Patient complains of large, dark spot in vision of right eye
An 80-year-old white male presented to the eye clinic for a recent-onset visual disturbance. The patient reported that there was a large, black spot in the central vision of his right eye. He first noticed the dark spot the previous day and described his vision as being blurry. He denied any ocular pain or new onset of flashes or floaters.
The patient’s ocular history was significant for mild nonproliferative diabetic retinopathy in both eyes and a vitreal floater in the right eye. Ocular surgery history was significant for cataract removal from both eyes as well as bilateral Nd:YAG laser capsulotomy. The patient reported no recent or past trauma to the head or eye region. There was no significant family ocular history.
The patient’s medical history was significant for noninsulin-dependent diabetes mellitus, which was diagnosed 7 years ago; hypertension; hyperlipidemia; atrial fibrillation; ischemic cardiomyopathy; transient ischemic attack; cerebral infarction; psoriasis; and an ulcer of the esophagus.
Current medications included 40 mg of furosemide daily, 20 mg of lovastatin at bedtime, 25 mg of metoprolol daily, 30 mg of apremilast twice a day, 1,000 mg of metformin twice a day, 40 mg of omeprazole daily, 4 mg of glimepiride daily, 7.5 mg of warfarin daily, 1 g of sucralfate twice a day, 20 mg of lisinopril daily and 325 mg of ferrous sulfate twice a day. The patient reported an allergy to sulfonamides.
Corrected distance visual acuities were 20/200 OD and 20/50+2 OS. With pinhole, the visual acuities improved only by one letter in the right eye to 20/200+1 and to 20/40+2 OS. His pupils were equal, round and reactive to light with no relative afferent pupillary defect. Extraocular motilities were full with no restrictions. Confrontational fields were full to finger counting in the left eye, but revealed a paracentral scotoma when presented to the right eye. Intraocular pressures were measured with applanation tonometry and were 12 mm Hg OU. The patient’s blood pressure was 158/68 mm Hg.
Slit lamp examination of the anterior segment was unremarkable except for pseudophakia in both eyes. The irises had no defects and were also negative for rubeosis. After dilation, the posterior chamber intraocular lenses were seen to be clear, centered and in a stable position. Fundus examination revealed healthy, pink and distinct optic nerve heads with no edema or atrophy. The cup-to-disc ratios were found to be 0.35/0.35 in both eyes and were negative for neovascularization of the disc. Diffuse retinal edema was present adjacent to the inferior aspect of the optic disc. The macula was flat with several scattered perimacular microaneurysms in both eyes. The vasculature was tortuous but otherwise showed no abnormalities. The peripheral retina was flat with no apparent pathology. The vitreous was significant for floaters and negative for hemorrhages in both eyes.
A Humphrey visual field of the right eye revealed a supranasal central visual field defect that respected the vertical midline. Fluorescein angiography of the right eye showed normal filling, no evident occlusions and diffuse retinal edema within the inferior arcade. Optical coherence tomography of the right eye revealed no significant nerve fiber loss or macular edema. Carotid artery auscultation was negative for bruits.
The patient was previously seen for an annual diabetic eye exam 9 months before our examination. His visual acuity at that time was 20/20-1 OD and 20/25-2 OS. Also, confrontational fields were full to finger counting in both eyes at that visit. Otherwise, all entrance testing was consistent with the results found at our most recent evaluation.
What’s your diagnosis?
This patient was diagnosed with a twig retinal arteriole occlusion of the right eye.
Retinal artery occlusion refers to a blockage in the lumen of an arterial vessel by an obstructive entity such as, but not limited to, a thrombus or embolus. The incidence of retinal artery occlusions is 0.85 per 100,000 people per year (Klein et al.). According to Keith, the disorder more commonly affects men, occurs during the seventh decade of life and is often accompanied by hypertension (67%) and diabetes mellitus (33%).
Retinal artery occlusions
The vasculature of the retina begins with the ophthalmic artery, a branch of the internal carotid artery that divides into the central retinal artery before entering the eye along with the optic nerve. The central retinal artery supplies the inner two-thirds of the retina and the surface of the optic nerve through branches that expand throughout the retina. Retinal artery occlusion can occur in a variety of locations within this retinal vasculature. The place at which this occlusion occurs is the basis of the nomenclature used to define it.
There are three main locations: the central retinal artery (CRAO), a branch retinal artery (BRAO) or the cilioretinal artery (CIRAO). Approximately 57% of retinal artery occlusions occur at the central retinal artery, and 38% occur in a branch of the central retinal artery (Keith). The remaining 5% of retinal occlusions occur in the cilioretinal artery, which is present in only about 20% of the population.
There are several subcategories of artery occlusions as well, including hemiretinal occlusions and twig retinal occlusions. Hemiretinal artery occlusion falls under the category of CRAO and occurs when one of the two main branches of the central retinal artery become obstructed just anterior to the retrolaminar area, leading to ischemia of either the superior or inferior half of the retina. Twig retinal arteriole occlusion falls under the category of BRAO and is routinely defined as any occlusion that occurs beyond the second bifurcation of a branch retinal artery.
Most commonly it is an embolus that leads to the obstruction in a retinal artery occlusion. The lodging of an emboli causes a lack of oxygen supply to the area of the retina affected, often leading to ischemia. Atherosclerotic disease of the ipsilateral carotid artery is the most common etiology of retinal artery occlusion.
The incidence of carotid artery disease among patients with artery occlusions is 10% to 30%, and in some cases has been reported to be as high as 70% (Hedges et al.). This is important because the risk of future stroke and other vascular events increases dramatically with carotid artery disease.
