Vitreous surgery in the management of chronic endogenous posterior uveitis

Abstract

There is evidence that pars plana vitrectomy (PPV) has a beneficial effect on the clinical course of chronic endogenous posterior uveitis (EPU) possibly by physically removing any resident inflammatory cells with the vitreous. We assessed the anatomical and therapeutic effects of PPV performed on patients with chronic EPU for any indication.
Retrospective review of 41 eyes of 38 consecutive patients with EPU who underwent a PPV for any reason, over a 5-year period. The mean age of the patients was 36.2 years, 46% of the eyes had intermediate uveitis, 32% panuveitis, and 22% posterior uveitis. The visual acuity, disease activity, and the requirement for medications to control it were recorded for 12 months pre- and postoperatively.
Overall, 61% of the eyes gained more than 2 Snellen lines (P<0.001) and the incidence of cystoid macular oedema (CMO) significantly reduced from 44 to 20% (P<0.05). Postoperatively, there was a significant decrease in the recurrence rate of intermediate uveitis, posterior uveitis, and panuveitis (P<0.001). The use of systemic and local depot immunosuppressive agents did not change over the study period, although the use of topical agents increased (P<0.05).
PPV appears to have a beneficial effect on the clinical course of EPU in selected cases. This may be mediated by the physical clearance of inflammatory debris, the anti-inflammatory effect of replacing vitreous by aqueous humour, by a reduction of CMO and/or the anatomical correction of sight-threatening retinal pathology.

Full text

Vitreous surgery in
the management of
chronic endogenous
posterior uveitis
RA Scott1, RJ Haynes2, GM Orr2, R J Cooling1,
CE Pave
´sio1and DG Charteris1
Abstract
Objectives There is evidence that pars plana
vitrectomy (PPV) has a beneficial effect on the
clinical course of chronic endogenous
posterior uveitis (EPU) possibly by physically
removing any resident inflammatory cells with
the vitreous. We assessed the anatomical and
therapeutic effects of PPV performed on
patients with chronic EPU for any indication.
Patients and methods Retrospective review
of 41 eyes of 38 consecutive patients with EPU
who underwent a PPV for any reason, over a 5-
year period. The mean age of the patients was
36.2 years, 46% of the eyes had intermediate
uveitis, 32% panuveitis, and 22% posterior
uveitis. The visual acuity, disease activity, and
the requirement for medications to control it
were recorded for 12 months pre- and
postoperatively.
Results Overall, 61% of the eyes gained more
than 2 Snellen lines (Po0.001) and the
incidence of cystoid macular oedema (CMO)
significantly reduced from 44 to 20% (Po0.05).
Postoperatively, there was a significant
decrease in the recurrence rate of intermediate
uveitis, posterior uveitis, and panuveitis
(Po0.001). The use of systemic and local depot
immunosuppressive agents did not change
over the study period, although the use of
topical agents increased (Po0.05).
Conclusion PPV appears to have a beneficial
effect on the clinical course of EPU in
selected cases. This may be mediated
by the physical clearance of inflammatory
debris, the anti-inflammatory effect of
replacing vitreous by aqueous humour, by a
reduction of CMO and/or the anatomical
correction of sight-threatening retinal
pathology.
Eye (2003) 17, 221–227. doi:10.1038/
sj.eye.6700299
Keywords: vitrectomy; uveitis; cystoid macular
oedema
Introduction
Endogenous posterior uveoretinitis (EPU)
encompasses the autoimmune inflammatory
syndromes of the posterior segment of the eye
associated with vitritis, choroiditis, retinal
vasculitis, cystoid macular oedema, and optic
nerve head oedema. EPU is characterised by an
exaggerated immune response leading to tissue
destruction, which may be localised to the eye
or comprise part of a systemic disease.
1,2
EPU responds to general inhibition of the
immune response with systemic steroids as well
as inhibitors of T-cell activation such as
cyclosporine A or FK506. The population of
autoreactive lymphocytes lodged in the vitreous
in chronic uveitis appears to be unable to exit
the eye and does not readily undergo
apoptosis.
3,4
It has been proposed that this
induces the collection of a ‘sump’ of
inflammatory cells lodged in the vitreous that
may be reactivated to cause an uveitic
exacerbation.
