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 mm²), average (1.6-2.6 mm²) and large (>2.6 mm²) 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.     

Retinal tomographic measurements in optic disc pit

Background: The aim was to assess the Heidelberg Retina Tomograph II measurements in optic disc pit. Methods: The study included 10 patients with a unilateral optic disc pit. The patients had no other ocular conditions except refractive errors. Normal fellow eyes of the patients were used as a control group. Optic nerve head topographic analyses were performed using a confocal scanning laser ophthalmoscope, Heidelberg Retina Tomograph II (HRT II). Results: The topographic parameters of the eyes with optic disc pit and normal fellow eyes were as follows, respectively: disc area (3.77 ± 1.50 and 3.07 ± 0.83 mm²), cup area (1.99 ± 1.71 and 1.09 ± 0.54 mm²), rim area (1.67 ± 0.55 and 1.87 ± 0.75 mm²), cup volume (0.94 ± 1.24 and 0.34 ± 0.27 mm³), rim volume (0.51 ± 0.40 and 0.55 ± 0.19 mm³), mean cup depth (0.44 ± 0.20 and 0.31 ± 0.11 mm) and mean retinal nerve fibre layer thickness (0.25 ± 0.20 and 0.28 ± 0.59 mm). Eyes with an optic disc pit were found to have significantly larger disc area compared to fellow eyes (p = 0.038). All the other parameters showed no statistically significant interocular differences (p > 0.05). Conclusion: Our study demonstrates that the optic disc pit affects only the disc area measurement in HRT II. Other changes in optic nerve head morphometric parameters were insignificant. The clinician must be careful in the evaluation of HRT II results with respect to optic disc area in a disc with a pit.     

Glaucoma diagnosis optic disc analysis comparing Cirrus spectral domain optical coherence tomography and Heidelberg retina tomograph II

Purpose

To evaluate the diagnostic ability of optic nerve head parameters, measured by Cirrus spectral domain optical coherence tomography (SD OCT) and Heidelberg retina tomograph II (HRT II) to detect concomitant glaucoma.

Methods

Cirrus OCT and HRT examinations of 62 eyes of 62 patients (32 with no perimetric glaucoma and 30 with concomitant perimetric glaucoma) evaluated between August 2010 and December 2010 were retrospectively analyzed and compared with regard to the optic disc morphometric parameter, disc area, rim area, cup-to-disc ratio (CDR), and cup volume. Receiver operating characteristic curves were constructed for the parameters and areas under the curves (AUCs) were compared.

Results

All parameters except disc area were significantly different between Cirrus OCT and HRT. Average cup-to-disc ratio (CDR), vertical CDR, and cup volume were greater when measured by OCT compared with HRT II (P = 0.002, P < 0.001, and P < 0.001, respectively). Rim area was smaller by OCT than by HRT II (P < 0.001). Of the parameters evaluated, rim area (0.938), average CDR (0.865), and vertical CDR (0.897) had higher AUCs with OCT than with HRT II. Glaucoma diagnostic capability using the AUC was greater for OCT than for the HRT.

Conclusions

Optic nerve head parameters measured by Cirrus OCT seem to be useful in differentiating glaucomatous optic nerve heads. The two types of instrument compared here should not be used interchangeably to obtain measurements of the optic disc for diagnosis of glaucoma.     

Optic disc topography in normal Indian eyes using spectral domain optical coherence tomography

Purpose:

The aim was to study optic nerve head (ONH) parameters in normal Indian eyes using spectral domain optical coherence tomography (OCT)/scanning laser ophthamoscope (SLO).

Materials and Methods:

One hundred and fifty-seven eyes of 157 normal subjects of various age groups underwent ONH imaging with spectral OCT/SLO and the parameters obtained were correlated with disc size. The effect of age, gender, and refractive error on various ONH parameters were also studied.

Results:

The mean optic disc area was 3.36 ± 0.64 mm² (range, 2.13–5.08 mm²), mean rim area was 2.49 ± 0.58 mm² (range, 1.20–3.62 mm²), and mean cup area was 1.10 ± 0.75 mm² (range, 0–3.07 mm²). The disc area showed significant positive correlation with the rim area, cup area, horizontal cup disc ratio, vertical cup disc ratio, cup disc area ratio, mean cup depth, and maximum cup depth (P < 0.001). Neither gender nor refractive error showed any significant difference in various ONH parameters. ONH parameters did not show significant change with age except for rim area which declined with the advancing age (r = –0.25, P < 0.001).

