Danjie Li

Fumiko Ikeda

Hideo Akiyama

Hirotaka Itakura

Shoji Kishi

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Anatomy and Pathology
Posterior Precortical Vitreous Pockets and Connecting
Channels in Children on Swept-Source Optical
Coherence Tomography
Danjie Li, Shoji Kishi, Hirotaka Itakura, Fumiko Ikeda, and Hideo Akiyama
Department of Ophthalmology, Gunma University, School of Medicine, Maebashi, Japan
Correspondence: Danjie Li, Depart-
ment of Ophthalmology, Gunma
University School of Medicine, 3-39-
15 Showa-machi, Maebashi, Gunma,
371-8511, Japan;
lidanjie@gunma-u.ac.jp.
Submitted: January 17, 2014
Accepted: February 27, 2014
Citation: 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. DOI:10.1167/iovs.14-13967
PURPOSE. We observed the posterior vitreous in children using swept-source optical coherence
tomography (SS-OCT).
METHODS. The normal right eyes of 73 children (ages, 3–11 years) were studied using SS-OCT
with 12-mm horizontal and vertical scans in the posterior fundus.
RESULTS. Posterior precortical vitreous pockets (PPVPs), narrow liquefied spaces along the
vitreoretinal interface in the macula (mean, 165.4 6 35.2 lm [depth] 3 3327 6 615.7 lm
[width]), were observed at age 3 in horizontal scans. The PPVPs enlarged to 382.9 6 51.8 3
4486.5 6 342.3 from ages 4 to 6 (P < 0.01) and 524.9 6 60.3 3 5485.9 6 307.5 after age 7
(P < 0.01). In all subjects, the depth and width were means of 426.4 6 38.2 and 4834.4 6
228.1 lm, respectively. There were significant correlations between the PPVP size and age
(PPVP depth, r ¼ 0.42, P < 0.001; PPVP width, r ¼ 0.42, P < 0.001), but not refractive error.
The PPVP posterior wall was not visible in all eyes. The PPVP and Cloquet’s canal appeared as
separate spaces at ages 3 and 4 years. The connecting channel between the PPVPs and
Cloquet’s developed in 7.7%, 11.1%, 12.5%, 27.3%, 40%, 37.5%, and 50% at ages 5, 6, 7, 8, 9,
10, and 11, respectively.
CONCLUSIONS. The PPVPs emerged in front of the macula as a solitary space in early childhood.
They first were narrow liquefied spaces anterior to the macula at age 3 and evolved to small
boat-shaped spaces that gradually enlarged with age. The channels connecting the PPVPs and
Cloquet’s canal begin to form after age 5. Their presence suggests a physiologic role of the
PPVPs.
Keywords: posterior precortical vitreous pocket, Cloquet’s canal, connecting channel, swept-
source optical coherence tomography
The vitreous is a gel-like structure that occupies approxi-mately four-fifths of the ocular volume. At birth, the
posterior vitreous gel is secondary vitreous. Cloquet’s canal
is the remnant of the primary vitreous that arises from the
optic disc, traverses the core vitreous, and ends in the
retrolental space. It is known that vitreous changes its
structure after birth to adulthood. Eisner1 reported that
vitreal tracts emerge during adolescence and become fully
develop in adulthood. Worst2,3 reported the presence of
cisternal systems in the fully developed vitreous body in
young adults. He described ‘‘bursa premacularis,’’ which is
situated on the convexly detached vitreous cortex in the
macular area. Kishi and Shimizu4 discovered the presence of
posterior precortical vitreous pockets (PPVPs) in adult eyes
and explained their role in various vitreoretinal interface
diseases. Although PPVP and bursa premacularis are defined
differently, many investigators call PPVP as bursa premacu-
laris.5–9 Because of the vitreous transparency, it is difficult to
observe the vitreous structure in vivo. Triamcinolone-assisted
vitrectomy provided the chance to observe the PPVP
intraoperatively.10,11 Spectral-domain optical coherence to-
mography (OCT) enabled partial visualization of the
PPVP.6,12–14 Newly developed swept-source OCT (SS-OCT)
visualizes the entire structure of the PPVP in vivo, which
accelerated the study of the vitreous.7–9,15 We previously
reported the anatomic characteristics of the PPVP and
precursor stage of posterior vitreous detachment in normal
adults.7,14 In the current study, we clarified the evolution of
the PPVP in children using SS-OCT.
METHODS
The study included 28 normal children and 45 children (39
girls, 34 boys) who visited the strabismus service at Gunma