5
Pars plana vitrectomy (PPV) physically
removes the vitreous humour and in the case of
EPU, any inflammatory cells that might be
trapped in it. There is clinical evidence that PPV
has a beneficial effect on the clinical course of
chronic uveitis. There is a reported
improvement in visual acuity,
6,7
with a
reduction in the incidence of cystoid macular
oedema.
8,9
The number of uveitic exacerbations
is also reduced with fewer immunosuppressive
medications required.
10–13
PPV in uveitis can
also be a useful aid in diagnosis by providing a
view of the fundus and biopsy material for
laboratory analysis. This can reveal a diagnosis
in approximately 30–50% of cases where the
fundus cannot be otherwise visualised.
14
Potential complications of PPV in uveitis
include postoperative uveitic exacerbations,
retinal detachment, and the induction and
progression of lens opacities. Despite these
risks, PPV is indicated as part of the surgical
management of certain sequelae of EPU,
1
Moorfields Eye Hospital
London EC1V 2PD, UK
2
Queens Medical Centre
Nottingham NG7 2UH, UK
Correspondence:
DG Charteris
Moorfields Eye Hospital
London EC1V 2PD, UK
Tel/Fax: þ44 (0) 207 566
2285
E-mail: david.charteris@
moorfields.nhs.uk
Received: 12 February 2002
Accepted: 13 May 2002
Eye (2003) 17, 221–227
&2003 Nature Publishing Group All rights reserved 0950-222X/03 $25.00
www.nature.com/eye
CLINICAL STUDY

including persistent vitreous inflammatory debris,
vitreous haemorrhage, traction retinal detachments, and
epiretinal membranes.
15
Our aim was to assess the
anatomical and therapeutic effects of PPV for patients
with chronic EPU who required vitreous surgery for any
indication.
Patients and methods
This was a retrospective review of 41 eyes (19 right, 22
left) of 38 consecutive patients with EPU who underwent
PPV for any indication at Moorfields Eye Hospital,
London and Queens Medical Centre, Nottingham
between January 1992 and December 1997. The mean age
of the patients was 36.2 years (range 9–68), 20 were males
and 18 females. Six eyes had undergone a previous
cataract extraction, five with a posterior chamber
intraocular lens implant (IOL) and one was aphakic. Two
eyes had a history of glaucoma; at the time of operation
one was medically controlled and the other had
undergone a trabeculectomy but also required topical
medication.
The primary indication for the PPV was for media
opacities (including visually significant floaters) in 18
eyes, retinal detachment in eight eyes, epiretinal
membrane in nine eyes, and vitreous haemorrhage in six
eyes. The uveitic syndromes included 19 eyes (46%) with
intermediate uveitis, 13 eyes (32%) with panuveitis, and
nine (22%) with posterior uveitis. Of the nine eyes with
posterior uveitis, seven were idiopathic, one associated
with multiple sclerosis, and one with systemic
sarcoidosis.
Patients were examined preoperatively to confirm the
clinical diagnosis. At each visit the best-corrected Snellen
visual acuity, the results of slit-lamp biomicroscopy with
fundal examination and applanation tonometry were
recorded. Cystoid macular oedema was assessed both
clinically and by fluorescein angiography; since the
timing of angiography was not standardised, the clinical
findings were used for analysis. The vitreous was graded
using Nussenblatt’s classification from 0 to 4 þaccording
to the fundal structures visible on indirect
ophthalmoscopy through a dilated pupil with a 20-
dioptre lens.
16
For statistical analysis, visual acuity was
graded from 1 to 10 corresponding to the Snellen visual
acuity, ranging from 6/6 or better to no light perception.
The primary outcome of a significant change in vision
was designated as an improvement or loss of more than 2
Snellen lines.
The percentage of eyes that suffered an uveitic
exacerbation per month, and the number and type of
immunosuppressive agents taken by each patient per
month were recorded over the 12-month period pre- and
postoperatively. In this way, the effect of the PPV on the
average percentage of patients per month who had an
uveitic exacerbation, and the average number of
medications required per patient per month to control
the disease could be assessed. Immunosuppressive
agents were classed as topical, orbital, or systemic, and
the uveitic episodes were recorded anatomically as
anterior uveitis, intermediate uveitis, or posterior.
