RT Book, Section
A1 Lueder, Gregg T.
SR Print(0)
ID 56151785
T1 Chapter 30. Disorders of the Lens
T2 Pediatric Practice: Ophthalmology
YR 2011
FD 2011
PB The McGraw-Hill Companies
PP New York, NY
SN 9780071633802
LK accesspediatrics.mhmedical.com/content.aspx?aid=56151785
RD 2024/04/18
AB The  lens  is  the  normally  clear  structure  that  is  located  just  posterior  to  the  iris.  The  primary  function  of  the  lens  is  to  focus  light  rays  on  the  retina.  The  lens  is  attached  to  the  ciliary  body  by  zonules.  These  zonules  produce  tension  in  response  to  contraction  of  the  ciliary  muscle.  The  ciliary  muscle  is  circular,  so  that  when  it  contracts  its  diameter  becomes  smaller  (Figure  30–1).  This  decreases  the  tension  on  the  lens  zonules,  and  the  lens  becomes  more  spherical.  This  is  known  as  accommodation,  which  is  what  allows  the  eye  to  focus  at  near.  As  people  age,  the  lens  becomes  progressively  stiffer.  Because  of  this,  the  ability  to  focus  at  near  gradually  deteriorates,  to  the  point  that  almost  all  people  require  reading  glasses  during  the  fourth  decade  of  life.