Effect of retinal nerve fibre loss on the optic nerve head configuration in early glaucoma

Schizophrenia and the retina: Towards a 2020 perspective

BACKGROUND

Differences between people with schizophrenia and psychiatrically healthy controls have been consistently demonstrated on measures of retinal function such as electroretinography (ERG), and measures of retinal structure such as optical coherence tomography (OCT). Since our 2015 review of this literature, multiple new studies have been published using these techniques. At the same time, the accumulation of data has highlighted the "fault lines" in these fields, suggesting methodological considerations that need greater attention in future studies.

METHODS

We reviewed studies of ERG and OCT in schizophrenia, as well as data from studies whose findings are relevant to interpreting these papers, such as those on effects of the following on ERG and OCT data: comorbid medical conditions that are over-represented in schizophrenia, smoking, antipsychotic medication, substance abuse, sex and gender, obesity, attention, motivation, and influences of brain activity on retinal function.

RESULTS

Recent ERG and OCT studies continue to support the hypothesis of retinal structural and functional abnormalities in schizophrenia, and suggest that these are relevant to understanding broader aspects of pathophysiology, neurodevelopment, and neurodegeneration in this disorder. However, there are differences in findings which suggest that the effects of multiple variables on ERG and OCT data need further clarification.

CONCLUSIONS

The retina, as the only component of the CNS that can be imaged directly in live humans, has potential to clarify important aspects of schizophrenia. With greater attention to specific methodological issues, the true potential of ERG and OCT as biomarkers for important clinical phenomena in schizophrenia should become apparent.

The impact of disc hemorrhage studies on our understanding of glaucoma: a systematic review 50 years after the rediscovery of disc hemorrhage

PURPOSE OF REVIEW

To trace the influence of disc hemorrhage studies on our understanding of glaucoma.

SOURCES

Major articles published during the last 50 years since the rediscovery of disc hemorrhage were identified. A total of 196 articles were selected from 435 articles retrieved using the keywords glaucoma and disc hemorrhage as of August 9 2018 from PubMed.

RECENT FINDINGS

The main characteristics of disc hemorrhage, including its morphology, recurrence rate, duration, increased incidence in glaucoma, and role in the progression of normal tension glaucoma was well understood by the year 2000. Since then, studies have focused on more sophisticated and accurate methods of elucidating both structural and functional progression, with special attention to the role of the lamina cribrosa. Nevertheless, both the mechanism of disc hemorrhage development and its fuller relationship with glaucoma remain unclear. Disc hemorrhage research requires careful study of glaucomatous optic neuropathy. This has been facilitated by recent advances in optical coherence tomography (OCT) angiography and other OCT technologies. Furthermore, animal studies of disc hemorrhage promise new insights into glaucomatous optic neuropathy.

Mapping the Structure-Function Relationship in Glaucoma and Healthy Patients Measured with Spectralis OCT and Humphrey Perimetry

Purpose

To study the structure-function relationship in glaucoma and healthy patients assessed with Spectralis OCT and Humphrey perimetry using new statistical approaches.

Materials and Methods

Eighty-five eyes were prospectively selected and divided into 2 groups: glaucoma (44) and healthy patients (41). Three different statistical approaches were carried out: (1) factor analysis of the threshold sensitivities (dB) (automated perimetry) and the macular thickness (μm) (Spectralis OCT), subsequently applying Pearson's correlation to the obtained regions, (2) nonparametric regression analysis relating the values in each pair of regions that showed significant correlation, and (3) nonparametric spatial regressions using three models designed for the purpose of this study.

Results

In the glaucoma group, a map that relates structural and functional damage was drawn. The strongest correlation with visual fields was observed in the peripheral nasal region of both superior and inferior hemigrids (r = 0.602 and r = 0.458, resp.). The estimated functions obtained with the nonparametric regressions provided the mean sensitivity that corresponds to each given macular thickness. These functions allowed for accurate characterization of the structure-function relationship.

Conclusions

Both maps and point-to-point functions obtained linking structure and function damage contribute to a better understanding of this relationship and may help in the future to improve glaucoma diagnosis.

The relationship between HDAC6, CXCR3, and SIRT1 genes expression levels with progression of primary open-angle glaucoma

BACKGROUND

Primary open-angle glaucoma (POAG) belongs to neurodegenerative diseases. Its etiology is not fully understood. However, a lot of reports have indicated that many biochemical molecules are involved in the retinal ganglion cell damage. Therefore, the purpose of this study was to evaluate a relationship between HDAC6, CXCR3, and SIRT1 genes expression levels with the occurrence risk of POAG and its progression.

MATERIALS AND METHODS

The study included 34 glaucoma patients and 32 subjects without glaucoma symptoms. RNA was isolated from peripheral blood lymphocytes. Level of mRNA expression was determined by real-time PCR method.

RESULTS

Our results have shown significant association of the HDAC6 and SIRT1 expression levels with progression of POAG according to rim area (RA) value, p = 0.041; p = 0.012. Moreover, the analysis of the CXCR3 expression level showed a correlation with progression of POAG based on RA and cup disc ratio (c/d) value, p = 0.006 and p = 0.012, respectively.

CONCLUSIONS

The expression level of HDAC6, CXCR3, and SIRT1 genes may be involved in the progression of POAG.

Diagnostic Capability of Peripapillary Three-dimensional Retinal Nerve Fiber Layer Volume for Glaucoma Using Optical Coherence Tomography Volume Scans

PURPOSE

To determine the diagnostic capability of peripapillary 3-dimensional (3D) retinal nerve fiber layer (RNFL) volume measurements from spectral-domain optical coherence tomography (OCT) volume scans for open-angle glaucoma (OAG).

DESIGN

Assessment of diagnostic accuracy.

METHODS

Setting: Academic clinical setting.

STUDY POPULATION

Total of 180 patients (113 OAG and 67 normal subjects).

OBSERVATION PROCEDURES

One eye per subject was included. Peripapillary 3D RNFL volumes were calculated for global, quadrant, and sector regions, using 4 different-size annuli. Peripapillary 2D RNFL thickness circle scans were also obtained.

MAIN OUTCOME MEASURES

Area under the receiver operating characteristic curve (AUROC) values, sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratios.

RESULTS

Among all 2D and 3D RNFL parameters, best diagnostic capability was associated with inferior quadrant 3D RNFL volume of the smallest annulus (AUROC value 0.977). Otherwise, global 3D RNFL volume AUROC values were comparable to global 2D RNFL thickness AUROC values for all 4 annulus sizes (P values: .0593 to .6866). When comparing the 4 annulus sizes for global RNFL volume, the smallest annulus had the best AUROC values (P values: .0317 to .0380). The smallest-size annulus may have the best diagnostic potential, partly owing to having no areas excluded for being larger than the 6 × 6 mm² scanned region.

