Optic Nerve Head Topographic Measurements Research Articles

A Comparison of Optic Nerve Head Topographic Measurements by Stratus OCT in Patients With Macrodiscs and Normal-sized Healthy Discs

To evaluate and compare optic nerve head parameters and retinal nerve fiber layer (RNFL) thickness between large discs and normal-sized vital discs using Stratus optical coherence tomography (OCT). A total of 293 healthy eyes (145 with macrodisc and 148 with normal-sized disc) were enrolled in the study. After a complete ophthalmic evaluation, measurement of optic nerve head parameters and RNFL thickness using OCT was performed in all subjects. Optic disc areas larger than 2.80 mm were accepted as macrodiscs. All OCT parameters were compared between normal-sized discs and macrodiscs. Participants' mean age was 46.5±10.6 years (range, 13 to 74 y). Average optic disc areas were 2.19±0.29 and 3.02±0.29 mm in the normal and the macrodisc groups, respectively. The optic disc area (P<0.0001), the cup area (P<0.0001), the horizontal cup disc ratio (P<0.0001), the vertical cup disc ratio (P<0.0001), and the cup disc area ratio (P<0.0001) were found to be significantly different in the macrodisc group and the control group. Rim areas (P=0.57) and RNFL thicknesses (inferior, superior, and mean) were found to be similar in both groups (P=0.75, 0.65, 0.85, respectively). A macrodisc may have a macrocup and should not be misdiagnosed as glaucoma. The present study showed that macrodiscs are identical to normal-sized discs in terms of rim area and RNFL thickness. We suggest that these 2 OCT parameters can help to differentiate a healthy macrodisc from a glaucomatous optic disc.

Optic Nerve Head Topographic Measurements and Retinal Nerve Fiber Layer Thickness in Physiologic Large Cups

To evaluate the parameters of optic nerve head (ONH) and retinal nerve fiber layer (RNFL) in patients with large cup/disc ratio (CDR) and normal neuroretinal rim configuration who have normal perimetry (physiologic large cups, LC) and to compare these parameters with those of the normal and early glaucoma patients. Using Heidelberg retinal tomography (HRT) and optical coherence tomography (OCT), 30 patients with LC, 29 normal subjects, and 31 early glaucoma patients were examined. One eye from each subject was randomly selected. Significant differences between LC and glaucomatous eyes (GE) were found in parameters indicating loss of nerve fibers, such as rim area, rim volume, and mean RNFL thickness. However, there was no difference between LC and normal eyes (NE) in RNFL thickness, rim area, and rim volume. LC was able to be defined as a normal central excavation with a large disc and large CDR with a normal rim area. HRT ONH parameters and RNFL thickness obtained with OCT may be useful for differentiating between glaucoma and LC eyes.

Effect of scan repetition on the reproducibility of optic nerve head topographic measurements with the Top SS.

To determine the effect of scan repetition during a single visit for improved reproducibility of optic nerve head topographic measurements. One randomly selected eye of 20 healthy subjects with no systemic or ocular disease was evaluated. Half of the subjects were under 30 years of age and the other half were older than 60 years. Five independent image series, each consisting of 10 newly recorded consecutive images, were obtained for each subject over a period of 10 weeks with a confocal scanning laser ophthalmoscope, the Top SS. Subjects were divided into two groups according to disc area being either smaller or larger than 2 mm2. Reproducibility of the measurements in three parameters (volume below, half depth area and the average depth) were calculated for each set of scans. The coefficient of variation (standard deviation divided by the mean) was taken as the measure of reproducibility. Repeated measures of analysis of variation and independent sample t-test were used for statistical analysis. Statistical significance was set as P < 0.05. Both age groups were found to be equally distributed with respect to sex. There were no significant intergroup differences in keratometry, pupil diameter or refractive error. Increasing the scan repetition per visit up to five improved the reproducibility of the measurements. Further increases in scans per visit reduced the reproducibility. Subjects with larger discs and older age were found to have lower coefficients of variation for topographic measurements. Normal subjects should be examined at least three to four times per visit to have significantly improved reliability of measurements of optic nerve head topography. Factors associated with decreased reproducibility included older age, smaller discs, and more than five scans per visit. Sex, refraction and pupil diameter were shown to have no effect on the reproducibility.

Reproducibility of the Measurements of the Optic Nerve Head Topographic Variables with a Confocal Scanning Laser Ophthalmoscope

Purpose: To determine the optic nerve head topographic parameters with the least variability in repeat measurements. Methods: We randomly selected and evaluated 1 eye each of 20 healthy subjects, a total of 20 eyes. We used the confocal scanning laser ophthalmoscope (CSLO) for optic nerve head analysis. The disc area and a total of 13 parameters were determined by Top SS. Each subject was examined five times, each time on a different day, during a 2-month period. We obtained a series of five 10 × 10° images for each eye per visit. Three of the five images were randomly selected to create a mean image. Coefficients of variation of each of the 13 variables studied were calculated separately by using those five different optic nerve head topographic measurements. Results: The subjects were 11 women and 9 men. The mean age of the subjects was 30.5 ± 6.9. The mean optic disc areas were 2.26 ± 0.39 mm 2 and 1.96 ± 0.37 mm 2 for the men and the women, respectively ( P > .05). The mean coefficient of variation for measurement of the variables was found to range between 1.2% and 9.8%. The variables, cup shape, volume above, average depth, and volume below, were found to yield the best reproducible measurements. Conclusion: The CSLO with its highly reproducible measurements (<10% error) offers a highly objective, safe, and effective method for clinical use in measurements of the topography of the optic nerve head. The subtle differences in the variables, cup shape, volume above, average depth, and volume below, may be of vital importance in the follow-up of those diseases requiring longitudinal monitoring of the optic nerve head, namely ocular hypertension and glaucoma.

