Dr. SUJATA LAKHTAKIA

Dr. EVA RANI TIRKEY, Dr.Anamika Dwivedi, DR. DIVYA TRIPATHI

Abstract

PURPOSE: To determine the validity of ISNT rule and its variants in normal eyes by spectral domain- OCT.

METHODOLOGY: The study included 124 eyes of 62 normal subjects in whom the neuro-retinal rim was assessed by measuring the retinal nerve fibre layer (RNFL) thickness using spectral domain-OCT.

RESULTS: The ISNT rule was reliable in only 58.06% of RNFL measurements. Wider superior rim compared to inferior rim was seen in 14.51% and wider temporal rim compared to nasal rim in 27.4%.The validity of ISNT variant rules increased by exclusion of nasal quadrant with 85.48%, 83.87% and 69.35% following the IST, IS and thinnest T rules respectively.

CONCLUSION: The ISNT rule was found valid for only around half of RNFL measurements in normal patients. ISNT rule variants such as the IST and IS rule maybe considered as they are valid in over 80% of patients.
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