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Reply: Scleral fixation
LETTERS
Table 1. Table 2 from the original article showing the Tomey incorrectly programmed Hoffer Q formula, yielding a mean prediction error greater than 11.0 D, with an error range of 17.6 D.
Table 2. Difference between predicted and actual postoperative refractions. Formula
Mean G SD (D)
Range (D)
SRK II SRK/T Holladay 1 Hoffer Q
C11.94 G 7.07 C4.40 G 4.34 C2.74 G 4.47 D11.44 G 7.49
C4.22 to C21.60 C0.40 to C11.17 0.56 to C10.20 D4.08 to D21.70
Table 2. Table 2 from the erratum showing the Tomey correctly programmed Hoffer Q formula, yielding the lowest mean prediction error of 2.80 D, with an error range of 9.0 D.
Table 2. Difference between predicted and actual postoperative refractions. Formula
Mean G SD (D)
Range (D)
SRK II SRK/T Holladay Hoffer Q
C11.94 G 7.07 C4.40 G 4.34 C3.03 G 4.23 D2.80 G 1.83
C4.22 to C21.60 C0.40 to C11.17 0.56 to C10.20 L4.02 to D5.00
is used to separate the 3 zeroes from the numeral before them; in Europe, a period is used. In America, a ‘‘million dollars and 56 cents’’ is written ‘‘$1,000,000.56’’; in Europe, it is written ‘‘$1.000.000,56.’’ Thus, Zuberbuhler and Morrell may have thought that ‘‘1,000’’ was really 1.000 or the number one. Most have learned this difference. Perhaps using ‘‘1000’’ in the formula publication would have been preferable. I thank Zuberbuhler and Morrell for pointing out the value of the Hoffer Q formula over the past 13 years and the problems inherent in individuals programming this formula based on the publications without checking it with the author. I apologize for any confusion this has caused.dKenneth J. Hoffer, MD REFERENCES 1. Erratum. J Cataract Refract Surg 1994; 20:677 2. Oshika T, Imamura A, Amano S, et al. Piggyback foldable intraocular lens implantation in patients with microphthalmos. J Cataract Refract Surg 2001; 27:841–844 3. Erratum. J Cataract Refract Surg 2001; 27:1536
Scleral fixation I congratulate Hoffmann et al.1 for their article about scleral fixation via suture retrieval through a scleral tunnel. The use of irisclaw intraocular lenses (IOLs) is a safe method in many cases, such as those mentioned by the authors. However, scleral suturing is done in cases in which the patient has iris problems, such as a scleral ring, or when the IOL requires suturing. In the article by Hoffman et al., this technique is used to prevent the suture ends from protruding from the conjunctiva by keeping them in
the scleral tunnel. After looking at other reports on this topic, I would like to make the following points. 1. This method is similar to the scleral flap method in that both use lamellary scleral dissection. It is a modification of the flap created. Especially in eyes in which intraocular pressure is low, preperations of these tunnels could be problematic. 2. The need to prepare 2 tunnels is more time consuming. 3. Each of the prepared tunnel’s upper lips is pierced at 2 points. The edges of the knot formed below could be directed upward and protrude from the pierced points. 4. When the knot is being prepared, especially if the tunnel is long, it could be difficult to form a tight knot on the sclera. In this case, the IOL will not be tightly attached to the sclera. 5. As mentioned by Hoffman et al., based on the type of large corneal incision, suturing of the incision could be joined to the scleral suture knot tunnels. Not only would the incision not be closed properly, but contact between the IOL and sclera would be weakened. 6. In my article on scleral fixation,2 the suture end with the knot is buried in the sclera. The edges will not cause problems because the knot and suture edge lie horizontally in the sclera. By covering the knot with a patch graft, flap or rotation is not needed. Additionally, the technique is quite easy; after it has been learned, it can be performed quickly. The method has been used succesfully in adults and infants. MEHMET BAYKARA, MD Bursa, Turkey REFERENCES 1. Hoffman RS, Fine IH, Packer M, Rozenberg I. Scleral fixation uisng suture retrieval thorugh a scleral tunnel. J Cataract Refract Surg 2006; 32: 1259–1263 2. Baykara M. Suture burial technique in scleral fixation. J Cataract Refract Surg 2004; 30:957–959
