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Sato A, Nakatani S. Independent bilateral-eye stimulation for gaze pattern recognition based on steady-state pupil light reflex. J Neural Eng 2022; 19. [PMID: 36583387 DOI: 10.1088/1741-2552/acab31] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2022] [Accepted: 12/13/2022] [Indexed: 12/15/2022]
Abstract
Objective:recently, pupil oscillations synchronized with steady visual stimuli were used as input for an interface. The proposed system, inspired by a brain-computer interface based on steady-state visual evoked potentials, does not require contact with the participant. However, the pupil oscillation mechanism limits the stimulus frequency to 2.5 Hz or less, making it hard to enhance the information transfer rate (ITR).Approach:here, we compared multiple conditions for stimulation to increase the ITR of the pupil vibration-based interface, which were called monocular-single, monocular-superposed, and binocular-independent conditions. The binocular-independent condition stimulates each eye at different frequencies respectively and mixes them by using the visual stereoscopic perception of users. The monocular-superposed condition stimulates both eyes by a mixed signal of two different frequencies. We selected the shape of the stimulation signal, evaluated the amount of spectral leakage in the monocular-superposed and binocular-independent conditions, and compared the power spectrum density at the stimulation frequency. Moreover, 5, 10, and 15 patterns of stimuli were classified in each condition.Main results:a square wave, which causes an efficient pupil response, was used as the stimulus. Spectral leakage at the beat frequency was higher in the monocular-superposed condition than in the binocular-independent one. The power spectral density of stimulus frequencies was greatest in the monocular-single condition. Finally, we could classify the 15-stimulus pattern, with ITRs of 14.4 (binocular-independent, using five frequencies), 14.5 (monocular-superimposed, using five frequencies), and 23.7 bits min-1(monocular-single, using 15 frequencies). There were no significant differences for the binocular-independent and monocular-superposed conditions.Significance:this paper shows a way to increase the number of stimuli that can be simultaneously displayed without decreasing ITR, even when only a small number of frequencies are available. This could lead to the provision of an interface based on pupil oscillation to a wider range of users.
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Affiliation(s)
- Ariki Sato
- Graduate School of Sustainability Science, Tottori University, Tottori, Japan
| | - Shintaro Nakatani
- Graduate School of Sustainability Science, Tottori University, Tottori, Japan.,Faculty of Engineering, Tottori University, Advanced Mechanical and Electronic System Research Center, Tottori University, Tottori, Japan
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Jayanetti V, Klistorner AI, Graham SL, Dexter M, Flaherty MP, Jones K, Billson FA, Wilson M, North K, Grigg JR, Fraser CL. Monitoring of optic nerve function in Neurofibromatosis 2 children with optic nerve sheath meningiomas using multifocal visual evoked potentials. J Clin Neurosci 2018; 50:262-267. [PMID: 29398196 DOI: 10.1016/j.jocn.2018.01.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2017] [Accepted: 01/05/2018] [Indexed: 11/19/2022]
Abstract
Monitoring optic nerve sheath meningiomas (ONSM) in Neurofibromatosis type 2 (NF2) patients remains difficult. Other ocular manifestations of NF2 may obscure ophthalmic assessment of optic nerve function in these patients. Serial magnetic resonance imaging (MRI) used to assess the optic nerve is not without limitations, being expensive and often requiring general anaesthetic in children, with associated risks. This study was undertaken to describe the use of multifocal visual evoked potentials (multifocal VEP, mfVEP) in the regular monitoring of NF2 patients with ONSM. This study involved three NF2 patients with ONSM who undertook mfVEP testing at an academic ophthalmic centre. Same day mfVEP and routine ophthalmic testing were undertaken. Topographical function of the optic nerve was assessed, utilising tools such as asymmetry deviation and accumap severity index. Results were assessed alongside MRI and visual acuity (VA). From the three patients, five eyes had ONSMs, of which two caused unilateral blindness. The remaining three affected eyes had initial VAs 6/6, 6/24, and 6/18. Over follow up, ranging from 5 to 12 years, all tumours progressed, and VA declined for all patients. Multifocal VEP detected optic nerve functional loss corresponding with visual decline. This case series suggests mfVEP is effective in the objective topographic monitoring of optic nerve function in NF2 patients with ONSM. Due also to its safety in a paediatric population, the test may be considered in the routine monitoring of these patients, to be used to assist regular ophthalmic review and MRI scans.
