Correlation between retinal nerve fibre layer thickness and retinal sensitivity

Evaluation of subjects with a moderate cup to disc ratio using optical coherence tomography and Heidelberg retina tomograph 3: impact of the disc area

Aim:

The aim was to evaluate subjects with a moderate cup to disc ratio using optical coherence tomograph (OCT) and Heidelberg retina tomograph (HRT) 3.

Settings and Design:

We included 80 patients with early glaucoma and 80 nonglaucomatous subjects with moderate cup/disc ratio (range of 0.5–0.8) to this cross-sectional study.

Subjects and Methods:

We compared results of color-coded algorithms of HRT 3 (Moorfields regression analysis [MRA] and Glaucoma probability score [GPS]) and OCT. All outputs are classified into three categories: Within normal limits (WNLs), borderline and outside normal limits (ONLs). Diagnostic accuracies of algorithms were determined using the highest sensitivity criteria.

Results:

The sensitivities of global MRA, GPS and OCT were 0.75, 0.925 and 0.725, respectively, in average disc area group and 0.85, 1.0 and 0.425, respectively, in large disc area group. The specificities of global MRA, GPS and OCT were 0.55, 0.15 and 0.85, respectively, in average disc area group and 0.425, 0.025 and 0.80, respectively, in large disc area group. Area under receiver operating characteristic curve (AUROC) of global MRA, GPS and OCT were 0.667, 0.617 and 0.792, respectively, in average disc area group and 0.746, 0.576 and 0.627, respectively, in large disc area group. AUROC of global MRA and OCT combination in the average and large disc area groups were 0.828 and 0.825, respectively.

Conclusions:

In contrast to GPS and OCT algorithms, diagnostic performance of MRA algorithm increased in large disc area group. Combining MRA and OCT algorithms produced satisfactory diagnostic performance in subjects with an average and large disc area.

The Multifocal On- and Off-Responses in the Human Diabetic Retina

The characteristics of the on- and off-responses in the human diabetic retina by a "long-duration" multifocal electroretinogram (mfERG) paradigm were investigated. Changes in the retinal antagonistic interaction were also evaluated in the early stage of diabetes mellitus (DM). Twenty type II diabetic patients with no or mild non-proliferative diabetic retinopathy (NPDR) and twenty-one age-matched healthy controls were recruited for "long-duration" mfERG measurements. A 61-hexagon mfERG stimulus was displayed under two chromatic conditions (white/black and blue/black) at matched luminance. The amplitudes and implicit times of the on-response components (N1, P1 and N2) and off-response (P2) components were analysed. The blue stimulation generally triggered greater mfERG amplitudes in P1, N2 and P2 (p<0.05) than those from white stimulation in both control and diabetic groups. The diabetic group showed significantly greater N2 amplitude than the controls under white stimulation in mid-retinal regions (Rings 2 and 4) (p<0.05). When the stimulus was changed from white to blue, the diabetic group showed a smaller percentage change in N2 amplitude than the controls in peripheral retinal region (Ring 5) (p<0.02). When a stimulus is changed from white (broad-band spectral stimulation) to blue (narrow-band spectral stimulation), a decrease in the involvement of lateral antagonism would be expected. The larger amplitude of the on-response component (N2) in the diabetic patients suggested an imbalance of lateral antagonism, and the lesser percentage change of N2 amplitude in the diabetic group may indicate an impairment of the cross-talk at the middle retinal level in early stages of DM.

Comparison of Macular Integrity Assessment (MAIA ™), MP-3, and the Humphrey Field Analyzer in the Evaluation of the Relationship between the Structure and Function of the Macula

Purpose

This study was conducted in order to compare relationships between the macular visual field (VF) mean sensitivity measured by MAIA^TM (Macular Integrity Assessment), MP-3, or Humphry field analyzer (HFA) and the ganglion cell and inner plexiform layer (GCA) thicknesses.

