Objective:
Saccades are rapid eye movements that shift the centre of highest vision (fovea) to visual targets. They are generated and controlled by a network of cortical and subcortical areas. Dementia with Lewy bodies (DLB) shows prominent subcortical and cortical neurodegenerative changes and might therefore be prone to saccadic eye movement disturbances.
Design:
Comparative study of saccade triggering, suppression and planning in DLB and Alzheimer’s disease (AD) and in elderly healthy controls (controls).
Material and Methods:
Prosaccades (e.g. gap, overlap and predictive tasks) and antisaccades were assessed via electro-oculogram in 48 age and education matched subjects (20 controls, 15 AD, 13 DLB) from the Newcastle MRC prospective cohort study.
Results:
In DLB, mean latency was significantly increased, and mean gain of the first saccade was reduced, compared to controls and AD patients. Furthermore, DLB patients made more erroneous prosaccades towards the targets in the antisaccade task and fewer predictive saccades compared to controls, but not different from AD patients.
| DLB |
AD |
Controls |
DLB vs Controls |
DLB vs AD |
|
| Gap task | |||||
|
Latency (ms) |
274 |
234 |
190 |
p < 0.001 |
p = 0.04 |
|
Gain first saccade |
0.85 |
0.94 |
1.00 |
p = 0.005 |
p = 0.03 |
|
Gain final eye position |
1.04 |
1.07 |
1.07 |
ns |
ns |
| Overlap task | |||||
|
Latency |
484 |
336 |
265 |
p < 0.001 |
p = 0.03 |
|
Gain first saccade |
0.82 |
1.02 |
1.06 |
p = 0.005 |
p = 0.03 |
|
Gain final eye position |
1.01 |
1.08 |
1.09 |
ns |
ns |
| Predictive task | |||||
|
Predicted saccades (%) |
10 |
23 |
47 |
p = 0.002 |
ns |
| Non-predicted saccade | |||||
|
latency |
325 |
265 |
211 |
p < 0.001 |
p = 0.02 |
|
gain first saccade |
0.76 |
1.02 |
1.06 |
p < 0.001 |
p = 0.01 |
|
gain final eye position |
1.00 |
1.09 |
1.05 |
ns |
ns |
| Antisaccades (AS) | |||||
|
Error AS (%) |
47 |
60 |
20 |
p < 0.001 |
ns |
|
Latency correct AS |
623 |
561 |
345 |
p < 0.001 |
ns |
|
Missed targets (%) |
17 |
3 |
0 |
p < 0.001 |
p = 0.02 |
Mann-Whitney-U tests; ns: non-significant difference (two-tailed testing α = 0.05);
gain = patient amplitude/target amplitude; predictive saccades = saccades with latencies <80ms
Conclusion:
The results of this preliminary study show that DLB is associated with a distinct pattern of saccadic eye movement behaviour that is different from that seen in elderly controls and AD patients. Saccadic eye movement assessment may be a promising neuro-physiological tool for the differential diagnosis of degenerative brain disorders.
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