Is It Necessary to Have Optic Disc Photos to Measure Optic Disc Parameters From the Heidelberg Retinal Tomograph?

Abstract

Purpose: : We aim to evaluate the measurement of optic disc morphology using the Heidelberg Retinal Tomography (HRT) with and without the aid of optic disc photos.

Methods: : 103 children (aged 11 and 12 years, 52 boys) were selected randomly from the Singapore Cohort study of Risk Factors for Myopia (SCORM). Optic nerve head topography and retinal nerve fiber layer (RNFL) thickness measurements were assessed using the HRT-II (Heidelberg, Germany) scanning laser ophthalmoscope with correction for refractive errors. All contour lines were drawn by the same researcher on two occasions. The first drawing was done without the aid of optics disc photographs. The second drawing, done two days later, was made with the aid of the 3-dimensional rotation assessment and digital monoscopic optic disc photographs.

Results: : There was a high correlation between measurements made without and with optic disc photographs. For global disc area readings, difference between the mean readings was 0.67 mm² and the intraclass correlation (ICC) was 0.81 (95% CI 0.73 to 0.86). The mean difference in readings for global cup to disc ratio was 0.03 and ICC was 0.86 (95% CI 0.80 to 0.90). The ICCs were high across almost all of the readings except rim volume, where the ICC was 0.57 (95% CI 0.43 to 0.69).

Conclusions: : This study shows minimal differences in HRT measured optic disc parameters when optic disc photos are used to aid in the definition of the scleral ring. Omitting the use of disc photographs in measuring HRT outputs may translate into significant savings in time and logistics in simultaneously obtaining HRT and optic disc photographs in large population based studies.

Keywords: imaging/image analysis: clinical • clinical (human) or epidemiologic studies: systems/equipment/techniques • optic nerve