CONCLUSION

Peripapillary 3D RNFL volume showed excellent diagnostic performance for detecting glaucoma. Peripapillary 3D RNFL volume parameters have the same or better diagnostic capability compared to peripapillary 2D RNFL thickness measurements, although differences were not statistically significant.

Association of Structural and Functional Measures With Contrast Sensitivity in Glaucoma

PURPOSE

To test the hypothesis that structural and functional measures predict contrast sensitivity (CS) outcomes in glaucomatous eyes.

DESIGN

Cross-sectional prospective study.

METHODS

One hundred five eyes of 65 patients who underwent macular spectral-domain optical coherence tomography imaging, 24-2 standard achromatic visual fields (VF), and CS measurement on the same day were enrolled. Association of CS at 4 spatial frequencies (3, 6, 12, and 18 cycles per degree, cpd) with structural and functional outcomes was explored with correlation and regression analyses.

RESULTS

The median (IQR) 24-2 visual field mean deviation was -7.6 (-11.1 to -3.0). Significant correlations were found between CS at 6 cpd and ganglion cell/inner plexiform layer thickness at inferotemporal and inferonasal macular sectors (ρ = 0.222, P = .023 and ρ = 0.209, P = .032, respectively). CS at 6 cpd demonstrated higher correlations with full macular thickness measurements, the strongest of which was with the central macular thickness in the superior 6 × 3-degree region (ρ = 0.311, P = .001). Contrast sensitivity at 6 cpd also had the strongest correlation with mean deviation of the 4 central VF points (ρ = -0.420; P < .001). There was a significant correlation between logMAR visual acuity and contrast sensitivity at 6, 12, and 18 cpd (ρ = -0.306, ρ = -0.348 and ρ = -0.241, P < .013, respectively).

CONCLUSIONS

Structural and functional measures showed a fair relationship with contrast sensitivity. This association was most prominent between full-thickness macular measures or central VF parameters and CS at 6 cpd. Contrast sensitivity was not a reliable surrogate for glaucoma severity in this cross-sectional study.

Evaluation of Peripapillary Nerve Fiber Layer after Dexamethasone Implantation (Ozurdex) in Branch Retinal Vein Occlusions

Purpose. To evaluate the peripapillary retinal nerve fiber layer (RNFL) thicknesses of patients treated with intravitreal Ozurdex implant due to branch retinal vein occlusion (BRVO) related macular edema (ME). Methods. Thirty-three eyes of 33 patients treated with Ozurdex implant due to ME associated with BRVO were included in the study. Ophthalmic examinations including determination of best corrected visual acuity (BCVA), measurement of intraocular pressure (IOP), and central macular thickness (CMT) and peripapillary RNFL assessment with optical coherence tomography (OCT) were performed before the injection of Ozurdex implant and during the 6-month follow-up period after the injection. Results. The mean age was 55.2 ± 7.4 (range: 40-68) years. The BCVAs were significantly increased and CMTs were significantly decreased at month 3 and month 6 visits compared to baseline values. The mean IOP was significantly increased from baseline at day 1, week 1, and month 1 visits (p₁ = 0.008, p₂ = 0.018, and p₃ = 0.022, resp.). The average and inferior quadrant peripapillary RNFL thicknesses were significantly reduced at month 6 control visit compared to baseline values (both p < 0.001). Conclusions. Ozurdex implant improved the BCVA and reduced the CMT in the eyes with RVO related ME. However, IOP elevations occurred within the first month after the injection and the average and inferior quadrant RNFL thinning was found six months after the injection. Further controlled studies are warranted.

Effect of Refractive Status and Axial Length on Peripapillary Retinal Nerve Fibre Layer Thickness: An Analysis Using 3D OCT

BACKGROUND

Accurate measurement of retinal nerve fiber layer (RNFL) is now possible with the high resolution optical coherence tomography (OCT). Effect of refractive status of the eye on RNFL thickness may be relevant in the diagnosis of glaucoma and other optic nerve diseases.

AIM

To assess the RNFL thickness and compare its correlation with refractive status and axial length of the eye.

MATERIAL AND METHODS

Three hundred eyes of 150 patients were included in this study, who underwent RNFL analysis using TOPCON 3D OCT 2000. Analysis of variance has been used to find the significance of study parameters between the study groups.

RESULTS

The study showed that refractive status/axial length affected the peripapillary RNFL thickness significantly.

CONCLUSION

The study suggests that the diagnostic accuracy of OCT may be improved by considering refractive status and axial length of the eye when RNFL is measured.

Imaging Glaucomatous Damage Across the Temporal Raphe

PURPOSE

To image and analyze anatomical differences at the temporal raphe between normal and glaucomatous eyes using adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography (OCT), and to relate these differences to visual field measurements.

METHODS

Nine glaucomatous eyes of 9 patients (age 54-78 years, mean deviation of visual field [MD] -5.03 to -0.20 dB) and 10 normal eyes of 10 controls (age 54-81, MD -1.13 to +1.39 dB) were enrolled. All the participants were imaged in a region that was centered approximately 9° temporal to the fovea. The size of imaging region was at least 10° vertically by 4° horizontally. The raphe gap, defined as the distance between the superior and inferior retinal nerve fiber layer (RNFL) bundles, was measured. A bundle index was computed to quantify the relative reflectivity and density of the nerve fiber bundles. We also measured thickness of the ganglion cell complex (GCC) and RNFL.

RESULTS

The raphe gap was larger in glaucomatous eyes than control eyes. Specifically, eight glaucomatous eyes with local averaged field loss no worse than -3.5 dB had larger raphe gaps than all control eyes. The bundle index, GCC thickness, and RNFL thickness were on average reduced in glaucomatous eyes, with the first two showing statistically significant differences between the two groups.

CONCLUSIONS

Structural changes in the temporal raphe were observed and quantified even when local functional loss was mild. These techniques open the possibility of using the raphe as a site for glaucoma research and clinical assessment.

Population-based evaluation of retinal nerve fiber layer, retinal ganglion cell layer, and inner plexiform layer as a diagnostic tool for glaucoma

PURPOSE

We determined the glaucoma screening performance of regional optical coherence tomography (OCT) layer thickness measurements in the peripapillary and macular region, in a population-based setting.

METHODS

Subjects (n = 1224) in the Rotterdam Study underwent visual field testing (Humphrey Field Analyzer) and OCT of the macula and optic nerve head (Topcon 3-D OCT-1000). We determined the mean thicknesses of the retinal nerve fiber layer (RNFL), retinal ganglion cell layer (RGCL), and inner plexiform layer for regions-of-interest; thus, defining a series of OCT parameters, using the Iowa Reference Algorithms. Reference standard was the presence of glaucomatous visual field loss (GVFL); controls were subjects without GVFL, an intraocular pressure (IOP) of 21 mm Hg or less, and no positive family history for glaucoma. We calculated the area under the receiver operating characteristics curve (AUCs) and the sensitivity at 97.5% specificity for each parameter.

