Patterns of Vision Loss in Glaucoma: Large Blind Spots Versus Scattered Missing Points

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Excerpt:

Introduction Glaucoma is a progressive optic neuropathy – damage to the optic nerve and retinal nerve fibers – that slowly steals vision. It is now the world’s second-leading cause of blindness (). Rather than causing blunt vision loss like cataracts, glaucoma typically creates blind spots (called scotomas) and patches of reduced sensitivity in the visual field. Depending on the eye and disease type, these scotomas can look very different. Some glaucoma patients see large regional areas of vision loss (for example, an arc-shaped “slice” or nasal wedge of blindness), while others only have numerous small “peppered” defects scattered across their field. Understanding these patterns helps patients interpret test results and helps doctors predict how the disease may behave. This article will explain why glaucoma produces large blind spots in some cases versus diffuse scattered losses in others, what this means for different glaucoma subtypes and progression, and how these patterns affect daily life, treatment, and monitoring () ().How Glaucoma Causes Visual Field Loss Inside the eye, the retinal ganglion cells send visual information along axons (the retinal nerve fiber layer) to form the optic nerve. In glaucoma, these nerve fibers die off. Because the fibers are organized into bundles (arcuate bundles that arc above and below the blind spot at the optic nerve head), damage tends to follow predictable paths (). For example, an arcuate scotoma follows the path of fibers over the macula, forming an arc-shaped blind region from the blind spot into peripheral field. A nasal step defect appears as an abrupt loss across the horizontal midline into the nasal (inner) field. In contrast, a generalized or diffuse defect involves a more uniform loss of sensitivity across many retinal locations rather than one localized patch () (). In a normal visual field test, each eye has a “blind spot” (where the optic nerve exits the retina) about 15° to the side of central fixation (). Glaucoma adds to this natural blind spot by progressively enlarging it or creating new blind regions elsewhere in the field. Common Patterns of Visual Field Loss Glaucoma visual field loss can broadly be categorized into localized (contiguous) defects and diffuse/scattered defects. Localized defects (large scotomas) – These are relatively large, continuous areas of vision loss that often align with nerve-fiber anatomy. Classic examples include arcuate scotomas (curving from the blind spot toward the nasal field), paracentral scotomas (small defects just next to fixation), nasal steps (a visible step-like loss at the horizontal meridian), and altitudinal defects (loss of an entire upper or lower half of vision). In fact, early glaucoma often produces arcuate or paracentral scotomas and nasal steps along the midline (). For example, one review reported that among patients with primary open-angle glaucoma (POAG), the nasal step was the most frequent early defect, followed by paracentral and arcuate scotomas (). These localized defects respect the anatomy of nerve fiber bundles and typically spare other regions until the disease advances () (). Diffuse or scattered defects (small-point losses) – Other patients show many isolated poi