Vision tests on spectacle lenses and contact lenses for optical myopia correction: a pilot study

Abstract

Objective: Visual performance and short-term tolerability of different designs of myopia correcting options, including therapeutically relevant bifocal contact lenses (CL) and spectacle lenses with 'defocus incorporated multiple segments (DIMS)' technology were compared.

Methods and analysis: In myopic volunteering subjects (n=8; spherical equivalent range: -1 to -7 D) visual acuity (VA) using Landolt C and contrast sensitivity (CS) using contrast C were assessed at three different gaze positions (-22° nasal, +22° temporal and 0° central), corresponding to a gaze through the DIMS area or the clear area of the DIMS lens design, respectively, after short-term wear of each of single vision spectacle lenses (SV), DIMS spectacle lenses (DIMS), monofocal soft CL and centre-near multifocal soft CL (MCL). Also, CS was assessed under photopic and mesopic light conditions with and without glare using sinusoidal gratings at 1.5, 3, 6, 12 and 18 cpd.

Results: Mean VA (Landolt C) was -0.12 to -0.10, -0.05 and 0.10 logMAR (SV, DIMS, CL, MCL) at central gaze (0°). At nasal gaze (-22°), VA differed by 0.12, 0.33, 0.05 and 0.01, and at temporal gaze (+22°) by 0.05, 0.26, 0 and -0.08 compared with central gaze values. Mean CS (Contrast C) was 1.74, 1.73, 1.69 and 1.61 logCS (SV, DIMS, CL, MCL) at central gaze at nasal gaze, CS differed by -0.02 to -0.13, -0.01 and -0.01, and at temporal gaze by -0.02 to -0.16, -0.01 and +0.06 compared with central gaze values.

Conclusion: When compared with SV, MCL leads to a general decrease in VA and CS, while DIMS did not differ from SV at straight gaze (0° gaze). With DIMS, VA and CS are decreased to a similar level as with the MCL, but only at nasal and temporal gaze.

Keywords: Contact lens; Optics and Refraction; Treatment other; Vision.

Figure 1

Schematic ray tracing through a myopic eye. Demonstration of ray bundles coming from infinity propagation towards the retina and being refracted by the lenses and the optical media of the eye under two incident angles: 0° (parallel to optical axis) and 22°. Ray tracing was performed using a custom written software routine in Matlab. Parameters were taken from the Lotmar eye model, except for the axial length which was set to 27 mm (=myopic). (A) DIMS, (B) MCL. Zoomed in images show the foci of the ray bundles in the region of the retina. DIMS, Defocus Incorporated Multiple Segments; MCL, multifocal contact lenses.

Figure 2

Schematic drawing of an eye in central (A) and nasal or temporal (B) gaze position. Z’ is the centre of rotation of the eye. Gaze angle α is 22° when the distance from Z’ to the back of the DIMS lens is 25.5 mm and the distance from the centre of the DIMS area to the optical axis of the DIMS lens is 10.5 mm. DIMS, defocus incorporated multiple segments.

Figure 3

Results of VA testing for the three different gaze positions (−22°, 0°, 22°) as measured with single vision lens (SV), spectacle lens with defocus incorporate multiple segments (DIMS), contact lens (CL) and multifocal CL (MCL). The measurements were performed under monocular conditions with the participants left eye occluded. Values for central gaze position are normalised to zero. Error bars represent SD. VA, visual acuity.

Figure 4

Results of CS testing for the three different gaze positions (−22°, 0°, 22°) as measured with single vision lens (SV), spectacle lens with defocus incorporate multiple segments (DIMS), contact lens (CL) and multifocal CL (MCL). The measurements were performed under monocular conditions with the participants left eye occluded. Values for central gaze position are normalised to 0 logCS. Error bars represent SD. CS, contrast sensitivity.

Figure 5

CS measured at 1.5, 3, 6, 12 and 18 cpd with the Optec 6000P. (A) photopic, (B) photopic with glare, (C) mesopic, (D) mesopic with glare (single vision lens (SV), single vision lens with defocus incorporate multiple segments (DIMS), contactlens (CL), multifocal CL (MCL)). CS, contrast sensitivity.