MANAGEMENT OF AION

As discussed above, AION is primarily of two types: (1) arteritic AION and (2) non-arteritic AION. Once the diagnosis of AION is made, in the management of AION, the first, most important step in all patients aged 55 and over is to rule out giant cell arteritis immediately - because that is a prime ophthalmic emergency, since patients with giant cell arteritis are in danger of bilateral total blindness. Blindness is almost always preventable with aggressive treatment..^{23,26,30,34,48,55} Naturally the question arises as how to differentiate arteritic AION due to giant cell arteritis from non-arteritic AION to prevent this tragedy. This is discussed in detail elsewhere.^23,30,49,55 Very briefly, the following parameters are highly suggestive of arteritic AION:^23,55

1. SYSTEMIC MANIFESTATIONS OF GIANT CELL ARTERITIS: The patient may complain of weight loss, malaise, "flu"-like symptoms, fever of unknown origin, anemia, polymyalgia, pain on chewing food (jaw-claudication), neck pain, headache and vague ill-health.^26,46,55 In our recent study, jaw claudication and neck pain emerged as the symptoms with the highest odds of being associated with giant cell arteritis.⁴⁶ However, among the giant cell arteritis patients who presented with visual loss, we found 21% of them perfectly fit and healthy, without any systemic symptoms at all, and presenting only with visual loss - these belong to the occult variety of giant cell arteritis⁴⁹. Thus, contrary to the popular belief, every patient with giant cell arteritis does not have systemic symptoms.
2. VISUAL SYMPTOMS: If a patient with AION gives a history of transient blurring or loss of vision (amaurosis fugax) preceding the permanent visual loss, that is highly suggestive of arteritic AION.^23,48,55 It is extremely rare in non-arteritic AION.
3. HEMATOLOGIC ABNORMALITIES: Our studies^46,55 have shown that the following three hematologic tests are key for the diagnosis of giant cell arteritis.
1. Erythrocyte sedimentation rate (ESR): A high ESR is traditionally emphasized as the sine qua non for the diagnosis of giant cell arteritis. It is also well-established that estimation of ESR is an important test in diagnosis of giant cell arteritis. In our study of patients with positive temporal artery biopsy for giant cell arteritis, it varied between 4 and 140 mm/hr (Westergren) (median 87.5 mm). We also evaluated ESR in 749 normal persons, and their ESR ranged from 1-59 mm/hr (median 11 mm). We found that ESR levels increase with age and are also higher in women than in men. In the literature highly variable numbers are given for the normal values: most laboratories described it as <10 mm/hr in men and <20 mm/hr in women; Miller et al.⁶¹ put forward a formula to calculate the normal ESR: in men age divided by 2 and in women age+10 divided by two. Our study suggested that a useful cutoff criterion for normal ESR is <30 mm/hr in men and <35 mm/hr in women, with a sensitivity and specificity of 92%.
   With the ESR values in our study varying between 4 and 140 mm/hr in giant cell arteritis patients and 1 and 59 mm/hr in normal persons, there is an overlap in lower levels of ESR between the two groups. Thus, the most important fact to remember is that a so-called “normal” ESR does not rule out giant cell arteritis; we have had patients with as low as 4 - 5 mm Westergren ESR with giant cell arteritis confirmed by temporal artery biopsy.³¹ Giant cell arteritis is missed in a number of patients simply because of the universal misconception that every patient with giant cell arteritis must have a high ESR.
2. C-Reactive protein (CRP): Our studies indicate that estimation of CRP (an acute phase plasma protein of hepatic origin) is a highly reliable, reproducible and rapid test.⁴⁶ CRP reaches abnormal levels within 4-6 hours and can increase up to 1,000 times, and also shows a much more rapid response to treatment than the ESR. Unlike ESR, it is not influenced by age, sex or hematologic factors. It generally runs parallel with the ESR; however, in some cases, CRP is not elevated when ESR is. This dichotomy between the two tests is very helpful when ESR is elevated due to conditions unrelated to giant cell arteritis. Normal value is <0.5 mg/dl in our laboratory. In our study, in giant cell arteritis patients it varied between 0.5 and 34.7 (median 4.35) mg/dl, and in the normal controls it was <0.5 to 3.3 (median <0.5) mg/dl.⁴⁶ The sensitivity and specificity of CRP in detecting giant cell arteritis was 100% and 79-83% respectively. CRP is a very useful test.
3. Thrombocytosis: In our study⁵⁵ of biopsy proven giant cell arteritis patients, 60% had thrombocytosis (defined as a serum platelet count >400 X10³/µl) and that was significantly more prevalent in giant cell arteritis patients than in the normal control population. Sensitivity and specificity of thrombocytosis for diagnosis of giant cell arteritis was 60.4% and 97.5% respectively. There was no difference in the prevalence of thrombocytosis in giant cell arteritis patients with and without visual loss, as well as among those with and without systemic symptoms of giant cell arteritis. There was a significantly (p<0.0001) higher prevalence of thrombocytosis in patients with giant cell arteritis and arteritic AION than in those with non-arteritic AION.
4. Other hematologic tests: In addition to these, other hematologic tests can also be helpful. Anemia is a well-known finding in giant cell arteritis patients. Our recent study⁵⁵ suggests that evaluation of white blood cell count and hemoglobin and hematocrit levels provides additional useful information, because giant cell arteritis patients have significantly higher white blood cell counts and lower hemoglobin and hematocrit levels than those without giant cell arteritis.
   