University Hospital, but had no ocular abnormalities except for
minor refractive errors. The subjects underwent a complete
ophthalmic examination in both eyes, including measurement
of the refractive error and best-corrected visual acuity (BCVA)
level, anterior segment examination, and indirect ophthalmos-
copy. The ages of the children ranged from 3 to 11 years (mean,
83.8 6 3.1 months; age 3, n¼ 8; age 4, n¼ 8; age 5, n¼ 14; age
6, n¼ 9; age 7, n¼ 8; age 8, n¼ 11; age 9, n¼ 5; age 10, n¼ 8;
and age 11, n ¼ 2).
Two investigators (DL, HI) performed SS-OCT (DRI OCT-1
Atlantis; Topcon, Tokyo, Japan) using 12-mm horizontal and
vertical scan lines through the fovea and optic disc. All subjects
Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.
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were sitting during the examination. The vitreous mode was
used to obtain clear visualization of the posterior vitreous. The
focus was adjusted to obtain the best image of the PPVP and
Cloquet’s canal. We measured the depth and width of the PPVP
(Fig. 1) in all eyes to determine the size of the PPVP from the
horizontal scanning line through the fovea. When Cloquet’s
canal or the connecting channel was not visible in the standard
horizontal scan, we performed further horizontal scans as
often as possible to visualize the structures at the posterior
pole, especially around the optic disc. After obtaining the SS-
OCT images, we modified the contrast and brightness to
enhance the structure of the posterior vitreous.
We investigated the relationship between the PPVP and
Cloquet’s canal in the posterior vitreous. We compared the
depth and width of the PPVPs in three age groups: ages 3, 4 to
6, and 7 to 11 years. In all subjects, we analyzed the correlation
between the PPVP size, and subjects’ age and refractive errors.
The correlations evaluated in the respective groups (age,
refractive error, size of the PPVPs) were analyzed using
Spearman’s rank correlation coefficient test. To determine
the significance of the differences, based on normal distribu-
tion of all data, the Mann-Whitney U test and Student’s t-test
were performed. Statistical analysis was performed using State
CEL 2 in the Excel 2012 software (Microsoft Corporation,
Redmond, WA, USA). The Bonferroni correction was used for
multiple comparisons. A P value less than 0.05 was considered
statistically significant.
This research adhered to the tenets of the Declaration of
Helsinki. The participant’s parents gave informed consent after
explanation of the nature and possible consequences of the
study. The research was approved by the Ethics Committee of
Gunma University Graduate School of Medicine.
RESULTS
The BCVAs of the 73 eyes ranged from 0.6 to 1.2 (average, 1.0
decimal VA). The refractive values ranged from 4 to þ10.25
diopters (D; average, þ1.95 6 0.37 D).
Although the configurations and sizes of the PPVPs differed
with age, a PPVP was observed in 71 (97.3%) of 73 eyes with
the exception of two eyes of children aged 4 and 5 years. All
PPVPs were boat-shaped with an elevated peripheral edge in
the horizontal scan, and the widths of PPVP were longer than
the depths in the 71 eyes (t¼19.3, P < 0.001; Figs. 1, 2). In the
vertical scans, the superior portion of the PPVPs was elevated
superiorly while the subjects were sitting; thus, the width and
central depth of the PPVPs were not determined in the vertical
scans.
Figure 3 shows the PPVPs in the horizontal scans obtained
from the three age groups. Figures 4A and 4B show the
comparison among the three groups in the depths and widths
of the PPVPs. The PPVPs appeared as narrow liquefied spaces
along the vitreoretinal interface in the macula (Fig. 3A) at age 3
years (mean depth, 165.4 6 35.2 lm) in eight children. In 29
eyes with a PPVP in children ages 4 to 6 years (Fig. 3B), the
PPVPs were deeper (P < 0.05; mean, 382.9 6 51.8 lm) than
those seen in children aged 3 years, but still shorter (P < 0.05)
compared to subjects over 7 years. The anterior border of the
PPVPs became more clearly demarcated in children over age 7
(Fig. 3C). The posterior wall or premacular vitreous cortex was
too thin to identify. In 34 children aged 7 to 11 years (Fig. 3C),
