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A popular and widely used method of visual acuity testing of young children is criticized on the grounds that it often fails to elicit amblyopia. The results obtained when the visual acuity of thirty amblyopic children was tested by different methods show that monotype testing gives an apparent acuity averaging three grades better than those derived from the standard Snellen's test.
Refractive amblyopia may occur as a unilateral or bilateral condition. Although bilateral refractive amblyopia may account for 1 to 2% of all refractive amblyopia, there is little consistent information in the literature regarding isoametropic amblyopia resulting from bilateral hyperopia. Hence, this retrospective study investigated the prevalence of reduced aided acuity in patients aged 10 years and younger (mean age 3.97 years) with 5 D or more of isometropic hyperopia and considered the following factors that may influence visual acuity: (1) age at first correction; (2) magnitude of hyperopia; and (3) duration of refractive correction of the hyperopia. The results indicate that the majority of patients (87%) have aided acuity poorer than 6/6 at initial correction of refractive error. However, if the full hyperopic correction was worn for 1 year or longer, only 43% of these patients demonstrated acuity poorer than 6/6 and none showed acuity poorer than 6/12. The magnitude of the hyperopia appeared to have the greatest influence on the visual acuity outcome both at initial correction of refractive error and 1 year or longer after correction. Duration of correction also influenced the visual acuity outcome, but to a lesser extent than the magnitude of refractive error. In contrast, the age of first correction showed little correlation with visual acuity either at the time of first refractive correction or after a minimum of 1 year of correction.
BACKGROUND: Pixel nonlinearity of a cathode-ray tube (CRT) display can cause differences between the actual image and the nominal image. One of the discrepancies, the anisotropy of interactions between neighboring pixels on the same raster line and between neighboring raster lines, may have an impact on the CRT-based visual acuity test where small horizontal and vertical gaps are used. We evaluated this impact. METHOD: Two high-quality color CRT monitors were tested. The stimulus target was a black square ring on a white background. White gaps of one stroke width were opened in the middle of the straight sides of the square ring. In a gap width comparison study, the up and down gaps were flanked with a one-pixel band on the left and right side. The pixel value of the bands was varied to determine the luminance that made up and down gaps appear to have the same width as left and right gaps. The comparison was made at 1 and 2 m. In a visual acuity study, horizontal gap (left/right) acuity and vertical gap (up/down) acuity were measured separately at several distances between 8 and 11 m. Similar measurements were made when the monitor was rotated 90 degrees. RESULTS: Gaps with edges that were parallel to raster lines (raster-parallel gaps) appeared wider than gaps with edges that were perpendicular to raster lines (raster-perpendicular gaps). To match the apparent width of the left and right gaps, the two one-pixel bands flanking the up and down gaps required a pixel value that corresponded approximately to a luminance of mid gray, indicating that the apparent width of a four-pixel left or right gap was similar to that of a five-pixel up or down gap. Raster-parallel gaps produced a higher percentage of correct responses than raster-perpendicular gaps in a visual acuity test. When nominal gap widths were equal, left and right gaps produced 10% or more correct responses than up and down gaps at some target sizes, which translated to a two-letter acuity difference. This acuity difference could not be accounted for by uncorrected astigmatism because the anisotropy persisted when the monitor was turned 90 degrees. CONCLUSIONS: Pixel nonlinearity of a CRT-display results in an anisotropy of gap width that can be observed at and above visual acuity size. This anisotropy may introduce uncertainties in the results of CRT-based visual acuity tests where gaps of different orientations are used.
