Apply the_content filter, but prevent other hooked actions

If this is only for certain content areas, create your own filter, and base it off the original the_content filter.

Put this in your functions.php (found in wp-includes/default-filters.php)

add_filter( 'se152488_the_content', 'wptexturize'        );
add_filter( 'se152488_the_content', 'convert_smilies'    );
add_filter( 'se152488_the_content', 'convert_chars'      );
add_filter( 'se152488_the_content', 'wpautop'            );
add_filter( 'se152488_the_content', 'shortcode_unautop'  );
add_filter( 'se152488_the_content', 'prepend_attachment' );

Then use the same filter. Feel free to rename it, but give it a prefix so there are no conflicts.

<?php 
   echo apply_filters('se152488_the_content' , $this->optionVal['custom-message']); 
?>

You have to be either inclusive, or exclusive for this kind of thing, so if there are other filters you WANT from plugins you’ll have to manually add them as well.