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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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Time-course and scatterplot examples for different types of trials.Panels A, C and E show example time-courses of eye-position over time, lines indicate horizontal (red) and vertical (blue) displacement over time. The example time-courses illustrate measurement with (A) and without (C) an intrusive saccade in control subjects and a typical trial without saccades or blinks of a JMD patient (E). Panels B, D and F show the corresponding eye-positions across the entire measurement duration, indicating the effect of saccade and blinks on the displacement spread (Panel B). Displacement was summarized by the BCEA and examples are shown in blue circles in panels D and E. Only trials that did not include these intrusive saccades or blinks were included in the analysis of the BCEA, displacement and power spectral densities.
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pone-0100171-g003: Time-course and scatterplot examples for different types of trials.Panels A, C and E show example time-courses of eye-position over time, lines indicate horizontal (red) and vertical (blue) displacement over time. The example time-courses illustrate measurement with (A) and without (C) an intrusive saccade in control subjects and a typical trial without saccades or blinks of a JMD patient (E). Panels B, D and F show the corresponding eye-positions across the entire measurement duration, indicating the effect of saccade and blinks on the displacement spread (Panel B). Displacement was summarized by the BCEA and examples are shown in blue circles in panels D and E. Only trials that did not include these intrusive saccades or blinks were included in the analysis of the BCEA, displacement and power spectral densities.

Mentions: Example eye-movement recordings and BCEA computation are shown in Figure 3. Figure 3 depicts three types of trials. The top trial (3A and 3B) is an example of a trial with an intrusive saccade. The scatterplot (3B) shows how an intrusive saccade influences the spread of the displacement and thus the BCEA and overall displacement. Intrusive saccades can greatly bias the displacement and fixation stability measures and therefore all trials that included intrusive saccades were removed from the remaining analysis. The two other trials show a ‘normal’ time-course (3C) and scatterplot (3D) of a healthy control and a time-course (3E) and scatterplot (3F) of a patient with JMD. In the scatterplots of the included trial types (3D and 3F) examples of a BCEA are shown.


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)

Time-course and scatterplot examples for different types of trials.Panels A, C and E show example time-courses of eye-position over time, lines indicate horizontal (red) and vertical (blue) displacement over time. The example time-courses illustrate measurement with (A) and without (C) an intrusive saccade in control subjects and a typical trial without saccades or blinks of a JMD patient (E). Panels B, D and F show the corresponding eye-positions across the entire measurement duration, indicating the effect of saccade and blinks on the displacement spread (Panel B). Displacement was summarized by the BCEA and examples are shown in blue circles in panels D and E. Only trials that did not include these intrusive saccades or blinks were included in the analysis of the BCEA, displacement and power spectral densities.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0100171-g003: Time-course and scatterplot examples for different types of trials.Panels A, C and E show example time-courses of eye-position over time, lines indicate horizontal (red) and vertical (blue) displacement over time. The example time-courses illustrate measurement with (A) and without (C) an intrusive saccade in control subjects and a typical trial without saccades or blinks of a JMD patient (E). Panels B, D and F show the corresponding eye-positions across the entire measurement duration, indicating the effect of saccade and blinks on the displacement spread (Panel B). Displacement was summarized by the BCEA and examples are shown in blue circles in panels D and E. Only trials that did not include these intrusive saccades or blinks were included in the analysis of the BCEA, displacement and power spectral densities.
Mentions: Example eye-movement recordings and BCEA computation are shown in Figure 3. Figure 3 depicts three types of trials. The top trial (3A and 3B) is an example of a trial with an intrusive saccade. The scatterplot (3B) shows how an intrusive saccade influences the spread of the displacement and thus the BCEA and overall displacement. Intrusive saccades can greatly bias the displacement and fixation stability measures and therefore all trials that included intrusive saccades were removed from the remaining analysis. The two other trials show a ‘normal’ time-course (3C) and scatterplot (3D) of a healthy control and a time-course (3E) and scatterplot (3F) of a patient with JMD. In the scatterplots of the included trial types (3D and 3F) examples of a BCEA are shown.

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