Polarimetric measurement of retinal nerve fiber layer thickness in glaucoma diagnosis

PURPOSE: To evaluate reliability and diagnostic value of polarimetric measurements of the retinal nerve fiber layer (RNFL) thickness in the diagnosis of glaucoma. METHODS: The study included 81 eyes with perimetric glaucoma with glaucomatous changes of the optic disc and visual field defects; 52 eyes with preperimetric glaucoma with glaucomatous optic disc abnormalities and normal achromatic visual fields; and 70 normal eyes. For determination of reliability, four examiners repeated polarimetric measurements five times in ten normal subjects. RESULTS: The polarimetric variables were significantly correlated with increasing mean visual field defect and decreasing neuroretinal rim area. In correlation analyses with visual field defects, correlation coefficients were highest for the variable "superior/nasal ratio" and "the Number," a variable calculated by the neural network of the device. In correlations with neuroretinal rim area, correlation coefficients were highest for measurements of the inferior nerve fiber layer thickness. The preperimetric glaucoma group and the control group differed significantly in the variables "superior/nasal ratio" and "the Number" and, to a smaller degree, in the variables "superior/temporal ratio" and "superior/inferior ratio." The Number variable had a sensitivity of 82% and 58% at a predefined specificity of 80% in separating perimetric glaucoma patients and preperimetric glaucoma patients, respectively, from control subjects. Reproducibility of the polarimetric measurements ranged between 70% and 89%. CONCLUSION: Polarimetric measurements of the RNFL thickness can detect glaucomatous optic nerve damage in patients with visual field loss, and in some patients with preperimetric glaucomatous optic nerve damage. Considering the fast performance, easy handling, and low maintenance costs, RNFL polarimetry may be helpful in glaucoma diagnosis.     

Quantitative analysis of visual field and optic disk in glaucoma: retinal nerve fiber bundle-associated analysis

 Background: A study was performed to evaluate whether visual field analysis using a perimetric nerve fiber bundle map gives information additional to global visual field indices and cumulative defect curves for early glaucoma diagnosis. Methods: One hundred and four control subjects, 124 patients with ocular hypertension (OHT), 97 patients with high-tension glaucoma without visual field defects (preHTG) and 91 patients with open-angle glaucoma with visual field defects [30 low-tension glaucoma (LTG), 61 high-tension glaucoma (HTG)] were included in this study. Correlation analyses were performed between (a) global visual field indices and total neuroretinal rim (NRR) area; (b) local mean values of four visual field areas and the NRR area of the corresponding four optic disk sectors; and (c) local mean values of 10 perimetric nerve fiber bundles (PNFB1–10) according to Weber and Ulrich (1991) and the four optic disk sectors. The correlations were adjusted for global mean defect and total NRR. Results: There were no significant correlations between NRR area and visual field in control subjects or in patients with OHT or preHTG for all three analyses. Significant correlations were found between the global visual field indices and the total NRR area for LTG and HTG. Significant correlations between local mean defects and NRR area of corresponding optic disk sectors were found only in LTG for the superior and inferior visual field area and the PNFB covering these areas. Conclusion: The method used for visual field analysis and sectorization of the optic disk does not give additional information on visual field defects in patients with normal global visual field indices and a normal cumulative defect curve. The nerve fiber bundle-related visual field analysis allows the topographical determination and quantification of glaucomatous damage. Received: 4 February 1999 Revised: 20 September 1999 Accepted: 4 October 1999     

Correlation of the optic disc size to glaucoma susceptibility

Previous studies have suggested that a larger optic disc size in blacks as compared with whites is related to the increased glaucoma susceptibility in blacks. In an intraindividual bilateral comparison of 245 white patients with open-angle glaucoma, the authors evaluated whether the glaucomatous optic nerve damage was greater or less in the eye with the larger optic nerve head. Highly myopic eyes were excluded. The difference in optic disc area of one eye as compared with the contralateral eye was not significantly correlated to the differences in visibility of retinal nerve fiber bundles and mean visual field defect between the two eyes. Mean perimetric loss and the retinal nerve fiber layer index were not significantly higher in the eye with the larger or smaller optic nerve head. This indicates that in whites, high myopes excluded, the susceptibility to glaucomatous optic nerve fiber loss may be independent of the optic disc size.     

