Abstract
Abstract: :
Purpose: To determine the sectors of the optic nerve head (ONH) which are related to each point in the visual field using empirical longitudinal patient data. Methods: 24–2 visual fields (either full threshold and SITA Standard) using standard automated perimetry (SAP) on a Humphrey Field Analyzer, and ONH images using the Heidelberg Retinal Tomography (HRT) instrument, were taken annually for both eyes of 164 patients with early glaucomatous visual field loss or glaucomatous optic neuropathy as determined by evaluation of simultaneous stereo optic disc photographs (mean 4.15 fields per eye; minimum 3, maximum 7). For inclusion in this study, the visual field and HRT measures had to be carried out within 21 days of each other. The HRT was then used to split the ONH into 36 ten–degree sectors, and provide a measurement of the rim area in each. These measurements were normalized to account for changes in the total rim area between discs, to indicate sectors whose rim is thinner than would be expected for a normal patient (based on a database of 218 normal eyes). Sectors were sought which were most correlated with the sensitivity of each point (in turn) in the 24–2 visual field. Results: Individual ONH sector / SAP point correlations ranged from –0.088 to 0.477 (mean 0.093). The best correlation at each SAP point ranged from 0.13 to 0.48 (mean 0.27). In almost all cases, the ONH sectors found to be best correlated with the sensitivity of a given point conformed with expectations. Points in the superior hemifield tended to be best correlated with the inferior and slightly temporal area of the ONH (roughly between 4 and 7 o’clock for a right eye); points in the inferior hemifield tended to be best correlated with the superior and slightly temporal area of the ONH (between 12 and 2 o’clock for a right eye). Best correlated sectors tended to be nearer vertical than the entry points into the ONH of corresponding retinal nerve fiber bundles. Conclusions: A map relating SAP test points to regions of the ONH has been produced. This may be useful in providing a structure–function relationship for cases of localized glaucomatous loss.
Keywords: imaging/image analysis: clinical • perimetry • optic disc