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PubMed1991

Age-dependent changes in visual acuity and retinal morphology in pigeons.

The visual acuities of 17 pigeons that ranged in age from 2 to 17 years were tested with high-contrast, square-wave gratings. A systematic decline in visual acuity was observed that was well described by a logarithmic function. Pupillary diameter also declined with age, which decreased retinal illumination, but increased depth of focus. A small amount of presbyopia also was observed. Both the decrease in retinal illumination and the presbyopia accounted for only a trivial proportion of the acuity loss. No relationship between corneal or lenticular density and age was observed. Ophthalmoscopic examination of the optic media revealed no abnormalities associated with age. Microscopic examination of the area dorsalis of the retina (the high-density region specialized for frontal vision) revealed age-related losses of up to 33% of photoreceptors and 23% of cells in the ganglion-cell layer. A study of the photoreceptor layer within area dorsalis indicated that single-cone densities were unaffected by aging whereas the double-cone densities, which are the predominant photoreceptor type in the area dorsalis, were reduced in number by about one third. Calculation of the Nyquist limit both for photoreceptors and ganglion cells suggested that the decreased retinal density together with the decreased retinal illumination and presbyopia could not account for all of the observed acuity loss.

Aging↗
PubMed2000

Lea symbols: visual acuity assessment and detection of amblyopia.

OBJECTIVE: Lea symbols can be used for measuring visual acuity in childhood. Therefore, these symbols might be useful for early detection of amblyopia. We evaluated whether the visual acuity determined with Lea symbols (LS) corresponds to the visual acuity determined with the Landolt-C (LC). PATIENTS AND METHODS: In 55 strabismic amblyopic volunteers aged 5-59 years, the monocular visual acuity of both eyes was determined using LC and LS. For comparison, the right eye of 20 healthy volunteers was examined. Single optotypes (LC, LS) were used in 55 amblyopes and crowded optotypes (LC(17.2), LC(2.6), CLS) in 40 amblyopes. The luminance of the test charts was 180-200 cd/m(2), with a contrast >85%. The refraction of the subjects was corrected beforehand. RESULTS: In the 40 amblyopic eyes tested under each condition, LS exceeded CLS and LC by about 1 line (dB), LC(17.2) by 2 lines and LC(2.6) by 3 lines (mean values +/- SD: LS 0.62+/-1.8 dB, CLS 0.46+/-1.7 dB, LC 0.5+/-2. 0 dB, LC(17.2) 0.41+/-2.3 dB, LC(2.6) 0.29+/-2.3 dB). The non-amblyopic fellow eyes and healthy eyes showed smaller differences (fellow eyes LS 1.32+/-1.1 dB, CLS 1.17+/-1.1 dB, LC 1. 15+/-0.9 dB, LC(17.2) 1.05+/-0.9 dB, LC(2.6) 0.93+/-1.1 dB; healthy eyes LS 1.74+/-0.9 dB, CLS 1.58+/-0.8 dB, LC 1.48+/-0.6 dB, LC(17.2) 1.41+/-0.7 dB, LC(2.6) 1.32+/-1.1 dB). In the amblyopic eyes, the reduction of LC was more distinct than the reduction of LS. Fifty-two amblyopes had an amblyopia >1 dB of LC, LC(17.2) and LC(2. 6), while 50 had an interocular acuity difference >1 dB CLS. CONCLUSIONS: Using Lea symbols, a recognition acuity can be determined and amblyopia can reliably be detected. Due to their design, the Lea symbols are particularly suitable and recommendable for application in young children. However a slight systematic difference between LS and LC has to be considered.

Adolescent↗
PubMedDate not supplied

Predicting visual acuity in children with colobomas involving the optic nerve.

BACKGROUND: This study evaluates the relationship to visual acuity of four ophthalmoscopic features of colobomas involving the optic nerve. The goal was to identify those features that could predict potential visual acuity of children with these colobomas. METHODS: Fundus photographs of 23 eyes with colobomas involving the optic nerve met the entry criteria and were evaluated by two masked observers. The following features were evaluated: coloboma size, optic nerve color, foveal development, and subfoveal retinal pigment epithelial changes. Simple linear regression was used to identify the feature that most closely correlated with visual acuity. Refractive status was assessed by cycloplegic refraction. RESULTS: The only component that correlated with the development of good visual acuity was the degree of foveal involvement by the optic nerve coloboma (P = .002, R = 0.8). Significant refractive error and anisometropia were common in patients with colobomas involving the optic nerve. CONCLUSION: Central visual acuity in children born with colobomas involving the optic nerve correlates with the development of normal foveal anatomy, regardless of the size of the coloboma, the color of the optic nerve, or the presence of subfoveal pigmentary changes. Because refractive error is common, these children should receive an accurate refraction and amblyopia treatment.

