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Botulinum toxin B is a useful treatment for cases that have become refractory to botulinum toxin A. The duration of beneficial effect is shorter than for type A. The side effect profile is similar to that for toxin type A except for pain on injection and the occurrence of dry mouth. Side effects occurred at a higher frequency than with botulinum toxin A, and the pattern suggests that botulinum toxin B spreads more diffusely. Side effects appear to be dosage-related.

The lacrimal drainage system is an intricate mucous membrane-lined conduit, the function of which depends on a complex interplay of anatomy and physiology. Appropriate drainage of tears depends on several factors, including the volume of tear production, eyelid position, normal pump mechanisms, anatomic status of the drainage passages, gravity, and nasal air convection currents. The patient with symptomatic epiphora may have a normal anatomic system overwhelmed by an oversecretion syndrome, or a drainage system that is anatomically compromised and therefore unable to handle normal tear production. Conversely, patients may have partial or complete blockage of the nasolacrimal system but experience no symptoms or have symptoms of dry eye if tear production is signifi cantly reduced. The clinical picture of bothersome epiphora thus depends on the balance of tear production and tear drainage, not on the absolute function of either one.The etiologies of lacrimal drainage dysfunction can be divided into two categories, anatomic and physiologic. Anatomic obstruction refers to a gross structural abnormality of the nasolacrimal system. This can be a complete obstruction, such as punctal occlusion, canalicular blockage, or nasolacrimal duct fi brosis. The causes of partial obstruction include punctal or canalicular stenosis, infl ammatory narrowing of the duct, or mechanical obstruction within the lacrimal sac, such as tumors or stones. Physiologic etiologies result from failure of functional mechanisms despite normal anatomy. These types of dysfunction may result from anatomic deformity, such as punctal eversion or other eyelid malposition, or from lacrimal pump inadequacy from poor orbicularis tone or eyelid laxity.1 Determining the type of dysfunction and the exact location of the anatomic blockage with physical examination and ancillary testing are essential if appropriate therapy is to be offered.The clinical evaluation of gross lacrimal function is usually not diffi cult and the diagnosis of epiphora can oftentimes be made largely on history alone. However, determination of the etiology of epiphora may be more diffi cult and often requires a variety of diagnostic procedures.

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