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Choroidal neovascularization after LASIK in a patient with low myopia
LETTERS
4. Enoch JM, Hope GM. An analysis of retinal receptor orientation. IV. Center of the entrance pupil and the center of convergence of orientation and directional sensitivity. Invest Ophthalmol 1972; 11:1017–1021 5. Yang Y, Thompson K, Burns SA. Pupil location under mesopic, photopic, and pharmacologically dilated conditions. Invest Ophthalmol Vis Sci 2002; 43:2508–2512 6. Schachar RA. Effect of accommodation on the cornea [letter]. J Cataract Refract Surg 2004; 30:531–532 7. Kirkwood BR, Sterne JAC. Essential Medical Statistics, 2nd ed. Malden, MA, Blackwell, 2003; 61–63 8. Indrayan A, Sarmukaddam SB. Medical Biostatistics. New York, NY, Marcel Dekker, 2001; 505–511 9. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307–310
Laser iridoplasty for congenital ectopic pupils A recent Consultation Section1 in which a healthy 25-year old man with congenital ectopic pupils and lenses was presented failed to include any responses suggesting laser iridoplasty for the patient’s right eye. In my experience, such a procedure could serve as the sole and definitive management of this eye. Rings of confluent spots can be placed using a green wavelength, thermal laser (such as a solid-state 532 nm or an argon– green laser) and delivered via an Abraham or the center of a 3-mirror lens, with a 0.5 s duration and 500 mm spot size at low enough power to cause stromal contraction without charring the tissue or forming bubbles. This iridoplasty technique will reliably allow the surgeon to enlarge and shape the pupil with a great degree of control. By placing these spots within the quadrant from 3:00 to 6:00 o’clock, the pupil could be moved inferonasally and enlarged to encompass the center of the crystalline lens and at least to or past the diameter shown at 4:30 in the postdilation photo. Since all treatment would be placed 180 degrees away, the superotemporal border of the pupil would move closer to or even perhaps cover the lens equator (which, in Figure 2, appears to be placed inferotemporally rather than temporally. The crystalline lens was clear and without visible phacodonesis, so this treatment modality could preserve accommodation as well as avoid risks related to intraocular surgery. Even if lensectomy were necessary subsequently, iris management would be greatly simplified as a result of the laser procedure. JOEL SHUGAR, MD Perry, Florida, USA REFERENCE 1. Masket S, ed. Consultation section: cataract surgical problem. J Cataract Refract Surg 2004; 30:2035–2049
inclusion criteria had been the same in both groups. There are 2 separate groups in the study. The phakic IOL group had a mean age of 35.7 years (range 32 to 43 years), whereas the CLE group had a mean age of 44.6 years (range 36 to 49 years). Also, the mean preoperative spherical equivalent refractive error was ÿ13.6 G 3.0 diopters (D) in the phakic IOL group and ÿ16.7 G 3.8 D in the CLE group. We think these are distinct groups and cannot be compared with each other. We also think that all the patients should be unilaterally or bilaterally recruited to increase the strength of the study. We would also like to clarify that the implantable contact lens from Staar is hydrophilic acrylic and not hydrophobic acrylic. In the CLE group, a retinal detachment occurred in 2 cases. Both were implanted with a poly(methyl methacrylate) IOL, and a neodymium:YAG (Nd:YAG) capsulotomy was performed to treat posterior capsule opacification. Using modern foldable IOLs with sharp edges results in a lower incidence of PCO and complications following Nd:YAG capsulotomy.1–4 We think it would have been more appropriate if the same foldable IOL had been implanted in all CLE cases. Also, the patients in the CLE group were older and more myopic. Both these preexisting factors are known to predispose to retinal detachment.3,5 Finally, although the author explained the postsurgical satisfaction, the reference on the description of the satisfaction scale is missing. A prospective randomized trial comparing these 2 methods would be more conclusive and desirable. MAYANK A. NANAVATY, DO ABHAY R. VASAVADA, MS, FRCS Ahmedabad, India CHARLOTTA ZETTERSTRO¨M, MD, PHD Stockholm, Sweden REFERENCES 1. Arne JL. Phakic intraocular lens implantation versus clear lens extraction in highly myopic eyes of 30- to 50-year-old patients. J Cataract Refract Surg 2004; 30:2092–2096 2. Hayashi K, Hayashi H, Nakao F, Hayashi F. Changes in posterior capsule opacification after poly(methyl methacrylate), silicone, and acrylic intraocular lens implantation. J Cataract Refract Surg 2001; 27:817–824 3. Jahn CE, Richter J, Jahn AH, et al. Pseudophakic retinal detachment after uneventful phacoemulsification and subsequent neodymium:YAG capsulotomy for capsule opacification. J Cataract Refract Surg 2003; 29:925–929 4. Ranta P, Tommila P, Immonen I, et al. Retinal breaks before and after neodymium:YAG posterior capsulotomy. J Cataract Refract Surg 2000; 26:1190–1197 5. Tielsch JM, Legro MW, Cassard SD, et al. Risk factors for retinal detachment after cataract surgery; a population-based case-control study. Ophthalmology 1996; 103:1537–1545
