Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study

Natural History of Optic Disc With Physiologic Large Cup: Incidence, Predictors of Glaucoma Conversion After Minimum 10-Year Follow-up

PURPOSE

To investigate the natural history of optic disc with physiologic large cup (PLC) (ie, vertical cup/disc ratio [VCDR] ≥0.6 without retinal nerve fiber layer defect) and the risk factors for glaucoma conversion.

DESIGN

Observational retrospective cohort study.

METHODS

Subjects who underwent a health screening examination at Seoul National University Hospital Healthcare System Gangnam Center from 2003 to 2010 (n = 76,030) were involved. The prevalence of PLC in the cohort was analyzed. The incidence rate of glaucoma conversion was estimated per 100 person-years among cases with a follow-up period longer than 10 years. Multivariate Cox proportional hazards regression was used to identify ocular and systemic factors associated with glaucoma conversion.

RESULTS

Among 74,617 eligible subjects, 3569 subjects (4.8%) had PLC. Of those with a follow-up period longer than 10 years (n = 859), the incidence rate of glaucoma conversion was 0.95 per 100 person-years. A total of 12.1% of PLC eyes progressed to glaucoma after 8.7 ± 3.9 years (range, 2.0-16.5 years). Higher VCDR (adjusted hazard ratio [aHR] = 4.36; 95% CI = 2.675-7.103), violation of the inferior superior nasal temporal neuroretinal rim thickness rule (aHR = 1.86; 95% CI = 1.057-3.258), presence of retinal arterial sclerosis (aHR = 1.63; 95% CI = 1.040-2.550), and lower total bilirubin level (aHR = 0.58; 95% CI = 0.340-0.991) were associated with glaucoma development.

CONCLUSION

This study identified the prevalence of PLC as well as the incidence rate of glaucoma conversion and the risk factors for glaucoma development in PLC eyes. The natural history of PLC may help clinicians to better understand its risk factors and the specific management needs of their patients.

A neuroglia-based interpretation of glaucomatous neuroretinal rim thinning in the optic nerve head

Neuroretinal rim thinning (NRR) is a characteristic glaucomatous optic disc change. However, the precise mechanism of the rim thinning has not been completely elucidated. This review focuses on the structural role of the glioarchitecture in the formation of the glaucomatous NRR thinning. The NRR is a glia-framed structure, with honeycomb geometry and mechanically reinforced astrocyte processes along the transverse plane. When neural damage selectively involves the neuron and spares the glia, the gross structure of the tissue is preserved. The disorganization and loss of the glioarchitecture are the two hallmarks of optic nerve head (ONH) remodeling in glaucoma that leads to the thinning of NRR tissue upon axonal loss. This is in contrast to most non-glaucomatous optic neuropathies with optic disc pallor where hypertrophy of the glioarchitecture is associated with the seemingly absent optic disc cupping. Arteritic anterior ischemic optic neuropathy is an exception where pan-necrosis of ONH tissue leads to NRR thinning. Milder ischemia indicates selective neuronal loss that spares glia in non-arteritic anterior ischemic optic neuropathy. The biological reason is the heterogeneous glial response determined by the site, type, and severity of the injury. The neuroglial interpretation explains how the cellular changes underlie the clinical findings. Updated understandings on glial responses illustrate the mechanical, microenvironmental, and microglial modulation of activated astrocytes in glaucoma. Findings relevant to the possible mechanism of the astrocyte death in advanced glaucoma are also emerging. Ultimately, a better understanding of glaucomatous glial response may lead to glia-targeting neuroprotection in the future.

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

Aim:

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

Settings and Design:

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

Subjects and Methods:

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

Results:

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

Conclusions:

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

Ageing and ocular surface immunity

Foreword

It gives me pleasure to introduce the 4th edition of the EGS Guidelines. The Third edition proved to be extremely successful, being translated into 7 languages with over 70000 copies being distributed across Europe; it has been downloadable, free, as a pdf file for the past 4 years. As one of the main objectives of the European Glaucoma Society has been to both educate and standardize glaucoma practice within the EU, these guidelines were structured so as to play their part.

Glaucoma is a living specialty, with new ideas on causation, mechanisms and treatments constantly appearing. As a number of years have passed since the publication of the last edition, changes in some if not all of these ideas would be expected.

For this new edition of the guidelines a number of editorial teams were created, each with responsibility for an area within the specialty; updating where necessary, introducing new diagrams and Flowcharts and ensuring that references were up to date. Each team had writers previously involved with the last edition as well as newer and younger members being co-opted.

As soon as specific sections were completed they had further editorial comment to ensure cross referencing and style continuity with other sections.

Overall guidance was the responsibility of Anders Heijl and Carlo Traverso. Tribute must be made to the Task Force whose efforts made the timely publication of the new edition possible.

