ENDOSCOPY FOR ANTERIOR PROLIFERATIVE VITREORETINOPATHY (PVR)

Claude Boscher (Paris)

I. Introduction to endoscopic use in vitreoretinal surgery
A. History (Thorpe 1934, Norris1981, Koch 1990)
B. Clinical investigations (1994 - 2001)
1: using a fiber optics video transmission system probe, endolaser integrated
   (Endoptiks, Little Silver, New Jersey, USA)
2: in the following indications:
   -complications of cataract surgery (lens/IOL dislocation, IOL suturing,
    endophtalmitis, expulsive hemorrage, retinal detachment)
   -traumas
   -severe proliferative diabetic retinopathy and prevention of anterior     fibrovascular proliferation
   -anterior PVR
   -silicone oil ablation
   -treatment of primary rhegmatogenous retinal detachment with vitrectomy,
    without indentation
   -neovascular / refractory glaucoma
   -evaluation of vitrectomy machines

II. Endoscopy assisted viewing in the vitreous cavity
A. Endoscopy presents 3 specific properties:
1: viewing through non transparent media:
a) applicable in cases of pathological anterior segment
b) to observation of tissues, normal or pathological, either normally
    inaccessible (iris root, zonular system, posterior lens capsular surface
    and Wieger ligament, or difficult to visualize (ciliary processes, anterior
    part of the pars plana and of the vitreous base)
c) on 360°
d) in the phakic as well as in the aphakic eye
e) undistorted (no need for scleral indentation)
f) applicable to any peroperative unplanned incident precluding conventional
    viewing
2: approach of tissues visualized right in front of the endoscopic probe is
    tangential (sagital) (in addition to frontal, as through the microscope)
3: viewing can be panoramic (as through wide angle systems) but also
    extremely magnified (x 5 to x 20, compared to magnification through
    microscope)
B. Other specific characteristics
1: viewing is obtained immediately after introduction of the endoscopic probe
    inside the sclerotomy, without need for setting any additional system
2: switching from panoramic viewing to extremely hig magnification is
    obtained in a few seconds, by approaching closer to the target observed
3: specific training
a) requires a few tens of procedures
b) acquisition of orientation and manipulation of the probe
c) adaptation to video monitor control and cerebral development of a
    pseudostereopsis
d) no limitations to maneuvers as vitrectomy, endodiathermy or retinectomy
4: limitation in the current state of the technology : membrane bimanual
    dissection is impossible

III. Endoscopy assisted vitrectomy: rationale in anterior PVR
A. Anterior (zonular) Vitreous Base
1: plays a key role in the development of anterior PVR, hypotony and phtisis:
    scaffold for fibrovascular proliferation and reservoir for cell proliferation.
2: anatomy
a) composed of anterior vitreous cortex fibers, which run parallel to the
    anterior halph of the pars plana epithelium, to the ciliary processes, to
    the anterior and posterior zonular bundles, and to the posterior lens
    capsule near to the lens equator (Wieger ligament).
b) extremely close intrication of anterior vitreous cortex fibers, or tertiary
    vitreous, and of these structures, derives from their common embryologic
    origin, the ciliary epithelium .
B. Endoscopic observations in retinal detachment with anterior PVR High
    magnification and tangential endoscopic approach allow, even in the
    phakic eye, on 360°:
1: a unique evaluation of real anatomical depth and of various orientations
    of anterior vitreous base fibers and of their connections to adjacent
    structures
2: retrospective study
a) goal: to determine per operative endoscopic data of the anterior Vitreous
    Base common to cases with established anterior PVR
b) methods: retrospective review of 79 surgical videos for primary
    rhegmatogenous retinal detachment (31 eyes with some degree of
    anterior PVR at clinical preoperative examination, 48 eyes without),
    compared to 80 cases operated for macular surgery with presumably
    normal anterior Vitreous Base.
c) results
1° normal anterior vitreous cortex
2° seven per operative endoscopic criteria common to anterior PVR cases
    have been collected ( at least three of them associated )at the penetration
    of the probe from the sclerotomy inside the vitreous cavity
1) "en bloc" stiff anterior vitreous retraction
2) granulations inside the anterior part of the vitreous base (pigmented,
    more often white)
3) ciliary detachment during vitrectomy (using a peristaltic pump with low
    flow)
4) tractional anterior retinal surface hemorrages
5) anterior displacement with trend to vitreous / ciliary / retinal incarceration
    into the sclerotomy
6) "wrinkling" of posterior attachment of the vitreous base
7) failure to complete anterior retinal flattening under PFCL (though anterior
    vitrectomy seems achieved under panoramic viewing)
3° none of these criteria was observed in any of the cases operated for
    macular surgery
4° one of them could be found ,usually isolated, in as much as 80 %
    of cases of rhegmatogenous detachment without anterior PVR at
    clinical examination; various bias (reason for performing a vitrectomy,
    retrospective nature of the study )
C. Endoscopic observations of the delayed consequences of anterior
    PVR on the ciliary body: cyclitic mem-branes and hypotony
1: three possible clinical cases (aphakic / pseudophakic eyes)
a) hypotony, retina flat, cyclitic membrane
b) hypotony, cyclitic membrane AND PERSISTENT retinal detachment
    after multiple surgeries) (usually retraction of ILM)
c) hypotony, and primary retinal detachment lwith anterior PVR leading to
    cyclitic membrane (rare)
2: composition of the cyclitic membrane:
a) proliferations upon a scaffold of three different layers agglomerated at the
    surface of the ciliary processes: 1) residual anterior vitreous cortex fibers
    2) zonular fibers and capsular bag or posterior capsule (sometimes
    themselves totally stuck to the iris) 3) ciliary epithelium
b) continuing on a variable amount of surface of pars plana, and even of
    anterior retina (or anterior flap of a retinectomy)
c) thickness depends on amount of vitreous fibers, fibrin, blood left in place
d) cosequences : underlying aspect / condition of the ciliary processes
    variable, probably depending on severity / duration of "suffocating"
    process: elongation, discolouration, atrophy.