   In conclusion, the combined information provided by ESR, CRP, platelet and white blood cell count and hemoglobin and hematocrit levels is highly useful in diagnosis of giant cell arteritis, although no one test individually, is 100% sensitive and specific. In view of this, we recommend doing complete blood count, in addition to ESR and CRP estimation.
4. EARLY, MASSIVE VISUAL LOSS: If from the very start the visual acuity is reduced to no or bare light perception or hand motion, this is highly suggestive of arteritic AION.^23,45,48 However, in our series, 20% of eyes with arteritic AION had 20/40 (6/12) or better vision.⁴⁸
5. CHALKY WHITE SWOLLEN OPTIC DISC: In 69% of the cases of arteritic AION, the swollen disc has a chalky white appearance (Fig. 6).^9,11,48 It is almost diagnostic of this condition. In other arteritic AION eyes, however, the disc swelling appears no different from that in non-arteritic AION (Figs. 4, 5-B).
6. AION ASSOCIATED WITH CILIORETINAL ARTERY OCCLUSION: If an eye with fresh AION has optic disc swelling and associated cilioretinal artery occlusion, that is almost diagnostic of arteritic AION, because both are manifestations of posterior ciliary artery occlusion (Fig. 9-B).^23,33,55
7. CHOROIDAL NON-FILLING ON FLUORESCEIN FUNDUS ANGIOGRAPHY: In arteritic AION, if angiography is performed within the first few days after the onset of visual loss, half of the choroid (usually the inner half - Fig. 9-B) shows no filling because of complete occlusion of the corresponding posterior ciliary artery.^{9,11,18,20,25,48} This, also, is highly suggestive of arteritic AION. However, if angiography is performed after that period, the filling defect may be not be so apparent.
8. TEMPORAL ARTERY BIOPSY: This is the single most reliable test to firmly establish the diagnosis. If there is a high index of clinical suspicion of giant cell arteritis from the seven parameters mentioned above, and temporal artery biopsy on one side does not show arteritis, we perform the biopsy on the second side.⁴⁶ In 9% of our cases, the biopsy was negative on one side but positive on the other.⁴⁶Inadequate size and examination of the biopsy can give false negative results. It is important that the temporal artery biopsy piece must be at least one inch long, and must be sectioned serially so that skip areas of arteritis do not mislead.⁴⁶ In every patient with suspected giant cell arteritis, even when the clinical presentation is almost classical of giant cell arteritis, it is absolutely essential to perform the biopsy to have a morphologic diagnosis. This is necessary because the only effective treatment for giant cell arteritis is continuous systemic corticosteroid therapy, virtually for the rest of patient’s life, which is very likely to produce side-effects, some of which could be very serious. Also because giant cell arteritis is a well-known masquerader. It is absolutely essential to be certain about the diagnosis before advising a patient to go on lifelong systemic corticosteroid regime. This is also important from the medicolegal point of view. Therefore, we make no exception to the rule of doing a temporal artery biopsy to establish the diagnosis.

In conclusion, although no one of these eight criteria is infallible and present in 100% of arteritic AION cases, the information provided collectively by all of them together is extremely helpful in diagnosis. To confirm the diagnosis finally, temporal artery biopsy must be performed.

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