Does blepharospasm effect biometric parameters and intraocular lens power calculations?

Area of Science:

• Ophthalmology
• Neurology

Background:

• Benign essential blepharospasm (BEB) and hemifacial spasm (HFS) are neurological conditions causing involuntary eyelid contractions.
• Botulinum toxin-A (BTX-A) injections are a common treatment for these conditions, but their effects on ocular parameters are not fully understood.

Purpose of the Study:

• To evaluate the impact of BTX-A treatment on corneal topography, ocular biometry, and keratometry in patients with BEB and HFS.
• To assess changes in intraocular lens (IOL) power calculations following BTX-A injections.

Main Methods:

• A study involving 33 patients with BEB and 5 patients with HFS who received BTX-A injections.
• Measurements of refractive error, tear break-up time (TBUT), corneal topography (K1, K2, Km), and ocular biometry (axial length, anterior chamber depth) were taken before and one month after treatment.
• Expected emmetropic IOL power was calculated using standard formulas (SRK-T, Holladay, Hoffer-Q, Haigis).

Main Results:

• BTX-A treatment led to significant increases in mean corneal power (Km) and anterior chamber depth (ACD).
• Significant decreases were observed in expected emmetropic IOL power calculated by SRK-T, Holladay, and Hoffer-Q formulas.
• Tear break-up time (TBUT) significantly decreased post-injection.

Conclusions:

• BTX-A injections can alter keratometric and ACD values, potentially impacting IOL power calculations.
• The study highlights the need for careful consideration of these changes, suggesting repeated measurements after spasm release for accurate IOL power determination in BEB and HFS patients.