Diurnal variation of intraocular pressure in normal-tension glaucoma

PURPOSE: Measurement of diurnal variation of intraocular pressure(IOP) is important for precise diagnosis of normal-tension glaucoma(NTG). We studied diurnal variation of IOP of NTG using a self-measuring tonometer. METHODS: A total of 159 patients(318 eyes) who were diagnosed as having NTG in Osaka Koseinenkin Hospital between 1994 and 2002 measured their own diurnal variation of IOP at home every 3 hours (8 times a day) using a prototype self-measuring non-contact air-puff tonometer(Hometonometer). RESULTS: The maximum IOP, the minimum IOP, and the range of diurnal variation of IOP were 16.8 +/- 2.0 mmHg(mean +/- standard deviation), 12.8 +/- 1.7 mmHg, and 4.0 +/- 1.3 mmHg, respectively. Maximum IOP occurred most frequently at noon(24.3%), 9:00 am(21.4%), and 6:00 am(17.4%). In 69.2% of eyes, maximum IOP was found during outpatient clinic hours(9:00 am to 6:00 pm). Minimum IOP occurred most frequently at midnight(34.1%), 3:00 am(22.8%), and 9:00 pm(17.8%). CONCLUSIONS: Approximately 30% of NTG patients have maximum IOP outside of outpatient clinic hours, and therefore measuring IOP in the early morning is important for determining the precise diurnal variation of their IOP. We hope that a safe self-measuring tonometer with which patients can measure their own IOP will be come commercially available soon, so that we can provide them with more individualized glaucoma treatment using the appropriate combination of medicines.