MySQL Query takes too long to execute - mysql

Question

I have a table
CREATE TABLE tb_incident (
id int(10) unsigned NOT NULL AUTO_INCREMENT,
what tinyint(4) NOT NULL,
when bigint(20) unsigned NOT NULL,
where tinytext NOT NULL,
where_longitude_latitude point NOT NULL,
who tinyint(4) DEFAULT NULL,
why tinyint(4) DEFAULT NULL,
description text,
created timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
PRIMARY KEY (id),
UNIQUE KEY id_UNIQUE (id),
KEY index_main_items (what,when),
SPATIAL KEY location_index (where_longitude_latitude)
) ENGINE=MyISAM AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;
When I try running this query,
SELECT db_incident.distance(point(132.6,15.604436765987833),where_longitude_latitude,'mi') AS "Distance in miles",
X(where_longitude_latitude) AS "Longitude",
Y(where_longitude_latitude) AS "Latitude"
FROM db_incident.tb_incident
WHERE db_incident.distance(point(132.6,15.604436765987833),where_longitude_latitude,'mi') <= 5
LIMIT 100
It takes over 10 minutes to execute, sometimes it gives this error Error Code: 2013. Lost connection to MySQL server during query
My table has over 10 million records. Can someone please take a look and see if there is a way the query can be optimized.
NOTE: db_incident.distance is a function that returns the distance between two points.
Below is the EXPLAIN of the query.
+----+-------------+-------------+------+---------------+------+---------+------+----------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+-------------+------+---------------+------+---------+------+----------+-------------+
| 1 | SIMPLE | tb_incident | ALL | NULL | NULL | NULL | NULL | 11689629 | Using where |
+----+-------------+-------------+------+---------------+------+---------+------+----------+-------------+
1 row in set (0.00 sec)