point spread function ( psf ) is used to define the quality of a retinal image .
when an eye is looking at a point source , the luminance distribution on the retina is called the psf .
the visual acuity corresponds to the central part of the psf ( 0~1  min of arc ) , and the outer part of the psf ( > 1 ) is the straylight .
straylight is caused by light that enters the eye and is scattered rather than focused on the retina .
straylight can create a veil of light over the retina , which can lead to halo , glare , hazy vision , and night blindness while driving [ 2 , 3 ] .
the cornea , iris , sclera , retina , and lens are the five major sources that contribute to intraocular straylight .
changes in intraocular straylight after cataract surgery are mainly caused by intraocular lenses ( iols ) .
although advances in iol design have improved postoperative visual outcomes , patients often complain of reduced contrast and glare after cataract surgery . a recent study on european drivers showed large variations in straylight values in pseudophakic eyes .
the iol material should be considered in studying the influence of intraocular straylight on pseudophakic eyes .
this study aims to determine whether there are differences among pmma , hydrophilic acrylic , and hydrophobic acrylic iols in perceived intraocular straylight .
patients who underwent cataract extraction with iol implantation may complain about dysphotopsia , entopic phenomena , and photic phenomena .
furthermore , we want to assess the differences among the various iol materials when the pupil is dilated with the iol edge exposed .
the c - quant straylight meter proposed by van den berg offers a convenient technique that uses the compensation comparison method .
moreover , cervio and guber both showed that c - quant possesses excellent reliability and high reproducibility [ 11 , 12 ] .
all the procedures followed the tenets of the declaration of helsinki and were approved by the local ethics committee .
we certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research .
seventy - six eyes of sixty - two patients ( age 64.86  8.39 years , range 4179 ; 38 women and 24 men ) were included in this study .
the patients were scheduled for phacoemulsification and iol implantation from may 1 , 2012 , to december 31 , 2012 , in tianjin eye hospital .
all the surgeries were performed by the same doctor ( ya - wen guo ) .
phacoemulsification with a 3.2  mm clear corneal incision in the hydrophobic acrylic and hydrophilic acrylic group and a 5.5  mm sclera tunnel incision in the pmma group were followed by iol implantation in the capsular bag .
a hydrophobic acrylic spherical iol ( ar40e , amo , usa ) was implanted in the hydrophobic acrylic iol group . a hydrophilic acrylic spherical iol ( hq201hep , hexavision , france )
a pmma spherical iol ( pc156c55 , henan universe iol r&m co. , china ) was implanted in the pmma group .
the diameters of pupil were measured with wave - front analyzer kr-1w in dark room ( topcon , tokyo medical system inc . , japan ) with natural pupil and dilated pupil .
the retinal straylight was measured with c - quant straylight meter ( oculus optikgerte , gmbh , wetzlar , germany ) .
it is more suitable for clinical examination than the instrument which works with direct compensation method .
the center of the test field is divided in half . when the compensation light is presented to one - half
the center is a ring - shaped flickering light source , which serves as the straylight source .
when the subject is tested , one - half of the center has counter - phase flickering added , the other has not .
the straylight meter will change the luminance of the stimulus and counter - phase modulating light automatically until the two halves are balanced . according to the subjects ' responses
all the subjects were examined with natural and dilated pupils one week and one month after surgery .
only when the estimated standard deviation ( esd ) was lower than 0.08 and the quality factor ( q ) was higher than 1.00 , the measurement was accepted .
the straylight data were presented as the mean  sd . the straylight values of three groups were compared with one - way analysis of variance ( anova ) .
the lsd ( least significance difference ) was used to identify effects among the iol types . in each pseudophakic group a paired t - test was used to compare the straylight values before and after pupil dilation .
comparison of the straylight one week and one month after surgery was performed with paired t - test .
all pupils involved in this study were round with no iris trauma and showed good responsiveness to light after surgery .
the mean ages of the hydrophobic acrylic , hydrophilic acrylic , and pmma iol groups were 67.17  6.82 , 62.82  9.50 , and 64.92  8.16 .
there were no significant differences between the three groups ( p > 0.05 ) . 

table 1 shows the characteristics of the rigid pmma , hydrophilic acrylic , and hydrophobic acrylic iols evaluated . 

table 2 shows the mean diameter of pupil one week after surgery and one month after cataract surgery .
there were no statistically significant differences among groups 1 week after surgery and 1 month after surgery ( p > 0.05 ) . 