Roger Hitchings

Chairman of the EGS Foundation

www.eugs.org

The Guidelines Writers and Contributors 

Augusto Azuara Blanco

Luca Bagnasco

Alessandro Bagnis

Keith Barton

Christoph Baudouin

Boel Bengtsson

Alain Bron

Francesca Cordeiro

Barbara Cvenkel

Philippe Denis

Christoph Faschinger

Panayiota Founti

Stefano Gandolfi

David Garway Heath

Francisco Goni

Franz Grehn

Anders Heijl

Roger Hitchings

Gabor Hollo

Tony Hommer

Michele Iester

Jost Jonas

Yves Lachkar

Giorgio Marchini

Frances Meier Gibbons

Stefano Miglior

Marta Misiuk-Hojo

Maria Musolino

Jean Philippe Nordmann

Norbert Pfeiffer

Luis Abegao Pinto

Luca Rossetti

John Salmon

Leo Schmetterer

Riccardo Scotto

Tarek Shaarawy

Ingeborg Stalmans

Gordana Sunaric Megevand

Ernst Tamm

John Thygesen

Fotis Topouzis

Carlo Enrico Traverso

Anja Tuulonen

Ananth Viswanathan

Thierry Zeyen

The Guidelines Task Force 

Luca Bagnasco

Anders Heijl

Carlo Enrico Traverso

Augusto Azuara Blanco

Alessandro Bagnis

David Garway Heath

Michele Iester

Yves Lachkar

Ingeborg Stalmans

Gordana Sunaric Mégevand

Fotis Topouzis

Anja Tuulonen

Ananth Viswanathan

The EGS Executive Committee 

Carlo Enrico Traverso (President)

Anja Tuulonen (Vice President)

Roger Hitchings (Past President)

Anton Hommer (Treasurer)

Barbara Cvenkel

Julian Garcia Feijoo

David Garway Heath

Norbert Pfeiffer

Ingeborg Stalmans

The Board of the European Glaucoma Society Foundation 

Roger Hitchings (Chair)

Carlo E. Traverso (Vice Chair)

Franz Grehn

Anders Heijl

John Thygesen

Fotis Topouzis

Thierry Zeyen

The EGS Committees 

CME and Certification 

Gordana Sunaric Mégevand (Chair)

Carlo Enrico Traverso (Co-chair)

Delivery of Care 

Anton Hommer (Chair)

EU Action 

Thierry Zeyen (Chair)

Carlo E. Traverso (Co-chair)

Education 

John Thygesen (Chair)

Fotis Topouzis (Co-chair)

Glaucogene 

Ananth Viswanathan (Chair)

Fotis Topouzis (Co-chair)

Industry Liaison 

Roger Hitchings (Chair)

Information Technology 

Ingeborg Stalmans (Chair)

Carlo E. Traverso (Co-chair)

National Society Liaison 

Anders Heijl (Chair)

Program Planning 

Fotis Topouzis (Chair)

Ingeborg Stalmans (Co-chair)

Quality and Outcomes 

Anja Tuulonen (Chair)

Augusto Azuara Blanco (Co-chair)

Scientific 

Franz Grehn (Chair)

David Garway Heath (Co-chair)

Ethnic variation in optic disc size by fundus photography

PURPOSE

To compare optic disc size among Caucasian, Chinese, African, Filipino and Hispanic subjects recruited from a university-based general ophthalmology clinic.

METHODS

In this retrospective cross-sectional study, optic disc size was calculated from fundus photographs. Differences in age, sex and spherical equivalent among the ethnic groups were examined with either Kruskal--Wallis test or Chi-square test. Ethnic differences in optic disc size were evaluated with linear mixed-effects regression models that adjusted for age, sex, spherical equivalent, glaucoma status, lens status and use of both eyes in the same subject.

RESULTS

Five hundred and seventy-four eyes of 305 subjects were analyzed. The mean and standard deviation of the optic disc size were 2.16 ± 0.41 mm(2) for Caucasian, 2.30 ± 0.56 mm(2) for Chinese, 2.31 ± 0.41 mm(2) for Filipino, 2.38 ± 0.40 mm(2) for African and 2.40 ± 0.38 mm(2) for Hispanic subjects. Age and spherical equivalent differed among the ethnic groups by Kruskal--Wallis test (p < 0.05). Sex differed among the ethnic groups by Chi-square test (p < 0.05). Ethnic differences in optic disc size were not observed among African, Hispanic, Filipino and Chinese subjects in linear mixed-effects regression analyses (p > 0.05). However, Caucasian differed from the other ethnicities in linear mixed-effects regression analyses (p < 0.05).

CONCLUSIONS

Optic disc size was significantly smaller in Caucasian compared to the other ethnic groups. Optic disc size differences among non-Caucasian ethnic groups were not significant.

Biometry and spectral domain optical coherence tomography parameters in children with large cupping

PURPOSE

The purpose of this study is to investigate optic nerve head using spectral domain optical coherence tomography (SD-OCT) in children with large cupping.

METHODS

111 eyes (4-10 years) were divided into three groups according to the cup to disc ratio: group 1, ≤0.3; group 2, 0.4-0.6; and group 3, ≥0.7. The rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were investigated using SD-OCT (Cirrus HD-OCT, Carl Zeiss, Jena, Germany), and the axial length and anterior chamber depth (ACD) were measured by IOL master (IOL master 500, Carl Zeiss, Jena, Germany). Next, we compared ocular biometry and SD-OCT between the three groups.

