The importance of measurements of quality of vision (QOV) has been recognized, and contrast sensitivity function has been widely evaluated in clinical practice in addition to conventional visual acuity (VA). Recently, a functional visual acuity (FVA) test that can evaluate another aspect of visual function has been developed. This test includes an element of time axis and sequentially assesses VA for 60 seconds, allowing estimation of practical vision for a subject during continuous-gazing tasks such as driving and work at visual display terminals. The test was initially applied for the detection of masked impairment of visual function in patients with dry eye who complained of decreased visual function despite normal conventional VA. Thereafter, it was shown that the FVA system is a useful tool in the assessment of dynamic VA changes in various ocular pathologies and in the detection of subtle and early changes in visual function. More recently, several researchers modified the FVA system for the assessment of near vision and mesopic vision, and various new findings have been obtained by application of these modified systems. It is expected that FVA systems will be more broadly applied in clinical practice to gain a further understanding of visual function.

Purpose: To examine the correction effect of orthokeratology (Ortho) to suppress the progression of myopia in Japanese schoolchildren with mild myopia over a 2-year period.

Methods: This study involved 48 eyes of 24 schoolchildren who underwent Ortho (Ortho group) and 60 eyes of 30 schoolchildren who wore eyeglasses (control group). The two groups were simultaneously followed up over a 2-year period (the Ortho group subjects were followed for 3 additional weeks to remove the lenses). In all subjects, objective spherical equivalence (SE) during cycloplegia and axial length were examined.

Results: Over the 2-year follow-up period, objective SE variation and axial-length variation were -0.56±0.64 D (mean±SD) and 0.58±0.10 mm in the Ortho group and -1.40±0.66 D and 0.72±0.11 mm in the control group, respectively, with significantly minor progression of myopia and minor axial length elongation found in the Ortho group (p<0.01, p<0.05 unpaired t-test).

Conclusion: The findings of this 2-year follow-up study suggest the possibility that correction by orthokeratology can suppress the progression of myopia in Japanese schoolchildren with mild myopia.

Soft contact lenses (SCLs) change in shape along the cornea surface when worn because they are made of a soft material. The changes in shape of SCLs when worn were examined using three types of SCLs with different optical, intermediate, and bevel regions in this study. First, changes in SCL shape when worn were analyzed by the finite element method. Then, the effects of the changes in shape on SCL strength were examined by the ray-trace method. The results showed that 1) the shape of the SCLs changed by at least 0.25 D (diopter is a unit of measurement for lens strength) when worn; 2) the change in strength was small in SCLs having a shape that retains tear fluid in a small space in the intermediate region, as the optical region was displaced upward; and 3) bending deformation occurred in the bevel region due to tensile stress on the BC side and compressive stress on the FC side.

The waveform in the resting state of accommodation under fogging was analyzed using an advanced objective accommodometer (ARK-1s, NIDEK) in normal eyes of participants of various ages. The subjects were 219 persons (219 eyes) between 6 years and 47 years old without eye diseases affecting accommodation (81 males, 138 females; mean age, 16.7 ± 9.3 years old). The mean spherical equivalent of the subjects was -3.04 ± 2.31 D. Eyeblink and the rate of poor fixation (deletion rate) were used as indices representing the measurement reliability of models used for measurements in this study, and double the standard deviation of the refractivity (accommodation variation) was used as an index representing the stability of accommodation. The median deletion rate was 13.2%, and there was a tendency for the deletion rate to become higher as the cylindrical power became higher (p<0.005). The median accommodation variation was 0.15 D, and there was a tendency for the accommodation variation to become higher as age is low (p<0.05).

The ARK-1s was usable for measurement of accommodation even in young patients. It was suggested that the accommodation variation in the resting state of accommodation is affected by age in normal eyes.

The purpose of this study was to investigate accommodation lag at the time of accommodative stimulation in normal subjects. In this study, accommodation function was measured in 118 normal subjects using an advanced objective accommodometer (ARK-1s). All subjects were healthy, with no disease such as amblyopia or strabismus that could affect accommodation, and the eyes of all the subjects could change focus at the time of accommodative stimulation. In each subject, refractivity was measured as the subject looked at equally-refractive moving targets. These measurements were then plotted linearly and analyzed. Comparison between positive and negative accommodation showed that accommodation lag and accommodative fluctuation were statistically significantly larger for positive accommodation (p=0.0007 and p=0.0073, respectively). The statistical significance of accommodation lag increased with increased stimulation (p<0.0001). Use of the ARK-1s allowed for quantification and assessment of accommodation lag, thus suggesting that it can be an effective tool in the clinical setting for analyzing the accommodation dynamics of various diseases.