Visual Cortical Thickness Increases with Prolonged Artificial Vision Restoration.

The Argus II retinal prosthesis restores visual perception to late blind patients. It has been shown that structural changes occur in the brain due to late-onset blindness, including cortical thinning in visual regions of the brain. Following vision restoration, it is not yet known whether these visual regions are reinvigorated and regain a normal cortical thickness or retain the diminished thickness from blindness. We evaluated the cortical thicknesses of ten Argus II Retinal Prostheses patients, ten blind patients, and thirteen sighted participants. The Argus II patients on average had a thicker left Cuneus Cortex and Lateral Occipital Cortex relative to the blind patients. The duration of the Argus II use (time since implant in active users) significantly partially correlated with thicker visual cortical regions in the left hemisphere. Furthermore, in the two case studies (scanned before and after implantation), the patient with longer device use (44.5 months) had an increase in the cortical thickness of visual regions, whereas the shorter-using patient did not (6.5 months). Finally, a third case, scanned at three time points post-implantation, showed an increase in cortical thickness in the Lateral Occipital Cortex between 43.5 and 57 months, which was maintained even after 3 years of disuse (106 months). Overall, the Argus II patients' cortical thickness was on average significantly rejuvenated in two higher visual regions and, patients using the implant for a longer duration had thicker visual regions. This research raises the possibility of structural plasticity reversing visual cortical atrophy in late-blind patients with prolonged vision restoration.

Metastatic neuroendocrine tumors mimicking as primary ocular disease.

PURPOSE: To report two cases of metastatic neuroendocrine tumors masquerading as primary ocular disease. OBSERVATIONS: Case 1 is a 38-year-old man who was referred with subacute onset diplopia and fluctuating ptosis suggestive of myasthenia gravis. Case 2 is a 21-year-old man who presented with blurry vision and was found to have a pigmented ciliary body mass and retinal detachment suggestive of uveal melanoma. Both patients were ultimately diagnosed with metastatic neuroendocrine tumors. CONCLUSIONS AND IMPORTANCE: Neuroendocrine tumors, though rare and infrequently metastatic to the eye and orbit, can initially present with ocular signs. A broad differential and careful consideration of ocular and systemic symptoms are critical in such challenging cases.

Visual-tactile shape perception in the visually restored with artificial vision.

Retinal prostheses partially restore vision to late blind patients with retinitis pigmentosa through electrical stimulation of still-viable retinal ganglion cells. We investigated whether the late blind can perform visual-tactile shape matching following the partial restoration of vision via retinal prostheses after decades of blindness. We tested for visual-visual, tactile-tactile, and visual-tactile two-dimensional shape matching with six Argus II retinal prosthesis patients, ten sighted controls, and eight sighted controls with simulated ultra-low vision. In the Argus II patients, the visual-visual shape matching performance was significantly greater than chance. Although the visual-tactile shape matching performance of the Argus II patients was not significantly greater than chance, it was significantly higher with longer duration of prosthesis use. The sighted controls using natural vision and the sighted controls with simulated ultra-low vision both performed the visual-visual and visual-tactile shape matching tasks significantly more accurately than the Argus II patients. The tactile-tactile matching was not significantly different between the Argus II patients and sighted controls with or without simulated ultra-low vision. These results show that experienced retinal prosthesis patients can match shapes across the senses and integrate artificial vision with somatosensation. The correlation of retinal prosthesis patients' crossmodal shape matching performance with the duration of device use supports the value of experience to crossmodal shape learning. These crossmodal shape matching results in Argus II patients are the first step toward understanding crossmodal perception after artificial visual restoration.

Factors Affecting Ophthalmology Resident Choice to Pursue Neuro-Ophthalmology Fellowship Training.

BACKGROUND: The number of ophthalmology-trained residents applying to neuro-ophthalmology fellowships has not increased despite a trend toward seeking fellowship training after residency. This study sought to identify factors affecting the choice to pursue or not pursue neuro-ophthalmology fellowship training by graduating ophthalmology residents and recently graduated neuro-ophthalmology fellows. METHODS: An anonymous survey was sent to Association of University Professors of Ophthalmology residency directors to distribute to post-graduate Year 4 (PGY4) ophthalmology residents graduating in either 2018 or 2019. A second anonymous survey was distributed via the North American Neuro-Ophthalmology Society (NANOS) Young Neuro-Ophthalmologists listserv to ophthalmology-trained neuro-ophthalmology fellows. A total of 147 respondents, including 96 PGY4 ophthalmology residents not going into neuro-ophthalmology and 51 practicing neuro-ophthalmologists are included. RESULTS: The most common reasons for residents to choose to not pursue further training in neuro-ophthalmology included a stronger interest in other fields, types of patients seen, no intraocular surgery, and the assumption that it is a nonsurgical discipline. The leading factors influencing graduated, ophthalmology-trained fellows to choose neuro-ophthalmology included interest in the clinical diseases treated, interaction with other specialty fields, and a supportive NANOS culture. Interestingly, despite perceptions of graduating residents, two-thirds of the neuro-ophthalmologists surveyed perform surgery. There were no differences between the 2 groups with respect to the degree of exposure to neuro-ophthalmology in medical school, presence of a dedicated neuro-ophthalmology rotation in residency, or timing of the rotation. CONCLUSIONS: There are a variety of factors influencing decisions regarding pursuing neuro-ophthalmology fellowship among ophthalmology residents. The perceived lack of surgical opportunities in neuro-ophthalmology is a deterrent for many. However, a significant number of neuro-ophthalmologists continue to perform surgery, including intraocular surgery. Repeated exposure later in residency may provide an opportunity to reconsider the field and to re-emphasize opportunities to remain surgically involved as a neuro-ophthalmologist. Exposure to the practice patterns of recently graduated neuro-ophthalmologists offers residents in training excellent exposure to the contemporary practice of neuro-ophthalmology. Hence, ensuring trainees receive a balanced exposure to practicing neuro-ophthalmologists across the spectrum of seniority and scope of practice may promote greater interest among ophthalmology residents to pursue a career in neuro-ophthalmology.

