Relationship between Optical Coherence Tomography, Pattern Electroretinogram and Automated Perimetry in Eyes with Temporal Hemianopia from Chiasmal Compression

Abstract

purpose. To evaluate the relationship between pattern electroretinogram (PERG) amplitude, macular and retinal nerve fiber layer (RNFL) thickness by optical coherence tomography (OCT), and visual field (VF) loss on standard automated perimetry (SAP) in eyes with temporal hemianopia from chiasmal compression.

methods. Forty-one eyes from 41 patients with permanent temporal VF defects from chiasmal compression and 41 healthy subjects underwent transient full-field and hemifield (temporal or nasal) stimulation PERG, SAP and time domain-OCT macular and RNFL thickness measurements. Comparisons were made using Student’s t-test. Deviation from normal VF sensitivity for the central 18° of VF was expressed in 1/Lambert units. Correlations between measurements were verified by linear regression analysis.

results. PERG and OCT measurements were significantly lower in eyes with temporal hemianopia than in normal eyes. A significant correlation was found between VF sensitivity loss and full-field or nasal, but not temporal, hemifield PERG amplitude. Likewise a significant correlation was found between VF sensitivity loss and most OCT parameters. No significant correlation was observed between OCT and PERG parameters, except for nasal hemifield amplitude. A significant correlation was observed between several macular and RNFL thickness parameters.

conclusions. In patients with chiasmal compression, PERG amplitude and OCT thickness measurements were significant related to VF loss, but not to each other. OCT and PERG quantify neuronal loss differently, but both technologies are useful in understanding structure-function relationship in patients with chiasmal compression. (ClinicalTrials.gov number, NCT00553761.)

Introduction

The clinical assessment of anterior pathway diseases involves both visual field (VF) tests and structural evaluation of the neural structures of the fundus—traditionally, the optic nerve head appearance and retinal nerve fiber layer (RNFL) thickness and, more recently, macular thickness measurements. ^{1 2} Studies evaluating the relationship between functional and structural measurements of the neural structures of the eye are of great importance to the diagnosis and monitoring the course of diseases. ¹ For the structure–function relationship, the extent of VF loss, usually assessed by standard automated perimetry (SAP) is the parameter most commonly used to estimate the severity of visual loss. Structural measurements made with recently introduced technologies make it possible to objectively detect and quantify axonal loss. Optical coherence tomography (OCT) is one such device that acquires cross-sectional images of retinal structures from which estimates of the neural integrity of the fundus can be made. Neural integrity may also be objectively assessed by pattern electroretinography (PERG), which is believed to reflect the function of retinal ganglion cell (RGC) and neighboring inner retinal structures when a temporally modulated patterned stimulus of constant mean luminance is viewed. ^{3 4}  

Several studies involving patients with glaucoma support the hypothesis of a spatial correspondence between RGC loss assessed with OCT or electrophysiology and VF defect. ^{5 6 7 8 9} However, structure–function relationships in glaucoma cannot be extrapolated to nonglaucomatous optic neuropathies, especially when these are associated with reversible functional damage and are capable of producing a range of patterns of clinical defects such as central visual loss, color vision impairment, pallor of the neuroretinal rim and different spectra of VF defects. Studies on structure–function relationship in different optic pathway diseases are important in the assessment of the ability of new instruments to estimate neuronal loss. Previous studies have demonstrated that the pattern of neural loss in patients with long-standing chiasmal compression represents a rather unique model of retinal neural loss. ^{2 10 11 12} In these patients, the crossed nerve fibers originating in the nasal hemiretina are lost, with preservation of the uncrossed fibers, which originate in the temporal hemiretina and penetrate the optic nerve through the superior and inferior arcuate fiber bundles. Therefore, RNFL loss occurs predominantly on the nasal and temporal sides of the optic disc, a pattern that can be identified on ophthalmoscopy as band atrophy (BA) of the optic nerve. ¹³  

Although a good correlation has been documented between RNFL ¹ or macular thickness measurements ² and SAP perimetry in eyes with BA of the optic nerve, no study so far has been conducted to investigate the correlation between electrophysiological measurements and OCT findings with perimetry in such patients. Therefore, the purpose of this study was to evaluate the relationship between macular and RNFL thickness measured by OCT, RGC function assessed by PERG and VF sensitivity determined by SAP in patients with BA of optic nerve from chiasmal compression. 

