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Editors Selection IGR 21-4

Examination methods: VF changes after IOP elevations

Comment by Louis Pasquale & Aliya Jewani on:

20954 Visual field changes after transient elevation of intraocular pressure in eyes with and without glaucoma, Chan KC; Poostchi A; Wong T et al., Ophthalmology, 2008; 115: 667-672

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Chan et al. (618) examined whether patients with and without glaucoma developed visual field changes after transient elevations of intraocular pressures (IOP). The authors examined visual field changes in 38 glaucomatous and 62 non-glaucomatous eyes after increasing the IOP, with a modified LASIK suction ring, to an average of 64 mmHg for less than 30 seconds. The authors found that Humphrey Matrix perimetry did not reveal short term functional optic nerve damage for most patients. However, six glaucoma eyes did show a decline in mean deviation in short-term follow-up perimetry tests while only three control eyes did so (P = 0.046). While this result is inconclusive, it is possible that some patients with documented optic neuropathy may be more vulnerable to optic nerve damage after transient IOP increase than those without documented optic neuropathy.

In this case control analysis, subjects with various types of glaucoma were included as cases and thus we don't know if subsets of glaucoma patients are more susceptible to the effects of IOP elevation than others are. Sixty percent of controls were glaucoma suspects, and it is possible that some of them had early signs of glaucoma based on their baseline pattern standard deviation values. However, every patient did serve as their own control and few patients manifested progression. Finally, the average IOP elevation induced in this study is considerably less than the IOP increase created during LASIK, which is certainly understandable given patient safety concerns. More work is needed to address the safety of LASIK in glaucoma patients.

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