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Modified insertion technique for the SI-18NB intraocular lens
Modified insertion technique for the SI -18NB intraocular lens James A. Davison, M.D.
AB TRA T The 14 mm pol propylen haptic tructur of th MO I-I B i extrem Iy oft for a~ mall inci ion in ertion. The material ha at nd nc to 10 e it memory and xpe.-ience a perman nt alt r tion in hape if it i b nt too much durin implantation. n alt rnati ur ical techniqu that pare extreme haptic di tortion and impro e centration of th intra ular len opti i pre nted.
Key Word
intra ul ar 1 n , phac mul ifi ation, p I pr pIn , ilicon
Silicone intraocular lenses are available in a single plate design (Staar Medical) and in a 6 mm optic design with polypropylene (Prolene®) haptics (American Medical Optics model SI-I8NB). The overall length of the 6 mm optic lens is 14 mm. The AMO SI-I8NB is usually placed in the capsular bag through a 4 mm incision using a Fine or Faulkner forceps. It can be placed without tucking the haptics between the folded optic but this may be awkward and can result in inferior corneal touch. While tucking the haptics between the folded optic halves is usually acceptable, subtle but immediate and definite optic decentration sometimes occurs even though both haptics are symmetrically contained within the capsular bag after a perfect capsulorhexis. Optic decentration may be increased because of permanent haptic distortion created during routine intraocular lens (IOL) insertion. It is easily prevented by using a simple modification of the haptic tuck IOL insertion technique. MATERIALS AND METHODS In an informal analysis of my intraoperative and postoperative results with the AMO SI-I8NB, I Reprint requests to James A. Davison, M.D., 309 East Church Street, Marshalltown, Iowa 50158.
J CATARACT REFRACT
noticed that occasionally the optic decentered about 0.5 mm for no apparent reason. The decentration seemed to be haptic dependent and not bag dependent; i.e., it was always oriented toward one haptic regardless of IOL position within the capsular bag. Other surgeons using this IOL in substantial volume were not experiencing the problem, but in some of my cases the decentration was present at surgery and persisted postoperatively. A study of slow motion and single frame videotape and of serial 35 mm photographs helped identify the cause of the decentration and a surgical solution. RESULTS Photographic analysis revealed that optic decentration occurred for two reasons. First, there was tremendous acute angle distortion of the tucked proximal haptic near its insertion at the optic during the final stages of compression through the 4 mm wound. Second, because of this acute bending, the Prolene haptic had lost its memory and remained curled and functionally shortened even after its acute angle compression had been relaxed. Leading and trailing haptics are easily identified if the IOL is folded and inserted with the long portion of the haptics parallel to the blades of the folder. The IOL is rotated 90 degrees when the haptics are to be tucked in the folded optic during insertion, so the leading and trailing haptics are still identifiable. The trailing haptic presents no problem although it is swept back and there is some haptic distortion at the optic-haptic junction during insertion. However, the haptic end is free and no significant acute angle distortion occurs while the haptic is compressed as the optic body passes through the wound. The leading haptic has to be tucked and advanced into the anterior chamber early or it will catch on the wound and efficient, safe IOL insertion will be impossible. Usually the tip of the leading haptic is tucked between the folded halves of the optic (Figure 1). As the optic is advanced the wound compresses the haptic toward the optic and squeezes it so that its redundancy accumulates near the optic-haptic junction outside the anterior chamber (Figures 2 and 3). Eventually, the haptic is folded through an arc of approximately 110 degrees (125 degrees minus the original approximately 15 degrees of angle in the proximal modified J-loop haptic). At this point of maximum compression and maximum distortion, an acute 55 degree angle is formed in the almost straight portion of the proximal haptic (Figure 4). After the IOL has been placed within the capsular bag, the trailing haptic has a normal anatomic configuration (Figure 5). However, the leading hap-
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849
Fig. 1.
(Davison) The AMO SI-18NB silicone IOL is engaged by the Fine folder. The end of the leading haptic is tucked between the folded optic halves.
