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Outpatient postoperative fluid-gas exchange after early failed vitrectomy surgery
Letters to the Editor
Regression after Photorefractive Keratectomy for Myopia Dear Editor: The finding of Haviv et al (Ophthalmology 1997;104:1948 – 51) is very important for every refractive surgeon to know. In their discussion, the authors mention the fact that they had not performed biometry, and thus cannot be sure that myopia did not progress as it would have progressed without photorefractive keratectomy (PRK). It would have been interesting to know the keratometric values (manual or as measured with videokeratography) before PRK and during the follow-up period. If there had been a true regression, a steepening of the cornea should have been registered. ISAAK SCHIPPER, MD Los Angeles, California Reference 1. Haviv D, Hefetz L, Krakowsky D, et al. For how long can regression continue after photorefractive keratectomy for myopia? Ophthalmology 1997;104:1948 –50.
Author’s reply Dear Editor: Dr. Schipper is correct, and it would have been informative to measure the keratometric values during follow-up on our patients. We are confident, however, that regression did not change due to progression of myopia because we took only patients with stable myopia of at least 3 years whose regression was the same at different ages. Nevertheless, we now routinely measure keratometric values and axial length, and are preparing to publish a study that takes these data into consideration. DAVID HAVIV, MD Zerifin, Israel
Outpatient Postoperative Fluid–Gas Exchange after Early Failed Vitrectomy Surgery Dear Editor: We read with interest the article by Johnson et al1 on outpatient postoperative fluid– gas exchange after early failed vitrectomy surgery for macular hole. In their series of 23 consecutive eyes, 17 eyes (74%) had successful closure of macular hole with improvement of visual acuity of 2 or more lines after a simple outpatient fluid– gas exchange procedure. The results are encouraging and the gas–fluid exchange procedure is simple to perform, cost-effective, and convenient to patients. However, should this procedure be recommended to all patients who have failed vitrectomy surgery for macular hole? When we further analyze the authors’ data in terms of the age of the macular hole, it is found that the successful rate for macular hole of less than 12 months old (group a) was much higher than those with an age of 1 year or more (group b). Their rates of successful
closure with this simple procedure were 88.2% (15 of 17 eyes) and 50% (3 of 6 eyes) for groups a and b, respectively.1 The difference is statistically significant (chi-square test, P ⫽ 0.05). Hence it appears that selecting the lesschronic cases (group a) will yield a better result. Repeating pars plana vitrectomy may be a better choice for cases with higher risk of failure, such as those in group b. Otherwise, there may be unnecessary delay for the final definitive surgery, and prolongation of the uncomfortable face-down posturing. Thompson et al2 repeated pars plana vitrectomy in 17 chronic macular holes that failed to close after initial vitrectomy. They managed to close 14 holes (82.4%), despite the fact that the age of all macular holes was greater than 24 months old. This much higher closure rate suggests that pars plana vitrectomy, rather than external fluid– gas exchange, may be a better alternative to treat chronic macular hole of 12 months or greater that failed the primary vitrectomy. Several factors may explain the different closure rates for the two methods (internal and external fluid– gas exchange) in the management of chronic macular hole after failed primary vitrectomy. Chronic macular holes tend to be larger, as macular holes usually enlarge with age until they reach a certain size. Macular holes of larger size may need a longer period of effective gas tamponade, which is more likely to be achieved through internal fluid– gas exchange during pars plana vitrectomy than during external fluid– gas exchange. Moreover, epiretinal membranes appear to be more common at the edge of chronic macular holes.3 These membranes may exert traction on the edges of macular holes and make the closure of larger chronic macular holes more difficult. These membranes can be removed only during the second pars plana vitrectomy, if they have not been removed initially. In conclusion, simple external fluid– gas exchange appears to be a good option in the management of macular hole of shorter duration that failed vitreous surgery. For more chronic ones, repeated pars plana vitrectomy may be a better alternative. ALVIN K.H. KWOK, FRCS DENNIS S.C. LAM, FRCS, FRCOPHTH LULU L. CHENG, MD Shatin, Hong Kong TARUN SHARMA, MD Madras, India References 1. Johnson RN, McDonald HR, Schatz H, Ai E. Outpatient postoperative fluid– gas exchange after early failed vitrectomy surgery for macular hole. Ophthalmology 1997;104:2009 –13. 2. Thompson JT, Sjaarda RN, Lansing MB. The results of vitreous surgery for chronic macular holes. Retina 1997;17:493– 501. 3. Guyer DR, Green WR, de Bustros S, Fine SL. Histopathologic features of idiopathic macular holes and cysts. Ophthalmology 1990;97:1045–51.
