正常眼圧緑内障の危険因子として唯一エビデンスが確立されているのは眼圧だけであり,その眼圧の高い値と大きな変動幅が疾患の進行に関与すると言われている.今回筆者らは血圧が正常眼圧緑内障進行の危険因子となりうるか否を検討した.対象は未治療の正常眼圧緑内障患者81例とし各患者の最高眼圧を示す時間帯および,眼圧変動幅を決定した.血圧の検討は収縮期140mmHgあるいは拡張期90mmHg以上を示す患者を高血圧群,収縮期血圧100mmHg以下を示す患者を低血圧群,それ以外の患者を正常血圧群と定義し各群における最高眼圧を示す時間帯,眼圧変動幅を比較した.全81例における平均日内変動幅は4.9mmHgであった.眼圧日内変動測定の結果眼圧が21mmHg以上で開放隅角緑内障と診断名が変更された症例は10例(12%)であった.最高眼圧を示す時間帯では午前型が35例(43.2%),午後型が16例(19.8%),夜型が5例(6.2%),深夜早朝型が21例(25.9%)であった.一方,日内変動幅が3mmHg未満で平坦型と分類されたのは4例(5%)であった.患者血圧群別の分類と眼圧変動幅は低血圧群15例で6.3mmHgと,正常血圧群10例の4.6mmHg,高血圧群56例の4.4mmHgと比較して有意に大きな変動幅を示した.(p<0.05).以上の結果から外来時眼圧が正常眼圧でも,再検で開放隅角緑内障と診断される症例があること,そして低血圧の症例では眼圧変動幅が大きい高いため低血圧が正常眼圧緑内障進行の一つの危険因子になりうると考えられた.Normal tension glaucoma is seen in many cases of glaucoma in Japan. Although this type of glaucoma may cause blindness, the mechanism leading to vision loss has yet to be explained. This disease has no effective treatment or prevention. No evidence exists for other risk factors except for intraocular pressure (IOP). Higher IOP and larger variability of IOP are known to be involved in progression. This study investigated whether blood pressure might be a risk factor for progression of normal tension glaucoma. The subjects were 81 patients with untreated normal tension glaucoma, and diurnal variation of intraocular pressure (IOP) and blood pressure were monitored. As for IOP, the period of time to reach the peak and diurnal variation of IOP were identified. The patients were classified by blood pressure: hypertension group (systolic ≧ 140 mmHg or diastolic ≧ 90 mmHg), hypotension group (systolic ≦ 100 mmHg) and normotension group (not applicable for the above two groups), and the time of the day when peak IOP was reached and diurnal variation of IOP were compared among the three groups. The mean diurnal variation of IOP in the 81 patients was 4.9 mmHg. Ten patients (12%) were diagnosed with open-angle glaucoma, not normal tension glaucoma, because they had IOP of ≧ 21 mmHg. Of 51 patients with a peak IOP in the daytime, 35 patients (43.2%) were morning type (9am - 12noon) and 16 patients (19.8%) were afternoon type (3pm - 6pm). Twenty-six patients had their peak at night: 5 patients (6.2%) were night type (9pm - Oam) and 21 patients (25.9%) were after-midnight to early morning type (3am - 6am) . The remaining 4 patients (5%) were regarded as flat type since their diurnal variations were 3 mmHg or lower. Comparing mean diurnal variations among the three blood pres-sure groups, the hypotension group (6.3 mmHg; n=15) was significantly larger than the normotension group (4.6 mmHg; n=10) and the hypertension group (4.4 mmHg; n=56) (p < 0.05). In conclusion, these results suggest that some patients may be found to have open-angle glaucoma in re-examination even if their IOPs in an outpatient clinic are normal, and that hypotension is potentially a risk factor for progression of normal tension glaucoma because many patients with hypotension show large diurnal variations
