Visual Loss of Uncertain Origin Diagnostic Strategies

H. Wilhelm, U. Schiefer, and E. Zrenner

The practicing ophthalmologist faces a common challenge on a daily basis: A patient's vision is worse than was expected, based on the appearances of the initial examination. Usually, a renewed and more careful examination explains the discrepancy. Often, however, additional examination finds nothing to explain the conflicting findings. Time is limited, and one is tempted to refer the patient to a neurologist or another ophthalmic service. The diagnostic modalities available at the next site often lead to an unguided attempt at diagnosis when it is felt that some sort of explanation for the visual loss must be found. This scenario can be both expensive and dangerous, subjecting the patient to a random wandering through neurodiagnostic procedures. At the end of this process, the patient is unsatisfied and anxiety ridden and returns to the ophthalmologist or seeks the counsel of other physicians or even alternative medicine practitioners. If the ophthalmologist wishes to find the correct diagnosis by the most efficient means, he/she must analyze the clinical findings carefully before referring the patient, to arrive systematically and rationally at a conclusive, problem-oriented working diagnosis.

Diagnostic Strategy in Schematic Form •| Pearl

An impairment of vision will have its source in one of the following categories: optical, macular, neural, chiasmal, or retrochiasmal visual pathway. There can also be an unrecognized developmental amblyopia, an open attempt at malingering, a functional or psychological disorder, or a simple exaggeration of the problem in an attempt to maximize a secondary gain (■ Fig. 2.1). For each of these categories, there are specific guidelines to the tests that will clarify the nature of the problem.

Ruling Out Optical Causes of Reduced Vision

The first crucial datum is the corrected visual acuity. Problems are evident from the start, however, beginning with determination of the best possible correction. Despite the availability of automated refractometers, an experienced examiner can be led down the wrong path. What is more, there are optical problems that cannot be detected by conventional methods of clinical refraction.

Fig. 2.1. How the patient characterizes his or her visual problem depends on the cause of the impairment. For refractive errors, the eye experiences blurring of images and double or ghosting of contrasting contours. The symptoms of macular disease are dominated by micropsia and metamorphopsia, whereas optic neuropathies more commonly are described as having darker images with poor color perception

Fig. 2.1. How the patient characterizes his or her visual problem depends on the cause of the impairment. For refractive errors, the eye experiences blurring of images and double or ghosting of contrasting contours. The symptoms of macular disease are dominated by micropsia and metamorphopsia, whereas optic neuropathies more commonly are described as having darker images with poor color perception

Strategies for the Evaluation of Visual Loss of Unknown Cause

Entity

Finding

Functional testing Morphology Additional testing

Reduced acuity despite best correction

History: current, past, medical, family, social

See also: "Additional diagnostic testing"

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