Methods

Subjects

Forty-one eyes from 41 patients (25 male) with temporal hemianopia from chiasmal compression and 41 eyes from 41 normal (18 male) controls were recruited for examination at the Division of Ophthalmology of the University of São Paulo Medical School. All patients with a history of chiasmal lesions had already submitted to previous treatment of the suprasellar lesion and had had stable VF defects for at least 1 year before study entry. Thirty-six patients had pituitary adenoma, four had craniopharyngioma, and one had suprasellar meningioma. The study adhered to the tenets of the Declaration of Helsinki, and informed consent was obtained from all participants. Approval was obtained for the study from the Institutional Review Board Ethics Committee. 

Subjects underwent a complete ophthalmic examination including VF evaluation using standard automated perimetry (SAP). VF, OCT, and PERG examinations were performed within a maximum period of 2 weeks. Among the inclusion criteria for the study were best-corrected VA of 20/25 or better in the study eye, age between 20 and 75 years, spherical refraction within ± 5 D and cylinder refraction within ± 4 D, intraocular pressure below 22 mmHg, and reliable VF. Patients with clinical signs of glaucomatous optic neuropathy or optic disc anomaly or history of intraocular pressure elevation were excluded. 

The control group consisted of normal healthy volunteers recruited from among the hospital staff with normal ophthalmic examination and normal SAP VF, defined as a pattern SD (PSD) within the 95% confidence limits and a glaucoma hemifield test result within normal limits. Healthy control eyes also had healthy-looking optic discs and RNFL. One eye of each healthy subject was included for analysis. 

Visual Field Testing

VF testing was performed using SAP with the 24-2 SITA-Standard strategy (Humphrey Field Analyzer; Carl-Zeiss Meditec, Dublin, CA), with Goldmann size III target. Near refractive correction was used, calculated according to the subjects’ age by the perimeter software. Reliability criteria were false positives, false negatives, or fixation losses less than30%. 

Patients with BA were required to have complete or partial temporal hemianopia on SAP and a nasal hemifield within normal limits, defined as the absence of any cluster of at least three points with P < 5% on the pattern-deviation plot. Only one eye of each patient was selected for analysis. 

PERG Recording and Measurements

Transient checkerboard PERG was recorded in accordance with the guidelines of the International Society for Clinical Electrophysiology of Vision (ISCEV) ¹⁴ (RETiscan System; Roland Consult, Wiesbaden, Germany). The checkerboard stimulus was generated on a pattern-reversing checkerboard subtending a visual angle of 23° (horizontal) × 17° (vertical) on the retina at 1 m viewing distance. The black-and-white checks (measuring 0.8°) had a mean luminance of 80 cd/m² and a contrast of 97%. The pattern reversed at a rate of 8.6 reversals per second (4.3 Hz), with an analysis time of 180 ms. Online artifact rejection was set at 100 μV and the bandpass of the amplifier ranged between 5 and 50 Hz. 

Each patient’s refraction was optimally corrected, and stimulation was monocular after occlusion of the other eye. The subject was instructed to look at a 10-mm X fixation target at the center of the screen. Sweeps contaminated by eye blinks or gross eye movements were rejected automatically. Fixation on the central target was carefully monitored during the examination, and the patient was constantly reminded to maintain central fixation. DTL electrodes were used for all recordings, and gold cup electrodes and ground electrodes served as reference on the temples and forehead, respectively. The conjunctiva was anesthetized with tetracaine eye drops. No miotic or mydriatic drugs were used. 

Three checkerboard pattern presentations were used in this study: full-field, temporal hemifield, and nasal hemifield (Fig. 1) . The averaged response of 200 artifact-free reversals was recorded for each test with a minimum of two trials per presentation. Each wave acquisition required approximately 3 minutes. The results shown are the average of the two recordings. For all acquisitions, amplitudes at P50 and N95 were measured relative to baseline and stimulus onset. In addition, the overall amplitude, taken as the maximum peak-to-trough amplitude (P50+N95), was calculated for each acquisition. This parameter was used in our analyses based on findings from previous studies showing it to be highly capable of distinguishing BA eyes from normal eyes. ¹⁵  

OCT Scanning

Subjects underwent ocular imaging with dilated pupils using a commercially available OCT scanner (Stratus; Carl Zeiss Meditec, Dublin, CA). Good-quality scans had to have focused images and signal strength equal to or higher than 7 and a ring centered around the optic disc in the case of the RNFL scans. For macula scans, the radial scans had to be centered on the fovea. 

