Pattern electroretinograms in preperimetric and perimetric glaucoma

Journal Pre-proof Pattern electroretinograms in preperimetric and perimetric glaucoma Kyoung In Jung, Sooji Jeon, Da Young Shin, Jiyun Lee, Chan Kee Park PII:

S0002-9394(20)30061-1

DOI:

https://doi.org/10.1016/j.ajo.2020.02.008

Reference:

AJOPHT 11231

To appear in:

American Journal of Ophthalmology

Received Date: 22 July 2019 Revised Date:

4 February 2020

Accepted Date: 7 February 2020

Please cite this article as: Jung KI, Jeon S, Shin DY, Lee J, Park CK, Pattern electroretinograms in preperimetric and perimetric glaucoma, American Journal of Ophthalmology (2020), doi: https:// doi.org/10.1016/j.ajo.2020.02.008. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Elsevier Inc. All rights reserved.

Credit Author Statement

Conceptualization: K.I.J. Methodology: K.I.J., S.J. Validation: K.I.J. Formal analysis: K.I.J., S.J. Investigation: K.I.J., D.Y.S. Resources: K.I.J., C.K.P. Writing - Original Draft: K.I.J. Writing - Review & Editing: C.K.P. Visualization: K.I.J., J.L., D.Y.S. Project administration: K.I.J. Funding acquisition; K.I.J.

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Pattern electroretinograms in preperimetric and perimetric glaucoma

Abstract Purpose: To investigate whether visual function can be graded in detail using pattern electroretinogram (PERG) in preperimetric to perimetric glaucoma Design: Cross-sectional observational study Methods: Twenty-six normal subjects, 113 preperimetric glaucoma patients (which included glaucoma suspect patients), and 52 early perimetric glaucoma patients with a mean deviation (MD) > -10dB were included. Structural and functional measurements were performed using spectral-domain optical coherence tomography and a commercial ERG stimulator, respectively. Results: The average retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GCIPL) thickness were thinnest in perimetric group followed by the preperimetric group and the control group (P<0.001). PERG N95 amplitude was the largest in the control group followed by the preperimetric group, and the perimetric group (P<0.001). Among the preperimetric glaucoma patients, the presence of the RNFL defect was associated with lower PERG N95 amplitude (P=0.013). The N95 amplitude showed a significant relationship with average RNFL thickness (r=0.336, P<0.001) and GCIPL thickness (r=0.376, P<0.001). In the preperimetric group with the RNFL defect, the N95 amplitude showed larger areas under the receiver operating characteristics curve (0.779) than the MD (0.533, P=0.005). Conclusions: PERG N95 amplitudes decreased from the control to preperimetric glaucoma and were reduced more in perimetric glaucoma. The functional assessment for detecting early glaucomatous damage could be complemented by PERG N95 amplitude. Usefulness of PERG parameters except N95 amplitude seemed to be limited in a clinical setting because of relatively low diagnostic performance in preperimetric glaucoma.

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Pattern electroretinograms in preperimetric and perimetric glaucoma

Kyoung In Jung, Sooji Jeon, Da Young Shin, Jiyun Lee, Chan Kee Park

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Department of Ophthalmology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea * Address correspondence and reprint requests to: Chan Kee Park: Department of Ophthalmology, Seoul St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea 222 Banpo-daero, Seocho-ku, Seoul 137-701, Korea Tel.: 82-2-2258-6199, Fax: 82-2-599-7405 E-mail: [email protected]