Fig. 4.
(Davison) Tremendous acute angle distortion is seen at the point of maximum accumulation of redundant haptic material outside the wound.
Fig. 2.
(Davison) The end of the trailing haptic is seen outside the anterior chamber as it is compressed against the optic sandwich. The proximal leading haptic angle has changed from its initial 15 degrees to more than 90 degrees.
Fig. 5.
(Davison) Normal trailing haptic architecture seen during direct inspection after capsular bag implantation.
Fig. 3.
(Davison) At the halfWay point of optic insertion through the wound. considerable acute angle distortion is seen in the leading haptic.
Fig. 6.
(Davison) Abnormal leading haptic architecture seen during direct inspection after capsular bag implantation. This residual distortion of the proximal haptic creates a functionally shorter leading haptic length.
850
J CATARACT REFRACT
SURG-VOL 17, NOVEMBER 1991
tic is substantially distorted and its functional length shortened by this persistent distortion (Figure 6). A 0.5 mm optic decentration results even though the IOL has been placed within the capsular bag (Figure 7). Asymmetric haptic distortion can be prevented by hooking the distal curled I-portion of the leading haptic over the folded optic edge before insertion (Figure 8). Proximal haptic compression and acute angle distortion do not occur because the distal haptic can be squeezed forward through the wound, actually ahead of the optic (just as the trailing haptic is squeezed behind), since the curved
Polypropylene haptics have the advantages of extreme flexibility and softness; loss of memory
Fig. 7.
(Davison) The IOL optic is decentered 0.5 mm toward the functionally shorter leading haptic. Note the perfectly centered 5.5 mm capsulorhexis and the posterior capsular striae from the haptic knees' relative two point capsular bag fixation.
Fig. 9.
(Davison) The IOL optic and leading haptic knee just before insertion through the wound.
Fig. 8.
(Davison) The leading haptic distal J-Ioop has been hooked over the leading optic edge. This results in minor distortion of the proximal haptic at the optichaptic junction which is identical to that of the trailing haptic in the same location.
Fig. 10.
(Davison) Symmetrical appearance of the trailing and leading haptics. Unencumbered by the optic sandwich the haptics are allowed to trail and lead passively. Proximal haptic distortion is symmetrical and insignificant.
J CATARACT REFRACT
I-portion is not trapped by the optic sandwich (Figures 9 and 10). The leading haptic passively unhooks from the optic edge and springs into the capsular bag as the optic is unfolded (Figure 11). Comparing the trailing and leading haptics shows that neither haptic is distorted (Figures 12 and 13). In this case, the optic is perfectly centered (Figure 14). DISCUSSION
SURG-VOL 17, NOVEMBER 1991
851
Fig. 11.
(Davison) The trailing haptic has been tucked under the left anterior capsular flap. The leading haptic is about to unhook itself from the optic rim and will spring into the capsular bag on the right.
Fig. 13.
(Davison) 'The leading haptic anatomy is normal.
Fig. 12.
(Davison) The trailing haptic anatomy is normal.
Fig. 14.
(Davison) The IOL optic is perfectly centered.
