Pulfrich Psychophysical Stereo-Illusion and Visual-Evoked Potentials in Epiretinal Membrane of the Macula

Visual latency in the spontaneous Pulfrich effect

“…More recently the Pulfrich effect has been investigated on six patients with epiretinal membrane of the macula [6]. All perceived the stereo illusion spontaneously, and the direction of the effect was consistent with the side (right or left) of the membrane.…”

“…A spontaneous Pulfrich effect has been reported in association with acute optic neuritis or following recovery from optic neuritis and in those with minor optic nerve damage due to multiple sclerosis [1,3,9,12,15,17,18,22]. More recently it has been shown that the effect is present in many cases of uniocular cataract [16] and in a number of other abnormalities in the visual pathway [2,6,9]. We have shown that many of the disturbing visual symptoms experienced by patients with a spontaneous Pulfrich effect [21] can be eradicated by the provision of a suitable ophthalmic tint to the less affected eye [4].…”

“…The location of the defect causing the spontaneous Pulfrich effect is unknown, but it can be presumed to reside somewhere in the neurological substrate which translates retinal disparity information into stereopsis. A number of earlier studies have compared measures of delay from the Pulfrich effect and from the VEP with differing results [1,6,12,15,20,22]. We were interested to compare measures of interocular delay resulting in a spontaneous Pulfrich effect with those measured directly using VEP recordings in cases of midfacial trauma associated with mild traumatic optic neuropathy.…”

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 that affect neural conduction directly in the central visual pathways, when unilateral or asymmetric, can also give rise to an inter-ocular signal latency difference that manifests as a spontaneous Pulfrich effect. 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].…”