Grating and Recognition Acuities of Pediatric Patients

Acuities for gratings obtained by preferential looking (PL) that differed from expectations based upon the ophthalmologic examination prompted this study. Older pediatric patients (124 patients; mean age, 6.5 years) were tested by the PL grating test and a test of recognition acuity (pictures or letters). On the average, grating acuity was better than recognition acuity. In patients with dense amblyopia or foveal abnormalities, very large discrepancies between grating and recognition acuities were found. In nonamblyopic patients, acuities were no more discrepant than for children with normal eyes. Amblyopia was less dense by grating acuities than by recognition acuities; grating acuities were sensitive, however, to refractive and organic amblyopia but not to strabismic amblyopia. Possible explanations include the heterogeneity of patients' eye disorders, single vs. linear acuity, stimulus size and relative complexity of stimuli. These results can aid in evaluating PL grating acuities of preverbal patients, and suggest modifications of stimuli to investigate amblyogenesis.     

Modified Allen pictures to assess amblyopia in young children

To produce a test of visual acuity for young children that is more sensitive to amblyopia than current preschool vision tests, the authors surrounded four Allen pictures with "crowding" bars. This modified Allen test was evaluated by measuring acuity of amblyopic children (n = 28) and children (n = 10) and adults (n = 5) with normal eyes. Mean acuities of amblyopic eyes for the modified pictures was 0.8 octaves or nearly three logMar Snellen lines poorer than for the isolated pictures. For nonamblyopic and normal eyes modified picture acuity averaged 0.1 to 0.4 octaves poorer than isolated picture acuity. Average acuities of amblyopic eyes (n = 22) for the modified pictures agreed with line letter acuities. These results suggest that the modified picture test induces contour interaction similar to that of line letter tests, and thus, is a more sensitive test of amblyopia in the preschool child than isolated symbols.     

Small and large field grating acuity versus recognition acuity in different groups of amblyopic patients

Grating acuity was tested in 74 subjects with different amblyopia and five patients with pathological morphological findings, reducing visual acuity. Recognition acuity was tested with Landolt C single symbol and close inter-space 2.6 min. of arc. Grating acuity was tested with the Teller Acuity Cards with large (12.5 cm × 12.5 cm) and small (6.25 cm × 6.25 cm) test fields. Reduction of field size did not cause any significant difference. Patients with strabismic or strabismic and anisometropic amblyopia did not show a close correlation of recognition acuity with grating acuity. Stimulus deprivation amblyopia showed a good correlation between grating acuity (large and small field) and Landolt single optotype acuity. In children at risk for amblyopia, a difference in favour of large field gratings was found for both eyes (risk and non-risk eye) in the lower visual acuity group (identical with the lower age group). Better grating acuity for large fields seems to reflect an early stage of the visual development rather than that it is indicative for amblyopia.     

Assessment of young amblyopes. Array vs. single picture acuities

A linear array of intact and "jumbled" symbols suitable for testing young children has been used to evaluate 35 young amblyopes. Acuities with the jumbled array test were poorer than those obtained with single symbols: the discrepancy between the jumbled array and single picture acuities was greater for large acuity deficits than small deficits. The depth of amblyopia, indexed by the interocular difference in acuity, was greater for the jumbled array than single pictures. For the patients who could be tested with lines of Snellen letters the jumbled array acuities were closer to line letter acuities than single picture or grating acuities. These results suggest that the jumbled array provides a more sensitive test of amblyopia in young children than single symbols or gratings, possibly because the jumbled array presents contour interactions that exploit the crowding phenomenon.     

Grating and recognition acuities of young amblyopes.

The visual acuities of 36 young amblyopes were determined by (a) conventional recognition tests (near and distance) and (b) an adapted grating acuity card procedure. Considerable agreement between the estimates of acuity obtained with each method was demonstrated, which was generally less than, or equal to, the mean difference between adjacent Snellen lines (4.5 c deg-1). Estimates of grating acuity obtained with vertical gratings did not differ significantly from those obtained with horizontal gratings. There was no difference between the subjects' ability to detect the grating (acuity) and accurately to discriminate target orientation (horizontal or vertical). The results of the experiment are discussed in relation to previous findings of a discrepancy between grating and recognition acuities in amblyopia, and the clinical use of the acuity card procedure.     