Examination of orbit size and optic foramen size in living primates reveals two adaptive phenomena. First, as noted by many authors, orbit size is strongly correlated with activity pattern. Comparisons of large samples of extant primates consistently reveal that nocturnal species exhibit proportionately larger orbits than diurnal species. Furthermore, nocturnal haplorhines (Tarsius and Aotus) have considerably larger orbits than similar-sized nocturnal strepsirrhines. Orbital hypertrophy in Tarsius and Aotus accommodates the enormously enlarged eyes of these taxa. This extreme ocular hypertrophy seen in extant nocturnal haplorhines is an adaptation for both enhanced visual acuity and sensitivity in conditions of low light intensity. Second, the relative size of the optic foramen is highly correlated with the degree of retinal summation and inferred visual acuity. Diurnal haplorhines exhibit proportionately larger optic foramina, less central retinal summation, and much higher visual acuity than do all other primates. Diurnal strepsirrhines exhibit a more subtle but significant parallel enlargement of the optic foramen and a decrease in retinal summation relative to the condition seen in nocturnal primates. These twin osteological variables of orbit size and optic foramen size may be used to draw inferences regarding the activity pattern, retinal anatomy, and visual acuity of fossil primates. Our measurements demonstrate that the omomyiforms Microchoerus, Necrolemur, Shoshonius, and Tetonius, adapiform Pronycticebus, and the possible lorisiform Plesiopithecus were likely nocturnal on the basis of orbit diameter. The adapiforms Leptadapis, Adapis, and Notharctus, the phylogenetically enigmatic Rooneyia, the early anthropoids Proteopithecus, Catopithecus, and Aegyptopithecus, and early platyrrhine Dolichocebus were likely diurnal. The activity pattern of the platyrrhine Tremacebus is obscure. Plesiopithecus, Pronycticebus, Microchoerus, and Necrolemur probably had eyes that were very similar to those of extant nocturnal primates, with a high degree of retinal summation and rod-dominated retinae. Leptadapis and Rooneyia likely had eyes similar to those of extant diurnal strepsirrhines, with moderate degrees of retinal summation, a larger cone:rod ratio than in nocturnal primates, and, more speculatively, well-developed areae centrales similar to those of diurnal strepsirrhines. Adapis exhibited uncharacteristically high degrees of retinal summation for a small-eyed (likely diurnal) primate. None of the adapiform or omomyiform taxa for which we were able to obtain optic foramen dimensions exhibited the extremely high visual acuity characteristic of extant diurnal haplorhines.
BACKGROUND AND OBJECTIVE: This study reports and compares the anatomic and visual acuity outcomes of patients treated with either thermal laser photocoagulation or photodynamic therapy for circumscribed choroidal hemangioma with associated serous retinal detachment. PATIENTS AND METHODS: Retrospective, consecutive, interventional case series of patients treated for symptomatic circumscribed choroidal hemangioma. RESULTS: Thirteen of 23 patients (57%) treated with thermal laser photocoagulation exhibited complete resolution of subretinal fluid, 6 (26%) had partial resolution of subretinal fluid, and 4 (17%) had persistent subretinal fluid despite therapy. At 3 months posttreatment, visual acuity was improved in 6 (26%), stable in 13 (57%), and worsened in 4 (17%) of 23 patients. All 5 patients who underwent photodynamic therapy had complete resolution of subretinal fluid. At 3 months posttreatment, visual acuity improved in 4 (80%), remained stable in 1 (20%), and worsened in 0 (0%) patients. CONCLUSIONS: Photodynamic therapy shows similar if not better anatomic and visual acuity results than thermal laser photocoagulation when treating symptomatic circumscribed choroidal hemangioma.
PURPOSE: The long-term evolution of diabetic maculopathy and visual acuity and their risk factors in patients with newly diagnosed Type 2 diabetes and in control subjects. METHODS: A 10-year prospective study consisting of a representative group of 133 (70 men, 63 women) newly diagnosed Type 2 diabetic patients diagnosed at health centers between 1979 and 1981 and 144 (62 men, 82 women) non-diabetic control subjects recruited from the population register. The frequency of maculopathy was determined by grading of 45 degrees fundus photographs and fluorescein angiograms. The subjects were studied at baseline and after 5 and 10 years. RESULTS: The frequency of maculopathy in Type 2 diabetic patients was low at the time of diagnosis but increased sharply after 5 years of the disease and at the 10-year examination 21% of diabetic patients had signs of maculopathy. By the 10-year follow-up the visual acuity declined more markedly in the diabetic patients than in the control subjects. Poor glycaemic control was the most important predictive factor for the development of maculopathy as well as deterioration of visual acuity. CONCLUSIONS: In newly diagnosed patients with Type 2 diabetes one-fifth had developed maculopathy which deteriorated their visual acuity. Poor glycaemic control was the most important predictor of maculopathy.