RESULTS

After excluding 23 subjects with an IOP > 21 mm Hg and 73 subjects with a positive family history for glaucoma, there were 1087 controls and 41 glaucoma cases. Mean RGCL thickness in the inferior half of the macular region showed the highest AUC (0.85; 95% confidence interval [CI] 0.77-0.92) and sensitivity (53.7%; 95% CI, 38.7-68.0%). The mean thickness of the peripapillary RNFL had an AUC of 0.77 (95% CI, 0.69-0.85) and a sensitivity of 24.4% (95% CI, 13.7-39.5%).

CONCLUSIONS

Macular RGCL loss is at least as common as peripapillary RNFL abnormalities in population-based glaucoma cases. Screening for glaucoma using OCT-derived regional thickness identifies approximately half of those cases of glaucoma as diagnosed by perimetry.

Microstructure of the optic disc pit in open-angle glaucoma

PURPOSE

To investigate the structural and clinical characteristics of the optic disc pit (ODP) in primary open-angle glaucoma (POAG) via enhanced depth imaging (EDI) spectral-domain optical coherence tomography (SD-OCT).

DESIGN

Prospective, observational case series.

PARTICIPANTS

Seventy POAG eyes clinically diagnosed with an ODP via stereo disc photography.

METHODS

Optic discs were scanned using EDI SD-OCT. Serial horizontal and vertical B-scan images covering the optic discs were obtained from each eye. The structural characteristics of the ODP were investigated via 3-dimensional images constructed from the serial B-scans, focusing on the presence of alterations in the contour of the lamina cribrosa (LC) or prelaminar tissue (PLT), in conjunction with associated clinical characteristics.

MAIN OUTCOME MEASURES

The structural characteristics of the ODP and associated clinical characteristics.

RESULTS

In the EDI SD-OCT images, the ODP was viewed as an isolated alteration of the LC (n = 14, 20.0%) or PLT (n = 16, 22.9%) or an alteration of both the LC and PLT (n = 40, 57.1%). Alterations of the LC were located at the mid-periphery near the LC insertion (n = 17) or far periphery adjacent to the LC insertion (n = 37), and the depth of alteration was deep (n = 23), involving nearly full-thickness LC, or shallow (n = 31), with partially visible LC at the base. Fifty-four eyes (77.1%) exhibited parafoveal visual field (VF) defect within 10 degrees of fixation, and in 98.1% of these eyes (53/54) it was spatially associated with the location of ODP. The parafoveal VF defect was more prevalent in eyes with LC alteration than those without (83.3% vs. 56.2%, P = 0.023) and in eyes with deep LC defect than those with shallow defect (95.7% vs. 74.2%, P = 0.036). Disc hemorrhage (32.4% vs. 0.0%, P = 0.008) and peripapillary retinoschisis (18.9 vs. 0.0%, P = 0.055) were more strongly associated with LC alterations located at the far periphery than at the mid-periphery.

CONCLUSIONS

Enhanced depth imaging SD-OCT facilitated visualization of the varied structure of the ODP, which presented as alteration of the LC or PLT or both. The clinical significance of differing characteristics of ODP microstructure remains to be determined.

Scanning laser polarimetry in glaucoma

Glaucoma is an acquired progressive optic neuropathy which is characterized by changes in the optic nerve head and retinal nerve fiber layer (RNFL). White-on-white perimetry is the gold standard for the diagnosis of glaucoma. However, it can detect defects in the visual field only after the loss of as many as 40% of the ganglion cells. Hence, the measurement of RNFL thickness has come up. Optical coherence tomography and scanning laser polarimetry (SLP) are the techniques that utilize the evaluation of RNFL for the evaluation of glaucoma. SLP provides RNFL thickness measurements based upon the birefringence of the retinal ganglion cell axons. We have reviewed the published literature on the use of SLP in glaucoma. This review elucidates the technological principles, recent developments and the role of SLP in the diagnosis and monitoring of glaucomatous optic neuropathy, in the light of scientific evidence so far.

Effect of axial length on retinal nerve fiber layer thickness in children

PURPOSE

To investigate the effect of axial length on peripapillary retinal nerve fiber layer (RNFL) thickness in myopic, hyperopic, and emmetropic eyes in children by Cirrus HD spectral-domain optical coherence tomography (OCT).

METHODS

Subjects were divided into 3 groups according to their refractive status: myopic (n = 36), emmetropic (n = 30), and hyperopic (n = 28) eyes. The RNFL thickness measurements were taken from the superior, inferior, nasal, and temporal quadrants in the peripapillary region by Cirrus HD OCT. Axial length was also determined for each patient.

RESULTS

The myopic eyes had thinner average RNFL and RNFLs of temporal, superior, nasal, and inferior quadrants than the hyperopic eyes (p1<0.001, p2 = 0.004, p3 = 0.011, p4 = 0.006, p5 = 0.033, respectively). In addition, average peripapillary RNFL thickness and RNFL thicknesses of all quadrants had significant negative correlations with axial length. On the other hand, after applying modified Littmann formula for correction of magnification effect, the differences among the 3 groups disappeared (all p>0.05).

CONCLUSIONS

We have shown that axial length and accordingly refractive status influenced peripapillary RNFL thickness measurements by Cirrus HD OCT in children. Therefore, to make a correct diagnosis of glaucoma or other optic neuropathies in children, either axial length-induced magnification effect should be corrected by ophthalmologists or the current Cirrus HD OCT database should be revised taking axial length into consideration.

Glaucoma diagnostics

This thesis addresses several aspects of glaucoma diagnostics from both a clinical and a screening perspective. New instruments for diagnosing glaucoma have been developed over the past years, but little information is available regarding their performance as screening methods and their usefulness in ordinary clinical practice. PURPOSE OF THE RESEARCH UNDERLYING THIS THESIS:  The objectives of this research were as follows: to compare the accuracy of results of analysis of the optic nerve head (ONH) achieved by computerized imaging using the Heidelberg Retina Tomograph (HRT) and by subjective assessment performed by physicians with different degrees of experience of glaucoma (paper III); to evaluate the effect of a continuous medical education (CME) lecture on subjective assessment of the ONH for diagnosis of glaucoma (paper II); to investigate subjective assessment of perimetric test results by physicians with varying knowledge of glaucoma with a trained artificial neural network (ANN) and to compare the certainty of the classifications (paper IV); and to compare the diagnostic performance of time-domain Stratus optical coherence tomography (OCT) with that of spectral-domain Cirrus OCT (paper I), frequency doubling technology (FDT) screening perimetry and scanning laser polarimetry with the GDx variable corneal compensator (VCC) in a random population-based sample and in patients with glaucoma of varying disease severity.

