CORRESPONDENCE
1111
aberrations generated is small (small pupil); while for large pupils, the tolerance to decentration is larger, as indicated by equation 6. REFERENCES
Figure 2. The maximum decentration that an aspheric IOL could have while the RMS value of the coma generated by decentration is not above the RMS value of the corneal spherical aberration pretended to be corrected with the aspheric IOL. This approach assumes that the value of the spherical aberration introduced by the IOL compensates for the value from the cornea.
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi að2; 2Þ2 þ að3; 1Þ2 þ að2; 0Þ2 Z að4; 0Þ
ð4Þ
Using the equations 1 to 4, we can obtain Dy Z 0:145r
ð5Þ
From equation 5, we can calculate the maximum decentration for any given pupil radius, which will limit the benefit of the correction in terms of the RMS. If the generated defocus (equation 3) and astigmatism (equation 1) were corrected with a spectacle lens, the residual RMS after the correction will be created just by the coma (equation 2) and the resulting in the maximum displacement will be Dy Z 0:158r
ð6Þ
The calculations have been done for a vertical decentration; however, given the rotational symmetry of the spherical aberration, a similar result will be found for the decentration in any other direction. For a 5.0 mm pupil, equations 5 and 6 (equation 6 in Figure 2) gives a maximum displacement of 0.363 (Z 0.145 2.5) and 0.395 mm (Z 0.158 2.5), respectively, which is in good agreement with previously cited empirical results.1,4,5 Small differences can be the result of the fact that it is known that not all coefficients of the Zernike polynomial result in equivalent losses of visual quality.7 However, besides the explanation of the empirical results, equation 6 shows an interesting result: The decentration value only depends on pupil size, so it is independent of the value of the spherical aberration to be corrected. This is good news for surgeons because for small pupils, the decentration of an aspheric IOL will not be of great importance because the absolute value of the
1. Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby NES. A new intraocular lens design to reduce spherical aberration of pseudophakic eyes. J Refract Surg 2002; 18:683–691 2. Shentu X, Tang X, Yao K. Spherical aberration, visual performance and pseudoaccommodation of eyes implanted with different aspheric intraocular lens. Clin Exp Ophthalmol 2008; 36:620–624 pez-Gil N, Thibos L. Simulated effect of 3. Amigo A, Bonaque S, Lo corneal asphericity increase (Q-factor) as a refractive therapy for presbyopia. J Refract Surg 2012; 28:413–418 4. Altmann GE, Nichamin LD, Lane SS, Pepose JS. Optical performance of 3 intraocular lens designs in the presence of decentration. J Cataract Refract Surg 2005; 31:574–585 5. Wang L, Koch DD. Effect of decentration of wavefront-corrected intraocular lenses on the higher-order aberrations of the eye. Arch Ophthalmol 2005; 123:1226–1230. Available at: http://archopht.jamanetwork.com/data/Journals/OPHTH/9945/els50006.pdf. Accessed January 31, 2015 €m L, Unsbo P. Transformation of Zernike coefficients: 6. Lundstro scaled, translated, and rotated wavefronts with circular and elliptical pupils. J Opt Soc Am A Opt Image Sci Vis 2007; 24:569–577 7. Applegate RA, Sarver EJ, Khemsara V. Are all aberrations equal? J Refract Surg 2002; 18:S556–S562
Tale of a twist: Progressive postoperative intraocular lens tilt from a twisted haptic Kavitha Avadhani, MD, Anitha Shakunthala, MD, Sandeep Mark Thirumalai, MD, Gaurav Prakash, MD, FRCS Intraoperative problems with acrylic intraocular lens (IOL) insertion and/or their postoperative implications have rarely been reported. 1–3 Improper unfolding of a single-piece IOL (Acrysof, Alcon Laboratories, Inc.) caused by 1 of the haptics sticking to the optic is often known to occur.4 We report a case of a twisted leading haptic of a single-piece Acrysof IQ IOL causing progressive postoperative IOL tilt and subsequent lenticular astigmatism. CASE REPORT A 52-year-old diabetic man presented with posterior subcapsular cataract in both eyes. His corrected distance visual acuity was 20/120 and 20/80 in the right eye and left eye, respectively. The patient had “uneventful” clear corneal phacoemulsification with implantation of a single-piece hydrophobic acrylic intraocular lens (Acrysof IQ, SN60WF). Retrospectively, there had been slight decentration of the IOL at the end of the surgery that seemed to right itself when a dialer was used. On the first postoperative day,
J CATARACT REFRACT SURG - VOL 41, MAY 2015
1112
CORRESPONDENCE
Figure 1. A: Slitlamp photograph of the right eye on the first postoperative day showing a well-dilated pupil with an air bubble in the anterior chamber. The nasal edge of the optic of the IOL is just visible at the level of the capsulorhexis margin (yellow arrow). B: Slitlamp photograph of the right eye on the third postoperative day showing the optic edge in the pupillary plane (red arrow). C: Slitlamp photograph of the right eye on the third postoperative day after dilation with tropicamide 1.0% showing the tilted IOL and the twist at the superior optic–haptic junction (white arrow). D: Slitlamp photograph of the right eye in retroillumination mode after the untwisting procedure shows a dilated pupil with a wellcentered in-the-bag IOL (rim of the capsulorhexis is visible on the nasal side).
