Environmental factors in school classrooms: How they influence visual task demand on children.

BackgroundThe key visual factors in a classroom environment include the legibility, angle subtended at the eye, illumination, contrast, and colour of the visual task. The study evaluated the visual environmental factors in the school classrooms.Materials and methodsThe distance Visual Acuity (VA) demand was evaluated based on the size of visual task i.e. the smallest size of chalkboard writing and its viewing distance. The environmental factors which can have an effect on the visibility in classrooms such as illuminance on the chalkboard and at student's desk, chalkboard contrast, light sources and the student's perception of their classroom visual environment were measured. To quantify the distance VA demand and to compare with a standard high contrast VA chart measure, a validation of the measurements was performed by chalkboard simulation experiment. The "acuity reserve" to be included to the measured distance VA demand was evaluated.ResultsWe included twenty-nine classrooms of eight schools. The median distance VA threshold demand was 0.28 logMAR(0.25,0.45). The median illuminance on front desk position and chalkboard contrast was 130 lux(92,208) and 40(36,50) respectively with 62% classrooms having low illumination (ConclusionThe study findings highlight the increased visual task demand in school classrooms and the need for appropriate seating arrangements in classrooms based on the visual acuity of children. The study emphasises regular audit of the classroom environment along with the school eye screening

Do school classrooms meet the visual requirements of children and recommended vision standards?

<div><p>Background</p><p>Visual demands of school children tend to vary with diverse classroom environments. The study aimed to evaluate the distance and near Visual Acuity (VA) demand in Indian school classrooms and their comparison with the recommended vision standards.</p><p>Materials and methods</p><p>The distance and near VA demands were assessed in 33 classrooms (grades 4 to 12) of eight schools. The VA threshold demand relied on the smallest size of distance and near visual task material and viewing distance. The logMAR equivalents of minimum VA demand at specific seating positions (desk) and among different grades were evaluated. The near threshold was converted into actual near VA demand by including the acuity reserve. The existing dimensions of chalkboard and classroom, gross area in a classroom per student and class size in all the measured classrooms were compared to the government recommended standards.</p><p>Results</p><p>In 33 classrooms assessed (35±10 students per room), the average distance and near logMAR VA threshold demand was 0.31±0.17 and 0.44±0.14 respectively. The mean distance VA demand (minimum) in front desk position was 0.56±0.18 logMAR. Increased distance threshold demand (logMAR range -0.06, 0.19) was noted in 7 classrooms (21%). The mean VA demand in grades 4 to 8 and grades 9 to 12 was 0.35±0.16 and 0.24±0.16 logMAR respectively and the difference was not statistically significant (p = 0.055). The distance from board to front desk was greater than the recommended standard of 2.2m in 27 classrooms (82%). The other measured parameters were noted to be different from the proposed standards in majority of the classrooms.</p><p>Conclusion</p><p>The study suggests the inclusion of task demand assessment in school vision screening protocol to provide relevant guidance to school authorities. These findings can serve as evidence to accommodate children with mild to moderate visual impairment in the regular classrooms.</p></div

Utility values associated with diabetic retinopathy in Chennai, India.

PURPOSE: The aim of this study was to estimate utility values associated with different severity stages of diabetic retinopathy (DR) in India by a direct elicitation method (time-trade off, TTO) and indirectly by questionnaire. METHODS: People with diabetes aged 40 years and over were recruited from an on-going DR epidemiology study and a laser clinic in Chennai, India. Utility values were elicited using the direct TTO method and indirectly through a validated questionnaire (EQ-5D). RESULTS: Of 249 participants, 30 had no DR, 73 had non-proliferative DR, 114 had sight-threatening DR, and 32 were blind from DR (bilateral visual acuity <6/60). The mean TTO utility value was 0.73 (standard deviation, SD, 0.31). TTO utility values decreased with increasing severity of DR (p < 0.001) and were significantly lower among participants with sight threatening DR (0.70, SD 0.33) and blindness (0.55, SD 0.24) compared to those with no DR (0.89, SD 0.25) after adjustment for sociodemographic and clinical factors. Blindness from DR was independently associated with a lower EQ-5D utility value. The utility value derived from EQ-5D (0.06) associated with being blind from DR was substantially lower than that of the TTO utility value (0.55). CONCLUSIONS: This study provides estimates of utility values that can be used in economic evaluations of DR screening strategies in India. The relatively low utility values associated with blindness highlights the importance of screening programs for early detection of the sight-threatening stages to prevent vision loss from DR in this setting

Are children with low vision adapted to the visual environment in classrooms of mainstream schools?

