|Year : 1979 | Volume
| Issue : 4 | Page : 232-237
Natural history of branch vein blocks
HK Tewari, PK Khosla
R. P. Centre for Ophthalmic Sciences, AIIMS, New Delhi, India
H K Tewari
Asst. Prof. R. P. Centre for Ophthalmic Sciences. AIIMS., New Delhi
|How to cite this article:|
Tewari H K, Khosla P K. Natural history of branch vein blocks. Indian J Ophthalmol 1979;27:232-7
The fluorescein angiography has made it possible to study the microvascular changes delineating small vessel damage during the course of their natural history in addition to recording the site and size of the venous obstruction. The changes seen can indicate possible visual outcome and also the need of photocoagulation. Evaluation of photocoagulation done in consecutive cases must take natural history into consideration and hence only a truely randomized study can give, the final answer about the efficacy of photocoagulation. In this study, we have documented the natural history of branch vein blocks and have tried to indicate the age of lesion on the basis of changes occuring during course of time and also the indications for photocoagulation on the basis of fluorescein angiography.
| Methods and Materials|| |
50 cases of branch vein occlusion referred to medical ophthalmology clinic of Dr. Rajendra Prasad Centre for Ophthalmic Sciences are the subject of this study. Cases with major vascular disease like diabetic retinopathy or Eale's disease were not included in this study. All these patients had a detailed cardiovascular check up and were put only on supportive therapy. Detailed ophthalmic examination including visual acuity, intraocular pressure, colour fundus photography and fluorescein angiography at interval of 3 months, 6 months, 9 months and 1 year were done. The presentation of first visual symptom was related to the fluorescein angiographic picture so as to assess the approximate age of block.
For fluorescein angiography 3 cc of 20% sodium fluorescein was injected into the antecubital vein and photographs were taken with Zeiss (West Germany) camera using 400 ASA black and white film.
The following parameters were assessed from the angiograms:
(1) Size (order) of vessel occluded. On the basis of this the occlusions were classified into 3 main groups (1) Hemisphere blocks at the disc (II) Main branch blocks-superior temporal or inf°rior temporal (III) Small branch blocks-second order branches mainly in relation to macular area [Figure - 1]
(2) Site of obstruction.
(3) Extent of capillary nonperfusion area with special reference to macular area.
(4) Perifoveal arcade of capillaries.
(5) Leakage from main vein.
(6) Leakage in the macular area.
(7) Late changes in vein and artery.
(8) New vessel formation on disc or retina.
(9) Any other feature-as shift of block, changes in pre-retina.
| Observations and Comments|| |
[Table - 1] shows age and sex distribution in 50 cases of branch vein occlusion. The small branch blocks had better visual outcome than the other groups and most of them had final visual acuity better than 6/12. The interval between onset of these symptoms and the first examination i.e. presentation to us varied from 8 days to approximately 1 year. (Within 1 week-5 cases, upto 6 weeks-20 cases, upto 1.2 weeks-15 cases, upto 6 months-7 cases, upto 1 year-3 cases). The fluorescein angiographic findings are discussed as under:-
1. Size of vessel occluded-The majority (41) of the patients were in group II followed by those in Group 1 (5) and Group III (4).
2. Site of obstruction: In majority of cases the site of obstruction was at the arteriovenous crossing. Delayed filling and emptying of affected vein was a constant finding. In majority of cases (60%) significant narrowing of fluorescein column was seen. It was also demonstrable in cases where the block was at the level of optic disc. In some cases proximal portion of the vein did not show up and an alternative capillary channels was seen. Focal fluorescein leakage proximal to the site of block [Figure - 5] in venous phase of angiogram was only seen in fresh cases (never beyond 6 weeks), although not in all cases. We believe that if present, this is one of the important signs to indicate the age of block. There are histological evidences to suggest that swelling of the endothelium and deep venous wall initiate the process of venous block.
The extent of capillary non-perfusion in the macular area seem to have an important bearing on visual acuity. [Figure - 2],[Figure - 3]. Similarly the obliteration of the perifoveal arcade affect the visual acuity adversely. It was interesting that none of the cases which had complete arcade at 3 months deteriorated although deterioration was seen in those where arcade was seen to be complete at less than six weeks stage. Microvascular study was difficult in presence of retinal haemorrhages, so often seen for weeks after the blocks. The value of fluorescine photography in assessing visual prognosis is self evident. In cases where the patient shows a deterioration of vision in 3-6 months after the block and is accompained by loss of integrity of perifoveal arcade leading to macular oedema, should be taken up for treatment. The small branch blocks did much better [Figure - 4] than the hemisphere or main branch block from the visual prognosis point of view. This study shows that spontaneous improvement does take place in cases of branch vein blocks and there is a need for a randomized prospective study to determine the role of any treatment.
In fresh case it may not be obvious due to retinal oedema and haemorrhages but as these resolve, the leakage becomes obvious and suggests macular oedema. The patients with leakage in the macular area have a bad visual prognosis. It is interesting that majority of them had broken perifoveal arcade and large areas of capillary non-perfusion [Table - 2]. All these features seem to indicate poor visual prognosis.
If the collaterals are not well established the obstructed vein develops a halo sheathing followed by irregular narrowing. Clinically the artery accompanying the vein shows increased arteriosclerosis and at later stages may show a picture which may be mistaken for an arterial block. [Figure - 7] Thus it seems the arterial changes are secondary to venous obstruction-not the other way round.
In this series neovascularisation was observed both in the retina and at the disc in 3 cases. However, the time period when it was noticed was more than 6 months [Figure - 6]. These cases showed extensive areas of capillary nonperfusion.
The collaterals across the horizontal raphe were often seen time progressed. The ultimate outcome of a branch vein block depends on the efficiency of collaterals. Venous collaterals enlarge and become well established over the year and develop from the normal retina to the area of venous block to re-establish drainage. Effective establishment of collateral circulation seem to explain the observation that the patients with small branch blocks did much better than the hemisphere or main branch block. These vessels are to be differentiated from new vessels by the fact that they do not ordinarily leak fluorescein.
In course of time the areas of decompansation may be confined to small areas far distal to the original site of obstruction while rest to the area show varying degree of improvement in circulation [Figure - 5]. Thus the macular area became clear and patient regained vision of 6/9. Capillary microcaneurysms develop-invariably after 3 months. As haemorrhages and exudates disappear they become more and more prominent.
The patients presented to us from within 8 days upto 1 year and was probably due to the fact that symptoms of visual loss come at varied periods of time after block. The majority of patients (35 cases-70%) presented within a period of 6 weeks to 12 weeks.
In the present study majority (60%) of the patients had incomplete block at a/v crossing. In only 6% of our cases, proximal portion of the vein did not show up on fluorescein angiography which indicated complete obstruction, however.
The occluded vein develops sheathing and it may show a narrowed lumen or alternate dilated and narrow segments of collaterals are not well established. The artery accompanying the vein may show signs of increased arteriosclerosis even progressing to arterial closure. These signs are late and generally seen after one year.
| References|| |
|1.||Khosla, P.K., Sachdeva, R.P., Prakash, P. & Gahlot, D.K., 1971, Orient Arch. Ophthal. 10, 297. |
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6], [Figure - 7]
[Table - 1], [Table - 2]