RESULTS

The mean age of group 1 was 6.48 ± 1.42 years, 7.00 ± 1.75 years in group 2, and 6.63 ± 1.82 years in group 3 (p = 0.370). A significant difference was seen in the spherical equivalent between the groups (p = 0.001). Group 2 had the most myopic refractive errors. As the cup to disc ratio increases, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume increase significantly. When the results of ocular biometry and SD-OCT are adjusted for axial length, only disc area showed a significant correlation with cup to disc ratio (ACD: p = 0.473, rim area: p = 0.639, disc area: p = 0.005, and cup volume: p = 0.325).

CONCLUSION

Axial length is the key factor determining disc size, which in turn is important for determining cup to disc ratio. Normal children with large cupping should be examined for axial length, myopic refractive errors, and disc size.

Effect of optic disc size and disease severity on the diagnostic capability of glaucoma imaging technologies in an Indian population

PURPOSE

To evaluate the influence of optic disc size and disease severity on the diagnostic validity of optical coherence tomography (Stratus OCT), scanning laser polarimetry [GDx variable corneal compensator (VCC)], and confocal scanning laser ophthalmoscopy [Heidelberg retina tomograph II (HRT II)] in Indian eyes with glaucoma.

METHODS

Ninety-five normal and 125 glaucoma patients underwent imaging with Stratus OCT, GDx VCC, and HRT II. One eye of each person was randomly selected for analysis. Using disc area determined on HRT II, discs were classified as small (<2 mm), moderate (2 to 3 mm), and large (>3 mm). The parameter with the best sensitivity for each device, at a fixed specificity, was compared for different disc sizes. Logistic marginal regression was used to study the effect of disc size and disease severity (mean deviation on standard automated perimetry) on the diagnostic performance of these imaging devices.

RESULTS

At a fixed specificity of 84.2%, the sensitivity of HRT II was significantly different for varying disc sizes (P=0.0004). The sensitivities for dissimilar disc sizes were not significantly different for the GDx VCC (P=0.928) or Stratus OCT (P=0.381). Logistic marginal regression also showed that sensitivity of HRT II increased with increasing disc size, whereas sensitivity of OCT and GDx were independent of the disc size. The sensitivity of all 3 technologies increased with increasing disease severity (decreasing mean deviation).

CONCLUSIONS

Optic disc size affects the diagnostic capability of HRT II but not that of GDx VCC or Stratus OCT. The sensitivity of all 3 imaging technologies increased with increasing disease severity.

Glaucoma risk assessment using a non-linear multivariable regression method

The present research investigates the relationship between the central corneal thickness (CCT), Heidelberg Retina Tomograph II (HRTII) structural measurements and intraocular pressure (IOP) using an innovative non-linear multivariable regression method in order to define the risk factors in future glaucoma development and patient management. The method is implemented to data from ninety-three open angle glaucoma eyes. The results show that in established glaucoma, CCT is significantly associated with HRTII structural measurements (maximum contour depression, cup volume inferotemporally) and IOP. They are also compared to those obtained from the application of standard linear regression methods, improving the coefficient determination R(2) by 35%, exhibiting thus the performance of the proposed methodology.

Morphologic assessment for glaucoma in the Multicenter Uveitis Steroid Treatment (MUST) trial

PURPOSE

To compare Reading Center (RC) cup-to-disc ratio (CDR) assessment from stereoscopic photographs with clinician estimation in a uveitis clinical trial.

METHODS

Clinical estimation of CDR was performed by ophthalmologists via dilated biomicroscopy. Photographic evaluation was performed at an independent RC by masked, certified evaluators. Quality control was performed by repeat grading of 77 randomly selected images.

RESULTS

Among 479 eyes with uveitis, 353 eyes had clinical and photographic grades for CDR. Agreement between clinical and RC grading was fair, with exact agreement of 29%. Agreement within 0.1 and 0.2 CDR was 70 and 93%, respectively (weighted κ = .34). Intergrader reproducibility at the RC was better (weighted κ = .59, ICC 0.74).

CONCLUSION

Morphologic assessment of cup to disc ratio is an important outcome and safety measure for determining glaucomatous damage in clinical trials. Masked RC measurements are more likely to be accurate than biomicroscopic grading in identifying meaningful anatomical change associated with glaucoma.

Diagnostic accuracy of the Heidelberg Retina Tomograph for glaucoma a population-based assessment

OBJECTIVE

To evaluate the Heidelberg Retina Tomograph II (HRTII; Heidelberg Engineering, Heidelberg, Germany) as a screening tool for open-angle glaucoma (OAG) in an older population.

DESIGN

Population-based, cross-sectional study.

PARTICIPANTS

Participants from the 10-year follow-up Blue Mountains Eye Study (n = 1952; 75.6% of survivors).

METHODS

Participants underwent optic nerve head imaging performed using the HRTII; OAG was diagnosed independently from optic disc photographs and Humphrey 24-2 visual fields.

MAIN OUTCOME MEASURES

The Moorfields Regression Analysis (MRA) was applied to scans using the default results of "normal," borderline," and "outside normal limits." Outcome classification was at the person level and used data from both eyes.

