A 65-year-old male complains of bilateral visual difficulty that has progressed over the last year. Funduscopy reveals small yellow retinal lesions clustered in the macula. Which of the following would you expect most on visual field examination?

Question

A 65-year-old male complains of bilateral visual difficulty that has progressed over the last year.  Funduscopy reveals small yellow retinal lesions clustered in the macula.  Which of the following would you expect most on visual field examination?

Quizplus · Accepted Answer

The macula is a yellowish spot approximately 1.5 mm in diameter located near the center of the retina. It is characterized histologically by the presence of densely packed cones, few overlying cells and no blood vessels. Each macular cone synapses to a single bipolar cell, which, in turn, synapses to a single ganglion cell. Due to this arrangement the visual acuity in the macula, and particularly the fovea, is greater than in any other area of the retina. The neural fibers that serve the macula transmit to an area of the occipital visual cortex that is separate from the area of representation of the peripheral fields (this area is also relatively large in size). Due to this peculiar cortical representation, macular sparing is common in lesions of the occipital cortex. Macular lesions impair central vision and result in central scotomata (Choice E). The term scotoma refers to any visual defect surrounded by a relatively unimpaired field of vision. Scotomas occur due to pathologic processes that involve parts of the retina or optic nerve. Examples of such processes include demyelinating diseases such as multiple sclerosis, diabetic retinopathy and retinitis pigmentosa. Pathologic processes that involve the entire optic nerve lead to monocular blindness. The patient described in this clinical vignette is likely to have macular degeneration (MD). This disorder is frequently age-related, and is the most common cause of blindness in people over 50 years old in the US. Macular degeneration is characterized by progressive loss of central vision due to deposition of fatty tissue (drusen) behind the retina (dry MD) and neovascularization of the retina (wet MD). (Choice A) Homonymous hemianopsia is a loss of vision in the same side of the visual field in both eyes. It occurs due to transection of the contralateral optic tract, the fibers of the visual pathway linking the optic chiasm to the lateral geniculate body. (Choice B) Binasal hemianopsia is a loss of vision in the nasal fields of both eyes. It is caused by pressure to the lateral areas of the optic chiasm. This may result from calcified carotid arteries. (Choice C) Bitemporal hemianopsia is a loss of vision in the temporal fields of both eyes. It is caused by compression of the medial part of the optic chiasm, where the nasal fibers decussate, most commonly by a pituitary adenoma. (Choice D) Arcuate scotomas occur due to damage to a particular region of the optic nerve head. The resulting visual field defect follows the arcuate shape of the nerve fiber pattern. Educational Objective: A scotoma is a visual field defect that occurs due to a pathologic process that involves parts of the retina or the optic nerve resulting in a discrete area of altered vision surrounded by zones of normal vision. Lesions of the macula cause central scotomas.

A 65-Year-Old Male Complains of Bilateral Visual Difficulty That Has