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| ARTICLES |
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| Year : 1955 | Volume
: 3
| Issue : 2 | Page : 34-36 |
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Some causes of disfunction of vision
K Lindner
,
Correspondence Address:
K Lindner
,
 Source of Support: None, Conflict of Interest: None  | Check |
How to cite this article:
Lindner K. Some causes of disfunction of vision. Indian J Ophthalmol 1955;3:34-6 |
We shall start our discussion with disfunctions of minor importance. What is the cause of enlargement of the blind spot in cases of chronic glaucoma ? Why and how is the blind spot enlarged in cases of choked disc ?
In chronic glaucoma the enlargement of the blind spot must be due to the excavation of the optic disc. The optic nerve fibres are surrounded up to the lamina cribrosa by medullary sheaths. Therefore the fibres are fixed on this place. On the other side, the fibres end in the ganglion cells of the retina and are fixed there, too. It is evident that the shorter fibres which end in the retina around the disc cannot stand the necessary elongation and must rupture. Longer fibres on the other hand undergo this stretching more readily but not the very short ones.
The enlargement of the blind spot in choked disc seems to be of a quite different nature. By the swelling of the papilla the retina is pushed away from the optical channel, therefore the blind spot must become larger. However when the condition of the choked disc improves the blind spot diminishes in size but does not become normal again. Here for the same reason some nerve fibres inserted in the retina around the disc rupture when the retina is pushed away by the swelling of the disc. They cannot stand the stretching. Inspite of the difference of their nature the cause of the final state of enlargement of the blind spot is in both conditions the same.
| Retinopathies | |  |
Now we shall discuss the far more important problems of the different retinopathies. What are the causes of disfunction and even blindness in these diseases ? To start this important problem we have first to recall the way in which the tissue is nourished.
The blood supplies the tissue with the necessary nutrition but only by way of diffusion. Diffusible liquids cross the normal walls of the arterial part of the capillaries by help of the blood pressure while the venous part of the capillaries resorbs the used liquids with help of the colloid osmotic resorptive power. This exchange of liquids is a continuous one. Normally only traces of proteins pass through the capillaries into the tissue. We have the best example for this fact in the way in which the cones and rods are nourished inspite of their need of intense metabolism. The network of the chorio-capillaries nourishes the cones and rods through the lamina vitrea of the choroid and through the layer of the pigment cells. On the other side the layer of cones and rods are separated from the inner layers of the retina and their blood supply by the lamina limitans externa. The cones and rods are a very delicate tissue which would suffer under the influence of proteins, therefore they are exposed to diffusible liquids only. However this nutrition must be a continuous one just as well as the nutrition of the nerve cells in the inner layers of the retina. Blocking of the central retinal artery results instantaneously in blindness.
The nerve fibres, too, need continuous nutrition. Pressure on the optic nerve stops its function. We know that the propagation of a nervous impulse along a nerve fibre is not performed by a kind of electrical current but by a chemical process which needs continual nutrition. Pressure on a nerve fibre would not stop the electrical current. One of the most striking examples that pressure on the optic nerve stops its function is seen in cases of cysts of the hypophysis. When Hirsch operated those cases on our clinic in Vienna with his transnasal method, it was spectacular how instantaneously vision returned in some cases and how the field of vision suddenly became improved. Nutrition returned, function returned, if the pressure was not of too long standing.
This knowledge regarding the necessity of nutrition for nervous elements, we will now apply to other ophthalmological problems.
The main treatment of thrombosis of the central vein is complete rest of function of both eyes. Dark goggles, no reading, no writing, no cinema, and in addition no strain of the body whatsoever. Why is this so important? In this disease the walls of the blood vessels become abnormally nourished and therefore become permeable to blood and blood serum which enters the tissue. The more the proteins and blood enter the tissue spaces, the more difficult becomes resorption. If those patients continue to use their good eye, the diseased eye works in the same way and more blood and exudate will pour out from the altered vessels and the absorption becomes more and more difficult. With lack of nutrition function goes down. This is the reason why thrombosis of the central vein in poor people so often results in total blindness and additionally in absolute glaucoma. Poor people cannot afford to stop their work and often do not understand our advice whereas intelligent patients of the well-to-do class understand us and are able to follow strictly the hygiene we prescribe.
Another disease which has to be treated with absolute rest of both eyes is macular hemorrhage. I remember a high myopic girl with macular hemorrhage. She regained her former vision by strictly avoiding any kind of eye-work and corporal strain. After about two years, a macular hemorrhage developed a second time and again after a few months the blood was resorbed and the former vision returned.
Another disease which necessitates absolute eye rest and avoidance of corporal strain is retinopathy angiospastica. Here again the nutrition of the retina is involved. More exudate and more blood, less nutrition. This condition ends so often in blindness or nearly so. We have always great difficulties in prescribing absolute rest of both eyes because there is no pain connected with these morbid changes of the retinal tissue. Retina belongs to the central nervous system therefore there is no pain. Often one eye has lost central vision but the patient continues to use his other eye where the macula accidentally was spared and so will lose the central vision of the other eye.
The same holds true for the retinopathies of diabetic origin. We have here the same difficulties with our patients who do not feel any pain and therefore continue their daily work, often only with help of stronger spectacles. If we have occasion to examine histological slides of these retina we will see that the nervous elements have to a great extent disappeared, not by action of any poison, but by lack of nutrition.
Cases of retinochoroiditis are altogether different. Here we have a circumscribed focus; hyperemia would rather help to cure this infectious inflammation, Here we are not afraid if the patient uses his eyes.
I have seen in India so many cases who have become blind or nearly so by Eale's disease. In our own country I hardly remember a case that has become totally blind by this disease. It is compulsory for a case of Eale's disease to avoid any kind of eye work or corporal strain especially shortly after a hemorrhage has taken place. The danger of this disease is not a direct one. One vessel bleeds but the retina itself remains normal behind the hemorrhage which spreads out between detached vitreous and retina. If the blood is resorbed, normal vision returns. However if these hemorrhages take, place repeatedly they will not resorb as the first ones. An inflammatory process develops ending with connective tissue which shrinks and by this may cause retinal detachment which we cannot cure in most instances. The danger of repeated hemorrhages will be diminished by strict hygiene of eyework of both eyes and by avoiding strain of the body. The patients in our country can be kept for longer periods in hospitals and have a better opportunity to care for their health and eyesight by the help of the insurance system.
Patients with degenerative changes in their retina, too, should be kept away from continual eyework although in these cases the beneficial influence of eye rest is not so evident.
To sum up we can say: In all kinds of diseases of the retina connected with circulatory disorders disrupting the normal nutrition of the retina or in cases of repeated hemorrhages of retinal vessels (Eale's disease) absolute rest of both eyes is the most important part of treatment. It is far more important than any medication given. It is peculiar that no textbook except my own calls attention to this side of medical care.
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