- Email: [email protected]
Author reply
Correspondence References 1. Thompson JT. Three kinds of lies. Ophthalmology 2014;121: 1315–6. 2. Etminan M, Foroghian F, Brophy JM, et al. Oral fluoroquinolone and the risk of retinal detachment. JAMA 2012;307: 1414–9. 3. Pasternak B, Svanstrom H, Melbye M, Hviid A. Association between oral fluoroquinolone use and retinal detachment. JAMA 2013;310:2184–90. 4. Kapoor KG, Hodge DO, St. Sauver JL, Barkmeier AJ. Oral fluoroquinolones and the incidence of rhegmatogenous retinal detachment and symptomatic retinal breaks: a population-based study. Ophthalmology 2014;121:1269–73.
Re: Srikumaran et al.: Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort
one study, but not in another.3 Thus, as in the retention analysis, if analysis of the complications as per primary indications would have been done, it could provide better insight over the long-term followup about specific group of ocular conditions predisposing to specific complications. The rate of posterior segment complications of retinal detachment and endophthalmitis steadily increased, even though the number of patients with follow-up declined. Patients with retroprosthetic membrane needed yttrium aluminum garnet (YAG) or surgical membranectomy, which has been shown to increase subsequent retinal detachment.4 These sight-threatening complications create challenges in the detection, management, and follow-up of patients, even for experienced retina surgeons. As retention rates of keratoprosthesis increase, these complications increase. The authors advocate simultaneous or prior glaucoma surgery for high-risk patients. However, it may be more prudent to calculate the number needed to treat to prevent glaucoma progression before this recommendation. Options like complete iridectomy may also be considered.5
(Ophthalmology 2014;121:2159-64) Dear Editor: We read with interest the article by Srikumaran et al1 regarding Boston type I keratoprosthesis implantation. The authors report an increasing risk of complications over time, but a significant proportion of patients retain the device and achieve useful vision. Mean visual acuity in logarithm of the minimum angle of resolution would have been a better outcome measure and the change in mean visual acuity could have been studied better. Interval visual acuity gives valuable insight into trend over time.2 There is a typographical error in Figure 1. Although the text mentions that 97 of 138 (70%) achieved best ever vision of 20/ 200 postoperatively, the figures show erroneous values of 60% and 70%. In the Kaplan-Meier survival curve, it is worth mentioning the number at risk at each follow-up interval and the number and distribution of the censored subjects. The retention rate is estimated to be 67% at 7 years follow-up. However, only 15 patients were followed through 7 years; thus, the censored data at each step give a better interpretation of the data. It may be better to look at the survival rate of around 70% at 4 years when more than one half of the patients had follow-up. In the subgroup analysis, in the infectious causes group, survival tends to stabilize at 40 months after a sharp fall in the survival after 36 months. The fall in survival could be because of a small sample size, as evidenced by the large steps, or because of actual tendency of failures to occur at 3 years. The authors state that survival of keratoprosthesis implanted primarily is comparable to that after 1 prior failed keratoplasties. Specific indications where primary keratoprosthesis will be preferred compared with keratoplasty should be defined. For the other indications, prior failed grafts do not affect the retention of the keratoprosthesis significantly and thus keratoplasty should be used to ‘buy time’ before taking the patient for keratoprosthesis. Among the complications, the rate of infectious keratitis and sterile necrosis tended to stabilize after 2 and 5 years, respectively. This could be because of fewer numbers in each group or due to changed antibiotic prophylaxis and practice patterns over the years, leading to decreased complications. Ocular cicatrizing disorders has been mentioned as a risk factor for microbial keratitis in
SHRADDHA PAWAN SUREKA, MBBS, MS ROHIT R. MODI, MBBS, MS SRIKANT K. SAHU, MBBS, MS LV Prasad Eye Institute, Patia, Bhubaneswar, Odisha, India Financial Disclosure(s): The authors have no proprietary or commercial interests in any materials discussed in this Letter. Correspondence: Shraddha Pawan Sureka, MBBS, MS, L V Prasad Eye Institute, Bhubaneswar, Odisha, India 751024. E-mail: [email protected].
References 1. Srikumaran D, Munoz B, Aldave AJ, et al. Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort. Ophthalmology 2014;121:2159–64. 2. Aldave AJ, Sangwan VS, Basu S, et al. International results with the Boston type I keratoprosthesis. Ophthalmology 2012;119: 1530–8. 3. Kim MJ, Yu F, Aldave AJ. Microbial keratitis after Boston type I keratoprosthesis implantation: incidence, organisms, risk factors, and outcomes. Ophthalmology 2013;120:2209–16. 4. Goldman DR, Hubschman J-P, Aldave AJ, et al. Postoperative posterior segment complications in eyes treated with the Boston type I keratoprosthesis. Retina 2013;33:532–41. 5. Basu S, Sureka S, Shukla R, Sangwan V. Boston type 1 based keratoprosthesis (Auro Kpro) and its modification (LVP Kpro) in chronic Stevens Johnson syndrome. BMJ Case Rep 2014. http://www.ncbi.nlm.nih.gov/pubmed/24663249. Accessed March 24, 2014.