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Affiliation(s)
- V Jayanetti
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia.
| | - A I Klistorner
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia
| | - S L Graham
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia; Macquarie University, Australia
| | - M Dexter
- The Department of Neurosurgery, The Children's Hospital Westmead, Australia
| | - M P Flaherty
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia; The Department of Ophthalmology, The Children's Hospital Westmead, Australia
| | - K Jones
- The Department of Clinical Genetics, The Children's Hospital Westmead, Australia
| | - F A Billson
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia
| | - M Wilson
- The Department of Clinical Genetics, The Children's Hospital Westmead, Australia
| | - K North
- Murdoch Institute, Australia
| | - J R Grigg
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia; The Department of Ophthalmology, The Children's Hospital Westmead, Australia
| | - C L Fraser
- Save Sight Institute Discipline of Ophthalmology, The University of Sydney, Australia
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Mousa MF, Cubbidge RP, Al-Mansouri F, Bener A. The role of hemifield sector analysis in multifocal visual evoked potential objective perimetry in the early detection of glaucomatous visual field defects. Clin Ophthalmol 2013; 7:843-58. [PMID: 23690675 PMCID: PMC3656925 DOI: 10.2147/opth.s44009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Objective The purpose of this study was to examine the effectiveness of a new analysis method of mfVEP objective perimetry in the early detection of glaucomatous visual field defects compared to the gold standard technique. Methods and patients Three groups were tested in this study; normal controls (38 eyes), glaucoma patients (36 eyes), and glaucoma suspect patients (38 eyes). All subjects underwent two standard 24-2 visual field tests: one with the Humphrey Field Analyzer and a single mfVEP test in one session. Analysis of the mfVEP results was carried out using the new analysis protocol: the hemifield sector analysis protocol. Results Analysis of the mfVEP showed that the signal to noise ratio (SNR) difference between superior and inferior hemifields was statistically significant between the three groups (analysis of variance, P < 0.001 with a 95% confidence interval, 2.82, 2.89 for normal group; 2.25, 2.29 for glaucoma suspect group; 1.67, 1.73 for glaucoma group). The difference between superior and inferior hemifield sectors and hemi-rings was statistically significant in 11/11 pair of sectors and hemi-rings in the glaucoma patients group (t-test P < 0.001), statistically significant in 5/11 pairs of sectors and hemi-rings in the glaucoma suspect group (t-test P < 0.01), and only 1/11 pair was statistically significant (t-test P < 0.9). The sensitivity and specificity of the hemifield sector analysis protocol in detecting glaucoma was 97% and 86% respectively and 89% and 79% in glaucoma suspects. These results showed that the new analysis protocol was able to confirm existing visual field defects detected by standard perimetry, was able to differentiate between the three study groups with a clear distinction between normal patients and those with suspected glaucoma, and was able to detect early visual field changes not detected by standard perimetry. In addition, the distinction between normal and glaucoma patients was especially clear and significant using this analysis. Conclusion The new hemifield sector analysis protocol used in mfVEP testing can be used to detect glaucomatous visual field defects in both glaucoma and glaucoma suspect patients. Using this protocol, it can provide information about focal visual field differences across the horizontal midline, which can be utilized to differentiate between glaucoma and normal subjects. The sensitivity and specificity of the mfVEP test showed very promising results and correlated with other anatomical changes in glaucomatous visual field loss. The intersector analysis protocol can detect early field changes not detected by the standard Humphrey Field Analyzer test.
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Affiliation(s)
- Mohammad F Mousa
- Department of Ophthalmology, Hamad Medical Corporation, Doha, Qatar
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Clinical use of multifocal visual-evoked potentials in a glaucoma practice: a prospective study. Doc Ophthalmol 2012; 125:1-9. [PMID: 22476612 DOI: 10.1007/s10633-012-9324-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 03/16/2012] [Indexed: 10/28/2022]
Abstract
PURPOSE To test a framework that describes how the multifocal visual-evoked potential (mfVEP) technique is used in a particular glaucoma practice. METHODS In this prospective, descriptive study, glaucoma suspects, ocular hypertensives and glaucoma patients were referred for mfVEP testing by a single glaucoma specialist over a 2-year period. All patients underwent standard automated perimetry (SAP) and mfVEP testing within 3 months. Two hundred and ten patients (420 eyes) were referred for mfVEP testing for the following reasons: (1) normal SAP tests suspected of early functional loss (ocular hypertensives, n = 43; and glaucoma suspects on the basis of suspicious optic disks, n = 52); (2) normal-tension glaucoma patients with suspected central SAP defects (n = 33); and (3) SAP abnormalities needing confirmation (n = 82). RESULTS All the glaucoma suspects with normal SAP and mfVEP results remained untreated. Of those with abnormal mfVEP results, 68 % (15/22) were treated because the abnormal regions on the mfVEP were consistent with the abnormal regions seen during clinical examination of the optic disk. The mfVEP was abnormal in 86 % (69/80) of eyes with glaucomatous optic neuropathy and SAP damage, even though it did not result in an altered treatment regimen. In NTG patients, the mfVEP showed central defects in 44 % (12 of 27) of the eyes with apparently normal central fields and confirmed central scotomata in 92 % (36 of 39), leading to more rigorous surveillance of these patients. CONCLUSIONS In a clinical practice, the mfVEP was used when clinical examination and subjective visual fields provided insufficient or conflicting information. This information influenced clinical management.
