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K. Ahrlich, C. G. V. De Moraes, T. S. Prata, F. A. Folgar, H. C. Beck, C. C. Teng, C. Tello, R. Ritch, J. M. Liebmann; Comparison of Progression Rates Between Normal-Tension and High Tension Glaucoma Patients. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2230.
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It remains unclear whether both pressure- and non-pressure-dependent mechanisms result in the same pattern of glaucomatous visual field (VF) loss. We examined the location and rates of VF loss between normal tension (NTG) and high tension (HTG) glaucoma patients. Exfoliation eyes were utilized as HTG to maximize the differences with the NTG group.
We reviewed records of all glaucoma patients (glaucomatous optic neuropathy + VF defects) with ≥10 SITA-Standard 24-2 VFs from 1999 to 2008. Patients were divided into NTG (all known untreated IOPs <21 mmHg) or HTG (exfoliative glaucoma with untreated IOP >21 mmHg) groups. Exclusion criteria were any conditions other than glaucoma likely to affect the VF. Pointwise linear regression analysis (Progressor®) was used to determine the rate of VF progression. We compared the location and mean rate of VF loss between groups.
74 NTG (mean MD: -6.2±4.1) and 67 HTG (mean MD: -5.1±5.5 dB) eyes (p=0.15) were included. Mean NTG and HTG group ages were 72.6±10.1 and 76.8±8.1 yrs, respectively (p=0.06). Central VF loss (at least 1 point with p<1% within the central 16 points on the 24-2 VF) occurred more frequently in NTG (85%) than HTG (53.7%) eyes (p<0.01). During a similar mean follow-up period (9.2±3.2 and 9.7±4.3 yrs, respectively, p=0.5), global rates of progression were similar between NTG (0.48±0.6 dB/year) and HTG (0.63±0.6 dB/year) eyes (p=0.16), even after adjusting for baseline MD and age (general linear model, p>0.05). Progression of central points was slightly faster in NTG eyes (2.35± 1.4 vs 1.9±1.0 dB/yr, p=0.2). Progression in NTG eyes tended to occur at the outer edge of the central field (73%), whereas in the HTG eyes it progressed centripetally from regions of more peripheral damage (58%). (p<0.01)
NTG eyes tended to show a slightly faster progression rate in the central field, but rates of global VF loss are similar between treated NTG and HTG patients. NTG eyes are at increased risk of field loss close to fixation, which may require more aggressive treatment.
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