May 2015
Volume 56, Issue 5
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Anatomy and Pathology/Oncology  |   May 2015
En Face Imaging of Posterior Precortical Vitreous Pockets Using Swept-Source Optical Coherence Tomography
Author Affiliations & Notes
  • Hirotaka Itakura
    Department of Ophthalmology Gunma University, School of Medicine, Maebashi, Japan
  • Shoji Kishi
    Department of Ophthalmology Gunma University, School of Medicine, Maebashi, Japan
  • Danjie Li
    Department of Ophthalmology Gunma University, School of Medicine, Maebashi, Japan
  • Hideo Akiyama
    Department of Ophthalmology Gunma University, School of Medicine, Maebashi, Japan
  • Correspondence: Hirotaka Itakura, Department of Ophthalmology, Gunma University School of Medicine, 3-39-15 Showa-machi, Maebashi, Gunma, 371-8511, Japan; itakura@gunma-u.ac.jp
Investigative Ophthalmology & Visual Science May 2015, Vol.56, 2898-2900. doi:10.1167/iovs.15-16451
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      Hirotaka Itakura, Shoji Kishi, Danjie Li, Hideo Akiyama; En Face Imaging of Posterior Precortical Vitreous Pockets Using Swept-Source Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2015;56(5):2898-2900. doi: 10.1167/iovs.15-16451.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose.: To obtain sequential flat (en face) images of posterior precortical vitreous pockets (PPVPs) using swept-source optical coherence tomography (SS-OCT).

Methods.: We performed SS-OCT in the right eyes of 112 volunteers (mean age, 30.1 years; mean refraction, −2.5 diopters) while sitting using 12-mm horizontal, vertical scans of the 12- × 9-mm plane × 2.6-mm depth through the macula and optic disc. En face images of the posterior vitreous were obtained by En-View, a SS-OCT program.

Results.: Swept-source OCT visualized the PPVPs and Cloquet's canals in all subjects; the PPVPs appeared as boat-shaped lacunae in the horizontal scan and extended superiorly as clefts in the vertical scan. En face imaging showed PPVPs and Cloquet's canals as two oval lacunae near the vitreoretinal interface and a septum between the nasal border of the PPVPs and Cloquet's canals. In all cases, the lacunas of the PPVPs were larger than those of Cloquet's canals. In 99 (88.4%) of 112 eyes, the PPVPs and Cloquet's canals were fused by connecting channels. The mean width of the connecting channels was 920.2 ± 37.4 μm, and the mean height was 288.6 ± 20.0 μm. On the anterior en face images, the PPVPs became crescent-shaped in all eyes.

Conclusions.: Using SS-OCT, we obtained en face images of PPVPs and Cloquet's canals in vivo. The en face images of the PPVPs near the retina showed oval shapes that changed to crescents, which corresponded to the superior edge of the PPVPs. The PPVPs were fused with Cloquet's canal by a flat-shaped connecting channel.

