Aims: To evaluate the test-retest variability of stereometric parameter measurements made with the Heidelberg retina tomograph (HRT) and Heidelberg retina tomograph-II (HRT-II), and to establish which parameter(s) provided the most repeatable and reliable measurements with both devices. An investigation into the factors affecting the repeatability of the measurements of this parameter(s) was conducted. Methods: 43 ocular hypertensive and 31 glaucoma subjects were recruited to a test-retest study. One eye from each subject underwent HRT and HRT-II imaging by two observers on each of two occasions within 6 weeks of each other. Lens grading was carried out by LOCS III grading and Scheimpflug camera generated densitogram analysis. Results: Rim area (RA) and mean cup depth measurements were found to be least variable. Both inter-test reference height difference and image quality had a strong relation (R 2 .0.5, p,0.0001) with inter-test RA difference and, together, are responsible for 70% of RA measurement variability. Image quality was influenced by lens opacity, cylindrical error, and age. Inter-test RA measurement differences were unrelated to the observer or visit interval. Conclusions: RA represents an appropriate measure for monitoring glaucomatous progression. Reference height difference and image quality were the factors that most influenced RA measurement variability. Image analysis strategies that address these factors may reduce test-retest variability.

Aims: To devise and test strategies for improving Heidelberg retina tomograph (HRT and HRT-II) rim area (RA) repeatability and assess the benefit of the strategies in time series of HRT images. Methods: The effect of the standard and 320 mm reference planes and image quality on RA repeatability was assessed in a test-retest HRT image dataset from 74 subjects. A longitudinal HRT image dataset from 30 ocular hypertensive subjects was analysed by linear regression of RA over time, with each of the reference planes and using a manual image alignment facility. RA variability was estimated by comparing the standard deviation of residuals (RSD) generated by each linear regression. Results: RA repeatability was better with the 320 mm reference plane (repeatability coefficient 0.17 mm 2 ), improving further with only good quality images (repeatability coefficient 0.08 mm 2 ). For the longitudinal data, a significant (p,0.0001) reduction in the RSD from 0.10 to 0.05 mm 2 was obtained with the 320 mm reference plane. Manual alignment led to a further significant (p,0.0001) reduction in the RSD to 0.04 mm 2 . Conclusions: The findings support the use of a 320 mm reference plane and manual image alignment to analyse RA over time. The estimates of RA repeatability may be used to define thresholds for glaucomatous change.

The IVF provides a method by which binocular visual fields can be incorporated into patient management and allows, for example, a prediction of future driver's license loss. The rate of binocular IVF sensitivity loss at 2 years of follow-up may help identify patients who could benefit from intensified intervention.

Ultrasound is a useful modality in the evaluation of acute cervical masses but is observer dependent and has a relatively low sensitivity in detecting whether or not pus is present. The clinical indicators for the presence of an abscess are discussed and clinicians should combine clinical findings with the ultrasound findings in order to determine treatment.

Noise in HRT measurement of RA is well characterized by the hyperbolic distribution. Sensitivity of detection improves with more frequent testing, but if consistently poor-quality images are yielded for a patient, the probability of detection is low. Results from this work could be used to tailor individual follow-up patterns for patients with different rates of RA loss and image quality, especially in a clinical trial setting.