Phakic IOL implantation versus clear lens extraction in highly myopic eyes
Choroidal neovascularization after LASIK in a patient with low myopia
We appreciate Arne’s idea of comparing phakic intraocular lens (IOL) implantation and clear lens extraction (CLE) in highly myopic eyes.1 However, we would like to comment on a few aspects of the study. The results would have been more conclusive if the
Saeed et al.1 report a single case of choroidal neovascularization (CNV) 3 months after laser in situ keratomileusis (LASIK) for low myopia. After a discussion featuring indefinite terms such
J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005
2041
LETTERS
as ‘‘could,’’ ‘‘probably,’’ and ‘‘possibly,’’ they conclude, ‘‘. potential risks of LASIK outweigh its benefits.’’ I believe there are 2 errors in the authors’ analysis. First, they group the affected eye, which had ÿ2.75 diopters (D) of myopia, with eyes that had more than ÿ13.00 D. Second, they define a risk for all eyes with low myopia having LASIK on the basis of a single case. Eyes with myopia greater than ÿ6.00 D, in which the basic abnormality is excessive axial elongation, are known to be at increased risk for CNV.2,3 The authors admit an incidence of CNV in high myopia of 5% to 10% but do not present evidence for a higher incidence in highly myopic eyes that have had LASIK. Also, CNV is common in some general populations, with an incidence between 0.4% and 1.1% in people older than 43 years4 and up to 3.5% in the elderly.5 Without proper assessment of the incidence of CNV after LASIK for low myopia and comparison with a matched control group, this report remains an isolated novelty. Therefore, I suggest the authors’ conclusions are presently unfounded and should be moderated. C.S. BAILEY, FRCS, FRCOPHTH London, United Kingdom REFERENCES 1. Saeed M, Poon W, Goyal S, et al. Choroidal neovascularization after laser in situ keratomilejsis in a patient with low myopia. J Cataract Refract Surg 2004; 30:2632–2635 2. Avila MP, Weiter JJ, Jalkh AE, et al. Natural history of choroidal neovascularization in degenerative myopia. Ophthalmology 1984; 91:1573– 1580; discussion by BJ Curtin, 1580–1581 3. Hotchkiss ML, Fine SL. Pathologic myopia and choroidal neovascularization. Am J Ophthalmol 1981; 91:177–183 4. Tomany SC, Wang JJ, van Leeuwen R, et al. Risk factors for incident agerelated macular degeneration; pooled findings for 3 continents. Ophthalmology 2004; 111:1280–1287 5. Gregor Z, Joffe L. Senile macular changes in black African. Br J Ophthalmol 1978; 62:547–550
Relationship between anterior capsule contraction and posterior capsule opacification after cataract surgery in patients with diabetes mellitus Hayashi et al.1 have demonstrated the absence of a correlation between contraction of the anterior capsule opening and the density of posterior capsule opacification (PCO) 1 year after uneventful phacoemulsification and acrylic foldable intraocular lens implantation in patients with diabetes mellitus. In any study of PCO, the fundamental issue is the objective documentation of opacification.2 In the study by Hayashi et al., Scheimpflug videography measuring slit images over only small areas of the posterior capsule was used. Scheimpflug videography is good for indicating PCO severity and has good correlation with patients’ visual acuity. It, however, has the drawback that any areas of involvement
2042
beyond the meridians of analysis may be missed and a significant portion of off-meridian PCO is overlooked thereafter. The overexpression or underexpression of the results may affect our understanding of the etiology or pathogenesis of PCO.2 Another downside of this study is the failure to address the natural progression of PCO and the exact timeframe of measurement. Posterior capsule opacification usually begins with capsule fibrosis, gradually evolving into Elschnig pearls.3,4 According to Hayashi et al., only capsule fibrosis is the common pathogenesis underpinning both anterior capsule opening contraction and PCO formation.1 However, the 1-year Scheimpflug videography findings revealed pearl-type PCO rather than capsule fibrosis.1 This observation was believed