182

able  because  the  iris  of  infauU  is  naturally  so  much
nearer  to  the  cornea  than  in  the  adult  subject  that  there  is
much  greater  risk  of  wounding  it  when  the  pupil  is  unex-
panded,  than  in  performing  the  same  operation  upon  older
individuals,  the  pupil  being  in  the  same  condiliou  of
moderate  contraction. If  operating  upon  a  patient  for
the  cure  of  congenital  cataract  at  any  period  before  one
and  between  six  and  about  thirty  years  old,  we  may,  u  i
general  rule,  perform  the  posterior  operation  of  solatioD,
but,  if  operating  before  the  infant  is  six  years  old  and
afler  he  is  a  year  old,  we  may  select  the  anterior  operation
of  solution  as  better  adapted  to  meet  all  the  circumstances
of  the  case. When  the  disease  is  allowed  to  continue  and
become  converted  into  the  mere  capsular  variety  of  cata-
ract— the  lens  being  absorbed,  the  united  capsules  being
tough,  and  much  tliickened — and  in  every  case  in  which  a
tough  portion  of  capsule  alone  exists,  whether  it  has
acquired  adhesions  to  the  iris  or  othemise,  a  different
mode  of  procedure  will  be  required. If  we  endeavour  to
divide  or  separate  it  from  its  morbid  or  natural  connexions,
wc  shall  fail  in  our  attempts,  or  otherwise  increase  the
annoyance  of  the  patient  by  rendering  tliat  a  floating  and
irritating,  which  was  previously  a  fixed  and  unirritating,
substance. To  this  condition  of  disease  the  mode  of
operating  so  clearly  described  by  Mr. Gibson,*  is  peco-


*  Practical  Obtervatiotu  on  the  exlractioH  of  membrmneous  etiitmcH
through  a  puncture  in  the  cornea^  j-r. London,  1811. The  opinkmiof
GiBfiON  appear  to  have  lH>cn,  in  a  certain  degree,  anticipated  bf
Wf.nzel. Referring  to  secondary  capsular  cataract,  he  lemaib,
**  whctlicr  the  opacity  of  the  capsule  bo  occasioned  by  one  or  the  olhff
nf  these  operations,  the  needle  is  inadequate  to  the  purpose  of  lonor-
ing  it,  and  cflccting  a  cure ;  because,  though  it  m^-  be  imffident  to
puncture  this  membrane,  vet,  when  punctured,  the  sides  of  the  cunk
ran  in  no  way  be  removed  by  the  needle  from  their  first  position,  ini
nf  course,  will  still  inlcrcepi  the  rays  of  light. It  is  not  impossible
that  they  may  again  unite. Tlicrc  remains,   therefore,  no  oibcr


183

liarly  well  adapted. 