Methods

This cross-sectional study examined 73 glaucoma patients and 19 normal subjects. All subjects underwent measurements for GCA thickness by Cirrus HD-OCT and static threshold perimetry using MAIA^TM, MP-3, or HFA. VF and OCT in the retinal view were used to examine both the global relationship between the VF sensitivity and GCA thickness, and the superior hemiretina and inferior hemiretina. The relationship between the GCA thickness and macular sensitivity was examined by Spearman correlation analysis.

Results

For each instrument, statistically significant macular VF sensitivity (dB) and GCA thickness relationships were observed using the decibel scale (R = 0.547–0.687, all P < 0.001). The highest correlation for the global (R = 0.682) and the superior hemiretina (R = 0.594) GCA thickness-VF mean sensitivity was observed by the HFA. The highest correlation for the inferior hemiretina (R = 0.687) GCA thickness-VF mean sensitivity was observed by the MP-3. Among the three VF measurement instruments, however, no significant differences were found for the structure-function relationships.

Conclusions

All three VF measurement instruments found similar structure-function relationships in the central VF.

Correlation of structural retinal nerve fibre layer parameters and functional measures using Heidelberg Retinal Tomography and Spectralis spectral domain optical coherence tomography at different levels of glaucoma severity

BACKGROUND

To compare the structure/function relationship in glaucoma cases at different levels of severity, and with different disc sizes, between the Heidelberg Retinal Tomography and Spectralis spectral domain optical coherence tomography.

DESIGN

Retrospective study of glaucoma patients attending a Sydney-based private practice.

PARTICIPANTS

169 eyes of 169 patients with a clinical diagnosis of glaucoma.

METHODS

Patients were divided on visual field criteria into early (mean deviation > -4 dB), moderate (-4 dB < mean deviation < -10 dB) and severe (mean deviation < -10 dB) disease. Bivariate correlation (Spearman's rho) between mean threshold scores for each area and the corresponding mean retinal nerve fibre layer thickness sectoral measurement were calculated.

MAIN OUTCOME MEASURES

Correlation, as measured by Spearman's rho, between retinal nerve fibre layer measurements and mean threshold scores. Comparison of correlation strengths between the two scanning modalities with analysis of the effect of disease severity and disc size.

RESULTS

Both imaging techniques showed only moderate correlations at best. Spectral domain optical coherence tomography (global retinal nerve fibre layer Spearman's rho = 0.670, P < 0.01) had higher correlation coefficients compared with Heidelberg Retinal Tomography rim area (Spearman's rho = 0.449, P < 0.01) and retinal nerve fibre layer (Spearman's rho = 0.421, P < 0.01). Disc size did not have a significant influence on the structure/function relationship.

CONCLUSIONS

Spectral domain optical coherence tomography retinal nerve fibre layer measurements demonstrated closer correlations to visual field threshold reductions using a structure/function model in varying stages of glaucoma.

[Fundus perimetry in functional diagnostics of glaucoma. Applicable in the practice?]

Examination of the visual field using static automated perimetry (SAP) is the method of choice for the detection of functional damage secondary to glaucoma. However, with SAP early visual field defects might be missed even if there is already visible damage of the retinal nerve fibre. The microperimetry or beter fundus perimetry provides a detailed examination of the differential luminance threshold within defined retinal areas. However, in contrast to lesions of the retinal receptors, in cases of glaucomatous damage the retinal fibre course has to be considered resulting in a displacement between the structural lesion and the location of the related functional defect. The functional damage may be detected at earlier stages and with enhanced spatial resolution compared to conventional SAP. The extra costs and time associated with the application of fundus perimetry have prevented its widespread use. Current developments are leading to new options.

Structure-function relationships using the Cirrus spectral domain optical coherence tomograph and standard automated perimetry

PURPOSE

To evaluate the relationship between glaucomatous structural damage assessed by the Cirrus Spectral Domain OCT (SDOCT) and functional loss as measured by standard automated perimetry (SAP).