Author reply Dear Editor: We thank the authors for their comments on our study.1 The numbers in the manuscript and in Figures 1 and 2 are correct. In the manuscript text, we reference the number of patients who achieved 20/200 or better vision. Whereas in the figures, we further subdivided the groups to better than 20/200 and included a separate bar for patients with 20/200 to 20/400 visual acuity.
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Ophthalmology Volume 122, Number 5, May 2015 Table 1. Follow-up Time of 139 Participants Included in the Survival Analyses Time (mo) 6 12 24 36 48 60 72 78
Cumulative Lost to Follow-up (Frequency) 6 18 35 54 68 89 114 120
Cumulative Lost to No. Remaining Follow-up (Percent) in the Cohort 4.3 12.9 25.2 38.8 48.9 64.2 82.0 86.3
133 121 104 85 71 50 25 19
We apologize for any confusion, but felt that this better showed the distribution of visual acuity in the cohort. We have included herein a depiction of the number of patients at risk at each time interval as requested (Table 1). We agree that the number of eyes remaining in the cohort beyond 5 years is small and that the survival curves may not be reliable. However, we are encouraged to note that a subset of eyes did very well for 7 years. Although we realize the inherent weakness of our retrospective study, we hope that future prospective studies will aim to identify preoperative patient characteristics or postoperative management
e32
regimens that result in better outcomes. In addition, comparison of keratoprosthesis with conventional repeat keratoplasty and the indications for primary keratoprosthesis need to be assessed in large prospective cohorts to better utilize this device.
DIVYA SRIKUMARAN, MD BEATRIZ MUNOZ, MS ESEN KARAMURSEL AKPEK, MD The Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, Maryland Financial Disclosure(s): The authors have no proprietary or commercial interests in any materials discussed in this Reply. Correspondence: Esen K. Akpek, MD, The Wilmer Eye Institute at Johns Hopkins, 600 N. Wolfe Street, Woods 370, Baltimore, MD 21287-2816. E-mail: [email protected].
Reference 1. Srikumaran D, Munoz B, Aldave AJ, et al. Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort. Ophthalmology 2014;121:2159–64.
Re: Srikumaran et al.: Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort
one study, but not in another.3 Thus, as in the retention analysis, if analysis of the complications as per primary indications would have been done, it could provide better insight over the long-term followup about specific group of ocular conditions predisposing to specific complications. The rate of posterior segment complications of retinal detachment and endophthalmitis steadily increased, even though the number of patients with follow-up declined. Patients with retroprosthetic membrane needed yttrium aluminum garnet (YAG) or surgical membranectomy, which has been shown to increase subsequent retinal detachment.4 These sight-threatening complications create challenges in the detection, management, and follow-up of patients, even for experienced retina surgeons. As retention rates of keratoprosthesis increase, these complications increase. The authors advocate simultaneous or prior glaucoma surgery for high-risk patients. However, it may be more prudent to calculate the number needed to treat to prevent glaucoma progression before this recommendation. Options like complete iridectomy may also be considered.5
(Ophthalmology 2014;121:2159-64) Dear Editor: We read with interest the article by Srikumaran et al1 regarding Boston type I keratoprosthesis implantation. The authors report an increasing risk of complications over time, but a significant proportion of patients retain the device and achieve useful vision. Mean visual acuity in logarithm of the minimum angle of resolution would have been a better outcome measure and the change in mean visual acuity could have been studied better. Interval visual acuity gives valuable insight into trend over time.2 There is a typographical error in Figure 1. Although the text mentions that 97 of 138 (70%) achieved best ever vision of 20/ 200 postoperatively, the figures show erroneous values of 60% and 70%. In the Kaplan-Meier survival curve, it is worth mentioning the number at risk at each follow-up interval and the number and distribution of the censored subjects. The retention rate is estimated to be 67% at 7 years follow-up. However, only 15 patients were followed through 7 years; thus, the censored data at each step give a better interpretation of the data. It may be better to look at the survival rate of around 70% at 4 years when more than one half of the patients had follow-up. In the subgroup analysis, in the infectious causes group, survival tends to stabilize at 40 months after a sharp fall in the survival after 36 months. The fall in survival could be because of a small sample size, as evidenced by the large steps, or because of actual tendency of failures to occur at 3 years. The authors state that survival of keratoprosthesis implanted primarily is comparable to that after 1 prior failed keratoplasties. Specific indications where primary keratoprosthesis will be preferred compared with keratoplasty should be defined. For the other indications, prior failed grafts do not affect the retention of the keratoprosthesis significantly and thus keratoplasty should be used to ‘buy time’ before taking the patient for keratoprosthesis. Among the complications, the rate of infectious keratitis and sterile necrosis tended to stabilize after 2 and 5 years, respectively. This could be because of fewer numbers in each group or due to changed antibiotic prophylaxis and practice patterns over the years, leading to decreased complications. Ocular cicatrizing disorders has been mentioned as a risk factor for microbial keratitis in
SHRADDHA PAWAN SUREKA, MBBS, MS ROHIT R. MODI, MBBS, MS SRIKANT K. SAHU, MBBS, MS LV Prasad Eye Institute, Patia, Bhubaneswar, Odisha, India Financial Disclosure(s): The authors have no proprietary or commercial interests in any materials discussed in this Letter. Correspondence: Shraddha Pawan Sureka, MBBS, MS, L V Prasad Eye Institute, Bhubaneswar, Odisha, India 751024. E-mail: [email protected].