A standard three-port PPV was performed on all of the
eyes. Any further operative manoeuvres were performed
as clinically indicated. Lensectomy, IOL implantation,
epiretinal membrane peel, retinectomy, fluid/silicone oil
or gas exchange, scleral buckling, and choroidal biopsy
were performed according to the surgical indication. All
operations were performed or directly supervised by one
of the four surgeons. Preoperatively, patients were
commenced on systemic prednisolone 40 mg/day for 2
weeks if not already on systemic steroids. This was tailed
off over 4–8 weeks postoperatively. Where there was a
contraindication to systemic steroids, topical and/or
orbital steroids were increased in the immediate pre- and
postoperative periods.
The eyes were examined preoperatively and at regular
intervals for 12 months postoperatively. The clinical
information was retrieved from the patient case notes
and had been recorded by multiple observers over the
time period chosen for the study. Comparisons of
categorical data between subgroups of eyes were made
using the two-tailed Fisher’s exact test and between
numerical variables using the Mann–Whitney Utest.
Results
Peroperative
No major peroperative complications were recorded. A
posterior vitreous detachment (PVD) was present in
23/41 (56%) of eyes at the time of operation. A PVD
was induced peroperatively in the remainder by suction
at the edge of the optic disc in seven (17%) eyes and
by surgical delamination in 11 (27%) eyes.
Visual acuity
Overall, 25/41 (61%) of the eyes gained more than 2
Snellen lines by 6 months (Po0.001). This improvement
was maintained at 12 months (Figure 1). All subgroups,
whether analysed according to the indication for surgery
or uveitic syndrome, had statistically significant numbers
of eyes gaining more than 2 Snellen lines over this
time period and no eyes lost more than 2 Snellen lines
(Table 1). The number of eyes where the level of vision
was 6/24 or less was reduced from 38 to 14 (Po0.001),
and the number of eyes achieving a level of vision of 6/
12 or greater increased from 0 to 23 (Po0.001). The visual
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results for the various subgroups did not significantly
differ from the pooled results at any time point after the
PPV (Table 1).
Cystoid macular oedema
Cystoid macular oedema (CMO) was significantly
reduced after PPV from 18 (44%) of the eyes
preoperatively compared to 8 (19%) at 12 months
postoperatively (Po0.05) (Figure 1). There was a
postoperative reduction of CMO observed in all the
uveitic subgroups (Table 2). Resolution of CMO was not
associated with a significantly greater visual
improvement, with a gain of more than 2 Snellen lines
observed in eight of 11 eyes where CMO resolved and
four of seven eyes where it persisted (P40.1). In the eyes
with a pre-existing PVD, CMO was present in 9/23 (39%)
preoperatively and 5/23 (22%) at 12 months. Where the
vitreous was attached, CMO was present in 9/18 (50%)
eyes preoperatively and 3/18 (17%) at 12 months. The
presence or absence of a PVD did not affect the incidence
of CMO either pre- or postoperatively (P40.1).
Visually significant floaters
In 18 eyes, the clinical indication for a PPV was visually
significant vitreous debris in the absence of vitreous
haemorrhage. Lens/capsular opacities were present in
seven of these eyes, four with cataracts requiring
lensectomy with ciliary sulcus fixated IOL implantation
and three with significant posterior capsular
opacification requiring surgical capsulotomy combined
with an IOL exchange in one case.
The median grade of preoperative vitreous haze was 3
for the 18 eyes with visually symptomatic floaters. After
removal/absorption of postoperative intracavity
haemorrhage and debris, all eyes improved to grade 0 by
1 month. Symptoms of visually disturbing floaters were
relieved in all 18 eyes where this was the primary
indication for the PPV (Po0.001). Apart from two
transient recurrences of intermediate uveitis, the vitreous
cavity remained clear over 12 months follow-up in all
cases.
A gain of more than 2 Snellen lines was observed in 11
(61%) of these eyes at 12 months (Po0.001). The
remaining seven eyes retained their preoperative visual
acuity. The incidence of CMO did not significantly
reduce over the study period, from nine eyes
preoperatively to six eyes at 12 months (P40.1).
Of the 11 eyes with visually significant vitreous floaters
in the absence of lens opacity seven (64%) gained more
than 2 Snellen lines. This improvement was attained in
four of the seven (57%) eyes requiring surgery for
concomitant lens/capsular opacities. Removal of lens/
Figure 1 Percentage of eyes gaining more than 2 Snellen lines
and percentages of eyes with clinically detectable CMO against
time after PPV for chronic EPU.