RESULTS

Mean age was 73.7 years. The HRT scans could be acquired in 1644 participants, 95.9% of those fully examined; 87.4% of scans having a topography standard deviation (TSD) < or =40 microm. Larger TSD was associated with older age and OAG. The MRA sensitivity was 64.1%, specificity 85.7%, positive predictive value 21%, and negative predictive value 97.6% for detecting OAG. Including borderline results improved sensitivity (87.0%) but specificity dropped to 70.6%. Significant predictors of abnormal MRA included OAG (odds ratio [OR], 7.70; 95% confidence interval [CI] 4.79-12.35), age (OR, 1.05; 95% CI, 1.03-1.07), TSD (OR, 1.01; 95% CI, 1.003-1.020) and disc size (OR, 3.2; 95% CI, 2.31-4.49). Diagnostic accuracy was improved by restricting TSD <40 microm. Further TSD restriction improved specificity at the expense of sensitivity. As disc size increased, specificity fell whereas sensitivity, OAG prevalence, and the proportion testing positive rose. Glaucoma prevalence, positive predictive value, and the proportion testing positive increased, but specificity fell with increasing age. Sensitivity also fell between youngest and oldest groups. Diagnostic performance improved for visual field mean deviation < -4.0 dB. Single eye analyses overestimated specificity and underestimated sensitivity compared with using data from both eyes.

CONCLUSIONS

Diagnostic test evaluation studies of HRTII using single eye analyses or restrictive selection overestimate test accuracy compared with this population-based study. Although the specificity of the MRA was inadequate for use as a glaucoma screening test, the HRTII performed relatively well in an unselected older population with acceptable quality scans in most eyes.

Optic disk size variability between African, Asian, white, Hispanic, and Filipino Americans using Heidelberg retinal tomography

PURPOSE

To compare the optic disk size of African, Asian, white, Hispanic, and Filipino-American patients in a multiethnic glaucoma practice.

PATIENTS AND METHODS

Five hundred seventy-six eyes of 319 patients who had consecutively received Heidelberg retinal tomography 2 (HRT) from February 2006 to October 2007 in a glaucoma clinic that met inclusion criteria were included. The 5 ethnic groups represented were white (n=215, 37.3%), Asian (non-Filipino) (n=178, 30.8%), African (n=67, 11.6%), Hispanic (n=66, 11.4%), and Filipino-Americans (n=50, 8.7%). The relationship of optic disk size (global disk area) with race, age, sex, diagnosis, central corneal thickness (CCT), spherical equivalent refraction (SE), and cylindrical refraction was evaluated using multivariate regression analysis adjusting for confounders.

RESULTS

Mean optic disk size of white-Americans (2.15 mm) was significantly smaller than that of African (2.55 mm), Asian (2.38 mm), Filipino (2.48 mm), and Hispanic-Americans (2.57 mm) (all, P < or = 0.0007). Global disk area was not statistically different between all other races (all, P > or = 0.054). Global disk area increased with SE (P=0.013), but was not found to vary with age, sex, diagnosis, CCT, or cylindrical refraction (all, P > or = 0.08).

CONCLUSIONS

In our glaucoma clinic-based population, white-Americans had smaller optic disks than all other races, and there were no optic disk size differences among the other races studied. Optic disk size had no significant relationship to age, sex, CCT, cylindrical refraction or diagnosis, and a small direct relationship to SE. Confirmation of these results in a population-based study is needed.

Clinical measurement and categorization of optic disc in glaucoma patients

BACKGROUND

Assessment of optic disc size is an important component of optic nerve head examination. Agreement between different methods of disc size measurements is not very good.

PURPOSE

To assess the agreement between the disc size assessed by Heidelberg retina tomograph (HRT) and stereobiomicroscopy with a 90 diopter (D) lens. To report the clinical (measured by biomicroscopy) disc diameters of small, average and large optic discs categorized by HRT disc areas.

SETTING AND DESIGN

Observational study of subjects examined in the glaucoma clinic of a tertiary eye institute.

MATERIALS AND METHODS

Seventy-five eyes of 75 glaucoma subjects were studied. Disc diameter was measured using stereobiomicroscopy and HRT. The agreement between the two sets of measurements was assessed by intraclass correlation coefficient (ICC). Discs were classified into small (<1.6 mm(2)), average (1.6-2.6 mm(2)) and large (>2.6 mm(2)) depending on cutoffs provided by the manufacturers of HRT. The means (95% CI) of the corresponding vertical disc diameter in these groups were assessed.

STATISTICAL ANALYSIS

ICC, Bland and Altman plots.

RESULTS

ICC for measurements of clinical and HRT horizontal disc diameter was 0.518 and for vertical disc diameter measurement was 0.487. The mean difference between the clinical and HRT measurements as analyzed by the Bland and Altman plot was 0.17 (95% CI, 0.13- 0.47) for horizontal and 0.22 (95% CI, 0.11- 0.54) for vertical disc diameter. Of the 75 eyes, 3 eyes had small discs, 54 average and 18 large discs. The mean clinical vertical disc diameter for small discs was 1.55 mm (95% CI, 1.2-1.7), for average discs was 1.91 mm (95% CI, 1.87-1.96) and for large discs was 2.15 mm (95% CI, 2.03-2.27).

CONCLUSION

The agreement between clinical and HRT disc diameter measurements is moderate. Disc diameter measurement on stereobiomicroscopy can be used to categorize discs into small, average and large discs.

