The first record of leucism in the Rhabdophis tigrinus (Boie, 1826) (Squamata, Colubridae) in South Korea

Leucism, in which pigmentation is lost over part or the entire body of an animal, has a range of possible genetic causes. Here, we report leucism in an individual tiger keelback (Rhabdophis tigrinus) found on Jeung Island, Shinan-gun, Jeollanam-do, South Korea, during a survey of the distribution of reptiles in the area. The individual was observed sunbathing in the bushes next to a pond. This individual exhibited ecdysis, thus it considered that have normal feeding activity. Our report represents the first observation of leucism in R. tigrinus, and thus, further analysis is needed of this phenotype to more clearly understand its impact on the species and its natural history.

Sex- and Age-Dependent Wide-Field Choroidal Thickness Differences in Healthy Eyes

In this study, we aimed to map and characterize the choroidal thickness over a wide area from the posterior pole to the vortex vein in normal eyes. This observational study included 146 healthy eyes (63 male). Three-dimensional volume data were acquired to create a choroidal thickness map using swept-source optical coherence tomography. The map was classified as type A if an area with a choroidal thickness >250 µm in the vertical direction from the optic disc, and the area corresponding to the watershed was not observed, or as type B if such an area was observed. The relationship between the ratio of groups A to B and age was compared by classifying the age for three age groups: <40, 40-60, and >60 years in men and women. In men and women, 69.8% and 49.4% were classified as type A, respectively, with significant sex differences (p = 0.013). The proportion of type B decreased with increasing age in both the sexes. There was a significant difference between ≤60 and >60 years in men and between ≤40 and >40 years in women (p < 0.05). To conclude, the wide-area choroidal thickness and the age-dependent changes in healthy eyes differed between the sexes.

The development of a reference database with the Topcon 3D OCT-1 Maestro

Importance

The paper presents the range for measurements taken with a new spectral domain optical coherence tomography (OCT) device to establish a reference database for discrimination purposes.

Objective

To report the range of thickness values for the new Topcon Maestro 3D OCT device with 2 scan size settings: the 12×9 mm wide field and 6×6 mm scans.

Design

Prospective, multicenter cohort study conducted at 7 clinical sites across the USA.

Setting

Primary eyecare clinics within academic, hospital, and private practice locations.

Participants

Healthy volunteers; all enrolled participants underwent a complete ophthalmological examination to confirm healthy ocular status prior to being enrolled in the study.

Main outcome measure

Average and 1st, 5th, 95th, and 99th percentile ranges for OCT parameters Early Treatment Diabetic Retinopathy Study macula full retinal thickness, ganglion cell + inner plexiform layer thickness (GCL + IPL), ganglion cell complex (GCC) thickness, circumpapillary retinal nerve fiber layer (cpRNFL) thickness.

Results

Three hundred and ninety-nine eyes of 399 subjects were included in the analysis. Mean (SD) age was 46.3 (16.3) years (range 18–88 years). Forty-three percent of the subjects were male. Mean (SD) measurements (in μm) for the 12×9 mm wide scan were as follows: foveal thickness=237.079 (20.899), GCL + IPL=71.363 (5.924), GCC=105.949 (8.533), cpRNFL=104.720 (11.829); measurements for the 6×6 mm scans were as follows: foveal thickness=234.000 (20.657), GCL + IPL=71.726 (5.880), GCC=106.698 (9.094), cpRNFL=104.036 (11.341).

Conclusion

The overall normal thickness values reported with Topcon 3D OCT-1 Maestro were like those studies with OCT from different manufactures. The reference limits at the 1st, 5th, 95th, and 99th percentile points establish the thresholds for the quantitative comparison of the cpRNFL and the macula in the human retina to a database of known healthy subjects.

Relationship between macular inner retinal layer thickness and corresponding retinal sensitivity in normal eyes

PURPOSE

The correlation between standard automated perimetry (SAP) sensitivity and macular inner retinal layer thickness in eyes with glaucoma is well known. We examined whether the corresponding correlation is also significant in normal eyes.

METHODS

One eye of each of 195 normal subjects was included. The average thickness of the macular ganglion cell-inner plexiform layers (GCIPL) and the macular retinal nerve fiber layer/GCIPL (ganglion cell complex, GCC) in four regions with 0.6-mm-diameter circular area corresponding to the four central test points of the Humphrey Field Analyzer 24-2 test program, adjusted for ganglion cell displacement, were measured using spectral-domain optical coherence tomography (SD-OCT) and correlated to the mean SAP sensitivity (in 1/Lambert scale) at the corresponding test points with a multiple regression analysis using age, refraction, disc size, sex, and laterality of the eye as other explanatory variables.