Predictive value of teller Acuity Card Test (TACT) and comparison of recognition and grating acuities in premature children with and without residua of Retinopathy of Prematurity (ROP)

BACKGROUND: The aim of the study was to evaluate the predictive value of grating acuity as measured by the TAC Test (TACT) at the age of 6 months corrected age and to compare grating and recognition acuities in eyes with and without ROP residua at an age of three to seven years. PATIENTS AND METHODS: The development of visual acuity between 6 months and 3 - 7 years (4.5 years median) was evaluated in 87 eyes of 44 premature children born between the 24 th and 36 th week of gestation, with a birthweight ranging from 550 to 2580 g. Thirteen eyes reached threshold: ROP disease and underwent cryocoagulation. Grating acuity was measured with the TACT at 6 months corrected age and every half year up to three to seven years (median 4.5 years). Recognition acuity was measured with the Sheridan-Gardiner Test (SGT) at 4.5 years (median). TACT-results at 6 months corrected age and 3 - 7 years were compared for the group of patients with normal posterior pole and patients with ROP residua. Furthermore, SGT scores and TACT scores were compared at the 4.5 years follow-up. A visual acuity of >/= 0.1 (3 cy/ degrees ) and >/= 0.4 (13 cy/ degrees ) was considered favourable at the age of 6 months corrected age and 3 - 7 years, respectively. RESULTS: The TACT scores ranged from < 0.03 to 0.2 (< 1.0 to 6.5 cy/ degrees ) at 6 months and from < 0.05 to 2.0 (< 1.6 to 57 cy/ degrees ) at 3 - 7 years. In 77 % of cases the TACT scores at 6 months had predictive value for the further TACT scores and in 78 % for the optotype acuity. There was no difference between eyes with normal posterior pole and eyes with ROP residua concerning the predictive value of non favourable optotype acuity. CONCLUSIONS: Testing grating acuity at 6 months corrected age allows to roughly predict both grating and recognition acuities at the age of 3 - 7 years. No difference between patients with normal posterior pole and patients with ROP residua was found.     

Central and peripheral contrast sensitivity in amblyopia with varying field size

The purpose of the present study was to establish the extent of the amblyopic deficit at 0°, 10°, and 20° retinal eccentricity using contrast sensitivity measures for sine wave gratings subtending various field sizes. Contrast sensitivity functions were shown to vary with stimulus field size, retinal location and degree of amblyopia. Foveally, peak contrast sensitivity of amblyopic eyes increased markedly with increasing field size, to reach the same magnitude as that of the contralateral non-amblyopic eyes for large fields. Peripherally, peak contrast sensitivity remained lower in the amblyopic eyes for all field sizes examined. High spatial frequency cut-offs were reduced both centrally and peripherally with all field sizes in the amblyopic eyes. The effect of increasing field size on the cut-off acuity was found to be smaller than the effect on-peak contrast sensitivity.The most significant conclusions drawn from the results are that: (1) The amblyopic deficit in terms of both peak contrast sensitivity and acuity isnot restricted to the central foveal region; and (2) amblyopic eyes benefit to a greater extent from increased stimulus field size than non-amblyopic eyes in terms of peak contrast sensitivity.A model is proposed which suggests that the results obtained are due to fewer and/or less sensitive cortical neurons being driven by the amblyopic eye in humans with naturally occurring amblyopia.Supported in part by NEI grant R01EY01728 from the National Eye Institute, NIH, Bethesda, Maryland     