after extreme distortion is a disadvantage. This paper presents one example of possible surgical insertional variations that avoid extreme haptic distortion. A popular solution involves tucking the distal end of both haptics into the folded optic sandwich. This usually achieves a minimized but symmetrical haptic distortion and actually shortens the functional length of the IOL. Another surgical solution might be to tuck the length of the leading haptic (or both haptics) when near the optic-haptic junction so the tips and knees could enter the eye without haptic material accumulating outside the eye and distorting. Alternatively, or perhaps additionally, IOL design solutions might involve using haptic materials with 852
J CATARACT REFRACT
improved memory, haptics 12 mm long, and a broad C capsular bag fixation design rather than oversized two-point fixation as in the modified J-Ioop design. A 14 mm haptic structure must experience substantial distortion to reside within a 10.5 mm capsular bag. The push from this extra material results in haptic curling which may be symmetrical but which sometimes is not, leading to optic decentration. Asymmetric overcompression and distortion of Prolene haptics increases the chance of such optic eccentricity. Patients who have received silicone IOLs through 4.0 mm incisions have an extraordinary earlyenthusiasm for their postoperative results. Immediate perfect anatomic centration of the optic within the
SURG-VOL 17, NOVEMBER 1991
capsulorhexis should be sought at all times. Initial eccentric placement of an optic within a perfectly centered capsulorhexis may allow the relentless forces of capsular fibrosis and contracture to decenter the IOL optic even further by ham mocking and squeezing one edge. This rilaY cause later disappointment in some patients who were happy with their initial results. Since this report was submitted, AMO has introduced another silicone IOL, the SI -26NGB, with the same 6 mm optic as the SI -18NB and haptics made of Prolene but a new 13 mm diameter modified C haptic configuration. This design is more appropriate and advanced for capsular bag placement but since the distal J is not used in the new model, the insertion technique described in this paper cannot be applied. The principle of preventing acute angle distortion of Prolene haptic material is still valid and important to observe but a variation in insertion technique is required. As suggested in the preceding discussion, excel-
lent results with either IOL may be obtained by tucking the middle portion of the leading haptic into the middle of the optic sandwich. The distal end then protrudes in front of the folded optic as it is inserted through the wound. Insignificant distortion of the proximal haptic is seen but no acute angle distortion occurs anywhere along the haptic length. Special care must be taken when rotating the SI-26NGB in the eye in preparation for unfolding. The distal 1.5 mm haptic which initially projects toward the right will then point toward the cornea. It may in fact touch the cornea if not deliberately kept posterior or contained within the inferior capsular bag just prior to unfolding. The least traumatic insertion can be accomplished by releasing the sandwiched haptic about three fourths of the way through the final optic rotation just before the optic unfolds. This release allows the distal end of the leading haptic to spring against the posterior capsule in a natural position ready to sweep to the right when the optic unfolds.
J CATARACT REFRACT SURG-VOL 17, NOVEMBER 1991
853
AB TRA T The 14 mm pol propylen haptic tructur of th MO I-I B i extrem Iy oft for a~ mall inci ion in ertion. The material ha at nd nc to 10 e it memory and xpe.-ience a perman nt alt r tion in hape if it i b nt too much durin implantation. n alt rnati ur ical techniqu that pare extreme haptic di tortion and impro e centration of th intra ular len opti i pre nted.
Key Word
intra ul ar 1 n , phac mul ifi ation, p I pr pIn , ilicon
Silicone intraocular lenses are available in a single plate design (Staar Medical) and in a 6 mm optic design with polypropylene (Prolene®) haptics (American Medical Optics model SI-I8NB). The overall length of the 6 mm optic lens is 14 mm. The AMO SI-I8NB is usually placed in the capsular bag through a 4 mm incision using a Fine or Faulkner forceps. It can be placed without tucking the haptics between the folded optic but this may be awkward and can result in inferior corneal touch. While tucking the haptics between the folded optic halves is usually acceptable, subtle but immediate and definite optic decentration sometimes occurs even though both haptics are symmetrically contained within the capsular bag after a perfect capsulorhexis. Optic decentration may be increased because of permanent haptic distortion created during routine intraocular lens (IOL) insertion. It is easily prevented by using a simple modification of the haptic tuck IOL insertion technique. MATERIALS AND METHODS In an informal analysis of my intraoperative and postoperative results with the AMO SI-I8NB, I Reprint requests to James A. Davison, M.D., 309 East Church Street, Marshalltown, Iowa 50158.