References 1. Srikumaran D, Munoz B, Aldave AJ, et al. Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort. Ophthalmology 2014;121:2159–64. 2. Aldave AJ, Sangwan VS, Basu S, et al. International results with the Boston type I keratoprosthesis. Ophthalmology 2012;119: 1530–8. 3. Kim MJ, Yu F, Aldave AJ. Microbial keratitis after Boston type I keratoprosthesis implantation: incidence, organisms, risk factors, and outcomes. Ophthalmology 2013;120:2209–16. 4. Goldman DR, Hubschman J-P, Aldave AJ, et al. Postoperative posterior segment complications in eyes treated with the Boston type I keratoprosthesis. Retina 2013;33:532–41. 5. Basu S, Sureka S, Shukla R, Sangwan V. Boston type 1 based keratoprosthesis (Auro Kpro) and its modification (LVP Kpro) in chronic Stevens Johnson syndrome. BMJ Case Rep 2014. http://www.ncbi.nlm.nih.gov/pubmed/24663249. Accessed March 24, 2014.
Author reply Dear Editor: We thank the authors for their comments on our study.1 The numbers in the manuscript and in Figures 1 and 2 are correct. In the manuscript text, we reference the number of patients who achieved 20/200 or better vision. Whereas in the figures, we further subdivided the groups to better than 20/200 and included a separate bar for patients with 20/200 to 20/400 visual acuity.
e31
Ophthalmology Volume 122, Number 5, May 2015 Table 1. Follow-up Time of 139 Participants Included in the Survival Analyses Time (mo) 6 12 24 36 48 60 72 78
Cumulative Lost to Follow-up (Frequency) 6 18 35 54 68 89 114 120
Cumulative Lost to No. Remaining Follow-up (Percent) in the Cohort 4.3 12.9 25.2 38.8 48.9 64.2 82.0 86.3
133 121 104 85 71 50 25 19
We apologize for any confusion, but felt that this better showed the distribution of visual acuity in the cohort. We have included herein a depiction of the number of patients at risk at each time interval as requested (Table 1). We agree that the number of eyes remaining in the cohort beyond 5 years is small and that the survival curves may not be reliable. However, we are encouraged to note that a subset of eyes did very well for 7 years. Although we realize the inherent weakness of our retrospective study, we hope that future prospective studies will aim to identify preoperative patient characteristics or postoperative management
e32
regimens that result in better outcomes. In addition, comparison of keratoprosthesis with conventional repeat keratoplasty and the indications for primary keratoprosthesis need to be assessed in large prospective cohorts to better utilize this device.
DIVYA SRIKUMARAN, MD BEATRIZ MUNOZ, MS ESEN KARAMURSEL AKPEK, MD The Wilmer Eye Institute, Johns Hopkins School of Medicine, Baltimore, Maryland Financial Disclosure(s): The authors have no proprietary or commercial interests in any materials discussed in this Reply. Correspondence: Esen K. Akpek, MD, The Wilmer Eye Institute at Johns Hopkins, 600 N. Wolfe Street, Woods 370, Baltimore, MD 21287-2816. E-mail: [email protected].
Reference 1. Srikumaran D, Munoz B, Aldave AJ, et al. Long-term outcomes of Boston type 1 keratoprosthesis implantation: a retrospective multicenter cohort. Ophthalmology 2014;121:2159–64.