Same question with 靉. I know together they make a literary translation of 'dark' in the context of clouds.
As a native speaker, I have to admit that this is the first time that I see these two characters.
By the help of dictionaries, I found that together 靉靆 means very cloudy so that it's dark. A new meaning appeared in the Ming Dynasty to mean glasses.
靉靆 is a 叠韵连绵词. Not sure how to translate the term, but it means a word that is made of two characters (syllables) which have the same vowel; it has only one morpheme. That is each character alone cannot be used to express a meaning; they have to be used together.
康熙字典: 《玉篇》靆: 不明貌。《正韻》𠀤蕩亥切，音駘。義同。
I can't explain/translate the sentence though :)