Calling custom fields for next/previous posts

With that said, I’d like to say I am using this snippet for a new theme I am building.

I want to pull a custom field from the “next” & “previous” post. So I used the following to do so:

<?php
  $previous_post = get_previous_post();
  $next_post = get_next_post();
  $image_prev = get_post_meta( $previous_post->ID, 'image', $single = true);
  $image_next = get_post_meta( $next_post->ID, 'image', $single = true);
?>

Simple. This is how I put it to use:

<?php if ( $image_prev != '' ) : ?>

  <img src="<?php echo FROSTY_SCRIPTS  ?>/thumb.php?src=<?php echo $image_prev; ?>&amp;h=50&amp;w=169&amp;zc=1&amp;q=80" alt="" />

<?php endif; ?>