopia treatment study visual acuity testing protocol.

PURPOSE: To study the accuracy of the newly proposed Amblyopia Treatment Study (ATS) visual acuity testing protocol for 3- to 6-year-old children. Because no "gold standard" is available for acuity testing in pediatric patients, accuracy was evaluated using computer simulations based on a psychometric model. METHODS: Monte Carlo simulations of ATS acuity data were generated using a psychometric model that accounts for true acuity, noise in the visual system, and the rate of inadvertent misses. We varied true acuity from 20/15 to 20/400 (-0.1 to 1.3 logMAR). Visual system noise was represented by the slope beta of the psychometric function and ranged from 1 (noisy) to 8 (not noisy). The rate of inadvertent misses ranged from 0% to 10%. Accuracy of the ATS protocol was evaluated in terms of precision, bias, and stimulus range limitations. The same model was fitted to experimental ATS acuity data, thus allowing us to study the distributions of acuity, visual system noise, and level of attentiveness in 126 children ages 3 to <7 years. RESULTS: For conditions with little noise in the visual system (beta > 2), precision was well within 0.1 logMAR (corresponding to one line on a logMAR letter chart), except for acuities worse than 1.2 logMAR, and decreased to 0.15 to 0.2 logMAR for beta = 1. Bias was negligible, except in noisy conditions, where the ATS protocol tended to overestimate acuity by one line at the poor end of the true acuity range and underestimate acuity at the good end of the true acuity range. Effects of the rate of inadvertent misses were small. Fits to the real data showed a wide range of slope parameters, but only 11% had beta < or = 2. The rate of inadvertent misses was < or = 2% in 89% of cases. CONCLUSION: The simulations suggest that the ATS protocol offers an accurate method for assessing visual acuity in children in the range of 3 to 6 years of age with both precision and bias within 0.1 logMAR for typical values of the psychometric parameters.

Amblyopia↗
PubMed1989

Visual acuity development: a study of preterm and full-term infants.

Visual acuity was measured in both preterm and full-term infants by means of forced-choice preferential looking. The ages of infants tested ranged from one month to 12 months. The results of both groups were considered and compared in terms of natal and conceptional age. The data suggested that preterm infants show visual responses equivalent to their full-term counterparts by nine months of age. Trends indicate that visual acuity development in healthy preterm infants appears to be accelerated when compared with full-term infants of the same post-conceptional age.

Humans↗
PubMed2003

Bayesian model of Snellen visual acuity.

A Bayesian model of Snellen visual acuity (VA) has been developed that, as far as we know, is the first one that includes the three main stages of VA: (1) optical degradations, (2) neural image representation and contrast thresholding, and (3) character recognition. The retinal image of a Snellen test chart is obtained from experimental wave-aberration data. Then a subband image decomposition with a set of visual channels tuned to different spatial frequencies and orientations is applied to the retinal image, as in standard computational models of early cortical image representation. A neural threshold is applied to the contrast responses to include the effect of the neural contrast sensitivity. The resulting image representation is the base of a Bayesian pattern-recognition method robust to the presence of optical aberrations. The model is applied to images containing sets of letter optotypes at different scales, and the number of correct answers is obtained at each scale; the final output is the decimal Snellen VA. The model has no free parameters to adjust. The main input data are the eye's optical aberrations, and standard values are used for all other parameters, including the Stiles-Crawford effect, visual channels, and neural contrast threshold, when no subject specific values are available. When aberrations are large, Snellen VA involving pattern recognition differs from grating acuity, which is based on a simpler detection (or orientation-discrimination) task and hence is basically unaffected by phase distortions introduced by the optical transfer function. A preliminary test of the model in one subject produced close agreement between actual measurements and predicted VA values. Two examples are also included: (1) application of the method to the prediction of the VAin refractive-surgery patients and (2) simulation of the VA attainable by correcting ocular aberrations.

Bayes Theorem↗
PubMed2004

[Role of vitrectomy in patients with a decrease in visual acuity secondary to asteroid hyalosis].

