Teleglaucoma: ready to go?

Telemedicine technologies and services allow today's ophthalmic clinicians to remotely diagnose, manage and monitor several ophthalmic conditions from a distance. But is this the case for glaucomas? There has been a proliferation of telemedicine friendly devices in recent years that improves the capabilities of the clinician in managing glaucomas. The existing instruments still need to align themselves with accepted industry standards. There are successful programmes running in several areas of the world. The safety and efficacy of these programmes needs further exploration. The inability of a single device or test to diagnose glaucomas satisfactorily has also hampered progress in remotely diagnosing these conditions. There is, however, significant potential for telemedicine-friendly devices to remotely monitor the progress of glaucoma and, thereby, reduce some of the workload on an overstretched health service.

HRT-3 Moorfields reference plane: effect on rim area repeatability and identification of progression.

AIMS: To assess the effect of the Moorfields Reference Plane on Heidelberg Retina Tomograph (HRT) rim area repeatability and its effect on progression rates using an event analysis. METHODS: The HRT reference plane (RP) defines structures above as "rim" and below as "cup." The Moorfields RP applies the Standard RP (located 50 microm posterior to the temporal disc margin) at baseline and maintains the distance between the Standard RP and the reference ring (located in the image periphery) for follow-up images. The Moorfields RP was applied to an HRT test-retest dataset, and rim area repeatability coefficients were calculated. Repeatability coefficients were compared between the Moorfields, Standard and 320 (located 320 microm posterior to the reference ring) RPs. The Moorfields RP was applied to HRT images from 198 ocular hypertensives, acquired over 6 years. HRT progression required rim area baseline/follow-up differences exceeding the repeatability coefficient in two or more sectors, with confirmation in at least one of two consecutive images. Field progression was assessed using Advanced Glaucoma Intervention Study criteria. RESULTS: The Moorfields RP improved rim area repeatability compared with the Standard RP; repeatability was similar between the Moorfields and the 320 RP. The frequency of identified progression using Moorfields RP was 40% compared with 28% for the 320 RP. There was a greater percentage with concurrent field progression -15.1% (Moorfields RP) compared with 12.1% (320 RP). CONCLUSIONS: Although rim area repeatability was similar using the 320 RP and the Moorfields RP, the latter resulted in greater rates of detection of change.

Factors affecting the test-retest variability of Heidelberg retina tomograph and Heidelberg retina tomograph II measurements.

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.

Improving the repeatability of Heidelberg retina tomograph and Heidelberg retina tomograph II rim area measurements.

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 microm 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 microm 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 microm 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 microm 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.