A posterior precortical vitreous pocket (PPVP or Kishi pocket) is a liquefied lacuna anterior to the macular area that is physiologically present in the vitreous of adults.1 Posterior precortical vitreous pockets were first reported in autopsy eyes, in which the vitreous gel was stained with fluorescein. Worst2,3 described what he saw as the bursa premacularis, which he observed by injecting India ink into the vitreous in postmortem eyes. In his original report, the bursa was anterior to the detached convex-shaped vitreous cortex that forms the subbursal space. Worst3 described septum interpapillomaculare and two channels that connect the bursa and Cloquet's canal. He speculated that inflammation of the anterior chamber after cataract surgery may affect development of cystoid macular edema through the channels. The presence of PPVPs has been confirmed during triamcinolone-assisted vitrectomy4,5 and observed by spectral-domain optical coherence tomography (SD-OCT).6 Enhanced vitreous imaging technique with SD-OCT and combined depth imaging technique on SD-OCT have revealed various structures in the posterior vitreous.7,8 
The anterior border of a PPVP is vitreous gel, and the posterior border is composed of a thin layer of the vitreous cortex attached to the retina. A septum is present between the nasal border of the PPVP and Cloquet's canal.6 The peculiar structure of the premacular vitreous cortex plays a key role in development of various vitreomacular disorders, such as macular holes and idiopathic premacular fibrosis.9 
Swept-source OCT (SS-OCT), a new generation of OCT that provides higher penetration into the choroid and sclera, enables visualization of the vitreous and the choroid. We observed the details of the PPVPs by SS-OCT and identified a connecting channel between the PPVP and Cloquet's canal.10 The presence of the connecting channel suggested the route by which aqueous humor enters the PPVP. Schaal et al.11 have reported further detailed structure of the connection observed by SS-OCT with a schema. Spaide12 tried visualization of anatomic structures in the posterior vitreous using a newly developed technique, dynamic focusing and windowed averaging SS-OCT.12 In this study, we examined sequential flat (en face) images of PPVPs in normal subjects using SS-OCT. 
Methods
We performed SS-OCT (DRI OCT-1 Atlantis; Topcon, Tokyo, Japan) in the right eyes of 112 healthy volunteers (60 men, 52 women) using 12-mm horizontal, vertical, and three-dimensional scans through the macula and the optic disc. This study included consecutive subjects examined from August 2012 to July 2014. The subjects' ages ranged from 21 to 40 years (average, 30.1 ± 0.6 years). To minimize age-related changes (liquefaction or posterior vitreous detachment), all subjects were between 21 and 40 years according to findings in our previous report.13 
The OCT examinations of all subjects were performed with the volunteers in the sitting position. During the OCT examination, we placed the scanner head backward to visualize the vitreous structure in the B-scan images of the 12- × 9-mm plane × 2.6-mm depth including the macula and the optic disc. The retina and the choroid were positioned at the lower border of the image plane to increase the visibility of the vitreous. After obtaining the OCT images, we adjusted the contrast to enhance the images of the gel, liquefied pocket, and cortex. En face images of the posterior vitreous were obtained by En-View, a program in the SS-OCT. The vertical diameter (width) and horizontal diameter (length) of the PPVP and Cloquet's canal were measured from the en face images of the posterior vitreous near the retina using the scaling program in the SS-OCT unit. The length, width, and distance from the retina of the connecting channel between the PPVP and Cloquet's canal also were measured using the scaling program. 
The refractive powers, measured using the RT-6000 Auto Ref-Topography (Tomey, Nagoya, Japan), ranged from −7.75 to +1 diopter (D) (average, −2.5 ± 0.2 D). Subjects with high myopia exceeding −8.0 D were excluded because highly myopic eyes have larger PPVPs and earlier progression of posterior vitreous detachments than normal eyes.14 
All measured values are expressed as the mean ± standard error. 
The study was conducted according to the tenets of the Declaration of Helsinki. The Gunma University Hospital Institutional Review Board approved this study. All subjects provided informed consent for participation in this research. 
Results
Swept-source OCT visualized the PPVPs and Cloquet's canals in all subjects. The PPVPs were observed as boat-shaped lacunae in the horizontal scans. In the vertical scans, the PPVPs extended superiorly like a cleft, and the inferior portion was flat in all eyes. In the en face images, the PPVPs and Cloquet's canals appeared as two oval lacunas near the vitreoretinal interface with a septum between the nasal border of the PPVPs and Cloquet's canals (Figure). In all cases, the lacunas of the PPVPs were larger than those of Cloquet's canals in length and width on the en face images. The mean length and width of the PPVPs were 6546.1 ± 85.5 μm (range, 4655–8530 μm) and 5795.7 ± 97.7 μm (range, 3497–8012 μm). The mean length and width of Cloquet's canals were 1934.2 ± 32.8 μm (range, 1045–2734) and 3153.2 ± 36.7 μm (range, 1984–4152 μm). 
Figure
 