Short title: Pattern ERG in preperimetric glaucoma

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Introduction Individuals with large optic disc cupping or retinal nerve fiber layer (RNFL) defects are regarded as “glaucoma suspect” or “preperimetric glaucoma” when standard automated perimetry does not become apparent. Sorting the preperimetric glaucoma patients who are at greater possibility for primary open-angle glaucoma is critical because they should be followed up regularly to determine the time if and when treatment is needed.1 A large cup-to-disc ratio (CDR) is one of predictors of the progression of glaucoma suspects to glaucoma.2-5. Focal RNFL defects are also fairly specific for optic nerve damage and are rarely found in healthy eyes.6, 7 Focal RNFL defects are considered as a feature of early glaucoma and indicate a relatively large loss of retinal ganglion cells (RGCs). 6-8 However, glaucomatous visual field (VF) defects do not appear on standard automated perimetry (SAP) 24-2 by the time 25-35% of the RGCs has been lost.9. The pattern electroretinogram (PERG) was known to mainly reflect the function of RGCs or with a contribution from other retinal cells. 10 The PERG showed promising outcomes in differentiating glaucoma patients from normal controls.10-14 It could be also used to detect glaucomatous insult early, considering that patients with ocular hypertension showed abnormal PERG findings.10, 15, 16 In glaucoma suspects, a longitudinal study found that the PERG changed 4 years before standard automated perimetry showed the defects.17 In glaucoma, damage to RGCs seems to occur mainly at the optic nerve head (ONH), especially the lamina cribrosa.18 The topographic changes of the ONH preceded peripapillary RNFL thinning in an ocular hypertension model of rhesus macaques. 19 In a human clinical study, ONH surface depression was detected prior to RNFL loss in glaucoma patients during follow-up for an average of 5.4 years.20 Given these findings, preperimetric glaucoma patients with the RNFL defect might have more attenuated visual function than those without the RNFL defect, although neither display VF abnormalities on SAP 24-2. In this study, we compared PERG findings in preperimetric glaucoma patients and early perimetric glaucoma patients. A comparison was made between preperimetric glaucoma patients with RNFL loss and those without the RNFL loss. The diagnostic performances of the PERG parameters were also evaluated in each subgroup.

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Methods Subjects This cross-sectional study was approved by the Institutional Review Board of the Catholic University of Korea, Seoul, Korea and was performed according to the tenets of the Declaration of Helsinki. Data was collected from glaucoma patients who satisfied the inclusion criteria at the Glaucoma Clinic of Seoul St. Mary’s Hospital between July 2018 and September 2018. The controls were recruited from the dry eye clinic of the same Hospital. Informed consent was obtained from all subjects. Patients were included if they have a best-corrected visual acuity ≥ 20/30, an open angle, and axial length less than 28 mm. Eyes with uveitis, retinal disease such as retinal vein obstruction, macular degeneration, diabetic retinopathy, or a history of retinal surgery, were excluded. When both eyes fulfilled the inclusion criteria, one eye per individual was randomly selected for this study. Classification of the Groups A glaucomatous VF damage was defined as a group of 3 or more spots; two of the points had a chance of presence < 5% in normal subjects, and one spot had a chance of presence < 1% in normal subjects for the pattern deviation plot. Patients with a glaucomatous optic disc, manifesting as diffuse or focal rim loss, notching, or an RNFL damage on fundus photography in accordance with glaucomatous VF damage with a mean deviation (MD) > -10dB, were assigned to the perimetric glaucoma group. Eyes with glaucomatous optic discs or the RNFL changes mentioned above without any abnormal VF damage, were assigned to the preperimetric glaucoma group (which included glaucoma suspect patients). The preperimetric glaucoma group was divided according to the presence of an RNFL defect on red-free fundus photography in subgroup analysis. The normal control group was defined as subjects having an IOP less than 21 mmHg, no history of increased IOP or neurologic diseases, no glaucomatous disc appearance, and no visible RNFL loss detected on red-free photography. Measurements All subjects performed a full ophthalmic examination, including Goldmann applanation tonometry, gonioscopic examination, red-free fundus photography. stereoscopic optic disc photography. Optical Coherence Tomography With Cirrus SD-OCT version 6.0 (Carl Zeiss Meditec, Inc.), the RNFL thickness was determined using the optic Disc Cube 200 x 200 scan mode and the ganglion cellinner plexiform layer (GCIPL) thicknesses was determined through GCA software using a macular cube scan. Detailed descriptions of GCIPL or RNFL thickness was previously described.21, 22 Only well-focused images with signal strengths >6 were included. Visual Field Testing

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All subjects performed SAP 24-2 with a Humphrey field analyzer (Carl Zeiss Meditec, Dublin, CA), using the Swedish interactive threshold algorithm (SITA) standard strategy. MD and pattern standard deviation (PSD) were analyzed. Reliable examinations were considered as those with less than 20% fixation losses, false positives, or false negatives.

