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Show Journal of Nairn- Ophthalmology 19( 1): 12, 1999. © 1999 Lippincott Williams & Wilkins, Inc., Philadelphia Short Communication The Pulfrich Phenomenon: Its Symptoms and Their Management Charles J. M. Diaper, M. B., ch. B., F. R. C. S., F. R. c. Ophth, Gordon N. Dutton, M. D., F. R. C. S., F. R. c. Ophth, and Gordon Heron, Ph. D., M. Sc, F. c. Opt We read with interest the paper of M. S. Vaphiades and E. Eggenberger ( 1). They found that in addition to the use of uniocular neutral density filters, the Pulfrich phenomenon could also be elicited by differential external illumination of the two eyes of a test subject. This latter finding has been reported previously ( 2) and is sometimes referred to as the the Lythgoe effect. Such lighting conditions have been postulated as a possible factor in accidents ( 3). The Pulfrich phenomenon is widely accepted as being due to an interocular latency difference between the eyes of an observer, with a variety of causes ( 4). Usually this interocular latency difference is brought about by a reduction in retinal illumination of one eye. In the Lythgoe effect, this interocular latency difference is brought about by increasing the retinal illumination to one eye. A spontaneous Pulfrich phenomenon can be produced in any condition in which nerve conduction is slower on one side ( e. g., optic neuritis) or in which there is pathology causing an interocular retinal illumination difference ( e. g., uniocular cataract). In our experience, the Pulfrich phenomenon is best elicited clinically with the patient viewing a weighted line ( plumb line or fishing weight on a length of line) swinging in the frontal plane approximately 50 to 100 cm away from the face at approximately one cycle per second. The line can then be swung in a parasagittal plane to ' go over' the patient's shoulder on one side and then on the other. It can then be swung obliquely across the midline, aiming at the opposite shoulder. As well as the ellipsoid movement perceived for movement seen in the frontal plane, the other pendulum vectors cause the patient to flinch away from the pendulum as it is swung toward the side with the longer latency. This occurs because the apparent pathway of the pendulum appears to curve inward to hit the head ( 4,5). The spontaneous Pulfrich effect can be debilitating with the symptoms as listed in Table 1, but can be alleviated by the use of an appropriate tint placed in front of the ' good' eye. The density of the ophthalmic tint is Manuscript received July 16, 1998; accepted September 1, 1998. From Tcnnct Institute ( C. J. M. D., G. N. D.), Gartnavel General Hospital, and Glasgow Caledonian University ( G. H.), Glasgow. Address correspondence to C. J. M. Diaper, 4/ 2, 15 Clarendon Street, Glasgow, G20 7QP. TABLE 1. Common visual problems experienced by patients with the spontaneous Pulfrich phenomenon Situation Problems Driving Oncoming traffic or parked cars appear to curve in toward the driver* Difficulty with parking* Walking Difficulty crossing roads: " cars appear nearer than they are" Difficulty in crowds: " I appear to be walking into people" In the home Difficulty placing keys into locks and crockery onto shelves Doorways appear to move as they are approached and may appear too low Misjudgement when pouring out liquids Difficulty placing the needle when doing needlepoint or sewing * Depends on eye affected and the side of road that is driven on. subjectively chosen to neutralize the spontaneous Pulfrich phenomenon, and we have found that the provision of this tint in either spectacles or contact lenses removes or reduces the visually disturbing symptoms ( 5,6). Although the phenomenon is widely reported in the ophthalmologic and neurologic literature and is recognized by clinicians, its amelioration with a uniocular tint seems to be less well disseminated into clinical practice. We wish to remind colleagues of the possibility of removing the unpleasant and sometimes alarming symptoms that frequently accompany the spontaneous Pulfrich phenomenon. Our clinical experience over the past few years testifies to the effectiveness and simplicity of this remedy ( 6). REFERENCES 1. Vaphiadaes MS, Eggenberger E. The Pulfrich effect and its relationship to retinal illumination. ./ Neuroophthalmol 1997; 17: 240- 2. 2. Lythgoe RJ. Some observations on the rotating pendulum. Nature 1938; 141: 474. 3. Walker JT. Lythgoe's visual stcreophenomenon in the natural environment: a possible factor in air and highway accidents. Hum Factors 1974: 6: 134- 8. 4. Diaper CJM. Pulfrich revisited. Surv Ophthalmol 1997; 41: 493- 9. 5. Heron G, Dutton GN. The Pulfrich phenomenon and its alleviation with a neutral density filter. Br J Ophthalmol 1989; 73: 1004- 8. 6. Heron G, Dutton GN. The management of visual symptoms related to the Pulfrich effect. Optician 1993; 205: 16- 8. 12 |