What have we learnt from lamina cribrosa puncture for CRVO?
Hugo Quiroz-Mercado (Mexico City)
Central retinal vein
occlusion (CRVO) is a pathology that has not a definitive treatment. Several
therapeutic alternatives have been proposed either to alleviate sequela
or as a definitive treatment.
Among them are: intravitreal trimacinolene (IVT), vitrectomy with IVT,
vitrectomy without IVT, vitrectomy with induction of retino-choroidal
shunts, vitrectomy with radial optic neurotomy (RON) and vitrectomy with
lamian cribrosa puncture (LCP). In a referral center in Mexico City (Asociacion
para Evitar la Ceguera en Mexico) we have performed some of this techniques.
In the beginning (1998) we reported our first experience with vitrectomy
and retino-choroidal shunts; although with marginal improvement in visual
acuity, patients decreased intra-retinal hemorrhage and macular edema
after two weeks of treatment. In this patients vitrectomy was performed
along with posterior hyloid removal and periocular steroids at the end
of the procedures. It is important to mention that all of our cases had
ischemic CRVO. To evaluate solo vitrectomy (without any other maneuver)
in ischemic CRVO we treated a group of patients in which vitrectomy and
posterior hyalid removal was performed. The final results in the group
of patients with retino-choroidal shunts and solo vitrectomy were not
quite different. Based on this results we speculated that patients may
improve mainly by vitrectomy and posterior hyaloid removal. Vitrectomy
may improve by 3 different effects: increasing oxygen concentration of
intravitreal cavity, removing angiogenic factors and removing scaffold
for neovascularization. Although IVT has gain popularity on the treatment
of CRVO we have observed that vitrectomy plus IVT has a more durable effect
without less vitreous hemorrhage. When RON was introduced as an alternative
treatment we performed a group of patients in which we observed the same
effect of eyes treated with solo vitrectomy and vitrectomy with retino-choroidal
anastomosis but interesting was that most of the patients decreased intraocular
pressure (IOP), mean preoperative IOP was 16.33 mm Hg (range 12-21) and
after a 6 months of follow-up, the mean postoperative IOP was 11 (range
8-12). At the same time we observed in a video of LCP from Dr. D’Amico
the following: he performed a complete vitrectomy, and two punctures in
the lamina cribrosa, at the second puncture he damaged the central retina
vein with accumulation of blood in the vitreous cavity that was spontaneously
drained through the optic nerve where LCP was performed. These observations
gave us two the following observations aqueous humor or any other fluid
in the vitreous cavity drain faster when the vitreous has been removed.
Aqueous humor may drain through the optic nerve. Optic nerve damage produced
by LCP and RON is not big enough to produce important reduction on visual
acuity. In dog eyes we performed vitrectomy with a solution stained with
fluorescein, after vitrectomy a LCP was performed. When the optic nerve
was cut 3 mm away from the eye we observed that BSS stained with fluorescein
was draining from the optic nerve. In two patients with absolute glaucoma
we performed parsplana vitrectomy and lamina cribosa puncture to decrease
IOP. On both eyes we observed considerable decrease of IOP, but it was
not permanent. At the present time we are exploring a new indication of
vitrectomy: to drain aqueous humor by the creation of a by-pas through
the optic nerve to drain either to subarachnoidal space, intraorbital
cavity or venous system of the orbit. Different models of canulas and
valves are under research.