Child, Preschool↗
PubMed1991

Relationship between performance in the Morris water task, visual acuity, and thermoregulatory function in aged F-344 rats.

The present experiments were designed to determine whether the loss of visual acuity and thermoregulatory control in aged rats contributes significantly to age-related deficits in the Morris water task. Relative to 2.5 mo rats, 16-18 mo F-344 rats were found to perform poorly in this spatial learning task. Their performance was also impaired in a test of visual acuity, and they became hypothermic during testing in the Morris water task. Nevertheless, 23 mo F-344 rats still retained a fairly high degree of visual acuity, and reducing the degree of visual acuity required to perform spatial mapping by adding large visual cues in close proximity to the target platform did not improve their performance. However, preventing hypothermia by warming 23 mo rats between trials in the Morris water task did significantly improve performance. These results suggest that age-related deficits in the Morris water task are not due to the loss of visual acuity; but, as a specific measure of cognitive function, performance in the Morris water task may be confounded by the loss of thermoregulatory control.

Aging↗
PubMed2002

The reliability of grading the fixation preference test for the assessment of interocular visual acuity differences in patients with strabismus.

PURPOSE: The purpose of this study is to test the reliability of the grading system of standard fixation preference testing compared with the logarithmic scale of the minimum angle of resolution (logMAR) interocular visual acuity difference of patients with manifest strabismus and to test the strength of association between the interocular visual acuity difference and the grade of alternation. METHODS: A total of 111 strabismic patients with large angle heterotropias (> 10 PD) were included in this study. The visual acuities of these patients were determined using the Snellen's, tumbling E, or Lea visual acuity charts as appropriate for the child's age and ability to cooperate. The results were converted to their logarithmic equivalents of minimum angle of resolution or recognition. Fixation preference was graded from 0 to 4 and was evaluated by observing the time-period through which fixation was maintained with the nonpreferred eye. RESULTS: The median value of interocular visual acuity difference for grade 4 was determined as 0.0, grade 3 as 0.097, grade 2 as 0.17, grade 1 as 0.3, and grade 0 as 0.8. The grade of fixation preference was found to be inversely related to the logMAR interocular visual acuity difference (P <.0001). There was a significant difference between every fixation grade except grade 1 and grade 2 (P <.005). CONCLUSIONS: The grades used in fixation preference testing correlate with the logMAR visual acuity differences in strabismic amblyopic patients. However, the grading system does not imply a linear function in terms of visual acuity difference. The difference between the logMAR values of patients with grade 0 and 1 are more profound compared with other grades.

Adolescent↗
PubMed1988

Dynamic visual acuity with telescopic spectacles: improvement with adaptation.

Telescopic spectacles are used as aids for the visually impaired in order to increase effective visual acuity. Because ocular stabilization reflexes are not fully compensatory when telescopic spectacles are worn, head motion would be expected to produce retinal image motion which could decrease visual acuity. Using 1.0 Hz sinusoids of vertical axis head rotation, we investigated the effect of head velocity and telescopic spectacle magnification on binocular dynamic visual acuity (DVA), the acuity during head motion, in 34 normally sighted subjects. The visual field peripheral to the telescopes was masked. Up to a head velocity amplitude of 30 degrees/sec, DVA was insensitive to head velocity for X2 telescopic spectacles. For X4 and, to a greater degree, X6 telescopic spectacles, DVA decreased progressively as head velocity increased. DVA measurements were repeated after a 15 min adaptation period, during which a distant video monitor was viewed using telescopic spectacles. For X4 telescopic spectacles, DVA increased significantly after adaptation. With an unobstructed peripheral visual field, initial DVA with X4 telescopic spectacles was equal to adapted DVA with peripheral vision occluded, but adaptation produced no further improvement in DVA with the peripheral field unobstructed. These data indicate that the visual acuity obtained with telescopic spectacles is substantially reduced under conditions where head motion occurs, potentially reducing the functional value of these devices in low vision rehabilitation. The adverse effect of head motion on DVA may be reduced by adaptation.

Adaptation, Physiological↗
PubMed2003

Visual acuity and its measurement.

