视近物时，晶状体变凸的原因是（ ）。

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SQL Error: select id,body,options from ***_enewstiku where sourceid='30911' and id < 2487463 and id<>'2487463' order by id desc limit 5 SQL Error: select id,body,options from ***_enewstiku where sourceid='30911' and id > 2487463 and id<>'2487463' order by id asc limit 5