B RIEF R EPORTS In Vivo Demonstration of the Anatomic Differences Between Classic and Occult Choroidal Neovascularization Using Optical Coherence Tomography Edward H. Hughes, MRCP, MRCOphth, Jaheed Khan, MRCOphth, Nishal Patel, MRCOphth, Shahram Kashani, MRCP, MRCOphth, and N. Victor Chong, FRCS, FRCOphth PURPOSE: To determine architectural differences between classic and occult choroidal neovascularization (CNV) in vivo. DESIGN: Prospective observational case series. METHODS: Twenty-two patients with acute CNV under- went fluorescein angiography and optical coherence to- mography (OCT), which were analyzed by separate blinded observers. RESULTS: In 87.5% of angiographically labeled “classic” CNV a discreet subretinal lesion corresponding to the neovascular complex could be seen above and separate to the retinal pigment epithelium on OCT. This was found in only 13.3% of “occult” CNV. CONCLUSION: With the latest commercially available OCT equipment it is now possible to confirm in vivo the previously proposed anatomic differences between fluorescein angiographically labeled classic and occult CNV. Classic CNV appear to grow predominantly in the subretinal space, whereas the majority of occult lesions do not. Optical coherence tomography features of CNV may correlate with response to photodynamic therapy or angiostatic treatments, as well as predicting the success of surgical removal. (Am J Ophthalmol 2005;139:344 –346. © 2005 by Elsevier Inc. All rights reserved.) S UBFOVEAL CHOROIDAL NEOVASCULARIZATION (CNV) is a major cause of visual loss in age-related macular degeneration (AMD). It was believed that CNV in AMD grows beneath the retinal pigment epithelium (type I membrane) in contrast with younger patients with myopia or uveitis, in whom neovascular complexes were situated above the retinal pigment epithelium in the subretinal space (type II membranes), thus being amenable to surgical excision. 1 More recently, evidence from histopathologic studies of surgically excised CNV has suggested that some CNV in AMD patients reside above the retinal pigment epithelium. 2 In particular, it has been proposed that fluorescein angiographic differences may correlate with anatomic location: “classic” CNV predominantly occupy- ing the subretinal space and “occult” lesions remaining beneath the retinal pigment epithelium. 3 However, be- cause of the difficulty of obtaining postmortem eyes with fresh exudative AMD, there remains inadequate informa- tion about the in situ histologic features of CNV to confirm these proposed differences. We have used the most recent commercially available OCT system (OCT 3000, Carl Zeiss Ophthalmic Systems Inc) to study architectural differences between classic and occult CNV, and in this pilot study have demonstrated that the resolution of this technology is now able to identify a neovascular complex within the subretinal space, confirming the dogma that classic CNV predomi- nantly lie above the retinal pigment epithelium unlike occult lesions. Twenty-two consecutive patients with 23 new-onset submacular choroidal neovascular lesions underwent fluo- rescein angiography (FA) and OCT imaging (OCT 3000). The appearance of the lesions with these two modalities was analyzed by separate blinded observers (FA by N.V.C., OCT by S.K.). According to FA, CNV were labeled classic or occult based on the TAP protocol. 4 Optical coherence tomography images were acquired using both fast macular and macular thickness protocols, and were examined for the presence of a discreet subretinal lesion indicating a CNV membrane. Statistical analysis was performed using  2 test with Yate’s continuity correction. According to FA, 15 CNV were pure occult and eight were classic with no occult. One patient was 28 years old and was a highly myopic individual with a classic CNV; the rest were over 60 years old and diagnosed with AMD. Optical coherence tomography identified a well-defined, discreet subretinal opacity, separate from the retinal pig- Accepted for publication July 29, 2004. From the Retinal Research Unit, King’s College Hospital, Denmark Hill, London SE5 9RS, England. Inquiries to Victor Chong, Retinal Research Unit, King’s College Hospital, Denmark Hill, London SE5 9RS, England; fax: +44 207 3463738; e-mail: victor@eretina.org © 2005 BY ELSEVIER INC.ALL RIGHTS RESERVED. 344 0002-9394/05/$30.00