Electroretinography A commercial ERG stimulator (Neuro- ERG, Neurosoft, Ivanovo, Russia) was used in this study. Two 35mm Ag/AgCl skin electrodes were attached to the lower eyelids, with two ground electrodes at both earlbes. Black and white checkerboards with a check size of 1.81° were displayed on a 24 inch-monitor with a 48° x 33° visual angle and at a distance of 60 cm. The pattern stimulus reversed in counterphase at 4 Hz. The mean luminance of the checkerboards was 105 cd/m². Subjects with undilated pupils fixated on a target at a red-colored fixed point of the monitor with a proper refractive correction. Signals were band-pass filtered (1-50 Hz), and sampled at 10,000 Hz. At least 100 measurements were averaged. To evaluate the reproducibility of the ERG variables, test-retest variability was measured with 80 randomly selected measurements. Statistical analysis SPSS software (ver. 17.0; SPSS Inc., Chicago, IL) was applied for statistical tests. Test-retest variability was estimated employing the intraclass correlation coefficient (ICC). ICC scores ≥0.75, 0.40-0.75, ≤0.40 are considered to be excellent, moderate, and poor, respectively. 23 Differences among the groups were assessed by independent t-test (for comparison between two groups), 1-way analysis of variance (ANOVA) (for comparison between three groups), or analysis of covariance (ANCOVA) adjusting for age. Correlations between RNFL or GCIPL thickness and PERG amplitudes were calculated with Pearson correlation coefficients. Correlations of <0.4 were classified as weak, correlations of ≥0.4 and <0.6 as moderate, and correlations of ≥0.6 as strong.24 The areas under the receiver operating characteristics curve (AUCs) were calculated to evaluate the diagnostic ability of each measurement. MedCalc (MedCalc Software Inc, Mariakerke, Belgium) was used to compare the AUC between the groups. P<0.05 was considered to designate statistical significance.

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Results Data from twenty-six normal subjects, 113 preperimetric glaucoma patients, and 52 early perimetric glaucoma patients, were analyzed. For the mean RNFL and GCIPL thickness, preperimetric glaucoma group showed lower value than the control group, and higher value than perimetric glaucoma group (all P<0.05, Table 1). The perimetric glaucoma group showed the lowest MD (-2.7±1.7 dB) and the greatest PSD value (4.1±1.9 dB). The PERG amplitude measurements showed excellent reproducibility for the P50 (ICC=0.817~0.885, Table 2) and N95 amplitude (ICC=0.953~0.978). The reproducibility for N 95 or P50 implicit time was moderate while N35 implicit time was moderate or poor. For PERG parameters, N95 amplitude was the largest in the control group followed by the preperimetric group, and the perimetric group (P<0.001; post hoc, control group> preperimetric group>perimetric group, Table 3). The P50 amplitude showed a significant difference only between the control and the perimetric glaucoma groups (P=0.001) Among the PERG implicit time parameters, N95 implicit time was significantly higher in the perimetric glaucoma group than the control group (P=0.005). Subgroup analysis in patients with preperimetric glaucoma according to the presence of an RNFL loss showed that PERG N95 amplitude was lower in the patients with RNFL loss (n=50) than in those without RNFL loss (n=63) (P=0.013, Table 4). The P50 amplitude was positively correlated with mean RNFL thickness (r=0.159, P=0.046; Figure 1) and GCIPL thickness (r=0.287, P<0.001). The N95 amplitude showed a significant relationship with RNFL thickness (r=0.336, P<0.001) and GCIPL thickness (r=0.376, P<0.001). For the implicit time, neither P50 nor N95 implicit time had a relevance to average RNFL or GCIPL thickness (all P>0.05). In the subgroup analysis of patients with preperimetric glaucoma, there were positive correlations between the PERG N95 amplitude and average RNFL or GCIPL thickness (RNFL thickness: r=0.417, P<0.001; GCIPL thickness: r=0.398, P<0.001). The P50 amplitude had a relevance to only mean RNFL thickness (r=0.212, P=0.029) in preperimetric glaucoma patients. Most of correlations between PERG amplitude parameters and average RNFL or GCIPL thickness were weak. Only the correlation between PERG N95 amplitude and average RNFL thickness was moderate in the subgroup analysis of patients with preperimetric glaucoma. The diagnostic abilities of PERG parameters and MD assessed by AUCs are shown in Table 5. In the preperimetric group with RNFL defects, the N 95 amplitude had the larger AUC (AUC, 0.779, 95% CI, 0.670-0.889) than the P 50 amplitude (AUC, 0.652, 95% CI, 0.515-0.790, P=0.042) or MD (AUC, 0.533, 95% CI, 0.397-0.668, P=0.005). In the perimetric glaucoma group and the preperimetric glaucoma group without RNFL defects, no difference was shown in the AUCs between the PERG parameters and MD (P>0.05).

