The thumb has one long flexor and a short flexor in the thenar muscle group. The human thumb also has other muscles in the thenar group (opponens and abductor brevis muscle), moving the thumb in opposition, making grasping possible. The extensors are located on the back of the forearm and are connected in a more complex way than the flexors to the dorsum of the fingers. The tendons unite with the interosseous and lumbrical muscles to form the extensorhood mechanism. The primary function of the extensors is to straighten out the digits. The thumb has two extensors in the forearm; the tendons of these form the anatomical snuff box. Also, the index finger and the little finger have an extra extensor, used for instance for pointing. The extensors are situated within six separate compartments. The first compartment contains abductor pollicis longus and extensor pollicis brevis. The second compartment contains extensors carpi radialis longus and brevis. The third compartment contains extensor pollicis longus. The extensor digitorum indicis and extensor digitorum communis are within the fourth compartment. Extensor digiti minimi is in the fifth, and extensor carpi ulnaris is in the sixth. The intrinsic muscle groups are the thenar and hypothenar muscles (thenar referring to the thumb, hypothenar to the small finger), the dorsal and palmar interossei muscles (between the metacarpal bones) and the lumbrical muscles. The lumbricals arise from the deep flexor (and are special because they have no bony origin) and insert on the dorsal extensor hood mechanism.
Sudden acquired retinal degeneration syndrome (SARDS) is a disease in dogs causing sudden blindness. It can occur in any breed, but female dogs may be predisposed. Approximately 4000 cases are seen in the United States annually. Characteristics
Symptoms include sudden permanent blindness, but may occur more slowly over several days, weeks or months, dilated pupils. Pupillary light reflexes  are usually reduced but present; the slow phase mediated by melanopsin in retinal ganglion cells is retained. Other symptoms commonly seen are similar to those seen with Cushings disease and include increased water consumption and urination, weight gain, confusion, restlessness, behavioral changes and lethargy. These symptoms may develop over a few months preceding the onset of SARDS. Clinical signs and disease progression vary markedly among individual animals, depending on the number and type of hormones that are increased, the degree of hormone elevation, and the age of the dog.Some owners notice a more obvious "eye shine" in photographs due to the dilated pupils and retinal atrophy creating what is described as a "hyper-reflective tapetum". Causes
The cause of SARDS is considered to be idiopathic and the veterinary community is divided as to its cause, but the most common hypotheses on the causes of the disease possibly include autoimmune disease, or exposure to toxins. Autoimmune disease as a cause is controversial because some studies have supported the presence of antiretinal autoantibodies in dogs with SARDS, but others have failed to show a link.