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Seonghwan Kim, Yung Ju Yoo, Se Joon Woo, Hee Kyung YangDepartment of Ophthalmology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, KoreaE-mail (Hee Kyung Yang): eye@snubh.org

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

References

1. Ashworth JL, Biswas S, Wraith E, Lloyd IC. Mucopolysac-charidoses and the eye. Surv Ophthalmol 2006;51:1-17.

2. McDonnell JM, Green WR, Maumenee IH. Ocular histo-pathology of systemic mucopolysaccharidosis, type II-A (Hunter syndrome, severe). Ophthalmology 1985;92:1772-9.

3. Yoon MK, Chen RW, Hedges TR 3rd, et al. High-speed, ul-trahigh resolution optical coherence tomography of the ret-ina in Hunter syndrome. Ophthalmic Surg Lasers Imaging 2007;38:423-8.

4. Chen TC, Cense B, Pierce MC, et al. Spectral domain opti-cal coherence tomography: ultra-high speed, ultra-high resolution ophthalmic imaging. Arch Ophthalmol 2005; 123:1715-20.

5. Bunt-Milam AH, Saari JC, Klock IB, Garwin GG. Zonulae adherentes pore size in the external limiting membrane of the rabbit retina. Invest Ophthalmol Vis Sci 1985;26:1377-80.

Macular Edema after Gabapentin

Dear Editor,Gabapentin is an anticonvulsant and has been used to

manage neuropathic pain. It was originally developed as an antiepileptic agent; however, it is now recommended as a drug of choice for the treatment of neuropathic pain. There is strong evidence that gabapentin is also effective in diabetic neuropathy and postherpetic neuralgia [1].

To the best of our knowledge, macular edema after use of gabapentin has not been reported to date. Therefore, we report a case of macular edema after gabapentin.

A 71-year-old man presented with a 1 day history of vi-sual disturbance and metamorphosis in both eyes. The pa-tient had taken oral gabapentin (Neurontin; Pfizer, New York, NY, USA) and oral methylprednisolone (Methylon; Alvogen, Seoul, Korea) for 8 days for treatment of posth-erpetic neuralgia. He had no other significant medical his-tory, except hypertension controlled by oral medication. Best-corrected visual acuity (Snellen) was 0.4 (right eye) and 0.2 (left eye), and the intraocular pressure was 9

mmHg (right eye), 11 mmHg (left eye), as determined by non-contact tonometry. Both eyes had moderate cataract. Ophthalmic examination of the anterior segments revealed no other abnormal findings. Dilated fundus examination and spectral domain optical coherence tomography re-vealed macular edema and serous retinal detachment of macula in both eyes (Fig. 1A-1D). Fluorescence angiogra-phy revealed f luorescein dye pooling on the macula and multiple leakages in both eyes (Fig. 1E and 1F). The patient was advised to discontinue gabapentin, and the use of the drug was stopped.

Four weeks after the initial visit, best corrected visual acuity improved to 0.9 (both eye). Fundus exam and spec-tral domain optical coherence tomography revealed mark-edly improved macular edema and serous detachment in both eyes (Fig. 1G-1J).

Gabapentin is an amino acid initially designed as a cyclic gamma-aminobutyric acid analogue with action as a gamma-aminobutyric acid agonist [2]. It also acts on different brain receptors by an as-yet unknown mecha-nism.

Common adverse effects of gabapentin include dizzi-ness, fatigue, drowsiness, sexual dysfunction, weight gain, and peripheral edema [3]. Uncommonly, gabapentin causes blurred vision and diplopia [4]. Steinhoff et al. [5] reported

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that this drug has been linked with abnormal color per-ception and reduced contrast sensitivity due to an un-known mechanism. Gabapentin could also cause abnor-mal f inding of visual evoked potentials and pattern electroretinogram [2]. It was suggested that toxic ef-fects on the neuro-transmitter function of the optic nerve might be responsible.

Macular edema on optical coherence tomography after gabapentin has not hitherto been described. Using fluores-cence angiography, the present patient was observed to suffer multiple chorioretinitis. Thus, it is possible that the macular edema was due to chorioretinitis. Herpetic infec-

tion can also induce chorioretinitis. However, the macular edema in the presented case was spontaneously improved after cessation of gabapentin and steroid, suggesting that chorioretinitis is not a sufficient explanation. Because the precise action mechanism of gabapentin is not known, it is difficult to deduce the mechanism of macular edema after the use of gabapentin. Further studies about the mecha-nism and frequency of macular edema after gabapentin are required.

In summary, we report macular edema occurring in a male patient receiving gabapentin therapy for postherpetic neuralgia treatment. The macular edema improved after

Fig. 1. At the initial visit, macular edema and serous detachment on both eyes were observed by fundus photo (A, right eye [OD]; B, left eye [OS]) and spectral domain optical coherence tomography (C, OD; D, OS). On fluorescence angiography, fluorescein dye pooling on the macula and multiple leakages were observed in both eyes (E, OD; F, OS). At 4 weeks after the initial visit, macular edema and serous detachment were much improved on fundus photo (G, OD; H, OS) and spectral domain optical coherence tomography (I, OD; J, OS).

A

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discontinuing the use of the drug. If vision loss after the use of gabapentin occurs, it is prudent to identify macular edema. Gabapentin should be considered one of the poten-tial causes of macular edema.

Ju Young Kim, Don Gyung Kim Retina Center, Nune Eye Hospital, Seoul, Korea

Soo Han KimDepartment of Ophthalmology, Wonju Severance Christian Hospital, Yonsei University Wonju College of Medicine, Wonju, Korea

Oh Woong Kwon, Soon Hyun Kim, Yong Sung YouRetina Center, Nune Eye Hospital, Seoul, KoreaE-mail (Yong Sung You): yongsung.you@gmail.com

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

References

1. Attal N, Cruccu G, Baron R, et al. EFNS guidelines on the pharmacological treatment of neuropathic pain: 2010 revi-sion. Eur J Neurol 2010;17:1113-e88.

2. Hilton EJ, Hosking SL, Betts T. The effect of antiepileptic drugs on visual performance. Seizure 2004;13:113-28.

3. Parke-Davis MP. Product information: Neurontin (gabapentin). New York: Pfizer; 2009.

4. Herranz JL, Sol JM, Hernandez G. Gabapentin used in 559 patients with partial seizures: a multicenter observation study. Spanish Gabapentin Work Group. Rev Neurol 2000; 30:1141-5.

5. Steinhoff BJ, Freudenthaler N, Paulus W. The influence of established and new antiepileptic drugs on visual percep-tion. 1. A placebo-controlled, double-blind, single-dose study in healthy volunteers. Epilepsy Res 1997;29:35-47.