to be the major cause of the lack of a correlation over time.1 It is important to note that the PCO imaging system adopted, Scheimpflug videography, might not be able to detect progression, as pointed out by Aslam et al.5 and Friedman et al.6 More sensitive and specific methods of capturing PCO, including Tetz’s computerized analysis of density boundaries and the density map system of Friedman et al. should be considered as viable alternates. Finally, Hayashi et al. conclude that contraction of the anterior capsule opening and PCO after cataract surgery cannot be explained by a common mechanism. We do not concur with the authors’ interpretation of correlation coefficient. The absence of a positive or negative correlation between 2 variables cannot extirpate the possibility that both are under the direct influence of a common mechanism, pathogenesis, or unobserved factor. There could have been many confounding factors influencing the variables to different extents and magnitudes. One of them was the protective effect of an acrylic foldable IOL, which has been shown to lower the PCO rate significantly. We do not think the authors’ conclusion cannot be drawn or implied objectively and logically from the observed results. DAVID T.L. LIU, MRCS VESTA C.K. CHAN, MB CHB WAI-MAN CHAN, FRCP, FRCS DENNIS S.C. LAM, MD, FRCOPHTH Hong Kong, China REFERENCES 1. Hayashi Y, Kato S, Fukushima H, et al. Relationship between anterior capsule contraction and posterior capsule opacification after cataract surgery in patients with diabetes mellitus. J Cataract Refract Surg 2004; 30:1517–1520 2. Spalton DJ. Methods of quantifying posterior capsule opacification [letter]. J Cataract Refract Surg 2003; 29:1247 3. Caballero A, Garcia-Elskamp C, Losada M, et al. Natural evolution of Elschnig pearl posterior capsule opacification after posterior capsulotomy. J Cataract Refract Surg 2001; 27:1979–1986 4. Caballero A, Marı´n JM, Salinas M. Spontaneous regression of Elschnig pearl posterior capsule opacification. J Cataract Refract Surg 2000; 26:779–780 5. Aslam TM, Dhillon B, Werghi N, et al. Systems of analysis of posterior capsule opacification. Br J Ophthalmol 2002; 86:1181–1186 6. Friedman DS, Duncan DD, Munoz B, et al. Digital image capture and automated analysis of posterior capsular opacification. Invest Ophthalmol Vis Sci 1999; 40:1715–1726
J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005
4. Enoch JM, Hope GM. An analysis of retinal receptor orientation. IV. Center of the entrance pupil and the center of convergence of orientation and directional sensitivity. Invest Ophthalmol 1972; 11:1017–1021 5. Yang Y, Thompson K, Burns SA. Pupil location under mesopic, photopic, and pharmacologically dilated conditions. Invest Ophthalmol Vis Sci 2002; 43:2508–2512 6. Schachar RA. Effect of accommodation on the cornea [letter]. J Cataract Refract Surg 2004; 30:531–532 7. Kirkwood BR, Sterne JAC. Essential Medical Statistics, 2nd ed. Malden, MA, Blackwell, 2003; 61–63 8. Indrayan A, Sarmukaddam SB. Medical Biostatistics. New York, NY, Marcel Dekker, 2001; 505–511 9. Bland JM, Altman DG. Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986; 1:307–310
Laser iridoplasty for congenital ectopic pupils A recent Consultation Section1 in which a healthy 25-year old man with congenital ectopic pupils and lenses was presented failed to include any responses suggesting laser iridoplasty for the patient’s right eye. In my experience, such a procedure could serve as the sole and definitive management of this eye. Rings of confluent spots can be placed using a green wavelength, thermal laser (such as a solid-state 532 nm or an argon– green laser) and delivered via an Abraham or the center of a 3-mirror lens, with a 0.5 s duration and 500 mm spot size at low enough power to cause stromal contraction without charring the tissue or forming bubbles. This iridoplasty technique will reliably allow the surgeon to enlarge and shape the pupil with a great degree of control. By placing these spots within the quadrant from 3:00 to 6:00 o’clock, the pupil could be moved inferonasally and enlarged to encompass the center of the crystalline lens and at least to or past the diameter shown at 4:30 in the postdilation photo. Since all treatment would be placed 180 degrees away, the superotemporal border of the pupil would move closer to or even perhaps cover the lens equator (which, in Figure 2, appears to be placed inferotemporally rather than temporally. The crystalline lens was clear and without visible phacodonesis, so this treatment modality could preserve accommodation as well as avoid risks related to intraocular surgery. Even if lensectomy were necessary subsequently, iris management would be greatly simplified as a result of the laser procedure. JOEL SHUGAR, MD Perry, Florida, USA REFERENCE 1. Masket S, ed. Consultation section: cataract surgical problem. J Cataract Refract Surg 2004; 30:2035–2049