The fast macular thickness protocol was used to obtain macular thickness measurements with OCT generated from six 6-mm linear scans in a spokelike radial configuration with each line 30° apart. Macular thickness parameters were automatically calculated by the software (version 4.0.1). The three macular parameters used in this study (global average macular thickness, average temporal and average nasal thickness) were calculated from the available data. 

Global average macular thickness was calculated as the weighted average of the sectoral macular thickness measurements excluding the fovea. Average temporal and nasal thickness was calculated as the weighted average of values from the outer and inner segments of the temporal and the nasal hemiretinas, respectively. 

The fast RNFL algorithm (Stratus-OCT; Carl Zeiss Meditec) was used to obtain RNFL thickness measurements. Three images were acquired from each subject, with each image consisting of 256 A-scans along a 3.4-mm diameter ring around the optic disc. Peripapillary RNFL thickness parameters were automatically calculated by the software, including average thickness (360°); temporal, superior, nasal, and inferior quadrant thickness, and thickness in each one of the 12 clock-hour (30°) segments, with the 3-, 6-, 9-, and 12-o’clock position indicating the nasal, inferior, temporal, and superior region, respectively. Based on previously reported correlations between VF locations and regions of the optic disc, ^{6 16} RGC axons corresponding to the area tested in the PERG were expected to enter the optic disc in the temporal 150° segment comprising the five 30° segments between 7 and 11 o’clock. To match the area stimulated by PERG, we calculated the RNFL thickness of the temporal sector subtending 150° (75° above and 75° below the horizontal axis; Fig. 2 , left). We also analyzed RNFL thickness data from the 9-o’clock segment to check for correlation with PERG nasal hemifield–stimulated findings (Fig. 2 , middle) and RNFL thickness based on the average of the 7- and 11-o’clock segments to check for correlations with temporal hemifield–stimulated PERG findings (Fig. 2 , right). Data from global, temporal, and nasal average macular thicknesses were also analyzed (Fig. 2) . 

Data Analysis and Statistics

PERG and OCT parameters of eyes with BA and normal control eyes were first compared by using Student’s t-test. VF sensitivity for the 16 central points (18° × 18°), roughly the equivalent of the area tested by PERG and in the fast macular thickness scan protocol (Fig. 1) . The severity of VF defects in patients with BA was evaluated by calculating the central mean deviation (CMD) from normal for the 16 central test points on SAP. This calculation was performed by averaging the total deviations for the 16 central test points. We also determined the central nasal mean deviation (CNMD) and the central temporal mean deviation (CTMD) by averaging the values of the total deviation plot for the eight nasal and eight temporal points, respectively. For each calculation, the deviation from normal at each test location provided in decibel (dB) was converted to unlogged 1/Lambert (1/L) units by dividing the dB value by 10 and then unlogging the quotient. The average value for each calculation was performed by using the unlogged 1/L values. 

To determine the degree of association between measurements, we calculated Pearson’s correlation (r) between PERG amplitude parameters, VF sensitivity loss parameters and OCT RNFL and macular thickness parameters. Subsequently, the relationship between VF sensitivity loss expressed in 1/L and PERG or OCT parameters was described with linear regression analysis based on the linear model proposed by Hood et al. ^{9 17} A multivariate stepwise regression analysis was performed to evaluate the parameters most likely to predict the presence of a VF defect. In all regression analyses VF sensitivity loss was used as the dependent variable, whereas PERG amplitude and RNFL or macular thickness parameters were used as independent variables. P < 0.05 was considered statistically significant. 