the uncorrected distance visual acuity (UDVA) was 20/200 in the right eye with astigmatism of 5.75 75. Slight IOL tilt was noted with the nasal edge of the optic, being visible at the level of the caspsulorhexis edge (Figure 1, A). There was an air bubble in the well-formed anterior chamber that prevented visualization of the upper haptic. There was no evidence of a posterior capsule defect or obvious fluid or ophthalmic viscosurgical device (OVD) in the bag; hence, a decision to observe was made. The patient returned for a review 1 day later. Ocular examination showed that the IOL optic was now at nearly 90 degrees to the capsule with the optic edge visible in the pupillary plane (Figure 1, B). A twist of the upper haptic (at the 1 o’clock position) was easily visible at the optic–haptic junction (Figure 1, C). This twist had caused the upper haptic to face downward instead of upward, as it should have. This twist had not been visible until then. The patient was taken to the operating room for IOL repositioning under aseptic conditions. Slight lifting and dialing of the IOL caused the twisted haptic to untwist and open into the right position. The IOL then comfortably slipped back into the bag
(Figure 1, D). The patient had a UDVA of 20/20 in the right eye the day after the untwisting procedure.
DISCUSSION To our knowledge, this is the first report of a haptic of a single-piece Acrysof IOL twisting during insertion. There are plenty of instances of improper unfolding of an IOL after insertion into the bag. Most of these are caused by inadequate OVD in the cartridge or rarely by the incorrect loading of the IOL.4 These occurrences are, however, instantly recognizable on the operating table because the IOL fails to unfold or sit properly in the bag even after apparent unfolding. In our case, the IOL unfolded with ease and even appeared to slip into position in the bag. This caused complete oversight of the twisting of the leading haptic. The memory of the haptic then caused it to untwist, albeit slowly. This
J CATARACT REFRACT SURG - VOL 41, MAY 2015
CORRESPONDENCE
untwisting process caused the slight IOL tilt and the significant astigmatism on the first postoperative day. The twist itself was not, however, visible at that time. A day later, this untwisting process had progressed enough to nudge the IOL out of the capsular bag, pushing the edge of the IOL into the pupillary plane. We believe that the twist may have occurred due to inadequate OVD in the cartridge while the IOL was being loaded. Postoperative astigmatism of this magnitude must set alarm bells ringing, and it may be prudent to look for a twist in the haptic in cases in which IOL tilting or unexplained postoperative astigmatism is observed.
1113
REFERENCES 1. Pfister DR. Stress fractures after folding an acrylic intraocular lens. Am J Ophthalmol 1996; 121:572–574 2. Balasubramanya R, Rani A, Dada T. Forceps-induced cracking of a single-piece acrylic foldable intraocular lens. Ophthalmic Surg Lasers Imaging 2003; 34:306–307 3. Shah U. Probable edge defect in Acrysof single-piece intraocular lens. Indian J Ophthalmol 2006; 54:277–278. Available at: http:// www.ijo.in/article.asp?issnZ0301-4738;yearZ2006;volumeZ54; issueZ4;spageZ277;epageZ278;aulastZShah. Accessed January 30, 2015 4. Van Vreeswijk H. Safe and easy way to release sticking haptic of a single-piece AcrySof intraocular lens. J Cataract Refract Surg 2008; 34:1611
J CATARACT REFRACT SURG - VOL 41, MAY 2015
1111
aberrations generated is small (small pupil); while for large pupils, the tolerance to decentration is larger, as indicated by equation 6. REFERENCES
Figure 2. The maximum decentration that an aspheric IOL could have while the RMS value of the coma generated by decentration is not above the RMS value of the corneal spherical aberration pretended to be corrected with the aspheric IOL. This approach assumes that the value of the spherical aberration introduced by the IOL compensates for the value from the cornea.
qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi að2; 2Þ2 þ að3; 1Þ2 þ að2; 0Þ2 Z að4; 0Þ
ð4Þ
Using the equations 1 to 4, we can obtain Dy Z 0:145r
ð5Þ
From equation 5, we can calculate the maximum decentration for any given pupil radius, which will limit the benefit of the correction in terms of the RMS. If the generated defocus (equation 3) and astigmatism (equation 1) were corrected with a spectacle lens, the residual RMS after the correction will be created just by the coma (equation 2) and the resulting in the maximum displacement will be Dy Z 0:158r
ð6Þ
The calculations have been done for a vertical decentration; however, given the rotational symmetry of the spherical aberration, a similar result will be found for the decentration in any other direction. For a 5.0 mm pupil, equations 5 and 6 (equation 6 in Figure 2) gives a maximum displacement of 0.363 (Z 0.145 2.5) and 0.395 mm (Z 0.158 2.5), respectively, which is in good agreement with previously cited empirical results.1,4,5 Small differences can be the result of the fact that it is known that not all coefficients of the Zernike polynomial result in equivalent losses of visual quality.7 However, besides the explanation of the empirical results, equation 6 shows an interesting result: The decentration value only depends on pupil size, so it is independent of the value of the spherical aberration to be corrected. This is good news for surgeons because for small pupils, the decentration of an aspheric IOL will not be of great importance because the absolute value of the
1. Holladay JT, Piers PA, Koranyi G, van der Mooren M, Norrby NES. A new intraocular lens design to reduce spherical aberration of pseudophakic eyes. J Refract Surg 2002; 18:683–691 2. Shentu X, Tang X, Yao K. Spherical aberration, visual performance and pseudoaccommodation of eyes implanted with different aspheric intraocular lens. Clin Exp Ophthalmol 2008; 36:620–624 pez-Gil N, Thibos L. Simulated effect of 3. Amigo A, Bonaque S, Lo corneal asphericity increase (Q-factor) as a refractive therapy for presbyopia. J Refract Surg 2012; 28:413–418 4. Altmann GE, Nichamin LD, Lane SS, Pepose JS. Optical performance of 3 intraocular lens designs in the presence of decentration. J Cataract Refract Surg 2005; 31:574–585 5. Wang L, Koch DD. Effect of decentration of wavefront-corrected intraocular lenses on the higher-order aberrations of the eye. Arch Ophthalmol 2005; 123:1226–1230. Available at: http://archopht.jamanetwork.com/data/Journals/OPHTH/9945/els50006.pdf. Accessed January 31, 2015 €m L, Unsbo P. Transformation of Zernike coefficients: 6. Lundstro scaled, translated, and rotated wavefronts with circular and elliptical pupils. J Opt Soc Am A Opt Image Sci Vis 2007; 24:569–577 7. Applegate RA, Sarver EJ, Khemsara V. Are all aberrations equal? J Refract Surg 2002; 18:S556–S562
Tale of a twist: Progressive postoperative intraocular lens tilt from a twisted haptic Kavitha Avadhani, MD, Anitha Shakunthala, MD, Sandeep Mark Thirumalai, MD, Gaurav Prakash, MD, FRCS Intraoperative problems with acrylic intraocular lens (IOL) insertion and/or their postoperative implications have rarely been reported. 1–3 Improper unfolding of a single-piece IOL (Acrysof, Alcon Laboratories, Inc.) caused by 1 of the haptics sticking to the optic is often known to occur.4 We report a case of a twisted leading haptic of a single-piece Acrysof IQ IOL causing progressive postoperative IOL tilt and subsequent lenticular astigmatism. CASE REPORT A 52-year-old diabetic man presented with posterior subcapsular cataract in both eyes. His corrected distance visual acuity was 20/120 and 20/80 in the right eye and left eye, respectively. The patient had “uneventful” clear corneal phacoemulsification with implantation of a single-piece hydrophobic acrylic intraocular lens (Acrysof IQ, SN60WF). Retrospectively, there had been slight decentration of the IOL at the end of the surgery that seemed to right itself when a dialer was used. On the first postoperative day,
J CATARACT REFRACT SURG - VOL 41, MAY 2015
1112
CORRESPONDENCE
Figure 1. A: Slitlamp photograph of the right eye on the first postoperative day showing a well-dilated pupil with an air bubble in the anterior chamber. The nasal edge of the optic of the IOL is just visible at the level of the capsulorhexis margin (yellow arrow). B: Slitlamp photograph of the right eye on the third postoperative day showing the optic edge in the pupillary plane (red arrow). C: Slitlamp photograph of the right eye on the third postoperative day after dilation with tropicamide 1.0% showing the tilted IOL and the twist at the superior optic–haptic junction (white arrow). D: Slitlamp photograph of the right eye in retroillumination mode after the untwisting procedure shows a dilated pupil with a wellcentered in-the-bag IOL (rim of the capsulorhexis is visible on the nasal side).
