Peripheral refraction performance of a myopia control aspheric multifocal contact lens

Abstract

Purpose : Marked asymmetry in peripheral refraction has been noted between the nasal and the temporal visual fields with aspheric lenses used for myopia control. We investigated whether there was an optical explanation for asymmetry in the case of the New Technologies NaturalVue lens (NV).

Methods : Off-eye power profiles of NV lenses were determined by a ClearWave aberrometer, from which 4-zone fits to the aspheric front surface were made. Peripheral refractions of right eyes of 5 participants were determined along the horizontal visual field to ±35° eccentricities, using a Grand-Seiko WAM 5500 Autorefractor (GS) and a COAS-HD aberrometer (COAS). Head movements were used to fixate a series of targets. Refraction was obtained without and with NV lenses. COAS refractions were calculated using 2^nd-order or 2^nd-6^th-order Zernike terms for 2.3 mm, 3 mm and 5 mm pupils. Finally, out-of-the-eye raytracing was done using the Zemax optical design package using the unaided eye’s aberrations and the contact lens, with allowance for lens decentration on the eye.

Results : Fig 1 shows the power profile of a typical lens: there was rapid increase in positive power from centre of 5 D by about 3.0 mm, beyond which power reduced quickly. With GS, there was considerable asymmetry in peripheral power, with more rapid myopic shift into the nasal than into the temporal field, but beyond about 15-20 degrees there was rapid hyperopic shift (Fig 2). There were considerable differences between the refractions obtained with the GS and COAS, with those of the latter depending on pupil size and number of Zernike order, but for most cases and participants the same overall pattern was seen (Fig 2). However, the modelling failed to show the hyperopic shift in the nasal visual field (Fig 2).

Conclusions : Peripheral refraction with the NV aspheric contact lens depends upon the instrument, and for aberrometers upon pupil size and number of aberration orders used in analysis. We were unable to duplicate peripheral refraction in a simulation, indicating that there is at least one unknown optical factor.

This is a 2020 ARVO Annual Meeting abstract.

 

Fig 1: Sagittal power of a NaturalVue lens as a function of radial distance from lens centre

 

Fig 2: Peripheral refraction of a participant as a function of visual field angle with the NaturalVue lens for the Grand-Seiko (GS), COAS with a 2.3 mm pupil, and simulations for a 2.3 mm pupil. COAS and simulated determined using 2nd-order Zernike terms