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A molded soft toric contact lens (STCL) is a workable option that provides good vision in corneal ectasia cases that have moderate irregularity and negative vertical coma, according to a study in Contact Lens & Anterior Eye.
The study looked at 22 eyes fitted with a molded STCL, 11 eyes of 9 patients with corneal ectasia and 11 eyes of 11 patients that were healthy participants. Investigators analyzed wavefront aberrations and measured visual performance under photopic (85 cd/m 2) and mesopic (≤3 cd/m 2) conditions. They also assessed high-(96 %) and low- (10 %) contrast VA (HCVA and LCVA, respectively) with the Early Treatment Diabetic Retinopathy Study (ETDRS) chart and contrast sensitivity (CS) using the Pelli-Robson chart.
They found that following STCL placement in the ectatic corneas, the oblique astigmatism increased 0.15±0.17 μm and 0.34±0.36 μm for 3 mm and mesopic pupil diameters, respectively.
The mean defocus decreased 1.41±0.36 μm and 2.17±0.85 μm for the same pupil diameters. And more positive values of vertical coma occurred with a change of 0.05±0.06 μm and 0.12±0.10 μm for 3 mm and mesopic pupil diameters, respectively.
“Comparing changes between both groups, with a 3 mm pupil aperture, statistically significant differences (P <.05) were detected in oblique astigmatism, defocus, vertical secondary trefoil and horizontal secondary coma,” according to investigators. “In the group with corneal ectasia, photopic HCVA and LCVA improved 0.09±0.11 logMAR and 0.12±0.15 logMAR respectively. In mesopic conditions, HCVA, LCVA and CS improved 0.11±0.12 logMAR, 0.18±0.15 logMAR and 0.11±0.07 log. units, respectively.”
The study’s limitations include its small sample size. Also, researchers did not examine corneal surface interactions between low and high order aberrations, long-term neural adaptation, and the use of different materials and designs of STCL.
Reference
Carballo-Alvarez J, Mari-Ribas M, Martin-Gonzalez A, Batres L. Is soft toric contact lenses fitting a feasible option to improve optical quality and visual performance in corneal ectasia? Cont Lens Anterior Eye. Published online March 11, 2021. doi:10.1016/j.clae.2021.03.001.