Conclusions:

The quantitative measurement of ONH topography obtained with this study provides a normative database for an Indian population with spectral OCT/SLO. As optic disc area influences ONH topography, disc size should to be considered when evaluating optic disc for progressive optic neuropathies such as glaucoma.     

Comparison of Optic Disc Topography Between Migrainous and Normal Subjects

The purpose of this study was to compare the optic disc topography parameters in migrainous and normal subjects, by using Heidelberg retinal tomograph (HRT). The topographic optic disc parameters of 29 nonglaucomatous eyes of 29 cases with migraine and 29 eyes of 29 normal subjects were compared with nonparametric Mann Whitney U test. The mean cup area (0.743 mm²) and cup to disc ratio (0.345) of migrainous subjects were greater than the mean cup area (0.591 mm²) and cup to disc ratio (0.288) of normal subjects (p = .009, p = .005). This result suggests that migrainous subjects have larger cup areas and higher cup to disc ratio ratios than normal subjects.     

The Heidelberg retina tomograph ancillary study to the European glaucoma prevention study: study design and baseline factors

Purpose: To describe the study design and baseline factors of the Heidelberg Retina Tomograph ancillary study within the EGPS. Furthermore, to examine the relationship between HRT optic disc topographic measurements and baseline demographic and ocular factors. Methods: Four hundred and eighty‐nine ocular hypertensive participants were included. Each participant completed HRT imaging at least annually. The associations between HRT measurements and IOP, central corneal thickness (CCT), baseline photographic estimates of vertical CDR ratio (CDR), asymmetry between the two eyes in CDR ratio and baseline visual field indices were assessed using regression analysis. Results: Associations between HRT measurements and vertical CDR by photographs were found for almost all stereometric optic disc parameters in both univariate and multivariate analysis. The strongest association was found between vertical CDR measurements and disc, cup and rim area; cup and rim volume, CDR area, linear CDR, mean and maximum cup depth and cup shape measure (all p < 0.0001). In multivariate analysis, pattern standard deviation (PSD) and HRT disc area had significant associations with several HRT optic disc measurements. Furthermore, CCT was significantly associated with reference height and the glaucoma probability score (GPS, outside normal limits). Conclusions: The EGPS is the first multicentre, placebo‐controlled randomized clinical trial to use HRT for monitoring optic disc changes in participants with ocular hypertension. We found strong associations between stereophotographic vertical CDR estimates, HRT disc area, PSD and several HRT parameters. We found, furthermore, that the parameters reference height and GPS were significantly related to central corneal thickness.     

Comparison of optic disc parameters using spectral domain cirrus high‐definition optical coherence tomography and confocal scanning laser ophthalmoscopy in normal eyes

Purpose: To compare Cirrus HD – optical coherence tomography (HD‐OCT) with confocal scanning laser ophthalmoscopy (HRT 3) for analysis of optic disc parameters in healthy eyes. Methods: In 126 subjects, cup volume (CV), vertical cup/disc ratio (CDR), neuroretinal rim area (NRA), cup area (CA) and optic disc area (ODA) were measured with the Cirrus HD‐OCT and HRT 3. These optic disc parameters were chosen for statistical analysis because they can be analysed in both OCT and HRT 3 and they are widely used parameters for glaucoma assessment. Results: Mean values and significances of paired t‐tests for OCT and HRT were for CV: 0.099 ± 0.11 versus 0.082 ± 0.10 (p < 0.001), CA: 0.42 ± 0.31 versus 0.39 ± 0.31 (p < 0.001), CDR: 0.36 ± 0.17 versus 0.27 ± 0.21 (p < 0.001). NRA and ODA were not significantly different between instruments. The Pearson coefficients were 0.905 (CV), 0.824 (CA), 0.734 (CDR), 0.295 (NRA) and 0.378 (ODA). Conclusion: To our interpretation, the delineation of the optic disc border is error‐prone with both instruments and all parameters directly depending on it are thus poorly correlated. However, the determination of the optic disc excavation (CV and CA) appears comparable taking into account a small systematic difference between instruments.     

Optic Disc Dimensions and Cup-Disc Ratios among Healthy South Indians: The Chennai Glaucoma Study

Purpose: To present optic disc and cup dimensions, cup-disc ratios (CDRs) and asymmetry among healthy South Indians, and their associations with ocular and systemic variables.