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Representative cases for each group were displayed in figure 2. A normal control case showed the highest PERG N95 amplitude (8.51 µV). In patients with preperimetric glaucoma, PERG N95 amplitude was lower in the case with RNFL defect (4.43 µV) than without it (6.1 µV). The perimetric glaucoma case demonstrated the lowest PERG N95 amplitude (3.11 µV).

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Discussion We demonstrated that the preperimetric glaucoma group showed lower PERG N95 amplitude than the control group, and higher than the perimetric glaucoma group (P <0.05). Among the preperimetric glaucoma patients, patients with RNFL defects revealed a smaller PERG N95 amplitude than those without RNFL defect (P=0.013). The N95 amplitude had a positive correlation with mean RNFL thickness (r=0.336, P<0.001) and mean GCIPL thickness (r=0.376, P<0.001), although the correlations were weak. In the preperimetric glaucoma group with RNFL defects, the N95 amplitude had superior discrimination ability (0.779) for glaucoma than MD (0.533, P=0.005). In the preperimetric glaucoma group, the N95 PERG amplitude was smaller than that in the normal control group (P<0.001). This result is in line with structural parameters: the preperimetric group showed thinner average RNFL or average GCIPL thickness than the control group (Both P<0.001). Previously, Cvenkel et al.25 and Preiser et al.14 found that PERG amplitude was decreased in glaucoma suspect or preperimetric glaucoma patients compared with healthy eyes. However, a study by Kreuz et al. reported similar PERG amplitude between preperimetric glaucoma and control subjects, whereas the average P50 peak time transient PERG responses were decreased in preperimetric glaucoma patients.26 We found that N95 implicit time was increased only in the perimetric glaucoma group than the control group (P=0.004). Inconsistent results might have arisen from different settings as well as the type of PERG examination and visual angle. In subgroup analysis of patients with preperimetric glaucoma, PERG N95 amplitude was lower in those with RNFL loss than in those without RNFL loss. Eyes with localized RNFL defects are related to large RGC loss, 39% fewer than healthy eyes.6-8 Normal findings on SAP 24-2 in preperimetric glaucoma patients does not guarantee normal visual function because SAP 24-2 does not show glaucomatous VF defects by the time 25-35% of the RGCs have been lost. Given that PERG amplitude was decreased in preperimetric glaucoma with RNFL defects than those without the RNFL defect, visual function might be attenuated more in the preperimetric glaucoma group with RNFL loss than in those without RNFL loss. Our group previously reported that patients with preperimetric glaucoma showed abnormalities in 24-2 or 10-2 frequency doubling technology perimetry.27, 28 Further large-scale and longitudinal studies are needed to confirm these results. In a subset of patients with preperimetric glaucoma, there were positive correlations between the PERG N95 amplitude and average RNFL or GCIPL thickness (RNFL thickness: r=0.417, P<0.001; GCIPL thickness: r=0.398, P<0.001), even though the correlations were weak to moderate. Our results correspond to a study by Ventura et al. showing a significant positive relationship between PERG amplitude and mean RNFL thickness (r=0.309, P=0.004).29 For preperimetric glaucoma patients or glaucoma patients with hemifield loss, Kreuz et al. reported that PERG P50 or N95 amplitudes had no significant relationship with macular or circumpapillary RNFL thickness.26 Cvenkel et al. also failed to prove a relevance between the PERG amplitudes and RNFL thickness.25 The number of patients in each of their studies was small (Keruez et al.: n=24 eyes for preperimetric glaucoma,

