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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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Fixation stability during fixation.The fixation stability in squared degrees as measured with a bivariate contour ellipse area (see figures 3B and 3D for an example). Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. The “§” marks a trend. This figure shows that fixation was more unstable in the JMD group (1 degree [M: 0.33 SD: 0.20], 3 degrees [M: 0.44 SD: 0.49]) compared to the healthy control group (1 degree [M: 0.08 SD: 0.02], 3 degrees [M: 0.09 SD: 0.04]). The difference between the JMD group and the simulation group (1 degree [M: 0.07 SD: 0.03], 3 degrees [M: 0.07 SD: 0.02]) was not significant but a Bonferroni corrected p-value of 0.067 might be considered a trend.
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pone-0100171-g006: Fixation stability during fixation.The fixation stability in squared degrees as measured with a bivariate contour ellipse area (see figures 3B and 3D for an example). Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. The “§” marks a trend. This figure shows that fixation was more unstable in the JMD group (1 degree [M: 0.33 SD: 0.20], 3 degrees [M: 0.44 SD: 0.49]) compared to the healthy control group (1 degree [M: 0.08 SD: 0.02], 3 degrees [M: 0.09 SD: 0.04]). The difference between the JMD group and the simulation group (1 degree [M: 0.07 SD: 0.03], 3 degrees [M: 0.07 SD: 0.02]) was not significant but a Bonferroni corrected p-value of 0.067 might be considered a trend.

Mentions: Third, we determined the total fixation area using a BCEA for all time-points during the fixation-phase of the fixation-offset paradigm (Figure 3D & F). The results show that fixation stability as measured with a bivariate contour ellipse during a short fixation phase was significantly different across the three groups F(2,16) = 4.476, p = 0.029, see figure 6. Post-hoc tests show that this effect is mainly caused by the JMD group: JMD>Control (p = 0.047) and that there was no significant effect for the JMD group compared to the simulation JMD>Simulation (p = 0.059). There was no main effect of Anchorsize, nor an interaction effect on the fixation stability. The results remained statistically significant even with the JMD outlier removed (main effect of Group (F2,15) = 11.537, p = 0.001 and Post-Hoc differences: JMD>Control, p = 0.003 and JMD>Simulation, p = 0.001). Again, these results show that patients with JMD have an unstable fixation that cannot directly be related to an unnatural eye-position.


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)

Fixation stability during fixation.The fixation stability in squared degrees as measured with a bivariate contour ellipse area (see figures 3B and 3D for an example). Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. The “§” marks a trend. This figure shows that fixation was more unstable in the JMD group (1 degree [M: 0.33 SD: 0.20], 3 degrees [M: 0.44 SD: 0.49]) compared to the healthy control group (1 degree [M: 0.08 SD: 0.02], 3 degrees [M: 0.09 SD: 0.04]). The difference between the JMD group and the simulation group (1 degree [M: 0.07 SD: 0.03], 3 degrees [M: 0.07 SD: 0.02]) was not significant but a Bonferroni corrected p-value of 0.067 might be considered a trend.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0100171-g006: Fixation stability during fixation.The fixation stability in squared degrees as measured with a bivariate contour ellipse area (see figures 3B and 3D for an example). Significant differences are marked: p<0.001 = ***, p<0.01 = ** & p<0.05 = *. The “§” marks a trend. This figure shows that fixation was more unstable in the JMD group (1 degree [M: 0.33 SD: 0.20], 3 degrees [M: 0.44 SD: 0.49]) compared to the healthy control group (1 degree [M: 0.08 SD: 0.02], 3 degrees [M: 0.09 SD: 0.04]). The difference between the JMD group and the simulation group (1 degree [M: 0.07 SD: 0.03], 3 degrees [M: 0.07 SD: 0.02]) was not significant but a Bonferroni corrected p-value of 0.067 might be considered a trend.
Mentions: Third, we determined the total fixation area using a BCEA for all time-points during the fixation-phase of the fixation-offset paradigm (Figure 3D & F). The results show that fixation stability as measured with a bivariate contour ellipse during a short fixation phase was significantly different across the three groups F(2,16) = 4.476, p = 0.029, see figure 6. Post-hoc tests show that this effect is mainly caused by the JMD group: JMD>Control (p = 0.047) and that there was no significant effect for the JMD group compared to the simulation JMD>Simulation (p = 0.059). There was no main effect of Anchorsize, nor an interaction effect on the fixation stability. The results remained statistically significant even with the JMD outlier removed (main effect of Group (F2,15) = 11.537, p = 0.001 and Post-Hoc differences: JMD>Control, p = 0.003 and JMD>Simulation, p = 0.001). Again, these results show that patients with JMD have an unstable fixation that cannot directly be related to an unnatural eye-position.

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