By Erin Swift, O.D.
A 71 year old white male presents to your office for an annual eye exam. He was seen last year by you and his ocular history is remarkable for mild cataracts, scattered retinal drusen (outside the macula, non-visually significant), dry eye symptoms and low refractive error OU (20/20- acuity OD, OS). His medical history is significant for impaired fasting glucose, HTN and history of CVA in 2010 with right side paresis. Confrontation fields at last exam were full to finger count 360 OD & OS and patient denies loss of vision since the stroke. You requested the patient come back for extended visual field testing, but the patient never returned prior to today. At today’s exam, the patient reports his vision seems about the same as last year, no new complaints. When asked why he didn’t return for the visual field, patient reports he actually had it done somewhere else and didn’t want to repeat it. The patient does not have a copy of the field, but reports he was told the right eye was abnormal, but nothing could be done about it. Your exam from today shows a stable refraction, with a mild decrease in vision compared to last year (20/25 OD, OS), which you attribute to increased cortical spoking into the visual axis. The retinal drusen seem stable to last year and the patient’s dry eye complaints are largely resolved with artificial tears.
However, there are some new findings at this exam. During confrontation fields, the patient’s right eye is restricted in the inferior hemisphere only (full to finger count superiorly OD and 360 OS). In addition, during dilated exam, you notice superior pallor to the right optic nerve. No RAPD was noted in either pupil when tested pre-dilation. Upon further questioning of the patient about the visual field test and subjective peripheral vision, the patient reports he believes the field loss has been there since the stroke in 2010. Hmm, a year ago the patient denies field loss, the confrontation fields were full and the optic nerves both looked healthy. Now, inferior field loss is noted OD only with superior optic nerve pallor OD, but the patient reports the defect is longstanding. Something just doesn’t add up…
You convince the patient to come back for another field at your office (the patient reports it would be difficult to get a copy of the outside field) to evaluate more closely. So what do you expect to find? If the field loss is neurological in nature, due to the patient’s CVA in 2010, a right-side hemianopia or quadrantanopia would be most likely (since the patient has right-side paresis from a left-side lesion). However, confrontation fields from both this year and last year showed no vertical or bilateral field loss. The patient does have new inferior horizontal field loss OD only, with corresponding superior optic nerve pallor that was not previously noted. The patient comes in for automated visual field testing and confirms your suspicions: absolute altitudinal inferior defect OD (respects the horizontal midline) and full field OS. So what happened? Given your patient’s predisposition to vascular occlusions (h/o impaired fasting glucose, HTN and prior CVA), the mostly likely diagnosis is non-arteritic anterior ischemic optic neuropathy (NAION) sometime in the past year, but the patient was unaware of it. The optic nerve pallor and absolute altitudinal visual field defect indicate chronicity, so no further ocular treatment is indicated at this time. Patient education on importance of systemic management of vascular diseases can help decrease risk for future vision loss. Visual field loss can occur from a number of etiologies, including vascular occlusion to both the brain and optic nerve, so must rule each out separately and manage accordingly.