METHODS AND RESULTS

  In evaluation of the ONH, use of the HRT statistical tools, Moorfields regression analysis (MRA) and the Glaucoma Probability Score (GPS) was compared with subjective assessment performed by 45 physicians. Optic nerve head images and photographs from 138 healthy and 97 glaucoma subjects were included. The sensitivity of MRA was higher (87-94%) than that of the average physician (62-82%), considerably greater than that of ophthalmologists with subspecialties other than glaucoma (53-77%) and non-significantly better than that of glaucoma experts (72-88%). Sensitivity achieved by GPS (79-93%) was also greater than that of the average physician. MRA correctly classified all eyes with advanced glaucomatous visual field defects, a result that was not achieved by GPS or even by the glaucoma experts. In eyes with small discs, MRA sensitivity (88%) was comparable with that of glaucoma experts (85%) and much better than that of GPS (50%). Also, the group comprising all physicians provided specificity (75-92%) similar to that of both MRA (69 - 86%) and GPS (72-94%) (Andersson et al. 2011a). A 1-hr CME lecture on ONH assessment led to a significant improvement in sensitivity (from 70% to 80%) and a significant decrease in uncertain assessments (from 22% to 13%), whereas specificity remained unchanged (68%) (Andersson et al. 2011b). A rise in sensitivity was seen in all subgroups of physicians, including glaucoma experts. Thirty physicians assessing standard automated perimetry (SAP) test results as Humphrey Field Analyzer single-field analysis printouts with full StatPac information from 99 patients with glaucoma and 66 healthy subjects were compared with a trained ANN regarding diagnostic performance. ANN reached significantly higher sensitivity (93%) than the average physician (83%), whereas specificity was similar for these two groups (91% and 90%, respectively). Diagnostic accuracy was similar among the different groups of physicians and seemingly rather independent of experience. Sensitivity ranged from 82% in the subgroup of other subspecialists to 87% in the glaucoma expert group, and specificity ranged from 88% among general ophthalmologists to 91% for glaucoma experts. The ANN attained certainty of classification that was in parity with that provided by the glaucoma experts and did not make any completely incorrect classifications of the visual fields (i.e. erroneous classifications were in the borderline zone) (Andersson et al. 2012). From a population-based randomly selected sample (n=308) of older subjects (aged ≥ 50 years) living in southern Sweden, 170 subjects underwent a comprehensive examination that included Stratus OCT, Cirrus OCT, an FDT screening programme and the GDx VCC. The same test protocol was applied to 138 randomized clinical patients with different stages of glaucoma. In the population-based sample, both Stratus and Cirrus OCT showed high diagnostic accuracy with area under the receiver-operating curve (aROC) values close to 1.0 (Bengtsson et al. 2012). Both OCT instruments correctly classified all of the clinical glaucoma patients with advanced disease. FDT screening showed high sensitivity (91%) but erroneously gave normal test results for some eyes with advanced disease. GDx VCC had lower sensitivity (73-92%) and also led to a large proportion of examinations with an atypical retardation pattern that is known to affect the diagnostic efficiency of this instrument.

CONCLUSIONS

  The HRT MRA performed better than most physicians and was consistent with the glaucoma experts. These results suggest that MRA can be a valuable tool for diagnosing glaucoma in ordinary practice, particularly when only a few glaucoma experts are available. Even though MRA provided 100% sensitivity in eyes with advanced glaucoma, it probably does not offer sufficient specificity to make it suitable as a screening method. Continuing medical education on ONH analysis had a small, but positive effect on diagnostic accuracy for glaucoma. An ANN trained to classify visual fields seemed to perform at least as well as most of the participating physicians, whose performances were remarkably similar regardless of their level of experience. This indicates that available tools for interpreting SAP findings are helpful in assessments of visual field test results. However, SAP is associated with learning effects (Heijl et al. 1989) that may entail low specificity for untrained subjects, and hence, it is not an ideal screening method for glaucoma. By comparison, the screening test of FDT is rapid and easy, but it is probably less suitable for screening purpose, because some eyes with advanced glaucoma were missed in this investigation. GDx VCC images for a relatively large number of eyes could not be analysed and is thus not appropriate for screening. The OCT instruments offer both high sensitivity and high specificity, and all eyes with advanced disease were correctly classified as glaucomatous in this evaluation. However, these instruments are still expensive and require special operator skills. Additional development to obtain OCT instrument that is more compact, easier to use and less expensive might render such tomography suitable as a screening tool for glaucoma.

Optimizing the information yield of 3-D OCT in glaucoma

PURPOSE

To determine, first, which regions of 3-D optical coherence tomography (OCT) volumes can be segmented completely in the majority of subjects and, second, the relationship between analyzed area and thickness measurement test-retest variability.

METHODS

Three-dimensional OCT volumes (6 × 6 mm) centered around the fovea and optic nerve head (ONH) of 925 Rotterdam Study participants were analyzed; 44 participants were scanned twice. Volumes were segmented into 10 layers, and we determined the area where all layers could be identified in at least 95% (macula) or 90% (ONH) of subjects. Macular volumes were divided in 2 × 2, 4 × 4, 6 × 6, 8 × 8, or 68 blocks. We placed two circles around the ONH; the ONH had to fit into the smaller circle, and the larger circle had to fit into the segmentable part of the volume. The area between the circles was divided in 3 to 12 segments. We determined the test-retest variability (coefficient of repeatability) of the retinal nerve fiber layer (RNFL) and ganglion cell layer (RGCL) thickness measurements as a function of size of blocks/segments.

RESULTS

Eighty-two percent of the macular volume could be segmented in at least 95% of subjects; for the ONH, this was 65% in at least 90%. The radii of the circles were 1.03 and 1.84 mm. Depending on the analyzed area, median test-retest variability ranged from 8% to 15% for macular RNFL, 11% to 22% for macular RGCL, 5% to 11% for the two together, and 18% to 22% for ONH RNFL.

CONCLUSIONS

Test-retest variability hampers a detailed analysis of 3-D OCT data. Combined macular RNFL and RGCL thickness averaged over larger areas had the best test-retest variability.

