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Pseudoexfoliation
Letters to the Editor about the graft rejection episodes after Descemet’s stripping automated endothelial keratoplasty (DSAEK) and its influence on the endothelial cell loss. It is generally believed that the risk of graft rejection following DSAEK is lower than penetrating keratoplasty,2 and therefore may require a less aggressive management with topical steroids. However, the authors’ study is insightful as they show concerns about discontinuing steroids prematurely and the practice of steroid withdrawal after 1 year of follow up. Of the 5 cases of rejection seen within the first 6 months in the study group, 3 (60%) were due to discontinuing steroids. The cumulative probability of graft rejection also shows an increasing trend with time. This is most likely attributed to the practice of discontinuation of steroid after 1 year of surgery. The authors’ observations clearly demonstrate that the risk of rejection is considerably higher in endothelial dysfunctions associated with comorbid conditions (8 of 24 or 33.3%) compared to Fuchs’ endothelial dystrophy (45 of 615 or 7.3%). We notice that there is a discrepancy in the total number of graft rejections in the subjects excluded from the study as the actual number of graft rejections adds up to 7. Were there 2 episodes of rejection in the same patient or was this merely a typographical error? What was the time frame of graft rejections seen in these cases excluded from the analysis? It is interesting to observe that in this excluded group, 3 of 7 (42.8%) cases with rejection had a prior glaucoma filtering surgery. Were these patients on a different (lower) dosage of steroid regimen on account of the coexisting pathology, which would probably mean a more vulnerable situation for graft rejection? SUNITA CHAURASIA, MD MURALIDHAR RAMAPPA, MD HARSHA LAXMANA RAO, MD PIYUSH BANSAL, MD Hyderabad, India
were excluded from analysis ranged from 12 to 39 months with a mean time of 20 months. Chaurasia et al1 bring up a very interesting question regarding the steroid regimen as a factor for increased risk of graft rejection. They note that in our group of patients with other ocular comorbidities that excluded them from the study analysis, there were 3 cases of rejection out of 7 eyes with prior glaucoma filtering surgery. We have subsequently reviewed these patients who were excluded due to prior glaucoma filtering surgery. We found that of these seven eyes, 4 of 7 (57.1%) were indeed placed on a lower dosage of steroid than our standard postoperative regimen (either loteprednol etabonate 0.5% or fluorometholone 0.1% as opposed to prednisolone acetate 1%) during the first postoperative year due to concerns about steroid-response elevations in intraocular pressure. However, of the 3 eyes in this group that subsequently developed a graft rejection episode, only one was on fluorometholone 0.1% at the time of their rejection episode. Thus, although the data set is too small to reach a statistically significant conclusion, in our patients with prior glaucoma filtering surgery it does not appear that a lower dosage of steroid led to an increased vulnerability to graft rejection. The issue of graft rejection in the context of endothelial keratoplasty, glaucoma filtering surgery, and the ideal steroid regimen is one that deserves more careful study. This is certainly not a new concern to keratoplasty surgery in general, but remains an important one for us to continue to address as we look toward improving the outcomes of our patients in the future. JENNIFER Y. LI, MD Sacramento, California MARK A. TERRY, MD Portland, Oregon JEFFREY GOSHE, MD Cleveland, Ohio
References 1. Li JY, Terry MA, Goshe J, et al. Graft rejection after Descemet’s stripping automated endothelial keratoplasty: graft survival and endothelial cell loss. Ophthalmology 2012;119: 90 – 4. 2. Allan B, Terry MA, Price FW, et al. Corneal transplant rejection rate and severity after endothelial keratoplasty. Cornea 2007;26:1039 – 42.
Author reply Dear Editor: We appreciate the interest that Chaurasia et al have expressed with regard to our article entitled, “Graft rejection after Descemet’s stripping automated endothelial keratoplasty.”1 We hope that we may clarify some aspects of the article in response to the questions they have raised. Regarding the discrepancy in the total number of graft rejections in subjects excluded from the study, this is a typographical error. There were a total of 7 graft rejections in patients excluded from the study for ocular comorbidities. The time frame for these graft rejection episodes that
DAVID DAVIS-BOOZER, MPH Portland, Oregon Reference 1. Li JY, Terry MA, Goshe J, et al. Graft rejection after Descemet’s stripping automated endothelial keratoplasty: graft survival and endothelial cell loss. Ophthalmology 2012;119:90 – 4.