Twenty-six mentally retarded children and young adults, most of them with severe neurological deficits, in the age range 5-24 years, were examined ophthalmologically, and their binocular visual acuities were tested with 'operant preferential looking' according to the technique of Mayer & Dobson (1980). Five of the subjects did not co-operate sufficiently for visual testing, although 3 had no ocular abnormalities that would affect binocular acuity. The visual acuity levels determined with 'preferential looking' ranged from 1.29 to 0.03 in the 21 subjects that could be tested. Two children with high myopia showed substantial increase in acuity with appropriate correction (from 0.1 to 1.06 in one child and from 0.05 to 0.31 in the other). Inability to fixate light or objects was found in subjects, who at acuity testing showed values of 0.15 or less. In patients with suspected or definite optic atrophy, visual acuities 0.28 or less were obtained. In general there was a good correlation between ophthalmological abnormalities (in fixation, pupil reactions to light, ocular motility, fundus appearance and refraction) and poor visual acuity. It is therefore concluded that visual acuity testing with 'preferential looking' techniques can give valid information on central visual function in mentally retarded children and young adults.
The prevalence of good visual acuity following surgery for congenital unilateral cataract was examined in a group of patients seen between 1980 and 1986. Overall, 53% of patients obtained linear distance acuities of 20/80 or better by 3 to 7 years of age. The best outcomes followed surgery during the first two months of life, prompt lens fitting, aggressive occlusion therapy, and regular follow-up. Nonetheless, aphakic eyes did not achieve a visual acuity of 20/20 in the sample. Prospective "preferential-looking" data demonstrated a failure of aphakic eyes to keep pace with the normal developmental course after 18 months of age. Poor visual outcomes following late surgery appear to be due primarily to the development of amblyopia during the first months of life, which may aggravate compliance problems and further deteriorate prospects of visual rehabilitation.
PURPOSE: A detailed understanding of overall quality of vision may help primary care physicians, optometrists, and general ophthalmologists to improve the care of patients with choroidal neovascularization (CNV) resulting from age-related macular degeneration (AMD). METHODS: Published literature was reviewed using Medline searches and the authors' knowledge of the field. RESULTS: Both visual acuity and contrast sensitivity are strongly associated with the ability to perform vision-related activities of daily living. CNV resulting from AMD often leads to scotoma, which is also strongly associated with the ability to perform everyday activities such as reading and driving. Contrast sensitivity and visual field extent may be better predictors of many abilities than visual acuity. Laser photocoagulation, verteporfin therapy, and pegaptanib sodium have been proven to reduce the risk of visual acuity loss in patients with CNV resulting from AMD. Laser photocoagulation frequently causes scotoma, but data on its effects on other aspects of overall quality of vision are scarce. Verteporfin therapy has been shown to also reduce the risk of contrast sensitivity loss and has been associated with stabilization or reduction of scotoma size. Treatment effects beyond visual acuity have not been investigated for pegaptanib. Detailed assessment of overall quality of vision also aids the design of vision rehabilitation programs tailored to the needs of individual patients. CONCLUSIONS: Understanding the impact of vision loss on patients with CNV resulting from AMD and assessing treatment benefits requires assessment of overall quality of vision. Primary care physicians and optometrists have an important role in ensuring that patients receive the best possible care, which can be aided by prompt referral to an ophthalmologist or retina specialist and collaboration with low-vision specialists and optometrists who together can make detailed assessments of overall quality of vision, implement appropriate treatment, and design effective rehabilitation strategies.
Teller Acuity Cards are a new "preferential looking" procedure for the evaluation of visual acuity in newborns and infants. We used this test to assess, longitudinally, visual acuity in 60 healthy term newborns followed up from birth to two years of age. In order to have a set of comparison parameters for use in studies of newborns at risk of developing visual system impairment, the relative maturational curve was plotted. The acuity values of our sample are in line with those reported by other authors in the literature and they represent the first set of such data referring to a group of healthy term newborns in Italy. This paper provides a visual acuity curve for the first two years of life obtained from healthy term newborns, a curve which could prove useful for reference when this technique is used on newborns at risk of developing neurological and especially visual problems.
