INVESTIGADORES
DORFMAN Damian
congresos y reuniones científicas
Título:
Study of Radial Optic Neurotomy Outcomes in Normal Rat Eyes
Autor/es:
DORFMAN D; CROXATTO JO; DE ZAVALÍA N; ROSENSTEIN RE; BELFORTE NA
Lugar:
Fort Lauderdale
Reunión:
Congreso; Pan-American Research Day; 2010
Institución organizadora:
Pan-American Association of Ophthalmology
Resumen:
Purpose
Radial optic
neurotomy (RON) consists in the surgical dissection of the lamina cribrosa
transvitreally via a radial incision on the nasal side of the optic nerve. RON
was proposed as a surgical treatment for central retinal vein occlusion (CRVO).
Although improvements in visual acuity by RON in patients with CRVO have been
confirmed by several investigators, it is still controversial whether the
incision of the scleral outlet is a reasonable or dangerous procedure. The use
of rodents allows experimentation with sufficient number of animals and could provide
a picture of both functional and morphological consequences of RON. Therefore,
the aim of the present report was to analyze RON outcomes in normal rat eyes.
Methods
Male Wistar rats
were subjected to RON in one eye, whereas the contralateral eye was subjected
to a sham procedure. RON was performed as follows: eyes were focused under a
binocular Colden surgical microscope with coaxial light and a scleral puncture,
using a 30-G needle, was made at 1 mm of the corneoscleral limbus and a cut was
performed in the edge of the neuro-retinal ring, cutting an equal part of optic
nerve and retina parapapillary, avoiding the central retinal vessels. The sham
operated eyes were submitted to a similar procedure, without the cutting step. After
surgery, the surgical outcomes were evaluated in terms of: IOP (assessed by a
TonoPen XL), flash electroretinograms(ERG, with a gold electrode), flash visual
evoked potential (VEPs, using skull-implanted electrodes) and consensual pupil
light reflex assessment, as well as optic nerve head morphology (examined by
light microscopy).
Results
A transient
decrease in scotopic ERG a- and b-wave amplitude was observed in eyes submitted
to RON, which was evident 24 h but not 3 or 7 days after surgery. No changes in
flash VEPs, IOP, and consensual pupil reflex were observed between sham and RON
operated eyes at 7-day post-surgery. Histologically,the optic nerve showed
circumscribed scarring at the site of the incision without significant damage
of adjacent nerve fibers.
Conclusions
These results
support that minor histological alterations and transient functional changes
were provoked by RON in normal rat eyes.