the PPVPs enlarged (P < 0.05) with a well-demarcated anterior
border. The mean depth was 524.9 6 60.3 lm. A thin vitreous
cortex was seen at the periphery of the posterior wall of the
PPVP. The widths of the PPVP in the children over 7 years
(mean, 5485.9 6 307.5 lm) were larger than in those who
were 3 year old (mean, 3327 6 615.7 lm) and those who were
4 to 6 years old (mean, 4486.5 6 342.3 lm; P < 0.05 for both
comparisons). However, although the widths of the PPVPs in
the 4- to 6-year-old group tended to enlarge compared to those
in the 3-year-old group, the difference did not reach
significance (P > 0.05). In all 71 eyes in which a PPVP was
identified, the depths ranged from 49 to 1512 lm (mean, 426.4
6 38.2 lm) and the widths ranged from 545 to 8594 lm
(mean, 4834.4 6 228.1 lm). Figures 4C and 4D show that the
depths and widths of the PPVPs increased with age (depth, r¼
0.42, P < 0.001; width, r¼ 0.42, P < 0.001), but no significant
correlation with the refractive error (P > 0.05) was seen.
However, the refractive error shifted to myopia with increasing
age (r ¼0.31, P < 0.05).
The PPVPs and Cloquet’s canal separate in the eyes of all
subjects examined aged 3 and 4 years. Cloquet’s canal was seen
in 72 (98.6%) of 73 eyes (Figs. 1, 3) with the exception of one
eye of children aged 5 years (PPVP had not been observed).
With expansion of the PPVPs, the gel between the PPVPs and
Cloquet’s canals was attenuated and formed a septum (Fig. 3).
The septum was thinned gradually, until the formation of a
channel. The channel between the two spaces developed
mostly at the superior edge of the septum (Fig. 3D). A
connecting channel between the PPVPs and Cloquet’s canals
developed in 7.7% at age 5, 11.1% at age 6, 12.5% at age 7,
FIGURE 1. An OCT 12-mm horizontal scan through the fovea in the
right eye of a 7-year-old boy. The depth and width of the PPVP
represents the size of PPVP. The black asterisk indicates the septum
between the PPVP and Cloquet’s canal (CC).
FIGURE 2. In the 71 eyes with a PPVP, the widths are (Student’s t-test, t
¼ 19.3, P < 0.001) significantly longer than the depths.
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FIGURE 3. Three SS-OCT horizontal scans through the fovea of (A) a 3-year-old girl, (B) a 6-year 11-month-old girl, and (C) an 8-year-old girl. The
PPVPs are seen clearly on the fovea and CC on the optic disc, but no connecting channels between the PPVPs and CC are seen. The black arrow (A)
indicates a small PPVP on the fovea. (D) A SS-OCT image is a horizontal scan above the fovea in the same eye as in (C). The white arrow indicates a
connecting channel between a PPVP and CC. The black asterisks indicate a septum between the PPVP and CC.
FIGURE 4. (A, B) The boxplots show the depth and width of the PPVPs in three age groups (3, 4–6, and 7–11 years). There are significant
differences (P < 0.05, P < 0.01) except for the width between the 3-year-old age group and 4- to 6-year-old age group (P > 0.05). (C, D) The
scatterplots show the relationship between the depth and width of the PPVPs and age (months). The width and depth increase with age. r,
correlation coefficient of Spearman rank correlation test; ns, not significant.
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27.3% at age 8, 40% at age 9, 37.5% at age 10, and 50% at age 11
(Fig. 5). In all subjects, a connecting channel between the
PPVPs and Cloquet’s canals was seen in 12 (16.9%) of all 71
eyes with a PPVP, and the incidence increased with age.
DISCUSSION
The current study showed that PPVPs appeared as narrow
liquefied spaces in front of the fovea at age 3. From age 4 years,
the PPVPs enlarged and the anterior border became well
demarcated. The PPVPs and Cloquet’s canals were separate
spaces in all children aged 3 and 4 years, but the channel
connecting the two spaces was seen in 7.7% at age 5, which
increased to 50% after age 11. Yokoi et al.8 reported that a
PPVP was not seen in a 2-year-old boy on SS-OCT images.
Those investigators observed a vitreous crack anterior to the
macula, which was connected to Cloquet’s canal in a 3-year-old
girl. The investigators observed a PPVP in an 8-year-old boy.
The PPVPs always were observed in children over age 10 years.
Kishi and Shimizu4 first reported the presence of PPVPs in