RESULTS

In normal eyes, GCIPL and GCC thickness (in micrometers) showed significant correlation to SAP sensitivity in corresponding areas, with partial regression coefficients of 0.0016 (P = 0.036) and 0.0022 (P = 0.023), respectively. Other significantly correlated factors were age and GCIPL (-0.18, P = 0.000), age and GCC (-0.20, P = 0.000), and refraction and GCIPL (0.92, P = 0.012). Similar analyses at each of the four test points yielded essentially the same results, although partial correlation coefficients were not always significant.

CONCLUSIONS

A thicker macular GCIPL or GCC was weakly but significantly associated with higher SAP sensitivity in the corresponding macular region in normal eyes.

Anterior segment biometry using ultrasound biomicroscopy and the Artemis-2 very high frequency ultrasound scanner

Purpose

To compare the precision of anterior chamber angle (ACA) and anterior chamber depth (ACD) measurements taken with ultrasound biomicroscopy (UBM) and the Artemis-2 Very High Frequency Ultrasound Scanner (VHFUS) in normal subjects.

Design

Prospective study.

Methods

We randomly selected one eye from each of 59 normal subjects in this study. Two subjects dropped out of the study; the associated data were excluded from analysis. ACA and ACD measurements were obtained using the VHFUS and the UBM. The results were compared statistically using repeated-measures analysis of variance for the intraobserver repeatability, unpaired t-test, and limits of agreement.

Results

The average ACA values for the UBM and the VHFUS (±standard deviation) were 41.83° ± 5.03° and 33.36° ± 6.03°, respectively. The average ACD values were 2.96 ± 0.34 mm and 2.87 ± 0.31 mm. The intraobserver repeatability analysis of variance P-values for ACA and ACD measurements using UBM were 0.10 and 0.68, respectively; for the Artemis-2 VHFUS, the respective values were 0.68 and 0.09. The difference in ACA measurements was statistically significant (t = 8.41; P < 0.0001), while the difference in ACD values was not (t = 1.51; P < 0.13). The mean ACA difference was 8.50° ± 2.50°, and the limits of agreement were +13.30° to −3.60°. The mean ACD difference was 0.09 ± 0.27 mm, and the limits of agreement ranged from 0.61 mm to −0.43 mm. The mean difference percentage of ACD was 3.1% for both instruments.

Conclusion

In case of the ACD, both instruments can be used interchangeably; however, with the ACA instruments, they cannot be used interchangeably.

Comparison of central corneal thickness measurements using ultrasound pachymetry, ultrasound biomicroscopy, and the Artemis-2 VHF scanner in normal eyes

Purpose

To compare the precision of central corneal thickness (CCT) measurements taken with the handheld ultrasound pachymeter (USP), ultrasound biomicroscopy (UBM), and the Artemis-2 very high frequency ultrasound scanner (VHFUS) on normal subjects.

Design

Prospective study.

Methods

One eye from each of 61 normal subjects was randomly selected for this study. The measurements of the CCT were taken with the USP, VHFUS, and UBM. Results were compared statistically using repeated-measures analysis of variance (ANOVA), Pearson’s correlation coefficient, and limits of agreement.

Results

The average CCT (± standard deviation) was 530.1 ± 30.5 μm, 554.9 ± 31.7 μm, and 559.5 ± 30.7 μm for UBM, VHFUS, and USP respectively. The intraobserver repeatability analyses of variance are not significant for USP, UBM, and VHFUS. P-values were 0.17, 0.19, and 0.37 respectively. Repeated-measures ANOVA showed a significant difference between the three different methods of measuring CCT (P = 0.0001). The ANOVA test revealed no statistically significant difference between USP and VHFUS (P > 0.05), yet statistical significant differences with UBM versus USP and UBM versus VHFUS (P < 0.001). There were high correlations between the three instruments (P < 0.0001). The mean differences (and upper/lower limits of agreement) for CCT measurements were 29.4 ± 14.3 (2.7/56), 4.6 ± 8.6 (−14.7/23.8), and −24.8 ± 13.1 (−50.4/0.8) for USP versus UBM, USP versus VHFUS, and UBM versus VHFUS, respectively.

Conclusion

The UBM produces CCT measurements that vary significantly from those returned by the USP and the VHFUS, suggesting that the UBM may not be used interchangeably with either equipment for monitoring the CCT in the clinical setting.