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F. Berisha, G.T. Feke, C.L. Trempe, J.W. McMeel, C.L. Schepens; Localized Retinal Nerve Fiber Layer Thinning in Patients With Early Glaucoma or Alzheimer`s Disease . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3379.
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© ARVO (1962-2015); The Authors (2016-present)
It has been well established that retinal nerve fiber layer (RNFL) thickness measurements using OCT have implications for the diagnosis and progression of glaucoma. Whether an association exists between the retinal manifestations of glaucoma and Alzheimer’s disease (AD) remains unclear. Conflicting reports have emerged about the RNFL thickness in AD patients. The purpose of this study was to characterize differences in the RNFL thickness between early glaucoma, mild AD patients, and control subjects.
Nine patients with early glaucoma (mean age 70.8 ± 7.4 years), 9 AD patients with mild dementia based on the Mini Mental State Examination (MMSE) score (mean MMSE score 25.3 out of a maximum of 30; mean age 75.8 ± 4.4 years), and 7 age–matched controls (mean age 71.6 ± 2.9 years) were enrolled in this study. RNFL thickness and optic nerve head (ONH) parameters were measured using Stratus OCT. Average and segmental (4 quadrants) RNFL thickness values were compared among the three groups using ANOVA with post hoc tests.
Glaucoma patients showed significantly increased vertical and horizontal cup–to–disc ratios compared with both AD patients and controls (p<0.01). No significant differences in the ONH parameters were found between AD patients and healthy controls. The average RNFL thickness values were 80.7 ± 7.0 µm in glaucoma, 83.2 ± 13.6 µm in AD, and 93.8 ± 9.3 µm in controls. The differences did not reach the level of statistical significance. However, when RNFL thickness was evaluated in the separate quadrants, a significant thinning was found at the superior quadrant in AD patients (90.3 ± 17.7 µm) compared with glaucoma (105.9 ± 10.8 µm, p=0.0264) and control subjects (115.4 ± 11.6 µm, p=0.0016). RNFL thickness at the inferior quadrant in glaucoma patients was significantly reduced compared with both AD patients and controls (p<0.001). None of the other quadrant differences were statistically significant.
In the present study patients with early glaucoma showed optic disc cupping and localized thinning of the inferior RNFL. By contrast, AD patients with a mild severity of dementia were found to have normal cup to disc ratios and localized RNFL thinning in the superior quadrant. These findings indicate that OCT can be useful in distinguishing between early glaucoma and optic neuropathy in patients with mild Alzheimer’s disease. Furthermore, our results may provide important implications for the early diagnosis of Alzheimer’s disease.
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