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Regression after Photorefractive Keratectomy for Myopia Dear Editor: The finding of Haviv et al (Ophthalmology 1997;104:1948 – 51) is very important for every refractive surgeon to know. In their discussion, the authors mention the fact that they had not performed biometry, and thus cannot be sure that myopia did not progress as it would have progressed without photorefractive keratectomy (PRK). It would have been interesting to know the keratometric values (manual or as measured with videokeratography) before PRK and during the follow-up period. If there had been a true regression, a steepening of the cornea should have been registered. ISAAK SCHIPPER, MD Los Angeles, California Reference 1. Haviv D, Hefetz L, Krakowsky D, et al. For how long can regression continue after photorefractive keratectomy for myopia? Ophthalmology 1997;104:1948 –50.
Author’s reply Dear Editor: Dr. Schipper is correct, and it would have been informative to measure the keratometric values during follow-up on our patients. We are confident, however, that regression did not change due to progression of myopia because we took only patients with stable myopia of at least 3 years whose regression was the same at different ages. Nevertheless, we now routinely measure keratometric values and axial length, and are preparing to publish a study that takes these data into consideration. DAVID HAVIV, MD Zerifin, Israel
Outpatient Postoperative Fluid–Gas Exchange after Early Failed Vitrectomy Surgery Dear Editor: We read with interest the article by Johnson et al1 on outpatient postoperative fluid– gas exchange after early failed vitrectomy surgery for macular hole. In their series of 23 consecutive eyes, 17 eyes (74%) had successful closure of macular hole with improvement of visual acuity of 2 or more lines after a simple outpatient fluid– gas exchange procedure. The results are encouraging and the gas–fluid exchange procedure is simple to perform, cost-effective, and convenient to patients. However, should this procedure be recommended to all patients who have failed vitrectomy surgery for macular hole? When we further analyze the authors’ data in terms of the age of the macular hole, it is found that the successful rate for macular hole of less than 12 months old (group a) was much higher than those with an age of 1 year or more (group b). Their rates of successful
closure with this simple procedure were 88.2% (15 of 17 eyes) and 50% (3 of 6 eyes) for groups a and b, respectively.1 The difference is statistically significant (chi-square test, P ⫽ 0.05). Hence it appears that selecting the lesschronic cases (group a) will yield a better result. Repeating pars plana vitrectomy may be a better choice for cases with higher risk of failure, such as those in group b. Otherwise, there may be unnecessary delay for the final definitive surgery, and prolongation of the uncomfortable face-down posturing. Thompson et al2 repeated pars plana vitrectomy in 17 chronic macular holes that failed to close after initial vitrectomy. They managed to close 14 holes (82.4%), despite the fact that the age of all macular holes was greater than 24 months old. This much higher closure rate suggests that pars plana vitrectomy, rather than external fluid– gas exchange, may be a better alternative to treat chronic macular hole of 12 months or greater that failed the primary vitrectomy. Several factors may explain the different closure rates for the two methods (internal and external fluid– gas exchange) in the management of chronic macular hole after failed primary vitrectomy. Chronic macular holes tend to be larger, as macular holes usually enlarge with age until they reach a certain size. Macular holes of larger size may need a longer period of effective gas tamponade, which is more likely to be achieved through internal fluid– gas exchange during pars plana vitrectomy than during external fluid– gas exchange. Moreover, epiretinal membranes appear to be more common at the edge of chronic macular holes.3 These membranes may exert traction on the edges of macular holes and make the closure of larger chronic macular holes more difficult. These membranes can be removed only during the second pars plana vitrectomy, if they have not been removed initially. In conclusion, simple external fluid– gas exchange appears to be a good option in the management of macular hole of shorter duration that failed vitreous surgery. For more chronic ones, repeated pars plana vitrectomy may be a better alternative. ALVIN K.H. KWOK, FRCS DENNIS S.C. LAM, FRCS, FRCOPHTH LULU L. CHENG, MD Shatin, Hong Kong TARUN SHARMA, MD Madras, India References 1. Johnson RN, McDonald HR, Schatz H, Ai E. Outpatient postoperative fluid– gas exchange after early failed vitrectomy surgery for macular hole. Ophthalmology 1997;104:2009 –13. 2. Thompson JT, Sjaarda RN, Lansing MB. The results of vitreous surgery for chronic macular holes. Retina 1997;17:493– 501. 3. Guyer DR, Green WR, de Bustros S, Fine SL. Histopathologic features of idiopathic macular holes and cysts. Ophthalmology 1990;97:1045–51.
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