Patients with hemifacial spasm likely have corneal changes as a result of their condition, which clinicians should take into account before cataract and refractive surgeries and contact lens fittings, a study in Eye Contact Lens reports.

Turkish researchers sought to determine whether corneal topographic parameter values, individual corneal layer thicknesses and its endothelial layer morphology were different in patients with hemifacial spasm than in the control fellow eye.

The prospective study included 28 patients treated within the past three years who had hemifacial spasm in one eye (the study eye) and a normal contralateral eye (controls). In addition to a complete ophthalmologic exam, researchers scanned all patients with a Scheimpflug camera and conducted a corneal endothelial cell count with specular microscopy. They also used optical coherence tomography to measure the thickness of the central cornea’s sublayers.

Investigators reported steep K, Kmax and astigmatism values were significantly higher in study eyes of patients with hemifacial spasm than the control group. “In our opinion, a probable reason for this increase in these parameters is the increased and altered pressure on the cornea of the eyelid,” investigators wrote in their paper.

In addition, the total corneal and stromal thickness measurements in the study eyes were statistically and significantly thinner than the control eyes. However, endothelial cell count differences were not statistically significant between the study and control eyes, researchers noted.

Stromal thinning suggests that chronic exposure to hypoxia may induce this effect through extracellular matrix remodeling and losses in collagen framework content in patients with hemifacial spasm, the investigators said.

They added: “We believed that corneal thickness reduction is mainly caused by

chronic hypoxia–associated keratocyte loss because of reduction in oxygenation of the ocular surface. In our opinion, the endothelial morphology is not affected because the corneal endothelium is nourished from the aqueous humour.”

Since the study suggests the anterior corneal surface is affected in patients with hemifacial spasm, keratometric changes in these patients should be considered in intraocular lens power calculations before cataract surgery, researchers suggested. It’s also a factor before contact lens wear and refractive surgeries, the researchers noted. “Also, the presence of irreversible corneal changes in patients with hemifacial spasms shows that early treatment is important,” they wrote.

Ulusoy DM, Ulusoy EK, Duru Z, et al. Evaluation of corneal morphology in patients with hemifacial spasm. Eye Contact Lens. March 29, 2019. [Epub ahead of print].