Student-led screening of school children for refractive error correction

Purpose: Detection and correction of uncorrected refractive errors among 12 million children is an overwhelming task for the 500 currently available eye-care professionals in Nepal. A mid-term review of VISION 2020 goals in Nepal has recommended utilizing alternative human resources that could screen children for visual impairment. This study was conducted to assess the validity of vision screening of school children by trained high school students when compared to optometrist testing as the gold standard.

Methods: A total of 150 students were selected, based on their merit by the headmasters of 25 schools in Nepal and trained for two days by optometrists to screen visual acuity of their peers. Visual acuity ≤ 6/12 in either eye was referred as abnormal vision. A random sample of 1,209 screened students was selected and their visual acuity was reassessed by optometrists under the same settings adopted by trained students. Using optometrist scores as the gold standard, screening results of trained students were analyzed for validity.

Results: Mean age of screened students was 12.2 ± 3.03 years (range: 4–19 years) and 57.4% of them were female. Sensitivity of vision screening test done by trained students was 81.7% and the specificity was 97.6%. A positive predictive value of the test was 77.3% and negative predictive value was 98.2%.

Conclusions: With high sensitivity and specificity values, vision screening done by trained students is effective for screening visual acuity of school children. Countries with limited eye-care professionals and infrastructures can effectively train and utilize students for timely detection of poor vision among children.     

Loss of miR-29b following acute ischemic stroke contributes to neural cell death and infarct size

Glutathione depletion and 12-lipoxygenase-dependent metabolism of arachidonic acid are known to be implicated in neurodegeneration associated with acute ischemic stroke. The objective of this study was to investigate the significance of miR-29 in neurodegeneration associated with acute ischemic stroke. Neural cell death caused by arachidonic acid insult of glutathione-deficient cells was preceded by a 12-lipoxygenase-dependent loss of miR-29b. Delivery of miR-29b mimic to blunt such loss was neuroprotective. miR-29b inhibition potentiated such neural cell death. 12-Lipoxygenase knockdown and inhibitors attenuated the loss of miR-29b in challenged cells. In vivo, stroke caused by middle-cerebral artery occlusion was followed by higher 12-lipoxygenase activity and loss of miR-29b as detected in laser-captured infarct site tissue. 12-Lipoxygenase knockout mice demonstrated protection against such miR loss. miR-29b gene delivery markedly attenuated stroke-induced brain lesion. Oral supplementation of α-tocotrienol, a vitamin E 12-lipoxygenase inhibitor, rescued stroke-induced loss of miR-29b and minimized lesion size. This work provides the first evidence demonstrating that loss of miR-29b at the infarct site is a key contributor to stroke lesion. Such loss is contributed by activity of the 12-lipoxygenase pathway providing maiden evidence linking arachidonic acid metabolism to miR-dependent mechanisms in stroke.     

Temperature distribution in selective laser-tissue interaction

Selective photothermal interaction using dye enhancement has proven to be effective in minimizing surrounding tissue damage and delivering energy to target tissue. During laser irradiation, the process of photon absorption and thermal energy diffusion in the target tissue and its surrounding tissue are crucial. Such information allows the selection of proper operating parameters such as dye concentrations, laser power, and exposure time for optimal therapeutic effect. Combining the Monte Carlo method for energy absorption and the finite difference method for heat diffusion, the temperature distributions in target tissue and surrounding tissue in dye enhanced laser photothermal interaction are obtained. Different tissue configurations and dye enhancement are used in the simulation, and different incident beam sizes are also used to determine optimum beam sizes for various tissue configurations. Our results show that the algorithm developed in this study could predict the thermal outcome of laser irradiation. Our simulation indicates that with appropriate absorption enhancement of the target tissue, the temperature in the target tissue and in the surrounding tissue can be effectively controlled. This method can be used for optimization of lesion treatment using laser photothermal interactions. It may also provide guidance for laser immunotherapy in cancer treatment, since the immunological responses are believed to be related to tissue temperature changes.