|Year : 1987 | Volume
| Issue : 1 | Page : 2-3
Carotid artery insufficiency
Neuro Ophthalmologist, Aravind Eye Hospital; Madurai, India
Neuro Ophthalmologist, Aravind Eye Hospital; Madurai
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Natchiar G. Carotid artery insufficiency. Indian J Ophthalmol 1987;35:2-3
Carotid artery disease is an important cause of strokes and if the condition could be recognised before symptoms arise, medical or surgical treatment might be effective in reducing the mortality and morbidity from strokes.
Many patients with carotid -artery occlusive disease visit the ophthalmologists initially because of amaurosis fugax, field loss, or transient diplopia, which often represent premonitory symptoms of threatened stroke. Rarely a patient with chronic occlusive disease of the catotid artery can present with features of chronic ocular hypoxia like corneal edema, folds in Descemet's membrane, Rubeosis iridis, ocular hypotony, mid peripheral retinal hemorrhages, retinal venous dilatation and retinal neovascularization.
It then becomes the ophthalmologists responsibility to recognise the nature of these warning symptoms and direct the patient to a neurologist for proper investigation.
By its very nature evaluation of carotid artery stenosis by angiography carries with it undesirable attendant risks which motivated the development of various non-invasive techniques. So it is not surprising that many non-invasive screening tests for carotid disease like ophthalmodynamometry, ophthalmo plethysmography, pneumo plethysmography and doppler flow studies have all been devised.
Ironically the most durable and probably the most widely used adjunctive test for carotid insufficiency is the oldest. ophthalmodynamometry and its various modifications. The chief goal of testing is the comparison of the two eyes. A reproducible difference of 20% to 25% systolic or diastolic or both readings usually indicates significant carotid compromise on the affected side. The technique can detect stenotic lesions with an accuracy of up to 50% - 80%.
Ophthalmodynamometry despite its limitations has distinct value in the non-invasive corroboration of carotid occlusive disease. However certain reservations should be noted.
- It is well recognised that flow characteristics in the carotid are not altered until there is 70% - 90% stenosis.
- Collateral circulation may support flow and pressure in the ophthalmic artery in carotid stenosis or even complete occlusion
- Symptomatic carotid embolic disease may occur with minimal stenosis and the absence of Ophthalmodynamometry abnormality does not militate against carotid occlusive disease.
These above tests are done only when the patient presents with symptoms suggestive of vascular insufficiency. Examination of ocular pulse by a modified tonometer has been proposed as a screening method for carotid artery stenosis. The criteria used for abnormality of the ocular pulse were a difference of 0.5 mm Hg between two eyes and/or a pulse amplitude of less than 1.5 mm Hg for hypermetropia / emmetropia and 1.0 mm Hg for myopia. This can be done as a routine oat patient procedure for all above 40 years, for early detection of occlusive carotid arterial disease.
No reliable data that allow prediction of the exact incidence of cerebral infarction or permanent visual loss subsequent to amaurosis fugax are available. Marshall and Meadows analysed 80 patients with amaurosis fugax and found that 9 suffered retinal infarction and 5 sustained cerebral stroke during a follow up of 4 years.
Patients with these problems inspire ambivalence and indecision, specifically as to whether the ophthalmologist should promptly involve. a neuro surgeon in an all out assault on the carotid artery or refer the patient to a (timid) conservative neurologist, or merely explain to the patient about the problem and ask the patient to be informed if the problem recurs.
In any case it is likely that our ultimate hope of controlling this disease lies in a better understanding of the pathogenesis of athero sclerosis and early applications of effective medical or surgical prophylactic principles.