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Combined technique: AK and LASIK
LETTERS
References 1. Newsom TH, Oetting TN. Indocyanine green staining in traumatic cataract. J Cataract Refract Surg 2000; 26:1691–1693 2. Hoffer KJ, McFarland JE. Intracameral subcapsular fluorescein staining for improved visualization during capsulorhexis in mature cataracts (letter). J Cataract Refract Surg 1993; 19:566 3. Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the lens capsule for circular continuous capsulorhexis in eyes with white cataract. Arch Ophthalmol 1998; 116:535–537 4. Melles GRJ, Waard PWT, Pameyer JH, Beekhuis WH. Trypan blue capsule staining in cataract surgery. J Cataract Refract Surg 1999; 24:7–9 5. Pandey SK, Werner L, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part I: anterior capsule staining for capsulorhexis in advanced/white cataracts. J Cataract Refract Surg 2000; 26: 1052–1059 6. Werner L, Pandey SK, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part II: an experimental study to learn and perform critical steps of phacoemulsification in human eyes obtained post-mortem. J Cataract Refract Surg 2000; 26: 1060 –1065 7. Pandey SK, Werner L, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part III: staining of the posterior capsule to learn and perform posterior continuous curvilinear capsulorhexis. J Cataract Refract Surg 2000; 26:1066 –1071
Figure 1. (Pandey) Gross photographs of 2 postmortem human eyes after dye-enhanced cataract surgery was performed. Note the staining of the capsular bag with ICG (A) and trypan blue (B). The arrows demonstrate the staining of the residual cortical material in both cases.
the interval between staining and surgery may influence the degree and pattern of staining. The results of our studies of dye-enhanced cataract surgery should be interpreted carefully since postmortem changes in the aqueous humor and human crystalline lens possibly influence the affinity as well as the degree and staining pattern of the anterior capsule and other structures of the capsular bag. Further studies with more cases are needed to reach definitive conclusions concerning the staining of the lens cortex. SURESH K. PANDEY, MD LILIANA WERNER, MD, PHD DAVID J. APPLE, MD Charleston, South Carolina, USA 648
Reply: Thank you for your interesting comments on our article. You point out correctly that we have not made any attempt to explain why the ICG seemed to stain the capsule selectively over the cortical material in our case. Even more interesting are the data you present demonstrating that cortical material does stain in postmortem eyes. Since the case presented in the article, we have gained a bit more experience. We have used ICG in a couple of cases in which we lost the reflex of the anterior capsule among cortical spokes after starting the anterior capsulotomy and exposing cortical material. We irrigated the viscoelastic material, injected some air, and injected ICG. As in the traumatic case described in the article, the ICG seemed to stain the capsule more than the exposed cortical material, which allowed us to complete the capsulorhexis—a nice trick to add to your bag if you ever get into similar trouble. Again, we are not sure of the mechanism, but it does seem that at least under air, ICG has a selective affinity for the capsule over cortical material in this small set of cases.—Thomas A. Oetting, MD
Combined Technique: AK and LASIK
I
would like to comment on the article by Gu¨ell and Vazquez regarding the correction of high degrees of astigmatism using a combination of astigmatic keratotomy (AK) followed by laser in situ keratomileusis (LASIK).1 I, too, have found this approach to be very useful for reducing high levels of astigmatism but with one subtle difference—intralimbal relaxing incisions (LRIs) are used instead of pure corneal (optical zone
J CATARACT REFRACT SURG—VOL 27, MAY 2001
LETTERS
