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Intraocular pressure and visual field loss in primary angle closure and primary open angle glaucomas
G Gazzard1, P J Foster, J G Devereux
1Singapore National Eye Centre, (SNEC), 11 Third Hospital Avenue, Singapore 168751, Republic of Singapore. gus@gazzard.demmon.co.uk
The British Journal of Ophthalmology
|May 29, 2003
Summary
Primary angle closure glaucoma (PACG) shows a stronger link between initial eye pressure and vision loss compared to primary open angle glaucoma (POAG). This suggests different damage mechanisms in these glaucoma types.
Area of Science:
- Ophthalmology
- Glaucoma Research
- Optic Nerve Health
Background:
- Glaucoma encompasses various conditions, including primary angle closure glaucoma (PACG) and primary open angle glaucoma (POAG).
- Understanding the relationship between intraocular pressure (IOP) and visual field loss is crucial for managing glaucoma.
- The distinct pathophysiology of PACG and POAG may influence their susceptibility to IOP-related optic nerve damage.
Purpose of the Study:
- To investigate and compare the correlation between pretreatment intraocular pressure (IOP) and visual field loss in patients with PACG and POAG.
- To determine if IOP has a differential impact on optic nerve damage in these two major glaucoma subtypes.
Main Methods:
- A cross-sectional observational study involving 74 patients (43 PACG, 31 POAG).
- Pretreatment IOP was measured at presentation before initiating treatment.
- Visual field loss severity was assessed using AGIS score, mean deviation (MD), pattern standard deviation (PSD), and corrected pattern standard deviation (CPSD). Glaucomatous optic neuropathy was evaluated from stereo disc photographs.
Main Results:
- A stronger correlation between pretreatment IOP and visual field loss was observed in PACG compared to POAG for both MD and AGIS scores.
- Specifically, for MD, the Pearson correlation coefficient (r) was 0.43 (p=0.002) in PACG versus 0.21 (p=0.13) in POAG.
- No significant associations were found for PSD or CPSD in either group. Cup-disc ratio correlated with field loss but not presenting IOP.
Conclusions:
- The findings support the hypothesis that optic nerve damage in PACG is more dependent on IOP than in POAG.
- Conversely, POAG may involve other, less pressure-dependent mechanisms contributing to optic nerve damage.
- These differences highlight distinct pathophysiological pathways in PACG and POAG, impacting treatment strategies.