Our patient’s diagnosis
Several differential diagnoses must be considered in our case. Acute and painless loss of monocular visual field occurs in many ocular disorders. Retinal vascular occlusions, vitreous hemorrhage, retinal detachment, macular disease, trauma, orbital tumor, anterior ischemic optic neuropathy, acute macular neuroretinopathy (AMN) and paracentral acute middle maculopathy (PAMM) are just some that may present with these symptoms. Most of these diagnoses, however, can be ruled out with a careful case history and thorough posterior segment examination.
Both AMN and PAMM present with a relative paracentral scotoma and limited reduction in visual acuity. AMN tends to affect women in their teens to 30s, while PAMM affects males in their late 50s.
PAMM is a newly discovered variant of AMN that separates itself by having different appearances on SD-OCT. Both AMN and PAMM have variable funduscopic appearances and little abnormality on fluorescein angiography, but often present with lesions near the macula. AMN lesions typically appear weeks to months after the initial vision loss but can be seen on SD-OCT as a hyperreflective band near the outer plexiform layer and outer nuclear layer. PAMM can appear similar to a cotton-wool spot upon fundus examination and is seen on SD-OCT as placoid, hyperreflective lesions within the inner nuclear layer.
The discrepancy of the demographics with our patient and the cases of AMN and PAMM seems to be a mark against these as potential diagnoses. Visual acuity also appears to not be drastically reduced in either of these diseases, where our patient’s was affected greatly. PAMM has been known to be associated with vascular diseases, such as with our patient. He, however, did not exhibit the typical appearance of hyperreflective lesions within the inner nuclear layer on SD-OCT.
PAMM is thought to be caused by retinal occlusions within the intermediate capillary plexus and deep capillary plexus, which causes ischemia to the inner nuclear layer of the retina. OCT angiography is a new modality that may reveal further information regarding the retinal capillary function. It was unavailable for our case. Due to the overall lack of some key findings, PAMM and AMN have been ruled out as potential diagnoses.
Retinal vascular occlusions can present with many different fundi appearances and should be considered a possible diagnosis. Due to the lack of retinal hemorrhages in our case, a vein occlusion was safely ruled out. The appearance of the retina and our patient’s visual acuity also did not match a CRAO. Patients with CRAO report visual acuity between counting fingers and light perception 94% of the time on their initial examination (Gerstenblith et al.). Branch retinal artery occlusions typically present with a wedge-shaped area of superficial whitening distal to the area of occlusion. Our patient’s fundus showed no such areas of superficial whitening.
Twig retinal arteriole occlusions, however, occur in small arteries that can be several bifurcations from the main branch. This fact makes diagnosing twig retinal occlusions sometimes challenging because they are not easily viewable upon fundus photography or fluorescein angiography. That was the case with our patient and is the precise reason why twig retinal arteriole occlusions are often a diagnosis of exclusion.
Retinal artery occlusions are often considered a form of stroke, and with that comes a similar clinical approach for treatment and management. It is important when dealing with these disorders that the clinician not only treat the acute outcome due to the occlusion, but also consider preventing further vascular events from taking place. We referred our patient to a retinal specialist as well as his primary care physician.
The retinal specialist saw our patient the next day and echoed our diagnosis. The patient’s visual acuity had already improved to 20/40 the following day. Branch artery and twig arteriole occlusions do not have a consensus treatment regimen. If a CRAO or BRAO is identified within 24 hours, one should perform ocular massage to dislodge any possible embolus. Breathing into a paper bag followed by breathing room air for 15 minutes may cause enough vasodilation to allow an emboli to move further downstream within the retinal vasculature and should be considered a potential treatment as well. Because a twig retinal arteriole is already a downstream vessel, these treatments would not be considered effective and, therefore, usually are not performed.
The three most common emboli responsible for blockage of an artery are platelet-fibrin, calcific and cholesterol (Hollenhorst plaque) emboli. Cholesterol emboli originate from atheromatous lesions in the ipsilateral carotid artery or aorta and account for 75% of the emboli observed in retinal artery occlusions (Walek et al.).
Our patient’s blood work, which included complete blood count with platelets, erythrocyte sedimentation rate and C-reactive protein, were all within normal limits. A transesophageal echocardiograph revealed no new changes to the patient’s cardiovascular disease. Carotid duplex ultrasonography revealed a mild atheromatous plaque at the right carotid bifurcation.
Carotid stenosis, if present, is based on velocity parameters. Typically, stenosis (decreased lumen size) causes the blood to be forced through the artery at a higher velocity. Blockage of 70% to 90% would be considered significant stenosis, and the patient should be considered a surgical candidate for carotid endarterectomy (Rerkasem et al.).
Patients with less than significant amounts of stenosis are typically managed with medications. Lipid-lowering statins such as simvastatin and antiplatelet therapy such as aspirin and clopidogrel have been proven to be successful in managing carotid artery stenosis.
Although the plaque in our patient’s right carotid was found not to be causing hemodynamically significant narrowing of the artery, it very well could have been responsible for the twig retinal arteriole occlusion. The patient was advised to continue following up with his primary care physician to better manage his systemic health and to return to the eye clinic for a follow-up visit in 3 to 4 months.
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- For more information:
- Zachary Lundgren is a fourth-year optometry intern from Pacific University College of Optometry in Forest Grove, Ore. He can be reached at email@example.com.
- Leonid Skorin Jr., OD, DO, MS, FAAO, FAOCO, practices at the Mayo Clinic Health System in Albert Lea, Minn., and is a member of the Primary Care Optometry News Editorial Board. He can be reached at Mayo Clinic Health System; firstname.lastname@example.org.
- Edited by Leo P. Semes, OD, FAAO, a professor of optometry, University of Alabama at Birmingham and a member of the Primary Care Optometry News Editorial Board. He may be reached at email@example.com.
Disclosures: The authors report no relevant financial disclosures.