From the Department of Ophthalmology, Asahikawa Medical College, Asahikawa, Japan.
The authors have no financial or proprietary interest in the materials presented herein.
Address correspondence to Atsushi Takahashi, MD, Department of Ophthalmology, Asahikawa Medical College, 2-1-1-1, Midorigaoka-Higashi, Asahikawa, 078-8510, Japan.
A perifoveal posterior vitreous detachment (PVD) may be complicated by various macular disorders as the result of static and dynamic tractional effects. The disorders caused by perifoveal PVD are determined partly by the size and strength of the vitreomacular adhesion.1 Zambarakji et al.2 reported optical coherence tomography (OCT) 3 (Stratus, Carl Zeiss Meditec Inc., Dublin, CA) findings in patients with small outer retinal defects or cysts, i.e., macular microholes. Although vitreomacular traction has been theorized to be the anatomic mechanism responsible for the development of macular microholes,2,3 the exact mechanism remains unclear.
We report a case of a macular microhole of an outer retinal defect visualized on OCT 3 imaging as an elevated photoreceptor layer with a perifoveal PVD using the OCT ophthalmoscope (C7, Nidek Co. Ltd., Gamagori, Japan). We performed sequential investigations with both OCTs to evaluate the anatomic changes before and after detachment of the posterior hyaloid from the fovea. We discuss the possible reasons for formation of macular microholes of the outer retinal defects.
A 47-year-old woman was referred to our department for symptoms in the right eye of a small central scotoma and metamorphopsia on an Amsler chart at the initial visit. She had no history of ocular surgeries or gazing at the sun. Her best-corrected visual acuity (BCVA) was 20/25 in the right eye and 20/20 in the left eye (−6.5 diopters [D] sphere bilaterally). Only a tigroid fundus and no obvious foveal abnormalities without a Weiss ring were seen during a dilated fundus examination of the right eye (Fig. 1A). OCT 3 showed a small outer retinal defect and an intact retinal pigment epithelium layer with a perifoveal vitreous detachment that appeared as a thin backscattering line in a smooth convex curve (Fig. 1B). The OCT ophthalmoscope showed the reflectivity of the perifoveal PVD, which was seen as a thin line by the precipitous posterior dip of the hyaloid face to the fovea in a smooth biconvex curve (Fig. 1C). A magnified view of the foveal image showed that the elevation in the photoreceptor layer was under the hyperreflectivity of the small irregular foveal contour (Fig. 1D). Fluorescein angiography and indocyanine green angiography showed a normal macula. One month later, a small outer retinal defect was seen clearly, and the faint reflectivity of the posterior hyaloid had separated and was visible as a thin line from the macula on an OCT 3 image (Fig. 2A), but the visual symptoms persisted. Six months after the initial visit, there were no symptoms in the right eye. On examination, the BCVA had increased to 20/20 in the right eye. Both OCTs showed that the photoreceptor layer abnormality had disappeared. The vitreous was detached and visible as a thin backscattering line above the macula (Figs. 2B and 2C). The photoreceptor layer abnormality and visual symptoms resolved almost simultaneously.
Figure 1. Images of the Right Eye at the First Visit. (A) A Fundus Photograph Shows a Tigroid Fundus and No Obvious Foveal Abnormalities. (B) OCT 3 Shows a Small Outer Retinal Defect (arrow) and an Intact Retinal Pigment Epithelium Layer with a Perifoveal PVD Seen as a Thin Backscattering Line (arrowheads) in a Smooth Convex Curve. (C) OCT Ophthalmoscope Shows the Reflectivity of the Perifoveal PVD, Seen as a Thin Line by the Posterior Precipitous Dip of the Posterior Hyaloid to the Fovea in a Smooth Biconvex Curve (arrowheads). (D) The Magnified Foveal Image of Figure 1C Shows that the Photoreceptor Layer Elevation (white Arrow) is Under the Hyperreflectivity of the Small Irregular Foveal Contour (yellow Arrow).
Figure 2. Images Obtained During Follow-Up. (A) One Month Later, OCT 3 Shows a Small Outer Retinal Defect (arrow) and the Faint Reflectivity of the Vitreomacular Detachment (arrowheads). (B) Six Months After the Initial Visit, OCT 3 Shows that the Outer Retinal Defect has Disappeared (arrow) with Faint Reflectivity Seen as a Thin Line of Complete Vitreomacular Separation (arrowheads). (C) Six Months After the Initial Visit, OCT Ophthalmoscope Shows that the Photoreceptor Layer Abnormality has Disappeared (arrow), with Faint Dome-Shaped Reflectivity Appearing as a Thin Line of Complete Vitreomacular Separation (arrowheads).
