The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task

Abstract

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. Amblyopia is associated with abnormal visual experience (e.g., anisometropia) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears—what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic/non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30 ± 11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28 ± 8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10°) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262 ± 48 ms) and dominant (mean 237 ± 45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226 ± 32 ms) and non-dominant (mean 230 ± 29 ms) eye was not significantly different. By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central retina in subjects with anisometropic amblyopia.

An Unexpected Spontaneous Motion-In-Depth Pulfrich Phenomenon in Amblyopia

“…It seems to us, on the basis of the stimulus dependence of the effect, that the spontaneous Pulfrich phenomenon experienced by a subgroup of amblyopes (those with mild amblyopia and some residual stereopsis) is likely caused by an alteration in temporal summation associated with the processing of information by the amblyopic visual system rather than a simple transmission delay [17][18][19][20]. This processing could involve two conflicting components: an "amblyopic delay" [16,23,38] and a "blur-based acceleration" [41].…”

“…Furthermore, a small percentage (approximately 4%) of mild anisometropic amblyopes who have rudimentary stereopsis experience a spontaneous Pulfrich phenomenon during normal viewing [15]. This is assumed to be due to a delay in the processing of the information coming from the amblyopic eye because of an increased retinocortical transmission time from their amblyopic eye, or because of prolonged neural integration at retinal or cortical sites [16][17][18][19][20]. This delay is observed in the pupillary response to contrast gratings of the amblyopic eye [21,22].…”

Not only amblyopic but also dominant eye in subjects with strabismus show increased saccadic latency

“…Ten subjects with strabismic amblyopia (seven females; mean age 39.4 6 16.3 years) and 12 normal subjects (controls; six females; mean age 36.4 6 13 years) took part in the study. Normal subjects were age matched and selected from the control group that participated in our previous study (Perdziak et al, 2014). Based on a medical interview, all subjects were healthy without any ophthalmological or neurological diseases and none were receiving medications known to affect attention or reaction time.…”

“…Since strabismic and anisometropic amblyopes may show different patterns of visual loss (McKee et al, 2003), different temporospatial characteristics of calcarine activation (Choi et al, 2001), as well as different characteristics of fixational eye movements (Chung, Kumar, Li, & Levi, 2015), we decided to compare the results of the current study with our previous study (Perdziak, Witkowska, Gryncewicz, Przekoracka-Krawczyk, & Ober, 2014) performed on anisometropic amblyopes (where we used the same experimental paradigm and procedure) in order to explore the impact of these two subtypes of amblyopia on the initiation process of delayed saccadic responses.…”

Interocular Differences in Spatial Frequency Influence the Pulfrich Effect

“…Nevertheless, the delay turned out to be longer in the eye viewing Gabor elements of higher spatial frequency and followed a common trend of getting more negative as the spatial frequency ratio increased ( Figure 5B). We attributed the unilateral delay in all conditions to an innate interocular delay in these exceptional subjects [5,[47][48][49][50][51][52]. If some subjects already had a large innate interocular delay, this delay would nonetheless persist even when the eye was shown images with a lower spatial frequency content.…”