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n=7 eyes for glaucoma hemifield loss; Cvenkel et al.: n=17 eyes for glaucoma suspect) compared with our study (n=113 eyes for preperimetric glaucoma group) or Ventura et al.’s study (n=84 for suspected glaucoma).25, 26 We used a different machine and settings (our study: Neuro- ERG, 48° x 33° visual angle, Kreuz et al.: RETiscan System, 23° x17 ° visual angel, Cvenkel et al.: Espion visual electrophysiology testing system, 21.6° x27.8 ° screen stimulator).25, 26 Several studies have suggested that PERG amplitude precedes RNFL loss as measured by SD-OCT by several years in suspected glaucoma patients.25, 30 These studies argue that RGC dysfunction measured by PERG has little correlation with SD-OCT measurements in suspected glaucoma patients,25, 30 because SD-OCT measures the structural loss of RGC axons or cell bodies rather than RGC dysfunction, which could be measured by ERG. However, the more RGC lost, the more dysfunctional or sick RGCs might occur in preperimetric glaucoma. PERG might be responsive to both RGC dysfunction and RGC loss. It is possible that the worse the glaucomatous damage, the fewer RGCs in play.29 Therefore, we assumed that there could be positive correlations between the PERG amplitudes and average RNFL or GCIPL thickness. The discriminating ability of PERG N95 amplitude in the preperimetric glaucoma with RNFL defect group (AUC, 0.779) was similar to that observed in a previous study (amplitude: 0.586, PERG ratio: 0.731).14 PERG N95 amplitude was more useful in distinguishing patients with preperimetric glaucoma from normal control subjects than MD on SAP (P=0.005). It is little wonder that MD has a low diagnostic ability in preperimetric glaucoma patients because these patients had no VF defect on 24-2 SAP. However, the diagnostic performance of PERG parameters except N95 amplitude was relatively low (mean AUC 0.504~0.652) in the preperimetric glaucoma group. In the absence of abnormal VF tests, clinicians may complement their assessment by adding the structural evaluation of RNFL with the state-of-the-art OCT. The OCT was reported to perform well in detecting preperimetric glaucomatous damage.31, 32 However, the OCT can evaluate only structural loss of RGCs and cannot assess dysfunction of RGCs. In preperimetric glaucoma patients, pattern ERG for evaluation of visual function may bridge a gap between the OCT and the 24-2 SAP. Electrophysiologic tests are not used routinely in clinical practice, although they are relatively objective and not dependent on the response of cortex in the brain. The difficulty of ERG measurements or invasiveness of corneal contact electrodes might refrain from using electrophysiologic examination. We employed skin electrodes, which are relatively noninvasive, and found them to be comparable to corneal contact electrodes.33, 34 Reproducibility for N95 or P50 amplitude was excellent but moderate or poor for implicit times. The significant results in this study are applicable mainly for PERG amplitudes. In conclusion, PERG N95 amplitudes were attenuated in preperimetric glaucoma group compared to controls and more so in the perimetric glaucoma group. In subgroup analysis of patients with preperimetric glaucoma, PERG N95 amplitude was lower in those with RNFL defects than those without the RNFL defect. PERG N95 amplitude could be useful as an ancillary tool to assess visual function,

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especially in preperimetric glaucoma patients with RNFL loss when 24-2 SAP shows no abnormality.