Multisensory perception in Argus II retinal prosthesis patients: Leveraging auditory-visual mappings to enhance prosthesis outcomes.

Crossmodal mappings associate features (such as spatial location) between audition and vision, thereby aiding sensory binding and perceptual accuracy. Previously, it has been unclear whether patients with artificial vision will develop crossmodal mappings despite the low spatial and temporal resolution of their visual perception (particularly in light of the remodeling of the retina and visual cortex that takes place during decades of vision loss). To address this question, we studied crossmodal mappings psychophysically in Retinitis Pigmentosa patients with partial visual restoration by means of Argus II retinal prostheses, which incorporate an electrode array implanted on the retinal surface that stimulates still-viable ganglion cells with a video stream from a head-mounted camera. We found that Argus II patients (N = 10) exhibit significant crossmodal mappings between auditory location and visual location, and between auditory pitch and visual elevation, equivalent to those of age-matched sighted controls (N = 10). Furthermore, Argus II patients (N = 6) were able to use crossmodal mappings to locate a visual target more quickly with auditory cueing than without. Overall, restored artificial vision was shown to interact with audition via crossmodal mappings, which implies that the reorganization during blindness and the limitations of artificial vision did not prevent the relearning of crossmodal mappings. In particular, cueing based on crossmodal mappings was shown to improve visual search with a retinal prosthesis. This result represents a key first step toward leveraging crossmodal interactions for improved patient visual functionality.

A case of reversible toxic optic neuropathy from tacrolimus (FK506).

PURPOSE: To report a rare case of reversible vision loss from tacrolimus-associated toxic optic neuropathy. OBSERVATIONS: A 30-year-old man with cystic fibrosis requiring bilateral lung transplantation developed painless, bilateral, gradual onset central vision loss with dyschromatopsia two years after starting tacrolimus. Visual fields revealed bilateral cecocentral scotomas. Fundoscopy demonstrated bilateral temporal pallor of the optic nerves. Testing for nutritional deficiencies was unremarkable. Tacrolimus was switched to cyclosporine and the patient was started on idebenone. Two months later, the patient demonstrated marked improvement in his visual acuity and dyschromatopsia. CONCLUSIONSAND IMPORTANCE: Neurotoxicity is a rare but major potential side effect of tacrolimus. Idebenone should be considered as a potential, low-risk supplement for transplant patients who are immunosuppressed in whom toxic optic neuropathy is a concern.

Paracentral and Cecocentral Scotomas After Pars Plana Vitrectomy for Rhegmatogenous Retinal Detachment.

PURPOSE: To describe novel paracentral and cecocentral visual scotomas after pars plana vitrectomy (PPV) for rhegmatogenous retinal detachment (RRD) repair over a 5-year period. DESIGN: Retrospective case series. METHODS: This was a retrospective review of all patients who reported visual scotomas after 23- or 25-gauge PPV (Constellation Vision System, Alcon, Fort Worth, Texas, USA) for RRD repair by a single surgeon (RNK) from January 2013 through December 2018. All patients had multimodal imaging (fundus photography, fluorescein angiography, autofluorescence, and spectral-domain optical coherence tomography [OCT] and standardized central Humphrey visual field [HVF] testing) to further characterize the visual scotomas. RESULTS: Nine patients reported visual scotomas after PPV for RRD from January 2013 to December 2018 with incidence of 6.4% (9/140). The average age was 61 years (range 53-71 years) and 3 of 9 were female. The preceding RRD was macula-sparing for 6 of 9 patients; all of them involved the right eye. Seven of 9 patients reported the central scotoma within the first week after surgery. All 9 patients noted paracentral or cecocentral location of scotomas involving the inferior temporal visual field. Multimodal imaging was only significant for corresponding focal superior nasal ganglion cell loss on spectral-domain OCT. Two of 9 patients had symptomatic visual loss from the scotoma because it involved the center of fixation. CONCLUSIONS: We report a novel central/paracentral visual field defect after PPV for RRD repair. The paracentral scotoma is located inferotemporally and correlates anatomically with ganglion cell loss on spectral-domain OCT. The visual field defect and corresponding anatomic ganglion cell loss suggests a focal retinal injury. We propose that it could be caused by trauma from air flow from the infusion cannula during the air-gas exchange, angled directly toward the superior nasal paracentral retina. Surgeons should be aware of this complication and take precautions to slowly inject the gas after the air-gas exchange.

