2020–2021 BCSC Basic and Clinical Science Course™
Chapter 4: The Patient With Decreased Vision: Classification and Management
Clinically, patients with optic neuropathies typically present with visual acuity loss, visual field loss, dyschromatopsia, and an RAPD (in patients with unilateral or asymmetric damage). The ONH may appear normal or acutely swollen; optic atrophy (optic nerve pallor) typically develops 4–6 weeks later, even after vision has recovered.
Visual Field Patterns in Optic Neuropathy
Retinal ganglion cell nerve fibers enter the ONH in 3 major groups (Fig 4-2). Thus, visual field loss attributable to lesions of the optic nerve may be associated with 3 types of fibers (Table 4-2):
papillomacular fibers: cecocentral scotoma (Fig 4-3A, left panel), paracentral scotoma (Fig 4-3A, right panel), and central scotoma (Fig 4-3B)
arcuate fibers: arcuate scotoma (nerve fiber bundle defect) (Fig 4-3C), altitudinal defect (broader region of arcuate fibers) (Fig 4-3D), and nasal (step) defect (temporal portion of arcuate fibers) (Fig 4-3E). These fibers align along the temporal horizontal retinal raphe; damage to them produces defects that do not cross and respect the nasal horizontal meridian
nasal radiating fibers: temporal wedge defect
Blind-spot enlargement results from ONH edema of any cause, due to displacement of the peripapillary retina (Fig 4-3F).
Figure 4-2 Retinal ganglion cell nerve fibers. A, Schematic representation of retinal nerve fiber layer entering the optic nerve head (ONH). The fibers are classified as arcuate (inferior bundle highlighted), papillomacular (long arrow), and nasal radiating (short arrow). B, Humphrey 30-2 perimetry grayscale diagram of the left eye, showing superior arcuate visual field defect corresponding to the inferior arcuate nerve fiber bundle (damage highlighted).
(Part B courtesy of Michael S. Lee, MD.)
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.