Abstract
Purpose: :
To evaluate the reproducibility and diagnostic accuracy in detecting glaucoma of the retinal nerve fiber layer(RNFL)macular thickness measurement provided by posterior pole scanning protocol with Spectralis spectral domain(SD) OCT (Heidelberg Engineering).
Methods: :
Seventy-four eyes from 74 normal subjects and 106 eyes from 106 glaucoma patients attending our institute, were consecutive enrolled. All patients underwent a full eye examination, standard achromatic perimetry (Humphrey Field Analyzer,SITA 24-2 program, Carl Zeiss Meditec) and imaging session with Spectralis SD-OCT. Abnormal and repeatable(>2 consecutive) visual field test results, defined as PSD and MD with p<5% and Glaucoma Hemifield Test outside normal limits, were used to classified glaucomatous eyes.Posterior pole scanning protocol(conducted three times during the same visit) analyze central 20° macular area, and RNFL macular thickness is calculated globally, for superior and inferior hemisphere, and for 64 squares with 3° x 3° area. Each small square were numbered from 1(supero nasal) to 64 (infero temporal) and taken individually.Reproducibility was assessed by Intraclasss Correlation Coefficient(ICC), Coefficient of Variation(COV) and test-retest variability. Area under receiving operating characteristics(AROC) curve and sensitivity at ≥90% fixed specificity were calculated to assess the diagnostic ability of each parameter.
Results: :
ICC ranged from 0.959(square number 23) to 0.999(four squares) for glaucoma patient, from 0,956(square number 30) to 0,999(six squares ) for normal. CoV ranged from 0,9% to 1,5 % and from 0,7% to 1,3% for glaucoma and normal respectively. Test retest variability ranged from 1,9 to 5,5 µm for glaucoma and from 1,8 to 5,8 µm for normal.The AROC curve ranged from 0,647 to 0,916(square number 1). Square number 2 showed the best sensitivity at >90 fixed specificity(76,09%). Totally, the squares in the upper and in the lower area of central 20° macular region had the highest performance.
Conclusions: :
Retinal nerve fiber layer macular thickness measurement provided by Spectralis SD-OCT have shown a high reproducibility in both normal and glaucoma subjects and a moderate to good diagnostic ability in detecting glaucoma damage.
Keywords: imaging/image analysis: clinical • nerve fiber layer • optic nerve