Alessandra Martins

Multifocal pattern electroretinogram does not demonstrate localised field defects in glaucoma.

Purpose: To determine if a multifocal PERG could be recorded in normals, and to examine changes in the multifocal PERG in glaucoma patients. To compare the ability of multifocal PERG and multifocal VEP responses in the same individuals to identify localised field defects in glaucoma. Methods: Using the VERIS ScientificTM system multifocal PERGs were recorded from 19 sites of the visual field according to pseudo-random binary m-sequence. Twenty normals and 15 glaucoma subjects were tested. Multifocal pattern VEPs were also recorded in the glaucoma cases using a cortically scaled stimulus. Results: The second order kernel of the PERG shows a consistent signal. The overall PERG amplitude decreases with age in normals. In glaucoma the PERG amplitude was reduced across the field, but reductions did not correspond to the area of the scotoma. The VEP showed localised signal reductions in all 15 cases of glaucoma. Conclusion: A multifocal PERG can be recorded in normals. However it did not reflect localised ganglion cell losses, whereas the multifocal pattern VEP recorded to a very similar stimulus in the same individual did show losses in the scotoma area.

Effect of pupil size on multifocal pattern visual evoked potentials.

The purpose of this study was to investigate the influence of pupil diameter on the amplitude and latency of multifocal visual evoked potentials (mfVEP). The multifocal objective perimeter (Accumap; Objectivision) was used to stimulate the visual field at 56 sites extending to 32° using a pseudorandom pattern stimulus. The mfVEP were recorded using bipolar occipital electrodes, 7 min/eye. Ten normal subjects were recruited from the community and one eye was randomly selected for testing. The mfVEP were recorded at four different pupil diameters (2 mm, 4 mm, 6 mm, 8 mm), obtained by applying tropicamide (0.5%) or pilocarpine (2%) in different dilutions. Appropriate refractive correction was provided to overcome cycloplegia and achieve a visual acuity of 6/7.5 or better. Analysis revealed that at most pupil diameters the normalized full field amplitude did not show significant variation, except at the most miotic pupil diameter (2 mm), where the amplitude became reduced, based on 2‐way anova and Tukeys T method. There was, however, significant correlation between latency and pupil area (correlation coefficient: upper field −0.63, lower field −0.76). The results suggest that even in the presence of mydriatics or miotics, the mfVEP test can be used to assess diseases that affect amplitude, provided near correction is used. The interpretation of latency, however, must be made with caution, as a borderline conduction defect with a dilated pupil may appear normal.

Effect of fixation tasks on multifocal visual evoked potentials.

Purpose:  This study investigated the effects of cognitive influence on the multifocal visual evoked potential (mVEP) at different levels of eccentricity. Three different foveal fixation conditions were utilized involving varying levels of task complexity. A more complex visual fixation task has been known to suppress peripheral signals in subjective testing.

Effect of check size and stimulation rate on blue-yellow multifocal visual evoked potentials.

Background: To determine the effect of different stimulus frame rates and check sizes on blue−yellow multifocal visual evoked potentials (mVEP).

Retinal and optic nerve changes in glaucoma: From animal study to clinical implication

Animal models of experimental glaucoma provide the ability to longitudinally characterize changes in the optic nerve head and surrounding retinal nerve fiber layer with various imaging modalities and compare them to histomorphometric changes. Analysis of the optic nerve head surface by confocal scanning laser tomography and structures deep to this by spectral domain optical coherence tomography allow for the detection of the earliest structural changes seen in glaucoma. Algorithms utilizing these parameters along with retinal nerve fiber layer measurement are likely to play an important role in the future of glaucoma progression monitoring.

Retinal and optic nerve changes in glaucoma

Animal models of experimental glaucoma provide the ability to longitudinally characterize changes in the optic nerve head and surrounding retinal nerve fiber layer with various imaging modalities and compare them to histomorphometric changes. Analysis of the optic nerve head surface by confocal scanning laser tomography and structures deep to this by spectral domain optical coherence tomography allow for the detection of the earliest structural changes seen in glaucoma. Algorithms utilizing these parameters along with retinal nerve fiber layer measurement are likely to play an important role in the future of glaucoma progression monitoring.