Background Image clarity during near work is influenced by several factors,such as accommodative lag,pupil size and monochromatic aberrations.Since image clarity during extended reading at near distance has been cited as a possible inducement of myopia in childhood and a possible difference between myopic and emmetropic people throughout life,it is important to examine these factors in myopic and emmetropic myopic juvenile during reading at near distance. Objective The aim of this study was to investigate the relationships among wavefront aberrations,accommodative response and pupil size in early onset and progressive myopes eyes under the different reading status and explore the possible mechanism of the development of myopia as well. Methods Fiflyseven subjects aged from 12 to 16 years were enrolled and grouped as emmetropes,the onset of myopes and progressive myopes.Reading material were Chinese novels presented by rapid serial visual presentation at a distance of 25 cm. Accommodative response and pupil size were recorded by a Grand Seiko WV-500 autorefractor.The Image J software was used to calculate the pupil diameter.Wavefront aberrations were then measured with a WASCA wavefront analyzer. Results Aberrations and accommodative response showed large inter-subjeet variability.With accommodative stimulus of 4 diopter,the accommodative lag in the early-onset of myopes group and progressive myopes group were ( 1.72 ±0. 53) D and ( 1.74 ±0. 44) D, showing larger value in comparison with ( 0. 96 ±0. 55) D of emmetropes group( t＝4.25 ,t=4.47 ,P<0. 001). However,there were no significant differences in accommodative lag between the early-onset of myopes group and progressive myopes group( t = 0. 18, P>0. 05). The mean value of pupil diameter, total RMS value, high-order RMS value, spherical aberration and coma were all significantly reduced with the stimulus varied from 0 D to 4 D( P<0. 01). However,none of the pupil sizs,total RMS value,high-order RMS value,spherical aberration and coma had significant difference among different refractive groups( P>0. 05). Conclusion The early-onset of myopes and progressive myopes had larger accommodative lag. The lower sensitivity to defocus at near reading distance,inducing the larger accommodative lag and hyperopic defocus may be linked to the developing myopia.

Objective To investigate the geographical distribution of excessive iodine in drinking water and to demarc aI|e the excessive iodine regions in Hebei Province.Methods In 173 counties of Hebei Province, town was surveyed as an elementary unit.Five villages were sampled according to the direction of east,west, south,north,center in every town.If the water sources were more than 5 in a village,water was sampled according to the direction ofeast,west, south,north, center, respectively;If the water sources were less than 5 in a village, all were sampled:If the village used water of cental supply,only one sample wag collected.Arsenic-cerium catalysis was used to determine the iodine concentration of drinking water.Results Two thousands and forty-nine towns were investigated and 19 352 water samples were determined in Hebei Province.One hundred and seventy- two towns were confirmed to be excessive iodine areas,where the range of water iodine Wag 0.1～2840.4μg/L The water 8amDle with 18 358 had a water iodine median less than 150.0μg/L The areas with water iodine median less than 150.0μg/L,in between 150.0μg/L and less than 300.0μg/L,and equal to or more than 300.0 μg/L accounted for 94.86%,2.92%and 2.22%,respectively.There were 110 towns with water iodine median being between 150.0μg/L and iess than 300.0 μg/L and 62 towns with water iodine median equal to or more than 300 gμ/L.Exeessive iodine towns distributed in 33 counties of 6 cities involving 5 854 960 residents in'Hebei Provmce. MOBt of the water sources with excessive iodine Cangzhou were deep wells and there was a positive correlation between we depth and water iodine concentration (r=0.430,P<0.01), while they were shallow wells in Handan, Xingtai.Hengshui,and no correlation was found between well depth and water iodine concentration(r=-0.060,-0.119.-0.121,P>0.05).Conclusions Six cities have excessive iodine water resotlrees in Hebei Province, mostly in Handan.xingtai,Hengshui and Cangzhou Cities,which all are low-lying land.The water with excessive iodine is hypogene,and the towns with excessive iodine water distributein patchy or spot pattern.

Objective To analyze the therapeutic effect and prognosis according to a new CT classification of traumatic posterior occipital epidural hematomas (POEH). Methods We classified the CT presentation of 104 patients with POEH by sinus transverses: type Ⅰ hematomas were defined as up-sinus transverses; type Ⅱ hematomas were defined as sub-sinus transverses and type Ⅲ hematomas were defined as straddling sinus transverses. The above types were divided into unilateral or bilateral subtypes. Bone flap craniotomy through a median posterior approach was performed in patients with unilateral hematoma adjacent to the midline. Bone flap craniotomy through a median suboccipital approach was adopted for patients with bilateral middle occipital hematoma. Results Type Ⅰ enjoyed mild symptoms, good curative effect and low mortality rate (7%). Type Ⅱ and Ⅲ had serious symptoms and high mortality rate (13.3%, 16.6%, respectively). Conclusion The classification of the CT presentation of POEH is helpful in confirming the diagnosis, drawing up the scheme of treatment and judging the prognosis.