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De Moraes CG, Ketner S, Teng CC, Ehrlich JR, Raza AS, Liebmann JM, Ritch R, Hood DC. Beta-zone parapapillary atrophy and multifocal visual evoked potentials in eyes with glaucomatous optic neuropathy. Doc Ophthalmol 2011; 123:43-50. [PMID: 21735265 DOI: 10.1007/s10633-011-9280-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2011] [Accepted: 06/23/2011] [Indexed: 10/18/2022]
Abstract
We investigated changes in multifocal visual evoked potential (mfVEP) responses due to beta-zone parapapillary atrophy (ßPPA). Patients with glaucomatous optic neuropathy (GON) with or without standard achromatic perimetry (SAP) abnormalities were referred for mfVEP testing during a 2-year period. Eyes with good quality optic disc stereophotographs and reliable SAP results were included. The mfVEP monocular mean latency delays (ms) and amplitudes (SNR) were analyzed. Age, SAP mean deviation (MD), pattern standard deviation (PSD), and spherical equivalent (SE) were analyzed in the multivariate model. Generalized estimated equations were used for comparisons between groups after adjusting for inter-eye associations. Of 394 eyes of 200 patients, 223 (57%) had ßPPA. The ßPPA eyes were older (59.6 ± 13.7 vs. 56.5 ± 13.7 year, P = 0.02), more myopic (-4.0 ± 3.5 vs. -1.3 ± 3.5 D, P < 0.01), and had poorer SAP scores (MD: -4.9 ± 5.2 vs. -2.6 ± 5.2 dB, P < 0.01; PSD: 4.3 ± 2.9 vs. 2.5 ± 3.0 dB, P < 0.01). By univariate analysis, mean latencies were longer in ßPPA eyes (6.1 ± 5.3 vs. 4.0 ± 5.5 ms, P < 0.01). After adjusting for differences in SE, age, and SAP MD, there was no significant difference between the two groups (P = 0.09). ßPPA eyes had lower amplitude log SNR (0.49 ± 0.16 vs. 0.56 ± 0.15, P < 0.01), which lost significance (P = 0.51) after adjusting for MD and PSD. Although eyes with ßPPA had significantly lower amplitudes and prolonged latencies than eyes without ßPPA, these differences were attributable to differences in SAP severity, age, and refractive error. Thus, ßPPA does not appear to be an independent factor affecting mfVEP responses in eyes with GON.
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A method to detect progression of glaucoma using the multifocal visual evoked potential technique. Doc Ophthalmol 2008; 118:139-50. [PMID: 18830654 DOI: 10.1007/s10633-008-9149-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2007] [Accepted: 09/11/2008] [Indexed: 10/21/2022]
Abstract
PURPOSE To describe a method for monitoring progression of glaucoma using the multifocal visual evoked potential (mfVEP) technique. METHODS Eighty-seven patients diagnosed with open-angle glaucoma were divided into two groups. Group I, comprised 43 patients who had a repeat mfVEP test within 50 days (mean 0.9 +/- 0.5 months), and group II, 44 patients who had a repeat test after at least 6 months (mean 20.7 +/- 9.7 months). Monocular mfVEPs were obtained using a 60-sector pattern reversal dartboard display. Monocular and interocular analyses were performed. Data from the two visits were compared. The total number of abnormal test points with P < 5% within the visual field (total scores) and number of abnormal test points within a cluster (cluster size) were calculated. Data for group I provided a measure of test-retest variability independent of disease progression. Data for group II provided a possible measure of progression. RESULTS The difference in the total scores for group II between visit 1 and visit 2 for the interocular and monocular comparison was significant (P < 0.05) as was the difference in cluster size for the interocular comparison (P < 0.05). Group I did not show a significant change in either total score or cluster size. CONCLUSION The change in the total score and cluster size over time provides a possible method for assessing progression of glaucoma with the mfVEP technique.