New findings in the evaluation of the optic disc in glaucoma diagnosis

PURPOSE OF REVIEW

Ophthalmoscopical evaluation of the optic disc is a feasible and largely accessible method to diagnose glaucoma. Many qualitative parameters have been described in glaucomatous optic neuropathy. Considering individual variations in the details of topography or tissue components damaged by the glaucomatous process, however, adequate identification of glaucomatous optic disc signs requires training and experience. Without adequate guidelines of optic disc examination, the physician may miss important aspects that could lead to adequate diagnosis or identification of progression in a patient with established glaucoma. This paper presents a systematic approach for the examination of the optic disc and retinal nerve fiber layer to aid the detection of glaucoma.

RECENT FINDINGS

Optic disc qualitative parameters are better than quantitative parameters in separating glaucomatous from normal eyes. The sequential evaluation of optic disc size, neuroretinal rim size and shape, retinal nerve fiber layer, presence of peripapillary atrophy, and presence of retinal or optic disc hemorrhages enhances the ability to detect glaucomatous damage and its progression.

SUMMARY

Ophthalmologists should be familiar with glaucomatous optic disc signs that can be identified during clinical examination. A simple systematic approach may allow improved diagnosis and management of glaucoma.

Optic disk size and glaucoma

Assessment of optic disk size is an important, but often overlooked, component of the diagnostic evaluation for glaucoma. Measured values of optic disk size vary with the measurement technique utilized. Available methods for disk size measurement and their respective strengths and limitations will be discussed. Further, actual disk size varies with race and possibly other demographic characteristics. Disk size is also associated with variation of specific anatomical structures of the optic nerve head and the retinal nerve fiber layer. These disk size- dependent variations may influence the susceptibility to glaucoma or the likelihood of glaucoma diagnosis. This manuscript reviews the published evidence relating to disk size and glaucoma.

Optic nerve head parameters of an indigenous population living within Central Australia

PURPOSE

Clinical examination of the optic disc is an essential element in the assessment of its health. Previous work has described normal optic disc appearance among different races. No such description of optic discs exists for indigenous Australians, who are at low risk of developing glaucoma. This study was designed to evaluate optic disc parameters of indigenous Australians.

METHODS

A sample of 208 indigenous Australians were recruited as they presented to remote clinics in Central Australia. Each subject underwent optic disc photography using a Topcon TRC-NW100 digital fundus camera. Optic discs were measured and analysed with Topcon ImageNet 2000 software.

RESULTS

Among other parameters, mean vertical disc diameter and disc area were 2.13 +/- 0.21 mm (mean +/- SD) and 3.13 +/- 0.57 mm2, respectively, for right eyes and 2.14 +/- 0.21 mm and 3.16 +/- 0.58 mm2 for left eyes. When compared with published studies, these parameters were significantly larger than Caucasians, but similar to African individuals.

CONCLUSION

Our results suggest that indigenous Australians have optic discs that are larger than those of Caucasians, but similar to those of Africans who are considered to at a greater risk of glaucoma. Factors other than optic disc area are likely to underlie the higher prevalence of primary open angle glaucoma among African individuals.

Five rules to evaluate the optic disc and retinal nerve fiber layer for glaucoma

A systematic approach for the examination of the optic disc and retinal nerve fiber layer is described that will aid in the detection of glaucoma. This approach encompasses 5 rules: evaluation of optic disc size, neuroretinal rim size and shape, retinal nerve fiber layer, presence of parapapillary atrophy, and presence of retinal or optic disc hemorrhages. A systematic process enhances the ability to detect glaucomatous damage as well as the detection of progression, and facilitates appropriate management.

Relationship between corneal thickness and optic disc damage in glaucoma

BACKGROUND

Central corneal thickness (CCT) has been found to be a powerful predictor for the development of glaucoma in patients with ocular hypertension. This study aimed to determine whether CCT was also related to glaucoma severity.

METHODS

The vertical cup/disc ratio (VCDR) was used as a single objective measure of glaucoma severity. Vertical cup diameters and vertical disc diameters were measured using a graticule attached to a 60 D Volk lens, in consecutive patients presenting to a single ophthalmologist. Measurements were corrected for magnification. The difference between corrected VCDR and 95% probability of VCDR normality was compared to CCT, which was measured with an ultrasonic pachymeter.

RESULTS

During the study period 554 eyes from 281 patients with glaucoma were reviewed. The mean CCT was 519.0 microm, with the mean corrected VCDR being 0.71. A univariate linear regression model revealed that an increase of 10 microm in CCT resulted in a 0.009 decrease in the difference between true VCDR and the predicted normal VCDR. The R2 value for the regression was 0.04 (P < 0.0001).

CONCLUSION

There is a highly statistically significant, albeit small, negative correlation between corneal thickness and glaucoma severity. This study supports the notion that CCT should be measured in the assessment of patients with glaucoma. Progressive thinning or presence of a thin cornea may have pathogenic or prognostic roles in some types of glaucoma.

Retinal vessel diameter and open-angle glaucoma: the Blue Mountains Eye Study

PURPOSE

To examine the relationship between open-angle glaucoma (OAG) and retinal vessel diameter among baseline participants in the Blue Mountains Eye Study.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

The study included 3654 persons older than 49 years, representing 82.4% of permanent residents living in an area west of Sydney.

METHODS

Participants had a detailed eye examination, including automated perimetry and stereo optic disc photography. A computer-assisted program measured retinal vessel diameters from digitized photographs of right eyes.

