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Contrast sensitivity (CS) testing may prove to be a better measure of vision in patients fit with multifocal contacts for myopia control than standard visual acuity testing, according to research published in Optometry and Vision Science. When compared with a single vision contact lens (SVCL), multifocal contacts (MFCL) can reduce distance contrast sensitivity in both mesopic and photopic conditions, according to the report. However, the investigators did not note any difference between SVCL and MFCLs in near contrast sensitivity testing.
Researchers used data from 25 patients with myopia (72% women, mean age 24.1±1.5 years), whose refractive error after vertexing was between -0.75 D and -6.00 D sphere and astigmatism equal or less than a 1.00 D in each eye. Patients were fitted with 3 contact lenses binocularly: Biofinity single vision (CooperVision), Biofinity Multifocal D (CooperVision) +2.50 add, and NaturalVue Multifocal (Visioneering Technologies, Inc.).
All lenses fitted in the study had an acceptable fit with adequate paralimbal coverage and slight temporal decentration, according to the study authors. Those with active anterior segment disease or pathology that affected vision or lens wear, history of trauma or surgery or RGP wearers were excluded from the study.
Contrast sensitivity was measured at both 4 meters in mesopic and photopic conditions and 40 cm in photopic conditions. Log CS by spatial frequency and area under the log contrast sensitivity function (AULCSF) was analyzed between the contact lenses. Distance contrast sensitivity was measured at 1.3, 3, 6, 12 and 18 cycles per degree (cpd) and near spatial frequencies ranged from 0.1 to 22 cpd.
Researchers report that the distance photopic CS at each spatial frequency was higher with the SVCL then the MFCLs (P <.001) but there was no difference between the 2 brands of MFCLs (P =.71). The distance mesopic CS, from 1.5 to 12 cpd was higher with the SVCL than the MFCL (all P <.2). At 18 cpd, there was no difference in CS between the NaturalVue MF and the SVCL (P =.76). Investigators hypothesized this may be due to spurious resolution. Under photopic conditions, the AULCSF for the SVCL was approximately 10% greater than both brands of MFCLs.
At near, contrast sensitivity was similar between lenses, but slightly lower with the NaturalVue at both 11 and 15.5 cpd. AULCSF was similar between all lenses (P >.05).
As many children are prescribed center-distance multifocal contact lenses for myopia control, it is important for doctors to “be aware of the lens design they prescribe” and consider the effect on the child’s vision. Contrast sensitivity function assesses sensitivity to both size and contrast of the target and may offer a more comprehensive measure of vision in the real-world than visual acuity testing alone.
The only limitation to the study is that contrast sensitivity was not measured beyond the day of the initial lens fitting. It is unknown whether patient adaptation in time may affect CS function.
Reference
Nti AN, Gregory HR, Ritchey ER, Wolffsohn JS, Berntsen DA. Contrast sensitivity with center-distance multifocal soft contact lenses. Optom Vis Sci. 2022;99(4):342-349. doi:10.1097/OPX.0000000000001874
