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Safety and effectiveness of topical bimatoprost
CORRESPONDENCE Safety and effectiveness of topical bimatoprost (Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes.Vol. 43[5])
Dear Editor,
reasonably confident (95%) that the true rate of this event in the population is no more than 3 in n (3/n).”2 By this estimation, with the “rule of three” and entering the 18 eyes of 18 patients, it is possible that a CME rate of up to 17% could have been missed with this small sample size.
n the October 2008 issue of the Canadian Journal of Ophthalmology, Yeom et al.1 conclude that topical application of bimatoprost does not induce clinical or structural changes in the macula. They also conclude that bimatoprost effectively lowers intraocular pressure without causing macular disorders such as cystoid macular edema (CME). While it is quite possible that this is indeed the case, I believe that the data do not support this conclusion. The study recruited 40 eyes of 22 patients, but only 33 eyes of 18 patients completed the study. Including both eligible eyes of each patient is inappropriate due to the high level of between eye–within patient correlation. More importantly, a power calculation is not included. The “rule of three” states that “if none of n patients has the adverse event in question, then we can be
REFERENCES
Safety and effectiveness of topical bimatoprost— Author reply (Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Vol. 43[5])
Bimatoprost, a prostamide F2α-like drug, acts as a prostanoid FP receptor agonist and (or) an ester prodrug equivalent. Although it appears to mimic the activity of the prostaglandin analogues, strictly speaking, it is a unique ocular hypotensive agent.6 Therefore, it is important to study the safety and effectiveness of bimatoprost itself. Considering these aspects, we believe our study provides clinicians with a good rationale to use topical bimatoprost safely and effectively in their clinics.
I
Dear Editor,
W
e thank Mikelberg1 for his interest in our article.2 He argues that our case series sample size was too small to effectively validate the safe application of topical bimatoprost 0.03%. Although the “rule of three” mentioned by Mikelberg is a useful tool, it is not a definite method to validate safety and effectiveness. However, we do agree with his basic assertion. The clinically significant maculopathy related to prostaglandin analogues occurs infrequently even in high-risk pseudophakic or aphakic eyes.3,4 Because we evaluated only 33 eyes of 18 glaucoma patients with normal phakic eyes, it is possible that we did not encounter an uncommon maculopathy (such as cystoid macular edema [CME]). In this respect, our article can be viewed as a preliminary report rather than a confirmation study. Nevertheless, our study presents several important findings that we wish to highlight. First, to judge whether or not the macula was changed by bimatoprost, we used optical coherence tomography (OCT) followed by angiography. Because CME, for example, causes fluid to accumulate in the outer plexiform layer, increasing the volume of the retina and progressively creating cystic spaces, it would be easily detected with OCT.5 Second, we evaluated not only the macular thickness of 9 scanned sectors but also the total macular volume. In the literature, we could not find any other article dealing with the influence of bimatoprost on macular volume.
1. Yeom HY, Hong S, Kim SS, Kim CY, Seong GJ. Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Can J Ophthalmol 2008;43:563–6. 2. Shachat AP, Chambers WA, Liesegang TJ, Albert DA. Safe and effective. Ophthalmology 2003;110:2073–4.
Frederick S. Mikelberg University of British Columbia, Vancouver, B.C. Correspondence to Frederick S. Mikelberg, MD: [email protected] Can J Ophthalmol 2009;44:209 doi:10.3129/i09-046
REFERENCES 1. Mikelberg FS. Safety and effectiveness of topical bimatoprost. Can J Ophthalmol 2009;44:209. 2. Yeom HY, Hong S, Kim SS, Kim CY, Seong GJ. Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Can J Ophthalmol 2008;43:563–6. 3. Ayyala RS, Cruz DA, Margo CE, et al. Cystoid macular edema associated with latanoprost in aphakic and pseudophakic eyes. Am J Ophthalmol 1998;126:602–4. 4. Wand M, Gaudio AR, Shields MB. Latanoprost and cystoid macular edema in high-risk aphakic or pseudophakic eyes. J Cataract Refract Surg 2001;27:1397–401. 5. Guex-Crosier Y. The pathogenesis and clinical presentation of macular edema in inflammatory diseases. Doc Ophthalmol 1999;97:297–309. 6. Krauss AH, Woodward DF. Update on the mechanism of action of bimatoprost: a review and discussion of new evidence. Surv Ophthalmol 2004;49:S5–11.