Swept-source OCT imaging of a PPVP in the right eye of a 39-year-old man. In a horizontal scan, the PPVP appears as a boat-shaped lacuna, and there is a connecting channel between the PPVP and Cloquet's canal (arrow). In a vertical scan, the superior portion of the PPVP is larger than the inferior portion. Two en face images were obtained of the upper area (A) and lower area (B) of a PPVP. The PPVP and Cloquet's canals are connected by a channel away from the retina (arrow). The anterior en face image of the PPVP shows that the structure becomes crescent-shaped (arrowhead). p, PPVP; c, Cloquet's canal.
Figure
 
Swept-source OCT imaging of a PPVP in the right eye of a 39-year-old man. In a horizontal scan, the PPVP appears as a boat-shaped lacuna, and there is a connecting channel between the PPVP and Cloquet's canal (arrow). In a vertical scan, the superior portion of the PPVP is larger than the inferior portion. Two en face images were obtained of the upper area (A) and lower area (B) of a PPVP. The PPVP and Cloquet's canals are connected by a channel away from the retina (arrow). The anterior en face image of the PPVP shows that the structure becomes crescent-shaped (arrowhead). p, PPVP; c, Cloquet's canal.
In 99 (88.4%) of 112 eyes, the PPVPs connected to Cloquet's canals by channels that were 432.0 ± 17.2 μm (range, 77–800 μm) away from the retina. The mean width of the connecting channels was 920.2 ± 37.4 μm (range, 302–2187 μm), and the mean height was 288.6 ± 20.0 μm (range, 38–1233 μm). 
The anterior en face images of the PPVPs showed that the structure became crescent-shaped in all eyes. 
Discussion
Using SS-OCT, we obtained en face images of the PPVPs and Cloquet's canals in vivo. During triamcinolone-assisted vitrectomy, the in vivo images of the PPVP and Cloquet's canal showed only stained posterior walls of the PPVPs. The en face images of the PPVPs near the retina showed oval shapes that changed to crescent shapes at the anterior plane, which corresponded to the superior edge of the PPVPs. In the vertical OCT scans obtained with the subjects sitting, the superior portion of the PPVP always extended superiorly, and the anterior border of the PPVP moved anteriorly when the participants were supine.15 The characteristic transformation of the PPVP in the sitting and supine positions suggests the specific weight, although specific gravity of vitreous gel versus PPVP contents is not clear. Because SS-OCT enabled observation to a depth of 2.6 mm, the PPVP extended superiorly beyond the superior border of the image in the vertical scans. In the current study, the en face images did not show the superior tip of the PPVP. A device that can visualize the increased depth from the vitreoretinal interface is needed to observe the entire PPVP. 
The methodology to determine PPVP size is fundamentally flawed since it appears to be based on the assumption that the PPVP is a boat-shaped space. This has recently been challenged by Schaal et al.11 and Spaide.12 We measured the vertical and horizontal diameters of the PPVP and Cloquet's canal from the en face images of the posterior vitreous near the retina using the scaling program in the SS-OCT unit. 
The PPVPs were fused with Cloquet's canal by a connecting channel at the plane 77 to 800 μm away from the retina in most cases. The mean width of the connecting channels was 920.2 ± 37.4 μm (range, 302–2187 μm), and the mean height was 288.6 ± 20.0 μm (range, 38–1233 μm). These results served a new finding that the shape of the connecting channel is not circular but flat. 
In some cases the connecting channel was not identified. The PPVPs are seen in front of the macula as a flat space in early childhood, and the channel connecting the PPVP and Cloquet's canal begins to form after age 5.16 In the current study, the connecting channel was seen in most (88.4%) eyes in adulthood. It is unclear why the remaining 13 eyes had incomplete formation of the connecting channel or why it was present more superiorly. 
In conclusion, SS-OCT showed en face images of PPVPs and Cloquet's canals in all subjects in vivo. The images showed the connecting channel between the PPVPs and Cloquet's canals within a depth of 2.6 mm from retina in most subjects (88.4%). 
