A lesion in this area would involve efferent pupillary fibres on the dorsal aspect of the Edinger-Westphal nucleus (associated with the response to light) while sparing the fibres associated with the response to near, which lie slightly more ventrally. The exact relationship between syphilis and the two types of pupils (AR pupils and tonic pupils) is not known at the present time. The older literature on AR pupils did not report the details of pupillary constriction (brisk vs. tonic) that are necessary to distinguish AR pupils from tonic pupils. Tonic pupils can occur in neurosyphilis. It is not known whether neurosyphilis itself (infection by Treponema pallidum) can cause tonic pupils, or whether tonic pupils in syphilis simply reflect a coexisting peripheral neuropathy. Thompson and Kardon summarize the present view:

The evidence supports a midbrain cause of the AR pupil, provided one follows Loewenfeld’s definition of the AR pupil as small pupils that react very poorly to light and yet seem to retain a normal pupillary near response that is definitely not tonic.To settle the question of whether the AR pupil is of central or peripheral origin, it will be necessary to perform iris transillumination (or a magnified slit-lamp examination) in a substantial  number of patients who have a pupillary light-near dissociation (with and without tonicity of the near reaction), perhaps in many parts of the world. Parinaud syndrome
A third cause of light-near dissociation is Parinaud syndrome, also called dorsal midbrain syndrome.
Examples of potential allergens include substances that may be present in some types of lipstick, toothpaste, acne products, cosmetics, chewing gum, mouthwash, foods, dental appliances, and materials from dentures or mercury containing amalgam fillings. It is usually impossible to tell the difference between irritant contact dermatitis and allergic contact dermatitis without a patch test. Loss of lower facial height
Severe tooth wear or ill fitting dentures may cause wrinkling at the corners of the lip that creates a favorable environment for the condition. This can be corrected with onlays or crowns on the worn teeth to restore height or new dentures with "taller" teeth. The loss of vertical dimension has been associated with angular cheilitis in older individuals with an increase in facial laxity. Diagnosis
Angular cheilitis is normally a diagnosis made clinically. If the sore is unilateral, rather than bilateral, this suggests a local factor (e.g., trauma) or a split syphilitic papule. Angular cheilitis caused by mandibular overclosure, drooling, and other irritants is usually bilateral.The lesions are normally swabbed to detect if Candida or pathogenic bacterial species may be present. Persons with angular cheilitis who wear dentures often also will have their denture swabbed in addition. A complete blood count (full blood count) may be indicated, including assessment of the levels of iron, ferritin, vitamin B12 (and possibly other B vitamins), and folate. Classification
Angular cheilitis could be considered to be a type of cheilitis or stomatitis.