Although the term “macular microhole” has been used to refer to a small full-thickness macular hole before OCT became available,4,5 Zambarakji et al.2 reported that 15 of 18 (83%) eyes with a diagnosis of a microhole examined by OCT 3 had an outer retinal defect and there were no full-thickness retinal defects. Therefore, we use the term macular microhole to describe a defect in the outer retina.2,3,6 Lai and colleagues7 described a 62-year-old patient with a small full-thickness macular microhole with vitreofoveal separation and an operculum that resolved spontaneously, which was not a case of a macular microhole of the outer retinal defect. To resolve the controversy surrounding the term macular microhole, we propose that a small full-thickness retinal defect be referred to as a full-thickness macular microhole and an outer retinal defect be referred to as a macular microhole of the outer retinal defect.
Two possible theories have been forwarded about the outer retinal defect in the central fovea. Privat and colleagues8 reported the presence of a residual defect on OCT 3 scans in the photoreceptor layer at the foveal center in eyes with a macular hole that closed spontaneously preoperatively. Those investigators stated that if the posterior hyaloid detached from the macula with a pseudo-operculum is visible or if a posterior hyaloid detachment is complete in patients 60 years of age or older, the presence of a central foveal defect in the photoreceptor layer seems to indicate that a macular hole closed spontaneously. The authors also stated that there are other causes of small central disruptions of the foveal photoreceptor layer in younger patients. The status of the posterior hyaloid plays an important role in whether there has been spontaneous resolution of a macular hole or a macular microhole of the outer retinal defect. Although ruling out that a macular hole closed spontaneously is difficult in a case in which vitreofoveal separation is present initially, our current case is not such as case, because a full-thickness macular hole was not present when the posterior hyaloid was still attached to the fovea at the initial visit and the operculum was not visible after the posterior hyaloid was detached from the fovea.
The quality of the OCT 3 images of the posterior hyaloid was weak, although it resembled a perifoveal PVD in a smooth convex curve. Therefore, we used the OCT ophthalmoscope to highlight the status of the posterior hyaloid in the smooth biconvex curve of a perifoveal PVD. However, the quality of the OCT scans of the posterior hyaloid near the fovea is lower and cannot clearly show the vitreofoveal adhesion, and the OCT ophthalmoscope image showed a small area of hyperreflectivity of the irregular foveal contour in the fovea, possibly indicating vitreofoveal adhesion. Several stages of partial PVD have been defined using OCT; Uchino et al.9 reported that the initial manifestation of PVD is a focal shallow detachment from the perifoveal retina, with persistent attachment to the fovea and optic nerve head in the smooth biconvex curve of the posterior vitreous hyaloid. This aged-related PVD starts initially in healthy eyes as early as the fourth decade of life. Therefore, in the current case of a macular microhole of an outer retinal defect observed at the first visit, the posterior hyaloid was detached partially over the posterior pole but still adhered to the fovea, resulting in a biconvex appearance.
The current case was similar to those cases described by Witkin and colleagues10 those authors reported an irregular foveal contour and perifoveal PVD with metamorphopsia without photoreceptor layer abnormalities on a high-speed ultra-high-resolution OCT image. They also reported a case similar to the current case; however, the OCT findings of that patient had photoreceptor disruption with an irregular foveal contour and vitreofoveal separation without metamorphopsia and images of vitreofoveal adhesion or perifoveal PVD.11 In the current case, the elevation in the photoreceptor layer may have resulted from a perifoveal PVD, because the outer foveal anatomy returned to normal over time after vitreomacular separation with resolution of visual symptoms. Gass speculated that the ultrastructure of the Müller cell cone binds the photoreceptor cells to the foveola.12 A macular hole was theorized to develop as the result of anteroposterior traction resulting from a perifoveal PVD.13 Although a study with a larger number of patients is needed to determine if this is the mechanism by which macular microholes develop in an outer retinal defect, contraction of the prefoveolar vitreous cortex may cause mild traction on the Müller cell cone, resulting in small abnormalities in the photoreceptor layer.
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