IV. Applications in anterior PVR
A. visualization and treatment of retinal detachment with established
    significant anterior PVR
1: Endoscopy assisted vitrectomy in anterior Vitreous Base with anterior
    PVR High magnification and tangential endoscopic approach allow,
    even in the phakic eye, on 360°:
a) control of penetration of surgical tools in case of anterior tissue
    displacements secondary to anterior PVR and / or ciliary detachment
b) hyaloido - lenticular dissection
c) deconnection of anterior vitreous base fibers from zonular system, ciliary
    epithelium and processes
d) deconnection of anterior from posterior attachment of vitreous base and
    to achieve close peeling of vitreous cortex in between b), c) and d): to
    treat / prevent vitreous base avulsion and anterior retinal displacement
e) identification, application of diathermy and dissection of neovascularized
    anterior proliferations
f) extremely tight vitreo retinal dissection (up to 0. 2 mm) (limited in fact by
    the shape of the vitrectomy probe tip and the distance between window
    and tip
g) thorough cleansing of sclerotomies
h) visualization / treatment / (prevention) of anterior reproliferations between
    sclerotomies and anterior tears, leading to anterior retinal / ciliary
    (re)detachment (even upon indentation, under silicone oil).
2: advantages
a ) "pushing" the peeling of the anterior vitreous base, thanks to endoscopic
    visualization, tangential approach, and high magnification : more
    achieved removal of the scaffold component of PVR
b) temporary conservation of the lens (will subsequently develop a cataract
    anyway): maintain anatomical barriers and limit per and post operative
    inflammation/complications .
3: discussion, limitations
a) temporary conservation of the lens might be unnecessary
b) no effect on biological components of anterior PVR
4: results biased (delay for surgery, primary or subsequent procedure(s) …)
5: future prospective: to combine evaluation of endoscopic viewing and
    therapeutical specific capacities with peroperative use of pharmacological
    agents.
B. visualization and treatment of the delayed consequences of anterior
    PVR on the ciliary body: cyclitic membranes and hypotony
1: endoscopy assisted maneuvers
a) dissection of the ciliary epithelium layer from the others; delicate
    (monomanual); necessitates sharp instruments b) dissection
    between iris pigmented epithelium layer and and capsular remnants
    sometimes impossible
2: results
a) hypotony, retina flat, cyclitic membrane: 3 eyes: pressure normalized
    at 9, vision acuity: 20/400, in two upon three eyes
b) hypotony, cyclitic membrane AND persistent retinal detachment :
    2 eyes : failure, pressure 2 and 4
c) hypotony, and primary retinal detachment lwith anterior PVR leading
    to cyclitic membrane : 1 eye, pressure normalized to 12, visual
    acuity inferior to 20 /400 .
C. Prevention of development of anterior PVR in cases at risk during
    primary vitrectomy
1: rationale
a) despite progresses in intrumentation and visualization, vitrectomy for
    anterior PVR fails, and / or secondary retinal tears, retinal detachment,
    and eventually anterior PVR develop after vitrectomy
b) a small amount of residual anterior vitreous, provided that it is still
    connected to undissected Wieger ligament, and/ or to sclerotomies
    and / or to retinal tears, is able to prevent successful retinal reattachment,
    or to provoke its redetachment (even upon buckles, and under silicone oil)
c) on the other hand, achieved anterior vitrectomy is unnecessary in many
    cases
d) current challenge: to determine which case will or will not need an
    achieved anterior vitrectomy during primary procedure .
2: current prospective study primary endoscopy assisted vitrectomy,
    internal tamponade and retinopexy limited to the tear(s), without buckling,
    without lensectomy, in primary rhegmatogenous retinal detachment

V. Conclusion
Endoscopy assisted vitrectomy of the anterior Vitreous Base provides additinal information on the pathogenesis and anatomical condition in anterior PVR, and explainations for failure of conventional surgery. It allows to treat some cases of hypotony post anterior PVR previously considered terminal. It might allow to step back the limits of treatment of retinal detachment with established anterior PVR, but it does not resolve the biological issues of PVR. By allowing a much closer and achieved anterior vitreous cortex peeling, endoscopy might improve the rate of primary success and be an efficient prevention of failures and complications of vitrectomy; cases at risk to develop anterior PVR after vitrectomy might be selected according to endoscopic peroperative criteria.
It certainly would be interesting to test it in conjunction with pharmacological adjuncts and more sophisticated vitrectomy machines.

References
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10) Boscher C. Endoscopy assisted vitrectomy for anterior PVR, oral
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11) Boscher C. Peroperative endoscopic evaluation of vitrectomy machines,
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