Methods: A total of 623 healthy phakic participants of the Chennai Glaucoma Study underwent complete eye examinations including optic disc stereo-photography. Planimetry was performed under stereo-viewing conditions. The morphological type of cupping (no cups, steep cups, partly sloping and fully sloping cups) was identified based on a modification of the classification by Jonas et al. The associations of planimetric measures (optic disc area, cup area and vertical cup-disc ratio [VCDR]) with age, gender, height, intraocular pressure, refraction, astigmatism, axial length and corneal thickness as explanatory variables were examined. The associations of asymmetries in the above planimetric measures with age, gender and asymmetries of the above explanatory variables were examined.

Results: Mean optic disc and cup areas were 2.82?±?0.52?mm² and 0.53?±?0.39?mm². Mean CDR was 0.36?±?0.18. Men had larger discs (P?=?0.03). Cup area and VCDR revealed significant associations with disc area (P <0.0001) and type of cupping (P?<?0.0001). Mean disc and cup area asymmetries were 0.19?±?0.16?mm² and 0.15?±?0.15?mm². Mean VCDR asymmetry was 0.07?±?0.08?mm². Cup area and VCDR asymmetries showed significant associations with disc area asymmetry (P?<?0.0001, both) and asymmetry in the presence or absence of physiological cupping, i.e. subjects with physiological cupping in one eye and no cupping in the other (P?<?0.0001, both).

Conclusions: We present normative optic disc, cup and VCDR measures and asymmetries among healthy South Indians. We demonstrated the dependence of VCDR on the morphological type of cupping.     

海德堡视网膜断层扫描仪测量正常人视盘参数

目的 :建立正常人群海德堡视网膜断层扫描仪 (Heidelbergretinatomograph ,HRT)视盘参数的正常值 ,明确哪些因素对正常人HRT视盘参数有影响。方法 :选用 10 2例 (13 2只眼 )正常人 ,用HRT进行视盘扫描 ,视盘参数包括视盘面积、视杯面积和容积、盘沿面积和容积、视杯形态、视杯平均深度和最大深度、杯 /盘面积比、沿 /盘面积比、平均视网膜神经纤维层(retinalnervefiberlayer,RNFL)厚度和横截面积、水平C/D和垂直C/D。计算正常人视盘参数范围 ,用直线回归的方法判断视盘大小和年龄对视盘参数的影响。结果 :正常人左右眼和男女间视盘各参数差异无显著意义 (P >0 0 5)。年龄与RNFL厚度及横截面积呈负相关 ,相关系数分别为 -0 2 3 4和 -0 2 3 5,其余各参数与年龄无关。盘沿容积和视杯最大深度不受视盘大小的影响 ,其余各参数均与视盘大小呈线性相关。结论 :HRT可定量检测正常人视盘参数 ;正常人视盘参数变异很大 ,盘沿容积不受视盘大小的影响 ,是一个区分正常与早期青光眼的很好的参数     

Assessment of optic disc parameters among healthy adult Malays by Heidelberg Retinal Tomograph II

Background: This study aims to assess the optic disc characteristics in healthy adult Malays and to correlate them with age, gender and refractive errors. Design: Cross‐sectional study. Participants: A total of 200 voluntary participants (106 women and 94 men) among Malay students aged 20 to 37 years at Health Campus, Universiti Sains Malaysia. Methods: The relationship between Heidelberg Retinal Tomograph parameters with age, gender and refractive error were analysed with correlation tests and multiple linear regression analyses. Main Outcome Measures: Twelve parameters, that is, disc area, rim area, cup area, cup to disc area, cup volume, rim volume, height variation contour, cup shape measure, mean cup depth, maximum cup depth, mean retinal nerve fibre layer thickness and retinal nerve fibre layer cross‐sectional area. Results: Disc area, rim area and cup : disc area ratio averaged 2.24 ± 0.52 (mean ± standard deviation), 1.64 ± 0.32 and 0.25 ± 0.12 mm², respectively. Five parameters (disc area, cup area, cup volume, cup : disc area ratio and mean retinal nerve fibre layer thickness) showed statistically significant difference between men and women. Age was negatively and significantly correlated with rim area with coefficient r = ?0.21, P = 0.003. All optic disc parameters were significantly correlated (P < 0.05) with disc area, except cup shape measure. Conclusions: One or more of optic disc parameters were affected significantly by age, gender and disc area in healthy adult Malays' eyes. These factors need to be considered during the evaluation of optic disc.     

