Akhtar Ali, Ahmad Nurfahmi
(2014)
The correlation between visual electrophysiology test with retinal nerve fibre layer thickness and advance glaucoma interventional study score in primary angle closure
glaucoma patient.
Masters thesis, Universiti Sains Malaysia.
Abstract
INTRODUCTION
Primary angle closure glaucoma (PACG) causes more blindness in Asian population.
Diagnosis and monitoring remains a challenge especially due to structural-functional
discrepancy in evaluating optic nerve head (ONH) in PACG. Visual electrophysiology
(pattern electroretinogram (PERG) and pattern visual evoked potential (PVEP)) has the
capability in detecting functional impairment of retina ganglion cells (RGC). It has the
potential as complimentary test to the existing standard structural and functional test for ONH
evaluation in glaucoma in general and PACG specifically.
OBJECTIVE
To evaluate visual electrophysiology response and retina nerve fibers layer (RNFL) thickness
in PACG. The correlation between visual electrophysiology with the glaucoma severity based
on RNFL thickness and Advance Glaucoma Interventional Study (AGIS) score were also
evaluated.
MATERIALS AND METHODS
A comparative cross sectional study was conducted in Hospital University Sains Malaysia
involving 66 samples of PACG patients and controls. A Complete ocular assessment was
done to confirm the diagnosis of PACG. Evaluation of structural changes of RNFL of ONH
was conducted using Cirrus SD-OCT (Carl Zeiss Meditec Inc, USA) with good signal
strength ( ≥ 6/10).AGIS score was performed on a reliable reproducible visual field of two
consecutive Humphrey’s visual field (24-2) analysis. PERG (0.8º checks size) and PVEP(0.25º checks size) was conducted by a trained technician. Independent t-test, ANCOVA and
Pearson’s correlation coefficient analysis were used in analysis.
RESULTS
There was statistically significant reduction in amplitude and latency in of PERG in PACG
patients (p<0.001). There was also significant reduction in magnitude of amplitude (p<0.001)
and shorten of P100 latency in PVEP (p<0.001). PACG patients had significant smaller disc
area (2.03±0.26) compared to controls (2.27±0.35). There was also significant thinner RNFL
analysis in all quadrant of the ONH in PACG patients (p<0.001). RNFL thickness shown a
significant strong positive correlation with the PERG amplitude of N95 (r = 0.54, p = 0.001).
AGIS score showed a significant negative correlation between N35 (r = - 0.36, p = 0.041) and
N95 (r = - 0.49, p = 0.003) of PERG. Similarly the positive and negative correlations were
seen between RNFL thickness and AGIS score respectively with PVEP. However it was not
statistically significant.
CONCLUSION
Visual electrophysiology showed significant changes in PACG patients. There was
significant correlation between PERG and existing standard structural and functional analysis
of ONH. PERG is the potential alternative tools for evaluation of functional changes of ONH
in PACG patients.
KEY WORDS
‘Primary angle closure glaucoma (PACG)’, pattern electroretinogram (PERG), pattern
visual evoked potential (PVEP), retina nerve fiber layer (RNFL), Advance Glaucoma
International Study (AGIS).
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