Pulfrich Pendulum Phenomenon in Patients With a History of Acute Optic Neuritis

Abstract

The Pulfrich phenomenon is a stereoillusion in which a pendulum swinging at right angles to the line of gaze appears to be describing an elliptical path when absorbing filters are placed in front of one eye. We used two sets of polaroid glasses as adjustable filters. A spot on a modified oscilloscope served at a pendulum bob. Twenty-nine former patients with a history of optic neuritis and visual acuities of greater than or equal to 6/6 in both eyes and twenty-two normal subjects underwent examinations. The patients showed pathological recordings which separated them from the control subjects. The test seems to expose minor residual dysfunction of affected optic nerves where the visual acuity is normalized. This abnormal response when viewing the moving Pulfrich pendulum is probably caused by disturbed neural conduction. The degree of acute visual loss and the time elapsed since the attack did not seem to influence the Pulfrich response. The results may explain why some patients who have recovered from optic neuritis complain of difficulties when viewing moving objects. In addition to the use of Pulfrich illusion test for diagnostic work; i.e. clinical or subclinical attacks of optic neuritis, it can serve as a valuable supplement to the more sophisticated method of visual evoked response.

The Pulfrich effect in the clinic

“…On top of a reduction in retinal illumination, it has been suggested that a unilateral cataract can also cause a spontaneous Pulfrich effect through retinal defocusing, i.e., blurring, which also slows retinocortical transmission and increases visual latency [23]. However, Cetinkaya et al [23,24] Corneal opacity [21] Iatrogenic, e.g., uniocular mydriasis, X-chrom lens [19] Traumatic anisocoria [21] Affecting neural conduction Post retinal detachment repair [21] Macular disease [26,27] Asymmetric pigmentary glaucoma [22] Central pathway conditions Optic neuritis/multiple sclerosis [21,[33][34][35][36][48][49][50] Mid-facial injuries [31,32] Other optic nerve pathologies [28][29][30]51] Pituitary tumours and temporoparietal astrocytomas [38] Anisometropic amblyopia [16] reported that the magnitude of the spontaneous Pulfrich effect in patients with unilateral cataracts did not correlate with visual acuity, but correlated with the presence of binocular symptoms [25]. Indeed, it has been suggested that the presence of the Pulfrich effect may account for visual symptoms in patients with unilateral cataracts that are independent of visual acuity, stereoacuity and contrast sensitivity [23].…”

“…Disorders affecting the retina, including central serous elevation of the macula [26], unilateral epiretinal membrane of the macula [27] and repaired retinal detachment [21], can delay conduction and have been reported to manifest a spontaneous Pulfrich effect associated with increased visual latency. Neural conduction can also be slowed in asymmetric optic nerve pathologies such as optic nerve hypoplasia [28], optic nerve head drusen [29], acute ischaemic optic neuropathy due to a presumed vascular accident [30], traumatic optic neuropathy due to mid-facial injury [31,32], and optic neuritis commonly associated with multiple sclerosis [21,[33][34][35][36].In patients with optic neuritis, the Pulfrich effect may account for difficulties with motion perception even in apparent recovery from optic neuritis, as it can be present due to residual optic nerve defects, and appears not to be related to the extent of acute visual loss and time elapsed since an attack of acute optic neuritis [34]. Interestingly, an asymptomatic inter-ocular signal latency difference in patients with multiple sclerosis can manifest as a spontaneous Pulfrich effect after exercise, presumably due to increased body temperature causing the Uthoff effect [37].…”

Interocular differences in visual latency induced by reduced‐aperture monovision

“…Unilateral wear of such light‐absorbing devices as the X‐Chrom lens, or unilateral mydriasis . The Pulfrich effect (the spontaneous Pulfrich effect) is also found in patients suffering increased latency in one eye due to pathology or trauma or reduced‐aperture monovision . In practical terms these motion‐related spatial distortions mean that patients may experience difficulties in moving about their environment at home, at work or when driving …”

Pulfrich autostereo display with micro-prism array

“…When the interocular delay appears, such noise would show "swirl" frame with depth. Besides, it is found clinically that Pulfrich effect, such as cataract [14], optic neuritis [15], or (nerve) multiple sclerosis [16], could appear without a filter when ocellar optic nerve is damaged. It would result in inconvenient life for the patients, such as not being able to accurately judge the position of an object and the distance of the opposite car.…”