A mathematical model for describing the retinal nerve fiber bundle trajectories in the human eye: average course, variability, and influence of refraction, optic disc size and optic disc position

Previously we developed a mathematical model for describing the retinal nerve fiber bundle trajectories in the superior-temporal and inferior-temporal regions of the human retina, based on traced trajectories extracted from fundus photographs. Aims of the current study were to (i) validate the existing model, (ii) expand the model to the entire retina and (iii) determine the influence of refraction, optic disc size and optic disc position on the trajectories. A new set of fundus photographs was collected comprising 28 eyes of 28 subjects. From these 28 photographs, 625 trajectories were extracted. Trajectories in the temporal region of the retina were compared to the existing model. In this region, 347 of 399 trajectories (87%) were within the 95% central range of the existing model. The model was extended to the nasal region. With this extension, the model can now be applied to the entire retina that corresponds to the visual field as tested with standard automated perimetry (up to approximately 30° eccentricity). There was an asymmetry between the superior and inferior hemifields and a considerable location-specific inter-subject variability. In the nasal region, we found two "singularities", located roughly at the one and five o'clock positions for the right optic disc. Here, trajectories from relatively widespread areas of the retina converge. Associations between individual deviations from the model and refraction, optic disc size and optic disc position were studied with multiple linear regression. Refraction (P = 0.021) and possibly optic disc inclination (P = 0.09) influenced the trajectories in the superior-temporal region.

Attenuated age-related thinning of peripapillary retinal nerve fiber layer in long eyes

Purpose

To assess the impact of axial length on the age-related peripapillary retinal nerve fiber layer (RNFL) thinning.

Methods

This cross-sectional observational comparative case series included 172 eyes from 172 healthy Korean subjects. Peripapillary RNFL thickness was measured using an Optic Disc Cube 200 × 200 scan of spectral domain Cirrus HD OCT and the axial length was measured using IOL Master Advanced Technology. In age groups based on decade, the normal ranges of peripapillary RNFL thickness for average, quadrant, and clock-hour sectors were determined with 95% confidence intervals. After dividing the eyes into two groups according to axial length (cut-off, 24.50 mm), the degrees of age-related RNFL thinning were compared.

Results

Among the eyes included in the study, 53 (30.81%) were considered to be long eyes (axial length, 25.04 ± 0.48 µm) and 119 (69.19%) were short-to-normal length eyes (axial length, 23.57 ± 0.60 µm). The decrease in average RNFL thickness with age was less in long eyes (negative slope, -0.12 µm/yr) than in short-to-normal length eyes (negative slope, -0.32 µm/yr) (p < 0.001).

Conclusions

Age-related thinning of peripapillary RNFL thickness is attenuated in long eyes compared to short-to-normal length eyes.

Current concepts in the pathophysiology of glaucoma

Glaucoma, the second leading cause of blindness, is characterized by changes in the optic disc and visual field defects. The elevated intraocular pressure was considered the prime factor responsible for the glaucomatous optic neuropathy involving death of retinal ganglion cells and their axons. Extensive investigations into the pathophysiology of glaucoma now reveal the role of multiple factors in the development of retinal ganglion cell death. A better understanding of the pathophysiological mechanisms involved in the onset and progression of glaucomatous optic neuropathy is crucial in the development of better therapeutic options. This review is an effort to summarize the current concepts in the pathophysiology of glaucoma so that newer therapeutic targets can be recognized. The literature available in the National Medical Library and online Pubmed search engine was used for literature review.

A mathematical description of nerve fiber bundle trajectories and their variability in the human retina

We developed a mathematical model wherein retinal nerve fiber trajectories can be described and the corresponding inter-subject variability analyzed. The model was based on traced nerve fiber bundle trajectories extracted from 55 fundus photographs of 55 human subjects. The model resembled the typical retinal nerve fiber layer course within 20 degrees eccentricity. Depending on the location of the visual field test point, the standard deviation of the calculated corresponding angular location at the optic nerve head circumference ranged from less than 1 degrees to 18 degrees , with an average of 8.8 degrees .

The correlation between visual field defects and focal nerve fiber layer thickness measured with optical coherence tomography in the evaluation of glaucoma

PURPOSE

To study the correlation between known visual field defects and retinal nerve fiber layer (RNFL) thickness detected by optical coherence tomography (OCT) in glaucomatous eyes.

MATERIALS AND METHODS

Visual field parameters and OCT RNFL measurements of 28 eyes of 28 glaucoma patients with various stages of glaucoma were compared with 38 eyes of 38 normal age-matched controls. A perimetric nerve fiber bundle map was built by dividing the visual field area into 21 zones. Mean deviation and pattern standard deviation values within these 21 zones were compared with OCT RNFL thickness measurements in 12 sectors and the results were analyzed.

RESULTS

Average RNFL thickness was 62.90+/-16.56 microm in the glaucoma group and 111.90+/-6.00 microm in the control group (P<0.05). Pattern standard deviation and mean deviation visual field zones and corresponding OCT RNFL thickness sectors were significantly correlated at specific sectors in the glaucoma group (P<0.01).

CONCLUSIONS

Analysis of RNFL thickness in eyes with focal glaucomatous visual field defects showed good structural and functional correlation with OCT. OCT contributes to the identification of focal defects in the RNFL of glaucoma patients.

Comparison of OCT and HRT findings among normal, normal tension glaucoma, and high tension glaucoma

PURPOSE

To evaluate the relationship between optic disc and retinal nerve fiber layer (RNFL) measurements obtained with the optical coherence tomography (OCT) and the Heidelberg retina topography (HRT) in normal, normal tension glaucoma (NTG), and high tension glaucoma (HTG).

METHODS

Normal, NTG and HTG subjects who met inclusion and exclusion criteria were evaluated retrospectively. One hundred seventy eyes of 170 patients (30 normal, 40 NTG, and 100 HTG) were enrolled. Complete ophthalmologic examination, HRT, OCT, and automated perimetry were evaluated.

RESULTS

Disc area, cup area and cup/disc area ratio measured with HRT were significantly different between NTG and HTG (all p < 0.05). Mean RNFL thickness measured by OCT with ascanning diameter of 3.4 mm was larger in NTG than HTG (84.97+/-24.20 micrometer vs. 73.53+/-27.17 micrometer, p = 0.037). Four quadrant RNFL thickness measurements were not significantly different between NTG and HTG (all p > 0.05). Mean deviation and corrected pattern standard deviation measured by automated perimetry was significantly correlated with mean and inferior RNFL thickness in both NTG and HTG (Pearson's r, p < 0.05). Mean RNFL thickness/disc area ratio was significantly larger in HTG than NTG (35.21+/-18.92 vs. 31.30+/-10.91, p = 0.004).

CONCLUSIONS

These findings suggest that optic disc and RNFL damage pattern in NTG may be different from those of HTG.

Heidelberg retina tomograph parameters of the optic disc in eyes with progressive retinal nerve fibre layer defects

PURPOSE

To determine the Heidelberg retina tomograph (HRT) parameters that identify glaucomatous changes in optic nerve head (ONH) topography associated with progression of retinal nerve fibre layer (RNFL) defects.

METHODS

A total of 68 eyes with open-angle glaucoma were included in this retrospective study: 34 eyes showed progression of an RNFL defect during the follow-up period and 34 eyes did not. Successful RNFL photographs and scanning laser tomography examinations with the HRT were taken in all patients at each of three visits. The change in HRT parameter values during follow-up was calculated.

