Trefoil and secondary astigmatism of higher-order aberration are introduced as the subject of the last in this series. It is reported that monocular triplopia and monocular diplopia are due to trefoil with spherical aberration and secondary astigmatism with spherical aberration, respectively. Here, the relation between these aberrations and defocus is shown using simulated retinal images. Also shown is that a special combination of trefoil and coma aberration is related to apparent accommodation.

Monocular diplopia or monocular triplopia is occasionally complained in young patients with cataract. Because the scattering in the lens is slight, higher-order aberration originating from the inhomogeneous refractive index in the lens may influence the retinal image. Monocular diplopia is explained by the combination of secondary astigmatism and spherical aberration, monocular triplopia by trefoil and spherical aberration. Cataract surgery is recommended if the subjective diplopia or triplopia is similar to the simulated retinal images and the corneal higher-order aberration is slight.

Full-field optical coherence tomography (FF-OCT) is a non-scanning horizontal cross-sectional imaging technique based on low-coherence interference microscopy. Use of a spatially incoherent broadband light source incorporating relatively high-NA (numerical aperture) objectives enables FF-OCT imaging with both ultrahigh axial and lateral resolutions. This paper gives a brief history of FF-OCT development and presents some of the ultrahigh resolution FF-OCT results for ex-vivo ophthalmologic tissues.

Purpose: Anterior chamber measuring instruments employing various principles are available today. In this study, we measured central corneal thickness (CCT) and anterior chamber depth (ACD) in normal volunteers, using a recently developed optical measuring system: anterior chamber optical coherence tomography, Visante^TM (Carl Zeiss Meditec). We then considered its measurement accuracy.

Methods: We measured 24 eyes of 12 subjects (mean age: 31.0±4.3 (23–37) years) with no ocular diseases, but with refractive errors, using Visante^TM and Orbscan^®IIz (Bausch&Lomb). Each subject eye was measured five times with the two devices; CCT and ACD data were then compared.

Results: CCT was 524.6±1.9 μm and ACD was 3.625±0.02 mm, as measured by Visante^TM. In contrast, CCT was 553.5±5.3 μm and ACD was 3.562±0.03 mm, as measured by Orbscan^®IIz. This study confirmed high correlation and significant difference between the two devices.

Conclusions: The observed data confirmed correlation between Visante^TM and Orbscan^®IIz; which fact suggests that Visante^TM will be useful in biometric studies of the anterior chamber.

Purpose: To measure contrast visual acuity in contact lens (CL) users.

Methods: Contrast visual acuity was measured in 15 normal subjects, ranging in age from 25 to 40 years (mean: 28.0 years) and 85 CL users, aged 15 to 51 years (mean: 24.8 years). Of the subjects, 16 used daily disposable soft CL (SCL), 23 used 2-week frequent replacement SCL, 24 used conventional SCL and 22 used rigid gas-permeable (RGP) CL. Contrast visual acuity was measured with the multiple-contrast visual acuity chart developed by Wang and Katsumi, which consists of four parts with different contrast levels 5%, 15%, 90% and 90% with reverse polarity. Contrast visual acuity score was determined by the total number of correct answers.

Results: In 15 normal subjects, the contrast visual acuity score was 78.6 points. In the CL users, the total score was 73.5 points in the daily disposable SCL group and 70.6 in the 2-week frequent replacement SCL group, lowest among the CL users. In the conventional SCL and RGPCL groups, the score was 73.1 points. Overall, contrast visual acuity showed a decrease compared with normalcy, especially in the low contrast optotypes.

Conclusions: Measurement of contrast visual acuity is helpful in assessing corneal function, so may be of use preventing CL-related problems.