J CATARACT REFRACT
noticed that occasionally the optic decentered about 0.5 mm for no apparent reason. The decentration seemed to be haptic dependent and not bag dependent; i.e., it was always oriented toward one haptic regardless of IOL position within the capsular bag. Other surgeons using this IOL in substantial volume were not experiencing the problem, but in some of my cases the decentration was present at surgery and persisted postoperatively. A study of slow motion and single frame videotape and of serial 35 mm photographs helped identify the cause of the decentration and a surgical solution. RESULTS Photographic analysis revealed that optic decentration occurred for two reasons. First, there was tremendous acute angle distortion of the tucked proximal haptic near its insertion at the optic during the final stages of compression through the 4 mm wound. Second, because of this acute bending, the Prolene haptic had lost its memory and remained curled and functionally shortened even after its acute angle compression had been relaxed. Leading and trailing haptics are easily identified if the IOL is folded and inserted with the long portion of the haptics parallel to the blades of the folder. The IOL is rotated 90 degrees when the haptics are to be tucked in the folded optic during insertion, so the leading and trailing haptics are still identifiable. The trailing haptic presents no problem although it is swept back and there is some haptic distortion at the optic-haptic junction during insertion. However, the haptic end is free and no significant acute angle distortion occurs while the haptic is compressed as the optic body passes through the wound. The leading haptic has to be tucked and advanced into the anterior chamber early or it will catch on the wound and efficient, safe IOL insertion will be impossible. Usually the tip of the leading haptic is tucked between the folded halves of the optic (Figure 1). As the optic is advanced the wound compresses the haptic toward the optic and squeezes it so that its redundancy accumulates near the optic-haptic junction outside the anterior chamber (Figures 2 and 3). Eventually, the haptic is folded through an arc of approximately 110 degrees (125 degrees minus the original approximately 15 degrees of angle in the proximal modified J-loop haptic). At this point of maximum compression and maximum distortion, an acute 55 degree angle is formed in the almost straight portion of the proximal haptic (Figure 4). After the IOL has been placed within the capsular bag, the trailing haptic has a normal anatomic configuration (Figure 5). However, the leading hap-
SURG-VOL 17, NOVEMBER 1991
849
Fig. 1.
(Davison) The AMO SI-18NB silicone IOL is engaged by the Fine folder. The end of the leading haptic is tucked between the folded optic halves.
Fig. 4.
(Davison) Tremendous acute angle distortion is seen at the point of maximum accumulation of redundant haptic material outside the wound.
Fig. 2.
(Davison) The end of the trailing haptic is seen outside the anterior chamber as it is compressed against the optic sandwich. The proximal leading haptic angle has changed from its initial 15 degrees to more than 90 degrees.
Fig. 5.
(Davison) Normal trailing haptic architecture seen during direct inspection after capsular bag implantation.
Fig. 3.
(Davison) At the halfWay point of optic insertion through the wound. considerable acute angle distortion is seen in the leading haptic.
Fig. 6.
(Davison) Abnormal leading haptic architecture seen during direct inspection after capsular bag implantation. This residual distortion of the proximal haptic creates a functionally shorter leading haptic length.
850
J CATARACT REFRACT
SURG-VOL 17, NOVEMBER 1991
tic is substantially distorted and its functional length shortened by this persistent distortion (Figure 6). A 0.5 mm optic decentration results even though the IOL has been placed within the capsular bag (Figure 7). Asymmetric haptic distortion can be prevented by hooking the distal curled I-portion of the leading haptic over the folded optic edge before insertion (Figure 8). Proximal haptic compression and acute angle distortion do not occur because the distal haptic can be squeezed forward through the wound, actually ahead of the optic (just as the trailing haptic is squeezed behind), since the curved
Polypropylene haptics have the advantages of extreme flexibility and softness; loss of memory
Fig. 7.
(Davison) The IOL optic is decentered 0.5 mm toward the functionally shorter leading haptic. Note the perfectly centered 5.5 mm capsulorhexis and the posterior capsular striae from the haptic knees' relative two point capsular bag fixation.
Fig. 9.
(Davison) The IOL optic and leading haptic knee just before insertion through the wound.
Fig. 8.
(Davison) The leading haptic distal J-Ioop has been hooked over the leading optic edge. This results in minor distortion of the proximal haptic at the optichaptic junction which is identical to that of the trailing haptic in the same location.