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Maertz NA, Kim CBY, Nork TM, Levin LA, Lucarelli MJ, Kaufman PL, Ver Hoeve JN. Multifocal visual evoked potentials in the anesthetized non-human primate. Curr Eye Res 2006; 31:885-93. [PMID: 17050280 DOI: 10.1080/02713680600899648] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
PURPOSE To evaluate monkey multifocal visual evoked cortical potentials (mfVEPs) recorded from central and peripheral fields for reliability and isolation from electroretinographic (ERG) activity. METHODS The mfVEP stimulus consisted of a 7-element hexagonal array that subtended 80 degrees of the central visual field. Recordings were made under intravenous pentobarbital sodium (15 mg/kg) anesthesia. Two monkeys with absent optic nerve and ganglion cell function after combined unilateral optic nerve transection and experimental ocular hypertension (ONT/OHT) were followed longitudinally. In a second study, 16 ophthalmologically normal monkeys were tested once. RESULTS Testing of the non-transected eye in two transected animals revealed robust first- and second-order kernel, first slice (K1 and K2.1) mfVEPs. Stimulation of the transected eye revealed no contamination of the mfVEP from the concurrently recorded multifocal ERGs. There was complete separation of the root-mean-square (RMS) mfVEP amplitudes from the transected and the fellow eyes tested repeatedly across a 4- to 17- month period. The largest amplitude mfVEP was generated by the central element; however, mfVEPs were recorded from outside the central 20 degrees element. The 16 normal animals showed waveforms similar to the normal eyes of the ONT/OHT animals both in shape and distribution throughout the visual field. A scalar-product measure showed both K1 and K2.1 mfVEPs from central and some peripheral elements were statistically distinct from noise. CONCLUSIONS mfVEPs can be reliably recorded from non-human primates anesthetized with pentobarbital. Under the recording conditions described, mfVEPs are not contaminated by ERG activity. mfVEPs may be useful in animal models of diseases that differentially affect macular and peripheral visual field responsiveness.
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Affiliation(s)
- Nathan A Maertz
- Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53792-3220, USA
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Graham SL. The effects of glaucoma on the latency of the multifocal visual evoked potential. Br J Ophthalmol 2006; 90:1077-8. [PMID: 16929054 PMCID: PMC1857392 DOI: 10.1136/bjo.2006.097592] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Kim YJ, Yukawa E, Kawasaki K, Nakase H, Sakaki T. Use of multifocal visual evoked potential tests in the objective evaluation of the visual field in pediatric epilepsy surgery. J Neurosurg 2006; 104:160-5. [PMID: 16572632 DOI: 10.3171/ped.2006.104.3.160] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT To evaluate objectively the visual fields of patients with pediatric epilepsy who are uncooperative with perimetry and in whom postoperative visual field deficits are expected, the authors investigated the usefulness of the multifocal visual evoked potential (VEP) method. METHODS Normal waves in multifocal VEP were determined in 21 healthy children (21 eyes) 6 to 15 years of age (mean 11.4 years). Responses from eight sites in each child were divided into four quadrants (superior and inferior temporal and superior and inferior nasal). In each quadrant, two response waves were grouped and averaged. The peak latency and amplitude at approximately 100 msec were used for assessment. In three cases involving patients with epilepsy, multifocal VEP measurements were also recorded and compared with the peak latency and amplitude in the healthy children. In these children, no significant differences were observed in the peak latency of amplitude among four quadrants using one-way analysis of variance. In each patient, multifocal VEP tests showed abnormal waves in the quadrant corresponding to the lesion demonstrated in neuroradiological images. This result was useful in the treatment of choice and the postoperative evaluation. CONCLUSIONS Multifocal VEP tests can be useful in evaluating the visual field of children objectively. They can also be valuable in assessing preoperative visual field defects and revealing changes in the visual field after treatment.
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Affiliation(s)
- Yeong-Jin Kim
- Department of Neurosurgery, Nara Medical University, Kashihara, Japan.
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Klistorner A, Graham SL. Intertest variability of mfVEP amplitude: reducing its effect on the interpretation of sequential tests. Doc Ophthalmol 2006; 111:159-67. [PMID: 16523233 DOI: 10.1007/s10633-005-5363-3] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2005] [Indexed: 10/24/2022]
Abstract
PURPOSE The multi-focal visual evoked potential (mfVEP) has been recently introduced as an alternative to subjective perimetry in detecting visual field defects. This study examines the source of variability in the mfVEP amplitude, and determines the relationship of this variability to the strength of the signal itself across the visual field. It also investigates possible means to reduce the effects of this variability on between-test interpretation to allow for easier detection of progression. METHODS 85 normal subjects participated in the study. The mfVEP was recorded using Accumap (ObjectiVision Pty Ltd, Sydney, Australia). Each subject was tested twice with an interval between visits of 3-4 weeks. Comparison between tests was performed using coefficient of variability (CV). Variability was also analysed using scaling and clustering procedures. RESULTS In the majority of the retinal areas CV fell within 15-20%. Variability increased with eccentricity, but there was no age dependency. There was a significant reduction of variability (by 15.8 +/- 6%, Student's t-test p<0.0001) when a scaling procedure was applied and this was consistent at all eccentricities. A clustering procedure reduced variability on average by a further 18.5 +/- 4.5% (Student's t-test p<0.0001). This result was also consistent at all eccentricities. CONCLUSION Between test comparisons of raw mfVEP traces is limited by a variability of at least 15%. While this variability required the amplitude of the individual VEP signal to change by 30-40% in order to detect progression, scaling and clustering procedures were able to reduce the required change to 20-25%, thus making an interpretation of consecutive test results more clinically viable.
