Purpose
Clinical use of perimetric testing in patients with glaucoma typically assumes that perimetric defects will be less deep for larger than smaller stimuli. However, studies have shown that very large sinusoidal stimuli can yield similar defects as small circular stimuli. In order to provide guidelines for new perimetric stimuli, we tested patients with glaucoma using five different stimuli and compared defects to their patterns of retinal nerve fibre layer (
RNFL
) damage.
Methods
Twenty subjects with glaucoma were imaged with optical coherence tomography (
OCT
) volume scans to allow for en face
RNFL
images and were also tested on a custom perimetry station with five stimuli: Goldmann sizes
III
and V, a two‐dimensional Gaussian blob (standard deviation 0.5°) and a 0.5 cycle degree
−1
sinusoidal grating presented two ways: flickered at 5 Hz, and pulsed for 200 ms instead of flickered. En face
RNFL
images were reviewed with the visual field locations overlaid, and each location was labelled for a patient as either no visible
RNFL
defect or as wedge, slit, edge, or diffuse defect. Nineteen age‐similar controls were tested with the same stimuli to define depth of defect as difference from mean normal. Bland‐Altman analysis was used to test three predictions of neural modelling by making five comparisons.
Results
Bland‐Altman analysis confirmed the three predictions. The flickered sinusoid gave deeper defects in damaged areas than the pulsed sinusoid (
r
= 0.25,
p
< 0.0001). When comparing data for sizes
III
and V there was increased spread of the data in deeper defects in the direction of size
III
having deeper defect (
r
= 0.35,
p
< 0.0001). The size V stimulus yielded shallower defects than a stimulus of similar size but with blurred edges (
r
= 0.20,
p
= 0.0004).
Conclusions
On average, all stimuli produced similar results comparing across type of
RNFL
damage. However, there were systematic patterns consistent with predictions of neural modelling: in damaged areas, depth of defect tended to be greater for the flickered sinusoid than the pulsed sinusoid, greater for the size
III
stimulus than the size V stimulus, and greater for the Gaussian blob than for the size V stimulus.