الفهرس 
Review chapterOnly 14 pages are availabe for public view
 |  | from | 91 |  |  |
| | | from | 91 | | |
Abstract
Summary
Glaucoma represents a gaggle of progressive neurodegenerative optic neuropathies characterized by degeneration of retinal ganglion cells (RGC) and their axons and it is the second leading cause of irreversible blindness worldwide.
It has been estimated that at least 25% to 35% of RGCs must be lost before producing significant abnormalities on the VF.
SD-OCT is a noninvasive imaging of detecting glaucoma and glaucomatous structural.
Peripapillary RNFL and the macular region represents the most used OCT parameter However, this method analyzes only the axonal portion of the RGCs without considering the cell bodies and dendrites, which are also affected in glaucoma.
The primary pathology of glaucoma involves the loss of ganglion cells Therefore, RGC loss should theoretically be easiest to detect in the macular region.
Repeatability of any diagnostic test is very important for the accuracy of diagnosis and monitoring changes and disease progression. In the case of glaucoma, it is critical.
The aim of this study was to investigate the repeatability of RNFL and GCC measurements and analysis in normal and glaucomatous patients using SD-OCT (Nidek RS 3000 advance).
This study was a prospective cross-sectional study. A hospital based clinical study carried out in the ophthalmology department at Ain Shams University Hospitals, Cairo, Egypt over six months. Study population was divided into two groups 30 Subjects with healthy eyes (group 1) and 30 Patients with confirmed diagnosis of primary open angle glaucoma (POAG) (group 2).
All subjects in the present study were subjected to full medical history and ocular history. A comprehensive ophthalmic examination (BCVA- Slit lamp examination- IOP- Dilated fundus examination- Optical Coherence Tomography were performed three times for each scan protocol (Optic disc map - Optic disc circle- Macula map)).
The results of the present study showed that:
• As regards, the repeatability of The RNFL Calculation optic disc map in group 1. The ICC values ranged from 0.44 to 0.84. The temporal quadrant showed the lowest repeatability as the within subject COV is high (19.67%) but others are excellent (≤ 10%).
• As regards, the repeatability of The RNFL Calculation optic disc map in group 2. The ICC values ranged of 0.33 to 0.93. The temporal showed the lowest repeatability 0.33. The within subject COV ranged from 7.44% to 19.52%. The highest was the temporal quadrant.
• As regards, the repeatability of the CDR measurements in group 1. The ICC values were 0.86 and 0.81 for horizontal and vertical respectively. The within subject COV were 8.33 and 11.52.
• While the repeatability of the same parameters in group 2 showed ICC value of 0.83 and 0.90 for horizontal and vertical respectively. The within subject COV 11.94% and 9.68% for horizontal and vertical respectively.
• As regards, the repeatability of The RNFL Calculation Circle and TSNIT Plots in group 1. It showed high repeatability for the whole circle, upper hemi field, superior and temporal quadrants with ICC value ranged from 0.76 to 0.96. The inferior quadrant showed the lowest repeatability. All parameters had excellent within subject COV (≤ 10%).
• As regards, the repeatability of The RNFL Calculation Circle and TSNIT Plots in group 2. This study revealed that all parameters showed high repeatability with ICC value ranged from 0.92 to 0.99. The nasal quadrant showed the lowest repeatability, and all had excellent within subject COV (≤ 10%).
• As regards, the repeatability of the GCC thickness in group 1. The upper and lower hemi fields showed moderate repeatability with ICC value of 0.79 and 0.83 respectively. And both had excellent within subject COV (≤ 10%).
• As regards, the repeatability of the GCC thickness in group 2. The ICC values were 0.96 and .84 in upper and lower hemi fields. And both had excellent within subject COV (≤ 10%).
In this study we used (Retina scan RS-3000 advance; NIDEK, Gamagori, Japan). To the best of our knowledge this is the first study to assess the repeatability of this device in glaucomatous patients.
Repeatability of the Nidek RS 3000 was assessed using the ICC as the indicators. The ICC can lie anywhere between 0 and 1. ICC ranges from low to high as follows: (ICC < 0.75: low reliability, 0.75 ≤ ICC ≤ 0.90: moderate reliability and ICC > 0.9: high reliability) and COV was ≤10%, good when COV was between 10–20%, acceptable when COV was between 20–30%, and poor when COV was >30%.
The Nidek RS 3000 demonstrated good repeatability for RNFL thickness measurements obtained from the optic disc circle in addition to the GCC measurements in both normal and glaucomatous patients. The least reliable measures were the nasal and temporal quadrants obtained from the optic disc map. Accordingly, for Nidek OCT users we recommend the use of GCC and optic disc circle for more reliable assessment in glaucoma and glaucoma suspect patients. However, optic disc map should also be obtained for assessment of the optic disc morphological parameters which showed accepted repeatability in this study.