AION: Anterior Ischemic Optic Neuropathy

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Onset of My NAION. Over the end-of-year holidays 2003/2004 I developed a loss of vision in my left eye. I noticed that the world looked less bright through my left eye than through my right eye, and that this produced a noticeable sense of imbalance, visually, when walking about. I tried closing my right eye to see what my vision was like in my left eye and was dismayed to find it poor. It was like I was looking through foggy or dirty lenses with my left eye, especially in the lower (inferior) and right (medial, towards my nose) visual field. When I tried to read a newspaper with my left eye only, I discovered that I could not see clearly any words to the right or below my focal point, which made it difficult if not impossible to scan/read properly. Apparently the brain normally scans ahead (right and down), starting the processing of textual information before it enters the focal point, or at least the small focal point I had remaining in my left eye.

All this happened shortly after I had spent some time helping my son sand down the rusty roof on his auto and repaint it. I figured that I must have gotten some dust or paint in my left eye, so I irrigated my eye with isotonic saline (Ringer's actually) for several days, but that did not help. After a week or 10 days I went to see an ophthalmologist, Dr. Catherine Sloop, at the Greenville (NC) eye clinic. A swinging flashlight test revealed a Relative Afferent Pupillary Defect -- the pupillary response to bright light was abnormal in my left eye -- less constriction than normal and more of a rebound following constriction than is normal. Further examination showed that the superior (top) portion of the optic nerve in my left eye had edema (was swollen). This would be expected to be associated with problems in the lower visual field, as I was experiencing. A visual field test confirmed the degradation of vision in the lower visual field of the left eye. Furthermore, after the strain of that test I started having flashes of light in that eye, especially when my eyes were closed, but also sometimes imposing it over my binocular vision when my eyes were open. My brain interpreted these lights as a dynamic line plot. These lights stops after a few days.

Cause of NAION. Reduced flow of blood to the anterior optic nerve results in ischemia (tissue damage) and infarction (tissue death), as occurs with a brain stroke, but the cause is not usually a thrombus (attached blood clot) or embolus (traveling blood clot) but rather a period of hypotension (low blood pressure). The cause is likely vascular. The vascular problem may result from giant cell arteritis, an inflammatory condition of the blood vessels, or it may be nonarteritic. Arteriosclerosis (thickening and hardening of the arteries) and atherosclerosis (deposition of fatty substances and fibrous tissues on the inner walls of the arteries) may be suspected. For more details, please see Optic Neuropathy, Anterior Ischemic.

Diagnostic Tests. Dr. Sloop ordered an extensive battery of blood tests for me, including a liver and lipid panel (I have high cholesterol and take Lipitor), potassium (I have hypertension and take a diuretic and potassium supplements), fasting blood sugar (diabetes can be a contributing factor), two tests for syphilis (RPR and FTA-ABS), a complete blood count, and tests for autoimmune dysfunction including ESR (erythrocyte sedimentation rate -- if high, body is attacking itself), ANA (antinuclear antibody -- antibodies directed against own body), and ACE level (screening test for neurosarcoidosis, an autoimmune disorder that usually involves the lungs -- I got a chest X-Ray too). Also obtained was a creatinine test (breakdown product of protein, high if bad kidneys, requested by the radiologists doing a brain scan on me). She also sent me to have a CT brain scan. The brain scan revealed no problems other than those associated with my chronic sinus disease (thickening of the membranes lining the sinuses, possible air fluid levels, and a hypoplastic right maxillary sinus -- that is, little air relative to bone -- don't call me an air head, but you may call me a bone head). Of course, I was relieved not to have been found to have a brain tumor or other such gross brain defect. My blood work showed no sign of infectious or autoimmune disease, which makes the diagnosis of Nonarteritic Anterior Ischemic Optic Neuropathy look right on.