RESULTS

Progression of the RNFL defect was statistically significantly correlated (p = 0.049) with only one topographic ONH parameter, the cup shape measure. The best combination of two parameters (p = 0.009) included the maximum cup depth and the linear cup : disc area ratio; the best combination of three parameters (p = 0.007) included the maximum cup depth, the linear cup : disc area ratio and the horizontal cup : disc area ratio. Sensitivity and specificity values were 52.9% and 73.5%, respectively, for the cup shape measure, 70.6% and 73.5%, respectively, for the two-parameter combination, and 76.5% and 79.4%, respectively, for the three-parameter combination. The areas under the receiver operating characteristic curve were 0.617, 0.724 and 0.753, respectively.

CONCLUSIONS

The results indicate that the HRT parameters may be used to detect small ONH changes associated with progression of the RNFL defect. With the exception of the cup shape measure, the parameters which provide the best correlation with progression differ from those considered optimal for recognizing the presence or absence of glaucoma.

Using red-free monochromatic conversions of nonmydriatic digital fundus images

PURPOSE

To compare three types of digital images for assessment of retinal nerve fiber layer (RNFL) defects: red-free RNFL images, color nonmydriatic images, and digitally converted nonmydriatic red-free fundus images.

DESIGN

Diagnostic test comparison.

METHODS

Ninety-five image sets of three type images were evaluated. Converted images were acquired from nonmydriatic digital images by converting them into red-free, monochromatic images with graphics software. Taking RNFL images as standards, the sensitivities/specificities of nonmydriatic digital color and converted images were evaluated for detecting wedge-shaped defect (WSD) or diffuse atrophy.

RESULTS

In terms of WSD, the sensitivity/specificity of converted images were 85.7%/95.5%, and those of nonmydriatic were 83.9%/91.0%. Regarding diffuse atrophy, the sensitivity/specificity of converted images were 60.0%/97.8%, and those of nonmydriatic were 60.0%/98.9%. Intragrader/intergrader agreements for converted images were 0.849/0.793 (WSD) and 0.417/0.614 (diffuse atrophy).

CONCLUSIONS

Converted nonmydriatic fundus images without pupillary dilation are as effective as conventional red-free RNFL images for detecting WSD.

Comparison of glaucomatous parameters in normal, ocular hypertensive and glaucomatous eyes using optical coherence tomography 3000

This study was performed to evaluate optic disc appearance, retinal nerve fiber layer (RNFL) thickness, and macular thickness in normal, ocular hypertensive (OHT) and glaucomatous eyes using optical coherence tomography (OCT) 3000. One hundred fifty-eight eyes of 167 consecutive subjects were enrolled: 60 normal, 53 OHT, and 54 glaucomatous. OCT topographic parameters of cup diameter, cup area, rim area, and cup/disc area ratio were significantly less in OHT eyes than in normal eyes and were significantly less in glaucomatous eyes than in normal and OHT eyes. RNFL was significantly thinner in OHT eyes than in normal eyes in the inferior quadrant, and in glaucomatous eyes than in OHT and normal eyes in the mean and for all four quadrants. Macular thickness was significantly thinner in glaucomatous eyes than in OHT and normal eyes throughout all subdivisions. Optic disc parameters, and RNFL and macular thickness measurements made with OCT may be useful in the clinical assessment of glaucoma.

Quantitative Analysis of Retinal Nerve Fiber Layer Thickness of Normal Children and Adolescents

PURPOSE

To determine the normal range of retinal nerve fiber layer (RNFL) thickness of normal children and adolescents by optical coherence tomography (OCT).

METHODS

This study analyzed 144 eyes of 72 normal children and adolescents by OCTIII (Zeiss-Humphrey, San Leandro, CA., USA) and the results were compared with the RNFL thickness of Korean adults.

RESULTS

The mean RNFL thickness of the 72 normal children and adolescents was 105.53 +/- 10.33 microm. The mean values for left and right eyes were 104.28 +/- 7.68 microm and 106.79 +/- 12.98 microm, respectively. There was no significant difference in mean RNFL thickness between the 4 quadrants of the left and right eyes (p=0.926). Additionally, the mean RNFL thickness showed a similar size pattern regardless of age (p=0.99). RNFL thickness was found to be greater in adults than in children or adolescents, although the difference was not statistically significant (p=0.295). Likewise, no significant difference was found with gender (p=0.822) or in the pattern of RNFL thickness of 12 sectors between children and adults (p=0.08).

CONCLUSIONS

This study reports RNFL thickness, as determined by OCT, for normal children and adolescents. We found this measurement method to be suitable for the early diagnosis of glaucoma and to the examination of its progression in these subjects. The findings could be used as clinical parameters for adolescent glaucoma.

Nocturnal hypotension: role in glaucoma progression

The role of systemic blood pressure in glaucomatous damage remains undefined, with systemic hypertension and hypotension being implicated in different studies. We have previously reported that the physiologic nocturnal blood pressure "dip" may be exaggerated in some glaucoma patients with progressive field loss. A 24-hour ambulatory blood pressure recording was originally performed on 84 patients with glaucoma. The mean result across all our glaucoma patients were within the ranges reported in the literature for normal subjects. The normal-tension glaucoma and primary open-angle glaucoma groups did not differ significantly in blood pressure variables. Nocturnal blood pressure variables were lower in the patients with progressive field defects compared to those with stable visual fields. To determine long-term outcomes in these patients, we reevaluated the visual fields of the original 84 patients studied. In 70 patients with long-term visual field data (mean, 5.1 years), those who had shown greater nocturnal blood pressure dips were more likely to have shown field progression at some stage, despite good intraocular pressure control. Patients who had field progression showed significantly lower nocturnal blood pressure variables, with the dips of the systolic, diastolic, and mean arterial pressure significantly larger (systolic dip, P = 0.01). They also had a greater history of disk hemorrhages. A review of other 24-hour blood pressure studies in the literature shows that most are in agreement with these findings. The nocturnal reduction in blood pressure may, therefore, be an additional risk factor in glaucoma patients.

Evaluation of focal defects of the nerve fiber layer using optical coherence tomography

OBJECTIVE

To analyze glaucomatous eyes with known focal defects of the nerve fiber layer (NFL), relating optical coherence tomography (OCT) findings to clinical examination, NFL and stereoscopic optic nerve head (ONH) photography, and Humphrey 24-2 visual fields.

DESIGN

Cross-sectional prevalence study.

PARTICIPANTS

The authors followed 19 patients in the study group and 14 patients in the control group.

INTERVENTION

Imaging with OCT was performed circumferentially around the ONH with a circle diameter of 3.4 mm using an internal fixation technique. One hundred OCT scan points taken within 2.5 seconds were analyzed.