METHODS

Four hundred twenty-two eyes (78 healthy, 210 suspects, 134 glaucomatous) of 250 patients were recruited from the longitudinal Diagnostic Innovations in Glaucoma Study and from the African Descent and Glaucoma Evaluation Study. All eyes underwent testing with the Cirrus SDOCT and SAP within a 6-month period. The relationship between parapapillary retinal nerve fiber layer thickness (RNFL) sectors and corresponding topographic SAP locations was evaluated using locally weighted scatterplot smoothing and regression analysis. SAP sensitivity values were evaluated using both linear as well as logarithmic scales. We also tested the fit of a model (Hood) for structure-function relationship in glaucoma.

RESULTS

Structure was significantly related to function for all but the nasal thickness sector. The relationship was strongest for superotemporal RNFL thickness and inferonasal sensitivity (R(2)=0.314, P<0.001). The Hood model fitted the data relatively well with 88% of the eyes inside the 95% confidence interval predicted by the model.

CONCLUSIONS

RNFL thinning measured by the Cirrus SDOCT was associated with correspondent visual field loss in glaucoma.

Macular function in macular degenerations: repeatability of microperimetry as a potential outcome measure for ABCA4-associated retinopathy trials

PURPOSE

To measure macular visual function in patients with unstable fixation, to define the photoreceptor source of this function, and to estimate its test-retest repeatability as a prerequisite to clinical trials.

METHODS

Patients (n = 38) with ABCA4-associated retinal degeneration (RD) or with retinitis pigmentosa (RP) were studied with retina-tracking microperimetry along the foveo-papillary profile between the fovea and the optic nerve head, and point-by-point test-retest repeatability was estimated. A subset with foveal fixation was also studied with dark-adapted projection perimetry using monochromatic blue and red stimuli along the horizontal meridian.

RESULTS

Macular function in ABCA4-RD patients transitioned from lower sensitivity at the parafovea to higher sensitivity in the perifovea. RP patients had the inverse pattern. Red-on-red microperimetric sensitivities successfully avoided ceiling effects and were highly correlated with absolute sensitivities. Point-by-point test-retest limits (95% confidence intervals) were ±4.2 dB; repeatability was not related to mean sensitivity, eccentricity from the fovea, age, fixation location, or instability. Repeatability was also not related to the local slope of sensitivity and was unchanged in the parapapillary retina.

CONCLUSIONS

Microperimetry allows reliable testing of macular function in RD patients without foveal fixation in longitudinal studies evaluating natural disease progression or efficacy of therapeutic trials. A single estimate of test-retest repeatability can be used to determine significant changes in visual function at individual retinal loci within diseased regions that are homogeneous and those that are heterogeneous and also in transition zones at high risk for disease progression.

Integration and fusion of standard automated perimetry and optical coherence tomography data for improved automated glaucoma diagnostics

Background

The performance of glaucoma diagnostic systems could be conceivably improved by the integration of functional and structural test measurements that provide relevant and complementary information for reaching a diagnosis. The purpose of this study was to investigate the performance of data fusion methods and techniques for simple combination of Standard Automated Perimetry (SAP) and Optical Coherence Tomography (OCT) data for the diagnosis of glaucoma using Artificial Neural Networks (ANNs).

Methods

Humphrey 24-2 SITA standard SAP and StratusOCT tests were prospectively collected from a randomly selected population of 125 healthy persons and 135 patients with glaucomatous optic nerve heads and used as input for the ANNs. We tested commercially available standard parameters as well as novel ones (fused OCT and SAP data) that exploit the spatial relationship between visual field areas and sectors of the OCT peripapillary scan circle. We evaluated the performance of these SAP and OCT derived parameters both separately and in combination.

Results

The diagnostic accuracy from a combination of fused SAP and OCT data (95.39%) was higher than that of the best conventional parameters of either instrument, i.e. SAP Glaucoma Hemifield Test (p < 0.001) and OCT Retinal Nerve Fiber Layer Thickness ≥ 1 quadrant (p = 0.031). Fused OCT and combined fused OCT and SAP data provided similar Area under the Receiver Operating Characteristic Curve (AROC) values of 0.978 that were significantly larger (p = 0.047) compared to ANNs using SAP parameters alone (AROC = 0.945). On the other hand, ANNs based on the OCT parameters (AROC = 0.970) did not perform significantly worse than the ANNs based on the fused or combined forms of input data. The use of fused input increased the number of tests that were correctly classified by both SAP and OCT based ANNs.

