Early Glaucomatous Eyes Research Articles

Viscoelastic Material Properties of the Peripapillary Sclera in Normal and Early-Glaucoma Monkey Eyes

To test the hypothesis that changes in the viscoelastic material properties of peripapillary sclera are present within monkey eyes at the onset of early experimental glaucoma detected by confocal scanning laser tomography (CSLT). Short-term (3-9 weeks), moderate (< or =44 mm Hg) intraocular pressure (IOP) elevation was induced in one eye of each of eight male monkeys by lasering the trabecular meshwork. This procedure generated early experimental glaucoma, defined as the onset of CSLT-detected optic nerve head (ONH) surface change, in the treated eye. Scleral tensile specimens from the superior and inferior quadrants of the eight early-glaucoma eyes were subjected to uniaxial stress relaxation and tensile tests to failure and the results compared with similar data obtained in a previous study of 12 normal (nonglaucomatous) eyes. Linear viscoelastic theory was used to characterize viscoelastic material property parameters for each specimen. Differences in each parameter due to quadrant and treatment were assessed by analysis of variance (ANOVA). Peripapillary sclera from the early-glaucoma eyes exhibited an equilibrium modulus (7.46 +/- 1.58 MPa) that was significantly greater than that measured in normal eyes (4.94 +/- 1.22 MPa; mean +/- 95% confidence interval, P < 0.01, ANOVA). Quadrant differences were not significant for the viscoelastic parameters within each treatment group. The long-term viscoelastic material properties of monkey peripapillary sclera are altered by exposure to moderate, short-term, chronic IOP elevations and these alterations are present at the onset of CSLT-detected glaucomatous damage to the ONH. Damage to and/or remodeling of the extracellular matrix of these tissues may underlie these changes in scleral material properties.

Identifying early glaucoma with optical coherence tomography

PurposeTo evaluate performance of optical coherence tomography (OCT) for detection of early glaucoma. DesignObservational case-control study. MethodsSetting: University-based tertiary care center. Study Population: One eye from 50 normals, 42 glaucoma suspects, and 59 early glaucoma patients meeting the following criteria: visual field (VF) mean deviation ≥−6.00 dB, age ≥40 years, spherical refractive error ≤5 diopters, astigmatism ≤3 diopters, and visual acuity ≥20/30. Observation Procedure: Early glaucoma by VF (EGVF) was described as repeatable abnormal achromatic VFs based on predefined criteria. Glaucoma suspects (GS) were defined as presence of glaucomatous disk appearance with normal achromatic VFs. Outcome Measures: Average nerve fiber layer thickness (NFLT) and NFLT in each of four quadrants and 12 clock-hour sectors. Receiver operating characteristic curves and sensitivity and specificity were used to assess the performance of OCT. ResultsAverage NFLT was 128.4 ± 15.4, 102.0 ± 25.4, and 86.5 ± 31.5 μm in normal, GS, and EGVF eyes, respectively. Normal eyes were different from both glaucoma groups (P < .001); NFLT in the superior quadrant and at the 11 o'clock position had the highest area under the receiver operating characteristic curve (.840 and .933) in the GS and EGVF groups (P = .03). The sensitivity of the OCT for detection of glaucoma was 71% and 85% for the GS and EGVF groups with specificity fixed at 90%. ConclusionThe OCT discriminates well between eyes with early perimetric glaucoma and normal eyes. However, its performance is less adequate in eyes with suspicious disk and normal VFs.

Ability of scanning laser polarimetry (GDx) to discriminate among early glaucomatous, ocular hypertensive and normal eyes in the Korean population.

We investigated the ability of the GDx-Nerve Fiber Analyzer (NFA) to discriminate between normal and early glaucomatous eyes among Korean individuals by reviewing the medical records of 217 consecutive subjects: 61 early glaucoma patients, 68 ocular hypertensive patients, and 88 normal subjects. GDx parameters were compared using ANOVA. The Receiver Operating Characteristics (ROC) curve for each GDx-NFA variable was used to diagnose each parameter, and Pearson correlation coefficients were calculated to assess the association between GDx-NFA parameters and visual field indices in early glaucoma. The best GDx parameters to discriminate between early glaucomatous and normal subjects were the number, maximum modulation, ellipse modulation and inferior ratio (i.e. area under the ROC curve > 0.8). A value for the Number of equal to or greater than 27 was optimal for detecting early glaucoma, with a sensitivity of 80.3% and specificity of 80.7%. In addition, symmetry was positively correlated with the corrected pattern standard deviation (CPSD) among visual field indices in early glaucoma.