Pseudoexfoliation Dear Editor: I read with interest the recent paper by Kang et al,1 in which they look at the geographic distribution of exfoliative glaucoma in the United States and found lower rates in those who had lived in the middle or southern regions of the country, which suggested an environmental or ecological effect. They do review a number of epidemiologic studies including that by Stein et al.2 However, they seem to have overlooked a study performed some years ago in Australian
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Ophthalmology Volume 119, Number 7, July 2012 Aboriginal people.3 The calculation of ocular exposure to radiation is relatively difficult and geographic location is at best only a poor surrogate.4 To ascertain ocular exposure, one needs to take into account the time spent outdoors, the surface and the use of eyewear, and hats in addition to geographic location. The study in Australian Aboriginal people avoided many of these problems, as there was little migration in this group whose lives are spent predominantly outside in sandy conditions, whether at work or not, and in whom hat use was infrequent and spectacle use almost unknown. Although this study was undertaken before it was possible to calculate multivariate adjusted rate ratios, its findings are still of relevance and highlighted the importance of sun exposure, and especially global radiation as a factor associated with pseudoexfoliation. Also noteworthy in the Aboriginal people is the rarity of glaucoma in those with pseudoexfoliation.5 HUGH R. TAYLOR, AC, MD Melbourne, Australia
LOUIS R. PASQUALE, MD JAE HEE KANG, SCD STEPHANIE LOOMIS, MPH JANEY L. WIGGS, MD, PHD Boston, Massachusetts JOSHUA D. STEIN, MD, MS Ann Arbor, Michigan References 1. Taylor HR, Hollows FC, Moran D. Pseudoexfoliation of the lens in Australian Aborigines. Br J Ophthalmol 1977;61: 473–5. 2. Stein JD, Pasquale LR, Talwar N, et al. Geographic and climatic factors associated with the exfoliation syndrome. Arch Ophthalmol 2011;129:1053– 60. 3. Kang JH, Wiggs JL, Stein JD, Pasquale LR. Demographic and geographic features of exfoliation glaucoma in 2 United States-based prospective cohorts. Ophthalmology 2012;119: 27–35.
References 1. Kang JH, Loomis S, Wiggs JL, Stein JD. Demographic and geographic features of exfoliation glaucoma in 2 United States-based prospective cohorts. Ophthalmology 2012;119: 27–35. 2. Stein JD, Pasquale LR, Talwar N, et al. Geographic and climatic factors associated with the exfoliation syndrome. Arch Ophthalmol 2011;129:1053– 60. 3. Taylor HR. Pseudoexfoliation, an environmental disease? Trans Ophthalmol Soc UK 1979;99:302–7. 4. Rosenthal FS, Phoon C, Bakalian AE, Taylor HR. The ocular dose of ultraviolet radiation to outdoor workers. Invest Ophthalmol Vis Sci 1988;29:649 –56. 5. Taylor HR, Hollows FC, Moran D. Pseudoexfoliation of the lens in Australian Aborigines. Br J Ophthalmol 1977;14: 473–5.
Author reply Dear Editor: We thank Dr. Taylor for his interest in our work. The role of genes and environment in relation to exfoliation syndrome (ES) has been long-debated. We are well aware of Dr. Taylor’s interesting work on ES in Australian Aboriginal people,1 which was one of the earliest studies supporting the possibility that environmental factors (particularly global irradiation) may play a role in ES. In fact, in our related work, where we assessed climatic factors in relation to ES and exfoliation glaucoma (EG),2 we reference Dr. Taylor’s work. Our current manuscript focuses on basic demographic attributes and residential history in relation to incident exfoliation glaucoma and exfoliation glaucoma suspect status in 2 cohorts of health professionals.3 Dr. Taylor’s work was not quoted, as a detailed climatic analysis was not performed. We agree with Dr. Taylor that ocular global irradiation exposure can be challenging to measure but assessing this parameter may yield more insight into the etiology of ES. In future manuscripts, we plan to investigate more climactic factors in relation to EG and compare our findings in light of Dr. Taylor’s work.
