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Abstract #61064 Published in IGR 17-1
Applicability of ISNT and IST rules to the retinal nerve fibre layer using spectral domain optical coherence tomography in early glaucoma
Dave P; Shah JBritish Journal of Ophthalmology 2015; 99: 1713-1717
BACKGROUND: To report the applicability of ISNT (inferior>superior>nasal>temporal) and IST (inferior>superior>temporal) rules on the retinal nerve fibre layer (RNFL) using spectral domain optical coherence tomography (SD-OCT) for detecting early glaucoma. METHODS: A prospective, cross-sectional study which included 80 eyes of 80 normal subjects and 76 eyes of 76 patients with early glaucoma by Hodapp-Anderson-Parrish classification. All subjects were of age more than 18 years, best corrected visual acuity 20/40 or better and a refractive error within ±5 dioptres (D) sphere and ±3 D cylinder. Control subjects had a normal ocular examination, intraocular pressure <22 mm Hg, no past history of high intraocular pressure, no family history of glaucoma, normal optic disc morphology and visual field. All eyes underwent SD-OCT examination for RNFL analysis. The sensitivity, specificity and likelihood ratio for violation of ISNT and IST rules was calculated for early glaucoma diagnosis. RESULTS: The ISNT rule was followed by 44 (55%) normal and 28 (36.84%) early glaucoma eyes. The IST rule was followed by 48 (60%) normal and 40 (52.63%) early glaucoma eyes. The sensitivity/specificity for violation of ISNT and IST rules for early glaucoma diagnosis was 63.2%/55% and 47.4%/60% respectively. The positive/negative likelihood ratio for ISNT and IST rules was 1.4/0.67 and 1.2/0.88, respectively, for diagnosing early glaucoma. CONCLUSIONS: Even though useful during ophthalmoscopy, ISNT and IST rules by themselves don't clearly distinguish normal eyes from those with glaucoma when applied to the quadrant values on RNFL on SD-OCT examination.
Dr. T V Patel Eye Institute, Vadodara, Gujarat, India.
Full articleClassification:
6.9.2.2 Posterior (Part of: 6 Clinical examination methods > 6.9 Computerized image analysis > 6.9.2 Optical coherence tomography)
2.13 Retina and retinal nerve fibre layer (Part of: 2 Anatomical structures in glaucoma)
