Standard Logarithmic Visual Acuity Research Articles

Association between elevated light levels in classrooms and change in vision acuity among elementary and secondary students

To explore the association between elevated light levels in classrooms and change in vision acuity among elementary and secondary students. A total of 4 elementary (grade 1-5) and secondary (grade 7-8) schools in urban and rural areas in Sujiatun, Shenyang, China were selected by cluster sampling as experimental schools, and lighting systems have been rebuilt to improve the ambient light levels in 56 classrooms in November 2012. The control schools were chosen for the comparable academic burden and adjacent location to experimental schools, 4 schools in all. Cluster sampling of all students in the selected schools as the subjects was carried out. A total of 2 092 students were chosen as experimental group and 1 595 students were in the control group. The luxmeter was used to measure illuminance of classrooms in two groups at baseline, and intervention for 1 month, respectively.Students in both groups were underwent 3 times for vision acuity examination by standard logarithmic visual acuity chart at baseline, intervention for 6 month and intervention for 1 year, respectively. The light levels of desk and blackboard in two groups were compared by Wilcoxon test. Multivariate analysis of covariance with repeated measures was performed to assess three vision acuity results between groups. After intervention, the average illuminance of desk (117.5 vs 532.5 lx, Z = -5.38, P < 0.001) and blackboard (75.6 vs 423.5 lx, Z = -5.38, P < 0.001) and uniformity of desk (Z = -4.28, P < 0.001) with new lighting were improved significantly than that with old lighting, however the uniformity of blackboard was lower than baseline significantly (0.64 vs 0.70, Z = -2.34, P = 0.019). The average scores of vision acuity in students at baseline, intervention for 6 month and intervention for 1 year were 4.87 ± 0.23, 4.84 ± 0.25 and 4.85 ± 0.23 in experimental group, and 4.88 ± 0.22, 4.84 ± 0.25 and 4.81 ± 0.27 in control group, respectively. The significant differences between groups were found and F values were 1.41, 0.13, 19.99, P values were 0.235,0.724, <0.001. At last the average vision acuity in experimental group were significantly better than that in control group either among elementary (4.90 ± 0.20) vs (4.87 ± 0.21) score, F = 13.61, P < 0.001 or secondary students (4.73 ± 0.28) vs (4.68 ± 0.32) score, F = 14.25, P < 0.001. Visual acuity loss could be decreased in students with elevated light levels which may slow the response to myopiagenic stimuli for eyes, therefore the ambient light levels of blackboard and desk in classroom should be improved.

A new specialized visual acuity chart for amblyopic children aged 3-5 years old: development and its clinical applications.

To introduce a new specialized visual acuity chart for amblyopic children aged 3-5 years old and its clinical applications. The new visual acuity chart and notations were designed based on Weber-Fechner law. The optotypes were red against a white background and were specially shaped four basic geometric symbols: circle, square, triangle, and cross. A regular geometric progression of the optotype sizes and distribution was employed to arrange in 14 lines. The progression rate of the optotype size between two lines was 1.2589 and the testing distance was 3m. Visual acuity score could be recorded as logMAR notation or decimal notation. Age-stratified diagnostic criteria for amblyopia established by consensus statement on diagnosis of amblyopia (2011) among members of the Strabismus and Pediatric Ophthalmology Group, Ophthalmology Society, Chinese Medical Association (SPOGOSCMA) were illustrated in the new visual acuity chart. When assessing visual acuity in children aged 3-5 years old, this new visual acuity chart that consists of four symmetrical shapes (triangle, square, cross, and circle) overcame an inability to recognize the letters of the alphabet and difficulties in designating the direction of black abstract symbols such as the tumbling 'E' or Landolt 'C', which the subjects were prone to lose interest in. The visual acuity score may be recorded in different notations: decimal acuity and logMAR. These two notations can be easily converted each other in the new eye chart. The measurements of this new chart not only showed a significant correlation and a good consistency with the international standard logarithmic visual acuity chart (r=0.932, P<0.01), but also indicated a high test-retest reliability (89% of retest scores were within 0.1logMAR units of the initial test score). The results of this study support the validity and reliability of distance visual acuity measurements using the new eye chart in children aged 3 to 5 years over a wide range of visual acuities, and the new eye chart is great for early detection of amblyopia. It can be applied in various clinical settings.