Combined use of frequency doubling perimetry and polarimetric measurements of retinal nerve fiber layer in glaucoma detection

PURPOSE: The aim of this study was to evaluate the diagnostic usefulness of the combined use of frequency-doubling technology (FDT) perimetry and polarimetry of the retinal nerve fiber layer. DESIGN: Cross-sectional study. METHODS: Seventy ocular hypertensive patients (normal optic disk and standard perimetry, elevated intraocular pressure [>21 mm Hg]), 59 patients with "preperimetric" open-angle glaucoma (glaucomatous optic disk atrophy, elevated intraocular pressure [>21 mm Hg], no visual field defect in standard perimetry), 105 patients with "perimetric" open-angle glaucoma (glaucomatous optic disk atrophy and clearly marked visual field defect), and 73 control subjects had FDT screening (protocol: C-20-5) and polarimetric measurements (GDx). Criteria for exclusion: optic disks larger than 4 mm(2), media opacities, patients younger than 33 years or older than 66 years. None of the subjects had earlier FDT perimetry. One eye of each patient and control subject entered the statistical evaluation. Database and statistical software were used for case-wise recalculation of all missed localized probability levels to create a FDT screening score. RESULTS: At a predefined specificity of 94.5% in control eyes, discrimination between "perimetric" glaucoma and normal subjects is superior using the FDT perimetry (sensitivity = 84.8%) in comparison to polarimetry (sensitivity = 63.8%), whereas sensitivity is similar with both methods in "preperimetric" patients (GDx, FDT: 25.4%). In several cases, patients classified as glaucomatous by the GDx are not the same patients as identified by the FDT perimetry. Therefore, a two-dimensional discrimination analysis can increase correct positive classification. Using a linear combination of the present FDT screening score and polarimetry ("the number"), 92.4% of "perimetric" glaucoma eyes and 44.1% of "preperimetric" glaucoma eyes have been classified as glaucomatous. CONCLUSION: Joint usage of polarimetry and FDT perimetry indicate that a combination of different techniques which can uncover different glaucoma properties, might be helpful in early glaucoma detection.     

Retinal nerve fiber layer thickness measured with optical coherence tomography is related to visual function in glaucomatous eyes

PURPOSE: To determine the relationship between areas of glaucomatous retinal nerve fiber layer thinning identified by optical coherence tomography and areas of decreased visual field sensitivity identified by standard automated perimetry in glaucomatous eyes. DESIGN: Retrospective observational case series. PARTICIPANTS: Forty-three patients with glaucomatous optic neuropathy identified by optic disc stereo photographs and standard automated perimetry mean deviations >-8 dB were included. METHODS: Participants were imaged with optical coherence tomography within 6 months of reliable standard automated perimetry testing. MAIN OUTCOME MEASURES: The location and number of optical coherence tomography clock hour retinal nerve fiber layer thickness measures outside normal limits were compared with the location and number of standard automated perimetry visual field zones outside normal limits. Further, the relationship between the deviation from normal optical coherence tomography-measured retinal nerve fiber layer thickness at each clock hour and the average pattern deviation in each visual field zone was examined by using linear regression (R(2)). RESULTS: The retinal nerve fiber layer areas most frequently outside normal limits were the inferior and inferior temporal regions. The least sensitive visual field zones were in the superior hemifield. Linear regression results (R(2)) showed that deviation from the normal retinal nerve fiber layer thickness at optical coherence tomography clock hour positions 6 o'clock, 7 o'clock, and 8 o'clock (inferior and inferior temporal) was best correlated with standard automated perimetry pattern deviation in visual field zones corresponding to the superior arcuate and nasal step regions (R(2) range, 0.34-0.57). These associations were much stronger than those between clock hour position 6 o'clock and the visual field zone corresponding to the inferior nasal step region (R(2) = 0.01). CONCLUSIONS: Localized retinal nerve fiber layer thinning, measured by optical coherence tomography, is topographically related to decreased localized standard automated perimetry sensitivity in glaucoma patients.     