1500
Myopia and Glaucoma Dear Editor: Tae-Woo et al nicely showed1 that advances in imaging technology often lead to refined knowledge of the eye in health and disease, which at the same time calls for clearer terminology to accommodate the newly discovered facts.2,3 As they acknowledged, “myopia” is often erroneously confused with “elongated globe,” for to paraphrase Priestley Smith, “large eyes are not necessarily myopic and myopic eyes are not necessarily large.”4 This distinction is not simply nitpicking but leads to a deeper understanding of the etiological mechanisms involved. Refractive errors belong to the optical branch of physics, while the forces that determine the structure of the globe and its growth (such as pressure) are part of mechanics. Optical factors do not change the shape of the globe, including its optic nerve head and lamina cribrosa, whereas mechanical ones do change. It is a geometrical axiom that a sphere contains the largest volume under the smallest surface area. Therefore, any malleable surface, such as the sclera, will tend to assume a spherical form under any pressure within. In an aspherical elongated globe (Acrophthalmos) the geometrical center moves backwards, away from the stiff limbal ring and toward the posterior pole. The intraocular pressure here exerts a larger force laterally, tending to stretch the posterior structures. Since the choroid and retina (Fig 1, available at http://aaojournal.org) are anchored nasally at the optic nerve head they will be stretched away laterally, hence the “myopic” cup and crescents (“␣ and -zone parapapillary atrophy”).5 These geometrical and physical principles apply reasonably well to the forces acting on the lamina cribrosa, a locus minoris resistentiae, as shown in the 2 articles by Park et al,6,7 preceding the article cited above. HARRY H. MARK, MD North Haven, Connecticut
were excluded from analysis ranged from 12 to 39 months with a mean time of 20 months. Chaurasia et al1 bring up a very interesting question regarding the steroid regimen as a factor for increased risk of graft rejection. They note that in our group of patients with other ocular comorbidities that excluded them from the study analysis, there were 3 cases of rejection out of 7 eyes with prior glaucoma filtering surgery. We have subsequently reviewed these patients who were excluded due to prior glaucoma filtering surgery. We found that of these seven eyes, 4 of 7 (57.1%) were indeed placed on a lower dosage of steroid than our standard postoperative regimen (either loteprednol etabonate 0.5% or fluorometholone 0.1% as opposed to prednisolone acetate 1%) during the first postoperative year due to concerns about steroid-response elevations in intraocular pressure. However, of the 3 eyes in this group that subsequently developed a graft rejection episode, only one was on fluorometholone 0.1% at the time of their rejection episode. Thus, although the data set is too small to reach a statistically significant conclusion, in our patients with prior glaucoma filtering surgery it does not appear that a lower dosage of steroid led to an increased vulnerability to graft rejection. The issue of graft rejection in the context of endothelial keratoplasty, glaucoma filtering surgery, and the ideal steroid regimen is one that deserves more careful study. This is certainly not a new concern to keratoplasty surgery in general, but remains an important one for us to continue to address as we look toward improving the outcomes of our patients in the future. JENNIFER Y. LI, MD Sacramento, California MARK A. TERRY, MD Portland, Oregon JEFFREY GOSHE, MD Cleveland, Ohio
References 1. Li JY, Terry MA, Goshe J, et al. Graft rejection after Descemet’s stripping automated endothelial keratoplasty: graft survival and endothelial cell loss. Ophthalmology 2012;119: 90 – 4. 2. Allan B, Terry MA, Price FW, et al. Corneal transplant rejection rate and severity after endothelial keratoplasty. Cornea 2007;26:1039 – 42.
Author reply Dear Editor: We appreciate the interest that Chaurasia et al have expressed with regard to our article entitled, “Graft rejection after Descemet’s stripping automated endothelial keratoplasty.”1 We hope that we may clarify some aspects of the article in response to the questions they have raised. Regarding the discrepancy in the total number of graft rejections in subjects excluded from the study, this is a typographical error. There were a total of 7 graft rejections in patients excluded from the study for ocular comorbidities. The time frame for these graft rejection episodes that
DAVID DAVIS-BOOZER, MPH Portland, Oregon Reference 1. Li JY, Terry MA, Goshe J, et al. Graft rejection after Descemet’s stripping automated endothelial keratoplasty: graft survival and endothelial cell loss. Ophthalmology 2012;119:90 – 4.
Pseudoexfoliation Dear Editor: I read with interest the recent paper by Kang et al,1 in which they look at the geographic distribution of exfoliative glaucoma in the United States and found lower rates in those who had lived in the middle or southern regions of the country, which suggested an environmental or ecological effect. They do review a number of epidemiologic studies including that by Stein et al.2 However, they seem to have overlooked a study performed some years ago in Australian
1499
Ophthalmology Volume 119, Number 7, July 2012 Aboriginal people.3 The calculation of ocular exposure to radiation is relatively difficult and geographic location is at best only a poor surrogate.4 To ascertain ocular exposure, one needs to take into account the time spent outdoors, the surface and the use of eyewear, and hats in addition to geographic location. The study in Australian Aboriginal people avoided many of these problems, as there was little migration in this group whose lives are spent predominantly outside in sandy conditions, whether at work or not, and in whom hat use was infrequent and spectacle use almost unknown. Although this study was undertaken before it was possible to calculate multivariate adjusted rate ratios, its findings are still of relevance and highlighted the importance of sun exposure, and especially global radiation as a factor associated with pseudoexfoliation. Also noteworthy in the Aboriginal people is the rarity of glaucoma in those with pseudoexfoliation.5 HUGH R. TAYLOR, AC, MD Melbourne, Australia
LOUIS R. PASQUALE, MD JAE HEE KANG, SCD STEPHANIE LOOMIS, MPH JANEY L. WIGGS, MD, PHD Boston, Massachusetts JOSHUA D. STEIN, MD, MS Ann Arbor, Michigan References 1. Taylor HR, Hollows FC, Moran D. Pseudoexfoliation of the lens in Australian Aborigines. Br J Ophthalmol 1977;61: 473–5. 2. Stein JD, Pasquale LR, Talwar N, et al. Geographic and climatic factors associated with the exfoliation syndrome. Arch Ophthalmol 2011;129:1053– 60. 3. Kang JH, Wiggs JL, Stein JD, Pasquale LR. Demographic and geographic features of exfoliation glaucoma in 2 United States-based prospective cohorts. Ophthalmology 2012;119: 27–35.
