Snellen fraction
斯涅伦小数(表示视力的数值)

• planetary pinion
• planetary radiation
• planetray microfilmer
• planetray reducer
• plane wave
• plane wave front
• planigraphy
• planimegraph
• planimeter
• planimetry
• planitron
• planizer
• plank
• plano-aspheric corrector
• plano-aspheric transmitting corrector
• plano-concave lens
• plano-convcave
• plano-convex
• plano-convex lens
• plan of site
• planometer
• planopaallel plate
• planoscope eyepiece
• planox
• plant