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Affiliation(s)
- A Klistorner
- Department of Ophthalmology, Sydney University, Save Sight Institute, Sydney Eye Hospital, Sydney, NSW, Australia
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Chan HHL, Ng FYF, Chu PHW. Clinical application of mfERG/VEP in assessing superior altitudinal hemifield loss. Clin Exp Optom 2005; 88:253-7. [PMID: 16083420 DOI: 10.1111/j.1444-0938.2005.tb06704.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2004] [Revised: 03/03/2005] [Accepted: 03/17/2005] [Indexed: 11/30/2022] Open
Abstract
Multifocal ERG (mfERG) and multifocal VEP (mfVEP) have been used widely in the investigation of pathological changes or functional variations in the visual system. Altitudinal hemifield loss is a visual field defect that is usually found in patients with ischaemic optic neuropathy (ION). Anterior ischaemic optic neuropathy (AION) is a complex multi-factorial disease and it is difficult to diagnose according to clinical symptoms and signs alone. AION is believed to be caused by an infarction of the optic nerve due to the occlusion of the posterior ciliary arteries. The current report presents a patient diagnosed with non-arteritic AION. In this report, the mfERG findings did not match the results of the visual field test but those of the mfVEP did. After consideration of the visual electrophysiological and visual field results, the defect arises from neither the retina nor the visual pathway behind the optic chiasma. Hence, the optic nerve is the most likely location of the lesion, causing the superior altitudinal hemi-field loss. This report shows that the mfERG and mfVEP techniques can be used for objective visual field assessment to supplement the conventional visual field testing.
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Affiliation(s)
- Henry Ho-lung Chan
- Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China.
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Martins A, Klistorner A, Graham S, Billson F. Effect of fixation tasks on multifocal visual evoked potentials. Clin Exp Ophthalmol 2005; 33:499-504. [PMID: 16181276 DOI: 10.1111/j.1442-9071.2005.01069.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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. METHODS Twenty normal subjects had monocular mVEPs recorded using the AccuMap objective perimeter. This allowed simultaneous stimulation of 58 segments of the visual field to an eccentricity of 24 degrees. The mVEP was recorded using three different fixation conditions in random order. During task 1 the subject passively viewed the central fixation area. For task 2 alternating numbers were displayed within the fixation area; the subject on viewing the number '3' in the central fixation area indicated recognition by pressing a button. Throughout task 3, numbers were displayed as in task 2. The subject had the cognitive task of summating all the numbers. RESULTS Analysis revealed that the increased attention and concentration demanded by tasks 2 and 3 in comparison with task 1 resulted in significantly enhanced central amplitudes of 9.41% (Mann-Whitney P = 0.0002) and 13.45% (P = 0.0002), respectively. These amplitudes became reduced in the periphery and approached those of task 1, resulting in no significant difference between the three tasks. Latencies demonstrated no significant difference between each task nor at any eccentricity (P > 0.05). As the complexity of each task increased the amount of alpha rhythm was significantly reduced. CONCLUSIONS Our findings indicate that task 1 required a minimal demand of cognition and was associated with the greatest amount of alpha rhythm. It was also the most difficult to perform because of loss of interest. The other two tasks required a greater demand of higher order cognitive skills resulting in significantly enhanced amplitudes centrally and the attenuation of alpha rhythm. Therefore, amplitudes are increased around the area of attention.
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Affiliation(s)
- Alessandra Martins
- Save Sight Institute, Department of Ophthalmology and Eye Health, University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia.
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Abstract
Despite important refinements that have improved quantitation and shortened test time, modern perimetry remains relatively insensitive and plagued by high test-retest variability. Some novel methods, though not yet fully vetted, offer the promise of improving sensitivity and reducing variability.
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Affiliation(s)
- Michael Wall
- University of Iowa, College of Medicine, Department of Neurology, Veterans Administration Medical Center, Iowa City, IA 52246, USA.
