ロービジョン外来で処方した拡大鏡の倍率と患者の視機能の検討

Visual function of low-vision patients as related to the magnification of prescribed magnifying glass

要約　目的：低視力者に処方した拡大鏡の倍率と，患者の視力，視野，疾患との関連の報告。

対象と方法：過去7年間に当院のロービジョン外来で，新聞用に拡大鏡を処方した59名を対象とした。男性29名，女性30名で，年齢は55〜93歳，平均77歳である。糖尿病網膜症14名，加齢黄斑変性13名，緑内障8名，強度近視7名，網膜色素変性4名などであり，視機能が良い眼を主として検索した。拡大鏡の倍率は，拡大必要度数（D）を指標とした。

結果：最も強い拡大鏡は，0.1未満の視力不良者が必要とし，平均度数は25.2±7.6Dであった。疾患別では，加齢黄斑変性が最も強い拡大鏡を必要とし，糖尿病網膜症，強度近視，緑内障，網膜色素変性がこれに続いた。中心暗点がある患者は，ない患者よりも強い拡大鏡を必要とした。強い拡大鏡は，視野狭窄が顕著な患者と中心暗点が大きな患者に必要であった。

結論：拡大鏡の度数には，視力と視野が大きく関係した。低視力者ほど度数が大きくなり，視力0.1付近で理論値に近づいた。視野狭窄がある患者では，残存中心視野の大きさと形が拡大鏡の度数に関係した。

Abstract　Purpose：To report the power of magnifier as related to visual acuity, visual field and the disease of patients.

Cases and Method：This retrospective study was made on 59 patients who were prescribed with magnifier in the low-vision clinic of our hospital. The series comprised 29 males and 30 females. The age ranged from 55 to 93 years, average 77 years. There were 14 patients with diabetic retinopathy, 13 with age-related macular degeneration, 8 with glaucoma, 7 with high myopia, and 4 with retinitis pigmentosa among others. Patients were evaluated regarding the better eye as parameter.

Results：Patients with visual acuity of 0.1 or less needed strong magnifier averaging＋25.2±7.6 diopters（D）. Highest magnification was needed by patients with retinitis pigmentosa, followed by those with diabetic retinopathy, high myopia, glaucoma and retinitis pigmentosa in the descending order, Patients with central scotoma needed higher magnification than those without. High magnification was required by patients with narrow visual field and those with central scotoma.

Conclusion：Power of magnifier was closely related with visual acuity and field. Patients with lower visual acuity needed higher magnification. Visual acuity of 0.1 approximated the theoretical value. In patients with visual field constriction, power of magnification was related to the size and shape of residual visual field.