inclusion criteria had been the same in both groups. There are 2 separate groups in the study. The phakic IOL group had a mean age of 35.7 years (range 32 to 43 years), whereas the CLE group had a mean age of 44.6 years (range 36 to 49 years). Also, the mean preoperative spherical equivalent refractive error was ÿ13.6 G 3.0 diopters (D) in the phakic IOL group and ÿ16.7 G 3.8 D in the CLE group. We think these are distinct groups and cannot be compared with each other. We also think that all the patients should be unilaterally or bilaterally recruited to increase the strength of the study. We would also like to clarify that the implantable contact lens from Staar is hydrophilic acrylic and not hydrophobic acrylic. In the CLE group, a retinal detachment occurred in 2 cases. Both were implanted with a poly(methyl methacrylate) IOL, and a neodymium:YAG (Nd:YAG) capsulotomy was performed to treat posterior capsule opacification. Using modern foldable IOLs with sharp edges results in a lower incidence of PCO and complications following Nd:YAG capsulotomy.1–4 We think it would have been more appropriate if the same foldable IOL had been implanted in all CLE cases. Also, the patients in the CLE group were older and more myopic. Both these preexisting factors are known to predispose to retinal detachment.3,5 Finally, although the author explained the postsurgical satisfaction, the reference on the description of the satisfaction scale is missing. A prospective randomized trial comparing these 2 methods would be more conclusive and desirable. MAYANK A. NANAVATY, DO ABHAY R. VASAVADA, MS, FRCS Ahmedabad, India CHARLOTTA ZETTERSTRO¨M, MD, PHD Stockholm, Sweden REFERENCES 1. Arne JL. Phakic intraocular lens implantation versus clear lens extraction in highly myopic eyes of 30- to 50-year-old patients. J Cataract Refract Surg 2004; 30:2092–2096 2. Hayashi K, Hayashi H, Nakao F, Hayashi F. Changes in posterior capsule opacification after poly(methyl methacrylate), silicone, and acrylic intraocular lens implantation. J Cataract Refract Surg 2001; 27:817–824 3. Jahn CE, Richter J, Jahn AH, et al. Pseudophakic retinal detachment after uneventful phacoemulsification and subsequent neodymium:YAG capsulotomy for capsule opacification. J Cataract Refract Surg 2003; 29:925–929 4. Ranta P, Tommila P, Immonen I, et al. Retinal breaks before and after neodymium:YAG posterior capsulotomy. J Cataract Refract Surg 2000; 26:1190–1197 5. Tielsch JM, Legro MW, Cassard SD, et al. Risk factors for retinal detachment after cataract surgery; a population-based case-control study. Ophthalmology 1996; 103:1537–1545
Phakic IOL implantation versus clear lens extraction in highly myopic eyes
Choroidal neovascularization after LASIK in a patient with low myopia
We appreciate Arne’s idea of comparing phakic intraocular lens (IOL) implantation and clear lens extraction (CLE) in highly myopic eyes.1 However, we would like to comment on a few aspects of the study. The results would have been more conclusive if the
Saeed et al.1 report a single case of choroidal neovascularization (CNV) 3 months after laser in situ keratomileusis (LASIK) for low myopia. After a discussion featuring indefinite terms such
J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005
2041
LETTERS
as ‘‘could,’’ ‘‘probably,’’ and ‘‘possibly,’’ they conclude, ‘‘. potential risks of LASIK outweigh its benefits.’’ I believe there are 2 errors in the authors’ analysis. First, they group the affected eye, which had ÿ2.75 diopters (D) of myopia, with eyes that had more than ÿ13.00 D. Second, they define a risk for all eyes with low myopia having LASIK on the basis of a single case. Eyes with myopia greater than ÿ6.00 D, in which the basic abnormality is excessive axial elongation, are known to be at increased risk for CNV.2,3 The authors admit an incidence of CNV in high myopia of 5% to 10% but do not present evidence for a higher incidence in highly myopic eyes that have had LASIK. Also, CNV is common in some general populations, with an incidence between 0.4% and 1.1% in people older than 43 years4 and up to 3.5% in the elderly.5 Without proper assessment of the incidence of CNV after LASIK for low myopia and comparison with a matched control group, this report remains an isolated novelty. Therefore, I suggest the authors’ conclusions are presently unfounded and should be moderated. C.S. BAILEY, FRCS, FRCOPHTH London, United Kingdom REFERENCES 1. Saeed M, Poon W, Goyal S, et al. Choroidal neovascularization after laser in situ keratomilejsis in a patient with low myopia. J Cataract Refract Surg 2004; 30:2632–2635 2. Avila MP, Weiter JJ, Jalkh AE, et al. Natural history of choroidal neovascularization in degenerative myopia. Ophthalmology 1984; 91:1573– 1580; discussion by BJ Curtin, 1580–1581 3. Hotchkiss ML, Fine SL. Pathologic myopia and choroidal neovascularization. Am J Ophthalmol 1981; 91:177–183 4. Tomany SC, Wang JJ, van Leeuwen R, et al. Risk factors for incident agerelated macular degeneration; pooled findings for 3 continents. Ophthalmology 2004; 111:1280–1287 5. Gregor Z, Joffe L. Senile macular changes in black African. Br J Ophthalmol 1978; 62:547–550