Dr. Sloop also referred me to a neurologist, Dr. Donald Price. Dr. Price put me on a three day course of IV steroid treatment. Each day I was given a full gram of Solu-Medrol and then I was tapered off with oral prednisone. Among the side-effects I experienced from this treatment were tachycardia, elevated blood pressure (especially systolic), hiccups, and bruising (especially the top of my hands, where the IVs were inserted). Also my teeth got so close together for a few days that I could no longer get floss between them. I guess they get closer when the steroids reduce the swelling in my head. I have had this same side effect other times when taking prednisone for my sinus condition. Steroid therapy is controversial for NAION, but may help when the actual problem is arteritic AION or when it is Optic Neuritis, a condition which is associated with multiple sclerosis and which is more likely in younger persons (< 50) than is AION. For more details on optic neuritis, please see Optic Neuritis and Optic Neuritis, Adult. The steroid treatment produced no improvement in the vision in my left eye.

Dr. Price ordered additional blood tests (Antithrombin III, Lupus Anticoagulant, Lyme disease, Protein C, Protein S, and Clotting Factor 5 Leiden), a cranial MRI (to check my brain for evidence of strokes), and a MR Angiography to check the condition of my blood vessels, both intra- and extra-cranial. Dr. Price also sent me to a cardiology clinic to have an echo cardiogram and an EKG, just in case there is a heart problem contributing to my vascular problem in the left eye. My echocardiogram and EKG were unremarkable and there were no vascular problems detected with the angiogram. The cranial MRI showed evidence of several very small and scattered lesions in the subcortical white matter of the frontal lobes and disease in my sinuses, but was otherwise unremarkable. The lesions were said to be of no clear relevance to my eye problems. My research colleague, neuropsychologist Erik Everhart, jokingly noted that these lesions provide an organic explanation for my lack of inhibition during faculty meetings. The blood work showed one abnormality -- Lupus Anticoagulant (LAC). Persons who test positive for LAC (on two tests at least eight weeks apart) and who have thrombotic events (including NAION) are considered to have Antiphospholipid Syndrome (APS). People with APS usually have clotting problems that require the use of a blood-thinning agent (such as coumadin). They may have to use blood-thinning agents for life, or their blood work may indicate that they no longer need it. APS has been associated with AION -- see the Handbook of Ocular Disease Management.

I saw Dr. Darla Liles, a hematologist, about the positive test for LAC. She told me that she had never before seen a patient with visual problems resulting from APS, briefly discussed the use of coumadin and heparin for people with LAC problems, and had her nurse draw six vials of blood from me for testing to see if I really do have LAC -- she described the earlier test I had as a screening test. My bloodwork came back with no sign of lupus anticoagulant antibody or any related problem, so I don't need to worry about that any more. I asked her about my neurologist's recommendation that I take either small daily doses of aspirin or Plavix. I expressed my discomfort with taking aspirin, given my suspicion that aspirin accelerates the rate of growth of the damn polyps in my sinuses -- persons with Samter's triad have asthma, polyps, and sensitivity to aspirin. I used to have asthma and now have polyps. While I do not have the sort of life-threatening reaction to aspirin that Samter's patients have, I worry that I may have a lesser related condition in which aspirin contributes to the problems with the polyps. Whether from cause or mere coincidence, I became more congested than usual when I started taking a small daily dose of aspirin. My hematologist thought it a good idea to try replacing the aspirin with Plavix. She did warn that it can cause some serious side effects, but in less than one percent of those who take it. I started on Plavix in April of 2004. One of the side effects from my use of Plavix was engorgement of vascular benign tumors on my scrotum. Even before the Plavix, these things would bleed terribly if I scratched one open, so in August of 2004 I had surgery to remove them.

