Bruckner Test Strabismus

Monocular strabismus

Alternating fixation

Significant anisometropia

Difference of less than 2 D

High hyperopia

Hyperopia of less than 3 D

High astigmatism

Astigmatism of less than 2 D

Crowding phenomenon

Dominant eye poorer

Eccentric fixation

Steady central fixation

Ammann test: no further deterioration of acuity when viewing the chart through a neutral density filter (an amblyopic eye behaves as if it is already dark-adapted)

Pathological Ammann test, i.e., there is further deterioration of acuity when viewing the chart through a neutral density filter

D Diopters

D Diopters the patient with an injury or an episode of inflammatory activity plausibly associates the cause of the poor vision. In all likelihood, the event was only a cause for drawing attention to the eye and discovery of its poor acuity. Not uncommonly, the history given by the patient and the patient's family can be useless. Some patients even forget that they have had strabismus surgery. Patient questioning and verification of the information (when possible) is needed.

j| Note

If the Lang stereotest finds evidence of good stereopsis, one can rule out strabismic amblyopia and/or microstrabismus (even though occasional exceptions are found). Bilateral amblyopia must have a convincing cause: very high hyperopia, high corneal astigmatism, ocular malformations. A myopic eye (or the more myopic of a pair) only rarely develops a refractive amblyo-pia if the refractive error is not extreme. A dominant eye cannot be amblyopic relative to its nondominant partner (■ Table 2.3).

Further options for diagnosis of an amblyopia include the Ammann test, tests of the crowding phenomenon, and acuity when reading. In the Ammann test, there will be no further reduction in acuity when a neutral density filter is held before the amblyopic eye - the amblyopic eye behaves as if it were already dark-adapted. The crowding phenomenon compares legibility of single characters as opposed to rows of characters. The mode of fixation can (but should not) show evidence of eccentric fixation. A profound or

Ckner Test

Fig. 2.7. The Brückner test: An interocular difference in the fundus reflexes is seen, signaling the presence of a problem. The possible sources include strabismic malalignment, a defect in the refractive media, or an interocular difference in fundus color (e.g., with high axial myopia or a fundus coloboma)

Fig. 2.7. The Brückner test: An interocular difference in the fundus reflexes is seen, signaling the presence of a problem. The possible sources include strabismic malalignment, a defect in the refractive media, or an interocular difference in fundus color (e.g., with high axial myopia or a fundus coloboma)

absolute central scotoma would exclude amblyopia as the principal cause of visual impairment, and would more commonly be the cause of eccentric fixation.

A quick and very helpful test of strabismic diagnosis is the Brückner test, in which one compares the fundus reflexes from both eyes (■ Fig. 2.7). The nonfixing, strabis-mic eye will have a brighter fundus reflex than its partner. However, a secondary strabismus because of damage to the visual system will also yield a positive Brückner test.

In short, one must use a number of measures for the diagnosis of amblyopia when the history is not clear.

T| Pearl

There is no reliable test to prove or exclude amblyopia. There are, however, numerous tests whose results can make the possibility of amblyopia so improbable that one cannot consider amblyopia as a plausible source of an unexplained visual deficit. The examiner should never be satisfied with a single test, and in cases of doubt should be very reluctant to accept amblyopia as a

Malingering

Simulation of visual loss plays a significant role among the patients attending any ophthalmic clinic, and is probably undetected in a number of cases. A separate chapter has been devoted to this subject (see Chap. 15).

Conclusion

The strategy outlined here should allow the examiner to classify quickly the source of the problem. No single method is certain to be effective. Any objective test can be conducted or interpreted incorrectly. Simply the combination of several different tests and proper attention to the logical context of the case help to ward off a mistaken diagnosis. Of course, a carefully taken history and a thorough oph-thalmologic examination are necessary for correct interpretation of the patient's problem. Not uncommonly, successful analysis of visual loss of an uncertain nature will require the cooperation of several specialty fields. Nonetheless, the ophthalmologist must take part from the very start in the full spectrum of diagnostic studies needed to make a correct diagnosis.

Further Reading

Hayreh SS, Klugman MR, Beri M, Kimura AE, Podhajsky P (1990) Differentiation of ischemic from non-ischemic central retinal vein occlusion during the early acute phase. Graefes Arch Clin Exp Ophthalmol 228: 201-217 Kretschmann U, Seeliger MW, Ruether K, Usui T, Apfelstedt-Sylla E, Zrenner E (1998) Multifocal electroretinography in patients with Stargardt's macular dystrophy. Br J Ophthalmol 82: 267-275 Levatin P (1959) Pupillary escape in disease of the retina or optic nerve.

Arch Ophthalmol 62: 768 Sutter EE, Tran D (1992) The field topography of ERG components in man. I. The photopic luminance response. Vision Res 32: 443-446 Zrenner E (1998) Dysfunktion von Zapfen und Stäbchen. In: Huber A, Kömpf D (eds) Klinische Neuroophthalmologie. Thieme, Stuttgart, pp 239-244

Zrenner E, Wilhelm H, Schiefer U (1993) Differentialdiagnostische Strategien bei unklaren Sehstörungen. Ophthalmologe 90: 104-119

cause.

Chapter 3

Was this article helpful?

0 0
Drug Addiction Report

Drug Addiction Report

You're going to discover so many things on addiction with little effort Not only will you discover the thrill of breaking free from your addiction, but you'll also learn extra bonus tips to actually help other people This new breakthrough book is a guide, really. A guide as a result of years of searching, studying, and scouring hundreds of websites, stores, and magazines.

Get My Free Ebook


Post a comment