Reply: Our approach to scleral fixation does represent a modification of the traditional triangular flap technique, but we believe it offers several advantages not inherent in the traditional approach. The tunnel provides a larger surface area, which facilitates suture passage for an ab interno or ab externo approach. It appears to be easier to dissect than a triangular flap and requires no sutures for closure. Although the construction of 2 tunnels is more time consuming than a procedure in which the suture knot is buried through rotation of a full-thickness scleral pass, it is no less efficient than the dissection of 2 triangular flaps. We currently prefer not to rotate knots because of the possibility of suture breakage. In addition, the larger 9-0 and 8-0 recommendations for suture gauges may further impede knot rotation secondary to the larger knot size. The technique does require 2 suture passes that are initially placed through the full thickness of the dissected sclera, including the roof. These punctures appear to heal, as would be the case with any suture pass through scleral tissue, and the knot has not eroded or poked through these perforations since it appears to lie midway between the perforations under nonperforated sclera. Tying the sutures allows the knot to slide under the
J CATARACT REFRACT SURG - VOL 33, JANUARY 2007
3
LETTERS
protection of the roof, and achieving adequate tension has not been an issue. We do recommend not tightening the sutures excessively and perhaps leaving some laxity to avoid cheese-wiring through the scleral bed. In our article, we presented one procedure only (scleral fixation of a large aniridia IOL); however, the tunnel technique can be used for any small-incision IOL or for a procedure that does not require incisions such as fixation of a dislocated IOL or repair of an iridodialysis. The large, temporal clear corneal incision used for the aniridia IOL is not connected with the scleral tunnel. Suture closure of the clear corneal incision incorporates relatively superficial suture passes compared with the depth of the sclerally fixated 9-0 polypropylene (Prolene) sutures. In addition, the scleral sutures are 1.0 mm posterior to the surgical limbus and thus an adequate distance from the clear corneal sutures. Compromise of the sutures, IOL, or tunnel has not been a problem, especially since the tunnel does not enter the anterior chamber. In eyes that are hypotonus and have large incisions or, for that matter, any incision, we recommend placing an anterior chamber (AC) maintainer or pars plana infusion port to avoid complications such as choroidal effusions or hemorrhages. The drawings in our article did not show the AC maintainer to simplify the image; however, it was mentioned in the technique description. The use of a scleral tunnel for scleral fixation is one more technique for surgeons to consider. As with many of our surgical techniques, we believe it represents a small incremental improvement of previous methods and we encourage surgeons to try it. In an upcoming issue, we will describe a further variation of this technique that eliminates the need for conjunctival dissection. We thank Baykara for taking the time to comment on our paper and we appreciate his contribution to this discipline within ophthalmology.dRichard S. Hoffman, MD, I. Howard Fine, MD, Mark Packer, MD, Israel Rozenberg, MD
Functions of the capsular tension ring I would like to make 2 comments about the recent capsular tension ring (CTR) article by Boomer and Jackson.1 1. Can implanting a CTR affect the intraocular (IOL) power formula? In the article, Boomer and Jackson state that the ‘‘CTR sat between the IOL haptics and ciliary body, which raised the question of whether a CTR modifies the effective lens position (ELP) and, ultimately, the accuracy of IOL calculations and refractive outcome.’’ To investigate this issue, Boomer and Jackson conducted the study. A previous study using the Miyake technique2 showed a CTR sitting in the capsular bag after cataract removal. The CTR did not strengthen the capsular bag or alter its anatomical position. When an IOL was placed in the bag, the CTR did not change the IOL’s position. However, if the CTR was larger than the capsular bag, the 2 ends of the CTR overlapped in the bag. If the CTR was smaller than the capsular bag, the CTR did not provide enough tension around the equator of the capsular bag and left a large opening between the 2 ends of the CTR, providing a potential opportunity for lens epithelial cells to migrate to the posterior capsule and eventually contribute to PCO. Based on these findings, a CTR is unlikely to affect the IOL power formula because the position of the IOL in the capsular bag is not affected by a CTR. The study by Boomer and Jackson provides scientific and clinical data to support the earlier study.