Despite its critical importance to our daily life, the most common measurement of visual function, visual acuity, is a relatively crude and narrow one testing only a small portion of the broad range of visual functions. Visual acuity is the measurement of the ability to discriminate two stimuli separated in space at high contrast relative to the background. Clinically, this is measured by asking the subject to discriminate letters of known visual angle. The visual acuity is represented as the reciprocal of the minimal angle of resolution (the smallest letters resolved) at a given distance and at high contrast. Other measurements of visual acuity also exist, including Vernier acuity. Newer charts, such as the ETDRS chart, use letters of equal recognition difficulty and use the log of the minimal angle of resolution; these charts have significant advantages over the old Snellen-type charts. This article reviews visual measurements in children and in patients with low vision, and it reviews factors affecting visual acuity, such as pupil size, refractive error, media opacities, and pharmacologic agents.

Eye Diseases↗
PubMed2002

Retinal detachment in patients with a preexisting glaucoma drainage device: anatomic, visual acuity, and intraocular pressure outcomes.

PURPOSE: To report anatomic, visual acuity, and intraocular pressure (IOP) outcomes after retinal detachment (RD) repair in patients with a preexisting glaucoma drainage device. METHODS: Consecutive case series including patients with a preexisting glaucoma drainage device who underwent RD repair at Bascom Palmer Eye Institute between 1989 and 1999. RESULTS: Ten patients were identified with a mean follow-up of 18 months. Initial RD repair included pars plana vitrectomy (PPV) and fluid-gas exchange in four patients, scleral buckling procedure (SBP) in two, PPV and SBP in three, and pneumatic retinopexy in one. Three patients initially treated with SBP or pneumatic retinopexy developed recurrent RD secondary to proliferative vitreoretinopathy. All patients eventually underwent PPV. At 6 months, the retina was attached in eight patients, and nine patients had an IOP no greater than 21 mmHg. Although postoperative vision was stable or improved compared to preoperative levels in seven patients, visual acuity at 6 months was worse than 2/200 in only four patients, largely because of preexisting advanced glaucoma. CONCLUSIONS: In eyes with RD and a preexisting glaucoma drainage device, PPV with fluid-gas exchange was the most successful approach in achieving retinal reattachment. Although anatomic success is usually achieved and IOP is usually controlled, visual acuity outcomes are often poor, largely because of preexisting advanced glaucoma.

Adolescent↗
PubMed2006

Assessing the impact of visual acuity on quality of life in individuals with type 2 diabetes using the short form-36.

OBJECTIVE: We sought to ascertain quality-of-life measures and utility values associated with visual acuity in type 2 diabetes. RESEARCH DESIGN AND METHODS: The Medical Outcome Study Short Form with 36 items (SF-36) was administered to 4,051 individuals with type 2 diabetes who were enrolled in the Lipids in Diabetes Study, and their best attainable vision was determined using an Early Treatment of Diabetic Retinopathy Study chart, expressed as a LogMAR score. Eight domain scores and a utility value representing an overall quality-of-life score were calculated using predefined algorithms. The associations between quality of life measured and best-eye visual acuity were assessed graphically and by regression analysis. RESULTS: All eight SF-36 domain scores were negatively associated with reduced visual acuity. The impact of lower levels of visual acuity ranged from a decline of 1.3 units for a 0.1-LogMAR increase for physical functioning and 0.6 units in mental health. Regression analysis indicated a negative association (P < 0.001) between utility and reduced visual acuity after controlling for sex, BMI, smoking status, and history of diabetes complications. Patients whose LogMAR scores equated to legally blind had, on average, 0.054 (95% CI 0.034-0.074) lower utility compared with patients with normal visual acuity. CONCLUSIONS: Reduced visual acuity is negatively associated with quality of life. The utility scores estimated here should inform studies quantifying the burden of diabetes and those evaluating potential therapies for treating or preventing diabetic eye diseases.

Aged↗
PubMedDate not supplied

[Table for assessing visual acuity in children].

A table of silhouette patterns meeting the requirements of ISO standard is developed in Russia. The aim of this work was to assess by ISO method the correspondence of visual acuity evaluated by the pattern table to visual acuity evaluated by Landolt rings and select the patterns the recognition of which is most of all similar to recognition of Landolt's rings. Visual acuity was examined by the ISO method in 10 subjects with visual acuity of 1.0. Visual acuity assessed by patterns corresponded to that assessed by Landolt's rings if the examinee was acquainted with all tests. Recognition of patterns was assessed in 22 children aged 3.5-5.5 years. Patterns which were identified in less than 50% cases were excluded from the tables. The proposed table can be used in practical ophthalmology, because the results of visometry using this table are compatible with the results of examination by means of Landolt's rings.