Measurement of the retinal nerve fiber layer thickness in clinical routine

The possibilities and limitations of methods for indirect and direct nerve fiber layer thickness (NFLT) measurements, and a summary of our own clinical studies using Optic Nerve Head Analyzer (Rodenstock, Munich, Germany) (ONHA), Laser Tomographic Scanner (Heidelberg Engineering, Heidelberg, Germany) (LTS), Heidelberg Retinal Tomograph (Heidelberg Engineering, Heidelberg, Germany) (HRT), Nerve Fiber Analyzer (Laser Diagnostic Technologies, San Diego, CA) (NFA) and Optical Coherence Tomography (OCT), together with the literature of the review period, are highlighted. A retinal hemifield test with the new parameters, retinal asymmetry difference and retinal asymmetry index, is introduced. These relative nerve fiber layer thickness (NFLT) measurement values are found to be independent of age, reference plane, and disc size. This reduces the interindividual variation of the measurements and may improve screening possibilities for glaucoma. The detection probability for nerve fiber bundle defects was found to be stage-dependent using HRT and NFA. For laser polarimetry, a decreasing correlation between NFLT and visual field loss with advanced glaucomatous disease was found. In the lower retina, a 6.9% higher NFLT was evident compared with the upper peripapillary NFLT in healthy eyes using NFA and OCT. This is not in correlation with perimetric retinal sensitivity, which was found to be 3.9% higher in the lower hemifield compared with the upper hemifield. In general, quantitative NFLT measures (HRT, NFA, OCT) were correlated with visual field loss in glaucoma. The interindividual variability of NFLT measurements, among other things, induces limitations on distinguishing beginning glaucoma from normals. Clinical and scientific significance and future directions of NFLT measurements are discussed.     

Retinal nerve fiber loss pattern in high-tension glaucoma by optical coherence tomography

PURPOSE: To identify the pattern of retinal nerve fiber layer thinning in high-tension primary chronic open-angle glaucoma (HT-PCOAG) using optical coherence tomography. METHODS: Retinal nerve fiber layer thickness was assessed with optical coherence tomography in 68 healthy controls and 68 age- and refractive error-matched patients with HT-PCOAG were recruited. Patients were divided into 3 subgroups according to their visual field mean deviation: early (> -3 dB), moderate (-3 to -7 dB), and moderately advanced (-7 to -15 dB). RESULTS: Retinal nerve fiber layer thickness values in inferotemporal and superotemporal regions were significantly lower in all groups of glaucomatous eyes than in healthy eyes (P<0.001). Inferotemporal thickness values were significantly lower than the superotemporal thickness values (P<0.001) in the early glaucomatous stage, but not significantly so in moderate and moderately advanced stages. CONCLUSIONS: Besides a diffuse retinal nerve fiber layer defect, a localized defect may present in the inferotemporal region in early-stage HT-PCOAG. These results also suggest that optical coherence tomography shows promise in providing quantitative data about the location and extent of retinal nerve fiber layer injury in glaucoma, and the findings are consistent with previous knowledge.     

Study of retinal nerve fiber layer thickness within normal hemivisual field in primary open-angle glaucoma and normal-tension glaucoma

PURPOSE: To determine if nerve fiber layer thickness (NFLT) in glaucoma patients decreases before the development of visual field loss, and if there is a difference in the thinning of NFLT between primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG) eyes. METHODS: Thirty patients (33 eyes) with POAG and 31 patients (31eyes) with NTG, who had visual field defects localized in either the upper or the lower hemifield verified by Humphrey Field Analyzer (HFA), were measured for NFLT by scanning laser polarimetry (Nerve Fiber Analyzer). Twenty-three normal subjects (23 eyes) matched in refraction and age with the glaucoma patients were recruited as the control group. The total deviation (TD) in each hemifield obtained by HFA and the 180 degrees NFLT of each corresponding hemifield was calculated. Relationships between the TD of the normal or abnormal visual hemifield and the NFLT of the corresponding hemifield were compared among the POAG, NTG, and control groups. RESULTS: The NFLT of the corresponding normal hemifield was decreased both in the POAG group and in the NTG group when compared with the corresponding measurements in control subjects. In POAG eyes, thinning of the NFLT in the corresponding normal hemifield was more remarkable if the TD of the abnormal hemifield was greater, but this tendency was not observed in NTG eyes. CONCLUSION: NFLT is already decreased when the visual field is still normal both in POAG eyes and in NTG eyes. However, the pattern of retinal nerve fiber layer damage in POAG may differ from that in NTG.     

