Neuro-ophthalmology is an academically-oriented subspecialty that merges the fields of neurology and ophthalmology, often dealing with complex systemic diseases that have manifestations in the visual system. Neuro-ophthalmologists initially complete a residency in either neurology or ophthalmology, then do a fellowship in the complementary field. Since diagnostic studies can be normal in patients with significant neuro-ophthalmic disease, [1] a detailed medical history and physical exam is essential, and neuro-ophthalmologists often spend a significant amount of time with their patients.
Common pathology referred to a neuro-ophthalmologist includes afferent visual system disorders (e.g. optic neuritis, optic neuropathy, papilledema, brain tumors or strokes) and efferent visual system disorders (e.g. anisocoria, diplopia, ophthalmoplegia, ptosis, nystagmus, blepharospasm, seizures of the eye or eye muscles, and hemifacial spasm). The largest international society of neuro-ophthalmologists is the North American Neuro-Ophthalmological Society (NANOS), [2] which organizes an annual meeting and publishes the Journal of Neuro-Ophthalmology. Neuro-ophthalmologists are often faculty at large university-based medical centers. Patients often have co-existing diseases in other fields (rheumatology, endocrinology, oncology, cardiology, etc.), thus the neuro-ophthalmologist is often a liaison between the ophthalmology department and other departments in the medical center. [3]
Neuro-ophthalmology focuses on diseases of the nervous system that affect vision, control of eye movements, or pupillary reflexes. Neuro-ophthalmologists often see patients with complex multi-system disease and exotic diagnoses—“zebras” in medical jargon—are not uncommon. Neuro-ophthalmologists are often active teachers in their academic institution, and the first four winners of the prestigious Straatsma American Academy of Ophthalmology teaching awards were neuro-ophthalmologists. [4] Neuro-ophthalmology is mostly non-procedural, however, neuro-ophthalmologists may be trained to perform eye muscle surgery to treat adult strabismus, optic nerve fenestration for idiopathic intracranial hypertension, and botulinum injections for blepharospasm or hemifacial spasm. [5]
At the turn of the 20th century, there was no textbook in the English language on neuro-ophthalmology. In 1906, Dr. William Campbell Posey, Professor of Ophthalmology in the Philadelphia Polyclinic and Dr. William G. Spiller, Professor of Neurology in the University of Pennsylvania, edited The Eye and Nervous System: Their Diagnostic Relations By Various Authors J.B. Lippincott & Co. According to the Preface to this book, "Although it is generally conceded that a knowledge of neurology is indispensable to the ophthalmologist and that an acquaintanceship with ophthalmology is of the greatest service to the neurologist, there is no book in the English language which covers the ground where the two specialties meet." [6]
Frank B. Walsh was a pioneer of neuro-ophthalmology, helping to popularize and develop the field. Walsh was born in Oxbow, Saskatchewan in 1895 and earned a degree from University of Manitoba in 1921. He joined the Wilmer Ophthalmological Institute at Johns Hopkins University and began organizing Saturday morning neuro-ophthalmology conferences. Walsh compiled the first neuro-ophthalmology textbook, which was published in 1947 and has been updated over the years by generations of his students. [7]
Improved functional neuroimaging is paving the way for better understanding, assessment, and management of many neurologic and neuro-ophthalmologic conditions. As our understanding of neuroscience evolves, neuro-ophthalmologists are becoming increasingly better at treatment, rather than only diagnosis, and novel therapies are emerging to treat traditionally vision-devastating disease. [8] For example, clinical trials began in February 2014 to use gene therapy to treat Leber hereditary optic neuropathy, [9] which is one of the first uses of gene therapy in the central nervous system. Progress has also been made in understanding retinal ganglion cell regeneration and in re-establishing synaptic connections from the optic nerve to the brain, [1] more than in other regions of the central nervous system. [10] [11] One of the goals of the National Institutes of Health is to use the visual system as a window to understand neural plasticity and regenerative medicine in the central nervous system, [12] an area of neuroscience that has a promising future and is intimately intertwined with neuro-ophthalmology.
Optic neuritis describes any condition that causes inflammation of the optic nerve; it may be associated with demyelinating diseases, or infectious or inflammatory processes.
The retina is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception. The retina serves a function which is in many ways analogous to that of the film or image sensor in a camera.
In neuroanatomy, the optic nerve, also known as the second cranial nerve, cranial nerve II, or simply CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.
Papilledema or papilloedema is optic disc swelling that is caused by increased intracranial pressure due to any cause. The swelling is usually bilateral and can occur over a period of hours to weeks. Unilateral presentation is extremely rare.
Retinitis pigmentosa (RP) is a member of a group of genetic disorders called inherited retinal dystrophy (IRD) that cause loss of vision. Symptoms include trouble seeing at night and decreasing peripheral vision. As peripheral vision worsens, people may experience "tunnel vision". Complete blindness is uncommon. Onset of symptoms is generally gradual and often begins in childhood.
The National Eye Institute (NEI) is part of the U.S. National Institutes of Health (NIH), an agency of the U.S. Department of Health and Human Services. The mission of NEI is "to eliminate vision loss and improve quality of life through vision research." NEI consists of two major branches for research: an extramural branch that funds studies outside NIH and an intramural branch that funds research on the NIH campus in Bethesda, Maryland. Most of the NEI budget funds extramural research.