AIM: To evaluate factors influencing change in visual acuity (VA) after intravitreal injection of triamcinolone acetonide as treatment of exudative age related macular degeneration (AMD). METHODS: This prospective, interventional, comparative non-randomised clinical case series study included 94 patients (99 eyes) showing progressive exudative AMD with occult (n = 61 eyes), minimally classic (n = 18), predominantly classic (n = 1), or totally classic (n = 8) subfoveal neovascularisation. Mean follow up was 8.5 (SD 4.7) months (median, 7.3 months; range 3.1-24.5 months). All patients received an intravitreal injection of 20-25 mg of triamcinolone acetonide. RESULTS: An increase in best VA of at least one line on the Snellen charts was found in 63 (63.1%) eyes. Correspondingly, mean VA increased significantly (p<0.001) from 0.17 (SD 0.13) to 0.22 (SD 0.17) after the injection. Postoperative increase in VA was significantly (p<0.001) and negatively correlated with preoperative VA (correlation coefficient, -0.49). Gain in visual acuity was significantly (p = 0.009) higher if preoperative visual acuity was less than 0.08 (gain: 3.2 (SD 2.9) Snellen lines) than if preoperative VA ranged between 0.08 and 0.20 (gain: 1.2 (SD 2.2) Snellen lines). Change in VA was significantly (p = 0.016) less if preoperative VA was higher than 0.20 (change: -0.8 (SD 3.4) Snellen lines). Maximal gain in VA was significantly (p = 0.035) larger in eyes with retinal pigment epithelium detachment than in eyes with minimally classic subfoveal neovascularisation. This was statistically independent of age (p = 0.99), refractive error (p = 0.88), sex (p = 0.92), and duration of follow up (p = 0.46). CONCLUSIONS: Gain in VA after intravitreal injection of 20-25 mg of triamcinolone acetonide is significantly and negatively correlated with preoperative VA. It is significantly larger in eyes with retinal pigment epithelium detachment than in eyes with minimally classic subfoveal neovascularisation.
The course of ocular disease can be monitored by the assessment and measurement of a number of visual functions. In the clinical situation, visual acuity and color discrimination are obvious and simple functions to assess. The relationship between color vision and visual acuity in eye disease has generally been discussed only in qualitative terms. This paper examines the correlation between visual acuity and color discrimination for a number of subjects exhibiting varying degrees of severity of senile macular degeneration.
Two behavioral techniques--OKN and PL--have been used to test visual acuity in young infants in both laboratory and clinical settings. Clinically, OKN is used widely by ophthalmologists as an informal, subjective estimate of an infant's visual status. However, the difficulty of the judgments required and the problem of obtaining good OKN gratings that can be used at a near enough distance to maintain an infant's attention make the procedcure less than ideal. The PL procedure has been used much more widely in laboratory testing than has the OKN procedure, probably because the grating stimuli used are smaller and easier to obtain than OKN stimuli and because the judgments required of the observer necessitate only comparison of the infant's looking behavior in the presence of two stimuli, rather than judgments concerning the presence or absence of a behavior. However, it is only recently that PL procedures, in the form of the diagnostic stripes procedure, have been introduced into clinical settings for measurement of acuity. To date, the diagnostic stripes procedure has proved to be a rapid and practical test to carry out in the clinic, and it appears to be effective in diagnosing infants with ophthalmic problems that would be expected to interfere with vision tested binocularly. However, whether the procedure will be more useful than a standard pediatric or ophthalmic examination for screening infants for visual problems has yet to be determined. In addition, the treatment implications of early detection of poor visual acuity cannot yet be known. To be a truly useful test, a procedure that assesses visual acuity in infants should have prognostic or treatment value--neither of which has been clearly established for the OKN or the PL procedure. The problem is a circular one. We do not know the value of developing tests of visual acuity in infants because the treatment implications and prognostic value of early detection have not yet been established. However, knowledge of the value of early treatment is useless unless early detection is possible. Now that the cycle is beginning to be broken through development of techniques for early detection of poor acuity, research into the prognostic and treatment value of early diagnosis becomes possible for the first time. In conclusion, a number of researchers are working on the development of behavioral techniques for measurement of visual acuity in infants. Whether or not these procedures can be helpful clinically depends on what visual problems can be identified with each technique in the clinic, and whether or not it will turn out to be useful to identify these visual problems at such an early age, a question that can only be answered by further clinical and laboratory observations.