[OZ] ⫽ 6.5 to 7.0 mm.) incisions. Similar to many other surgeons, I have found that these more peripheral incisions are more forgiving, with less tendency to induce irregular corneal flattening and astigmatism; they are less likely to shift the resultant astigmatic axis and to overcorrect (L.D. Nichamin, MD, “Peripheral Arcuate Astigmatic Relaxing Incisions,” presented at the Symposium on Cataract, IOL and Refractive Surgery, Boston, Massachusetts, USA, May 2000). They are, however, less powerful than conventional corneal astigmatic incisions, but when combined with LASIK, nearly all encountered levels of astigmatism are approachable. I have found this combined approach particularly helpful in the following 3 clinical scenarios: (1) the absolute amount of cylinder exceeds the limit for laser ablation; (2) the absolute amount of cylinder could be addressed by excimer treatment, but the resulting elliptical OZ could present potential problems; and (3) until recently approved by the U.S. Food and Drug Administration, the treatment of hyperopic astigmatism. Unpublished data for this combined technique of hyperopic LASIK and LRIs seemed to compare favorably with the most recent reports of hyperopic astigmatic LASIK; the technique spared more tissue than the “double-carding” approach (spherical hyperopic correction followed by myopic cylinder ablation) practiced by some U.S. surgeons. In my experience, an additional advantage of intralimbal arcuate relaxing incisions over smaller OZ AK is their more consistent 1:1 coupling ratio, with little effect on the resulting spheroequivalent (SE). Gu¨ell and Vazquez report that the SE refraction changed from ⫺1.66 ⫾ 2.65 diopters (D) to 0.30 ⫾ 1.27 D in the naturally occurring astigmatic groups and from ⫺6.12 ⫾ 6.89 D to ⫺1.87 ⫾ 1.50 D in the surgically induced group, indicating a substantial hyperopic shift. It is presumed that this shift in SE was intentionally accomplished during the second ablation step. (Final mean SE was an impressive ⫺0.09 ⫾ 1.50 D.) The change in SE after AK alone was not reported; however, given the superior results of laser ablation for myopic astigmatism compared to hyperopic astigmatism, it would seem preferable that the initial relaxing incisions not induce a hyperopic shift, which in my experience can occur (quite inconsistently) with AK at the 6.0 to 7.0 mm OZ.
I congratulate these authors on recognizing the usefulness of combining astigmatic relaxing incisions with LASIK to treat higher levels of astigmatism. With refinements in ablation technique such as crossed-cylinder treatment (with further tissue sparing), this combined approach may become unnecessary. LOUIS D. NICHAMIN, MD Brookville, Pennsylvania, USA Reference 1. Gu¨ell JL, Vazquez M. Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis. J Cataract Refract Surg 2000; 26:960 –966
Reply: We would like to thank Dr. Nichamin for his interesting comments. We have no personal experience with LRIs, which have been classically indicated at the time of cataract surgery to reduce the final cylinder.1 We do not like this combination because we prefer to combine only the design and location of the entry incisions at the time of lens surgery and to leave the final fine tuning, if necessary, to a second surgery, typically LASIK. Considering Dr. Nichamin’s experience with both techniques, LRIs and pure corneal AK, both combinations are probably useful in the management of high astigmatism. Most eyes treated in our series were in young people (high regression rate after incisional corneal surgery) with high levels of myopic astigmatism or mixed astigmatism. In both situations, it was especially important to maximally reduce the cylinder to reduce the ablation depth in the second procedure (first group) or to possibly eliminate the need of a second procedure (second group). For this reason, we think a more powerful technique at the 7.0 mm corneal OZ is indicated. On the other hand, during our experience with transverse keratotomy to correct high astigmatism after cataract surgery, we observed that both irregular residual astigmatism and hyperopic shift were not uncommon, particularly when we were working with 5.5 and 6.0 mm OZs. With arcuate instead of transverse and with a standard 7.0 mm OZ, both complications are extremely uncommon, particularly the hyperopic shift. (We have not seen a single case.) Finally, we agree with Dr. Nichamin that in our daily practice, the new ablation profile techniques for astigmatism (crossed cylinder) have reduced the need of these combinations, but they are still extremely helpful in 3 groups of patients: (1) those with high myopic astigmatism, especially cases with a cylinder higher than the sphere, because we drastically reduce the final required ablation depth and increase predictability; (2) those with mixed astigmatism with an SE equal or close to 0, because with a single procedure to correct the ametropia, we avoid manipulating the central cornea; and (3) those with residual astigmatism after penetrating keratoplasty, because we have to work inside the trephination line (against limbal) and because we try to maximally reduce the ablation
J CATARACT REFRACT SURG—VOL 27, MAY 2001