Quantitative evaluation of the optic nerve head in patients with unilateral visual field loss from primary open-angle glaucoma

Measurable structural alterations of the optic nerve head may precede visual field abnormalities in early open-angle glaucoma. The authors studied the optic nerve heads of 10 patients with unilateral visual field loss from primary open-angle glaucoma, and 12 age- and sex-matched normal subjects. Topographic optic nerve head parameters were measured with a system of computerized image analysis (Rodenstock Analyzer, G. Rodenstock Instrumente GMBH, Munich, W. Germany). In patients with asymmetric primary open-angle glaucoma, eyes with normal visual fields had a slightly larger mean (+/- standard error of the mean) disc rim area (0.90 +/- 0.04 mm2) than eyes with glaucomatous visual field defects (0.78 +/- 0.05 mm2). However, both sets of eyes in the asymmetric primary open-angle glaucoma patients had smaller mean disc rim areas (P less than 0.0007) than did the control group (1.27 +/- 0.09 mm2). These findings support the hypothesis that loss of the optic disc rim can be detected before perimetric abnormalities develop in primary open-angle glaucoma.     

The retinal nerve fiber layer in normal and glaucomatous eyes. II. Correlations

The retinal nerve fiber layer is different in normal and glaucomatous eyes. We correlated semi-quantitative data of the retinal nerve fiber layer of 398 eyes with chronic primary open-angle glaucoma and of 234 normal eyes with the intra- and parapapillary morphometric signs and with the perimetric indices. The three parameters "sequence of the fundus sectors concerning the best visibility of the retinal nerve fiber bundles", "visibility of the nerve fiber bundles", and "localized defects" were significantly (p less than 0.001) correlated to 1) area of the neuroretinal rim as a whole and in four different optic disc sectors, 2) neuroretinal rim width determined every 30 degrees, 3) optic cup area, diameters and form, 4) horizontal and vertical cup/disc ratios and the quotient of the horizontal to vertical cup/disc ratio, 5) area and width of zone "Alpha", zone "Beta", and the total parapapillary chorio-retinal atrophy, 6) diameter of the retinal vessels, 7) grade of a "tesselated fundus", and 8) the visual field loss. If only the inferior temporal and the superior temporal sectors were considered, the retinal nerve fiber bundles were less visible in that sector with the largest notch in the neuroretinal rim, the smaller neuroretinal rim area and width, the thinner retinal vessels, and the larger zone "Alpha", zone "Beta", and total parapapillary chorio-retinal atrophy. The glaucomatous changes in the retinal nerve fiber layer are correlated in time and location with the intra- and parapapillary and the perimetric alterations. Evaluation of the retinal nerve fiber layer is a useful method to detect a glaucomatous optic nerve damage.(ABSTRACT TRUNCATED AT 250 WORDS)     

Correlation of automated visual field parameters and peripapillary nerve fiber layer thickness as measured by scanning laser polarimetry

PURPOSE: To correlate Humphrey visual field mean sensitivity and peripapillary nerve fiber layer thickness as measured by scanning laser polarimetry. METHODS: The authors studied 54 eyes of 34 patients who visited a university-based glaucoma clinic and had undergone scanning laser polarimetry and Humphrey perimetry within 6 months. The study population included normal patients and those with glaucoma, ocular hypertension, and glaucoma suspect. The authors correlated visual field sensitivity with peripapillary nerve fiber thickness, and visual field mean deviation with the average deviation from the normal nerve fiber layer thickness. They also correlated the visual field mean deviation with all available GDx Nerve Fiber Analyzer parameters. RESULTS: The visual field mean sensitivity and deviation showed a bilinear correlation to peripapillary nerve fiber layer thickness. The visual field mean sensitivity changed little when the nerve fiber layer thickness was greater than 70 microm. The nerve fiber layer thickness below this level was associated with a rapid decrease in the visual field sensitivity. Similarly, the visual field mean deviation was close to 0 dB when the nerve fiber layer was within -10 microm of the normal value; below this thickness, the mean deviation became substantially more negative. There was a large individual variability around the bilinear fit. Of the scanning laser polarimetry parameters, a calculated index, referred to as the number, had the highest correlation with the Humphrey mean deviation. CONCLUSION: The bilinear correlation and its variability between the scanning laser polarimetry and visual field parameters make it difficult to predict the result of one from the other. In general, the correlation between the two is better when there is a significant visual field defect than when the visual field is close to normal.     