Cup to Disk Ratio. The blood supply of the anterior portion of the optic nerve is provided by an artery that is lies deep inside the optic nerve, creating a cup at the disk end. Some have argued that when the cup to disk ratio is low, the axons in the optic nerve may be very crowded and the artery may be more subject to events that disrupt the flow of blood in it, and that the morphology of such a "disk at risk" may result from the optic nerve fibers having to pass through an abnormally small scleral canal when entering the eye. For more details, please see Neuro-ophthalmic Manifestations of Vascular Eye Diseases. A leading expert on vascular problems in the eye (Hayreh, personal communication, January 2004) strongly objects to the conclusion that AION results largely from the morphology I described as "a disk at risk." The disk is the total width of optic nerve head. The blood vessels come out at the cup, which is the central part of the optic nerve head where there are no nerve fibers. Imagine a donut: the hole is the cup and the width of the donut is the disk. A cup to disk ratio of 0.4 means that the hole is 2/5 the width of the entire disk. A 'normal' cup to disk ratio is between .3 and .5. My cup to disk ratio is about .3, which is on the small end of the normal range. Cup to disk ratio tends to be small in Caucasians. This racial difference in cup size is reflected in the racial difference in incidence of NAION -- 95% of cases occur in Caucasians. A small or absent cup is associated with NAION, a large cup is associated with glaucoma. The article "Ischemic Optic Neuropathies" (Rucker et al., Current Opinion in Neurology, 2004, 17, 27-35) has an informative photo of an eye with normal disk to cup ratio (.4) and one with a low cup to disk ratio (< .1).

Color Vision. Abnormalities of color vision are associated with NAION. My doc always gives me such a test, but my color vision appears to be unaffected by NAION. You can find the Ishihara Test for Color Vision online.

Prognosis and Treatment. No reliable treatment is available for NAION, but one should try to reduce risk factors that may make more likely an ischemic event in the fellow eye, which is a distressingly likely event. Progressive loss of vision in the already affected eye is not very likely, possibly because the death of nerve cells in the affected anterior optic nerve relieves the compression in that optic nerve. Surgical optic nerve sheath compression has proved to be of no benefit.

Risk of Recurrence in the Fellow Eye. There are great differences in estimates of the probability of recurrence of NAION in the second eye. You must consider the time frame employed in the study. For example, if researcher A follows her patients for two years after the first incident and researcher B follows his patients for ten years, you should not be surprised that the incidence of recurrence was much higher for B than for A. In a quick review of the medical literature I found estimates of 53.5%, 12% to 40%, and less than 43% within three years.

Risk Factors. Sohan Singh Hayreh at the Ocular Vascular Clinic at the University of Iowa has posted a list of risk factors in the excellent document Anterior Ischemic Optic Neuropathy. Dr. Hayreh has been kind enough to correspond with me regarding AION. It was Dr. Hayreh who first referred to this condition as Anterior Ischemic Optic Neuropathy. He was also the person first to report that eyes with AION have a smaller cup than is normal. He has, however, stressed that small cup to disk ratio (the so called "disk at risk"), is not the primary contributory factor in the development of AION, but rather is only a secondary contributory factor. Hayreh also argues that nocturnal arterial hypotension (low blood pressure while sleeping) may often be "the straw that broke the camel's back," especially when hypertensive persons are prescribed long-lasting blood pressure medications that are taken in the evening. Combined with the naturally occurring dip in blood pressure that occurs during sleep, such medication may reduce the flow of blood in the anterior optic tract to such an extent that neurons there die. With this in mind, I have already stopped taking blood pressure medication in the evening, shifting that dose to earlier in the day. I would also like to have a 24-hour recording of my blood pressure, to see how sharp is the dip in blood pressure that I experience while sleeping. Hayreh has suggested that systemic steroid therapy may prevent or reduce loss of visual function if it is initiated prior to any loss of vision -- that is, if the optic edema is observed in a routine examination prior to the patient reporting any loss of vision, then prompt treatment with systemic steroids may, in a small group of patients, promote some recovery of vision and or prevent additional loss of vision.

