Radial Optic Neurotomy in Central Retinal Vein Occlusion
We read with great interest the article entitled 'Role of early radial optic neurotomy in CRVO'.1 We have the following observations to make:
- Among the inclusion criteria authors have said cases with capillary non perfusion as seen by angiography were excluded. Patients studied by them are of duration between 15 to 60 days. Retina, especially the posterior pole is largely covered by haemorrhages in recent onset cases. Any judgement of capillary perfusion or non perfusion by angiography in presence of haemorrhages cannot be accurate because of blocked fluorescence.
- Authors have stated that brushing the retinal surface with soft tipped cannula resulted in passive aspiration of superficial retinal haemorrhages to some extent. We would like to point out that superficial retinal haemorrhages are intra retinal collections of blood and cannot be aspirated unless a retinal injury is caused. Preretinal deposits of blood would clear with passive aspiration and these should not be mistaken as superficial retinal haemorrhages. Attempts at aspirating intra retinal haemorrhages with passive suction do show a movement of these haemorrhages in line with aspirating port, but these do not get aspirated through intact retinal tissue, one has to have a partial thickness break in retina for this blood to be aspirated out. On relieving the suction some temporary displacement may be seen in the position of haemorrhages.
- Authors have mentioned injecting three to four cc of liquid perfluorocarbon (PFCL) over the posterior pole in order to mechanically squeeze the oedematous fluid. Firstly oedematous fluid is tissue fluid and cannot be drained away or squeezed out like subretinal fluid with heavy PFCL liquid. Secondly even if we believe that it will do so; 3 to 4 ml of PFCL will reach upto equator, a little short of ora serrata and the entire retina will be pressed equally, therefore any movement of fluid is unlikely with the given technique by the authors.
- In the conclusion the authors have mentioned multiple mechanisms which help these patients such as effect of cuts in the optic nerve, relief of macular oedema by vitrectomy (which is a well established observation) and also the debatable value of passive aspiration of retinal haemorrhages and squeezing effect of PFCL. To our mind and observation a vitrectomy procedure will relieve macular oedema of any origin to a varying degree.
True value of radial optic neurotomy can be established only if cuts are given in the optic nerve without doing a vitrectomy procedure.
© 2005 Indian Journal of Ophthalmology | Published by Wolters Kluwer – Medknow
1. Nagpal M, Nagpal K, Bhatt C, Nagpal PN. Role of early radial optic neurotomy in central retinal vein occlusion Indian J Ophthalmol. 2005;53:105–8