Can image.php shows only attachment form [gallery]

Hi,
I use native gallery function and a modified version of image.php to enlarge the gallery items. (using image.php instead of fancy or similar grow up my page-views…)

But the problem is that when I use next_image_link() and previous_image_link, image.php load an attachment image on the whole post, not just the [gallery] ids.

this is the code:

<?php 

							      	$image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'full' ); 

								      if ($image) : ?>
								          <img src="<?php echo $image[0]; ?>" alt="" />
								          <br>
								          <br>
								         <?=$att_title = apply_filters( 'the_title' , $attachment->post_excerpt);

									       	echo '<p  style="margin-top:20px;">' . the_excerpt() . '</p>' ; 

								         ?>

								      <?php endif; ?>

							    <!--  </a> -->

							<ul id="gallery-nav" class="clearfix">
								<li class="next pull-left"><?php next_image_link() ?></li>
								<li class="previous pull-right"><?php previous_image_link() ?></li>
							</ul>

Thank you.