We need to translate visible text content, preserving HTML tags exactly. No extra text. Must output only translation. So we need to translate each visible text segment, including punctuation, keep tags. Also preserve attributes like class, href. Let's go through paragraph by paragraph. Original:

If you have 20/20 vision, you can clearly see an object 20 feet away. This refers to average, normal vision. If your vision does not measure 20/20, you may need to wear contact lenses or glasses to see clearly. But do you know who has a visual acuity 20 times better than the average human? 

Translate to Japanese. Something like:

もし視力が20/20であれば、20フィート離れた物体をはっきりと見ることができます。これは平均的な正常視力を指します。視力が20/20でない場合は、コンタクトレンズや眼鏡を装着してはっきり見る必要があるかもしれません。しかし、平均的な人間の20倍の視力を持つ人がいることをご存知ですか？ 

Make sure to keep