En face OCT provides more detail on macular lesions
The in-depth exam of various retinal layers can expedite follow-up and treatment.
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OCT is the preferred imaging modality for diseases of the macula as it is noninvasive, easy to perform and provides high-resolution images. The most commonly used macula scans are macula cube and five-line raster, which both provide cross-sectional, longitudinal scans.
Recently, the en face OCT has been identified as an additional useful tool for analyzing and quantifying pathological findings. It provides transverse images at a specific depth of the retina. The software application takes dense raster scans and reconstructs a C-scan image on the coronal plane; it localizes lesions with specific subretinal layers.
The historical findings in the following case report will demonstrate the capacity of the Cirrus OCT (Carl Zeiss Meditec), specifically the en face feature, in diagnosing and monitoring macular and paramacular lesions. The accompanying OCT studies point at the salient details in the outer and subretinal layers; they flag the changes occurring over time and alert the practitioner as to the frequency of follow-up visits and to the adequate and timely referral to a retina specialist.
Case report
A 75-year-old Caucasian man presented with complaints of decreased vision in the left eye over the past month. His medical history included hypertension, benign prostatic hypertrophy and a history of basal cell carcinoma of the face (status-post removal). Ocular history was significant for bilateral pinpoint macular drusen, first noted 10 years prior, and early cataracts.
Best corrected visual acuity was 20/20 OD and 20/30 OS. Evaluation of the macula revealed an increase in pinpoint drusen along with a small focal area of geographic atrophy inferior to the macula in the right eye and left eye. Amsler grid testing was negative in both eyes. OCT macula cube 512 × 128 was performed in the right eye, and the en face feature was used to obtain an additional image at that time. Macula cube and en face images were also obtained for the left eye. The patient began taking AREDS2 formula vitamins and was advised to return in 6 months for follow-up. The patient is not a smoker.
Source: Danielle Kalberer, OD, FAAO; Joseph Hallak, OD, FAAO.
Upon follow-up, the patient presented with complaints of a “gradual” further decrease in the vision of his left eye. BCVA was 20/30 OD and 20/200 OS. Amsler grid testing was negative for metamorphopsia in the right eye and positive for blur throughout the grid for the left eye. Mild bilateral age-related lens changes were present. Dilated exam revealed pigment mottling of the right macula with one small pigment epithelial detachment (PED) and pigmentary changes along with a large, elevated, fluid-filled PED in the left macula. OCT macula cube 512 × 128 with five-line raster was performed, and the results confirmed a small extrafoveal intraretinal drusen with a small PED in the right eye (evident in the en face) and a subretinal cyst, PED and fluid leakage in the macula of the left eye.
The patient was immediately referred to a retina specialist. He was scheduled to start anti-VEGF intravitreal injection on a periodic basis in the left eye.
The question remained when treatment should be started in the right eye. Fluorescein angiography (FA) and close follow-up were mandated at best, as there is a high probability of conversion to wet age-related macular degeneration in the right eye. The FA images demonstrate dry AMD in the right eye and exudative in the left.
En face OCT more precise
The term “en face” means “facing forward,” and, as such, this computer iteration program allows the practitioner to view a specific retinal layer as a transverse image. This type of OCT permits more precise mapping of pathological and structural changes.
When used in conjunction with (and ahead of) dynamic retinal testing, such as FA or indocyanine green (ICG), en face OCT provides us with a noninvasive adjunct to determine diagnosis and develop a comprehensive treatment plan. Specific correlations can be made between FA or ICG and en face OCT images, as they all offer coronal views of the retina.
Rosen and colleagues studied patients with neovascular AMD and superimposed en face OCT and ICG images to investigate structural and functional correlates. This study concluded that the two modalities together provided the most accurate information. While the dynamic testing of ICG allowed for identification of neovascularization, the OCT provided greater resolution for areas not visualized easily on ICG, for example, areas of fibrosis or scarring.
En face OCT has also shown utility in conjunction with fundus autofluorescence (FAF) to predict progression of geographic atrophy (GA) in dry AMD. While FAF shows hyperfluorescence at the border of advancing GA, en face OCT of the inner segment/outer segment junction demonstrated areas of darkening that corresponded to the progression over the next year in approximately one-third of patients (Holz et al.).
We can apply the aforementioned to our case. In the initial en face images from 2018, areas of concern appear in both eyes (“areas of darkening” that are highlighted in red). In the follow-up en face images in 2019, 6 months later, a conversion to wet AMD is evident in the left eye (within the highlighted area). The right eye remains essentially stable though the areas of concern, requiring frequent monitoring due to the rapid conversion of its counterpart.
While OCT technology has led to astounding advancements in diagnosis and treatment of retinal conditions, en face OCT technology allows for even more detailed studies compared with the typically used five-line raster or macular cube. In this case study, OCT and en face technology allowed for in-depth examination of various layers of the retinal structure and allowed for judicious timing of follow-up and initiation of treatment for optimal patient care.
References:
Heiferman M, et al. Retina Physician. 2015;12:45-48,50.
Holz FG, et al. Invest Ophthalmol Vis Sci. 2001;42:1051–1056.
Lau T, et al. Indian J Ophthalmol. 2015;doi:10.4103/0301-4738.159860.
Rosen RB, et al. Invest Ophthalmol Vis Sci. 2009;doi:10.1167/iovs.08-1855.
Acknowledgments:
K. Chaudhary, MD, retina specialist, for his input and clinical pearls in the care of our patient. M. Fischer, OD, FAAO, for performing fluorescein angiography on our patient. T. DiBenedetto, optometry student, and J. Hamilton, optometry student, for assistance with imaging modalities.
For more information:
Joseph Hallak, OD, PhD, FAAO, is in private practice in Syosset, N.Y. He can be reached at: drjhallak@aol.com.
Danielle Kalberer, OD, FAAO, practices at the Northport Veterans Affairs Medical Center and is an adjunct assistant clinical professor at the SUNY College of Optometry. She can be reached at: danielle.kalberer@gmail.com.
Disclosures: Hallak and Kalberer report no relevant financial disclosures.
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