MAIN OUTCOME MEASURES

Measurements of NFL thickness using OCT were performed.

RESULTS

In most eyes with focal NFL defects, OCTs showed significant thinning of the NFL in areas closely corresponding to focal defects visible on clinical examination, to red-free photographs, and to defects on the Humphrey visual fields. Optical coherence tomography enabled the detection of focal defects in the NFL with a sensitivity of 65% and a specificity of 81%.

CONCLUSION

Analysis of NFL thickness in eyes with focal defects showed good structural and functional correlation with clinical parameters. Optical coherence tomography contributes to the identification of focal defects in the NFL that occur in early stages of glaucoma.

Laser scanning tomography of localised nerve fibre layer defects

AIMS

Retinal nerve fibre layer photography is a well established method to qualitatively document early structural changes which might be induced by primary open angle glaucoma. The aim was to analyse localised retinal nerve fibre layer (RNFL) defects in a new quantitative way with respect to surface topography, defect width, and surface reflectivity by means of the technique of confocal scanning laser tomography.

METHODS

12 eyes of 12 patients with a localised RNFL defect documented in RNFL photographs and a normal appearance of the optic disc were enrolled in the study. Using confocal laser scanning tomography (Heidelberg retina tomograph, HRT) a series of 32 optical section images from different focal planes of the retina at the site of the RNFL defects were obtained. The optical section images, the reflectivity images, and the topographic images were analysed regarding the visibility of the RNFL defects. The mean surface height and the reflectance at the sites of the RNFL damage were measured and compared with the adjacent apparently normal retina. The width of the RNFL defect at 1 mm distance from the disc border was evaluated.

RESULTS

RNFL defects could be detected in nine of 12 reflectivity images (75%). Single optical section images displayed the RNFL defects in 12 of 12 eyes. The defect width ranged from 0.11 to 1.0 mm. In six of 12 eyes a surface depression (34 (SD 5) microns; range 21-47 microns) was present. The reflectance ratio ranged from 0.68 to 0.94 at the site of the RNFL defect. In eyes with a glaucomatous scotoma in a 6 degrees grid visual field (VF), the defect width was at least 0.25 mm. Surface depression and low reflectance ratio were found irrespective of the presence of a scotoma in the 6 degrees grid VF.

CONCLUSION

The majority of localised RNFL defects can be detected in reflectivity images from laser scanning tomograms. Localised RNFL defects may be differentiated according to surface topography into those with and those without a measurable surface depression. A small but deep RNFL defect is not necessarily associated with a scotoma in routine 6 degrees grid VF static perimetry.

Laser scanning tomography of the optic nerve head in ocular hypertension and glaucoma

BACKGROUND

This study evaluated the ability of laser scanning tomography to distinguish between normal and glaucomatous optic nerve heads, and between glaucomatous subjects with and without field loss.

METHODS

57 subjects were classified into three diagnostic groups: subjects with elevated intraocular pressure, normal optic nerve heads, and normal visual fields (n = 10); subjects with glaucomatous optic neuropathy and normal visual fields (n = 30); and subjects with glaucomatous optic neuropathy and repeatable visual field abnormality (n = 17). Three 10 degrees image series were acquired on each subject using the Heidelberg retina tomograph (HRT). From the 14 HRT stereometric variables, three were selected a priori for evaluation: (1) volume above reference (neuroretinal rim volume), (2) third moment in contour (cup shape), and (3) height variation contour (variation in relative nerve fibre layer height at the disc margin). Data were analysed using analysis of covariance, with age as the covariate.

RESULTS

Volume above reference, third moment in contour, and mean height contour were significantly different between each of the three diagnostic groups (p < 0.001). Height variation contour showed no significant difference among the three diagnostic groups (p = 0.906).

CONCLUSIONS

The HRT variables measuring rim volume, cup shape, and mean nerve fibre layer height distinguished between (1) subjects with elevated intraocular pressures and normal nerve heads, and glaucomatous optic nerve heads, and (2) glaucomatous optic nerve heads with and without repeatable visual field abnormality. This study did not directly assess the ability of the HRT to identify patients at risk of developing glaucoma. It is hypothesised that the greatest potential benefit of laser scanning tomography will be in the documentation of change within an individual over time.

Activated protein C resistance--low incidence in glaucomatous optic disc haemorrhage and central retinal vein occlusion

PURPOSE

Activated protein C (APC) resistance has recently been reported as conferring a sevenfold increase in the risk of venous thrombosis. It is linked to a genetic mutation in the factor V gene which occurs commonly (about 2% to 4% of the community have the mutation). Glaucoma patients with nerve fibre layer (NFL) haemorrhages on the optic disc and patients with central retinal vein occlusion (CRVO) were tested for APC resistance to determine if there was an association.

METHODS

Twenty-three patients with glaucomatous NFL haemorrhages and 23 patients with CRVO were tested. The CRVO cases included 11 with relatively young age of onset (mean 45.1 +/- 6.9 years) without conventional vascular risk factors. Eighty randomly selected Red Cross blood donor samples and 33 staff members were tested as controls. Clotting times with and without exogenous APC were recorded and an APC ratio determined. Cases with APC resistance were tested to confirm that they had the factor V Leiden gene.

RESULTS

No cases of APC resistance were identified in the glaucoma patients and only one of the younger CRVO patients tested positive, but four of 113 controls tested positive. The difference in prevalence between groups is not significant. The mean APC ratios for the three groups were very similar: NFL haemorrhages 5.46(+/- 1.62), CRVO 5.70(+/- 1.56), controls 5.34 ( +/- 1.19) p > 0.5.

CONCLUSION

There was not clear association detected between glaucomatous NFL haemorrhages or CRVO and APC resistance in this sample of patients. This negative finding is important due its known association with venous thrombosis elsewhere in the body.

A new classification of glaucoma including focal glaucoma

This report suggests a new method of classifying glaucoma based upon the appearance of the optic nerve. One subdivision of this classification, focal glaucoma, is discussed in some detail. As is true for all classifications, the system proposed will not be a permanent one. Nor is it intended to be all inclusive. Its purpose is not to replace the system which at present is based on the mechanism for intraocular pressure elevation, i.e., angle-closure glaucoma, open-angle glaucoma, etc., but rather to provide a means by which various subtypes of glaucoma can be better differentiated.