Purpose: The study aimed to evaluate the classroom environment of children with low vision and provide recommendations to reduce visual stress, with focus on mainstream schooling. Methods: The medical records of 110 children (5–17 years) seen in low vision clinic during 1 year period (2015) at a tertiary care center in south India were extracted. The visual function levels of children were compared to the details of their classroom environment. The study evaluated and recommended the chalkboard visual task size and viewing distance required for children with mild, moderate, and severe visual impairment (VI). Results: The major causes of low vision based on the site of abnormality and etiology were retinal (80%) and hereditary (67%) conditions, respectively, in children with mild (n = 18), moderate (n = 72), and severe (n = 20) VI. Many of the children (72%) had difficulty in viewing chalkboard and common strategies used for better visibility included copying from friends (47%) and going closer to chalkboard (42%). To view the chalkboard with reduced visual stress, a child with mild VI can be seated at a maximum distance of 4.3 m from the chalkboard, with the minimum size of visual task (height of lowercase letter writing on chalkboard) recommended to be 3 cm. For 3/60–6/60 range, the maximum viewing distance with the visual task size of 4 cm is recommended to be 85 cm to 1.7 m. Conclusion: Simple modifications of the visual task size and seating arrangements can aid children with low vision with better visibility of chalkboard and reduced visual stress to manage in mainstream schools

Categorization of desk positions and the minimum and average distance visual acuity demand (Mean±SD (range)) at different desk positions in 33 classrooms.

<p>Categorization of desk positions and the minimum and average distance visual acuity demand (Mean±SD (range)) at different desk positions in 33 classrooms.</p

Comparison of variables in measured 33 classrooms to the Indian Government standard recommendations.

<p>Comparison of variables in measured 33 classrooms to the Indian Government standard recommendations.</p

Box plot representing the comparison of minimum distance visual acuity demand at different desk positions (front, middle and last row) between grades 4 to 8 and grades 9 to 12.

<p>Box plot representing the comparison of minimum distance visual acuity demand at different desk positions (front, middle and last row) between grades 4 to 8 and grades 9 to 12.</p

Average letter size, viewing distance and visual acuity demand, and comparison between different grades (grade 4 to 8 and grade 9 to 12 group) and schools (n = 8) in 33 classrooms.

<p>Average letter size, viewing distance and visual acuity demand, and comparison between different grades (grade 4 to 8 and grade 9 to 12 group) and schools (n = 8) in 33 classrooms.</p

Mathematical notations.

<p>Mathematical notations.</p

Schematic of the multi-drop protocol for the measurement of epithelial permeability.

<p>At t = 0, a 0.35% fluorescein drop (0.35 gm of fluorescein/100 mL PBS buffer) is instilled on the bulbar conjunctiva and the tear fluorescence is measured (shown by red unfilled circles). After clearance of the dye (usually < 15 min), two drops of 2% fluorescein (2 gm of fluorescein/100 mL PBS buffer) are instilled 10 min apart (T₁ and T₂). About fifteen minutes after the second drop, the ocular surface is washed with CMC solution (carboxymethyl cellulose solution; Blue arrow). Next, stromal fluorescence is measured 3–4 times at time T_s (usually within 5–10 min after T₃). AUC_dL1 and AUC_dL2, which are assumed to be equal, are estimated based on the area under the curve calculated for the 0.35% drop (AUC*). The tear fluorescence in response to the probe drop is fitted to a single-exponential decay to determine F⁰_dp and k_d. F⁰_dp is then used to estimate F⁰_dL1 and F⁰_dL2. k_d for the 2% drops is assumed to be the same as that for the 0.35% drop. Hence, the first 0.35% drop is referred to as the probe drop. The 2% drops have been employed to load the stroma with measurable levels of fluorescein so that noise-free measurements of the stromal accumulation can be obtained. Therefore, the 2% drops are referred to as the loading drops.</p