Results

A total of 41 eyes with temporal hemianopia and 41 control eyes were studied. The mean age ± SD was 46.0 ± 12.8 years (range, 21–73) in patients with BA, and 41.1 ± 13.2 years (range, 25–78) in normal subjects (P = 0.09; Student’s t-test). On SAP 18 eyes had complete temporal hemianopia; 10 had incomplete defects greater than one VF quadrant, 5 a defect of approximately one quadrant, and 8 a defect involving less than one quadrant (mean ± SD). SAP mean deviation was −9.7 ± 4.7. The funduscopic examination revealed signs of BA in all 41 eyes with temporal hemianopic field defect. 

Table 1shows PERG amplitudes evoked by full-field, temporal, and nasal hemifield stimulation, OCT macular and RNFL thickness parameters, and the deviation from normal in the 16 central VF test points expressed in dB and 1/L for eyes with BA and controls. All parameters were significantly lower in BA eyes than in normals. 

Table 2shows the relationship between PERG parameters and VF sensitivity loss in the central 16 VF test points expressed in dB and 1/L units. A significant correlation was observed between CMD or CTMD and the full-field stimulation PERG amplitude as well as between the nasal hemifield stimulation PERG amplitude and all three VF sensitivity loss parameters. No significant correlation was observed between the temporal hemifield stimulation PERG amplitude and any of the VF sensitivity loss parameters. However, a significant correlation was found for temporal 150° RNFL thickness measurement and both CMD and CTMD, in decibels (0.48 and 0.47, respectively) as well as in 1/L units (R = 0.45 and 0.56, respectively). No significant correlation was observed for RNFL thickness between the temporal 150 segment and CNMD or between RNFL thickness in the 9-o’clock segment and any VF parameter. A significant correlation was observed between macular thickness parameters, on one side, and VF CMD and CTMD (but not CNMD), on the other (Table 2) . 

Figure 3shows the results of the linear regression analysis of the best performing PERG amplitude, OCT RNFL thickness and OCT macular thickness parameters and VF sensitivity loss parameters in 1/L units. A multivariate stepwise regression model identified the best variables for predicting CMD severity to be average RNFL thickness in the 7- and 11-o’clock segment and nasal stimulation PERG amplitude. For predicting CTMD severity the best variables were RNFL thickness in the temporal 150° segment and temporal macular average. Only the nasal stimulation PERG amplitude was predictive of CNMD. 

No significant correlation was observed between any PERG amplitude and OCT RNFL or macular thickness parameter (P < 0.05), save between nasal hemifield stimulation parameter and average RFNL thickness in the 7- and 11-o’clock segments (Table 3) . Significant correlations were observed between global macular average or temporal average macular thickness and RNFL thickness in the temporal 150-degree segment and between global average or nasal average macular thickness and average RNFL thickness in the 7- and 11-o’clock segments, but not between any of the macular thickness parameters and RNFL thickness in the 9-o’clock segment (Table 4) . 

Discussion

In the present study, all the parameters for the PERG amplitude and OCT RNFL and macular thicknesses were significantly smaller in eyes with BA of the optic nerve than in the control eyes. This was expected because our patients had long-standing and often severe temporal VF loss, and previous studies have documented RNFL loss ^{1 2 10 11 18 19} and reduced macular thickness ² in such patients. The significantly reduced PERG amplitude observed in eyes with temporal VF defect from chiasmal compression matches findings in previous studies ¹⁵ and in studies by other authors involving patients with anterior visual pathway diseases. ^{3 20 21} In the present study, however, our main purpose was to evaluate the relationship between OCT, PERG, and VF parameters. When assessing patients with anterior visual pathway diseases, it is important to know how different technologies quantify permanent damage so that we can estimate possible functional improvement after treatment and possible worsening with disease progression. Previous studies have evaluated the structure–function correlation between VF sensitivity and PERG or OCT parameters in patients with glaucoma. The PERG is believed to reflect the function of the inner retina ^{3 4 22} ; thus, PERG amplitude should be related to the number of functioning RGCs. In glaucomatous eyes, PERG amplitude has been reported to be reduced, ^{3 23 24 25} and significant correlations have been found between PERG amplitude and VF sensitivity. ^{4 26 27 28 29} The exact relationship between abnormalities in PERG parameters and VF. However. Is uncertain. Some authors have reported PERG parameters to be frequently abnormal in patients with glaucoma even in the absence of defects in the central VF, ^{6 28 29 30} thus precluding correlations between the two parameters. In contrast, Garway-Heath et al. ⁶ found evidence of a continuous, linear structure–function relationship between the number of ganglion cells and differential light sensitivity expressed in 1/L units. A study by Hood et al. ⁴ suggests that in glaucoma small field losses are associated with greater than expected amplitude losses, whereas large field losses are associated with smaller than expected amplitude losses. Although the relationship between PERG amplitude and VF loss is still debatable, several studies have documented a good structure–function correlation between OCT RNFL or macular thickness parameters and VF sensitivity in patients with glaucoma, ⁸ ischemic optic neuropathy ³¹ or optic chiasm compression. ^{1 2}  

