カラーマッピング法による円錐角膜の形状解析

Corneal topography of keratocornea by computerassisted color mapping method

　円錐角膜の形状解析を目的に，円錐角膜患者65例115眼についてコンピュータを用いて角膜曲率のカラーマッピングを試みた。角膜曲率の算出には，コニコイド曲線を利用した。円錐角膜では早期から角膜曲率分布が非対称となり，次第に突出していくことが視認された。さらに，非対称度と突出度の2つのパラメータを定めて解析を行い，正常眼47眼と早期円錐角膜42眼の間には，非対称度，突出度ともに有意差が認められ（p＜0.001），これら2つのパラメータが円錐角膜の早期診断に有用と思われた。

We evaluated the shape of the cornea in 115 eyes with keratoconus in 65 patients. We used a computer-assisted color mapping method in the evaluation. An asphericity equation was applied to express the refractive power of the cornea as a conicoid curve. The distribution of corneal refrac-tion showed asymmetry to the center from earlystage on. The difference between the central and peripheral refractive power increased along with the progression of the stage of keratoconus. We then compared 47 normal eyes with 42 eyes with early-stage keratoconus by using corneal asym-metry and protrusion as parameters. Both parame-ters were significantly greater in eyes with ker-atoconus than in normal eyes (p＜0.001). These findings suggest the usefulness of these two para-meters in the detection of corneal irregularity in early-stage keratoconus.