autopsy eyes in which the vitreous was stained with
fluorescein and observed by slit-lamp biomicroscopy. A PPVP
was not present in the eye of a 2-year-old child, but local
liquefaction was seen at the macula. The next youngest eye
among their specimens was that of a subject who was 26 years,
and this eye had a fully developed PPVP.
Itakura et al.7 examined the posterior vitreous in 58 normal
subjects who ranged in age from 22 to 40 years using SS-OCT. A
PPVP was observed in all eyes.
Stanga et al.15 also examined normal eyes aged 5 to 100
years using SS-OCT, They observed a bursa premacularis (or
PPVP) detected in 57.1% of eyes. The bursa premacularis and
Cloquet’s canals coexisted in 97.8% of eyes.
The current study and previous reports have suggested that
PPVPs emerge as small liquefied spaces in front of the macula,
develop into a boat-shaped liquefied space at approximately
ages 4 to 7 years, and fully evolve after age 10. The connecting
channels between the PPVPs and Cloquet’s canals were seen in
54 (93.1%) of 58 adults.7 Since the incidence increased from
7.7% at age 5 to 50% at age 11 in the current study, this
structure appears to develop during childhood.
Although many investigators view these cisternae or PPVPs
as the result of age-related vitreous degeneration, the current
results suggested that PPVPs and the connecting channels are
anatomic structures in the vitreous that start to develop after 3
years of age and reach full development at approximately age 7
years.
Larsen17 reported that the ocular axial length increases
acutely after birth to age 1.5 years (first term), grows gradually
from ages 2 to 5 years (second term), and grows minimally
from ages 6 to 13 years (third term). The axial length reaches
almost the same size as that in adults at age 7 from 17 mm at
birth to approximately 23.50 mm. Along with the postnatal
ocular growth, PPVPs and connecting channels also seem to
develop.
We previously studied the role of PPVPs in various
vitreoretinal interface diseases, such as macular holes, epire-
tinal membranes, and proliferative diabetic retinopathy.5,18,19
Recent studies of normal adults and children using SS-OCT
showed that PPVPs emerge as narrow liquefied space in front
of the macula and gradually enlarge their size during
childhood. Cloquet’s canal was thought to be a remnant of
the primary vitreous. However, Yokoi et al.8 reported a
liquefied crack that arose from Cloquet’s canal and enlarged
into a PPVP. Although there is no evidence to discuss the
function of the PPVPs at this time, Cloquet’s canal and the
connecting channel may serve a route by which aqueous
humor drains into the PPVP. The aqueous has a high
concentration of vitamin C, which neutralizes the radicals
generated in the crystalline lens. The macula appears to
produce a high concentration of radicals. If aqueous humor
drains into the PPVP, it may protect the macula from the stress
of radical oxygen.
In conclusion, PPVPs emerged in front of the macula as a
solitary space in early childhood. They first were narrow
liquefied spaces anterior to the macula at age 3 and evolved to
small boat-shaped spaces that gradually enlarged with age. The
channels connecting the PPVPs and Cloquet’s canals are
anatomic structures that develop postnatally. Their presence
suggests a physiologic role of the PPVPs.
Acknowledgments
The authors alone are responsible for the content and writing of
the paper.
Disclosure: D. Li, None; S. Kishi, None; H. Itakura, None; F.
Ikeda, None; H. Akiyama, None
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FIGURE 5. The numbers of eyes with and without a connecting channel between the PPVPs and CCs in each age group.
PPVPs and Connecting Channels in Children IOVS j April 2014 j Vol. 55 j No. 4 j 2415
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Anatomy and Pathology Posterior Precortical Vitreous Pockets and Connecting Channels in Children on Swept-Source Optical Coherence Tomography

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Anatomy and Pathology Posterior Precortical Vitreous Pockets and Connecting Channels in Children on Swept-Source Optical Coherence Tomography

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