dislocation of an intraocular lens ( iol ) within the capsular bag is a rare , late complication of cataract surgery . probably reduce the frequency of in - the bag iol dislocation but fail to prevent this complication fully . frequency of in - the - bag iol dislocation increased with the development of cataract surgery technique . previously reported factors associated with ctr and iol dislocation are pseudoexfoliation , uveitis , previous vitreoretinal surgery , high myopia , and trauma . this factors are identical in secondary in - the bag lens dislocation , without ctr support . it is not known which patients with predisposing factors are likely to benefit from ctr insertion and which patients require alternative iol fixation . the ctr device was introduced by hara and yamada , in the early 1990s , to stretch the lens capsule and retain the circular contour of the capsular bag equator after cataract removal , to prevent intraocular lens decentration and dislocation . since then , various designs of ctrs have been in use . they are indicated in eyes with zonular weakness or dehiscence , including those with pseudoexfoliation syndrome , high myopia , mature cataract , and subluxated lenses , from marfan syndrome , ehlers - danlos syndrome , and other genetic diseases [ 7 , 8 ] . there are fewer higher - order aberrations in eyes with a multifocal iol and a ctr than in eyes with a multifocal iol only . management includes ctr removal , iol exchange , replacement with an anterior or a sutured posterior chamber iol , or suturing the iol through the bag to the iris or the sclera [ 11 , 12 ] . pseudoexfoliation syndrome has been the most frequently indicated factor in secondary in - the - bag iol dislocation . retrospective series of 86 patients revealed that neither lens material nor lens design appears to play a role . retrospective series available in the literature are very difficult to compare , as ctr insertion rates vary greatly between surgeons and depend on individual surgeon 's experience and approach to dislocated lens . it would be a great advantage to be able to select the patients with zonule insufficiency , who can be fixed with ctr , from those , who require alternative iol fixation . we performed an analysis of the eyes with secondary iol / ctr complex dislocation within 5 years from surgery . control group consisted of the eyes , where ctr was inserted and did not dislocate over the period of 5 years . operating notes of 15  835 intraocular surgeries performed between january 2010 and december 2014 at the department of ophthalmology of the medical university of lodz were reviewed . 19 eyes of 17 patients ' surgeries included ctr / iol complex removal or refixation , including removals associated and not associated with secondary lens implantation . 16 eyes of 15 patients ( 10 males and 5 female ) aged from 49 to 82 years ( mean 66.2  9.5 ) were analyzed . the time from primary cataract surgery was more than 5 years and one patient suffered blunt eye trauma , before ctr / iol complex dislocation was diagnosed . to select control group , we reviewed the notes of 10  789 cataract surgeries performed at the department of ophthalmology of the medical university of lodz between january 2007 and august 2010 . in 114 eyes of 106 patients , we identified 54 patients , remaining under the care of our out - patient department , who did not present with secondary iol dislocation , for 5 or more years . age and sex matched group of 26 eyes of 26 patients ( 17 male and 9 female ) aged from 56 to 85 ( mean 68.9  7.2 ) were randomly selected from 54 and analyzed as a control group . 16 eyes of 15 patients , who presented with secondary ctr / iol complex dislocation within 5 years from primary surgery , were analyzed in respect ofcause of crystalline lens dislocation;preoperative or intraoperative diagnosis of lens dislocation or zonule dehiscence;axial length and iol power;pre - op refractive status;coexistent pathology.exclusion criteria were ctr / iol dislocation more than 5 years from primary surgery and blunt eye trauma as a cause of ctr / iol complex dislocation . we did exclude patients in whom trauma was the reason of crystalline lens subluxation before primary cataract surgery . the data were analyzed by means of descriptive statistics , and fisher 's exact test and chi - squared test were used for significance . in all analyses , a statistically significant difference was assumed for p  0.05 . cause of crystalline lens dislocation ; preoperative or intraoperative diagnosis of lens dislocation or zonule dehiscence ; axial length and iol power ; pre - op refractive status ; coexistent pathology . axial lengths of the eyeball , refractive status , iol power , and timing of the diagnosis of zonule dehiscence and subluxation in analyzed groups are summarized in table 1 . in the group of patient with dislocation the axial length was 23.8  1.3 ( from 21 to 29 ) and in the group without dislocation 20.7  1.2 ( from 19 to 24 ) , p = 0.008 . preoperative diagnosis of zonule dehiscence was made in 13 patients with the dislocation group and in 7 patients without dislocation . axial length of the eyeball in those patients was 23.8  1.1 from 21 to 29 and 20.6  0.8 from 19 to 22 , respectively ( p = 0.007 ) . there were no statistically significant differences in any of the pathologies like clinically visible pseudoexfoliation , degenerative myopia , uveitis , glaucoma or ocular hypertension , and diabetes mellitus . statistically significant difference was detected in the presence of the blunt eye trauma as a cause of lens subluxation . there were no cases in the dislocation group and 7 ( 26.9% ) cases in the group without dislocation ( p = 0.04 ) . axial length of the eyeball was statistically significant higher in the group of patients with ctr / iol complex dislocation . two patients in this group had high degenerative myopia ( axial length 28.4  mm and 29.5  mm , resp . ) with myopic retinopathy . in both cases we performed second analysis of the group , having excluded this two cases of degenerative myopia and we repeated comparison with the control group . statistical significance remained in respect of axial length of the eyeball ( p = 0.009 ) , iol power ( p = 0.002 ) , refraction in spherical equivalent ( p = 0.001 ) , and preoperative diagnosis of zonule dehiscence ( p = 0.007 ) . there were no statistically significant differences in clinically visible pseudoexfoliation ( p = 0.9 ) . our retrospective analysis indicates that higher axial length of the eyeball and associated myopia and low iol power may be a strong predisposing factor to secondary dislocation of ctr / iol complex . we