视网膜断层扫描仪在青光眼性视神经病变中的诊断价值

目的　评价视网膜断层扫描仪在青光眼性视神经病变中的诊断价值。方法　应用海德堡视网膜断层扫描仪 (HRT)检测 116例 (116只眼 )正常人和 6 3例 (99只眼 )原发性开角型青光眼(POAG)患者的视乳头地形图参数 ,比较两者间各参数的差异 ;将正常人与POAG患者的视乳头地形图参数进行逐步判别分析 ,建立判别函数 ,筛选出诊断POAG的敏感参数并进行回代分析。结果POAG患者的视盘面积 (DA)、视杯面积 (CA)、杯 /盘面积 (C/DAR)、盘沿面积 (RA)、视乳头轮廓线高度变化值 (HVC)、视杯容积 (CV)、盘沿容积 (RV)、平均视杯深度 (MCD)、最大视杯深度 (MxCD)、视杯形态测量 (CSM)、平均视网膜神经纤维层厚度 (mRNFLT)、视网膜神经纤维层截面面积 (RNFLA)与正常人比较差异有显著意义 (P <0 0 0 1) ;对POAG诊断敏感的视盘地形图参数为C/DAR、RA、CSM、CV和MxCD ;判别函数式为Y =- 2 0 83- 4 833×C/DAR - 2 0 379×CSM 2 0 35×RA 3 95 5×CV - 3 70 1×MxCD ;对POAG诊断的敏感性、特异性及诊断符合率分别为 81 8%、86 2 %及 84 2 % ,与HRT自动分析程序相当。结论　POAG患者视乳头地形图与正常人差异较大 ;利用我国人的数据资料建立的判别函数对POAG诊断效能与HRT自动分析程序相当 ,说明HRT自动分析程序在一定程     

Does optic disc topography vary during office hours?

Purpose:  To investigate whether there is variation in optic disc topography as measured by the Heidelberg Retina Tomograph (HRT), in normals during office hours.
Methods:  Thirty normal subjects (22 females and 8 males, median age 28 years, range 18–58) underwent Goldmann tonometry and optic disc analysis with the HRT. Three HRT readings were taken at each visit and a mean topographic image (MTI) produced. Measurements were performed in the morning (07.00–09.00 hours) and were repeated later the same day (17.00–19.00 hours). We studied the following topographic parameters: cup-to-disc area ratio (CDR), rim volume (RV), cup shape measure (CSM), and retinal nerve fibre layer thickness (RNFLT) in relation to time of day and the change in intraocular pressure (IOP).
Results:  The median changes in the topographic parameters were as follows (a negative value indicates a larger value in the evening): CDR (median 0.001, 95% CI: −0.007 to 0.007), RV (median 0.003, 95% CI: −0.021 to 0.016), CSM (median: −0.003, 95% CI: −0.015 to 0.007) and RNFLT (median 0.006, 95% CI: −0.010 to 0.009). No parameter exhibited statistically significant change. The median morning IOP was 14 mmHg (95% CI: 13–16 mmHg) and was not significantly different (Wilcoxon's W  = 234; p  = 0.27) to evening IOP when it was 13 mmHg (95% CI: 12–15 mmHg). The median difference in IOP was 1 mmHg higher in the morning than the evening (range 6 mmHg higher in the morning to 4 mmHg higher in the evening). The parameter changes between the morning MTI and the evening MTI were independent of IOP changes using Kendall's tau statistic for each parameter.
Conclusions:  There was no variation in HRT parameters when measured during office hours. Small intraindividual changes in IOP do not significantly affect optic disc topography.     

