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Editors Selection IGR 7-1

Medical treatment: 24-hrs IOP-control in NTG

Comment by Anastasios Konstas on:

18117 Effect of concomitant use of latanoprost and brinzolamide on 24-hour variation of IOP in normal-tension glaucoma, Nakamoto K; Yasuda N, Journal of Glaucoma, 2007; 16: 352-357

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There are little published data available on 24-hour IOP control obtained with adjunctive medical therapy in normal-tension glaucoma (NTG). Nakamoto et al. (713) have studied 24-hour IOP control obtained with latanoprost and brinzolamide specifically in patients with NTG. In an attempt to elucidate the efficacy of adding brinzolamide to latatoprost the authors carried out an investigation in 22 patients with bilateral NTG (44 eyes) who had their diagnosis confirmed with an untreated 24-hour curve where the peak IOP had to be below 21 mmHg at all timepoints measured (IOP was measured every 3 hours throughout the 24-hour period). All IOP measurements were performed in the sitting position using Goldmann applanation tonometer. In this group of NTG patients the highest untreated IOP was recorded at 10:00 in the morning (15.5 ± 2.1 mmHg) and the lowest IOP value was detected at 03:00 at night (12.7 ± 2.0). The mean untreated 24-hour IOP (13.8 ± 1.5 mmHg) was reduced by 14% to 11.9 ± 2.0 mmHg with latanoprost monotherapy. Following latanoprost monotherapy the peak IOP was still detected at 10:00 (13.1 ± 2.6 mmHg). Then one eye, chosen at random, was treated with the combination of latanoprost and brinzolamide and another 24-hour curve was performed. Combined therapy obtained an additional IOP reduction of 5.7% for daytime IOP and 3.4% for nocturnal IOP. The mean 24-hour IOP was 11.3 ± 1.7 mmHg. This new 24-hour study confirms the findings of several previously published 24-hour studies which generally find the IOP in only the sitting position to be higher in the morning and lower during the night. However, all these studies only monitor sitting IOP. It would appear from the findings of this study that latanoprost significantly reduces 24-hour IOP in NTG, but less so than in open-angle glaucoma with higher baseline pressures. With combined therapy IOP reduction was more pronounced during the daytime than at night. Indeed, during the nocturnal period additional IOP reduction provided by brinzolamide was small and not statistically significant compared with latanoprost monotherapy. Presumably this is due to the relatively low baseline IOP in NTG and the lower IOP recorded during the night.

A number of authors have argued that reducing 24-hour IOP fluctuation may be beneficial in the long-term management of glaucoma. Unfortunately and despite the title of the article the authors do not discuss this topic. Interestingly, the addition of brinzolamide to latanoprost further reduced 24-hour IOP fluctuation from 4.0 ±

1.7 mmHg to 2.7 ± 1.6 mmHg. This represents a staggering 33% reduction in 24-hour IOP fluctuation. If in some NTG patients progression occurs as a consequence of wide 24-hour IOP fluctuation this adjunctive regime appears capable of positively influencing this parameter. This 24-hour IOP study confirms the clinical utility of brinzolamide as adjunctive therapy in NTG patients treated with latanoprost. It is possible that the combination of a prostaglandin analogue and a topical carbonic anhydrase inhibitor is particularly advantageous in some glaucoma patients. This study helps in establishing a better understanding in how adjunctive therapy works in NTG. Much remains to be elucidated in this important area.

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