MAIN OUTCOME MEASURES

Open-angle glaucoma was diagnosed from matching visual field defects and optic disc cupping, without reference to intraocular pressure (IOP) level. Ocular hypertension was defined as IOP of >21 mmHg in either eye, without matching glaucomatous optic disc and field changes. Average retinal vessel diameters, measured from right eyes, were summarized as arteriolar and venular equivalents. The lowest quintile of the arteriolar equivalent or arteriole-to-venule ratio was used to define generalized retinal arteriolar narrowing.

RESULTS

The study included 3314 participants, after excluding those with incomplete data or nonglaucomatous optic nerve disease. Of persons included, 59 (1.8%) had evidence of glaucomatous damage affecting the right eye, 3065 (92.5%) had no damage to either eye, and 163 (4.9%) had ocular hypertension. Right eyes with glaucomatous damage had significantly narrower retinal arteriolar diameters (183+/-2.6 microm) than eyes without glaucoma (194+/-0.4 microm, P = 0.0001) or eyes with ocular hypertension (195+/-1.6 microm, P = 0.0002), after adjusting for age, mean arterial blood pressure, and other confounding variables, including refraction. Right eyes with glaucomatous damage were at least 2 times more likely to have generalized retinal arteriolar narrowing than eyes without glaucoma (odds ratio, 2.7; 95% confidence interval, 1.5-4.8).

CONCLUSIONS

These population-based data suggest that generalized retinal arteriolar narrowing, an indicator of localized vascular change, is significantly associated with optic nerve damage caused by OAG. It is not clear whether such a retinal arteriolar change reflects an ischemic process leading to optic nerve damage or results from loss of retinal neurons secondary to glaucoma.

Visibility of lamina cribrosa pores and open-angle glaucoma

PURPOSE

To determine prevalence and associations of visible lamina cribrosa pores in an older population and assess whether this feature is associated with open-angle glaucoma (OAG).

DESIGN

Case-control study nested within a large, population-based cross-sectional study.

METHODS

The Blue Mountains Eye Study examined 3654 persons (82.4% of permanent residents of a defined area) aged over 48 years. Stereo optic disk photographs were taken and graded reliably in a masked fashion.

RESULTS

Lamina pore visibility was associated with larger vertical cup-disk ratio and optic disk diameter, hyperopic refraction, and male gender. Pores were slightly less visible with increasing age. They were visible in 70.8% of subjects with open-angle glaucoma but in only 29.3% of normals. This strong association disappeared after adjusting for other variables.

CONCLUSION

Lamina cribrosa pores are commonly visible in glaucoma subjects and less commonly in normals. This association, however, is almost entirely because of an increased visibility associated with larger vertical cup-disk ratio and optic disk size.

The effect of optic disc diameter on vertical cup to disc ratio percentiles in a population based cohort: the Blue Mountains Eye Study

OBJECTIVE

The 97.5th percentile for vertical cup to disc ratio (VCDR) has been proposed as a useful tool to assist in the diagnosis of glaucoma in population studies. Previous reports of VCDR percentiles have either not been adjusted for disc size or have been calculated by regression analysis from small hospital based cohorts. The authors' aim was to generate VCDR percentiles in a large, population based sample.

METHODS

Data were collected from 3654 individuals, aged 49 years or older, living in the Blue Mountains, west of Sydney. Vertical disc diameter and VCDR were determined by planimetry from stereo optic disc photographs. The distribution of VCDR and percentiles (95th, 97.5th, 99th) were calculated.

RESULTS

6678 eyes were included in the analysis. Median cup to disc ratio, 95th, 97.5th, and 99th percentile increased with vertical optic disc diameter in a linear fashion. An increase of 0.2 in median VCDR (0.35 to 0.55) was observed between small (1.1-1.3 mm) and large (1.8-2.0 mm) optic discs. An equivalent increase of 0.2 (0.59 to 0.74) was observed for the 97.5th percentile from small to large discs.

CONCLUSION

VCDR percentiles for a "normal" population, adjusted for vertical optic disc diameter are presented. One quarter of all discs fell within the small or large disc categories highlighting the importance for estimating optic disc size. These data may assist in the diagnosis of glaucoma in clinical practice as well as providing a normative database. Sole use of VCDR percentile cut offs in defining glaucoma cases in population surveys requires further validation.

Relationship of optic disk topography and visual function in patients with large cup-to-disk ratios

PURPOSE

To determine if topographic differences exist between large cup-to-disk ratio (C/D) eyes with standard achromatic automated perimetry (SAP) abnormalities and those with only short-wavelength automated perimetry (SWAP) abnormalities.

DESIGN

Cross-sectional study.

METHODS

The setting was a referral university-based clinical practice. We selected one eye of 72 patients with a vertical C/D of at least 0.8 by ophthalmoscopy. Patients performed SWAP, SAP, and confocal scanning laser ophthalmoscopy. We compared optic disk topography in eyes with and without visual field abnormalities and controlled for the influence of disk area.

RESULTS

Disk area was a confounder of many topographic measures. After controlling for disk area, eyes with abnormal SAP had differences in rim volume, cup shape, rim area, retinal nerve fiber layer thickness, and retinal nerve fiber layer cross-sectional area when compared with eyes with normal SAP (P <.05). Rim volume and rim area were different in the SWAP comparison (P <.05).