Clinical evaluation of the Heidelberg Retina Tomograph II

PURPOSE: To evaluate the usefulness of Heidelberg Retina Tomograph (HRT) II prototype, which is an easily handled model for routine optic disc examination in glaucoma clinics. METHODS: Ten eyes of 10 normal volunteers and 18 eyes of 18 open-angle glaucoma patients followed at Gifu University were studied. The reproducibility of three consecutive optic disc measurements with a 15 degrees x 15 degrees field using HRT II and with a 10 degrees x 10 degrees field using HRT (version 2.01) were evaluated by the same examiner on the same day. We also examined the correlation of the main topographic parameters (disc area, cup area, cup/disc area ratio, rim area, cup volume, rim volume, cup shape measure) between HRT II and HRT. RESULTS: The mean (+/- standard deviation) reproducibility of optic disc measurements with HRT II and HRT were 17.5 +/- 7.6 microns and 19.3 +/- 9.6 microns, respectively. This difference was not significant. All topographic parameters obtained from HRT II and HRT (R = 0.86-0.98, p < 0.01) showed statistically significant correlations with each other. CONCLUSION: The HRT II has high reproducibility of measurements and reliable stereometric parameters comparable to the conventional HRT.     

Detection of optic disc change with the Heidelberg retina tomograph before confirmed visual field change in ocular hypertensives converting to early glaucoma

AIM: To determine whether analysis of sequential optic disc images obtained with the Heidelberg retina tomograph (HRT) is able to demonstrate optic disc change before the development of reproducible field defects in a group of ocular hypertensive (OHT) patients converting to early glaucoma. METHODS: Two groups were analysed: (1) 13 eyes of 13 OHT patients who subsequently developed reproducible field defects (converters); and (2) 13 eyes of 11 normal control subjects. Two sequential optic disc images were obtained using the HRT (median separation between images was 12 months for the converters and 13 months for the normals). The second image in the converter group was obtained before confirmed visual field loss. The optic disc variables were analysed both globally and segmentally using HRT software version 1.11. The Wilcoxon signed rank test was used to determine if there were any significant differences between the variables of the two image sets. RESULTS: Significant optic disc change was demonstrated in the group of converters: (1) global variables: the cup area increased by 9.7%, the C/D area ratio increased by 10.5%, and the rim area decreased by 6.9%; (2) segmental variables: the superonasal cup area increased by 11.0%, the superonasal C/D area ratio increased 11.7%, and the inferonasal cup volume increased by 28.4%. The temporal rim volume decreased by 15.6%, the inferotemporal rim volume decreased by 23.6%, and the rim area in the superonasal and superotemporal segments decreased by 6.6% and 6.9% respectively. CONCLUSION: Analysis of sequential optic disc images on the HRT allowed the detection of glaucomatous change before confirmed visual field change in a group of OHT patients converting to early glaucoma.     

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 group1 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.     

Eccentric ruthenium plaque radiotherapy of posterior choroidal melanoma

Background

The aim of this work is to report on conservation of visual acuity after eccentric ruthenium¹⁰⁶ (Ru-106) brachytherapy of posterior choroidal melanoma.

Methods

Fifty-four patients with choroidal melanoma extending to within 5?mm of the optic disc or fovea were treated at a single institution during the 3?years up to July 31, 2007. The plaque was positioned eccentrically with its posterior edge aligned with the posterior tumor margin to reduce the radiation dose to the optic disc and fovea. The main outcome measures were local tumor control and conservation of vision of 6/12 or better, according to baseline variables.

Results

The tumors had a mean longest basal diameter of 12.0?mm and a mean thickness of 3.1?mm. The posterior tumor margin extended to within 3?mm of the fovea in 30 patients (56%). In the 24 eyes with the posterior tumor margin located 3.1–5.0?mm from the fovea, 74.9% retained visual acuity of 6/12 or better 4?years after treatment (95% confidence interval [CI], 55.5–94.3%). In the 30 eyes with tumor extension to within 3.0?mm of the fovea, then 3?years after treatment only 25.3% retained such vision (95% CI, 5.3–45.3%). Recurrence at the posterior tumor margin occurred in two patients.

Conclusions

Eccentric ruthenium¹⁰⁶ plaque radiotherapy of posterior choroidal melanoma achieves good rates of local tumor control and conservation of vision if special measures are taken to ensure that the plaque is positioned correctly.     

Influence of disc area on retinal nerve fiber layer thickness measurement by spectral domain optical coherence tomography

Background:

To examine the effect of optic disc area on peripapillary RNFLT (retinal nerve fiber layer thickness) measurement at circle diameter of 3.4 mm around optic nerve head using spectral OCT/SLO (Optical coherence tomography/scanning laser ophthalmoscope).