Acknowledgements

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A. Funding/support: This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (K.I.J., 2017R1D1A1B03035355). The funders had no role in study design, data collection and analysis, the decision to publish, or preparation of the manuscript. B. All authors declare that no competing interests exist with the funder.

References

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17. Bode SF, Jehle T, Bach M. Pattern electroretinogram in glaucoma suspects: new findings from a longitudinal study. Invest Ophthalmol Vis Sci 2011;52(7):4300-6. 18. Quigley HA, Addicks EM, Green WR, Maumenee AE. Optic nerve damage in human glaucoma. II. The site of injury and susceptibility to damage. Arch Ophthalmol 1981;99(4):635-49. 19. Fortune B, Burgoyne CF, Cull GA, Reynaud J, Wang L. Structural and functional abnormalities of retinal ganglion cells measured in vivo at the onset of optic nerve head surface change in experimental glaucoma. Invest Ophthalmol Vis Sci 2012;53(7):3939-50. 20. Xu G, Weinreb RN, Leung CK. Optic nerve head deformation in glaucoma: the temporal relationship between optic nerve head surface depression and retinal nerve fiber layer thinning. Ophthalmology 2014;121(12):2362-70. 21. Mwanza JC, Oakley JD, Budenz DL, Chang RT, Knight OJ, Feuer WJ. Macular ganglion cell-inner plexiform layer: automated detection and thickness reproducibility with spectral domain-optical coherence tomography in glaucoma. Invest Ophthalmol Vis Sci 2011;52(11):8323-9. 22. Shin HY, Park HY, Jung KI, Park CK. Comparative study of macular ganglion cell-inner plexiform layer and peripapillary retinal nerve fiber layer measurement: structure-function analysis. Invest Ophthalmol Vis Sci 2013;54(12):7344-53. 23. Fleiss JL. Reliability of Measurements. The design and Analysis of Clinical Experiments New York: Wiley, 1986:1-32. 24. Pinto LM, Costa EF, Melo LA, Jr., et al. Structure-function correlations in glaucoma using matrix and standard automated perimetry versus time-domain and spectral-domain OCT devices. Invest Ophthalmol Vis Sci 2014;55(5):3074-80. 25. Cvenkel B, Sustar M, Perovsek D. Ganglion cell loss in early glaucoma, as assessed by photopic negative response, pattern electroretinogram, and spectraldomain optical coherence tomography. Doc Ophthalmol 2017;135(1):17-28. 26. Kreuz AC, de Moraes CG, Hatanaka M, Oyamada MK, Monteiro MLR. Macular and Multifocal PERG and FD-OCT in Preperimetric and Hemifield Loss Glaucoma. J Glaucoma 2018;27(2):121-132. 27. Choi JA, Lee NY, Park CK. Interpretation of the Humphrey Matrix 24-2 test in the diagnosis of preperimetric glaucoma. Jpn J Ophthalmol 2009;53(1):24-30. 28. Jung KI, Park CK. Detection of Functional Change in Preperimetric and Perimetric Glaucoma Using 10-2 Matrix Perimetry. Am J Ophthalmol 2017;182:35-44. 29. Ventura LM, Sorokac N, De Los Santos R, Feuer WJ, Porciatti V. The relationship between retinal ganglion cell function and retinal nerve fiber thickness in early glaucoma. Invest Ophthalmol Vis Sci 2006;47(9):3904-11. 30. Banitt MR, Ventura LM, Feuer WJ, et al. Progressive loss of retinal ganglion cell function precedes structural loss by several years in glaucoma suspects. Invest Ophthalmol Vis Sci 2013;54(3):2346-52. 31. Lisboa R, Leite MT, Zangwill LM, Tafreshi A, Weinreb RN, Medeiros FA. Diagnosing preperimetric glaucoma with spectral domain optical coherence tomography. Ophthalmology 2012;119(11):2261-9. 32. Lisboa R, Paranhos A, Jr., Weinreb RN, Zangwill LM, Leite MT, Medeiros FA. Comparison of different spectral domain OCT scanning protocols for diagnosing preperimetric glaucoma. Invest Ophthalmol Vis Sci 2013;54(5):3417-25.