Analysis of macular volume in normal and glaucomatous eyes using optical coherence tomography

Purpose To evaluate macular volume in normal and glaucomatous eyes using optical coherence tomography (OCT). Design Case control study. Methods The authors assessed 272 eyes of 164 subjects as part of an institutional study at New England Eye Center in Boston, Massachusetts; 202 eyes were in the study group and 70 eyes in the control group. Eyes were categorized as normal (70 eyes of 43 subjects), glaucoma suspect (70 eyes of 44 subjects), early glaucoma (70 eyes of 47 subjects), or advanced glaucoma (62 eyes of 43 subjects). Subjects underwent analysis with the commercially available OCT1 unit. Optical coherence tomography macular neurosensory retinal thickness maps were used to calculate macular volume for comparison to Humphrey visual field testing, intraocular pressure measurement, and stereo biomicroscopy of the optic nerve head and nerve fiber layer. Results Using repeated measures regression, macular volume in normal (2.37 ± 0.11 mm 3) glaucoma suspect (2.33 ± 0.16 mm 3), and early glaucoma eyes (2.27 ± 0.13 mm 3) was significantly greater than in eyes with advanced glaucoma (2.12 ± 0.23 mm 3, P = .0001, P = .0001, and P = .0008, respectively). Macular volume in normal eyes was significantly greater than in early glaucoma eyes ( P = .01). Conclusions Optical coherence tomography retinal macular volume correlates with known structural defects of glaucoma, providing a potential objective and quantitative parameter for evaluation. Our data show a significant difference in macular volume between normal, glaucoma suspect, and early glaucoma eyes, compared with advanced glaucomatous eyes as well as between normal and early glaucomatous eyes. This correlates with a trend of decreasing macular volume in eyes with more advanced disease.

Evaluation of the glaucomatous damage on retinal nerve fiber layer thickness measured by optical coherence tomography

Purpose To evaluate the relationship between visual field and retinal nerve fiber layer (RNFL) thickness measured by optical coherent tomography (OCT) and to assess the diagnostic ability of OCT to distinguish between early glaucomatous or glaucoma-suspect eyes from normal eyes. Design Retrospective, non-randomized, cross-sectional study. Methods A total of 160 eyes of 120 normal Japanese adults, 23 eyes of 16 patients with ocular hypertension, 38 eyes of 35 glaucoma-suspect patients, and 237 glaucomatous eyes of 140 glaucoma patients were enrolled in the study. The glaucoma group included 89 early glaucomatous eyes. Thickness of the RNFL around the optic disk was determined with three 3.4-mm diameter circle OCT scans. Average and segmental RNFL thickness values were compared among all groups. The correlation between mean deviation and RNFL thickness in glaucomatous eyes was also analyzed. Receiver operating characteristic (ROC) curve area was calculated to discriminate normal eyes from early glaucomatous or glaucoma-suspect eyes. Results A significant relationship existed between the mean deviation and RNFL thickness in all parameters excluding the 3-o’clock area. The average RNFL thickness had the strongest correlation in all parameters (r = −0.729, P < .001). Retinal nerve fiber layer thickness at the 7-o’clock inferotemporal segment had the widest areas under the ROC curves in all parameters for early glaucomatous eyes (0.873). Conclusion Measurement of RNFL thickness by OCT is useful in detecting early RNFL damage. Furthermore, OCT measurements of RNFL thickness may provide clinically relevant information in monitoring glaucomatous changes.

Deformation of the lamina cribrosa and anterior scleral canal wall in early experimental glaucoma.