Relation of optic disc topography and age to thickness of retinal nerve fibre layer as measured using scanning laser polarimetry, in normal subjects

AIMSTo evaluate the relation of the optic nerve head topographic measurements and age with the thickness of the retinal nerve fibre layer (RNFL) in normal Caucasoid subjects by means of...

Hemifield association between blue-on-yellow visual field and optic nerve head topographic measurements.

Blue-on-yellow (B/Y) perimetry can reveal visual field defects earlier and larger in extent than white-on-white (W/W) perimetry. The Heidelberg Retina Tomograph (HRT) produces a three-dimensional image of the optic disc. The aim of this study was to compare the strength of the association of the B/Y and W/W visual hemifield mean deviation (HMD) variables with the optic nerve head (ONH) morphological variables of the respective area. We evaluated one randomly chosen eye of 40 normal subjects and 37 patients with ocular hypertension and different stages of glaucoma. The B/Y and W/W visual fields (program 30-2) were obtained with a Humphrey perimeter. Results of both visual fields were adjusted for the patient's age and lens transmission index measured with a lens fluorometer. HMD was calculated as the difference between the measured and expected hemifield mean sensitivity values, predicted by the regression model fitted in our nonglaucomatous subject data. The HRT with the software version 1.11 was used to acquire and evaluate the topographic measurements of the optic disc. The B/Y and W/W visual field HMDs showed statistically significant correlation with ONH parameters such as cup shape measure (CSM), rim volume, rim area, mean retinal nerve fiber layer (RNFL) thickness and RNFL cross-sectional area. With forward stepwise logistic regression analysis using B/Y hemifield data 38% of the glaucoma patient's normal W/W hemifields were classified abnormal. With the CSM alone in the model 52% of the cases were classified abnormal. B/Y visual field hemifield mean deviation values correlate well with ONH parameters examined with the HRT.

P 302 Reproducibility of optic nerve head topographic measurements with the glaucomascope (3.10)

P 302 Reproducibility of optic nerve head topographic measurements with the glaucomascope (3.10)

Reproducibility of optic nerve head topographic measurements with the glaucomascope (3.10)

Reproducibility of optic nerve head topographic measurements with the glaucomascope (3.10)

Reproducibility of Optic Nerve Head Topographic Measurements with the Glaucoma-Scope

Our purpose was to evaluate the reproducibility of optic nerve head depth measurements using the Glaucoma-Scope. Optic nerve head topography was measured with the Glaucoma-Scope in 10 normal subjects and in 10 patients with glaucoma. Five separate readings were obtained by a single observer from one eye of each subject on the same day. Mean depth values were calculated for the overall disc, each quadrant, and areas overlying vessels at those points at which the change from baseline exceeded 50 mum. Similar calculations were made for actual depth measurements in regions of potential clinical interest, including the bottom of the cup, the temporal slope, the nasal disc, and a peripapillary region, as well as 15 randomly selected single points. Reproducibility of the depth values was determined by calculating standard deviations, coefficients of variation, and 95% confidence intervals in the five separate measurements. The mean standard deviations in regions of potential clinical interest among the 20 subjects ranged from 3.98 mum to 14.09 mum, and the mean coefficient of variation ranged between 4.2% and 8.7%. The 95% confidence intervals for the total population ranged from 9.88 mum to 34.97 mum for the regions of interest and was 43 mum for the 15 random points. There was no statistically significant difference in reproducibility between the two groups of subjects. In this study the Glaucoma-Scope produced quantitative optic nerve head topographic measurements that were highly reproducible, within a tolerance of <50 mum.

Changes in Glaucomatous Optic Disc Cupping or Variability of Computerized Topographic Measurements?

To the Editor. —We read the interesting article by Shin et al 1 in the November 1989 issue of theArchiveson the reversal of glaucomatous optic disc cupping. Though their findings are of significance, we feel that an important issue has been overlooked while interpreting the computerized topographic measurements of the optic nerve head. It is essential to distinguish random variability associated with the technique of computerized topographic measurements from actual changes in the optic nerve head over time. Based on repeated measurements on the same eyes, previous studies have reported confidence levels for the variability of optic nerve head topographic measurements with different computerized image analyzers. 2,3 Shin et al 1 used the Rodenstock analyzer. For this instrument, Bishop et al 2 calculated that two measurements on the same glaucomatous eye would have to differ by at least 0.138, 0.273 mm, 2 and 0.189 mm 3 for the

Reliability of Optic Nerve Head Topographic Measurements With Computerized Image Analysis

We evaluated the reliability of optic disk area and disk rim area measurements obtained with the Humphrey Retinal Analyzer from ten repeat fundus images each of one eye of ten normal subjects and ten subjects with increased intraocular pressure. Variability of rim and disk areas was not significantly different between these two groups (P greater than .05), nor was it significantly different between images acquired during the same session and those acquired during different sessions (P greater than .05). Variability was significantly different between subject groups based on the distinctness of the disk edge and the slope of the cup wall (P less than .01). The average minimum change in the measurements on the same eye that would exceed variability of the technique at the 95% confidence level was 0.20 mm2 and 0.47 mm2 for rim area for the least variable and most variable subject groups based on optic nerve head characteristics, and 0.09 mm2 and 0.32 mm2 for disk area for the corresponding subject groups. Operator input contributed significantly to overall variability. Reliability of rim and disk areas in this study was comparable to that reported for other computerized image analyzers.