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33. Porciatti V, Ventura LM. Normative data for a user-friendly paradigm for pattern electroretinogram recording. Ophthalmology 2004;111(1):161-8. 34. Bach M, Ramharter-Sereinig A. Pattern electroretinogram to detect glaucoma: comparing the PERGLA and the PERG Ratio protocols. Doc Ophthalmol 2013;127(3):227-38.

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-Figure legends-

Figure 1. Scatter plots between the average retinal nerve fiber layer or ganglion cellinner plexiform layer thickness in total subjects excluding normal control subjects, and in patients with preperimetric glaucoma.

Figure 2. Representative cases. (A) A normal control case (a 39-year-old female): Preperimetric glaucoma cases without retinal nerve fiber layer (RNFL) defect (B, a 43-year-old male) and with RNFL defect (C, a 41-year-old male) (D) A perimetric glaucoma case (a 41-year-old male) Top row: optic disc photography, middle row: standard automated perimetry 24-2, bottom row: pattern electroretinogram Triangles indicated the RNFL defect.

Table 1. Demographics of subjects

Parameter

Age (years) Male/Female CCT (µm) Spherical equivalent (diopter) Axial length (mm) Average RNFL thickness Average GCIPL thickness SAP MD (dB) SAP PSD (dB)

Control group (n=26) 48.1±12.2 10/16 536.2±45.0 -2.2±2.7

Preperimetric glaucoma (n=113) 53.8±12.2 50/63 538.3±62.2 -1.7±3.0

Perimetric glaucoma (n=52) 51.1±11.1 18/34 535.1±38.9 -2.2±3.1

P value

24.6±1.1 92.6±7.9

24.4±1.7 84.7±10.7

24.4±4.7 77.3±9.9

0.977 < 0.001*

81.4±4.6

76.4±8.1

71.4±10.1

< 0.001*

-0.7±0.6

-0.6±1.2

-2.7±1.7

< 0.001*

1.5±0.2

1.5±0.3

4.1±1.9

< 0.001*

Post hoc

0.063 0.487 0.947 0.545

Control> preperimetric glaucoma>perimetric glaucoma Control> preperimetric glaucoma>perimetric glaucoma Control, preperimetric glaucoma>perimetric glaucoma Control, preperimetric glaucoma
CCT, Central corneal thickness; GCIPL, ganglion cell-inner plexiform layer; MD, mean deviation; PSD, pattern standard deviation; RNFL, retinal nerve fiber layer; SAP, standard automated perimetry *statistically significant difference between the groups, with P<0.05

Table 2.

Reliability of electroretinogram parameters

Pattern electroretinogram variables

Control group Preperimetric glaucoma Perimetric glaucoma (n=20) (n=30) (n=30) ICC 95% CI ICC 95% CI ICC 95% CI Amplitude (µV) P50 0.817 0.537~0.927 0.885 0.759~0.945 0.860 0.727~0.931 N95 0.953 0.882~0.982 0.966 0.929~0.987 0.978 0.953~0.989 Implicit time N35 0.408 -0.495~0.766 0.386 -0.291~0.708 0.367 0.013~0.639 (ms) P50 0.458 0.031~0.743 0.724 0.497~0.859 0.550 0.390~0.862 N95 0.576 -0.071~0.832 0.457 0.122~0.699 0.519 0.202~0.738 The reproducibility of electroretinogram parameters: excellent for P50 and N95 amplitudes, moderate for N95 and P50 implicit times, and moderate or poor for N35 implicit time

Table 3. Pattern electroretinogram amplitudes and implicit times in the control subjects, preperimetric, and perimetric glaucoma patients Control group