To test the hypothesis that pathophysiologic deformation of the lamina cribrosa and anterior scleral canal wall underlies the onset of confocal scanning laser tomography (CSLT)-detected optic nerve head (ONH) surface change in early experimental glaucoma. Both eyes of four normal (two normal eyes) monkeys and four with early glaucoma (one eye with laser-induced IOP elevation, observed until the onset of CSLT-detected ONH surface change) were enucleated immediately after death and immersion fixed at IOP 0 mm Hg. In an additional four normal monkeys and five with early glaucoma, both eyes were cannulated, and IOP set to 10 mm Hg in one normal eye and either 30 or 45 mm Hg in the other (normal or early-glaucoma) eye. After 15 to 80 minutes of acute IOP elevation, these nine monkeys were perfusion-fixed. Within images of serial sagittal sections of the ONH tissues in all 17 monkeys, anterior lamina cribrosa position, laminar thickness, and scleral canal diameter were measured. For each parameter, differences between the two eyes of each monkey and between treatment groups were assessed by ANOVA. Within the eyes of the eight monkeys with IOP 0 mm Hg, the lamina cribrosa was posteriorly displaced and thicker and the scleral canal was enlarged at Bruch's membrane and at the anterior laminar insertion in the early-glaucoma eyes compared with the contralateral normal eyes (plastic deformation). Within the high-IOP normal eyes, the lamina cribrosa was posteriorly displaced compared with that in the low-IOP normal eyes, but there were no significant differences in laminar thickness or scleral canal diameter (normal compliance). Within the high-IOP early-glaucoma eyes, the lamina cribrosa was posteriorly displaced and thicker and the scleral canal enlarged, compared with both low-IOP normal eyes and high-IOP normal eyes (hypercompliant deformation). Differences in laminar position between the high-IOP early-glaucoma eyes and the contralateral low-IOP normal eyes (hypercompliant plus plastic deformation) were more than eight times greater than the differences between the high-IOP normal eyes and the contralateral low-IOP normal eyes (normal compliance). Both plastic (permanent) and hypercompliant deformation of the lamina cribrosa and anterior scleral canal wall are present in young adult monkey eyes with early experimental glaucoma. These findings suggest that damage to the ONH connective tissues occurs early in the monkey model of experimental glaucoma.

Use of the GDx to detect differences in retinal nerve fibre layer thickness between normal, ocular hypertensive and early glaucomatous eyes

The GDx is a scanning laser polarimeter that has been developed to allow the quantitative analysis of retinal nerve fibre layer (RNFL) thickness. The purpose of this study was to determine whether differences in the RNFL thickness between normal, ocular hypertensive and glaucomatous eyes could be detected using the GDx. RNFL analysis was carried out using the GDx on 33 normal, 145 ocular hypertensive (OHT) and 44 glaucomatous (POAG) eyes. The inclusion criteria for entry into the study did not include the clinical appearance of the RNFL or optic disc, thus eliminating an important source of selection bias. The Kruskal-Wallis one-way analysis of variance was used to determine whether any significant differences existed among the groups in mean total and quadrantic RNFL thickness. When significant differences were found, specific inter-group analysis was carried out using the Mann-Whitney U-test. Significant differences in RNFL thickness were found for the mean total, superior and inferior quadrant values between normals and OHT eyes as compared with POAG eyes. No significant differences were found for these values between the normal and OHT eyes. Analysis of RNFL thickness using the GDx was able to detect differences between POAG eyes compared with normal and OHT eyes, although there was considerable overlap between groups. Further assessment of the technique is required to determine whether it may be useful in screening for the presence of early glaucomatous damage.

Blue-on-Yellow Perimetry Using an Armaly Glaucoma Screening Program

The purpose of the present investigation was to determine whether blue-on-yellow (B/Y) perimetry using a screening program can detect early glaucomatous change before it is evident with standard white-on-white (W/W) screening tests. The subjects included 25 normal, 20 ocular-hypertensive and 27 early glaucomatous eyes. From our results, even in normal subjects, B/Y perimetry alone demonstrated abnormal points in the nasal field in 10 eyes (40%). The Armaly central screening program was thought to be superior to the Armaly full-field program, because the former has less probabilities to detect a false-positive scotoma in the nasal field than the latter. In glaucomatous eyes, more abnormal points were detected by B/Y perimetry than by W/W perimetry. The screening program of B/Y perimetry is more advantageous than conventional tests in detecting early glaucomatous visual field defects.

RA/DA cumulative curve analysis of local and diffuse neuroretinal rim area damage in glaucoma patients

AIMTo evaluate the validity of cumulative rim/disc area (RA/DA) curve analysis as a clinical tool for the identification of glaucoma induced optic disc pathology.METHODS71 normal and 83 glaucomatous eyes were...