4
2. How does a CTR improve refractive outcome? In the article, Boomer and Jackson state ‘‘[t]he CTR subset analysis demonstrated a trend toward more accurate outcomes when using Holladay 2 formula but not SRK/T when compared with contralateral eyes without a CTR. Both formulas showed lower variances in the CTR eyes.’’ Therefore, the authors conclude the CTR not only assisted surgeons in surgery but also improved refractive outcomes and patient satisfaction. Previous studies2–5 suggest the CTR has 2 basic functions: facilitating phacoemulsification during surgery and maintaining IOL centration after surgery in eyes with zonular dehiscence. An in vitro study2 demonstrates that IOL decentration can be avoided when a CTR in implanted in a capsular bag with broken zonules. This finding is supported by clinical studies.3–5 If visual and refractive outcomes are better in eyes with a CTR than in those without a CTR, the CTR should be credited because it prevented IOL tilt and decentration in the eyes with zonular dehiscence after cataract surgery. The CTR is not a refractive device, but implanting a CTR may achieve good visual and refractive outcomes after cataract surgery in eyes with zonular dehiscence. In Boomer and Jackson’s article, the refractive prediction error was used to compare refractive outcomes between eyes with a CTR and those without a CTR. Several factors such as IOL decentration, the time of the postoperative refraction, and the astigmatism-reduction procedure during cataract surgery may have affected the measurement. These factors are critical and must be controlled to achieve accurate measurements. In summary, a CTR can facilitate phacoemulsification during surgery and maintain IOL centration after surgery in eyes with zonular dehiscence. Good visual and refractive outcomes following CTR implantation in these eyes are likely due to IOL centration. RAN SUN, MD Rochester, New York REFERENCES 1. Boomer JA, Jackson DW. Effect of the Morcher capsular tension ring on refractive outcome. J Cataract Refract Surg 2006; 32:1180–1183 2. Sun R, Gimbel HV. In vitro evaluation of the efficacy of the capsular tension ring for managing zonular dialysis in cataract surgery. Ophthalmic Surg 1998; 29:502–505 3. Hara T, Hara T, Yamada Y. ‘‘Equator ring’’ for maintenance of the completely circular contour of the capsular bag equator after cataract removal. Ophthalmic Surg 1991; 22:358–359 4. Cionni RJ, Osher RH. Endocapsular ring approach to the subluxed cataractous lens. J Cataract Refract Surg 1995; 2:245–249 5. Gimbel HV, Sun R, Heston JP. Management of zonular dialysis in phacoemulsification and IOL implantation using the capsular tension ring. Ophthalmic Surg Lasers 1997; 28:273–281
Modified technique for management of LIDRS We were very interested in the series of articles describing various maneuvers to relieve the reverse pupil block in the lens–iris diaphragm retropulsion syndrome (LIDRS).1–3 To relieve LIDRS, it is necessary to separate the posterior surface of the iris from the anterior surface of the anterior capsule. Previous reports describe maneuvers that lift the iris using the tip of the phaco or
J CATARACT REFRACT SURG - VOL 33, JANUARY 2007
Table 1. Table 2 from the original article showing the Tomey incorrectly programmed Hoffer Q formula, yielding a mean prediction error greater than 11.0 D, with an error range of 17.6 D.
Table 2. Difference between predicted and actual postoperative refractions. Formula
Mean G SD (D)
Range (D)
SRK II SRK/T Holladay 1 Hoffer Q
C11.94 G 7.07 C4.40 G 4.34 C2.74 G 4.47 D11.44 G 7.49
C4.22 to C21.60 C0.40 to C11.17 0.56 to C10.20 D4.08 to D21.70
Table 2. Table 2 from the erratum showing the Tomey correctly programmed Hoffer Q formula, yielding the lowest mean prediction error of 2.80 D, with an error range of 9.0 D.
Table 2. Difference between predicted and actual postoperative refractions. Formula
Mean G SD (D)
Range (D)
SRK II SRK/T Holladay Hoffer Q
C11.94 G 7.07 C4.40 G 4.34 C3.03 G 4.23 D2.80 G 1.83
C4.22 to C21.60 C0.40 to C11.17 0.56 to C10.20 L4.02 to D5.00
is used to separate the 3 zeroes from the numeral before them; in Europe, a period is used. In America, a ‘‘million dollars and 56 cents’’ is written ‘‘$1,000,000.56’’; in Europe, it is written ‘‘$1.000.000,56.’’ Thus, Zuberbuhler and Morrell may have thought that ‘‘1,000’’ was really 1.000 or the number one. Most have learned this difference. Perhaps using ‘‘1000’’ in the formula publication would have been preferable. I thank Zuberbuhler and Morrell for pointing out the value of the Hoffer Q formula over the past 13 years and the problems inherent in individuals programming this formula based on the publications without checking it with the author. I apologize for any confusion this has caused.dKenneth J. Hoffer, MD REFERENCES 1. Erratum. J Cataract Refract Surg 1994; 20:677 2. Oshika T, Imamura A, Amano S, et al. Piggyback foldable intraocular lens implantation in patients with microphthalmos. J Cataract Refract Surg 2001; 27:841–844 3. Erratum. J Cataract Refract Surg 2001; 27:1536