649
References 1. Newsom TH, Oetting TN. Indocyanine green staining in traumatic cataract. J Cataract Refract Surg 2000; 26:1691–1693 2. Hoffer KJ, McFarland JE. Intracameral subcapsular fluorescein staining for improved visualization during capsulorhexis in mature cataracts (letter). J Cataract Refract Surg 1993; 19:566 3. Horiguchi M, Miyake K, Ohta I, Ito Y. Staining of the lens capsule for circular continuous capsulorhexis in eyes with white cataract. Arch Ophthalmol 1998; 116:535–537 4. Melles GRJ, Waard PWT, Pameyer JH, Beekhuis WH. Trypan blue capsule staining in cataract surgery. J Cataract Refract Surg 1999; 24:7–9 5. Pandey SK, Werner L, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part I: anterior capsule staining for capsulorhexis in advanced/white cataracts. J Cataract Refract Surg 2000; 26: 1052–1059 6. Werner L, Pandey SK, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part II: an experimental study to learn and perform critical steps of phacoemulsification in human eyes obtained post-mortem. J Cataract Refract Surg 2000; 26: 1060 –1065 7. Pandey SK, Werner L, Escobar-Gomez M, et al. Dye-enhanced cataract surgery. Part III: staining of the posterior capsule to learn and perform posterior continuous curvilinear capsulorhexis. J Cataract Refract Surg 2000; 26:1066 –1071
Figure 1. (Pandey) Gross photographs of 2 postmortem human eyes after dye-enhanced cataract surgery was performed. Note the staining of the capsular bag with ICG (A) and trypan blue (B). The arrows demonstrate the staining of the residual cortical material in both cases.
the interval between staining and surgery may influence the degree and pattern of staining. The results of our studies of dye-enhanced cataract surgery should be interpreted carefully since postmortem changes in the aqueous humor and human crystalline lens possibly influence the affinity as well as the degree and staining pattern of the anterior capsule and other structures of the capsular bag. Further studies with more cases are needed to reach definitive conclusions concerning the staining of the lens cortex. SURESH K. PANDEY, MD LILIANA WERNER, MD, PHD DAVID J. APPLE, MD Charleston, South Carolina, USA 648
Reply: Thank you for your interesting comments on our article. You point out correctly that we have not made any attempt to explain why the ICG seemed to stain the capsule selectively over the cortical material in our case. Even more interesting are the data you present demonstrating that cortical material does stain in postmortem eyes. Since the case presented in the article, we have gained a bit more experience. We have used ICG in a couple of cases in which we lost the reflex of the anterior capsule among cortical spokes after starting the anterior capsulotomy and exposing cortical material. We irrigated the viscoelastic material, injected some air, and injected ICG. As in the traumatic case described in the article, the ICG seemed to stain the capsule more than the exposed cortical material, which allowed us to complete the capsulorhexis—a nice trick to add to your bag if you ever get into similar trouble. Again, we are not sure of the mechanism, but it does seem that at least under air, ICG has a selective affinity for the capsule over cortical material in this small set of cases.—Thomas A. Oetting, MD
Combined Technique: AK and LASIK
I
would like to comment on the article by Gu¨ell and Vazquez regarding the correction of high degrees of astigmatism using a combination of astigmatic keratotomy (AK) followed by laser in situ keratomileusis (LASIK).1 I, too, have found this approach to be very useful for reducing high levels of astigmatism but with one subtle difference—intralimbal relaxing incisions (LRIs) are used instead of pure corneal (optical zone
J CATARACT REFRACT SURG—VOL 27, MAY 2001
LETTERS
[OZ] ⫽ 6.5 to 7.0 mm.) incisions. Similar to many other surgeons, I have found that these more peripheral incisions are more forgiving, with less tendency to induce irregular corneal flattening and astigmatism; they are less likely to shift the resultant astigmatic axis and to overcorrect (L.D. Nichamin, MD, “Peripheral Arcuate Astigmatic Relaxing Incisions,” presented at the Symposium on Cataract, IOL and Refractive Surgery, Boston, Massachusetts, USA, May 2000). They are, however, less powerful than conventional corneal astigmatic incisions, but when combined with LASIK, nearly all encountered levels of astigmatism are approachable. I have found this combined approach particularly helpful in the