When Retinal Disease Masquerades as Neuro-Ophthalmic Disease
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INTRODUCTION
Welcome to the “Neuro Nuggets” column within the Journal of Medical Optometry (JoMO)! This column aims to make neuro-ophthalmic disease more approachable by blending real-world clinical cases with evidence-based medicine. The patient in this edition’s column features a familiar visual field defect from a less-familiar etiology. Enjoy!
CASE PRESENTATION
A 77-year-old white male presented as a consult from an outside eye care provider who noted abnormalities on automated perimetry. The patient’s past medical history included migraines, basal cell carcinoma of the skin, hypertension, obstructive sleep apnea, and prior heart valve replacement. The patient was followed for glaucoma suspicion due to moderate optic nerve cupping in each eye. Additionally, he had cataract surgery with posterior chamber intraocular lens replacement in each eye several years prior; there were no documented surgical complications.
On examination, the patient’s best-corrected visual acuity was 20/20 in the right eye and 20/30 in the left eye (due to mild dry age-related macular degeneration and vitreomacular traction in the left eye). Color vision by Ishihara was intact in each eye. Pupils were physiologically anisocoric, round and reactive to light, and without any relative afferent pupillary defect. Extraocular motility evaluation demonstrated normal ductions and saccades in both horizontal and vertical directions. Slit lamp evaluation was within normal limits and age-appropriate in each eye with clear intraocular lenses bilaterally. Intraocular pressure was normotensive and symmetric.
On dilated fundus evaluation, there was evidence of mild hard drusen in the left eye greater than the right eye. The optic nerve neuro-retinal rim tissue appeared pink and intact with flat, distinct margins in each eye. There was mild peripapillary atrophy in each eye and very subtle pigmentary changes inferotemporal to the optic nerve head bilaterally. There was no sign of any anterior or posterior segment inflammatory process.
Automated Humphrey visual field testing showed superotemporal defects in each eye, suggesting a bitemporal hemianopia (Figure 1b and 1c). However, the superotemporal defect in the right eye notably did not “respect the vertical meridian” as it crossed into the superonasal sector, and the defects seemed to originate from the blind spot (correlating to the optic nerve head) in each eye. This visual field pattern was similar to the reported findings from the patient’s outside eye care provider, raising concern for a potential process impacting the optic chiasm. However, further testing suggested an alternative explanation.
Figure 1. Humphrey visual field 24-2 SITA Fast (B, C) and fundus autofluorescence imaging (A, D). A and B = left eye, C and D = right eye.
Figure 2. Fundus photographs of the right eye (A) and the left eye (B).
Fundus photography documented subtle pigmentary changes along the inferior arcade stemming from the optic nerve head bilaterally (Figures 2a and 2b). Optical coherence tomography (OCT) of the retinal nerve fiber layer (RNFL) demonstrated several sectors of borderline/thin RNFL in multiple sectors (Figure 3). OCT of the macula showed outer retinal thinning in an arcuate pattern along the inferior arcades emanating from the optic nerve head in each eye (Figures 4a and 4b). Fundus autofluorescence (FAF) imaging showed a partial arcuate pattern of hypo-autofluorescence that emanated from the optic nerve head, right eye worse than the left eye (Figures 1a and 1d).
Figure 3. Spectral-domain OCT Peripapillary RNFL scans
Figure 4. SD-OCT line scan of the right eye (A) and the left eye (B).
Altogether, the patient’s examination findings and ancillary test results were concerning for a possible inherited retinal dystrophy. Namely, sectoral retinitis pigmentosa sine pigmento was felt to be a leading differential diagnosis. The day after the eye exam, the patient called and informed the clinic that his mother and three younger brothers all were previously diagnosed with retinitis pigmentosa and had issues with scotopic/night vision. A consult with an inherited retinal disease specialist with electrophysiologic retinal evaluation and genetic testing is pending at the time of submitting this case report.
DISCUSSION
When eye care providers encounter bitemporal visual field defects, disease involving the optic chiasm (often pituitary adenoma) is likely at the forefront of the differential diagnosis. However, many other processes may present with similar visual field defects.1,2 Ancillary testing such as OCT can be instrumental in helping to narrow the differential diagnosis and aid in appropriately directing a work-up for unexplained visual loss.3 There is often a need to distinguish ocular/retinal disease from neuro-ophthalmic conditions – or potentially recognize overlap between them.