Table 1 Number of eyes gaining more than 2 Snellen lines after PPV for chronic EPU according to subgroup
Number of eyes (%) gaining >2 lines of acuity after PPV
1 month 3 months 6 months 12 months
Uveitic group
Intermediate (19) 3 (16) 8 (42)* 12 (63)* 12 (63)*
Posterior (9) 5 (56)* 8 (89)* 7 (78)* 8 (89)*
Panuveitis (13) 2 (15) 6 (46)* 6 (46)* 5 (38)*
All eyes (41) 10 (24)* 22 (54)* 25 (61)* 25 (61)*
Indication for PPV
Floaters (18) 5 (28)* 10 (56)* 11 (61)* 11 (61)*
Retinal detachment (8) 0 (0) 3 (38) 4 (50)* 4 (50)*
Epiretinal membrane (9) 1 (11) 3 (56)* 6 (67)* 6 (67)*
Vitreous haemorrhage (6) 4 (67)* 4 (67)* 4 (67)* 4 (67)*
*Denotes statistical significance (Po0.05).
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capsular opacities did not significantly increase the
chance of gaining more than 2 Snellen lines (P40.1).
Retinal detachment
A retinal detachment (RD) was present in 12 eyes, seven
presented with tractional RD (TRD), four with combined
rhegmatogenous/traction RD (R/TRD), and one with a
rhegmatogenous RD (RRD). Four eyes had panuveitis
and five had posterior uveitis owing to retinal vasculitis.
Intermediate uveitis was present in the remaining three
eyes, including the single case of RRD. Overall, six (50%)
of these eyes gained more than 2 Snellen lines, the
remainder retained their preoperative visual acuity at 12
months, and this improvement was statistically
significant (Po0.01).
The indication for surgery in the eyes with TRD was
sudden loss of vision owing to vitreous haemorrhage in
four cases and a gradual loss of vision owing to macular
detachment in three cases. All seven eyes underwent a
PPV with delamination and laser. A further operation
with an encircling scleral buckle and silicone oil internal
tamponade was required in one eye for persistent retinal
traction; the oil was successfully removed at 6 months,
with a good anatomical result and a visual acuity of 6/18.
Six eyes gained more than 2 Snellen lines at 1 year, with
three attaining a final visual acuity of 6/12 or better. The
only eye that did not improve was known to have a
macular scar prior to surgery.
All four eyes with combined R/TRD underwent
PPV and surgical delamination. An encircling buckle was
employed in three eyes; two of these had silicone oil
and one C3F8 gas internal tamponade. Retinectomy with
silicone oil tamponade was performed in one eye.
A further delamination and silicone oil top-up procedure
was performed in one eye for residual RD. The
retina was successfully attached in all cases at 12 months,
although the silicone oil was not removed from any eye
and one eye became hypotonous (IOPo5 mmHg).
None of the eyes had either a preoperative visual
acuity of greater than counting fingers (CF) or a gain of
more than 2 Snellen lines postoperatively. The single eye
with an RRD had macular involvement and was treated
with a PPV, scleral buckling, and gas internal tamponade.
The retina was successfully reattached although the
visual acuity did not improve from CF.
Epiretinal membrane (ERM)
Metamorphopsia and reduced visual acuity as a result of
symptomatic ERM were present in nine eyes of nine
patients. The ERM were presumed to be secondary to the
ocular inflammatory process; five associated with
idiopathic panuveitis, two with pars planitis, and two
with posterior uveitis. A PPV and membrane peeling
procedure was performed in all cases, one eye required a
further membrane peel at 2 months postoperatively. A
gain of more than 2 lines of acuity at 1 year was noted in
six (67%) of the eyes (Po0.005), metamorphopsia was
subjectively reduced in all eyes, and none of the eyes
deteriorated. CMO was present preoperatively in five
eyes and was undetectable clinically in any eye at 1 year
(Po0.05).