To our knowledge, this is the first study to evaluate the relationship between PERG amplitude, OCT thickness measurements, and VF sensitivity loss in patients with chiasmal compression. When describing the pattern of neural loss in patients with temporal VF defect, two distinct regions in the fundus: one nasal to fovea (corresponding to the temporal VF), with moderate to severe neuronal loss, and one temporal to fovea (corresponding to the nasal VF). While neuronal structures originating nasal to the macula are certainly damaged, the structures temporal to the macula are relatively preserved. In fact, as indicated by previous studies, even when the nasal VF is within normal limits the neuronal structures temporal to the macula may be partially damaged, presumably due to tumor compression before optic pathway decompression was achieved. ^{2 15} The present study indicates that although full-field stimulation and nasal hemifield stimulation PERG amplitude correlated well with most of the observed VF sensitivity loss, there was no correlation between temporal hemifield stimulation and the VF sensitivity loss parameters investigated. At first, the absence of correlation between temporal stimulation PERG amplitude and VF sensitivity loss was surprising. However, since our patients had mostly severe temporal VF defects, the lack of correlation may be related to defect severity. Hood et al. ⁴ did not find a significant correlation between PERG parameters and VF loss in patients with glaucoma with severe VF defects. On the other hand, the presence of a significant correlation between full-field or nasal hemifield–stimulated PERG amplitude and VF sensitivity loss suggests that the relationship between PERG amplitude and VF sensitivity loss is more significant during the earlier stages of VF damage. Our findings therefore suggest that correlating PERG amplitude parameters with VF loss may be useful in milder cases of neuronal damage but of limited use in eyes with severe VF loss. A multivariate regression model identified the best variables for predicting CMD severity to be average RNFL thickness from the 7- and 11-o’clock segments and nasal stimulation PERG amplitude, all of which parameters relative to the retina temporal to the fovea. It should be remembered that neuronal loss was much less severe on this side of the retina than nasally to the fovea. 

The correlation between RNFL thickness and VF sensitivity has only been tested in detail in a previous study dealing with structure–function associations in patients with chiasmal syndrome. Danesh-Mayer et al. ¹ studied eyes with temporal VF defects from chiasmal compression and found that RNFL topography is related globally and sectorally to decreased SAP. The present study is in agreement with these findings in that RNFL thickness in the temporal 150° segment and the average RNFL thickness between the 7- and 11-o’clock segments correlated with the VF sensitivity loss. The absence of significant correlation between the 9-o’clock segment and VF sensitivity loss may be explained by the fact that most of our patients had severe temporal VF defect, and the 9 o’clock segment is usually the most severely affected in patients with temporal VF defects. In our study macular thickness measurements correlated significantly better with VF sensitivity loss than did RNFL thickness measurements, probably due to the disposition of the RNFL around the optic disc. Thus, according to a previously published description, ¹⁶ in optic nerve diseases the disposition of the fibers around the disc is adequate for structure–function correlation, but the situation is different in chiasmal or optic tract diseases which manifest as hemianopic field defect separating the neuronal damage along the vertical meridian. This pattern of neuronal loss correlates directly with nasal or temporal macular measurements. On the other hand, the fibers originating in the temporal hemiretina penetrate the optic disc superiorly and inferiorly, entering the disc in regions that also receive nerve fibers from the nasal hemiretina. Only the nasal segment of the optic disc receives fibers exclusively from the nasal hemiretina—all other areas receive fibers from both the nasal and the temporal hemiretina, resulting in lowered specificity compared with that of macular segments. 