Correlation between polarimetric retinal nerve fiber layer thickness and retinal sensitivity determined with frequency-doubling technology.

BACKGROUND AND OBJECTIVE: Correlation between polarimetric retinal nerve fiber layer thickness measured with variable corneal compensation and retinal sensitivity measured with frequency-doubling technology (FDT) and standard automated perimetry (SAP) was investigated. PATIENTS AND METHODS: Twenty-four consecutive patients with chronic open-angle glaucoma and 17 healthy control subjects (1 randomly selected eye for each subject) were evaluated. RESULTS: For all subjects, quadrant scanning laser polarimetry parameters correlated positively with both FDT and SAP mean sensitivity of the opposite hemifield (P< .001). Global scanning laser polarimetry parameters correlated positively with FDT-mean sensitivity, SAP-mean sensitivity, and FDT-mean deviation, and negatively with SAP-mean deviation (in SAP, mean deviation is positive in case of sensitivity loss) (P < or = .02). The nerve fiber indicator also correlated with FDT-pattern standard deviation and SAP-corrected loss variance (P < or = .01). Using un-logged sensitivity values, no further correlations were found. CONCLUSION: Our results show that a similar structure-function relationship exists between polarimetric retinal nerve fiber layer thickness determined with variable corneal compensation and retinal sensitivity measured with SAP and FDT.     

A comparison of optical coherence tomography and retinal nerve fiber layer photography for detection of nerve fiber layer damage in glaucoma

PURPOSE: To compare optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) thickness measurements with established methods for assessment of glaucomatous damage using RNFL photography and visual field testing. DESIGN: Cross-sectional study. PARTICIPANTS: Fifty-eight eyes of 58 healthy volunteer ocular hypertensive patients, glaucoma suspect patients, and glaucoma patients were included. METHODS: Optical coherence tomography 3.4-mm diameter circular scans were obtained within 3 months of RNFL photography and standard achromatic visual field testing. Three independent observers graded RNFL photographs using two standardized protocols. For each method, superior and inferior arcuate bundles were scored separately, and interobserver and intraobserver variation was measured. Standard achromatic visual field mean deviation in the superior and inferior hemifields was compared with RNFL damage as assessed by photography and OCT RNFL thickness measurements. MAIN OUTCOME MEASURES: Visual field mean deviation and severity of glaucomatous RNFL damage as assessed by photography. RESULTS: Optical coherence tomography RNFL thickness decreased with increasing RNFL damage as assessed by photography using both methods of photographic assessment. Standard achromatic perimetry mean deviation was significantly associated with OCT RNFL thickness (R(2) = 35%-43%) and RNFL photography severity score (R(2) = 18%-29%). CONCLUSIONS: These results suggest that the OCT shows promise for providing quantitative measures of RNFL thickness for diagnosing and monitoring glaucoma.     

