Two Novel Disease-Causing Variants in the PDE6C Gene Underlying Achromatopsia

We report the clinical phenotype and genetic findings of two variants in PDE6C underlying achromatopsia (ACHM). Four patients with the variant c.1670G&#x3e;A in exon 13 of the PDE6C gene were identified. Additionally, one had compound heterozygous genotype, with two variants in the <i>PDE6C</i> gene, a variant of c.2192G&#x3e;A in exon 18 and c.1670G&#x3e;A in exon 13. All patients presented the symptomatic triad of decreased visual acuity, severe photophobia, and colour vision disturbances. SD-OCT showed an absence of the ellipsoid zone, creating an optically empty cavity at the fovea in three patients. The patient with the compound heterozygous genotype presented a more severe subfoveal outer retina atrophy. ERG recordings showed extinguished responses under photopic and 30-Hz flicker stimulation, with a normal rod response. We identified two new variants in the <i>PDE6C</i> gene that leads to ACHM.

Time-course of adaptations for electroretinography and pupillography

Cones are primarily involved in photopic vision and light adaptation. Rods are responsible for scotopic vision and dark adaptation. The typical time-courses of light and dark adaptations have been known for century. However, information regarding the minimal adaptation time for electroretinography (ERG) and pupillography would be helpful for practical applications and clinical efficiency. Therefore, we investigated the relationship between adaptation time and the parameters of ERG and pupillography. Forty-six eyes of 23 healthy women (mean age, 21.7 years) were enrolled. ERG and pupillography were tested for right and left eyes, respectively. ERG with a skin electrode was used to determine amplitude (µV) and implicit time (msec) by the records of rod-, flash-, cone-, and flicker-responses with white light (0.01–30 cd·s/m2). Infrared pupillography was used to record the pupillary response to 1-sec stimulation of red light (100 cd/m2). Cone- and flicker- (rod-, flash-, and pupil) responses were recorded after light (dark) adaptation at 1, 5, 10, 15, and 20 min. Amplitude was significantly different between 1 min and ≥5 or ≥10 min after adaptation in b-wave of cone- or rod-response, respectively. Implicit time differed significantly between 1 min and ≥5 min after adaptation with b-wave of cone- and rod-response. There were significant differences between 1 min and ≥10 or ≥5 min after dark adaptation in parameter of minimum pupil diameter or constriction rate, respectively. Consequently, light-adapted ERGs can be recorded, even in 5 min of light adaptation time without special light condition, whereas dark-adapted ERGs and pupillary response results can be obtained in 10 min or longer of dark adaptation time in complete darkness.

Evaluation of Agility and Walking Ability in Elderly People

An important aspect of independent living in a super-aging society is the achievement of “successful aging” in mind and body. Recent large-scale epidemiological studies found that reduced walking ability significantly affects “extended healthy life expectancy” and “successful aging.” In terms of anatomy and physiology, “usual aging” (i.e., the inevitable decrease in walking function due to aging) occurs unless one undertakes daily physical activity. Conversely, aggressive moderate and habitual physical activity may lead to “successful aging” (i.e., maintained and improved walking function). Previous studies revealed that agility and walking ability are related to healthy life expectancy. Thus, we measured agility with a stick response test to investigate its relationship to gait, and determined whether this test could be substituted for a battery test of walking ability. This test has the convenience of shortening measurement time and requiring a wider measurement place than gait evaluation performed by actually walking. Correlation was observed between the rod response test and stride length (r = 0.60), walking speed (r = 0.38), and walking ratio (r = 0.34). Therefore, we propose that the rod response measurement is simpler than a simple walking ability test and can be used as a physical function measurement item that predicts the health and longevity of the elderly.