Although both PERG amplitude parameters and OCT thickness parameters correlated generally well overall with VF sensitivity loss, no significant correlation was found between PERG amplitude and OCT thickness measurements except for a significant correlation between nasal hemifield stimulation PERG amplitude and average RNFL thickness in the 7- and 11-o’clock segments (Table 3) . When studying patients with glaucoma, Parisi et al. ⁷ found that OCT-measured average and temporal RNFL thickness values correlated significantly with PERG amplitude. A similar correlation has been observed in patients with multiple sclerosis. ³² Toffoli et al. ³³ used SLP to assess RNFL thickness in patients with glaucoma and found a statistically significant correlation between most RNFL thickness parameters and PERG amplitudes. However, no significant correlation was observed between temporal or nasal optic nerve segments and PERG amplitudes. On the other hand, Falsini et al. ³⁰ saw no correlation between PERG amplitude parameters and OCT RNFL thickness in patients with ocular hypertension but found a significant correlation in early glaucoma when RNFL loss was already present. Disagreements between our study and some of these papers may be related to differences in the severity of neural loss. Of interest, the only significant correlation observed was that between PERG values obtained stimulating the relatively normal nasal hemifield and RNFL thickness in the temporal hemiretina. The findings suggest that, in cases of early neuronal damage, the association of PERG amplitude parameters with OCT RNFL and macular thickness measurements may be used to improve structure–function relationships. 

In conclusion, our results indicate that in patients with chiasmal compression, PERG amplitude and OCT thickness measurements are significantly related to VF loss but not to each other. Our findings support the hypothesis that at earlier stages of VF loss the structure–function correlation is better between PERG amplitude and SAP, whereas with greater axonal loss the correlation between OCT RNFL or macular thickness parameters and SAP may still be present. Future studies are necessary to better understand how both electrophysiological and anatomic measurements may be combined to predict functional visual loss. 

 Supported by Grants 06/61549-6 and 07/54142-0 from Fundação de Amparo a Pesquisa do Estado de São Paulo FAPESP São Paulo, Brazil; and Grant 309709/2007-5 from Conselho Nacional de Desenvolvimento Científico e Tecnológico, CNPq, Brasília, Brazil.

 Submitted for publication November 1, 2008; revised January 24, 2009; accepted May 18, 2009.

 Disclosure: M.L.R. Monteiro, None; L.P. Cunha, None; L.V.F. Costa-Cunha, None; O.O. Maia, Jr, None; M.K. Oyamada, None

 The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertisement” in accordance with 18 U.S.C. §1734 solely to indicate this fact.

 

Figure 1.

 

Top row: PERG stimulation checkerboards (check size: 0.8) superimposed on fundus photographs: full-field (left), temporal hemifield (middle), and nasal hemifield (right) stimulation. Bottom row: demarcation of points read on 24-2 standard automated perimetry. The 16 points contained in the central square correspond to the area covered by full-field stimulation pattern electroretinography (left); the 8 points contained in the rectangle correspond to the area covered by nasal stimulation PERG (middle) and temporal stimulation PERG (right).

Figure 2.

 

Top row: sketch of the course of the retinal ganglion cell axons in the retina with test points for the 24-2 SAP field and superimposed PERG checkerboard showing full-field stimulation (left), temporal hemifield stimulation (middle), and nasal hemifield stimulation (right). Bottom row: schematic representation of the disc and macular areas (gray) evaluated with optical coherence tomography (illustrated immediately below the corresponding PERG stimulation area).

Table 1.

 