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Martins A, Klistorner A, Graham S, Billson F. Effect of check size and stimulation rate on blue-yellow multifocal visual evoked potentials. Clin Exp Ophthalmol 2004; 32:270-4. [PMID: 15180839 DOI: 10.1111/j.1442-9071.2004.00815.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND To determine the effect of different stimulus frame rates and check sizes on blue-yellow multifocal visual evoked potentials (mVEP). METHODS Subjects were examined at the Save Sight Institute at the University Sydney. Experiment 1 involved five adult subjects who underwent binocular stimulation by the Accumap multifocal objective perimeter. The eyes were stimulated with a cortically scaled dartboard pattern consisting of isoluminant blue and yellow checks. These were arranged in three concentric rings extending to an eccentricity of 26 degrees in the visual field. The stimulus pattern was driven by binary sequences resulting in pseudorandom binary exchange of two opposite checkerboard patterns at each of the 32 sites in the visual field. The mVEP were recorded at two different rates of display of the pattern stimulus. In experiment 2, mVEP were tested on 10 normal subjects. Each of the 36 stimulation sites contained a checkerboard pattern of 20, 30, 42 or 56 checks/site, the stimulation pattern was displayed at the optimum rate found in experiment 1. The size of the checks was inversely proportional to the number of checks per site. RESULTS In experiment 1, the slow frame rate significantly increased the average amplitude throughout the field tested by 50 +/- 10.1% (P = 0.001). Latency was significantly shortened by 6.3% (P < 0.01). In experiment 2, the average amplitude peaked at 30 checks per segment; however, this was only calculated to be significantly different from the smallest check size (F(crit range 4,27) = 0.09 P < 0.05, anova, Tukey's T method). A similar difference was found in ring 1 (F(crit range 4,27) = 0.09, P < 0.05, anova, Tukey's T method). In ring 2, however, there was also a significant difference between 56 checks and 20, 30 and 42 (F(crit range 4,27) = 0.09, anova, P < 0.05). Altering the check sizes did not significantly affect the amplitudes in ring 3. The latencies were not significantly modified by altering check size at any eccentricity. CONCLUSIONS These findings suggest that slowing the stimulation rate and displaying 30 checks per stimulation segment optimizes the blue-yellow mVEP stimulus.
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Affiliation(s)
- Alessandra Martins
- Save Sight Institute, Department of Ophthalmology and Eye Health, University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia.
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Martins A, Balachandran C, Klistorner AI, Graham SL, Billson FA. Effect of pupil size on multifocal pattern visual evoked potentials. Clin Exp Ophthalmol 2003; 31:354-6. [PMID: 12880463 DOI: 10.1046/j.1442-9071.2003.00669.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
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 degrees using a pseudo-random 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 Tukey's 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.
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Affiliation(s)
- Alessandra Martins
- Save Sight Institute, Department of Clinical Ophthalmology and Eye Health, University of Sydney, Sydney Eye Hospital, Sydney, New South Wales, Australia.
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Chan HL, Tam WK, Chen CL, Ng NC. The detection of small simulated field defects using multifocal VEPs. Ophthalmic Physiol Opt 2003; 23:205-12. [PMID: 12753476 DOI: 10.1046/j.1475-1313.2003.00108.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
INTRODUCTION The multifocal visual-evoked potential (mfVEP) has been widely investigated in the study of diseases of the visual system. However, the sensitivity of the mfVEP in objective detection of field defects has not been determined. This study investigates the variation of the mfVEP responses whilst simulating field defects by using different sizes of mask on the stimulus pattern. METHODS Simulated field defects of four different sizes (2, 3, 5, and 7 degrees) at two different eccentricities (10 and 16 degrees) were generated on a standard mfVEP dartboard stimulus using opaque masks. These masks were placed at the centre of each dartboard sector and the modified stimuli were used to elicit mfVEPs from 10 normal subjects. The response densities and latencies of N1, P1 of the mfVEP were compared, without and with small simulated field defects. RESULTS The minimum size of simulated field defect causing significant response density reduction in P1 and N1 was 5 degrees at both retinal eccentricities. N1 showed similar reduction in response density at both retinal eccentricities, but P1 showed larger reduction at the 10-degree location than at the 16-degree location. There was no change in latencies with simulated field defect at either location. CONCLUSIONS The mfVEP is only sensitive to a simulated field defect equal to or larger than 5 degrees in diameter, and mfVEP has greater sensitivity at 10-degree eccentricity than at 16-degree eccentricity.
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Affiliation(s)
- H L Chan
- Department of Optometry and Radiography, The Hong Kong Polytechnic University, Hong Kong SAR, China.