The visual field is "that portion of space in which objects are visible at the same moment during steady fixation of the gaze in one direction"; in ophthalmology and neurology the emphasis is mostly on the structure inside the visual field and it is then considered “the field of functional capacity obtained and recorded by means of perimetry”.
The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small blind spot in each eye.
Leber's hereditary optic neuropathy (LHON) is a mitochondrially inherited degeneration of retinal ganglion cells (RGCs) and their axons that leads to an acute or subacute loss of central vision; it predominantly affects young adult males. LHON is transmitted only through the mother, as it is primarily due to mutations in the mitochondrial genome, and only the egg contributes mitochondria to the embryo. Men cannot pass on the disease to their offspring. LHON is usually due to one of three pathogenic mitochondrial DNA (mtDNA) point mutations. These mutations are at nucleotide positions 11778 G to A, 3460 G to A and 14484 T to C, respectively in the ND4, ND1 and ND6 subunit genes of complex I of the oxidative phosphorylation chain in mitochondria.
Anterior ischemic optic neuropathy (AION) is a medical condition involving loss of vision caused by damage to the anterior portion of the optic nerve as a result of insufficient blood supply (ischemia). This form of ischemic optic neuropathy is generally categorized as two types: arteritic AION, in which the loss of vision is the result of an inflammatory disease of arteries in the head called temporal arteritis, and non-arteritic AION, which is due to non-inflammatory disease of small blood vessels. It is in contrast to posterior ischemic optic neuropathy, which affects the retrobulbar portion of the optic nerve.
Blepharospasm is a neurological disorder characterized by intermittent, involuntary spasms and contractions of the orbicularis oculi (eyelid) muscles around both eyes. These result in abnormal twitching or blinking, and in the extreme, sustained eyelid closure resulting in functional blindness.
Dominant optic atrophy (DOA), or autosomal dominant optic atrophy (ADOA), (Kjer's type) is an autosomally inherited disease that affects the optic nerves, causing reduced visual acuity and blindness beginning in childhood. However, the disease can seem to re-present a second time with further vision loss due to the early onset of presbyopia symptoms (i.e., difficulty in viewing objects up close). DOA is characterized as affecting neurons called retinal ganglion cells (RGCs). This condition is due to mitochondrial dysfunction mediating the death of optic nerve fibers. The RGCs axons form the optic nerve. Therefore, the disease can be considered of the central nervous system. Dominant optic atrophy was first described clinically by Batten in 1896 and named Kjer’s optic neuropathy in 1959 after Danish ophthalmologist Poul Kjer, who studied 19 families with the disease. Although dominant optic atrophy is the most common autosomally inherited optic neuropathy (i.e., disease of the optic nerves), it is often misdiagnosed.
The retinal nerve fiber layer (RNFL) or nerve fiber layer, stratum opticum, is part of the anatomy of the eye.
Optic neuropathy is damage to the optic nerve from any cause. The optic nerve is a bundle of millions of fibers in the retina that sends visual signals to the brain.
Optic disc drusen (ODD) are globules of mucoproteins and mucopolysaccharides that progressively calcify in the optic disc. They are thought to be the remnants of the axonal transport system of degenerated retinal ganglion cells. ODD have also been referred to as congenitally elevated or anomalous discs, pseudopapilledema, pseudoneuritis, buried disc drusen, and disc hyaline bodies.
Bonnet–Dechaume–Blanc syndrome, also known as Wyburn-Mason syndrome, is a rare congenital disorder characterized by arteriovenous malformations of the brain, retina or facial nevi. The syndrome has a number of possible symptoms and can, more rarely, affect the skin, bones, kidneys, muscles, and gastrointestinal tract. When the syndrome affects the brain, people can experience severe headaches, seizures, acute stroke, meningism, and progressive neurological deficits due to acute or chronic ischaemia caused by arteriovenous shunting.
Mitochondrial optic neuropathies are a heterogenous group of disorders that present with visual disturbances resultant from mitochondrial dysfunction within the anatomy of the Retinal Ganglion Cells (RGC), optic nerve, optic chiasm, and optic tract. These disturbances are multifactorial, their aetiology consisting of metabolic and/or structural damage as a consequence of genetic mutations, environmental stressors, or both. The three most common neuro-ophthalmic abnormalities seen in mitochondrial disorders are bilateral optic neuropathy, ophthalmoplegia with ptosis, and pigmentary retinopathy.
Chronic relapsing inflammatory optic neuropathy (CRION) is a form of recurrent optic neuritis that is steroid responsive and dependent. Patients typically present with pain associated with visual loss. CRION is a clinical diagnosis of exclusion, and other demyelinating, autoimmune, and systemic causes should be ruled out. An accurate antibody test which became available commercially in 2017 has allowed most patients previously diagnosed with CRION to be re-identified as having MOG antibody disease, which is not a diagnosis of exclusion. Early recognition is crucial given risks for severe visual loss and because it is treatable with immunosuppressive treatment such as steroids or B-cell depleting therapy. Relapse that occurs after reducing or stopping steroids is a characteristic feature.
Alfredo Arrigo Sadun is an American ophthalmologist, academic, author and researcher. He holds the Flora L. Thornton Endowed Chair at Doheny Eye Centers-UCLA and is Vice-Chair of Ophthalmology at UCLA.