A Review of Periocular Botulinum Neurotoxin on the Tear Film Homeostasis and the Ocular Surface Change

Abstract

Clinical usage of botulinum neurotoxin (BoNT) in ophthalmology has dramatically increased since the 1980s and has become one of the most widely used agents for treating facial movement disorders, autonomic dysfunction and aesthetic wrinkles. Despite its high efficacy, there are some complications with periocular BoNT injections due to its chemodenervation effect. Among these, there is still controversy over the BoNT effect on tear film homeostasis and the ocular surface. A periocular BoNT injection could dry the eye by reducing tear production of the lacrimal gland and increase tear evaporation due to potential eyelid malposition and abnormal blinks. On the contrary, the injection of BoNT in the medial eyelids could treat dry eye disease by impairing lacrimal drainage. Regarding the ocular surface change, corneal astigmatism and high-order aberrations may decrease due to less eyelid tension. In conclusion, the entire awareness of the effect of BoNT and the patients’ ocular condition is crucial for successful and safe results.

Dry Eye Disease in Hemifacial Spasm Patients Treated with Botulinum Toxin Type A

“…Few studies investigating only affected eyes of HFS patients showed that the injection of BTX-A caused decreased tear film stability and decreased Schirmer test, especially in patients received lateral injection sites. 5 , 7 , 14 Mitigating effects including an increase in tear meniscus height, reduction of mean blink output, an increase in lipid tear thickness, and an increased TBUT following BTX-A injection were also observed from the other studies with similar design. 5 , 7 , 12 To the best of our knowledge, only a study by Pellegrini et al had non-affected eye as a comparison and found a significant lower of TBUT at 1 month after injection of BTX-A in affected eye, but no significant change in non-affected eye among HFS patients who received long-term BTX-A injections.…”

“… 5 , 7 , 14 Mitigating effects including an increase in tear meniscus height, reduction of mean blink output, an increase in lipid tear thickness, and an increased TBUT following BTX-A injection were also observed from the other studies with similar design. 5 , 7 , 12 To the best of our knowledge, only a study by Pellegrini et al had non-affected eye as a comparison and found a significant lower of TBUT at 1 month after injection of BTX-A in affected eye, but no significant change in non-affected eye among HFS patients who received long-term BTX-A injections. 11 Our insignificant observations on tear dynamic with a unique design including naïve and long-term BTX-A injection of HFS patients added to the pool of conflicting evidence of the BTX-A effect on tear dynamic.…”

“… 11 Our insignificant observations on tear dynamic with a unique design including naïve and long-term BTX-A injection of HFS patients added to the pool of conflicting evidence of the BTX-A effect on tear dynamic. 5 , 7 , 12 , 14 We suspect that BTX-A may play a role in tear dynamic and present its effects through changes in tear secretion from lacrimal gland, lipid layer thickness, amount of tear on ocular surface, or tear film. The discernable BTX-A effects would depend on BTX-A dosage and concentration, injection technique, injection sites, and size of diffusion area of BTX-A to surrounding tissue.…”

“…1,3,4 Side effects, including ptosis, tearing, dry eye and diplopia have been reported. [3][4][5][6][7] Although the efficacy and side effects of BTX injection for HFS treatment have been well established, the effect of BTX-A on dry eye signs and symptoms is still controversial. 5,[8][9][10][11][12][13][14][15][16][17] Furthermore, there are some studies that investigated the association between dry eye and facial dystonia.…”

Ocular Surface Metrics in Blepharospasm Patients After Treatment With Botulinum Toxin Injections

“…1,[6][7][8] However, the effect of BTX-A injections on the ocular surface remains controversial: while some studies reported improvement, some reported worsening or no change in tear film parameters after BTX-A applications. [8][9][10][11][12][13][14][15][16] In this study, the authors aimed to objectively assess EB patients regarding the effect of botulinum toxin injections on the ocular surface, assessing tear meniscus area with optical coherence tomography. Break-up time (BUT), Schirmer test, and the Ocular Surface Disease Index (OSDI) questionnaire were also evaluated at baseline and after BTX-A injections.…”