Relationship between anterior capsule contraction and posterior capsule opacification after cataract surgery in patients with diabetes mellitus Hayashi et al.1 have demonstrated the absence of a correlation between contraction of the anterior capsule opening and the density of posterior capsule opacification (PCO) 1 year after uneventful phacoemulsification and acrylic foldable intraocular lens implantation in patients with diabetes mellitus. In any study of PCO, the fundamental issue is the objective documentation of opacification.2 In the study by Hayashi et al., Scheimpflug videography measuring slit images over only small areas of the posterior capsule was used. Scheimpflug videography is good for indicating PCO severity and has good correlation with patients’ visual acuity. It, however, has the drawback that any areas of involvement
2042
beyond the meridians of analysis may be missed and a significant portion of off-meridian PCO is overlooked thereafter. The overexpression or underexpression of the results may affect our understanding of the etiology or pathogenesis of PCO.2 Another downside of this study is the failure to address the natural progression of PCO and the exact timeframe of measurement. Posterior capsule opacification usually begins with capsule fibrosis, gradually evolving into Elschnig pearls.3,4 According to Hayashi et al., only capsule fibrosis is the common pathogenesis underpinning both anterior capsule opening contraction and PCO formation.1 However, the 1-year Scheimpflug videography findings revealed pearl-type PCO rather than capsule fibrosis.1 This observation was believed to be the major cause of the lack of a correlation over time.1 It is important to note that the PCO imaging system adopted, Scheimpflug videography, might not be able to detect progression, as pointed out by Aslam et al.5 and Friedman et al.6 More sensitive and specific methods of capturing PCO, including Tetz’s computerized analysis of density boundaries and the density map system of Friedman et al. should be considered as viable alternates. Finally, Hayashi et al. conclude that contraction of the anterior capsule opening and PCO after cataract surgery cannot be explained by a common mechanism. We do not concur with the authors’ interpretation of correlation coefficient. The absence of a positive or negative correlation between 2 variables cannot extirpate the possibility that both are under the direct influence of a common mechanism, pathogenesis, or unobserved factor. There could have been many confounding factors influencing the variables to different extents and magnitudes. One of them was the protective effect of an acrylic foldable IOL, which has been shown to lower the PCO rate significantly. We do not think the authors’ conclusion cannot be drawn or implied objectively and logically from the observed results. DAVID T.L. LIU, MRCS VESTA C.K. CHAN, MB CHB WAI-MAN CHAN, FRCP, FRCS DENNIS S.C. LAM, MD, FRCOPHTH Hong Kong, China REFERENCES 1. Hayashi Y, Kato S, Fukushima H, et al. Relationship between anterior capsule contraction and posterior capsule opacification after cataract surgery in patients with diabetes mellitus. J Cataract Refract Surg 2004; 30:1517–1520 2. Spalton DJ. Methods of quantifying posterior capsule opacification [letter]. J Cataract Refract Surg 2003; 29:1247 3. Caballero A, Garcia-Elskamp C, Losada M, et al. Natural evolution of Elschnig pearl posterior capsule opacification after posterior capsulotomy. J Cataract Refract Surg 2001; 27:1979–1986 4. Caballero A, Marı´n JM, Salinas M. Spontaneous regression of Elschnig pearl posterior capsule opacification. J Cataract Refract Surg 2000; 26:779–780 5. Aslam TM, Dhillon B, Werghi N, et al. Systems of analysis of posterior capsule opacification. Br J Ophthalmol 2002; 86:1181–1186 6. Friedman DS, Duncan DD, Munoz B, et al. Digital image capture and automated analysis of posterior capsular opacification. Invest Ophthalmol Vis Sci 1999; 40:1715–1726
J CATARACT REFRACT SURG - VOL 31, NOVEMBER 2005