Scleral fixation I congratulate Hoffmann et al.1 for their article about scleral fixation via suture retrieval through a scleral tunnel. The use of irisclaw intraocular lenses (IOLs) is a safe method in many cases, such as those mentioned by the authors. However, scleral suturing is done in cases in which the patient has iris problems, such as a scleral ring, or when the IOL requires suturing. In the article by Hoffman et al., this technique is used to prevent the suture ends from protruding from the conjunctiva by keeping them in
the scleral tunnel. After looking at other reports on this topic, I would like to make the following points. 1. This method is similar to the scleral flap method in that both use lamellary scleral dissection. It is a modification of the flap created. Especially in eyes in which intraocular pressure is low, preperations of these tunnels could be problematic. 2. The need to prepare 2 tunnels is more time consuming. 3. Each of the prepared tunnel’s upper lips is pierced at 2 points. The edges of the knot formed below could be directed upward and protrude from the pierced points. 4. When the knot is being prepared, especially if the tunnel is long, it could be difficult to form a tight knot on the sclera. In this case, the IOL will not be tightly attached to the sclera. 5. As mentioned by Hoffman et al., based on the type of large corneal incision, suturing of the incision could be joined to the scleral suture knot tunnels. Not only would the incision not be closed properly, but contact between the IOL and sclera would be weakened. 6. In my article on scleral fixation,2 the suture end with the knot is buried in the sclera. The edges will not cause problems because the knot and suture edge lie horizontally in the sclera. By covering the knot with a patch graft, flap or rotation is not needed. Additionally, the technique is quite easy; after it has been learned, it can be performed quickly. The method has been used succesfully in adults and infants. MEHMET BAYKARA, MD Bursa, Turkey REFERENCES 1. Hoffman RS, Fine IH, Packer M, Rozenberg I. Scleral fixation uisng suture retrieval thorugh a scleral tunnel. J Cataract Refract Surg 2006; 32: 1259–1263 2. Baykara M. Suture burial technique in scleral fixation. J Cataract Refract Surg 2004; 30:957–959
Reply: Our approach to scleral fixation does represent a modification of the traditional triangular flap technique, but we believe it offers several advantages not inherent in the traditional approach. The tunnel provides a larger surface area, which facilitates suture passage for an ab interno or ab externo approach. It appears to be easier to dissect than a triangular flap and requires no sutures for closure. Although the construction of 2 tunnels is more time consuming than a procedure in which the suture knot is buried through rotation of a full-thickness scleral pass, it is no less efficient than the dissection of 2 triangular flaps. We currently prefer not to rotate knots because of the possibility of suture breakage. In addition, the larger 9-0 and 8-0 recommendations for suture gauges may further impede knot rotation secondary to the larger knot size. The technique does require 2 suture passes that are initially placed through the full thickness of the dissected sclera, including the roof. These punctures appear to heal, as would be the case with any suture pass through scleral tissue, and the knot has not eroded or poked through these perforations since it appears to lie midway between the perforations under nonperforated sclera. Tying the sutures allows the knot to slide under the
J CATARACT REFRACT SURG - VOL 33, JANUARY 2007
3
LETTERS
protection of the roof, and achieving adequate tension has not been an issue. We do recommend not tightening the sutures excessively and perhaps leaving some laxity to avoid cheese-wiring through the scleral bed. In our article, we presented one procedure only (scleral fixation of a large aniridia IOL); however, the tunnel technique can be used for any small-incision IOL or for a procedure that does not require incisions such as fixation of a dislocated IOL or repair of an iridodialysis. The large, temporal clear corneal incision used for the aniridia IOL is not connected with the scleral tunnel. Suture closure of the clear corneal incision incorporates relatively superficial suture passes compared with the depth of the sclerally fixated 9-0 polypropylene (Prolene) sutures. In addition, the scleral sutures are 1.0 mm posterior to the surgical limbus and thus an adequate distance from the clear corneal sutures. Compromise of the sutures, IOL, or tunnel has not been a problem, especially since the tunnel does not enter the anterior chamber. In eyes that are hypotonus and have large incisions or, for that matter, any incision, we recommend placing an anterior chamber (AC) maintainer or pars plana infusion port to avoid complications such as choroidal effusions or hemorrhages. The drawings in our article did not show the AC maintainer to simplify the image; however, it was mentioned in the technique description. The use of a scleral tunnel for scleral fixation is one more technique for surgeons to consider. As with many of our surgical techniques, we believe it represents a small incremental improvement of previous methods and we encourage surgeons to try it. In an upcoming issue, we will describe a further variation of this technique that eliminates the need for conjunctival dissection. We thank Baykara for taking the time to comment on our paper and we appreciate his contribution to this discipline within ophthalmology.dRichard S. Hoffman, MD, I. Howard Fine, MD, Mark Packer, MD, Israel Rozenberg, MD