Fig. 10.
(Davison) Symmetrical appearance of the trailing and leading haptics. Unencumbered by the optic sandwich the haptics are allowed to trail and lead passively. Proximal haptic distortion is symmetrical and insignificant.
J CATARACT REFRACT
I-portion is not trapped by the optic sandwich (Figures 9 and 10). The leading haptic passively unhooks from the optic edge and springs into the capsular bag as the optic is unfolded (Figure 11). Comparing the trailing and leading haptics shows that neither haptic is distorted (Figures 12 and 13). In this case, the optic is perfectly centered (Figure 14). DISCUSSION
SURG-VOL 17, NOVEMBER 1991
851
Fig. 11.
(Davison) The trailing haptic has been tucked under the left anterior capsular flap. The leading haptic is about to unhook itself from the optic rim and will spring into the capsular bag on the right.
Fig. 13.
(Davison) 'The leading haptic anatomy is normal.
Fig. 12.
(Davison) The trailing haptic anatomy is normal.
Fig. 14.
(Davison) The IOL optic is perfectly centered.
after extreme distortion is a disadvantage. This paper presents one example of possible surgical insertional variations that avoid extreme haptic distortion. A popular solution involves tucking the distal end of both haptics into the folded optic sandwich. This usually achieves a minimized but symmetrical haptic distortion and actually shortens the functional length of the IOL. Another surgical solution might be to tuck the length of the leading haptic (or both haptics) when near the optic-haptic junction so the tips and knees could enter the eye without haptic material accumulating outside the eye and distorting. Alternatively, or perhaps additionally, IOL design solutions might involve using haptic materials with 852
J CATARACT REFRACT
improved memory, haptics 12 mm long, and a broad C capsular bag fixation design rather than oversized two-point fixation as in the modified J-Ioop design. A 14 mm haptic structure must experience substantial distortion to reside within a 10.5 mm capsular bag. The push from this extra material results in haptic curling which may be symmetrical but which sometimes is not, leading to optic decentration. Asymmetric overcompression and distortion of Prolene haptics increases the chance of such optic eccentricity. Patients who have received silicone IOLs through 4.0 mm incisions have an extraordinary earlyenthusiasm for their postoperative results. Immediate perfect anatomic centration of the optic within the
SURG-VOL 17, NOVEMBER 1991
capsulorhexis should be sought at all times. Initial eccentric placement of an optic within a perfectly centered capsulorhexis may allow the relentless forces of capsular fibrosis and contracture to decenter the IOL optic even further by ham mocking and squeezing one edge. This rilaY cause later disappointment in some patients who were happy with their initial results. Since this report was submitted, AMO has introduced another silicone IOL, the SI -26NGB, with the same 6 mm optic as the SI -18NB and haptics made of Prolene but a new 13 mm diameter modified C haptic configuration. This design is more appropriate and advanced for capsular bag placement but since the distal J is not used in the new model, the insertion technique described in this paper cannot be applied. The principle of preventing acute angle distortion of Prolene haptic material is still valid and important to observe but a variation in insertion technique is required. As suggested in the preceding discussion, excel-
lent results with either IOL may be obtained by tucking the middle portion of the leading haptic into the middle of the optic sandwich. The distal end then protrudes in front of the folded optic as it is inserted through the wound. Insignificant distortion of the proximal haptic is seen but no acute angle distortion occurs anywhere along the haptic length. Special care must be taken when rotating the SI-26NGB in the eye in preparation for unfolding. The distal 1.5 mm haptic which initially projects toward the right will then point toward the cornea. It may in fact touch the cornea if not deliberately kept posterior or contained within the inferior capsular bag just prior to unfolding. The least traumatic insertion can be accomplished by releasing the sandwiched haptic about three fourths of the way through the final optic rotation just before the optic unfolds. This release allows the distal end of the leading haptic to spring against the posterior capsule in a natural position ready to sweep to the right when the optic unfolds.
J CATARACT REFRACT SURG-VOL 17, NOVEMBER 1991
853