Optotype and grating visual acuity in preschool children

PURPOSE: To investigate the contribution of stimulus and response differences to the different developmental courses of grating and optotype visual acuity at the preschool age range. METHODS: Binocular visual acuity at 228 cm was assessed in 205 children in 7 age groups between 2.5 and 6 years and in 12 adults. Acuities were obtained in three tasks: detection of a grating in one of two positions, discrimination of the orientation of a single grating, and discrimination of the orientation of the gap in an uncrowded Landolt-C optotype. The three paradigms were as similar as possible in stimulus contrast, luminance, presentation mode, and psychophysical procedure. RESULTS: Mean grating and optotype acuities were lower than adult acuities at all ages. Optotype acuity was overall higher and increased faster with age than grating acuities. Grating orientation acuity was slightly but not significantly lower than grating detection acuity in all but one age group. The grating detection task was successful at earlier ages (100% at 3.5 years) than both the optotype acuity task (100% at 4.5 years) and the grating orientation task (100% at 5.75 years). CONCLUSIONS: Optotype and grating acuities follow a different developmental course in children between 3 and 6 years of age, with optotype acuity growing superior to grating acuity in that age range. The similarity of grating orientation to grating detection acuities and the difference between grating and optotype acuities suggest that superior optotype acuity is due to stimulus characteristics rather than to the complexity of the response required.     

A simple grating visual acuity test for impaired children

Twenty-five developmentally delayed or neurologically impaired nonverbal children, aged 2 to 15 years, referred for visual acuity assessment, were beyond the age at which standard preferential-looking techniques are considered to be effective and none could be tested with Snellen letters, illiterate Es, or Allen pictures. Our method, in which the children learn to point to grating stimuli, enabled us to obtain monocular visual acuity estimates in 19 of the 25 patients. When indicated, patching therapy was begun and was monitored with this method. Similar testing of 31 unimpaired children showed good prediction of recognition visual acuities except in patients with visual acuities worse than 20/160. The grating method accurately identified or excluded amblyopia in 26 of 31 children (84%). We consider this a clinically useful test of visual acuity in nonverbal impaired children.     

The relationship between indoor and outdoor Snellen visual acuity in cataract patients

One hundred six cataractous eyes of 78 patients were evaluated to examine the relationship between indoor and outdoor Snellen visual acuity. While 81 of all cataractous eyes (76.4%) had Snellen visual acuities of 20/40 or better when tested indoors, only 33 eyes (31.2%) had 20/40 or better Snellen visual acuities when tested outdoors facing the sun. When tested indoors, only three eyes (2.8%) had Snellen visual acuities worse than 20/80, while 31 eyes (29.2%) had outdoor Snellen visual acuities worse than 20/80. Ten eyes (9.4%) had outdoor Snellen visual acuities worse than 20/200. Seventy-four eyes (69.8%) had outdoor visual acuities that were at least two Snellen lines worse than those measured indoors and 23 eyes (21.7%) had outdoor visual acuities that were at least five Snellen lines worse. The median difference between indoor and outdoor visual acuity was three Snellen lines. The need for increased precision in the ability to assess outdoor "real world" vision while in the ophthalmologist's examination room is discussed. Clearly, indoor Snellen visual acuity alone is insufficient to evaluate functional visual impairment in cataract patients.     

Visual outcome in infants with cicatricial retinopathy of prematurity

Monocular grating acuities of preterm infants with retinopathy of prematurity (ROP) were measured using a forced-choice preferential-looking (FPL) procedure. Eyes were independently graded by a retinal specialist and/or pediatric ophthalmologist and assigned to anatomic outcome categories on the basis of cicatricial residua of ROP. Eyes assigned to the normal/regressed and peripheral retinal changes categories (n = 120) had normal posterior poles. The authors found that grating acuities in this group were slightly lower than those of age-matched healthy full-term infants, even when infants with amblyogenic or neurologic conditions were eliminated from the analysis. Grating acuity of eyes assigned to the macular ectopia, macular fold, partial detachment, or total detachment outcome categories (n = 60) had abnormal posterior poles, and grating acuity of these eyes was significantly related to anatomic outcome category (P less than 0.001). Follow-up data from subsets of eyes at 6 months, 12 months, or 2-5 yr after the initial acuity test suggest that early FPL acuity tests may be predictive of long-term functional outcome (r = 0.75-0.87).     

Assessment of acuity of amblyopic subjects using face, grating, and recognition stimuli

For amblyopic subjects, square-wave gratings, such as those used in preferential looking tests of infants' vision, yield more optimistic estimates of visual acuity than complex stimuli such as letters. A complex stimulus--a schematic face pattern--has recently been shown (Harris et al, IOVS 25:782, 1984) to permit preferential looking estimates of acuity of infants with normal eyes. In the present study, older amblyopic subjects had acuities measured with the face stimulus as well as gratings and standard recognition tests. Acuities measured with the face stimulus agreed better with the results of the standard recognition tests than did those obtained with gratings. Thus, if amblyopia of infants and young children affects spatial vision in a manner similar to that of older children and adults, one would anticipate that complex stimuli, such as the face pattern, would complement current assessments of young pediatric patients.     

