Myopic LASIK is less effective in correcting astigmatism when astigmatism is mainly located at the internal optics. Topography and refractive value should be incorporated in the treatment of patients when a significant amount of internal optical astigmatism is detected preoperatively.
Recovery of corneal sensitivity began 1 month after LASEK and was completed by 3 months in eyes treated for low-moderate myopia and at 6 months in eyes with high myopia. The depth of ablation during surgery affected the recovery of corneal sensitivity.
The key step is improved the national standards-the molybdoantimonyarsenate blue spectrophotometric method for the determination of arsenic content in tin smelting waste residue. The experimental results show that on the basis of GB/T 1819.5-2004, the reaction acidity instead 2.0mol/L, tartaric acid 10mL, coloration in water bath 20min, then colorimetric at wavelength of 850nm are the optimal conditions for determination. Using three samples of tin slag smelting arsenic verification of these conditions, precision and accuracy are good, the relative standard deviations are 0.91%、1.35%、1.07%, the recoveries are 100.01%、99.73%、99.98%, respectively.
PurposeTo explore the relationship between ablation parameters of myopic laser surgery and measurement area of wavefront aberration (WA) with Hartmann-Shack wavefront sensor.Methods58 subjects undergone myopic laser surgeries and 74 uncorrected myopic subjects were enrolled in this experiment. The laser ablation parameters were obtained from surgical records, which included spherical error (Rx), depth, and optical zone (OZ) of ablation. The measured area of WA was tested by the WASCA, and the real pupil size was tested by Pentacam. The corneal eccentricity (E value) and curvature was also measured with the Pentacam. All the measurements were performed under mydriatic condition.ResultsFor uncorrected myopic eyes, the measured area of WA was similar with the real pupil size. But for the corrected eyes, the measured area of WA was smaller than the real pupil size with a mean difference of 0.66 ± 0.54 mm for moderate myopia (t = 6.45, p < 0.0001) and 1.76 ± 0.55 mm for high myopia (t = 18.92, p < 0.0001), but not for mild myopia. The Rx (t = -3.20, p = 0.0017), OZ (t = 64.4, p < 0.0001) and postoperative corneal E value (t = 2.52, p = 0.017) were the independent factors of measured area of WA. Measured area of WA = -0.81*Rx + 1.13*OZ + 0.49*postoperative corneal E value (r2 = 0.997).ConclusionsThe WASCA has a limitation in measuring wavefront aberration over the whole pupil area when it’s used for patients received myopic laser surgery. The measured area is smaller than the real pupil size and depends linearly on ablation depth, optical zone and corneal eccentricity.
<div class="ftSection"><span class="ftInlineSubsectionTitle">Purpose:</span><p>To evaluate whether accommodation has effects on eye elongation.</p></div><div class="ftSection"><span class="ftInlineSubsectionTitle">Methods:</span><p>Two hundred seventy-three eyes with a refractive error between +1.0 and −0.5 diopters were divided into three groups: pre-school children, grade-school children, and middle-school children. Ocular structures were measured using autorefraction and A-scan ultrasonography.</p></div><div class="ftSection"><span class="ftInlineSubsectionTitle">Results:</span><p>There was a negative correlation between age and corneal power (r = −0.227, <italic>P</italic> = .0001), lens thickness (r = −0.263, <italic>P</italic> = .00001), and Gullstrand lens power (r = −0.452, <italic>P</italic> << .0001). There was a positive correlation between age and axial length (r = −0.432, <italic>P</italic> << .0001) and vitreous chamber depth (r = 0.505, <italic>P</italic> << .0001). Mean corneal power (<italic>P</italic> < .001) and lens power (<italic>P</italic> < .001) were significantly greater in pre-school children than in grade-school children, whereas axial length (<italic>P</italic> < .001) and vitreous chamber depth (<italic>P</italic> < .001) were greater in grade-school children. Mean lens thickness (<italic>P</italic> = .01) and lens power (<italic>P</italic> = .07) were higher in grade-school children than in middle-school children, whereas axial length (<italic>P</italic> = .024) and vitreous chamber depth (<italic>P</italic> < .001) were higher in middle-school children.</p></div><div class="ftSection"><span class="ftInlineSubsectionTitle">Conclusion:</span><p>Ocular structures may play different roles in maintaining emmetropia. Accommodation during near work and its potential attendant hyperopic defocus could potentially drive eye elongation.</p></div>
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