Postoperative complications
Early complications (at less than 3 months) included one
eye that required a second membrane peel and one a
second delamination procedure. One eye developed an
RD from an entry site break, which was successfully
treated with cryopexy, scleral buckling, and a fluid/gas
exchange. One eye that had pre-existent glaucoma
Table 2 Number of eyes with clinical CMO after PPV for chronic EPU according to subgroup
Number of eyes (%) with clinical CMO after PPV
Preop 1 month 3 months 6 months 12 months
Uveitic group
Intermediate (19) 9 (22) 9 (22) 6 (15) 3 (7) 4 (10)
Posterior (9) 3 (7) 2 (5) 1 (2) 0 (0) 0 (0)
Panuveitis (13) 6 (15) 5 (12) 4 (10) 3 (7) 4 (10)
All eyes (41) 18 (44) 16 (39) 11 (27)* 6 (15)* 8 (20)*
Indication for PPV
Floaters (18) 9 (22) 9 (22) 6 (14) 4 (10) 6 (15)
Retinal detachment (8) 4 (10) 4 (10) 3 (7) 2 (5) 2 (5)
Epiretinal membrane (9) 5 (12) 3 (7) 2 (5) 0 (0)* 0 (0)*
Vitreous haemorrhage (6) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0)
*Denotes statistical significant change from preoperative value (Po0.05).
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managed medically required a trabeculectomy
augmented with mitomicin-C for a persistent intraocular
pressure rise.
Late complications occurring between 3 and 12 months
included one eye, which required a cataract extraction
and lens implant procedure and one eye, originally
treated for a combined TRD/RRD, which became
hypotonous. Three eyes developed pigmented macular
scars on the postoperative resolution of gross, chronic
CMO. Two of these eyes had tractional fibrovascular
membranes and one had an ERM removed. These three
eyes had a postoperative visual acuity of CF. Late
recurrence of CMO at 9–12 months occurred in two eyes,
which had final visual acuities of 6/60 and 6/36.
Immunosuppressive agents
There was no statistically significant difference in the
percentage of eyes per month that received systemic or
orbital floor immunosuppressive agents over the pre-
and postoperative 12-month periods. There was a
statistically significant increase in the use of topical
medication over the same period. The percentage of eyes
per month not requiring any immunosuppression did
not statistically differ over the two time periods (Table 3).
Disease activity
There was a significant decrease in episodes of
intermediate uveitis, posterior uveitis or panuveitis in
the postoperative 12-month period compared with the
same period preoperatively. The percentage of eyes per
month with anterior uveitis increased, although this did
not reach statistical significance (Table 3). There was a
significant increase in the percentage of eyes per month
that did not suffer any episodes of uveitis, from 70 to 84%
(P¼0.0012).
Discussion
In our study, PPV combined with appropriate adjunctive
surgical manoeuvres was safe and effective in the
management of the complications of chronic EPU. A gain
of more than 2 Snellen lines was observed in 61% of eyes,
with 75% attaining a final visual acuity of 6/24 or better
and 56% attaining 6/12 or better. This compares well
with other smaller series of the effects of PPV on the
course of chronic uveitis, where an improvement of more
than 2 Snellen lines was observed in 48–83% of eyes with
48–75% achieving 6/24 or better and 32–50% achieving
6/12 or better.
6,8,15
Visual improvement from the PPV is produced by a
number of factors. These include the physical clearance
of vitreous inflammatory debris, the reduction of
CMO, and the anatomical correction of sight-threatening
retinal abnormalities. Clearance of vitreous debris was a
major visual factor for the subgroups where PPV was
performed for visually significant vitreous floaters
and vitreous haemorrhage. Anatomical factors were
likely to be more important in the groups where
the PPV was performed for RD and ERM. The
likelihood of gaining more than 2 Snellen lines
did not significantly differ for any of the subgroups.
The RD group took longer to achieve a significant
improvement of acuity, and the overall acuity tended to
be worse with 50% achieving a final Snellen acuity of 6/
24 or better and 33% attaining 6/12 or
better. The group of four eyes with combined TRD/RRD
had the worst results; none of these eyes gained more
than 2 lines of visual acuity, all but one eye required long-
term silicone oil tamponade for residual peripheral RD.
Clinically detectable CMO decreased by 56% in a
fashion similar to other studies where a 40–50%
reduction was seen.
6,8,9
Clinical assessment of CMO in a
retrospective series is subject to the inaccuracies of the
objectivity of the examination and the difficulties of
fundal viewing through vitreous debris. Nevertheless,
the authors believe that the findings of this study
represent a true therapeutic effect of PPV and deserve
further investigation. It should be noted that prospective
studies retain the inherent difficulties of assessment of
CMO behind opacified media. Late postoperative
recurrences of CMO are recognised and occurred in two
eyes in our study.