Sleep Apnea. Research published in the Archives of Ophthalmology. 2002, 120: 601-605 has shown that 71% of patients with NAION also have sleep apnea, as compared to only 24% of a random control sample. See also Papilledema and Obstructive Sleep Apnea Syndrome. Of course, the association between sleep apnea and NAION may not be direct but may rather result from a constellation of third variables (such as hypertension and related factors including the use of long-lasting blood pressure medications) which are causally related to both NAION and to sleep apnea, resulting in a spurious association between sleep apnea and NAION in the absence of any causal relationship between sleep apnea and NAION. For many years my wife has told me that I snore like a chainsaw and that she has observed me stop breathing while sleeping frequently. In fact, if we don't sleep in separate bedrooms, my awful snoring and thrashing about prevent her from getting any sleep. I have seen a pulmonologist, Dr. Robert Dietrich (who expressed concern that my sinus disease may contribute to breathing problems during sleep), and have spent two nights in a sleep laboratory. The first night, the sleep study, showed that I have mild sleep apnea. Dr. Dietrich said that I stopped breathing nine to ten times an hour, 52 times during the study. Most of my sleep was Stage 2 sleep, I was in REM (dream) sleep a good deal, but I was in deep sleep (Stages 3 and 4) very little. He described my sleep apnea as "mild" and said that he would not treat it were it not for the association with AION. On the eve of April Fools' Day, 2004, I spent a second night in the sleep lab for a CPAP titration -- that is, to figure out what pressure should be used with the CPAP machine. Because of my chronic sinus disease, they put a full mask (mouth and nose) on me. Despite having taken a sleeping pill (Ambien, 10 mg), I just could not sleep with this thing on me. I felt like I was breathing in a bag and it irritated me greatly under my mouth. After 80 minutes I buzzed them and told them I could not deal with the full mask, to try a nose-only mask. The nose mask was much better, and I was able to sleep with it for four hours, long enough for the titration. Just recently I picked up my CPAP machine. The provider told me that nobody sticks with the masks that are given out at the sleep lab. I asked about the one that an old friend recommended to me, and he says that they carry it. I'll go ahead and give the nose mask I was given a try (but the full face mask they gave me is just intolerable). I got it all set up to use the first night and then I fell asleep without putting it on. I got up about 3 AM and put it on then and kept it on for about 3 hours, during which time I woke up several times. I have gotten used to wearing the nose mask, but sometimes I fall asleep before I remember to put it on.

See the emedicine article Snoring and Obstructive Sleep Apnea, CPAP. About half of persons who try the CPAP just can't get used to it. For these people, alternative treatments include weight loss (I am about 200 lb now, would like to lose about 25 lb), an uncomfortable dental appliance, and surgery. Avoiding alcohol in the evening can help too -- I guess I am going to have to drink my beer and Scotch in the morning instead of the evening.

My Vision Now. I returned to my ophthalmologist ten weeks after my initial visit for this problem. Her examination revealed that there was no longer any edema or hemorrhage obvious in my optic disk. I did still show the relative afferent pupillary defect. My vision (with glasses) tested 20/20 in both eyes, but to get that acuity with my left eye I had to rotate my head to put each letter exactly on the focal point. Because my visual acuity at focal point is good, Dr. Sloop advised that I should have no problem passing the eye exam that is given when renewing one's driver's license. I saw her again in June for another follow-up examination. That examination showed no change in my vision. I saw her again in July of 2005 -- again, no change. At my examination in July of 2006 my corrected vision was actually a bit better than normal (15/20).

Conditions Which Might Be Mistaken as NAION. Loss of vision that is diagnosed as due to NAION can be caused by other factors, so it is important to have a thorough examination, including imaging of the brain. For example, Lee et al (Atypical features prompting neuroimaging in acute optic neuropathy in adults) reported on several cases which were initially diagnosed as as optic neuritis or NAION but in which the problem was subsequently found to stem from intracranial lesions. Those who had been incorrectly diagnosed with NAION had shown some symptoms not typical with NAION patients, including a lack of the usual vascular risk factors, transient visual loss prior to the episode that was diagnosed as NAION, and a progressive loss of vision rather than the loss occurring all at once.

Experiences of Others Who Have NAION

Bill Patton -- nicely constructed page. Includes information about link between lipid disorders and NAION.

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