Migraine photophobia originating in cone-driven retinal pathways

Migraine headache is uniquely exacerbated by light. Using psychophysical assessments in patients with normal eyesight we found that green light exacerbates migraine headache significantly less than white, blue, amber or red lights. To delineate mechanisms, we used electroretinography and visual evoked potential recording in patients, and multi-unit recording of dura- and light-sensitive thalamic neurons in rats to show that green activates cone-driven retinal pathways to a lesser extent than white, blue and red; that thalamic neurons are most responsive to blue and least responsive to green; and that cortical responses to green are significantly smaller than those generated by blue, amber and red lights. These findings suggest that patients' experience with colour and migraine photophobia could originate in cone-driven retinal pathways, fine-tuned in relay thalamic neurons outside the main visual pathway, and preserved by the cortex. Additionally, the findings provide substrate for the soothing effects of green light.

An Experimental Animal Model of Photodynamic Optic Nerve Head Injury (PONHI)

PURPOSE

Anterior ischemic optic neuropathy (AION) is the most common cause of non-glaucomatous optic nerve head (ONH) injury among older adults. AION results from a sudden ischemic insult to the proximal portion of the optic nerve, typically leading to visual impairment. Here, we present an experimental model of photodynamically induced ONH injury that can be used to study neuroprotective modalities.

METHODS

Intraperitoneal injection of mesoporphyrin IX was followed by photodynamic treatment of the ONH in one eye of Brown-Norway rats; the fellow eye received the reverse sequence as a sham control. Fluorescein angiography (FA), spectral domain optical coherence tomography (SD-OCT), and visual evoked potential (VEP) recordings were performed at different time points following laser treatment. Immunohistochemistry was used to monitor apoptotic cell death (TUNEL) and macrophage infiltration (CD68). Cytokine levels were evaluated using enzyme-linked immunosorbent assay (ELISA).

RESULTS

FA showed early hyperfluorescence and late leakage of the ONH, while SD-OCT revealed optic nerve edema. No leakage or other abnormalities were detected in control eyes. VEPs were significantly reduced in amplitude and showed prolonged responses compared to sham eyes. The number of apoptotic retinal ganglion cells was elevated one day after laser treatment (13.77 ± 4.49, p < 0.01) and peaked on day 7 (57.22 ± 11.34, p < 0.01). ONH macrophage infiltration also peaked on day 7 (101.8 ± 9.8, p < 0.05). ELISAs performed showed upregulation of macrophage chemoattractant protein-1 and macrophage inflammatory protein-2 on days 3 and 1, respectively.

CONCLUSIONS

Photodynamic treatment of the ONH after administration of mesoporphyrin IX leads to macroscopic, histologic, and physiologic evidence of ONH injury. Given the long half-life of mesoporphyrin IX and the ease of intraperitoneal injections, this new model of photodynamically induced ONH injury may be a useful tool for studying optic nerve injury and possible neuroprotective treatments.

Optic neuropathy following retrobulbar injection: a review

A retrobulbar block is a regional anesthetic nerve block in the retrobulbar space. Optic neuropathy following retrobulbar injection is a well-recognized and rare complication of the procedure with an unknown incidence. This article reviews the relevant literature regarding vision loss following this procedure. Mechanisms of injury to the optic nerve as well as methods that can be employed to minimize the risk of optic neuropathy will be explored, including alternatives to retrobulbar anesthesia.

A Rod-Sparing Retinopathy in Bardet-Biedl Syndrome

Bardet-Biedl syndrome is a continuum of disorders characterized by systemic and ocular findings. Retinal abnormalities typically present as diffuse photoreceptor degeneration. Here, we report a novel case that suggests a rod-sparing variant of Bardet-Biedl syndrome.

Ocular flutter as the presenting sign of lung adenocarcinoma

Ocular flutter is a rare ophthalmic finding that could represent paraneoplastic phenomena. In adults it is most commonly associated with small cell lung cancer (SCLC). Most patients also present with other neurological defects. We report the case of a 75-year-old woman who presented with isolated ocular flutter. The ensuing workup was significant for an early lung adenocarcinoma that would not have been biopsied otherwise due to its small size. To our knowledge, this is the first reported case of isolated ocular flutter as the presenting symptom of non-SCLC.

Deprivation amblyopia and congenital hereditary cataract

Amblyopia is a neurodevelopmental disorder of vision associated with decreased visual acuity, poor or absent stereopsis, and suppression of information from one eye.(1,2) Amblyopia may be caused by strabismus (strabismic amblyopia), refractive error (anisometropic amblyopia), or deprivation from obstructed vision (deprivation amblyopia). 1 In the developed world, amblyopia is the most common cause of childhood visual impairment, 3 which reduces quality of life 4 and also almost doubles the lifetime risk of legal blindness.(5, 6) Successful treatment of amblyopia greatly depends on early detection and treatment of predisposing disorders such as congenital cataract, which is the most common cause of deprivational amblyopia. Understanding the genetic causes of congenital cataract leads to more effective screening tests, early detection and treatment of infants and children who are at high risk for hereditary congenital cataract.