PURPOSE: To study the relation between changes in visual acuity, fixation stability and the retinal area covered by hard exudates 3, 6 and 12 months after laser photocoagulation for diabetic maculopathy. METHODS: Twenty-four eyes of 24 patients with diabetes mellitus were examined 3, 6 and 12 months after retinal photocoagulation for clinically significant macular oedema. Each examination included visual acuity testing (ETDRS charts), quantification of fixation stability using a scanning laser ophthalmoscope (Rodenstock 101) and fundus photography. The fundus photographs were digitised and the retinal area covered by hard exudates determined by image processing. RESULTS: The retinal area covered by hard exudates decreased significantly during the first 6 months after treatment ( P=0.05, paired t-test), but increased again between 6 and 12 months after treatment. The visual acuity showed an increase, albeit non-significant, during the first 6 months after treatment followed by a decrease between 6 and 12 months after treatment. Quantification of fixation stability showed that four patients with central exudates fixated at the border of these lesions, and in two of these patients the disappearance of the exudates resulted in increased visual acuity and a change in fixation to the former exudate area. CONCLUSIONS: The retinal area covered by hard exudates decreases during the first 6 months after central photocoagulation, but increases again between 6 and 12 months after the treatment. Hard exudates covering the foveal region contribute to disturbance of central vision.
The Night Vision Aid is a photomultiplier device developed by International Telephone and Telegraph Co. (ITT) and the Retinitis Pigmentosa Foundation as a mobility aid for those with night blindness. The purpose of this study was to measure visual acuity with and without the Night Vision Aid at a variety of light levels to determine how much visual assistance it provided over a wide range of illuminations. Ten normal subjects and five patients with retinitis pigmentosa (RP) used the aid at nine luminance levels ranging from 10(-6) to 10(2) ml. With the device, visual acuity improved at light levels below 0.1 ml and target visibility was extended about 3 log units further into low luminance. At light levels above 0.1 mL, unassisted visual acuity was better in all normal and most RP subjects. The best visual acuity attained with the Night Vision Aid was 6/15 (20/50). Graphs and dark adaptation curves illustrate our findings.
Reproducible measures of refraction and visual acuity are necessary in clinical and population studies of eye diseases. Inter-observer differences in measurements of these parameters were evaluated using the Early Treatment of Diabetic Retinopathy Study (ETDRS) protocol. No clinically significant interobserver variation was found for refraction or visual acuity measurements between three observers. This study confirms that when standardized measurement procedures are used, observer differences as a source of variability in the data can be minimized.
In persons with congenital nystagmus (CN), the ability to integrate visual information over time can be limited by two factors--the duration of foveation periods and the temporal integration period of the visual system. The purpose of this study was to assess the relative importance of these two factors for visual acuity for targets of different luminances. We measured visual acuity using Landolt C targets at 5 luminance levels (50 to 0.005 cd/m2) in 6 observers with CN, and in 6 normal observers with comparable motion of the retinal image. To allow comparison, normal observers viewed the targets during image motion simulating jerk CN, with "foveation durations" ranging from 20 to 160 ms. In the normal observers, acuity improves as a function of the simulated foveation duration at all luminance levels. However, this improvement is larger and occurs at a faster rate at high than at low luminances. The more gradual improvement in acuity with simulated foveation durations at low luminances is consistent with a prolongation of the temporal integration period, which we estimate to range from approximately 140 to 380 ms over the 4 log unit range in luminance that we tested. In observers with CN, the change in acuity with luminance is similar, but not identical, to that in normal observers when the duration of the foveation periods is matched. We conclude that the integration of visual information may be limited by either the period of temporal integration or the duration of the foveation period in persons with CN, depending upon which is shorter at the luminance level under consideration.
OBJECTIVE: To examine the efficacy of phacoemulsification (Phaco) versus extracapsular extraction (ECCE) on visual acuity. METHODS: 9 cases related with Phaco and ECCE were retrieved from PubMED and Chinese biomedical data base. The combinability of the studies was assessed in terms of clinical and statistical criteria. Treatment effect was measured as risk difference between phacoemulsification and extracapsular extraction. Pooled estimates were analyzed with computer according to a random-effects model. RESULTS: A total of 1192 patients were included in 9 trials. The pooled risk differences of visual acuity 0.5 or better after surgery one week or 3 month were 24% (95% CI is 10% - 37%), 20% (95% CI is 14% - 25%) respectively. The complications extracapsular extraction rates (36.8%) of phacoemulsification was lower than extracapsular extraction (62.1%). CONCLUSIONS: Phacoemulsification is a safer and reliable surgery for restoration of visual acuity in patients with cataract, and is superior to extracapsular cataract extraction.