Functions of the capsular tension ring I would like to make 2 comments about the recent capsular tension ring (CTR) article by Boomer and Jackson.1 1. Can implanting a CTR affect the intraocular (IOL) power formula? In the article, Boomer and Jackson state that the ‘‘CTR sat between the IOL haptics and ciliary body, which raised the question of whether a CTR modifies the effective lens position (ELP) and, ultimately, the accuracy of IOL calculations and refractive outcome.’’ To investigate this issue, Boomer and Jackson conducted the study. A previous study using the Miyake technique2 showed a CTR sitting in the capsular bag after cataract removal. The CTR did not strengthen the capsular bag or alter its anatomical position. When an IOL was placed in the bag, the CTR did not change the IOL’s position. However, if the CTR was larger than the capsular bag, the 2 ends of the CTR overlapped in the bag. If the CTR was smaller than the capsular bag, the CTR did not provide enough tension around the equator of the capsular bag and left a large opening between the 2 ends of the CTR, providing a potential opportunity for lens epithelial cells to migrate to the posterior capsule and eventually contribute to PCO. Based on these findings, a CTR is unlikely to affect the IOL power formula because the position of the IOL in the capsular bag is not affected by a CTR. The study by Boomer and Jackson provides scientific and clinical data to support the earlier study.
4
2. How does a CTR improve refractive outcome? In the article, Boomer and Jackson state ‘‘[t]he CTR subset analysis demonstrated a trend toward more accurate outcomes when using Holladay 2 formula but not SRK/T when compared with contralateral eyes without a CTR. Both formulas showed lower variances in the CTR eyes.’’ Therefore, the authors conclude the CTR not only assisted surgeons in surgery but also improved refractive outcomes and patient satisfaction. Previous studies2–5 suggest the CTR has 2 basic functions: facilitating phacoemulsification during surgery and maintaining IOL centration after surgery in eyes with zonular dehiscence. An in vitro study2 demonstrates that IOL decentration can be avoided when a CTR in implanted in a capsular bag with broken zonules. This finding is supported by clinical studies.3–5 If visual and refractive outcomes are better in eyes with a CTR than in those without a CTR, the CTR should be credited because it prevented IOL tilt and decentration in the eyes with zonular dehiscence after cataract surgery. The CTR is not a refractive device, but implanting a CTR may achieve good visual and refractive outcomes after cataract surgery in eyes with zonular dehiscence. In Boomer and Jackson’s article, the refractive prediction error was used to compare refractive outcomes between eyes with a CTR and those without a CTR. Several factors such as IOL decentration, the time of the postoperative refraction, and the astigmatism-reduction procedure during cataract surgery may have affected the measurement. These factors are critical and must be controlled to achieve accurate measurements. In summary, a CTR can facilitate phacoemulsification during surgery and maintain IOL centration after surgery in eyes with zonular dehiscence. Good visual and refractive outcomes following CTR implantation in these eyes are likely due to IOL centration. RAN SUN, MD Rochester, New York REFERENCES 1. Boomer JA, Jackson DW. Effect of the Morcher capsular tension ring on refractive outcome. J Cataract Refract Surg 2006; 32:1180–1183 2. Sun R, Gimbel HV. In vitro evaluation of the efficacy of the capsular tension ring for managing zonular dialysis in cataract surgery. Ophthalmic Surg 1998; 29:502–505 3. Hara T, Hara T, Yamada Y. ‘‘Equator ring’’ for maintenance of the completely circular contour of the capsular bag equator after cataract removal. Ophthalmic Surg 1991; 22:358–359 4. Cionni RJ, Osher RH. Endocapsular ring approach to the subluxed cataractous lens. J Cataract Refract Surg 1995; 2:245–249 5. Gimbel HV, Sun R, Heston JP. Management of zonular dialysis in phacoemulsification and IOL implantation using the capsular tension ring. Ophthalmic Surg Lasers 1997; 28:273–281
Modified technique for management of LIDRS We were very interested in the series of articles describing various maneuvers to relieve the reverse pupil block in the lens–iris diaphragm retropulsion syndrome (LIDRS).1–3 To relieve LIDRS, it is necessary to separate the posterior surface of the iris from the anterior surface of the anterior capsule. Previous reports describe maneuvers that lift the iris using the tip of the phaco or
J CATARACT REFRACT SURG - VOL 33, JANUARY 2007