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Goldberg I, Graham SL, Klistorner AI. Multifocal objective perimetry in the detection of glaucomatous field loss. Am J Ophthalmol 2002; 133:29-39. [PMID: 11755837 DOI: 10.1016/s0002-9394(01)01294-6] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
PURPOSE To test the ability of a new type of multifocal objective perimetry to identify glaucomatous visual field defects. METHODS A multichannel visual evoked potential was recorded using the ObjectiVision Accumap perimeter. One hundred patients (age, 62.2 +/- 9.8 years, mean MD -6.5 +/- 4.17 dB) with open-angle glaucoma and confirmed glaucomatous visual field defects were tested and compared with the normal database of 100 normal subjects (age, 58.9 +/- 10.7 years). Both eyes were tested, but for determining sensitivity the eye with the lesser field defect was chosen if both qualified. The amplitude and intereye asymmetry coefficient for each zone of the field were calculated. A mean amplitude and multifocal objective perimetry severity index was calculated for each subject. RESULTS In 95 of 100 (95%) patients with glaucoma Humphrey field defects were correlated with visual evoked potential amplitude reductions identifying a cluster of three or more abnormal zones. In two of five remaining patients with glaucoma the defect was detected on the intereye asymmetry analysis. Topographic location was well correlated with Humphrey fields. Mean amplitude was significantly reduced in 86 of the glaucoma cases (86%). The glaucoma severity index was abnormal in 93 glaucoma cases and showed a correlation with Humphrey MD (r = 0.67 right eyes, 0.69 left eyes). In 37 glaucoma cases with no scotoma by definition in the fellow eye, 22 (59.4%) had an abnormal multifocal objective perimetry, whereas only eight had some other aspect of their Humphrey visual field flagged as abnormal. CONCLUSIONS Multifocal objective perimetry can assess the visual field and identify glaucomatous visual field defects. It may have the potential for identifying defects earlier than conventional perimetry.
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Affiliation(s)
- Ivan Goldberg
- Save Sight Institute, Department of Ophthalmology, Sydney University, Sydney, Australia
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Fortune B, Johnson CA, Cioffi GA. The Topographic Relationship Between Multifocal Electroretinographic and Behavioral Perimetric Measures of Function in Glaucoma. Optom Vis Sci 2001; 78:206-14. [PMID: 11349928 DOI: 10.1097/00006324-200104000-00009] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
PURPOSE To study the spatial relationship between local functional abnormalities found using multifocal electroretinography (MERG) and those measured using standard automated perimetry (SAP) in a group of glaucoma patients with well-defined, localized visual field loss. METHODS MERG's were measured for 15 patients with longstanding, stable, localized SAP visual field loss and for 27 normal controls using VERIS Science (EDI, San Mateo, CA). Most glaucoma patients had substantial asymmetry of visual field defects across the horizontal midline so that within-eye comparisons of MERG changes could be made in addition to comparisons between glaucoma and healthy, aged-matched controls. RESULTS For the glaucoma patient group as a whole, conventional measurements of MERG responses, such as peak-to-trough amplitude, peak implicit time, and scalar-product density, did not reveal abnormalities that spatially corresponded to local sensitivity losses determined by SAP visual field thresholds. Some of the patients had MERG abnormalities (e.g., reduced amplitudes) in areas of advanced SAP visual field loss that indicated local retinal dysfunction. On average, glaucoma patients were missing a MERG component that resembled the optic nerve head component as described by Sutter and Bearse. CONCLUSIONS Different MERG components may be affected at different stages of glaucoma, perhaps reflecting a diversity of pathophysiologic mechanisms. This may complicate spatial and temporal relationships between abnormalities found using the MERG and behavioral perimetry, particularly when conventional measurements of MERG responses are used to characterize a diverse patient group/disease.
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Affiliation(s)
- B Fortune
- Discoveries in Sight Research Laboratories, Devers Eye Institute, Portland, Oregon 97232, USA.
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Kretschmann U, Bock M, Gockeln R, Zrenner E. Clinical applications of multifocal electroretinography. Doc Ophthalmol 2001; 100:99-113. [PMID: 11142751 DOI: 10.1023/a:1002775518141] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The multifocal ERG using the m-sequence stimulation technique allows the derivation of 61 - 241 local ERG signals in a central visual field of about 60 degree diameter in a short time between 4 and 16 min. A recording in a light adapted state offers local information comparable to cone responses in the full-field ERG. Retinal functional losses due to regional disorders in outer retinal layers can be described in detail with this technique. In maculopathies decreased or absent central ERGs are found surrounded by normal ERG. The extent of the central lesion can be estimated. In diseases of the outer retina the pattern of distribution of multifocal ERG activity is similar to the the pattern of the visual field defect. In addition to decreased ERG amplitudes a delay of implicit time may be an important sign of pathology, i.e. the pronounced delay of implicit times in the periphery in retinitis pigmentosa and the implicit time delays in regions associated with retinal edema like CRVO and cystoid macula edema in intermediate uveitis. No simple correlation of the first order kernel multifocal ERG and field defects could be found in disorders of the ganglion cell layer. The multifocal ERG is therefore useful in the differential diagnosis of retinal and optic nerve diseases.
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Affiliation(s)
- U Kretschmann
- University Eye Hospital, Dept. of Pathophysiology of Vision and Neuro-Ophthalmology, Tübingen, Germany
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Klistorner AI, Graham SL, Martins A. Multifocal pattern electroretinogram does not demonstrate localised field defects in glaucoma. Doc Ophthalmol 2001; 100:155-65. [PMID: 11142744 DOI: 10.1023/a:1002772520539] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
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 Scientific 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.
