There is a pattern here. subject + to be + adjective relating to personal reaction + infinitive (to+base verb) Other examples of reaction adjectives: sorry, disappointed, delighted, devastated, happy, sad, overjoyed. e.g. I was overjoyed to see the result of West Ham's first league game in their new stadium.

Some verbs only take infinitives (to see), some only take gerunds (seeing), and some can take either. This link will help you: http://www.really-learn-english.com/gerunds-and-infinitives.html

Like Melissa, I would say "I was was glad to see Tom" and never "I was glad seeing Tom". But when it comes to saying "It was great to see Tom", one will also hear, quite commonly, "It was great seeing Tom".

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It is correct to say "I was very glad to see..." For example: I was very glad to see that you were accepted into medical school.