PURPOSE: Asteroid hyalosis is a vitreous degeneration with calcium and phosphorus--lipid complexes in elderly patients with vascular risk factors or general disease such as diabetes mellitus. Synchysis scintillans is a complication of pathological eyes. Generally there are no symptoms. This study aims to evaluate the role of vitrectomy in patients with a decrease in visual acuity. CASE REPORTS: Pars plana vitrectomy was performed in three patients with visual acuity less than 1/10. The biomicroscope examination showed white and bright particles with rounded and variable shapes localized in the anterior vitreous, moving with the eye. The visualization of the fundus was difficult or impossible. On echography B, the vitreous was very dense with a complete posterior vitreous detachment. The vitrectomy was completed in one case by peeling an epiretinal membrane. Visual acuity was improved for two patients (6/10 or more) and stable for one patient with an atrophic DMLA. DISCUSSION AND CONCLUSION: These results were compared with studies in the literature: in spite of complications, vitrectomy can be indicated in patients with a substantial decrease in visual acuity. However, the result is conditioned by the macular status. Fluorescein angiography can, when it is possible, evaluate the fundus before surgery.

Aged↗
PubMed2006

[Development of visual acuity and refraction in deep lamellar and penetrating keratoplasty (KPL)].

BACKGROUND: Deep lamellar KPL can be considered as an alternative for penetrating KPL in pathologies of corneal stroma, because there is no risk of decompensation of the endothelium or corneal rejection. Nevertheless, it is well know in lamellar keratoplasty that scars may occur in the interface which can limit the final visual acuity. In a retrospective study we compared the postoperative development of visual acuity and refractive values in deep lamellar keratoplasty with a penetrating procedure. PATIENTS AND METHODS: 16 consecutive patients (mean age 48 years) with corneal stroma pathologies such as corneal ulcer, alkali burn and keratoconus underwent deep lamellar KPL. The control group consisted of 38 patients (mean age 42 years) with keratoconus who received a penetrating keratoplasty. Visual acuity and subjective spherical and cylindrical values of the refraction were evaluated preoperatively and after 6 weeks, 6 months and 1 year. RESULTS: The mean postoperative visual acuity (VA), spherical (SV) and cylindrical (CV) values of the deep lamellar group (results of the control group in brackets) were at 6 weeks VA = 0.24 +/- 0.24 (0.37 +/- 0.23), SV = 0.325 +/- 5.3 dpt, CV = - 1.66 +/- 0.67 dpt (- 3.08 +/- 1.93 dpt), after 6 months VA = 0.38 +/- 0.28 (0.53 +/- 0.31), SV = - 3.0 +/- 4.42 dpt (0.33 +/- 1.93 dpt), CV = - 2.57 +/- 2.03 dpt (- 2.35 +/- 1.32 dpt) and after 1 year VA = 0.41 +/- 0.27 (0.57 +/- 0.26), SV = - 2.57 +/- 4.62 dpt (0.17 +/- 3.98 dpt), CV = - 2.75 +/- 1.25 dpt (- 0.34 +/- 1.86 dpt). There was no significant difference in all the parameters between the two groups. CONCLUSIONS: As the good functional results of deep lamellar KPL are comparable to those of penetration KPL and the risk of endothelial decompensation or rejection is lower in a lamellar procedure, we suggest the use of a deep lamellar KPL in patients with an intact endothelium.

Adult↗
PubMed2001

Loss of visual acuity is the main reason why reading addition increases after the age of sixty.