the uncorrected distance visual acuity (UDVA) was 20/200 in the right eye with astigmatism of 5.75 75. Slight IOL tilt was noted with the nasal edge of the optic, being visible at the level of the caspsulorhexis edge (Figure 1, A). There was an air bubble in the well-formed anterior chamber that prevented visualization of the upper haptic. There was no evidence of a posterior capsule defect or obvious fluid or ophthalmic viscosurgical device (OVD) in the bag; hence, a decision to observe was made. The patient returned for a review 1 day later. Ocular examination showed that the IOL optic was now at nearly 90 degrees to the capsule with the optic edge visible in the pupillary plane (Figure 1, B). A twist of the upper haptic (at the 1 o’clock position) was easily visible at the optic–haptic junction (Figure 1, C). This twist had caused the upper haptic to face downward instead of upward, as it should have. This twist had not been visible until then. The patient was taken to the operating room for IOL repositioning under aseptic conditions. Slight lifting and dialing of the IOL caused the twisted haptic to untwist and open into the right position. The IOL then comfortably slipped back into the bag
(Figure 1, D). The patient had a UDVA of 20/20 in the right eye the day after the untwisting procedure.
DISCUSSION To our knowledge, this is the first report of a haptic of a single-piece Acrysof IOL twisting during insertion. There are plenty of instances of improper unfolding of an IOL after insertion into the bag. Most of these are caused by inadequate OVD in the cartridge or rarely by the incorrect loading of the IOL.4 These occurrences are, however, instantly recognizable on the operating table because the IOL fails to unfold or sit properly in the bag even after apparent unfolding. In our case, the IOL unfolded with ease and even appeared to slip into position in the bag. This caused complete oversight of the twisting of the leading haptic. The memory of the haptic then caused it to untwist, albeit slowly. This
J CATARACT REFRACT SURG - VOL 41, MAY 2015
CORRESPONDENCE
untwisting process caused the slight IOL tilt and the significant astigmatism on the first postoperative day. The twist itself was not, however, visible at that time. A day later, this untwisting process had progressed enough to nudge the IOL out of the capsular bag, pushing the edge of the IOL into the pupillary plane. We believe that the twist may have occurred due to inadequate OVD in the cartridge while the IOL was being loaded. Postoperative astigmatism of this magnitude must set alarm bells ringing, and it may be prudent to look for a twist in the haptic in cases in which IOL tilting or unexplained postoperative astigmatism is observed.
1113
REFERENCES 1. Pfister DR. Stress fractures after folding an acrylic intraocular lens. Am J Ophthalmol 1996; 121:572–574 2. Balasubramanya R, Rani A, Dada T. Forceps-induced cracking of a single-piece acrylic foldable intraocular lens. Ophthalmic Surg Lasers Imaging 2003; 34:306–307 3. Shah U. Probable edge defect in Acrysof single-piece intraocular lens. Indian J Ophthalmol 2006; 54:277–278. Available at: http:// www.ijo.in/article.asp?issnZ0301-4738;yearZ2006;volumeZ54; issueZ4;spageZ277;epageZ278;aulastZShah. Accessed January 30, 2015 4. Van Vreeswijk H. Safe and easy way to release sticking haptic of a single-piece AcrySof intraocular lens. J Cataract Refract Surg 2008; 34:1611
J CATARACT REFRACT SURG - VOL 41, MAY 2015
