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A. Aoyama, K. Ishida, T. Yamamoto; Target Pressure Determined in Progressive Normal-Tension Glaucoma Cases. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1265.
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To determine a target IOP level in progressive normal-tension glaucoma (NTG) by evaluating visual field (VF) progression following trabeculectomy.
All consecutive cases (164 eyes of 115 patients) with NTG who underwent trabeculectomy with mitomycin C between 1990 and 2000, were retrospectively reviewed and 40 eyes of 40 patients who had significant progression of VF preoperatively, were selected based on the following criteria: best-corrected visual acuity >20/30, preoperative mean deviation (MD) >-20.00 dB, no eye diseases except NTG or postoperative complications which may affect VF, and postoperative follow-up period > 5 years (mean 12 years, range; 5.3-16.0 yrs). Perimetric examination was periodically performed and progression was determined by two criteria: AGIS score deteriorated at least four, and significant negative MD slope by a linear regression model. Kaplan-Meier method was used to compare the VF stability in different IOP levels. Preoperative mean MD was -13.38dB.
The IOP was reduced from 15.2 to 9.4 mmHg in average by trabeculectomy (p<.0001). IOP≤10 was attained in 60% of cases. 30% and 20% reduction of IOP were achieved in 23 (58%) and 29 (73%) of 40 patients, respectively. Cumulative probability of postoperative VF stability defined by the AGIS criterion was 96 % at 14 year-F/U in patients who achieved 30% reduction of IOP, whereas it was 32 % in ones who did not (p<.0001: Logrank test). When 20% IOP reduction was employed as a cut-off value, VF was maintained in 93% in the successfully controlled group, but all cases who failed showed progression (p<.0001). When IOP values such as 8, 9, 10, 11, 12 mmHg were employed as a cut-off, the best VF prognosis was attained by both progression criteria in cases with the postoperative IOP value of 10 mmHg. However, 8 % of patients with postoperative IOP≤10 mmHg and/or achieved 30% reduction of IOP still had VF progression.
At least 20% reduction of IOP or IOP≤10 mmHg is required as postoperative target IOP in NTG patients who had significant progression of VF preoperatively.
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