Materials and Methods:

In this prospective, cross sectional study, one hundred and two eyes of 102 normal subjects underwent RNFLT and disc area measurement using spectral OCT/SLO. Based on disc area, subjects were divided into three groups i.e., <3 mm² (32 eyes), 3-4 mm² (36 eyes) and >4 mm² (34 eyes). The effect of disc area on RNFLT parameters was analyzed using linear regression analysis.

Results:

The mean and quadrant RNFLT did not show significant correlation with disc area in subjects with disc area of <4 mm², however in eyes with disc area >4 mm², average RNFLT, superior and temporal quadrant RNFLT showed negative correlation with disc area, which was statistically significant (P = 0.004, P = 0.005 and P = 0.002, respectively)

Conclusion:

In healthy eyes of disc area <4 mm², disc size does not appear to affect peripapillary RNFLT measurement by spectral OCT/SLO. Average, superior and temporal quadrant RNFLT measurements were inversely proportional to disc area in eyes with disc area >4 mm². Hence, RNFLT measurement by OCT in eyes with optic disc area of >4 mm² should be interpreted carefully.     

Use of sequential Heidelberg retina tomograph images to identify changes at the optic disc in ocular hypertensive patients at risk of developing glaucoma

AIM: To determine if global and segmental changes in optic disc parameters of sequential Heidelberg retina tomograph (HRT) images develop in individual ocular hypertensive (OHT) patients without white on white visual field defects. METHODS: Patients and normal controls were recruited from a prospective ocular hypertension treatment trial. The subject groups consisted of 21 OHT patients who had converted to early glaucoma on the basis of visual field criteria (24-2 program on the Humphrey perimeter), 164 OHT subjects with normal visual fields, and 21 normal controls. Sequential HRT images 16-21 months apart were obtained for each subject and segmental optic disc parameters were measured to determine if any change had occurred. From the analysis of sequential HRT images of the 21 normal eyes we established normal limits of interimage variation. Individual discs in each group showing changes above the 95% limit of normal variability were then sought. RESULTS: Several segmental and global optic disc parameters were found to show significant change in the converter group before confirmed visual field change, confirming our previously published results. Individual optic disc analysis using the 95% limit of normal variability data demonstrated glaucomatous change in 13 out of 21 converter eyes. 47 of the 164 OHT eyes with normal visual fields showed change in global and segmental parameters in a "glaucomatous" direction above the level expected for normal variability. The parameters which changed most frequently in the OHT eyes were: global cup volume (6.7% of discs), inferonasal cup volume (11%), inferotemporal cup volume (8.5%), and superotemporal cup area (7.3%). CONCLUSIONS: We have identified change in a subset of ocular hypertensive patients which could predate the development of glaucomatous visual field loss. The HRT could be of value in the sequential follow up of those suspected of having glaucoma by identifying eyes at risk of developing glaucoma. However, further refinement of the technique is required to eliminate some of the inherent variability of the analysis method described, and to increase the ability to detect at risk individuals.     

Heidelberg retina tomograph in ocular Behçet's disease

PURPOSE: To compare the optic disc topography of patients with ocular Beh?et's disease (BD) with age-matched controls, using Heidelberg retina tomograph (HRT). METHODS: This study included 32 patients (51 eyes) with ocular BD (active and/or inactive), 38 patients (74 eyes) with nonocular BD, and 62 normal subjects (62 eyes). All patients and control group underwent complete ophthalmologic evaluation. Intraocular pressure was less than 22 mmHg in patients and in the control group. The optic nerve heads of all subjects were imaged with the HRT (software 2.01a-M). The following stereometric parameters were calculated for each patient: disc area, cup area, cup/disc area ratio, rim area, height variation contour, cup volume, rim volume, mean cup depth, cup shape measure, mean RNFL thickness, and RNFL cross-sectional area. Differences among the groups were evaluated by Kruskal-Wallis variance analysis. When the Kruskal-Wallis test revealed a significant difference between groups, multiple comparison tests were used to find out which groups differed from which others. RESULTS: The mean disc area was significantly smaller (P<0.05) in patients with ocular and nonocular BD. The mean cup area, mean cup depth, and mean cup volume were significantly smaller (P<0.05) in patients with ocular BD. No significant differences were found between the groups in terms of the other stereometric parameters (P>0.05). CONCLUSION: A small disc and cup may be an additional risk factor for retinal vaso-occlusion in ocular Beh?et's disease.     

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 × 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.

Keywords: cup/disc ratio; glaucoma; imaging