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Decreased fixation stability of the preferred retinal location in juvenile macular degeneration.

Bethlehem RA, Dumoulin SO, Dalmaijer ES, Smit M, Berendschot TT, Nijboer TC, Van der Stigchel S - PLoS ONE (2014)

Bottom Line: It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision.For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker.In addition, we performed a simulation with the same task in a group of five healthy controls.

View Article: PubMed Central - PubMed

Affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands; Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Macular degeneration is the main cause for diminished visual acuity in the elderly. The juvenile form of macular degeneration has equally detrimental consequences on foveal vision. To compensate for loss of foveal vision most patients with macular degeneration adopt an eccentric preferred retinal location that takes over tasks normally performed by the healthy fovea. It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision. Here, we investigated whether the fixation characteristics of the preferred retinal locus resemble those of the healthy fovea. For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker. The fixation-offset paradigm measures release from fixation under different fixation conditions and has been shown useful to distinguish between foveal and non-foveal fixation. We measured eye-movements in nine healthy age-matched controls and five patients with juvenile macular degeneration. In addition, we performed a simulation with the same task in a group of five healthy controls. Our results show that the preferred retinal locus does not adopt a foveal type of fixation but instead drifts further away from its original fixation and has overall increased fixation instability. Furthermore, the fixation instability is most pronounced in low frequency eye-movements representing a slow drift from fixation. We argue that the increased fixation instability cannot be attributed to fixation under an unnatural angle. Instead, diminished visual acuity in the periphery causes reduced oculomotor control and results in increased fixation instability.

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Displacement during fixation.The start-to-end displacement in degrees of visual angle is shown. Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. This figure shows that patients with JMD (1 degree [M: 0.78 SD: 0.22], 3 degrees [M: 0.69 SD: 0.14]) deviated more from their original fixation at the end of the fixation phase compared to controls in both the normal (1 degree [M: 0.40 SD: 0.08], 3 degrees [M: 0.41 SD: 0.14]) and simulation (1 degree [M: 0.34 SD: 0.12], 3 degrees [M: 0.34 SD: 0.12]) paradigm.
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pone-0100171-g005: Displacement during fixation.The start-to-end displacement in degrees of visual angle is shown. Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. This figure shows that patients with JMD (1 degree [M: 0.78 SD: 0.22], 3 degrees [M: 0.69 SD: 0.14]) deviated more from their original fixation at the end of the fixation phase compared to controls in both the normal (1 degree [M: 0.40 SD: 0.08], 3 degrees [M: 0.41 SD: 0.14]) and simulation (1 degree [M: 0.34 SD: 0.12], 3 degrees [M: 0.34 SD: 0.12]) paradigm.

Mentions: Second, we measured the displacement between the start- and end-point of the eye at the onset of the fixation phase. Here, results show a main effect of Group F(2,16) = 16.904, p<0.001. This effect also seems to be mainly driven by the JMD group as Post-Hoc tests show: JMD>Control (p<0.001) and JMD>Simulation (p<0.001), see figure 5. There was no main effect of Anchorsize, nor an interaction effect on the total displacement. These results confirm that patients with JMD have an unstable fixation pattern even when trials that contained saccades were removed from the analysis.


Decreased fixation stability of the preferred retinal location in juvenile macular degeneration.

Bethlehem RA, Dumoulin SO, Dalmaijer ES, Smit M, Berendschot TT, Nijboer TC, Van der Stigchel S - PLoS ONE (2014)

Displacement during fixation.The start-to-end displacement in degrees of visual angle is shown. Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. This figure shows that patients with JMD (1 degree [M: 0.78 SD: 0.22], 3 degrees [M: 0.69 SD: 0.14]) deviated more from their original fixation at the end of the fixation phase compared to controls in both the normal (1 degree [M: 0.40 SD: 0.08], 3 degrees [M: 0.41 SD: 0.14]) and simulation (1 degree [M: 0.34 SD: 0.12], 3 degrees [M: 0.34 SD: 0.12]) paradigm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4061130&req=5

pone-0100171-g005: Displacement during fixation.The start-to-end displacement in degrees of visual angle is shown. Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. This figure shows that patients with JMD (1 degree [M: 0.78 SD: 0.22], 3 degrees [M: 0.69 SD: 0.14]) deviated more from their original fixation at the end of the fixation phase compared to controls in both the normal (1 degree [M: 0.40 SD: 0.08], 3 degrees [M: 0.41 SD: 0.14]) and simulation (1 degree [M: 0.34 SD: 0.12], 3 degrees [M: 0.34 SD: 0.12]) paradigm.
Mentions: Second, we measured the displacement between the start- and end-point of the eye at the onset of the fixation phase. Here, results show a main effect of Group F(2,16) = 16.904, p<0.001. This effect also seems to be mainly driven by the JMD group as Post-Hoc tests show: JMD>Control (p<0.001) and JMD>Simulation (p<0.001), see figure 5. There was no main effect of Anchorsize, nor an interaction effect on the total displacement. These results confirm that patients with JMD have an unstable fixation pattern even when trials that contained saccades were removed from the analysis.

Bottom Line: It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision.For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker.In addition, we performed a simulation with the same task in a group of five healthy controls.

View Article: PubMed Central - PubMed

Affiliation: Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands; Autism Research Centre, Department of Psychiatry, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Macular degeneration is the main cause for diminished visual acuity in the elderly. The juvenile form of macular degeneration has equally detrimental consequences on foveal vision. To compensate for loss of foveal vision most patients with macular degeneration adopt an eccentric preferred retinal location that takes over tasks normally performed by the healthy fovea. It is unclear however, whether the preferred retinal locus also develops properties typical for foveal vision. Here, we investigated whether the fixation characteristics of the preferred retinal locus resemble those of the healthy fovea. For this purpose, we used the fixation-offset paradigm and tracked eye-position using a high spatial and temporal resolution infrared eye-tracker. The fixation-offset paradigm measures release from fixation under different fixation conditions and has been shown useful to distinguish between foveal and non-foveal fixation. We measured eye-movements in nine healthy age-matched controls and five patients with juvenile macular degeneration. In addition, we performed a simulation with the same task in a group of five healthy controls. Our results show that the preferred retinal locus does not adopt a foveal type of fixation but instead drifts further away from its original fixation and has overall increased fixation instability. Furthermore, the fixation instability is most pronounced in low frequency eye-movements representing a slow drift from fixation. We argue that the increased fixation instability cannot be attributed to fixation under an unnatural angle. Instead, diminished visual acuity in the periphery causes reduced oculomotor control and results in increased fixation instability.

Show MeSH
Related in: MedlinePlus