Optic disk and nerve fiber layer imaging to detect glaucoma

PURPOSE: To compare optic disk and retinal nerve fiber layer (RNFL) imaging methods to discriminate eyes with early glaucoma from normal eyes. DESIGN: Retrospective, cross-sectional study. METHODS: In a tertiary care academic glaucoma center, 92 eyes of 92 subjects (46 with early perimetric open-angle glaucoma and 46 controls) were studied. Diagnostic performance of optical coherence tomography (StratusOCT; Carl Zeiss Meditec, Dublin, California, USA), scanning laser polarimetry (GDx VCC; Laser Diagnostic Technologies, San Diego, California, USA), confocal laser ophthalmoscopy (Heidelberg Retinal Tomograph [HRT] III; Heidelberg Engineering GmbH, Heidelberg, Germany), and qualitative assessment of stereoscopic optic disk photographs were compared. Outcome measures were areas under receiver operator characteristic curves (AUCs) and sensitivities at fixed specificities. Classification and regression tree (CART) analysis was used to evaluate combinations of quantitative parameters. RESULTS: The average (+/- standard deviation) visual field mean deviation for glaucomatous eyes was -4.0 +/- 2.5 dB (decibels). Parameters with largest AUCs (+/- standard error) were: average RNFL thickness for StratusOCT (0.96 +/- 0.02), nerve fiber indicator for GDx VCC (0.92 +/- 0.03), Frederick S. Mikelberg (FSM) discriminant function for HRT III (0.91 +/- 0.03), and 0.97 +/- 0.02 for disk photograph evaluation. At 95% specificity, sensitivity of disk photograph evaluation (90%) was greater than GDx VCC (P = .05) and HRT III (P = .002) results, but not significantly different than those of StratusOCT (P > .05). The combination of StratusOCT average RNFL thickness and HRT III cup-to-disk area with CART produced a sensitivity of 91% and specificity of 96%. CONCLUSIONS: StratusOCT, GDx VCC, and HRT III performed as well as, but not better than, qualitative evaluation of optic disk stereophotographs for detection of early perimetric glaucoma. The combination of StratusOCT average RNFL thickness and HRT III cup-to-disk area ratio provided a high diagnostic precision.     

A perimetric nerve fiber bundle map

The so-called nerve fiber bundle defects in the visual field are considered as being the fuctional equivalent of retinal nerve fiber bundle damage. This study examines the course and the position of scotoma borders in 159 visual fields with complete nerve fiber bundle defects using high resolution test point patterns. The scotoma border lines were averaged geometrically. The result is presented in the form of mean vectors.This functional map of nerve fiber lines shows a close correspondence to the anatomical course of the retinal nerve fibers. To make the result suitable for topographical analysis of visual fields, 21 areas (Perimetric Nerve Fiber Bundles) are defined. Certain arbitrary assumptions were neccessary because data were to scanty in some nasal regions. Also, the lines had to be fitted into a rectangular grid to be transferable to standard perimetric patterns.Topographical analysis on the basis of these areas may be useful for the evaluation of visual fields, particularly those of glaucoma.     

Wedge-shaped retinal nerve fiber layer defects in experimental glaucoma preliminary report

Many investigators have reported that abnormalities in the retinal nerve fiber layer may be the earliest sign of primary open-angle glaucoma. We attempted to create defects in the retinal nerve fiber layer in experimentally induced glaucoma and to examine their histology. By repeated circumferential argon laser photocoagulation of the trabecular meshwork of normal cynomolgus monkeys, we succeeded in causing a continuous increase in intraocular pressure (IOP). During the course of this experiment, cupping of the optic nerve head, wedge-shaped retinal nerve fiber layer defects, and halo glaucomatosus developed, all of which are defects that are similar to those seen clinically in primary open-angle glaucoma. The IOP required for this fundus change was 25, 35, and 43 mmHg, indicating great individual variation. Histological examination revealed localized degeneration, loss of axon bundles, and diffuse thinning of the nerve fiber layer in the area of these wedge-shaped defects in the retinal nerve fiber layer. These results may indicate that the optic-nerve-damaging mechanism, both localized and generalized, is the same in the cynomolgus monkey and in man.     

Visual field defects and normal nerve fiber layer: may they coexist in primary open-angle glaucoma?

The retinal nerve fiber layer (RNFL) is the anatomical structure most sensitive to glaucoma injury. Before a functional loss such as a visual field defect is displayed, a large number of nerve fibers can be damaged. However, there are glaucoma patients in which an apparently normal RNFL coexists with evident visual field defects. A total of 54 eyes affected with primary open-angle glaucoma were studied. Visual field was examined with the Humphrey Field Analyzer (Zeiss) using program 30-2. The Nerve Fiber Analyzer II (Laser Diagnostic Technologies) was used to study the RNFL of these patients. Mean deviation of the visual field ranged from 6 to 31 dB in all eyes that were examined. The average thickness of the RNFL ranged from 20 to 90 microm. According to our previous experience 75 microm was fixed as the cutoff between normal and pathological values of RNFL thickness. We identified 5 eyes with a RNFL thickness over 75 microm and a visual field with a mean deviation over 6 dB; 9% of the studied eyes were found to have a visual field defect with no changes in RNFL. We conclude that not all subjects have the same number of fibers at birth and that it is therefore possible to underestimate the RNFL changes. Our study illustrates that the concept of normal and altered has to be considered as a relative one for all the aspects characterizing the glaucomatous disease.     