17
The clinical resolution of CMO was
not statistically associated with visual improvement,
suggesting that other factors such as the clearance of
vitreous debris are responsible for the visual
Table 3 Comparison of immunosuppressive agent use and
disease activity in the pre- and postoperative 12-month periods
Immunosuppression Preoperative
12 months
(% per month)
Postoperative
12 months
(% per month)
Pvalue
Immunosuppressive agent use
None 30 30 0.4065
Systemic 42 41 0.5702
Orbital 1 0.6 0.2975
Topical 31 46 0.0349*
Uveitic exacerbations
Uveitic syndrome
Anterior 5 13 0.1437
Intermediate 9 1 0.0001*
Posterior 9 1 0.0003*
Panuveitis 7 0.4 0.0003*
*Statistically significant change in pre- and postoperative value (Po0.05).
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improvement seen in this series. It may be that earlier
surgical intervention is required to influence the visual
outcome associated with CMO resolution. Improvement
of CMO was not proven angiographically and in some
eyes may have persisted despite the clinical fundal
appearance. Although clinical resolution implies at least
a reduction in oedema, this may not have been sufficient
to allow a visual improvement. Furthermore, in some
cases, irreversible macular damage may have already
occurred as a result of the chronic CMO; this is illustrated
by the three eyes that developed pigmented macular
scars on resolution of the CMO.
ERM formation is a common cause of visual loss for
patients with EPU. Malinowski et al
18
found that 30% of
patients with pars planitis developed ERM of which 6.5%
were classified as severe. Dev et al
19
performed PPV with
membrane peeling on seven eyes with pars planitis and
ERM. A visual improvement of more than 2 Snellen lines
was attained in 71% of the eyes.
19
Our study has similar
findings, with six (67%) of nine eyes achieving the same
visual improvement.
An improvement in the course of uveitis after PPV has
been noted in other studies, and this improvement is
associated with a reduction in the use of medications to
control the disease process.
9–13
In our study, the number
and classes of medications did not change in the
postoperative period. This difference may be explained
by the increased use of immunosuppression in the
immediate postoperative period. With the use of
perioperative systemic steroids and careful observation
of the eyes in the immediate postoperative period, the
eyes in this series did not suffer from uncontrolled
uveitic episodes postoperatively. The episodes of anterior
uveitis seen postoperatively (Table 3) were generally
mild and easily controlled. It is possible that following
the reduction in postoperative medications, a significant
overall reduction in immunosuppression would be seen
in the second postoperative year.
There was a significant reduction in uveitic
exacerbations in the posterior segment postoperatively.
There is evidence that the population of autoreactive
lymphocytes lodged in the vitreous of eyes with
EPU is unable to exit the eye and does not appear to
undergo apoptosis. The reduction of inflammatory
relapses and CMO after PPV may be through the
removal of these cells, abolishing the abnormal Th1/Th2
balance of lymphocytes within the uveitic eye which
is proposed to mediate uveitic exacerbation and
remission.
10
The continued episodes of anterior
uveitis postoperatively may be caused by the stimulus of
surgical trauma, but could potentially also be because
of abnormalities in immune regulation in anterior
uveitis that are not affected by removal of vitreous
cells.
Another potential beneficial effect of PPV in uveitis is
the replacement of the vitreous with aqueous humour
which itself has anti-inflammatory effects. There is a
decreased level of cortisol binding globulin (TBG) in the
aqueous humour compared to the plasma, increasing the
free concentration of cortisol to enhance its
immunosuppressive effects.
20
Additionally, aqueous
humour constitutively expresses the anti-inflammatory
cytokines TGF-b, vasoactive intestinal peptide (VIP) and
a-melanocyte stimulating hormone (a-MSH).
21–23
Aqueous humour also inhibits complement fixation
through an unknown mechanism and promotes
apoptosis to allow the removal of inflammatory cells
after an inflammatory episode.
24,25
The results of this study add to the evidence that PPV
has a beneficial effect on the clinical course of EPU. We
did not evaluate subjective changes in vision following
surgery. Our clinical impression was that this often
improved even when the patient’s measured visual
acuity was not greatly increased.
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