Samin Hong,* Yeom Ho Yeop,† Gong Je Seong* *Yonsei University College of Medicine, and † Siloam Eye Hospital, Seoul, Korea Correspondence to Gong Je Seong, MD: [email protected] Can J Ophthalmol 2009;44:209 doi:10.3129/i09-047 CAN J OPHTHALMOL—VOL. 44, NO. 2, 2009
209
Dear Editor,
reasonably confident (95%) that the true rate of this event in the population is no more than 3 in n (3/n).”2 By this estimation, with the “rule of three” and entering the 18 eyes of 18 patients, it is possible that a CME rate of up to 17% could have been missed with this small sample size.
n the October 2008 issue of the Canadian Journal of Ophthalmology, Yeom et al.1 conclude that topical application of bimatoprost does not induce clinical or structural changes in the macula. They also conclude that bimatoprost effectively lowers intraocular pressure without causing macular disorders such as cystoid macular edema (CME). While it is quite possible that this is indeed the case, I believe that the data do not support this conclusion. The study recruited 40 eyes of 22 patients, but only 33 eyes of 18 patients completed the study. Including both eligible eyes of each patient is inappropriate due to the high level of between eye–within patient correlation. More importantly, a power calculation is not included. The “rule of three” states that “if none of n patients has the adverse event in question, then we can be
REFERENCES
Safety and effectiveness of topical bimatoprost— Author reply (Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Vol. 43[5])
Bimatoprost, a prostamide F2α-like drug, acts as a prostanoid FP receptor agonist and (or) an ester prodrug equivalent. Although it appears to mimic the activity of the prostaglandin analogues, strictly speaking, it is a unique ocular hypotensive agent.6 Therefore, it is important to study the safety and effectiveness of bimatoprost itself. Considering these aspects, we believe our study provides clinicians with a good rationale to use topical bimatoprost safely and effectively in their clinics.
I
Dear Editor,
W
e thank Mikelberg1 for his interest in our article.2 He argues that our case series sample size was too small to effectively validate the safe application of topical bimatoprost 0.03%. Although the “rule of three” mentioned by Mikelberg is a useful tool, it is not a definite method to validate safety and effectiveness. However, we do agree with his basic assertion. The clinically significant maculopathy related to prostaglandin analogues occurs infrequently even in high-risk pseudophakic or aphakic eyes.3,4 Because we evaluated only 33 eyes of 18 glaucoma patients with normal phakic eyes, it is possible that we did not encounter an uncommon maculopathy (such as cystoid macular edema [CME]). In this respect, our article can be viewed as a preliminary report rather than a confirmation study. Nevertheless, our study presents several important findings that we wish to highlight. First, to judge whether or not the macula was changed by bimatoprost, we used optical coherence tomography (OCT) followed by angiography. Because CME, for example, causes fluid to accumulate in the outer plexiform layer, increasing the volume of the retina and progressively creating cystic spaces, it would be easily detected with OCT.5 Second, we evaluated not only the macular thickness of 9 scanned sectors but also the total macular volume. In the literature, we could not find any other article dealing with the influence of bimatoprost on macular volume.
1. Yeom HY, Hong S, Kim SS, Kim CY, Seong GJ. Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Can J Ophthalmol 2008;43:563–6. 2. Shachat AP, Chambers WA, Liesegang TJ, Albert DA. Safe and effective. Ophthalmology 2003;110:2073–4.
Frederick S. Mikelberg University of British Columbia, Vancouver, B.C. Correspondence to Frederick S. Mikelberg, MD: [email protected] Can J Ophthalmol 2009;44:209 doi:10.3129/i09-046
REFERENCES 1. Mikelberg FS. Safety and effectiveness of topical bimatoprost. Can J Ophthalmol 2009;44:209. 2. Yeom HY, Hong S, Kim SS, Kim CY, Seong GJ. Influence of topical bimatoprost on macular thickness and volume in glaucoma patients with phakic eyes. Can J Ophthalmol 2008;43:563–6. 3. Ayyala RS, Cruz DA, Margo CE, et al. Cystoid macular edema associated with latanoprost in aphakic and pseudophakic eyes. Am J Ophthalmol 1998;126:602–4. 4. Wand M, Gaudio AR, Shields MB. Latanoprost and cystoid macular edema in high-risk aphakic or pseudophakic eyes. J Cataract Refract Surg 2001;27:1397–401. 5. Guex-Crosier Y. The pathogenesis and clinical presentation of macular edema in inflammatory diseases. Doc Ophthalmol 1999;97:297–309. 6. Krauss AH, Woodward DF. Update on the mechanism of action of bimatoprost: a review and discussion of new evidence. Surv Ophthalmol 2004;49:S5–11.
Samin Hong,* Yeom Ho Yeop,† Gong Je Seong* *Yonsei University College of Medicine, and † Siloam Eye Hospital, Seoul, Korea Correspondence to Gong Je Seong, MD: [email protected] Can J Ophthalmol 2009;44:209 doi:10.3129/i09-047 CAN J OPHTHALMOL—VOL. 44, NO. 2, 2009
209