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Affiliation(s)
- A I Klistorner
- Save Sight Institute, Department of Ophthalmology, Sydney University, Australia.
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Abstract
PURPOSE Objective perimetry in glaucoma is described using the multifocal pattern visually evoked potential (VEP). A multichannel recording technique was used to improve signal detection in healthy volunteers and assess its ability to detect glaucoma and early changes in patients with suspected glaucoma. DESIGN Prospective, case-control study. PARTICIPANTS Thirty healthy volunteers, 30 patients with suspected glaucoma, and 30 patients with glaucomatous visual field defects were tested. METHOD The VEP was recorded using cortically scaled, multifocal, pseudorandomly alternated pattern stimuli with the VERIS system (Electro-Diagnostic Imaging, Inc., San Francisco, CA). An array of four bipolar occipital electrodes provided four differently oriented channels for simultaneous recording. Signals were compared for different locations within the field up to 26 degrees of eccentricity. Healthy volunteers, patients with suspected glaucoma, and glaucoma patients with established visual field defects were tested, and results were compared with Humphrey visual fields (Humphrey Systems, Dublin, CA) performed on the same day. For reproducibility, five healthy volunteers were each tested on four separate days. The patients with suspected glaucoma and the established glaucoma patients were analyzed for intereye asymmetry of signals, and these data were compared with the asymmetry values of the healthy volunteers. RESULTS Multiple recording channels significantly enhanced the recording of signals from parts of the visual field not reliably sampled with a single channel technique in all healthy volunteers, particularly along the horizontal meridian (P: < 0.001). Signal amplitude did not decline with age in healthy volunteers. Recordings showed good reproducibility within individuals. In all 30 glaucoma patients, the Humphrey visual field defects were well demonstrated by the VEP, and topographic location was strongly correlated (r(s) = 0.79). Despite large interindividual variations in amplitude, scotomas were well demonstrated when compared with normal values. In the patients with suspected glaucoma, smaller changes in signal amplitude could be identified in parts of the field still normal on perimetry using intereye asymmetry analysis. CONCLUSIONS The multifocal, multichannel VEP can objectively detect glaucomatous visual field defects. The nasal step region can be more reliably tested using multiple channels. Asymmetry analysis has the potential to detect early defects. This technique represents a significant step toward the clinical application of objective perimetry in glaucoma.
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Affiliation(s)
- A Klistorner
- Save Sight Institute, Department of Ophthalmology, Sydney University, Sydney, Australia
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Abstract
PURPOSE The objective detection of local visual field defects using multi-focal pattern visual evoked potentials (VEP) has recently been described. The individual waveforms show variable polarity in different parts of the visual field due to underlying cortical convolutions. Normal trace arrays were examined to determine if certain areas of similar waveform could be grouped for analysis, while minimising cancellation of data. METHOD The VEP was assessed using multi-focal pseudo-randomly alternated pattern stimuli which were cortically scaled in size. Bipolar occipital electrodes were used for recording. Waveforms were compared for different locations within the field up to 25 degrees of eccentricity. Analysis of sectors showing similarly shaped waveforms was performed. Twelve normal subjects were studied. RESULT Grouping waveforms by sectors of similar waveform increased the total calculated upper hemifield amplitude by 60%, compared with simple summations of responses for the whole hemifield. The inferior hemifield showed more consistent waveforms throughout, with the amplitude only increasing by 11% with sectoral summation. Intra-subject variability (10.6%) is less for sectors than for individual points (17.3%). Inter-subject amplitude differences are high, calculated at 56% for individual points and 45% for sectors. CONCLUSIONS Due to differences in waveform as a result of underlying cortical anatomy, individual VEP responses from multifocal recordings should be grouped as sectors along the vertical meridian and above and below the horizontal, rather than by hemifields or quadrants. This finding is significant if one is considering within-field grouping strategies similar to the glaucoma hemifield test used in conventional perimetry, or reporting derived overall VEP amplitudes and latencies from a multifocal recording. Large amplitude variations between individuals and small signals from horizontal and upper field seen in single channel recording, still limit the application of this technique as a form of objective perimetry.
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Affiliation(s)
- A I Klistorner
- Save Sight and Eye Health Institute, Sydney University, Department of Ophthalmology, Australia.
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Abstract
More than 50% of ganglion cells may be damaged before visual field loss is measurable by conventional methods in primary open angle glaucoma. There is general agreement on the need to improve early diagnosis of visual field loss in primary open angle glaucoma. In this article, new techniques that enlist measurement of paracentral regions are discussed, and the ability of each method to detect visual field loss prior to perimetric loss is described.
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Affiliation(s)
- I Bodis-Wollner
- State University of New York, Health Science Center at Brooklyn, New York 11203, USA
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