Vernier acuity of normal and visually deprived cats

This study examines the relationship between grating and vernier acuity in cats that were either normally reared, unilaterally amblyopic as a result of a period of monocular deprivation, or bilaterally amblyopic resulting from a period of reverse occlusion followed by binocular visual experience. Vernier acuity was assessed on a jumping stand by use of a vernier-grating stimulus similar to that devised for use with human infants. The vernier thresholds for normal cats were 1.2-1.3 min arc, values that were approx. 6 times better than their grating acuity, and hence may represent a true hyperacuity. By contrast, the vernier acuity of the visually deprived cats were substantially below normal (19-83 min arc). The vernier thresholds for the deprived eye of the monocularly deprived cat and both eyes of the reverse occluded cats had fallen to the point where they were at best equal, and sometimes worse than the corresponding grating acuity. This pattern of results is similar to those observed in some types of human amblyopia, where vernier acuity also no longer represents a hyperacuity, and where in severe cases the thresholds may be worse than grating acuity.     

An automated visual acuity testing computer program using the Apple II system

We developed an automated visual acuity testing program that uses an E optotype with surrounding confusion bars. The computer software program runs on Apple II equipment and a black-and-white monitor with a five-inch screen. The program is available in response box and joystick versions. The test is suitable for children older than 31/2 to 4 years of age and for adults. A t-test on the same floppy disk as the visual acuity programs is used to test the probability that the differences in test results are greater than chance. Visual acuities of 20 normal subjects were reduced by means of plus lenses. Test-retest acuity correlation coefficients were similar for letter charts and computer-generated E optotypes, suggesting approximately equal reliability under the test conditions employed. Visual acuities of 12 amblyopic eyes were obtained by a Ferris-type letter chart and computer-generated E optotypes. The correlation coefficient was +0.93, suggesting similar test results by these two methods.     

Monocular acuity in preschool children: Assessment with the Teller and Keeler acuity cards in comparison to the C-test

The development of monocular grating acuity was studied in 210 children between 1 and 6 years using Teller Acuity Cards (TAC). 95 of these children were also tested with the Keeler Acuity Cards (KAC). Monocular visual acuity measured with the TAC showed a gradual increase from 8.4 to 32.4 c/deg for 7 to 79 month-olds and with the KAC from 14.5 to 31.4 c/deg for 19 to 78 month-olds. Mean visual acuity at 6 years was still 0.5-1.0 octave lower than grating acuity in adults. The results of 95 children tested with TAC and KAC did not indicate any significant differences between the acuity scores obtained with the two tests. Stimulus configuration of the TAC did not result in overestimation of acuity in children 1-6 years of age. In 141 older children (39-79 months), the TAC test was compared with a recognition test (C-test). Children between 3 and 5 years of age reached significantly lower acuities with the C-test than with the TAC. The C-test showed a higher sensitivity for unconnected refractive errors than the acuity card tests.     

Theories of Binocular Vision after Aguilón

The development of monocular grating acuity was studied in 210 children between 1 and 6 years using Teller Acuity Cards (TAC). 95 of these children were also tested with the Keeler Acuity Cards (KAC).

Monocular visual acuity measured with the TAC showed a gradual increase from 8.4 to 32.4 c/deg for 7 to 79 month-olds and with the KAC from 14.5 to 31.4 c/deg for 19 to 78 month-olds. Mean visual acuity at 6 years was still 0.5–1.0 octave lower than grating acuity in adults.

The results of 95 children tested with TAC and KAC did not indicate any significant differences between the acuity scores obtained with the two tests. Stimulus configuration of the TAC did not result in overestimation of acuity in children 1–6 years of age.

In 141 older children (39–79 months), the TAC test was compared with a recognition test (C-test). Children between 3 and 5 years of age reached significantly lower acuities with the C-test than with the TAC. The C-test showed a higher sensitivity for unconnected refractive errors than the acuity card tests.     

