Abstract
Purpose: :
To evaluate the effect of systemic hypertension and type–2 diabetes on progression of optic nerve damage in patients suspected to have normal tension glaucoma using the confocal scanning laser ophthalmoscope.
Methods: :
200 eyes of 103 patients suspected of having normal tension open angle glaucoma based on large cup–to–disk ratios (>0.5) but with normal intraocular pressures (<22mmHg) and without peripheral visual field defects were included in this retrospective cohort study. Each patient had a follow up period of at least 3 years with a minimum of 2 Heidelberg Retinal Tomogram (HRT) tests (software version 2.01). Exclusion criteria included ocular hypertension, abnormal visual fields or significant confounding ocular pathologies. The effect of diabetes (HbA1C>7%) and hypertension (at least 3 consecutive BP recordings >=140/90 mmHg) on the slopes of the optic nerve head parameters on the HRT with time was studied in these patients using mixed effects regression models (which accommodates clustering of multiple responses from the 2 eyes of the same patient).
Results: :
Patients with systemic hypertension showed a significant increase in cup area (2.46%, p=0.029), cup–to–disk area ratio (1.14%, p=0.007) and cup volume (1.49%, p=0.028) over time. There was a significant decrease in rim area (3.91%, p=0.0279), rim–to–disk area ratio (1.15%, p=0.0052) in these patients with time. The difference in the slopes of cup–to–disk area ratio (p=0.0398) and Retinal Nerve Fiber Layer thickness (p=0.017) with time between hypertensive and non–hypertensive patients was statistically significant. Non–diabetic patients showed a significantly higher rate of progression of the optic cup area (p=0.033), mean cup depth (p=0.044) and height variation contour (p=0.025) with time and a significantly larger decrease in rim–to–disk area ratio (p=0.033) with time, when compared to diabetics.
Conclusions: :
The data indicates that systemic hypertension shows a significant association with increased rate of progression of optic nerve damage in normal tension glaucoma suspects as measured by the HRT. Type–2 diabetics may be less likely to progress when compared to non–diabetics. Prospective studies to further determine these associations are warranted.
Keywords: clinical (human) or epidemiologic studies: risk factor assessment • imaging/image analysis: clinical • optic disc