Browsing by Author "Khanal, Safal"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Comparison of retinal nerve fiber layer and macular thickness for discriminating primary open-angle glaucoma and normal-tension glaucoma using optical coherence tomography
    (Wiley, 2016-07) Khanal, Safal; Davey, Pinakin Gunvant; Racette, Lyne; Thapa, Madhu; Department of Ophthalmology, IU School of Medicine
    Purpose The aim of this study was to evaluate the discrimination capabilities of macular and peripapillary retinal nerve fiber layer (pRNFL) thickness parameters as measured using spectral domain optical coherence tomography (SD-OCT) between primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG). Methods A total of 90 subjects were enrolled: 30 healthy subjects, 30 subjects with POAG and 30 subjects with NTG, consecutively. Retinal nerve fiber layer thickness, macular thickness and volume measurements were obtained with circular and radial SD-OCT scans. All parameters were compared between groups using an analysis of variance test. Areas under receiver-operating characteristic (AROC) curves with sensitivities at specificities greater than or equal to 90 per cent were generated to compare discrimination capabilities of various parameters between POAG and NTG. Results Macular thickness and volume measurements were the highest in normal subjects, followed by NTG and POAG (p < 0.05). Average retinal nerve fiber layer thickness had perfect discrimination for normal-POAG (AROC: 1.000; sensitivity: 100 per cent) and near perfect discrimination for normal-NTG (AROC: 0.979; sensitivity: 93 per cent) as well as NTG-POAG pairs (AROC: 0.900; sensitivity: 60 per cent). Inferior outer macular thickness (IOMT) and total volume were the best macular thickness and volume parameters having similar AROCs and sensitivities between normal and POAG (IOMT, AROC: 0.987; sensitivity: 92 per cent and total volume, AROC: 0.997; sensitivity: 97 per cent), normal and NTG (IOMT, AROC: 0.862, sensitivity: 47 per cent and total volume, AROC: 0.898, sensitivity: 67 per cent) and also between NTG and POAG (IOMT, AROC: 0.910, sensitivity: 53 per cent and total volume, AROC: 0.922, sensitivity: 77 per cent). In each comparison group, there was no statistically significant difference in AROCs between average retinal nerve fiber layer and inferior outer macular thickness, as well as total volume. Conclusions The macular parameters offer comparable performance to pRNFL parameters for the discrimination of NTG and POAG. Average retinal nerve fiber layer thickness, total macular volume and inferior outer macular thickness were the best SD-OCT parameters with superior discriminating capabilities.
  • Thumbnail Image
    Item
    Intraeye retinal nerve fiber layer and macular thickness asymmetry measurements for the discrimination of primary open-angle glaucoma and normal tension glaucoma
    (Elsevier, 2016-04) Khanal, Safal; Davey, Pinakin Gunvant; Racette, Lyne; Thapa, Madhu; Department of Ophthalmology, IU School of Medicine
    PURPOSE: The aim of this study was to evaluate the diagnostic capability of intraeye retinal nerve fiber layer (RNFL) thickness and macular thickness (MT) asymmetry measurements for the discrimination of normal tension glaucoma (NTG) and primary open-angle glaucoma (POAG) using spectral domain optical coherence tomography (SD-OCT). METHODS: A total of 90 subjects were enrolled including 30 consecutive healthy subjects, 30 consecutive subjects with POAG, and 30 consecutive subjects with NTG. RNFL thicknesses around the optic disc as well as MT measurements were taken with circular and radial SD-OCT scans. Intraeye retinal and MT asymmetry were calculated as the absolute difference between superior and inferior hemispheres of the eye using posterior pole asymmetry analysis protocol. Analysis of variance was used for comparison and areas under the receiver operating characteristic (AROC) were obtained for different parameters among the three diagnostic groups. RESULTS: There was a significant difference in MT asymmetry for all comparison groups (normal-NTG, p<0.05; normal-POAG, p<0.001; and NTG-POAG, p<0.001). Intraeye retinal nerve fiber thickness asymmetry measurements were not different between the groups (normal-NTG, p<0.187; normal-POAG, p<0.056; and NTG-POAG, p<0.837). The area under ROC curves exceeded 0.800 for all the studied parameters, including the MT asymmetry except for intraeye RNFL thickness asymmetry which had the lowest AROC as well as the least sensitivity for identifying subjects with NTG from normal (AROC=0.626, sensitivity=30%); POAG from normal (AROC=0.644, sensitivity=37%) and NTG from POAG (AROC=0.533, sensitivity=13%). CONCLUSION: The intraeye MT asymmetry holds significant potential as a distinguishing parameter for NTG and POAG.
  • No Thumbnail Available
    Item
    Retinal nerve fiber layer thickness in glaucomatous Nepalese eyes and its relation with visual field sensitivity
    (Elsevier, 2014) Khanal, Safal; Thapa, Madhu; Racette, Lyne; Johnson, Richard; Davey, Pinakin Gunvant; Joshi, Mahesh Raj; Shrestha, Gauri Shankar; Medicine, School of Medicine
    BACKGROUND: To evaluate peripapillary retinal nerve fiber layer (RNFL) thickness in glaucomatous Nepalese eyes using spectral domain optical coherence tomography (SD-OCT) and study its relationship with visual field sensitivity. METHODS: A total of 120 eyes comprising primary open angle glaucoma (POAG), glaucoma suspects (GS), normal tension glaucoma (NTG) and healthy subjects (n=30 cases in each group) underwent a complete ophthalmic examination, including optic nerve head (ONH) evaluation and standard automated perimetry (SAP). RNFL thickness measurements around the optic disk were taken with circular spectral domain optical coherence tomography (SD-OCT) scans. Analysis of variance (ANOVA) was used for comparison of RNFL parameters among various study groups. The relationship of RNFL parameters with visual field (VF) global indices was evaluated with regression analysis. RESULTS: The mean pRNFL thickness was significantly less in the POAG (64.30±14.45μm, p<0.01), NTG (85.43±9.79μm, p<0.001) and GS (102.0±9.37μm, p<0.001) groups than in the healthy group (109.8±8.32μm). The RNFL was significantly thinner across all quadrants in all study group pairs (p<0.05) except for normal vs. GS (only superior and inferior quadrant, significant). Linear regression plots with RNFL thickness as a predictor of MD and LV demonstrated a strong and statistically significant degree of determination in the POAG group (R(2)=0.203 and 0.175, p=0.013 and 0.021). CONCLUSION: The RNFL thickness measurements with SD-OCT are lower in glaucomatous eyes as compared to age-matched GS and normal eyes in the Nepalese population. A high resolution SD-OCT could aid significantly in the early diagnosis of glaucoma in Nepal.