Study Parameter Measurements

Parameter	BA	Control	P *
PERG amplitude (μV)
Full-field stimulation	7.21 ± 2.64	11.29 ± 3.50	<0.001
Temporal hemifield stimulation	3.86 ± 1.39	6.55 ± 1.71	<0.001
Nasal hemifield stimulation	4.50 ± 1.20	6.52 ± 1.81	<0.001
OCT RNFL thickness (μm)
150° temporal segment	66.78 ± 16.07	99.98 ± 14.62	<0.001
30° 9-o’clock segment	30.76 ± 7.55	57.20 ± 7.20	<0.001
Average of 7- and 11-o’clock 30° segments	100.63 ± 26.82	141.35 ± 20.92	<0.001
OCT macular thickness (μm)
Average thickness	222.96 ± 12.09	248.87 ± 16.34	<0.001
Nasal average thickness	223.31 ± 15.27	263.63 ± 19.44	<0.001
Temporal average thickness	279.03 ± 16.35	295.8 ± 21.38	<0.001
Central visual field
CMD (dB)	−10.37 ± 6.04	−1.28 ± 1.05	<0.001
CMD (1/Lambert)	438.45 ± 169.68	820.07 ± 192.53	<0.001
CNMD (dB)	−1.50 ± 1.75	−0.96 ± 1.07	0.108
CNMD (1/Lambert)	788.30 ± 278.54	845.74 ± 199.83	0.305
CTMD (dB)	−19.24 ± 11.70	−1.29 ± 1.12	<0.001
CTMD (1/Lambert)	178.61 ± 231.50	794.36 ± 200.39	<0.001

  n = 41. Data are expressed as the mean ± SD.

*  Student’s t-test. Significant differences are in italic.

Table 2.

 

Relationship of Central Visual Field Sensitivity Loss, PERG Amplitude Parameters, and OCT Thickness Measurements in Eyes with BA of the Optic Nerve

	CMD			CTMD			CNMD
		dB	1/L	dB	1/L	dB	1/L
Full field PERG amplitude (μV)	0.36	0.38	0.33	0.34	0.29	0.26
Nasal hemifield PERG amplitude (μV)	0.44	0.45	0.40	0.36	0.35	0.34
Temporal hemifield PERG amplitude (μV)	0.26	0.24	0.23	0.19	0.22	0.18
150° temporal RNFL thickness (μm)	0.48	0.45	0.47	0.56	0.13	0.17
30° temporal (9-o’clock meridian) RNFL thickness (μm)	−0.01	−0.06	0.02	0.15	−0.21	−0.21
Average of 7- and 11-o’clock meridian RNFL thickness (μm)	0.47	0.47	0.45	0.51	0.21	0.25
Average macular thickness (μm)	0.51	0.33	0.52	0.56	0.05	−0.00
Nasal average macular thickness (μm)	0.48	0.20	0.49	0.49	−0.03	−0.13
Temporal average macular thickness (μm)	0.52	0.37	0.53	0.58	0.08	0.05

  n = 41. Data are Pearson’s correlation coefficients. Bold, P < 0.05; bold italic, P < 0.01.

Figure 3.

 

Scatterplots of pattern electroretinograms (top row), sectoral peripapillary RNFL (middle row), and macular thickness measurements (bottom row) plotted against VF differential light sensitivity (DLS) loss expressed in the antilog (1/L) scale. The two parameters with best correlation with each device were selected.

Table 3.

 

Relationship between PERG and OCT Parameters in 41 Eyes with BA of the Optic Nerve

OCT Parameter	Full-field Stimulation PERG Amplitude	Nasal Hemifield Stimulation PERG Amplitude	Temporal Hemifield Stimulation PERG Amplitude
RNFL thickness of 150° temporal segment	0.26	0.29	0.15
RNFL thickness of 30° temporal 9-o’clock segment	−0.10	−0.11	−0.00
Average RNFL thickness of 7- and 11-o’clock segments	0.31	0.33	0.19
Average macular thickness	0.14	0.18	0.10
Nasal average macular thickness	0.05	0.11	0.30
Temporal average macular thickness	0.23	0.22	0.22

 Pearson’s correlation coefficients. Bold, P < 0.05.

Table 4.

 

Relationship between OCT RNFL Thickness and Macular Thickness Parameters in 41 Eyes with BA of the Optic Nerve

RNFL Parameter	Average Macular Thickness	Nasal Average Macular Thickness	Temporal Average Macular Thickness
RNFL thickness of 150° temporal segment	0.51	0.30	0.58
RNFL thickness of 30° temporal 9-o’clock segment	0.25	0.26	0.15
Average RNFL thickness of 7- and 11-o’clock segments	0.38	0.44	0.19

 Pearson’s correlation coefficients. Bold, P < 0.05; bold italic, P < 0.01.

The authors thank Donald Hood for editorial review of the manuscript.