Adolescent↗
PubMed1996

[The comparative study of the macular light threshold in the normal and low visual acuity people].

PURPOSE: To test the macular light threshold (MLT) and the change of macular light sensitivity (MLS) in the normal and low visual acuity people. METHODS: MLT of 93 eyes of the normal and 76 eyes of low visual acuity people was measured with macular threshold test of Humphrey Field Analyzer-640. RESULTS: 1. MLT increases with age, there is a negative correlation between MLS and age 2. MLT of low visual acuity people is significantly higher than that of the normal visual acuity people in the same age group; 3. No significant difference of MLT was found in the four quadrants of visual field in the same age group; 4. No significant difference of MLT was found between male and female. CONCLUSIONS: MLS of the normal visual acuity people is superior to that of the low visual acuity people; MLS decreases with age.

Adult↗
PubMed2000

[Final visual acuity in patients undergoing posterior vitrectomy for Terson's syndrome: a series of 11 cases].

PURPOSE: The purpose of this study was to assess visual acuity after vitrectomy for Terson's syndrome. METHODS: This is a retrospective study of 11 eyes (7 patients), who underwent pars plana vitrectomy between 1996 and 1998. Visual acuity was evaluated at 1, 5 and 12 months. We also report immediate and delayed complications. RESULTS: Initial visual acuity was below 20/200 for 9 patients (81%). Final visual acuity was 20/25. An epiretinal membrane was noticed in two patients during the surgical procedure. Final visual acuity for those two patients was only 20/40 and 20/100. Two patients developed cataract following vitrectomy, one developed an endophthalmitis with good vision recovery. CONCLUSION: Vitrectomy for vitreous hemorrhage in Terson's syndrome after three months follow up is a solution without major risks and has a good visual prognosis. Final visual acuity of patients after vitrectomy for Terson's syndrome is good. However, Terson's complications such as epiretinal membrane and cataract are limiting factors for good visual recovery.

Adult↗
PubMed2000

Quantitative topographic irregularity as a predictor of spectacle-corrected visual acuity after refractive surgery.

PURPOSE: To evaluate a new topographic index called topographic irregularity as a quantitative predictor of corrected vision after refractive surgery. METHODS: We defined topographic irregularity as the summed difference at all points between a topographic refractive corneal power map and its best-fit spherocylinder. We prospectively studied 107 eyes of 107 patients 3 months after a variety of refractive procedures. Topographic irregularity was calculated from topographic maps, and the correlation between topographic irregularity and spectacle-corrected visual acuity was determined using both high-contrast and low-contrast acuity charts. This correlation was compared with correlations for the surface regularity index and the surface asymmetry index. Next, we analyzed 54 of these topographic maps to create a regression scale relating surface regularity index, surface asymmetry index, and topographic irregularity to predict spectacle-corrected visual acuity. This scale was then used to predict spectacle-corrected visual acuity on the remaining 53 postoperative patients. RESULTS: The correlation of topographic irregularity with spectacle-corrected visual acuity (R(2) =.36) was comparable to the correlation for the surface regularity index (R(2) =.36) and stronger than for the surface asymmetry index (R(2) =.11) when spectacle-corrected visual acuity was measured with high-contrast eye charts. Topographic irregularity correlated more strongly with spectacle-corrected visual acuity (R(2) =.42) than either the surface regularity index (R(2) =.28) or the surface asymmetry index (R(2) =.14) when spectacle-corrected visual acuity was measured with low-contrast eye charts. Using the regression scale, prediction of high-contrast and low-contrast spectacle-corrected visual acuity from topographic irregularity was superior to or comparable to predictions using the surface regularity index and the surface asymmetry index. CONCLUSIONS: Topographic irregularity has a closer correlation with spectacle-corrected visual acuity than existing topographic indexes. Topographic irregularity is also an accurate predictor of spectacle-corrected visual acuity and may be a more sensitive tool for evaluating postoperative visual performance than current topographic measures.

Cornea↗
PubMed1978

Fading and feedback in the modification of visual acuity.