Acknowledgments
The authors have no proprietary interest in any aspect of this report. 
Disclosure: H. Itakura, None; S. Kishi, None; D. Li, None; H. Akiyama, None 
References
Kishi S, Shimizu K. Posterior precortical vitreous pocket. Arch Ophthalmol. 1990; 108: 979–982.
Worst J. Cisternal systems of the fully developed vitreous body in the young adult. Trans Ophthalmol Soc U K. 1977; 97: 550–554.
Worst J. Extracapsular surgery in lens implantation (Binkhorst lecture). Part IV. Some anatomical and pathophysiological implications. J Am Intraocul Implant Soc. 1978; 4: 7–14.
Sakamoto T Miyazaki M, Hisatomi T et al. Triamcinolone-assisted pars plana vitrectomy improves the surgical procedures and decreases the postoperative blood-ocular barrier breakdown. Graefes Arch Clin Exp Ophthalmol. 2002; 240: 423–429.
Fine HF, Spaide RF. Visualization of the posterior precortical vitreous pocket in vivo with triamcinolone. Arch Ophthalmol. 2006; 124: 1663.
Itakura H Kishi S. Aging changes of vitreomacular interface. Retina. 2011; 31: 1400–1404.
Pang CE Freund KB, Engelbert M. Enhanced vitreous imaging technique with spectral-domain optical coherence tomography for evaluation of posterior vitreous detachment. JAMA Ophthalmol. 2014; 132: 1148–1150.
Barteselli G Bartsch D-U, El-Emam S et al. Combined depth imaging technique on spectral-domain optical coherence tomography. Am J Ophthalmol. 2013; 155: 727–732.
Kishi S, Hagimura N Shimizu K. The role of the premacular liquefied pocket and premacular vitreous cortex in idiopathic macular hole development. Am J Ophthalmol. 1996; 122: 622–628.
Itakura H Kishi S, Li D Akiyama H. Observation of posterior precortical vitreous pocket using swept-source optical coherence tomography. Invest Ophthalmol Vis Sci. 2013; 54: 3102–3107.
Schaal KB Pang CE, Pozzoni MC Engelbert M. The premacular bursa's shape revealed in vivo by swept-source optical coherence tomography. Ophthalmology. 2014; 121: 1020–1028.
Spaide RF. Visualization of the posterior vitreous with dynamic focusing and windowed averaging swept source optical coherence tomography. Am J Ophthalmol. 2014; 158: 1267–1274.
Itakura H Kishi S. Evolution of vitreomacular detachment in normal subjects. JAMA Ophthalmol. 2013; 131: 1348–1352.
Itakura H Kishi S, Li D Nitta K, Akiyama H. Vitreous changes in high myopia observed by swept-source optical coherence tomography. Invest Ophthalmol Vis Sci. 2014; 55: 1447–1452.
Itakura H Kishi S. Alterations of posterior precortical vitreous pockets with positional changes. Retina. 2013; 33: 1417–1420.
Li D Kishi S, Itakura H Ikeda F, Akiyama H. Posterior precortical vitreous pockets and connecting channels in children on swept-source optical coherence tomography. Invest Ophthalmol Vis Sci. 2014; 55: 2412–2416.
Figure
 
Swept-source OCT imaging of a PPVP in the right eye of a 39-year-old man. In a horizontal scan, the PPVP appears as a boat-shaped lacuna, and there is a connecting channel between the PPVP and Cloquet's canal (arrow). In a vertical scan, the superior portion of the PPVP is larger than the inferior portion. Two en face images were obtained of the upper area (A) and lower area (B) of a PPVP. The PPVP and Cloquet's canals are connected by a channel away from the retina (arrow). The anterior en face image of the PPVP shows that the structure becomes crescent-shaped (arrowhead). p, PPVP; c, Cloquet's canal.
Figure
 
Swept-source OCT imaging of a PPVP in the right eye of a 39-year-old man. In a horizontal scan, the PPVP appears as a boat-shaped lacuna, and there is a connecting channel between the PPVP and Cloquet's canal (arrow). In a vertical scan, the superior portion of the PPVP is larger than the inferior portion. Two en face images were obtained of the upper area (A) and lower area (B) of a PPVP. The PPVP and Cloquet's canals are connected by a channel away from the retina (arrow). The anterior en face image of the PPVP shows that the structure becomes crescent-shaped (arrowhead). p, PPVP; c, Cloquet's canal.
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