PURPOSE: To determine why the reading addition increases after the age of 55 to 60 years when accommodation is zero. METHODS: Distance and near visual acuities, arm length, habitual near working distance, reading addition, and pupil diameter were measured in 44 subjects aged >60 years (mean, 72.9 +/- 5.7). Reading addition values were attained using three techniques: least-plus addition using both N-notation text and MN-READ text and the cross-cylinder technique. RESULTS: The mean dioptric working distance was 2.75 +/- 0.40 D. The reading addition found using N-notation text (+2.21 +/- 0.38 D) was significantly lower than that measured using MN-READ text (+2.48 +/- 0.49 D) or the cross-cylinder method (+2.53 +/- 0.44 D). The reading addition was positively correlated with the dioptric working distance (r = 0.47, p < 0.01), and decreasing habitual working distance was associated with poorer visual acuity (r = -0.42, p < 0.01). CONCLUSIONS: Our results suggest that decreases in near visual acuity after 60 years of age lead to a reduction in habitual working distance, which increases text angular subtense. In turn, the reduced working distance requires a greater reading addition. Increases in depth of field associated with both suprathreshold text (N-notation) and lower visual acuity lead to reading additions being less than the dioptric working distance.

Accommodation, Ocular↗
PubMed1992

[Effect of various light sources on visual functions in the age aspect. II. Visual acuity, the range of accommodation and fusion and the visual field].

The authors performed examinations in 15 middle aged persons and in 13 persons of older productive age in conditions of equivalent illumination, first the glow one, then the sodium one of 600 lx value at the stand of examination. They observed the dynamics of selected visual functions as the time went by in the forenoon hours. The group of older persons tolerated worse the sodium light and in both age groups one could observe the receding of the visual near point. The authors analyze the remaining visual functions in both conditions of illumination.

Accommodation, Ocular↗
PubMed2005

Perceptual learning improves contrast sensitivity and visual acuity in adults with anisometropic amblyopia.

To evaluate the effects of perceptual learning on contrast-sensitivity function and visual acuity in adult observers with amblyopia, 23 anisometropic amblyopes with a mean age of 19.3 years were recruited and divided into three groups. Subjects in Group I were trained in grating detection in the amblyopic eye near pre-training cut-off spatial frequency. Group II received a training regimen of repeated contrast-sensitivity function measurements in the amblyopic eye. Group III received no training. We found that training substantially improved visual acuity and contrast-sensitivity functions in the amblyopic eyes of all the observers in Groups I and II, although no significant performance improvement was observed in Group III. For observers in Group I, performance improvements in the amblyopic eyes were broadly tuned in spatial frequency and generalized to the fellow eyes. The latter result was not found in Group II. In a few cases tested, improvements in visual acuity following training showed about 90% retention for at least 1 year. We concluded that the visual system of adult amblyopes might still retain substantial plasticity. Perceptual learning shows potential as a clinical tool for treating child and adult amblyopia.

Adolescent↗
PubMed1993

Contrast sensitivity and visual acuity in patients with early cataracts.

In a population of 188 nondiabetic patients with early cataracts or nuclear brunescence, we assessed the degree to which contrast sensitivity function (CSF) provided more information about a patient's visual disability than high contrast visual acuity measurements. Data collected included LOCS II cataract classification, Bailey-Lovie visual acuity (LogMAR score), Lotmar interferometric visual acuity (LI VA), and distance contrast sensitivity function (CSF) using the Vistech 6500. Generalized least squares regression models in which CS was the dependent variable and either LogMAR score or LI VA was among the independent variables were used to ascertain whether CSF provided additional information about visual disability to that provided by LogMAR score or LI VA. Contrast sensitivity function was decreased only by nuclear opalescence at high frequencies (12 to 18 cpd); for all other cataract types and nuclear color, CSF testing provided no more information about cataract-related visual loss than LI VA or LogMAR score. Measurement of CSF using the Vistech 6500 system in patients with early cataracts provides information on visual dysfunction beyond that provided by LogMAR score or LI VA only in patients with nuclear opalescence, and that may not be clinically significant.

Adult↗
PubMed1992

Interferometer assessment of potential visual acuity before YAG capsulotomy: relative performance of three instruments.