Albino spatial vision as an instance of arrested visual development

Adult albinos and human infants share a number of common visual characteristics: both have low grating acuity, both lack a foveal pit (foveal hypoplasia), and both have much lower central cone densities than in the normal adult. We have explored the consequences of these characteristics by measuring both spatial and temporal contrast sensitivity in the central retina and by comparing central and peripheral grating and vernier acuities in two young adult albino subjects. To compensate for nystagmus, horizontally oriented patterns were employed. Both subjects had normal flicker sensitivities, but their central grating and vernier acuities were approximately five times worse than normal. At 10.0 degrees in the inferior visual field, however, vernier and grating acuities were normal for both subjects. Finally, the ratio of grating to vernier acuity in albino central vision fell within the normal foveal range, suggesting that albino central vision does not resemble the adult periphery. These results are consistent with the hypothesis that spatial processing deficiencies in albino central vision are a direct consequence of the increased spacing of their central cones. Our data are comparable to available psychophysical results obtained from infants of approx. 10 months of age, thus suggesting that the albino visual system may represent a case of arrested development.     

弱视患者多焦视网膜电图的研究

目的　探讨弱视患者多焦视网膜电图 (mfERG)的改变和视网膜的损害。方法　对 2 8例屈光参差性弱视患者 (A组 )、2 5例斜视性弱视患者 (B组 )、14例屈光不正性弱视患者 (C组 )行mfERG检测 ,记录总体和不同视野区域的一阶、二阶反应N1波、P1波的振幅密度和潜时 ,并与正常对照者 (D组 )进行比较。结果　A、B、C组mfERG的一阶反应P1波、N1波和二阶反应P1波的振幅密度均降低 (P <0 0 5 ) ,且这种改变在视野中央明显 ,随偏心度的增加而减少。 4组mfERG均表现颞侧视野一阶反应P1波、N1波振幅密度较鼻侧视野降低 ,且潜时延长 (P <0 0 5 ) ;上方视野二阶反应P1波振幅密度均低于下方视野 (P <0 0 5 ) ,其余指标上、下方视野差异无显著意义 (P >0 .0 5 )。A、B、C组各阶反应波的潜时与D组比较 ,差异均无显著意义 (P >0 0 5 )。弱视患者视力与mfERG指标之间无线性相关关系 (P >0 0 5 )。A、B组中健眼mfERG指标与患眼比较 ,差异均有显著意义 (P <0 0 5 ) ;与D组比较 ,差异无显著意义 (P >0 0 5 )。结论　弱视患者mfERG有明显改变 ,提示弱视眼视网膜神经节细胞受损 ,但神经信息的传递无延长。     

Grating visual acuity using the preferential-looking method in elderly nursing home residents

PURPOSE: To assess the performance of two approaches to visual acuity testing in a group of nursing home residents with cognitive impairment. The study was a cross-sectional comparison of the effectiveness of two tests of visual acuity. METHODS: Nursing home residents participating in a clinical trial were tested with both recognition acuity charts and grating acuity cards (Teller) by masked observers. RESULTS: Of the nursing home residents (n = 656) who participated in the study, 86% could respond to visual acuity testing in at least one eye. Eighty-four percent were testable using Teller cards versus 73% who were testable by Early-Treatment Diabetic Retinopathy Study (ETDRS) charts or Lea symbol charts. Forty-one percent of individuals with MiniMental Status Examination (MMSE) scores lower than 10 were testable by recognition acuity, whereas 61% were testable with grating acuity cards. Grating acuity correlated well with recognition acuity (R = 0.79; 95% CI, 0.75-0.98, intraclass correlation coefficient [ICC]). The correlation was slightly lower in individuals with decreased MMSE scores. Although grating acuity was one line better than recognition acuity on average and median acuities were the same, 24% of individuals had results that differed by three or more lines. CONCLUSIONS: Teller acuity cards can effectively test the vision in cognitively impaired individuals who are not testable by conventional means. Grating acuity results correlated well with those of recognition acuity, although differences of three or more lines were not uncommon. Wider use of grating acuity testing allows a more complete assessment of visual function in the cognitively impaired elderly.