CONCLUSIONS

Investigators should control for disk area when evaluating topographic measures by confocal scanning laser ophthalmoscopy. In eyes with a large C/D, optic disk topography is more glaucomatous in eyes with SAP abnormalities than in those with only SWAP abnormalities. Eyes with large C/D and only SWAP abnormalities may have fewer glaucomatous optic disk changes than such eyes with SAP abnormalities. This indicates that SWAP is likely to correspond to abnormalities in optic disk topography at an earlier stage of glaucomatous optic neuropathy than SAP. Therefore, clinicians should consider SWAP testing in glaucoma suspects to detect glaucomatous visual field loss at an earlier stage of structural loss.

Patterns of glaucomatous visual field defects in an older population: the Blue Mountains Eye Study

This report aims to describe the frequency of different patterns of visual field loss in open-angle glaucoma (OAG). The Blue Mountains Eye Study examined 3654 persons (aged 49+) during 1992-1994. Humphrey supra-threshold visual fields were performed in 88.9%. Those classified as glaucoma suspects had 30-2 full-threshold fields (9.2%). Of OAG cases (n = 108) with field tests in both eyes (n = 97), unilateral defects were present in 49 (50.5%) and bilateral in 48 (49.5%). Advanced field loss was found in 16 (15.4%) subjects and in 22 (10.9%) eyes, with bilateral loss present in 6 (6.2%) cases. Of all eyes of OAG cases (n = 201), 49 (24.4%) had no defects, 52 (25.9%) upper, 61 (30.3%) lower, and 17 (8.5%) had combined upper and lower loss. Of the upper and lower cases (n = 113), the types of defects included nasal step (36), arcuate (26), nasal plus arcuate (26), and hemispherical defects (25). Of subjects with fields in at least one eye (n = 104), there was a similar proportion in the worse eye of upper defects (28.8%), lower (31.7%), and combined upper and lower (24.0%). Undiagnosed OAG was more frequent in unilateral (65.3%) than bilateral (34.7%) cases (P = 0.003). This study reports the pattern of typical glaucomatous field loss in an older Australian population.

Observer experience and Cup:Disc ratio assessment

BACKGROUND

The validity of the Cup:Disc (C:D) ratio as a clinical measure depends on the level of agreement among observers. In this study, we investigated the effect of observer experience on interobserver and intraobserver agreement in C:D ratio estimation.

METHODS

Nine 3rd-year (Yr3) and nine 4th-year (Yr4) optometry students and nine optometrists (Opt), determined C:D ratios from 26 optic disc photographs viewed monoscopically and stereoscopically. Observer agreement was investigated using weighted kappa (Kw) analysis.

RESULTS

Interobserver agreement was higher (p < 0.01) among optometrists than among 4th-year students and higher (p < 0.01) among 4th-year than among 3rd-year students (mean Kw: Opt = 0.61; Yr4 = 0.51; Yr3 = 0.39). Stereoscopic estimates of C:D ratios were higher (p < 0.0001) than monoscopic estimates, and interobserver agreement was higher (p < 0.001) when evaluating the vertical rather than the horizontal C:D ratio. Intraobserver agreement (mean Kw: Opt = 0.67; Yr4 = 0.66; Yr3 = 0.62) did not vary significantly (p = 0.78) with experience.

CONCLUSIONS

The extent to which an observer reproducibly assesses the C:D ratio from optic disc photographs (intraobserver agreement) does not increase with experience. However, the agreement between different observers in assessing the C:D ratio (interobserver agreement) increases with experience.

Relationship between visual field testing and scanning laser polarimetry in patients with a large cup-to-disk ratio

PURPOSE

To determine the relationship between quantitative nerve fiber layer measurements and visual field testing in patients with large cup-to-disk ratios.

METHODS

Seventy-six patients with vertical cup-to-disk ratios by contour of at least 0.8 on stereoscopic photographs and 50 normal subjects were included. One eye was randomly selected for study. All patients underwent standard achromatic automated perimetry, short-wavelength automated perimetry, and retinal nerve fiber layer measurements with scanning laser polarimetry. Analysis of variance was used to evaluate differences between the subject groups. Significance of pairwise comparisons was determined using the Tukey-Kramer multiple comparison test.

RESULTS

Statistically significant differences in nerve fiber layer measurements between patients with large cup-to-disk ratios and both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry (n = 22) and patients with large cup-to-disk ratios and both normal standard achromatic automated perimetry and short-wavelength automated perimetry (n = 42) were found for superior nasal ratio, maximum modulation, ellipse modulation, and the linear discriminant function (Tukey-Kramer less than.05). There was no significant difference in patients with abnormal short-wavelength automated perimetry only (n = 9) as compared with patients with both normal standard achromatic automated perimetry and short-wavelength automated perimetry and patients with both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry. Statistically significant differences between the normal subjects and patients with large cup-to-disk ratios and both abnormal standard achromatic automated perimetry and short-wavelength automated perimetry were found for all retinal nerve fiber layer parameters, with the exception of symmetry, superior ratio, and inferior ratio.