The use of fourth-generation optical coherence tomography in multiple sclerosis: a review

Optical coherence tomography (OCT) has been routinely used to obtain high spatial resolution images of the retina and choroid non-invasively. Within the past decade, a fourth-generation OCT device using Fourier domain (FD) analysis has been developed that provides higher velocity and higher axial resolution images with better reproducibility than the previous generation time domain (TD) OCT technology. This review addresses the use of fourth-generation, FD ocular OCT in patients with multiple sclerosis.

Neuro-imaging: a review for the general ophthalmologist

The diagnosis of many neuro-ophthalmic conditions is facilitated with neuro-imaging. The two main modalities are Computed Tomography (CT) and Magnetic Resonance Imaging (MRI). Clinicians who refer patients for either of these techniques must not only know which of them to choose, but also where the imaging should be performed (e.g. brain, orbit), whether or not contrast is indicated, and if angiography should be supplemented. These complexities often result in imaging studies that are either unneeded or unhelpful. The goal of this manuscript is to provide a practical set of guidelines for the general ophthalmologist of how to choose the correct parameters for neuro-imaging studies.

Concurrent acute brain infarcts in patients with monocular visual loss

OBJECTIVE

Embolism from a proximal source to the retinal circulation could be a sign of embolism from the same source to the hemispheric circulation. We sought to determine the frequency of acute brain infarcts on diffusion-weighted imaging (DWI) in patients with monocular visual loss of presumed ischemic origin (MVL).

METHODS

We retrospectively studied 129 consecutive patients with MVL secondary to retinal ischemia. All patients underwent DWI, comprehensive ophthalmologic and neurologic examination, and diagnostic evaluations for the underlying etiology. Statistical analyses explored univariate and multivariate predictors of DWI evidence of acute brain infarcts.

RESULTS

DWI revealed concurrent acute brain infarct(s) in 31 of the 129 patients (24%). The probability of positive DWI was higher in embolic versus nonembolic MVL (28 vs 8%, p = 0.04), in MVL characterized by permanent visual loss versus transient symptoms (33 vs 18%, p = 0.04), and in MVL associated with concurrent hemispheric symptoms versus isolated MVL (53 vs 20%, p < 0.01). Patients with positive DWI were more likely to harbor a major underlying etiology as compared to those with normal DWI (odds ratio, 3.7; 95% confidence interval, 1.5-9.4).

INTERPRETATION

This study demonstrates that MVL does not always represent an isolated disease of the retina; approximately 1 of every 4 patients with MVL demonstrates acute brain infarcts on DWI. Because patients with concurrent brain infarcts are more likely to exhibit a cardiac or vascular source of embolism, imaging evidence of brain injury in patients with MVL may be a useful marker to guide the timing and extent of diagnostic examinations.

Decreased vision and junctional scotoma from pituicytoma

Pituicytomas are rare neoplasms of the sellar region. We report a case of vision loss and a junctional scotoma in a 43-year-old woman caused by compression of the optic chiasm by a pituitary tumor. The morphological and immunohistochemical characteristics of the tumor were consistent with the diagnosis of pituicytoma. The tumor was debulked surgically, and the patient's vision improved.

Isolated bilateral fourth cranial nerve palsies as the presenting sign of hydrocephalus

Midbrain lesions leading to bilateral fourth nerve palsies are typically accompanied by other brainstem symptomatology. Here we report a case of a 29-year-old man with hydrocephalus and significant third ventricle dilation applying pressure on the dorsal midbrain and having as only manifestation isolated, bilateral fourth cranial nerve palsies. This finding, reported now for the first time, could be attributed to a partially working ventriculoperitoneal shunt previously placed to this patient, which was able to sporadically relieve the increases of the intraventricular pressure on the midbrain that would normally lead to other manifestations.

The use of onabotulinum toxin A in the treatment of see-saw nystagmus

See-saw nystagmus (SSN) is an uncommon disorder that consists of cycles in which one eye rises and intorts while the other depresses and extorts, followed by reversal of the pattern. It typically causes debilitating symptoms including oscillopsia that interfere with activities of daily living. There are myriad etiologies, including stroke, tumors, trauma, and multiple sclerosis. Treatment options are limited and are often unsatisfactory. The authors report a case in which targeted injections of onabotulinum toxin A were used to decrease the torsional component of SSN and thus significantly improve the subjective symptoms of oscillopsia in a patient with acquired SSN.

Recurrent isolated sixth nerve palsy after consecutive annual influenza vaccinations in a child

Recurrent sixth nerve palsy in children in the absence of structural or other neurological abnormality is a rare occurrence. We report the case of recurrent isolated sixth (abducens) nerve palsy after consecutive annual influenza vaccinations in an otherwise-healthy 2-year-old boy. Investigations including magnetic resonance imaging of the brain and orbits after each episode failed to reveal any abnormality. The temporal relation to the immunizations supports but does not prove that the influenza immunization regimen was responsible.