I hypothesize that due to inherent temporal tilt of the disc the temporal nerve fibers are severed earlier therefore the central vessels are shifted nasally. Analogy: if the roots of a tree were cut from one side the tree would shift to opposite side. Nasal shifting of central vessels also supports the hypothesis that nerve fibers are being severed, not atrophied in glaucoma. Looking forward for feedback.
Hi,
Nasalization occurs as retinal blood vessels shift nasally in cases of progressive glaucoma; this is attributed to deterioration of adjacent nerve fiber tissue (the retinal nerve fiber layer contains the retinal blood vessels). Furthermore, this shift could afflict adjacent neural tissue. The fact that hypodense areas, also known as holes, were reportedly observed prior to actual shifting of the vessels should prompt us to think that focal/localized loss of the neural tissue can bring with it nasalization.
For more information, please consider the following work:
Varma R, Spaeth GL, Hanau C, Steinmann WC, Feldman RM. Positional changes in the vasculature of the optic disk in glaucoma. American journal of ophthalmology. 1987;104(5):457-64.
Amrit, thank you for your feedback. Literature is full of thinning of RNFL and neural loss occurring in glaucoma but no body ever mentions what kind of loss we are talking about as neural loss may be due to several things. Just saying neural loss is not enough, we have to be very specific about the kind of damage occurring to the individual nerve fibers in glaucoma. Are the nerve fibers being shrunk in size or atrophied or sliced or broken or reduced in number or anything else? Answer may give the reason for nasal shifting of vessels and also solve the mystery of glaucoma. What is your opinion as to kind of damage leading to neural loss or thinning of RNFL in glaucoma? Many thanks.
In glaucoma the first changes are seen at the level of lamina cribrosa which are seen clinically as nerve fibre layer defects. Some of the researchers have tried to image the optic nerve fibres within the LC and have detected LC defects on OCT in Glaucoma patients. Optic nerve fibres undergo apoptosis secondary to ischemic, mechanical or excitotoxic insult or a combination of these. Apoptosis of these fibres leads to atrophy of the nerve fibres leading to shift of disc vessels to the peripheral part of the disc. This is seen clinically as nasal shift of the vessels. You may like to view my earlier question on NTG in the same forum and provide your valuable input.
Dear Puneet, thank you for your reply. We always have to remember that in glaucoma the nerve fibers are always being destroyed in an orderly fashion starting with the peripheral fibers and ending with the central. In addition there are arcuate field defects in the early stages of glaucoma. These features are hallmark of glaucoma which, ironically, researchers have never addressed in bringing forward their theories of glaucoma.
It is easy to say that optic nerve fibers undergo apoptosis secondary to ischemia, mechanical or excitotoxic insult but do these also explain the orderly destruction of nerve fibers in glaucoma? Do these also explain the production of arcuate field in the early stages of glaucoma? Do these also explain the histology of end-stage glaucoma disc- an empty crater totally devoid of nerve fibers?
In my opinion none of the prevailing theories such as neurodegeneration, apoptosis. ischemia,or direct role of IOP or any other could explain the orderly destruction of nerve fibers in glaucoma. In fact, there is no pathology which acting directly on the nerve fibers could result in their orderly destruction. It has to be some indirect mechanism which is causing the orderly destruction of nerve fibers even though that indirect mechanism may have resulted from the direct effect of raised IOP on some very important tissue of the disc. This indirect mechanism is the paradigm shift in glaucoma. Humbly, unless we would change the present paradigm and address the issue of orderly destruction of nerve fibers in glaucoma in glaucoma I see no hope of finding the true pathogenesis of glaucoma.
www. glaucomaparadigmshift.com
Later this year I expect to publish images of the reversibility of nasal shift of the central artery and vein of the retina at their point of emergence from the Optic nerve, the level of which changes as the condition is seen to be a reversible demyelinating disease, before the stage of arcuate scotoma development. It was the acquisition of the first digital electronic fundus camera to come to the UK in April 1998 for the purpose of investigating this specific phenomenon, that led instead, to the initial discovery of CardioRetinometry® and the reversibility of arterial disease. This was entirely due, according to hundreds of contact lens wearing patients, to the coincidental and serendipitous urging on them in the clinic, of the advantage of reliable ability to wear their lenses gained by accepting supplementary sodium ascorbate dispensed as pure powder in 200 gram pots specifically for the prevention of opportunistic contact lens related eye infections. Subsequently a third discovery was made. This is that the condition of contact lens related supposedly "Dry Eye" is not "Dry Eye" at all. But that will be the subject of yet another paper. Now teaching physicians for the two year post graduate Doctorate in CardioRetinometry to save them from the heart attacks they are unable to prevent in their patients and themselves, is a priority.
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