Two experiments assessing the modification of visual acuity by fading plus feedback procedures are presented. The training procedure involved a gradual increase of the distance myopic subjects could accurately discriminate letters requiring a minimum of 20/20 vision at approximately 23 feet. In Experiment I experimental and matched control groups of mildly to moderately myopic subjects were compared on repeated Ortho-rater examinations of visual acuity. The experimental group showed a significant improvement relative to the control group who received no training. Multiple-baseline across-stimuli designs were used in Experiment II to evaluate training effects for another group of subjects with moderate to severe myopia. Two measures of acuity were obtained. Accuracy of discrimination of letters at various preselected distances was determined each session while Ortho-rater examinations were given periodically throughout training. Changes in discrimination accuracy over sessions appeared to be related to fading for three of the four subjects, and Ortho-rater acuity changes were observed for each subject. Some short-term maintenance of improved vision was evident on both acuity measures.

Accommodation, Ocular↗
PubMed2006

Relationship between foveal birefringence and visual acuity in neovascular age-related macular degeneration.

PURPOSE: To investigate the relationship between visual acuity and foveal birefringence in patients with neovascular age-related macular degeneration. METHODS: In total, 40 patients with choroidal neovascularization underwent macular imaging with scanning laser polarimetry. Bowtie patterns, typically seen in birefringence images of the macula, were evaluated and classified into three categories: (1) regular bowtie present; (2) bowtie present, but disrupted; and (3) no bowtie present. The relation of the bowtie appearance to the best-corrected logMAR visual acuities was tested (ANOVA). RESULTS: Mean visual acuity was best for the group that had regular bowties (mean logMAR=0.34) and differed statistically significantly from the disrupted bowtie group and no bowtie group (P=0.01 and 0.0007). Ages for the three groups did not differ (P=0.31). CONCLUSIONS: Appearance of a regular bowtie indicates a substantially intact Henle fibre layer with the potential for good visual function, despite the presence of underlying pathology. Conversely, disruption or absence of a bowtie may indicate severe damage to the photoreceptors, consistent with the finding of poorer visual acuity.

Aged↗
PubMed2004

Visual acuity and its decrease in classic neovascular age-related macular degeneration.

PURPOSE: To identify factors affecting visual acuity and its decrease in eyes with subfoveal choroidal neovascularization (CNV) associated with age-related macular degeneration (AMD). METHODS: Distance visual acuity was recorded at screening and up to five follow-up visits during the first year of a randomized, double-blind, placebo-controlled trial of oral prinomastat. Subjects had AMD in both eyes and neovascular AMD in at least one eye. Analysis employed a generalized linear mixed model. RESULTS: Of 158 eligible subjects (age 56-90), 125 (79.1%) received prinomastat. Visual acuity was independently affected by relative acuity of the fellow eye, whether the study eye had been the first or second to develop CNV, age, current smoking, leakage area, and prior photocoagulation. Decrease in visual acuity score, unaffected by prinomastat, was less steep in eyes that had been second to develop CNV. Such eyes had a comparable time since CNV onset to other study eyes. CONCLUSION: Fellow eye features independently affect visual acuity and its decrease in eyes with classic neovascular AMD.

Aged↗
PubMed1995

Long-term follow up of visual acuity in eyes with stage 5 retinopathy of prematurity after closed vitrectomy.

PURPOSE: This study was done to determine the efficacy of closed vitrectomy on long-term visual acuity of stage 5 retinopathy of prematurity. METHODS: We studied the visual acuity of eyes that had undergone retinal reattachment by closed vitrectomy for stage 5 retinopathy of prematurity and were followed up for more than three years. RESULTS: Forty-nine eyes of 31 patients among a total of 71 eyes of 48 consecutive patients were operated on and followed up for more than three years. Retinal reattachment occurred in 29 (59%) of the 49 eyes. Six patients (eight eyes) did not respond to visual acuity testing because of mental retardation or cerebral palsy. Measured visual acuity in the remaining 21 eyes varied from no light perception in one eye, light perception in four eyes, Recognizable hand movement in three eyes, 20/2,000 to 20/200 in seven eyes, 20/200 to 20/25 in five eyes, and 20/25 in one eye. No correlation was seen between visual outcome and factors such as gestational age, birth weight, and configuration of retinal detachment. Markedly better visual acuity was obtained in eyes that underwent initial surgery within four months of birth. CONCLUSIONS: Useful vision can be obtained after reattachment of the retina by closed vitrectomy on some patients who have stage 5 retinopathy of prematurity. Better visual acuity may be obtained by earlier surgery.

Birth Weight↗