Visual acuity evaluated by pattern-reversal visual-evoked potential is affected by check size/visual angle

To systemically explore the range of visual angles that affect visual acuity, and to establish the relationship between the P1 component (peak latency ~100 ms) of the pattern-reversal visual-evoked potential (PRVEP) and the visual acuity at particular visual angles. Two hundred and ten volunteers were divided into seven groups, according to visual acuity as assessed by the standard logarithmic visual acuity chart (SLD-ii). For each group, the PRVEP components were elicited in response to visual angle presentations at 8°, 4°, 2°, 1°/60', 30', 15', and 7.5', in the whiteblack chess-board reversal mode with a contrast level of 100% at a frequency of 2 Hz. Visual stimuli were presented monocularly, and 200 presentations were averaged for each block of trials. The early and stable component P1 was recorded at the mid-line of the occipital region (oz) and analyzed with SPSS 13.00. (1) oz had the maximum P1 amplitude; there was no significant difference between genders or for interocular comparison in normal controls and subjects with optic myopia. (2) The P1 latency decreased slowly below 30', then increased rapidly. The P1 amplitude initially increased with check size, and was maximal at ~1° and ~30'. (3) The P1 latency in the group with visual acuity ≤0.2 was significantly different at 8°, 15' and 7.5', while the amplitude differed at all visual angles, compared with the group with normal vision. Differences in P1 for the groups with 0.5 and 0.6 acuity were only present at visual angles <1°. (4) Regression analysis showed that the P1 latency and amplitude were associated with visual acuity over the full range of visual angles. There was a moderate correlation at visual angles <30'. Regression equations were calculated for the P1 components and visual acuity, based on visual angle. (1) Visual angle should be taken into consideration when exploring the function of the visual pathway, especially visual acuity. A visual angle ~60' might be appropriate when using PRVEP components to evaluate poor vision and to identify malingerers. (2) increased P1 amplitude and decreased P1 latency were associated with increasing visual acuity, and the P1 components displayed a linear correlation with visual acuity, especially in the range of optimal visual angles. Visual acuity can be deduced from P1 based on visual angle.

ND1 G3635A mutation in the mitochondrial DNA in three Chinese pedigrees of Leber's hereditary optic neuropathy

Objective To screen mitochondrial DNA mutations in 3 Chinese pedigrees with Leber's hereditary optic neuropathy (LHON) carrying the ND1 G3635A mutation. Methods88 members (53maternal relatives and 35 paternal relatives)in 3 pedigrees were enrolled. The ophthalmologic examinations were performed for all members, including visual acuity (standard logarithmic visual acuity charts), fundus photography (Canon fundus camera), visual field (Humphrey Visual Field Analyzer), color vision (Yu zhiping color vision plate), and visual evoked potentials (Roland Consult RETI port gamma, flash VEP).16 members had LHON, 72 members did not have LHON. 135 healthy people from Wenzhou were included as the control group. Genomic DNA was extracted from peripheral blood leukocytes of all subjects. G3635A mutation was screened by PCR-amplification of mitochondrial DNA for all subjects. Mitochondrial haplotypes and other mutations in the entire mitochondrial genome were also determined by PCR using 24pairs of primers for the probands. ResultsAnalysis of mitochondrial DNA (mtDNA) in 3 pedigrees revealed the presence of ND1 G3635A mutation in 3 probands and all maternal relatives, but not in paternal relatives and healthy controls. Proband's haplogroup belong to East Asia group N9a3, D4, and R11a. In addition to the G3635A mutation, probands also had other variants including 12 variants in D-loop region, 6variants in RNA gene, and 36 variants in protein-encoding gene. ConclusionsG3635A mutation was identified in probands and maternal relatives of 3 pedigrees of LHON. It showed that G3635A mutation was the pathogenic molecular basis for those patients. Key words: Optic atrophy, hereditary, Leber/etiology; DNA, nitochondrial; Mutation