Conclusions

Compared to the use of SAP parameters, input from the combination of fused OCT and SAP parameters, and from fused OCT data, significantly increased the performance of ANNs. Integrating parameters by including a priori relevant information through data fusion may improve ANN classification accuracy compared to currently available methods.

Predictors for visual field progression and the effects of treatment with dorzolamide 2% or brinzolamide 1% each added to timolol 0.5% in primary open-angle glaucoma

PURPOSE

This study aims to identify progression factors in patients with primary open-angle glaucoma (POAG), including the effects of treatment with dorzolamide 2% or brinzolamide 1%, each added to timolol 0.5%.

METHODS

A sample of 161 POAG patients were prospectively randomized to receive either dorzolamide 2% (DT) or brinzolamide 1% (BT) b.i.d., each added to timolol 0.5%, during a 60-month, evaluator-masked study. Progression was determined by perimetric criteria. Factors associated with visual field progression were estimated using a conditional Cox hazard model with patient intraclass correlation and were expressed as hazard ratios (HRs) with 95% confidence intervals (95% CIs).

RESULTS

Predictive baseline factors were lower diastolic blood pressure (DBP), lower mean arterial pressure (MAP), antihypertensive treatment, lower end-diastolic velocity (EDV) in the ophthalmic artery (OA) and short posterior ciliary artery (SPCA), and a higher resistivity index (RI) in the OA and SPCA. Progression risk decreased by approximately 30% and 20% with each centimetre per second increase of EDV in the OA and SPCA, respectively, from baseline to the last follow-up visit. Each RI decrease (or increase) of 0.01 unit in the OA or SPCA was associated with an approximate 20% decrease (or increase) in risk for progression. In a multivariate analysis, progression risk was significantly lower in eyes treated with DT (HR=0.65, 95% CI 0.41-0.90) compared with those treated with BT.

CONCLUSIONS

Progression increased with lower DBP, lower MAP, antihypertensive medication, lower EDV in the OA and SPCA, and higher RI in the OA and SPCA. The risk for progression in patients treated with DT was half that in patients treated with BT.

Linking structure and function in glaucoma

The glaucomas are a group of relatively common optic neuropathies, in which the pathological loss of retinal ganglion cells causes a progressive loss of sight and associated alterations in the retinal nerve fiber layer and optic nerve head. The diagnosis and management of glaucoma are often dependent on methods of clinical testing that either, 1) identify and quantify patterns of functional visual abnormality, or 2) quantify structural abnormality in the retinal nerve fiber layer, both of which are caused by loss of retinal ganglion cells. Although it is evident that the abnormalities in structure and function should be correlated, propositions to link losses in structure and function in glaucoma have been formulated only recently. The present report describes an attempt to build a model of these linking propositions using data from investigations of the relationships between losses of visual sensitivity and thinning of retinal nerve fiber layer over progressive stages of glaucoma severity. A foundation for the model was laid through the pointwise relationships between visual sensitivities (behavioral perimetry in monkeys with experimental glaucoma) and histological analyses of retinal ganglion cell densities in corresponding retinal locations. The subsequent blocks of the model were constructed from clinical studies of aging in normal human subjects and of clinical glaucoma in patients to provide a direct comparison of the results from standard clinical perimetry and optical coherence tomography. The final formulation is a nonlinear structure-function model that was evaluated by the accuracy and precision of translating visual sensitivities in a region of the visual field to produce a predicted thickness of the retinal nerve fiber layer in the peripapillary sector that corresponded to the region of reduced visual sensitivity. The model was tested on two independent patient populations, with results that confirmed the predictive relationship between the retinal nerve fiber layer thickness and visual sensitivities from clinical perimetry. Thus, the proposed model for linking structure and function in glaucoma has provided information that is important in understanding the results of standard clinical testing and the neuronal losses caused by glaucoma, which may have clinical application for inter-test comparisons of the stage of disease.