先天性第3色盲不完全型の一家系

A pedigree with incomplete tritanopia

　我々は先に先天性第3色盲の一家系例を報告したが，今回更に先天性第3色盲不完全型の一家系を経験し，本症の特性をより明らかにすることができたのでここに報告する．

　この家系には発端者（女性）とその父，妹の3名の不完全型第3色盲患者があり，常染色体優性遺伝を認めた．この家系内に視神経疾患をもつ患者は見いだされなかった．

　家系内の第3色盲患者はすべて良い視力をもち，調べえた範囲で眼疾もなく，色覚検査で赤緑色覚異常を伴わない純粋な第3色覚異常所見を示した．

　発端者について，ERG検査ではnormal responseを示したが，黄色背景光下のblueERGはnonrecordableであった．心理物理的検査としてスベクトル比視感度と，Waldの選択色順応法による錐体の分離と二色閾値法（tvi曲線）とTransient Tritanopia Effectの測定を行い，tvi曲線で青錐体系がわずかに機能している以外完全型第3色盲と同じように青錐体系が機能していない結果を得た．

We observed a family with tritanopia affecting three members : a 35-year-old female, her sister aged 33 years and their father aged 66 years. Each of the three cases had normal visual acuity. They manifested pure tritanopic findings and were free of red-green defects when tested with various color vision tests. No pathological fundus findings were observed in the affected and unaffected family members. These findings led to the conclusion that the tritanopia in this family was decidedly hered-itary and was of dominant autosomal nature.

One of the three cases showed normal ERG and non-recordable blue ERG under background illu-mination. Psychophysiological studies made on the proband demonstrated no detectable blue cone response without π component, or Stiles' n mecha-nism. The findings were suggestive of underlying defective functions in the blue cone system following loss of interreceptoral interraction between the blue cone and the longer wavelength sensitive red and blue cones.