The accuracy of white light and laser interferometers in predicting visual acuity after YAG laser capsulotomy was compared. 42 eyes of 41 patients were tested with both a Haag-Streit (Lotmar) white light interferometer and a Rodenstock laser interferometer, and 14 were also tested with a Site white light machine. The laser interferometer predicted a final visual acuity to within one line of that actually achieved in 93%, and to within two lines in 98%, whereas for the Haag-Streit these figures were 64% and 81%, and for the Site 77% and 92%. In patients with poor initial visual acuity, the difference in the relative performance of the two instruments was increased further. When interferometry was repeated after capsulotomy, the values obtained with all instruments agreed closely with Snellen acuity. This difference in predictive accuracy shows that capsular thickening causes a greater degree of optical degradation of the image produced by a white light interferometer than occurs when a laser interferometer is employed.

Adult↗
PubMed2002

[A study on cases of good apparent accommodation using an all-distance visual acuity chart and corneal shape analysis].

PURPOSE: As a part of an attempt to elucidate the mechanism of apparent accommodation, an evaluation was made of patients with good apparent accommodation using an all-distance visual acuity chart and corneal shape analysis. MATERIALS AND METHODS: The study was performed on 6 patients (7 eyes) in a good apparent accommodation group and 13 patients (15 eyes) in a poor apparent accommodation group. These were selected from patients who had undergone normal small-incision ultrasonic phacoemulsification and posterior chamber type single focus intraocular lens implantation. In these patients, all-distance visual acuity was measured using an AS-15(Kowa Co., Ltd.), and corneal shape analysis was performed using Orbscan (Orbtek Inc.). RESULTS: In all-distance visual acuity, gentle decline from far to near was noted in the poor apparent accommodation group, and the degree of decline was lower in the good apparent accommodation group. Also, a two-peak pattern, showing decline at first and then an increase, was observed in some of the cases. In corneal shape analysis, there was no specific pattern in the good apparent accommodation group. However, the difference between maximum refractive power and minimum refractive power of cornea in the ranges of 3, 5, and 7 mm in total optical power (TOP) was significantly higher in the good apparent accommodation group compared with the poor apparent accommodation group (TOP 3 mm: p = 0.0233, TOP 5 mm: p = 0.0306, TOP 7 mm: p = 0.0035). CONCLUSION: In the present study, there were three patterns in all-distance visual acuity in the good apparent accommodation group, showing a two-peak pattern, a flat pattern, and a gentle decline, and the pattern of gentle decline was observed more often than the other patterns. The results of the study also suggest that the gradient of corneal refractive power may be related to apparent accommodation.

Accommodation, Ocular↗
PubMed1981

Effects of grating stimulation on visual acuity in amblyopia.

Thirty-one children with amblyopia were treated with CAM vision stimulation. Twenty-one of them had previously been treated with conventional methods but failed to improve further. The conventional therapy was continued during and after CAM. Grating stimulation was the first treatment attempted for the rest of the children. Most children in both groups showed improved distance visual acuity after CAM-treatment and no one suffered a loss. The average visual acuity improvement was the same in both groups of children and did not vary with age. The improvement amounted to about 50% of the visual acuity before CAM, irrespective of the pre-treatment acuity level. We conclude that CAM-stimulation can be useful in cases where occlusion or other amblyopia treatment has failed, but that some form of treatment must be continued if visual acuity is to be maintained after the CAM-treatment period.

Adolescent↗
PubMed1970

Regional variations in the visual acuity for interference fringes on the retina.

1. The visual acuity of the peripheral retina was measured using both sinusoidal gratings viewed in the usual way and interference fringes formed on the retina directly.2. It is shown that optical aberrations cause a reduction in peripheral visual acuity for eccentricities of less than 5 degrees . However, the hypothesis that optical defects are a major cause of the well-known decrease in acuity with eccentricity is rejected.3. The fringe acuities at various retinal positions are compared with Osterberg's counts of the distribution of cones. It is shown that at eccentricities of less than 2 degrees , resolution approaches the theoretical limits for a mosaic of receptors.

Journal Article↗