An improved method of densitometry of red-free retinal nerve fibre layer photographs

The red-free negatives of 53 right eyes (30 normal eyes and 23 glaucomatous eyes) and 51 left eyes (32 normal eyes and 19 glaucomatous eyes) were analysed using two different image densitometry techniques. The first technique measured the density from rectangular sample areas, while the second measured density from sector-shaped sample areas which more closely follow the course of the nerve fibres in the retina. Indices which measured the deviation of the data from a clinically determined normal 'gold standard' were calculated, and were used to determine the optimum sensitivity and specificity in separating normal from glaucomatous eyes. There is a significant difference between the data from the normal and glaucomatous groups of eyes, when measured from the sector sample areas. The relative efficacy of this technique is also shown by the improved values of sensitivity (from 42%-70% to 70%-91%), although specificity remained fairly constant (from 66%-83% to 62%-88%).

Laser scanning tomography and stereophotogrammetry in three-dimensional optic disc analysis

Laser scanning tomography (LST) and computed stereophotogrammetry (CSP) are sophisticated diagnostic tools for the three-dimensional analysis of optic nerve head topography. The two methods are based on different physical principles. To compare the information about the shape of the cup of an optic nerve head obtained by LST and CSP, we evaluated the volume profile (VP; i.e., the cross-sectional area of the cup from top to bottom) in 36 discs of 36 patients (20 control group discs C, 16 glaucoma discs G). The Spearman correlation coefficient between the photogrammetric and the laser scanning VP-slope measurements was rs = 0.931; P < 0.001 (rs = 0.935 G, P < 0.001; rs = 0.910 C, P < 0.001). The results suggest that confocal laser scanning provides readings of the shape of the optic disc cup that are similar to the measurements of computed stereophotogrammetry.

Intra- and inter-observer variation of optic nerve head measurements in glaucoma suspects using disc-data

The aim of this study was to determine the intra- and inter-observer variation in the use of a system designed for exact measurements from standard optic nerve head photographs. The commercially available system consisted of a colour CCD Videocamera, a dedicated frame grabber and customized software run on a IBM AT compatible computer. Masked measurements were made 3 times by 2 observers, from stereophotographs of the optic nerve head of 56 eyes from 30 glaucoma suspects. The cup was defined on the basis of contour, not pallor and the disc area was defined as the area inside Elschnig's ring. Intra-observer variances were 0.001 +/- 0.001 mm2 for cup area (mean +/- SD), 0.002 +/- 0.002 mm2 for disc area and 0.002 +/- 0.003 mm2 for rim area. These values for intra-observer variance were comparable with the results obtained using manual planimetric techniques. Intra-observer variance for disc area was significantly larger for the less trained of the two experienced observers. Inter-observer variances were 0.004 +/- 0.009 mm2 for cup area, 0.008 +/- 0.013 mm2 for disc area and 0.009 +/- 0.014 mm2 for rim area. These inter-observer variances were significantly larger than those previously reported for manual planimetry. The absolute differences between the two observers ranged from -0.35 to +0.20 mm2 (-0.08 +/- 0.11 mm2) for cup area, from -0.38 to +0.15 mm2 (-0.08 +/- 0.11 mm2) for disc area and from -0.29 to +0.34 mm2 (-0.06 +/- 0.12 mm2) for rim area.(ABSTRACT TRUNCATED AT 250 WORDS)

Lateral differences indicate future glaucoma

Since eye pairs are anatomically and pathologically asymmetrical, we attempted to determine whether the transition from ocular hypertension to glaucoma might be typified by lateral differences in either intraocular pressure (IOP), papillary excavation, or visual field. Such lateral differences were sought in a retrospective study of the medical records of 47 patients exhibiting ocular hypertension, of whom 25 remained hypertensives and 22 developed glaucoma during the period considered. Although all visual field indices in the latter group had remained within the normal range, the same side consistently yielded significantly worse results in mean sensitivity, and the absolute value for the lateral difference in these individuals was significantly higher than that found for the patients who did not develop glaucoma. Future glaucoma is manifested when the mean sensitivity remains worse in one eye.

Initial glaucomatous optic disk and retinal nerve fiber layer abnormalities and their progression

We attempted to identify the initial glaucomatous changes of the optic disk and retinal nerve fiber layer and to analyze how these changes subsequently progressed. Of 61 eyes of 61 patients with ocular hypertension, 23 (38%) developed glaucoma during ten years of follow-up (range, five to 15 years). The initial sign of glaucomatous damage was diffuse enlargement of the optic disk cup in ten of 23 eyes or generalized thinning of the nerve fiber layer without localized changes in 12 of 23 eyes. We found localized optic disk damage in ten of 23 patients and localized retinal nerve fiber layer damage in 11 of 23 patients alone or in combination with diffuse damage. In 13 of 23 eyes, the cupping ended up in diffuse enlargement with even more profound thinning of the neural rim in the upper and lower temporal disk margins. There seems to be great variability in the appearance and progression of the initial glaucomatous optic disk and nerve fiber layer abnormalities in patients with increased intraocular pressure.

Photogrammetric measurement of nerve fiber layer thickness

To measure retinal nerve fiber layer (NFL) thickness, three sets of simultaneous stereophotographs of the optic disc, taken with the Donaldson fundus camera, were measured at 5 degrees intervals in a stereoplotter (Kern PG2) at the surface of the internal limiting membrane (ILM) and the retinal pigment epithelium (RPE) along the disc margin. The NFL thickness was expressed as a ratio of the vertical disc radius. The reproducibility of the method showed that the percent coefficients of variation (CV%) for 15 normal, 10 ocular hypertensive, and 10 glaucomatous subjects were 5.2%, 6.0%, and 3.9%, respectively. The presence of a halo or scleral crescent had no significant effect on reproducibility. The photogrammetric technique for measuring NFL thickness appears to be highly reproducible and sensitive and may be a valuable quantitative method for: (1) early detection of optic nerve damage from glaucoma and other optic neuropathies and (2) monitoring progression of retinal NFL defects.

Retinal nerve fiber layer photography in glaucoma

Retinal nerve fiber layer (RNFL) photographs can be used for detection of early glaucomatous damage and in the follow-up of patients with established glaucoma. Enlarged black-and-white paper-prints taken with a wide-angle fundus camera as well as stereophotographs of the peripapillary retina have proven quite useful. This article gives a detailed description of both the photographic and the laboratory techniques involved in the process of making good quality RNFL photographs.

Early glaucoma changes in patients with and without an optic disc haemorrhage

Previous reports have shown that retinal nerve fibre layer (RNFL) observation is useful for detection of early glaucoma changes in patients with optic disc haemorrhage. Since disc haemorrhages are not a factor in all glaucoma patients this study was carried out in order to estimate the value of RNFL observation in patients whose first glaucoma damage developed without a haemorrhage. Evaluation of the retrospective data showed that RNFL defects were the first and only detectable glaucoma changes in 46% of haemorrhagic eyes and 26% of non-haemorrhagic eyes. RNFL observation is useful in the follow-up of ocular hypertensive patients for detection of very early glaucoma changes, regardless of whether the changes develop with or without an optic disc haemorrhage.