|Year : 1977 | Volume
| Issue : 3 | Page : 17-19
Course of the nerve fibres in the temporal half of the retina
DN Gangwar, IS Jain, SP Dhir
Postgraduate Institute of Medical Education and Research, Chandigarh, India
D N Gangwar
Postgraduate Institute of Medical Education and Research, Chandigarh
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Gangwar D N, Jain I S, Dhir S P. Course of the nerve fibres in the temporal half of the retina. Indian J Ophthalmol 1977;25:17-9
|How to cite this URL:|
Gangwar D N, Jain I S, Dhir S P. Course of the nerve fibres in the temporal half of the retina. Indian J Ophthalmol [serial online] 1977 [cited 2020 Aug 4];25:17-9. Available from: http://www.ijo.in/text.asp?1977/25/3/17/31263
Examination of opaque nerve fibres provides a unique opportunity to study the topography of nerve fibres in the retina.
The nerve fibre layer consists of the axons of the ganglion cells which pass through the lamina cribrosa to form the optic nerve. The nerve fibres are arranged in bundles which run parallel to the surface of the retina. They are not normally visible by ophthalmoscope, however, when the myelin sheath is continued beyond the optic disc, they can be seen as opaque nerve fibres. The direction of fraying of these opaque nerve fibres shows their course and reveals the pattern in their distribution.
The basic pattern of arrangement of the nerve fibres in the retina has been well studied by field defect patterns, histological examination as well as by study of opaque nerve fibres. This basic pattern is demonstrated in [Figure - 1]. by Harrington Much emphasis has been devoted to the study of arrangement of fibres in the macular area, only little information is available of their arrangement in the peripheral part of retina. We present two cases of opaque nerve fibres which are of special interest as they show opaque nerve fibres in the central and peripheral regions of the retina.
Case No. 1:
On routine examination of the fundus of young adult male opaque nerve fibres were found in the right eye. The distribution of the opaque nerve fibres as seen in funds is shown [Figure - 2]. The arrangement of fibres at the horizontal raphe is of special interest [Figure - 3]. It is seen that the temporal axons take a curved course. This curve become increasingly greater in the macular region. In the region of the horizontal raphe the courses of axons are of three types. Immediately, adjacent to fovea the fibres are vertical. Further temporal they become oblique. This obliquity is further accentuated into a curve. Thus the fibres arising from the temporal part of raphe describe a double S shaped curve in their course towards the optic disc viz. first curve with a concavity towards the periphery (C-I) and second curve with concavity towards the macula (C-2). This is shown diagramatically in [Figure - 4].
Case No. 2:
This adult male patient seen with unrelated complaints showed opaque nerve fibres in the inferotemporal quadrant to the right eye [Figure - 5] in the region of equator and beyond. The direction of fraying of these opaque nerve fibres in this lower part described an unusal curve with concavity towards six O'clock position [Figure - 6]. The conjoint effect of the two cases is shown diagramatically in [Figure - 4].
| Comments|| |
All the fibres in the nerve fibre layer converge towards the optic disc. Those from the nasal side reach it without interruption. Those from temporal side do not pass through the macula but have to go around it. The fibres above the horizontal meridian pass above the macula and those below it pass under it. Thus, we find to the lateral side of the macula a sort of raphe from which the nerve fibres arise in a pennate manner. The course of the temporal axons is curved, and becomes increasingly greater in the macular region. In the region of the raphe the courses of the axons are of three types-vertical, oblique and triangular. The vertical axons are more numerous. Posner and Schlossman have suggested existence of nasal arcuate fibres in temporal juxta papillary region. Although this arrangement explains some of the field defects corresponding to this area, the existence of these fibres has been questioned on histological basis.
Case No. 1 demonstrates that the fibres arising from the temporal part of the raphe' describe a double S shaped curve. First the concavity is towards the periphery (C-1) and the second concavity is towards the macula (C-2) [Figure - 4]. Further, as demostrated by case No. 2 the first curve present in the central fibres is continued to the peripheral fibres in the temporal half of the retina. It appears that fibres arising even at the equator and beyond do not have a straight course to the optic disc but rather have an initial curved course with concavity towards the periphery and later a reverse curve with concavity towards the macula. It appears that all the temporal fibres arising from the raphe and beyond describe an S shaped course and not a single curve with concavity towards the macula.
| Summary|| |
Two cases of opaque nerve fibres of the retina showing the direction of fraying in the central and peripheral part of the retina have been presented. The temporal fibres arising from the raphe and beyond described an unusual S shaped course and not a single curve with concavity towards the macula has been reported in the literature.
| References|| |
Greef, 1900 Quoted from Wolff, E. The Anatomy of the Eye and orbit. Fourth Ed. 107 H.K. Lewis and Co. Ltd. London.
Harrington, D.O., 1976. A text Book and Atlas of Clinical Perimetery, The C.V. Mosby Company, Saint Louis 68.
Hogan, M.J., Alvarado, J.A., Weddell, J.E. 1971. Histology of the human eye, 536. W.B. Saunders Co., London.
Posner, A.. and Schlossman, A., 1948. Arch. Ophth.
Vrabec: 1960., Amar. J. Ophth.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]