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J.M. Wild, I. Bourtsoukli, I.A. Cunliffe, E.A. Ansari, K. Rajkumar, R.V. North, J.E. Morgan; Patterns of Normal Neuroretinal Rim Configuration: The Reliability of the ISNT Rule in Clinical Decisions for Glaucoma . Invest. Ophthalmol. Vis. Sci. 2005;46(13):2494.
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The width of the neuroretinal rim in normal eyes is consideredto follow a distinct pattern – the ISNT rule: the rimis widest in the inferior sector of the disc, followed by thesuperior, the nasal, and the temporal sectors1.
To determine the efficacy of the ISNT rule for thedetection of open angle glaucoma (OAG) based on digital stereoscopicoptic disc analysis.
Optic disc images from 51 normal subjects (mean age58.9 years, SD 10.6) and from 80 patients with early to severeOAG (mean age 66.7 years, SD 10.4) were digitised and then analysedby planimetry, masked to patient diagnosis, by three ophthalmologiststrained to fellowship standard in glaucoma. Diagnosis, by twoexperts, was based on concurrent disc damage and visual fieldloss. Stereoscopic images were viewed using a Z screen (StereographicsCorp.) with quad buffered display (24 bits per pixel true colour)and were corrected for magnification factors. The rim was measuredwith custom cursors at the level of the scleral rim and in 5–degreeintervals. The rim area was summed in four equal sectors (I,S,N,T)subtending 10° and 30° respectively. Analysis was basedon the rule that I>S>N>T indicated normality.
References. 1.Jonas, Gusek & Naumann, 1988. IOVS 29: 1151–1158.
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