Vision loss, gaze palsy, and nystagmus in a patient with leukemia.

A 22-year old male with a history of B-cell acute lymphoblastic leukemia with recent bone marrow transplantation and on immunosuppressive therapy presented with painless, subacute vision loss of two weeks duration. He exhibited a horizontal gaze palsy, nystagmus, and mildly swollen and hyperemic optic discs with peripapillary flame hemorrhage on retinal exam. He had bilateral cecocentral scotomas on visual field exam, and MRI of his brain/orbits demonstrated hyperintensities in the hypothalamus, periaqueductal gray, and dorsal rostral medullary regions. After continued progression of symptoms despite discontinuation of the patient's tacrolimus, an empiric trial of IV thiamine treatment was started before the patient's lab vitamin levels were available, given strong clinical suspicion for a nutritional etiology. The patient's clinical presentation improved dramatically, and he achieved a final visual acuity of 20/20, full visual fields bilaterally, and resolution of nystagmus. A final diagnosis of Wernicke's encephalopathy was supported by his clinical course, imaging findings, and further confirmation with blood thiamine levels. This case presents unique ocular manifestations of Wernicke's encephalopathy and highlights the importance of early diagnosis in this potentially reversible condition.

THE SECOND BLIND SPOT: SMALL RETINAL VESSEL VASCULOPATHY AFTER VACCINATION AGAINST NEISSERIA MENINGITIDIS AND YELLOW FEVER.

PURPOSE: To describe a case of small retinal vessel vasculopathy postvaccination. METHODS: We report the case of a 41-year-old white man who presented with a "second blind spot," describing a nasal scotoma in the right eye that started 4 days after vaccinations against Neisseria meningitidis and the yellow fever virus, and after a 2-month period of high stress and decreased sleep. Clinical examination, Humphrey visual field testing, and multimodal imaging with fundus photographs, autofluorescence, fluorescein angiography, and spectral domain optical coherence tomography and angiography were performed. RESULTS: Clinical examination revealed a well-circumscribed, triangular area of retinal graying of about 1-disk diameter in size, located at the border of the temporal macula. This corresponded to a deep scotoma similar in size to the physiologic blind spot on Humphrey visual field 24-2 testing. There was mild hypoautofluoresence of this lesion on autofluorescence, hypofluorescence on fluorescein angiography, and focal attenuation of a small artery just distal to the bifurcation of an artery supplying the involved area. Spectral domain optical coherence tomography through the lesion conveyed hyperreflectivity most prominent in the inner and outer plexiform layers, with extension of the hyperreflectivity into the ganglion cell and inner nuclear layers. Spectral domain optical coherence tomography angiography demonstrated arteriolar and capillary dropout, more pronounced in the superficial retinal layer compared to the deeper retinal layer. At 1-month follow-up, his scotoma improved with monitoring, with reduction from -32 dB to -7 dB on Humphrey visual field testing. There was clinical resolution of the area of graying and decreased hyperreflectivity on spectral domain optical coherence tomography, with atrophy of the inner retina. Spectral domain optical coherence tomography angiography showed progression of arteriolar and capillary dropout, more so in the superficial than in the deep capillary plexus. CONCLUSION: We describe a case of small artery occlusion in a previously healthy patient, 4 days after vaccination against N. meningitidis and yellow fever. Fluorescein angiography yielded greater diagnostic value than OCTA for evaluating the occlusion, whereas spectral domain optical coherence tomography angiography enabled better visualization of capillary dropout and layer-specific assessment. Further research is required to determine whether vaccination in general, or directed specifically at N. meningitidis or yellow fever, is associated with small vessel vasculopathy and the underlying pathogenesis.

High-Resolution 3D Magnetic Resonance Imaging of the Sixth Cranial Nerve: Anatomic and Pathologic Considerations by Segment.

BACKGROUND: Weakness of the sixth cranial nerve is the most common cause of an ocular motor cranial nerve palsy. It is often difficult to identify a corresponding abnormality on neuroimaging to correlate with the clinical examination. EVIDENCE ACQUISITION: High-resolution 3D skull base magnetic resonance imaging (MRI) allows for visualization of the sixth nerve along much of its course and may increase sensitivity for abnormalities in regions that previously were challenging to evaluate. In this review, the authors share their experience with high-resolution imaging of the sixth nerve. RESULTS: For each segment, anatomic features visible on high-resolution imaging are described along with relevant pathologic entities. CONCLUSIONS: We present a segmental approach to high-resolution 3D MRI for evaluation of the sixth nerve from the nuclear to the orbital segment.