following 3 clinical scenarios: (1) the absolute amount of cylinder exceeds the limit for laser ablation; (2) the absolute amount of cylinder could be addressed by excimer treatment, but the resulting elliptical OZ could present potential problems; and (3) until recently approved by the U.S. Food and Drug Administration, the treatment of hyperopic astigmatism. Unpublished data for this combined technique of hyperopic LASIK and LRIs seemed to compare favorably with the most recent reports of hyperopic astigmatic LASIK; the technique spared more tissue than the “double-carding” approach (spherical hyperopic correction followed by myopic cylinder ablation) practiced by some U.S. surgeons. In my experience, an additional advantage of intralimbal arcuate relaxing incisions over smaller OZ AK is their more consistent 1:1 coupling ratio, with little effect on the resulting spheroequivalent (SE). Gu¨ell and Vazquez report that the SE refraction changed from ⫺1.66 ⫾ 2.65 diopters (D) to 0.30 ⫾ 1.27 D in the naturally occurring astigmatic groups and from ⫺6.12 ⫾ 6.89 D to ⫺1.87 ⫾ 1.50 D in the surgically induced group, indicating a substantial hyperopic shift. It is presumed that this shift in SE was intentionally accomplished during the second ablation step. (Final mean SE was an impressive ⫺0.09 ⫾ 1.50 D.) The change in SE after AK alone was not reported; however, given the superior results of laser ablation for myopic astigmatism compared to hyperopic astigmatism, it would seem preferable that the initial relaxing incisions not induce a hyperopic shift, which in my experience can occur (quite inconsistently) with AK at the 6.0 to 7.0 mm OZ.
I congratulate these authors on recognizing the usefulness of combining astigmatic relaxing incisions with LASIK to treat higher levels of astigmatism. With refinements in ablation technique such as crossed-cylinder treatment (with further tissue sparing), this combined approach may become unnecessary. LOUIS D. NICHAMIN, MD Brookville, Pennsylvania, USA Reference 1. Gu¨ell JL, Vazquez M. Correction of high astigmatism with astigmatic keratotomy combined with laser in situ keratomileusis. J Cataract Refract Surg 2000; 26:960 –966
Reply: We would like to thank Dr. Nichamin for his interesting comments. We have no personal experience with LRIs, which have been classically indicated at the time of cataract surgery to reduce the final cylinder.1 We do not like this combination because we prefer to combine only the design and location of the entry incisions at the time of lens surgery and to leave the final fine tuning, if necessary, to a second surgery, typically LASIK. Considering Dr. Nichamin’s experience with both techniques, LRIs and pure corneal AK, both combinations are probably useful in the management of high astigmatism. Most eyes treated in our series were in young people (high regression rate after incisional corneal surgery) with high levels of myopic astigmatism or mixed astigmatism. In both situations, it was especially important to maximally reduce the cylinder to reduce the ablation depth in the second procedure (first group) or to possibly eliminate the need of a second procedure (second group). For this reason, we think a more powerful technique at the 7.0 mm corneal OZ is indicated. On the other hand, during our experience with transverse keratotomy to correct high astigmatism after cataract surgery, we observed that both irregular residual astigmatism and hyperopic shift were not uncommon, particularly when we were working with 5.5 and 6.0 mm OZs. With arcuate instead of transverse and with a standard 7.0 mm OZ, both complications are extremely uncommon, particularly the hyperopic shift. (We have not seen a single case.) Finally, we agree with Dr. Nichamin that in our daily practice, the new ablation profile techniques for astigmatism (crossed cylinder) have reduced the need of these combinations, but they are still extremely helpful in 3 groups of patients: (1) those with high myopic astigmatism, especially cases with a cylinder higher than the sphere, because we drastically reduce the final required ablation depth and increase predictability; (2) those with mixed astigmatism with an SE equal or close to 0, because with a single procedure to correct the ametropia, we avoid manipulating the central cornea; and (3) those with residual astigmatism after penetrating keratoplasty, because we have to work inside the trephination line (against limbal) and because we try to maximally reduce the ablation
J CATARACT REFRACT SURG—VOL 27, MAY 2001
649