propose the hypothesis that longer axial length of the eyeball makes dislocation of the ctr / iol complex more likely especially the presence of pseudoexfoliation and other previously identified factors like uveitis , glaucoma , and vitreo - retinal surgery . it is likely that what makes difference is the diameter of the ctr / iol complex in relation to the diameter of the eyeball at the level of the ciliary processes . in cases where the diameter of the capsular bag stretched by the ring is significantly smaller than diameter of the eyeball at the level of ciliary body , where the ctr / iol complex is fixated , ctr fails to release the tension of the ciliary processes adequately and does not prevent further degeneration of the ciliary processes and makes dislocation more likely . there were no significant differences in the rate of pseudoexfoliation between the groups of patients with and without dislocation in our study . pseudoexfoliation is most frequent factor responsible for zonule weaknesses [ 14 , 15 ] , but our findings help to understand why some patients with lens subluxation secondary to pseudoexfoliation remain stable with ctr and some patients suffer from secondary dislocation of the ctr / iol complex . it appears likely that axial length of the eyeball is one of the factors contributing . we decided to analyze the patients who presented with dislocation within 5 years from primary surgery . this decision was based on the assumption that early secondary dislocation is the one that surgeon would most like to prevent , and these patients would be the ones more likely to reveal predisposing features . also the 5-year period from primary surgery to dislocation was based on the practicability of obtaining the control group . composing a control group was a big challenge in this analysis , as it was difficult to obtain the patients who were operated on more than 5 years and still under the care of our department , to ascertain that no dislocation was present . in our series none of the patients with ctr / iol complex dislocation had blunt eye trauma as a reason for crystalline lens subluxation . traumatic crystalline lens subluxations are due to mechanical rupture of the zonule in a specific area only and are not the reason for progressive zonule degeneration . mutations in human fibrillin-1 and fibrillin-2 , which are major constituents of tissue microfibrils , can affect multiple ocular components , including the ciliary zonule , lens , drainage apparatus , cornea , and retina . in ectopia lentis observed in marfan 's syndrome , the fibers of the ciliary zonule appeared stretched or ruptured , consistent with a pathogenesis of haploinsufficiency , but in weill - marchesani syndrome , the problem appears to be aberrant formation of the zonule and the lens [ 18 , 19 ] . therefore , insights on the composition and formation of the zonule are especially valuable in the context of microfibril disorders . fbn1 , fbn2 , and fbn3 can form homo- or heterotypic microfibrils [ 20 , 21 ] . the anatomy of the zonular apparatus and its structural arrangement have been described previously using ultrasound biomicroscopy [ 22 , 23 ] and scanning electron microscopy . the anterior zonule has a greater effect on the anterior lens surface , and the posterior zonule has a greater effect on the posterior lens surface . this may be due to the thickness difference between the anterior and posterior capsule   and , potentially , the role of the hyaloid membrane and its connections with the posterior zonule , which could act together to augment the effect of posterior zonular tension . this may be another factor influencing the way ctr stretches the capsular bag following crystalline lens removal . in myopia , the mechanism for lens subluxation may be different than in pseudoexfoliation [ 4 , 27 ] . lens subluxation may be the result of progressive overstretching of the processes , and progressive elongation of the fibers , rather than degeneration and weakening without elongation which is more likely in pseudoexfoliation . elongation of zonular processes may result from the disproportion between the crystalline lens size and the size of the eyeball . following phacoemulsification , and ctr insertion , the capsule becomes more flat , and its diameter becomes larger than before surgery . in myopic eye it was not possible to obtain data on the stage of crystalline lens subluxation preoperatively and intraoperatively . it appears likely that the more the degrees of subluxation , the more the chance of ctr failure to secure it . also the degree of zonule degeneration from pseudoexfoliation is not measurable at present and it is not possible to assess it unless subluxation is already present . ctrs were inserted by different surgeons , and there may be in - between surgeon variation in the approach to the subluxated crystalline lens , but this inconsistency may only have a minimal impact on the conclusions . axial length of the eyeball , myopia , and low iol power appear to play a role in secondary ctr / iol complex dislocation within 5 years from primary cataract surgery . patients with cataracts or lens subluxation as the result of blunt eye trauma appear likely to remain stable with ctr . preoperative diagnosis of lens subluxation increases the chances of secondary iol / ctr complex dislocation .
purpose . to analyze the patients with secondary dislocation of ctr and iol within 5 years from cataract surgery , to determine predisposing factors 
 . methods . 16 eyes of 15 patients 
 aged 66.2  6.7 ( from 49 to 82 ) with ctr / iol complex dislocation within 5 years from cataract surgery were compared with 26 patients aged 67.1  7.2 ( from 53 to 85 ) , implanted with ctr during cataract surgery to manage zonule dehiscence and did not dislocate for at least 5 years , in respect of cause , axial length and iol power , refraction , coexistent pathology , and trauma . 
 results . 
 axial length of the eyeball was 23.8  1.3 ( from 21 to 29 ) in the group of patients with ctr / iol dislocation and 20.7  1.2 ( from 19 to 24 ) in patients with no dislocation present ( p = 0.008 ) . 
 crystalline lens dislocation was diagnosed before surgery in 13 of 16 patients with ctr / iol complex dislocation as opposed to 7 of 26 eyes in the control group ( p = 0.01 ) . 
 pseudoexfoliation was present in 50% and 58% in both groups , respectively . 
 traumatic dislocation was present in 8 patients , none of them with ctr / iol dislocation ( p = 0.04 ) . 
 conclusion . 
 longer axial length may contribute to the failure of the ctr to prevent in - the - bag iol dislocation . 
 traumatic dislocation appears to be well fixed with the ctr .