the hydrophilic acrylic iol showed a significantly lower straylight value than the hydrophobic iol with dilated pupil one week after surgery ( p = 0.002 ) .
there was not a significant difference between hydrophilic acrylic and pmma iol group ( p > 0.05 ) .
but the straylight values of hydrophilic acrylic iol were the lowest of the three iol groups .
there was no significant difference in retinal straylight between one week and one month after surgery in each iol group with natural pupil ( p > 0.05 ) .
a similar result was found with dilated pupil ( p > 0.05 ) ( figure 1 ) .
no significant difference was found in retinal straylight between natural and dilated pupil in each iol group 1 week after surgery ( p > 0.05 ) .
a similar result was found a month after surgery ( p > 0.05 ) ( figure 2 ) .
patient complaints regarding dysphotopsia and glare after iol implantations have recently gained a great deal of attention .
only the hydrophilic acrylic iols showed a significantly lower straylight value than the hydrophobic acrylic iols in dilated pupils .
no significant difference was found in straylight between the other groups . with or without dilated pupil , the straylight value of the hydrophilic acrylic iol was the lowest among the three iol materials . with natural pupil ,
the square edge of iols can cause clinically significant glare and halo [ 13 , 14 ] .
the edge of the iol may have been exposed when the pupil was dilated , thereby increasing light scatter .
accordingly , hydrophobic iols induced more scattering . did the hydrophobic acrylic material induce more straylight ?
the difference in the optic diameter between the pmma iol and the other two iols should theoretically change the straylight value with dilated pupils . more study is recommended .
montenegro et al .   also found that postoperative straylight in the hydrophilic acrylic group was lower than that of the hydrophobic acrylic group .
he supposed that the glistenings around the hydrophobic acrylic iol can explain the reason for the higher amount of straylight induced by the hydrophobic acrylic iols . when iols are implanted into the eyes , some fluid - filled microvacuoles form in the hydrophobic iol optics , which are called glistenings .
the glistenings were observed from as early as one week after surgery until after several months [ 16 , 17 ] .
the high incidence of glistenings was associated with hydrophobic acrylic iols , with an incidence of 55% at one year after the hydrophobic acrylic iol implantation .
a japanese study showed that internal light scattering caused by the glistenings within the optic of the acrysof iols increased over time up to three years after surgery .
the high incidence of glistenings may be the reason for the higher straylight values in the hydrophobic acrylic iol group . in the present study
, we found that the straylight values at one week and one month after hydrophilic acrylic iol surgery were both lower than those of the hydrophobic acrylic iols .
in addition , we did not find any apparent glistening in the hydrophobic acrylic iol using a slit lamp . in the present study
, we did not find an increase in straylight values with increasing pupil size at one week and one month after surgery .
franssen 's study showed that there was no significant difference in straylight between pupils with diameters of 2.0  mm and 7.0  mm of healthy phakic eyes .
cervio et al . also found that straylight values were not associated with the pupil size of the subject .
reported that straylight increased with increasing pupil size in pseudophakic eyes at one year after surgery .
straylight values were significantly higher in dilated than those in natural pupils , which was contradictory to our study . in van gaalen 's study ,
the presence of the anterior capsule rim in the pupillary area , not the pupil size , was considered as the main reason for the increase in straylight .
van gaalen measured straylight using natural pupils and dilated pupils at one year after surgery . although the eyes that had posterior capsular opacification ( pco ) within the 3.0  mm diameter central zone of the posterior capsule were excluded , the migration of residual lens epithelial cells may have resulted in the opacification of the peripheral anterior and posterior capsules .
, we did not find pco in any of the patients during the brief follow - up period .
the follow - up period of one month is not enough to elicit changes of light scatter related to anterior capsule opacification .
they thought corneal edema could increase straylight values . in the present study , we did not find any marked cornea edema in all the subjects using slit lamp . but corneal thickness was not measured .
no significant differences were found in straylight values in natural pupils at one week and one month after surgery ; similar results were obtained in dilated pupils .
van der meulen et al . found no significant differences in straylight values between the patients examined within 30 days after surgery and those examined after 30 days or longer postoperatively .
study and van der meulen 's study all subjects were measured 7 and 30 days after surgery .
two parameters ( esd and q ) were used to determine the reliability of the measurement .
the measurement results are considered reliable when the esd is lower than 0.08 and the q is higher than 1 .
moreover , old age did not affect the measurement reliability of c - quant using the compensation comparison method .
 
 purpose . to investigate the intraocular straylight value after cataract surgery 
 . 
 methods . in this study , 
 76 eyes from 62 patients were subdivided into three groups . 
 a hydrophobic acrylic , a hydrophilic acrylic , and a pmma iol were respectively , implanted in 24 eyes , 28 eyes , and 24 eyes . 
 straylight was measured using c - quant at 1 week and 1 month postoperatively in natural and dilated pupils . 
 results . 
 the hydrophilic acrylic iols showed significantly lower straylight values than those of the hydrophobic acrylic iols in dilated pupils at 1 week and 1 month after surgery ( p < 0.05 ) . 
 however , the straylight values of the hydrophilic acrylic iols were the lowest among the three iol groups . no significant difference was observed in straylight between 1 week and 1 month postoperatively in each group with natural and dilated pupils ( p > 0.05 ) . 
 moreover , no significant difference was found in straylight between natural and dilated pupils in each group at 1 week and 1 month postoperatively ( p > 0.05 ) . conclusions . 
 although the hydrophobic acrylic iol induced more intraocular straylight , straylight differences among the 3 iols were minimal . 
 pupil size showed no effect on intraocular straylight ; the intraocular straylight was stable 1 week after surgery . 
 
1. Introduction
2. Materials and Methods
3. Results
4. Discussion