Evaluation of retinal nerve fiber layer thickness in the area of apparently normal hemifield in glaucomatous eyes with optical coherence tomography

PURPOSE: The authors investigated the correlation between visual field defects detected by automated perimetry and the thickness of the retinal nerve fiber layer measured with optical coherence tomography, and examined whether there is a decrease in retinal nerve fiber layer thickness in the apparently normal hemifield of glaucomatous eyes. PATIENTS AND METHODS: Forty-one patients with glaucoma and 41 normal control subjects were included in this study. Statistical correlations between the sum of the total deviation of 37 stimuli of each hemifield and the ratio of decrease in retinal nerve fiber layer thickness were evaluated. The statistical difference between the retinal nerve fiber layer thickness of the apparently normal hemifield in glaucomatous eyes and that of the corresponding hemifield in normal subjects was also evaluated. RESULTS: There was a statistically significant correlation in the sum of the total deviation and retinal nerve fiber layer thickness decrease ratio (superior hemifield, P = 0.001; inferior hemifield, P = 0.003). There was no significant decrease in retinal nerve fiber layer thickness in the area that corresponded to the normal visual field in the hemifield defect with respect to the horizontal meridian in glaucomatous eyes (superior side, P = 0.148; inferior side, P = 0.341). CONCLUSIONS: Optical coherence tomography was capable of demonstrating and measuring retinal nerve fiber layer abnormalities. No changes in the retinal nerve fiber layer thickness of the apparently normal hemifield were observed in glaucomatous eyes.     

Quantification of retinal nerve fiber defects in glaucoma: three-dimensional analysis by Heidelberg retina tomograph

PURPOSE: To describe a new method of quantifying retinal nerve fiber layer defects (NFLD) in glaucomatous eyes using the Heidelberg Retina Tomograph (HRT).METHODS: Mean tomographic images including the optic disc and peripapillary area were constructed using HRT. An image field of 15 degrees x 15 degrees or 20 degrees x 20 degrees was used for the NFLD analysis. Data on the nerve fiber layer thickness was collected and further analyzed circumferentially across the NFLD at a position 500 microm away from the optic disc margin. We studied 31 patients with early to moderate open-angle glaucoma, ie, with visual field defects appearing earlier than stage 3 of the modified Aulhorn-Greve classification. We determined the width (W), maximum depth (D), and cross-sectional area of the NFLD (A), and we identified correlations between these parameters and the visual field indices from Humphrey Visual Field tests, mean deviation (MD) and corrected pattern standard deviation (CPSD).RESULTS: NFLD parameters could be obtained from 20 of 31 eyes (65%). There was a statistically significant correlation between the D and A parameters, and between these parameters and the maximum depression threshold in the corresponding visual field. No significant correlation was found between the NFLD parameters, the global visual field indices (MD, CPSD) and the mean value of the total deviation (TD) in the corresponding hemifield visual field.CONCLUSIONS: A cross-sectional NFLD image can be obtained using HRT. Among the three NFLD parameters, maximum depth (D), and area under the surface (A) correlated well with the visual field threshold.     

The early structural and functional disturbances of chronic open-angle glaucoma. Robert N. Shaffer lecture

The earliest psychophysical disturbances in color vision, foveal sensitivity, spatial and temporal contrast sensitivity precede nerve fiber bundle defects of the visual field in glaucoma. Optic nervehead changes such as enlargement of the physiological cup, as well as retinal nerve fiber layer losses, also precede visual field defects. Which of these is the earliest change has not yet been recognized. Evidence for more than one mechanism of damage in glaucoma is also presented.