CONCLUSION

Our results show considerable overlap in nerve fiber layer measurements in eyes with large cup-to-disk ratio and abnormal visual fields as compared with eyes with large cup-to-disk ratios and normal visual fields. This may limit the clinical usefulness of scanning laser polarimetry for detection of early glaucoma in patients with large cup-to-disk ratios. Longitudinal studies are needed to determine if patients with large cup-to-disk ratios with normal standard achromatic automated perimetry and abnormal short-wavelength automated perimetry subsequently develop standard achromatic automated perimetry defects and if scanning laser polarimetry can concurrently detect progression of nerve fiber layer damage.

The normal optic nerve head

BACKGROUND

The normal optic nerve head varies from one person to another, and there is often intraindividual variation as well. Factors such as race and age play an important role in distinguishing what may be considered normal variations in optic nerve head appearance.

METHODS

A literature search and review of the latest studies on the optic nerve head was conducted.

RESULTS

Results of recent studies showed that variations in the average cup-to-disc ratio exist for different races, and with age there is a gradual loss of nerve fibers leading to an overall increase in the cup-to-disc ratio. There is also evidence that congenitally larger optic nerves have larger cup-to-disc ratios and more nerve fibers. Smaller optic nerves, in contrast, have smaller cup-to-disc ratios and fewer nerve fibers. These findings are presented along with sample photographs depicting the normal variations in optic nerve head appearance.

CONCLUSION

Over the past 30 years, technology has allowed for changing views about what may be considered normal in reference to the optic nerve head. This information is valuable to the eye care practitioner in helping to make appropriate patient care management decisions.

Vertical cup/disc ratio in relation to optic disc size: its value in the assessment of the glaucoma suspect

AIMS

The vertical cup/disc ratio (CDR) has long been used in the assessment of the glaucoma suspect, though the wide range of CDR values in the normal population limits its use. Cup size is related physiologically to disc size and pathologically to glaucomatous damage. Disc size can be measured at the slit lamp as the vertical disc diameter (DD). The ability of the CDR, in relation to DD, to identify glaucomatous optic discs was investigated.

METHODS

88 normal, 53 early glaucoma, and 59 ocular hypertensive subjects underwent stereoscopic optic disc photography and clinical biometry. Photographs were analysed in a masked fashion by computer assisted planimetry. The relation between vertical cup diameter and DD was explored by linear regression, and expressed in terms of CDR. The upper limit of normal was defined by the 95% prediction intervals of this regression (method 1) and by the upper 97.5 percentile for CDR (method 2). The sensitivity and specificity of CDR to identify an optic disc as glaucomatous was tested with these disc size dependent and disc size independent cut offs in small, medium, and large discs.

RESULTS

The CDR was related to DD by the equation CDR = (-1.31 + (1.194 x DD))/DD. The sensitivity in small, medium, and large discs was 80%, 60%, and 38% respectively for method 1 and 33%, 67%, and 63% respectively for method 2. Specificity was 98.9% (method 1) and 97.7% (method 2).

CONCLUSIONS

The CDR, relative to disc size, is useful clinically, especially to assist in identifying small glaucomatous discs.

Optic disc hemorrhages in a population with and without signs of glaucoma

OBJECTIVE

This study aimed to determine the prevalence and associations of optic disc hemorrhage in a well-defined older Australian population.

DESIGN

The study design was a population-based, cross-sectional study.

PARTICIPANTS

A total of 3654 persons 49 years of age or older, representing 88% of permanent residents from an area west of Sydney, participated in the study.

MAIN OUTCOME MEASURES

Participants underwent a detailed eye examination. The diagnosis of optic disc hemorrhage was made from masked photographic grading; disc hemorrhages were subclassified as flame or blot in shape. Open-angle glaucoma was diagnosed from matching visual field loss and optic disc rim thinning.

RESULTS

The overall prevalence of disc hemorrhage in either or both eyes was 1.4%. Disc hemorrhage prevalence was higher in women (odds radios [OR], 1.9; confidence interval [CI], 1.0-3.5) and increased with age (OR, 2.2 per decade; CI, 1.7-2.8 per decade). The overall prevalence in subjects with open-angle glaucoma was 13.8% (8% in high-pressure glaucoma and 25% in low-pressure glaucoma) and 1.5% in subjects with ocular hypertension. Disc hemorrhages were associated with increasing intraocular pressure (OR, 1.7 per 5 mmHg; CI, 1.3-2.3 per 5 mmHg), pseudoexfoliation (OR, 3.5; CI, 1.1-11.8), diabetes (OR, 2.9; CI, 1.4-6.3), and increasing systolic blood pressure (OR, 1.1 per 10 mmHg; CI, 1.0-1.3) after adjusting for age and gender. Among subjects without open-angle glaucoma, disc hemorrhages were more frequent in eyes with larger vertical cup-disc ratios and in subjects with a history of typical migraine headache (OR, 2.2; CI, 1.1-4.6). No associations were found among subjects with a history of vascular events, smoking, regular aspirin use, or myopia.

CONCLUSIONS

Disc hemorrhage prevalence in this population is higher than that in the two previous population-based reports. Although the strong association of disc hemorrhage with open-angle glaucoma was confirmed (particularly low-pressure glaucoma), most disc hemorrhages (70%) were found in participants without definite signs of glaucoma.