Preperimetric glaucoma

Perimetric glaucoma

P value*

P value**

P50

3.5±0.9

3.1±0.9

2.7±1.0

0.001

0.001

N95

6.7±1.6

5.6±1.4

4.8±1.2

<0.001

<0.001*

N35 P50

24.1±2.9 49.9±3.4

24.0±4.2 48.9±3.1

24.8±3.7 50.2±3.5

0.487 0.034

0.372 0.294

N95

98.3±5.6

98.4±6.3

102.1±8.6

0.005

0.006

Parameter

Amplitude (µV)

Implicit time (ms)

* P value for determined via analysis of variance (ANOVA) **P value for determined via analysis of covariance (ANCOVA) adjusting for age. Statistically significant values (P < 0.05) are shown in bold.

Post hoc Control>Perimetric glaucoma Control>preperimetric glaucoma>perimetric glaucoma

Perimetric glaucoma>control

Table 4. Pattern electroretinogram and spectral domain optical coherence tomography parameters in patients with preperimetric glaucoma according to the presence of retinal nerve fiber layer defects

Preperimetric glaucoma

Parameter

SD-OCT

Pattern ERG

Average RNFL thickness Average GCIPL thickness Amplitude (µV) Implicit time (ms)

P50 N95 N35 P50 N95

P value

RNFL defect (-) (n=63)

RNFL defect (+) (n=50)

89.0±8.0

79.6±11.2

<0.001*

78.9±6.3

74.1±9.0

0.007*

3.08±0.89 5.89±1.33 24.46±4.14 48.70±3.25 97.45±5.25

3.04±0.96 5.24±1.36 23.46±4.25 49.14±2.79 99.68±7.25

0.794 0.013* 0.212 0.441 0.061

ERG, electroretinogram; GCIPL, ganglion cell-inner plexiform layer; RNFL, retinal nerve fiber layer; SD-OCT, spectral domain optical coherence tomography *statistically significant difference between the groups, with P<0.05

Table 5. Areas under the receiver operating characteristic curve of pattern electroretinogram and visual field parameters

Amplitude (µV) Pattern ERG

P50 N95 N35

Implicit time (ms)

P50 N95

Visual field

MD

Preperimetric glaucoma without RNFL defect vs Control Sensitivity Mean at 95% CI Cutoff AUC specificity >80% 0.4800.622 0.38 2.77 0.765 0.4770.618 0.35 5.34 0.758 0.4120.547 0.41 26.65 0.681 0.4020.525 0.24 46.60 0.646 0.382 0.504 0.29 94.45 0.626 0.482 0.606 0.41 -0.06 0.721

Preperimetric glaucoma with RNFL defect vs Control Sensitivity Mean at 95% CI Cutoff AUC specificity >80% 0.5150.652 0.42 2.77 0.790 0.6700.779 0.54 5.22 0.889 0.4300.555 0.42 23.30 0.674 0.3830.506 0.2 46.60 0.629 0.423102.5 0.567 0.28 0.712 0 0.3970.533 0.25 -1.47 0.668

Perimetric glaucoma vs Control Mean AUC 0.766 0.847 0.516 0.583 0.640 0.845

95% CI 0.6500.882 0.7580.935 0.3790.654 0.4380.728 0.5090.771 0.7570.932

Sensitivity at specificity >80%

Cutoff

0.58

2.77

0.77

5.43

0.39

26.65

0.27

52.25

0.44

102.50

0.79

-1.29

AUC, the areas under the receiver operating characteristics curve; ERG, electroretinogram; RNFL, retinal nerve fiber layer Cut-off value at specificity > 80%

Pattern electroretinograms in preperimetric and perimetric glaucoma

Highlights No definite method to evaluate visual function in preperimetric glaucoma. The RNFL defect was associated with lower PERG amplitude in preperimetric glaucoma. Good discriminating ability of PERG N95 amplitude in preperimetric glaucoma with RNFL defect