Retinitis pigmentosa (RP) is a group of progressive, inherited retinal diseases that often present with peripheral visual deficits and nyctalopia.4,5,6 While many patients with RP present with classic features (i.e., retinal pigmentary changes such as “bone spicules,” arteriolar narrowing, cystoid macular edema, optic disc pallor), the clinical presentation is heterogeneous.4,5,7 There are various theories surrounding the formation of the “bone spicule” pigmentation with some groups describing pigment-laden macrophages while others propose migration or translocation of retinal pigment epithelium (RPE) cells.7 Some cases of RP “sine pigmento” present without the characteristic pigmentary abnormalities 5,7 but may go on to develop pigmentation later in their disease course.7 Sectoral RP has been described dating back to the 1930s and seems to predominantly impact the photoreceptors along the inferior retinal arcades.4,5 Sectoral RP patients present with varying levels of outer retinal or RPE irregularities that may be quite subtle on clinical examination.4,5 Multimodal imaging including fundus autofluorescence (FAF), OCT, and color fundus photography can be instrumental in identifying patients with subtle clinical retinal pigment changes. OCT imaging may reveal small nodules overlying the RPE, retinal layer disorganization and thinning, and cystic degeneration of the inner retinal layers.7 Electrophysiologic testing, such as electroretinography (ERG), also plays a key role in the work-up of these patients. In sectoral RP, ERG responses are reported to have higher amplitudes than patients with generalized RP.4
Imaging with FAF has increasingly played a key role in the identification of various retinal conditions. Areas of decreased autofluorescence (hypo AF) have been shown to correlate to visual field defects in patients with RP.4,6 The finding of a ring of increased autofluorescence (hyper AF) in the macular region has been reported to correspond to the border of photoreceptor loss and correlates with areas of alterations in photoreceptor integrity demonstrated on OCT imaging.6 Several different patterns of hyper AF rings, both within the macula and outside of the macula, have been reported in the literature.6 There is a notable overlap of AF patterns across various RP genotypes (i.e., the AF pattern does not necessarily predict the genetic defects in patients with RP).6 A study evaluating 77 patients with RP who had macular FAF imaging found that 64.9% of participants had ring-shaped hyper AF.7
There are sparse cases of sectoral RP presenting with bitemporal hemianopia reported in the literature.5 In this case, FAF demonstrated an abnormal pattern of reflectance that would have otherwise gone unnoticed on clinical exam alone – revealing the likely diagnosis of sectoral RP sine pigmento. Without this quick, non-invasive ancillary imaging modality, the patient might have undergone potentially unnecessary (and expensive) diagnostic testing, such as magnetic resonance imaging (MRI).
CLINICAL PEARLS
- Bitemporal visual field defects are not always “neurologic” in etiology and may stem from underlying retinal disease
- Fundus autofluorescence is an instrumental non-invasive imaging modality that can unmask subtle posterior segment ocular pathology
- Appropriately distinguishing between retinal and neuro-ophthalmic etiologies of visual loss helps to properly direct work-up
REFERENCES
- Sowka JW, Luong VV. Bitemporal visual field defects mimicking chiasmal compression in eyes with tilted disc syndrome. Optometry. 2009 May;80(5):232-42. doi: 10.1016/j.optm.2008.11.005. PMID: 19410228.
- Zaslavsky K, Eshtiaghi A, Jeeva-Patel T, Christakis PG, Margolin E. Bitemporal Hemianopia Secondary to Acute Zonal Occult Outer Retinopathy. J Neuroophthalmol. 2021 Dec 1;41(4):e749-e751. doi: 10.1097/WNO.0000000000001167. PMID: 33470740.
- Sullivan-Mee M, Amin P, Pensyl D, Katiyar S. Differentiating Occult Branch Retinal Artery Occlusion from Primary Open-angle Glaucoma. Optom Vis Sci. 2018 Feb;95(2):106-112. doi: 10.1097/OPX.0000000000001170. PMID: 29370018.
- Meyerle CB, Fisher YL, Spaide RF. Autofluorescence and visual field loss in sector retinitis pigmentosa. Retina. 2006 Feb;26(2):248-50. doi: 10.1097/00006982-200602000-00030. PMID: 16467695.
- Pellegrini F, Prosdocimo G, Romano F, Interlandi E. Retinitis Pigmentosa Sine Pigmento Mimicking a Chiasm Disease. Neuroophthalmology. 2017 Mar 15;41(4):198-201. doi: 10.1080/01658107.2017.1292532. PMID: 29344059; PMCID: PMC5762150.
- Dowd-Schoeman TJ, Rosenbloom J, Ameri H. Patterns of Autofluorescence in Common Genotypes of Retinitis Pigmentosa. Ophthalmic Surg Lasers Imaging Retina. 2021 Aug;52(8):426-431. doi: 10.3928/23258160-20210727-03. Epub 2021 Aug 1. PMID: 34410191.
- Lee EK, Lee SY, Ma DJ, Yoon CK, Park UC, Yu HG. RETINITIS PIGMENTOSA SINE PIGMENTO: Clinical Spectrum and Pigment Development. Retina. 2022 Apr 1;42(4):807-815. doi: 10.1097/IAE.0000000000003367. PMID: 34907125.
The authors have no financial disclosures, and no sponsorship or funding was involved in this work.
Dr. Kane graduated from New England College of Optometry in 2015 and went on to complete an ocular disease/primary care residency at VA Boston Jamaica Plain from 2015-2016. He is currently an attending optometrist at VA Boston. His interests include clinical teaching, neuro-ophthalmic disease, retinal vascular disease, glaucoma, and ocular manifestations of systemic disease.
Jade Pacheco is currently working to complete her residency in Vision Rehabilitation at the Boston VA Healthcare System. She is a 2024 graduate from the New England College of Optometry. Jade obtained her undergraduate degree from Providence College with a double major in Biology and Health Policy & Management.
Dr. Marie Mantelli was raised in Thompson, Connecticut. She attended the University of New England in Biddeford, Maine where she received her Bachelor of Science in Medical Biology. She went on to receive her Doctorate in Optometry and Masters of Public Health at MCPHS University in Worcester, Massachusetts in 2016. She continued her education after graduating by completing a residency in ocular disease and primary care at the VA Maine Healthcare System. Dr. Mantelli currently provides care to our veterans at the Worcester VA Clinic.