References 1. Kang JH, Loomis S, Wiggs JL, Stein JD. Demographic and geographic features of exfoliation glaucoma in 2 United States-based prospective cohorts. Ophthalmology 2012;119: 27–35. 2. Stein JD, Pasquale LR, Talwar N, et al. Geographic and climatic factors associated with the exfoliation syndrome. Arch Ophthalmol 2011;129:1053– 60. 3. Taylor HR. Pseudoexfoliation, an environmental disease? Trans Ophthalmol Soc UK 1979;99:302–7. 4. Rosenthal FS, Phoon C, Bakalian AE, Taylor HR. The ocular dose of ultraviolet radiation to outdoor workers. Invest Ophthalmol Vis Sci 1988;29:649 –56. 5. Taylor HR, Hollows FC, Moran D. Pseudoexfoliation of the lens in Australian Aborigines. Br J Ophthalmol 1977;14: 473–5.
Author reply Dear Editor: We thank Dr. Taylor for his interest in our work. The role of genes and environment in relation to exfoliation syndrome (ES) has been long-debated. We are well aware of Dr. Taylor’s interesting work on ES in Australian Aboriginal people,1 which was one of the earliest studies supporting the possibility that environmental factors (particularly global irradiation) may play a role in ES. In fact, in our related work, where we assessed climatic factors in relation to ES and exfoliation glaucoma (EG),2 we reference Dr. Taylor’s work. Our current manuscript focuses on basic demographic attributes and residential history in relation to incident exfoliation glaucoma and exfoliation glaucoma suspect status in 2 cohorts of health professionals.3 Dr. Taylor’s work was not quoted, as a detailed climatic analysis was not performed. We agree with Dr. Taylor that ocular global irradiation exposure can be challenging to measure but assessing this parameter may yield more insight into the etiology of ES. In future manuscripts, we plan to investigate more climactic factors in relation to EG and compare our findings in light of Dr. Taylor’s work.
1500
Myopia and Glaucoma Dear Editor: Tae-Woo et al nicely showed1 that advances in imaging technology often lead to refined knowledge of the eye in health and disease, which at the same time calls for clearer terminology to accommodate the newly discovered facts.2,3 As they acknowledged, “myopia” is often erroneously confused with “elongated globe,” for to paraphrase Priestley Smith, “large eyes are not necessarily myopic and myopic eyes are not necessarily large.”4 This distinction is not simply nitpicking but leads to a deeper understanding of the etiological mechanisms involved. Refractive errors belong to the optical branch of physics, while the forces that determine the structure of the globe and its growth (such as pressure) are part of mechanics. Optical factors do not change the shape of the globe, including its optic nerve head and lamina cribrosa, whereas mechanical ones do change. It is a geometrical axiom that a sphere contains the largest volume under the smallest surface area. Therefore, any malleable surface, such as the sclera, will tend to assume a spherical form under any pressure within. In an aspherical elongated globe (Acrophthalmos) the geometrical center moves backwards, away from the stiff limbal ring and toward the posterior pole. The intraocular pressure here exerts a larger force laterally, tending to stretch the posterior structures. Since the choroid and retina (Fig 1, available at http://aaojournal.org) are anchored nasally at the optic nerve head they will be stretched away laterally, hence the “myopic” cup and crescents (“␣ and -zone parapapillary atrophy”).5 These geometrical and physical principles apply reasonably well to the forces acting on the lamina cribrosa, a locus minoris resistentiae, as shown in the 2 articles by Park et al,6,7 preceding the article cited above. HARRY H. MARK, MD North Haven, Connecticut