Blue Irises Research Articles

Sensorineural deafness in purebred white Devon Rex cats.

Data regarding congenital sensorineural deafness (CSD) in client-owned, white Devon Rex cats is limited because most of the information on this disease comes from experiments on mixed-breed cats. Provide data on the occurrence of CSD in a population of client-owned purebred white Devon Rex cats. Forty client-owned, purebred, white Devon Rex cats examined at 2 different facilities. Median age of the examined cats was 19 weeks. Hearing status was defined by use of brainstem auditory evoked responses. The occurrence of sensorineural deafness in the studied population of Devon Rex cats was estimated at 10%. Unilateral and bilateral deafness occurred equally often, with 2 individuals having each (ie, 5.0%). No association between the occurrence of CSD and sex could be found, χ2 (1, n = 40) = 0.001 (P > .99). No association between blue irises and deafness was noted in the studied population, χ2 (1, n = 40) < 0.01 (P > .99). The occurrence of CSD in a population of client-owned, white Devon Rex cats was found to be lower compared with data obtained in previously conducted studies of deafness in purebred cats. In the studied population of Devon Rex cats, no association between blue irises and CSD was found.

Utilizing 3D Printing Technology to Create Prosthetic Irises: Proof of Concept and Workflow.

There are currently limited treatment options for aniridia. In this context, 3D printed iris implants may provide a cost-effective, cosmetically acceptable alternative for patients with aniridia. The purpose of this study was to develop a proof-of-concept workflow for manufacturing 3D printed iris implants using a silicone ink palette that aesthetically matches iris shades, identified in slit lamp images. Slit lamp iris photos from 11 healthy volunteers (3 green; 4 blue; 4 brown) were processed using k-means binning analyses to identify two or three prominent colors each. Candidate silicone inks were created by precisely combining pigments. A crowdsourcing survey software was used to determine color matches between the silicone ink swatches and three prominent iris color swatches in 2 qualifying and 11 experimental workflows. In total, 54 candidate silicone inks (20 brown; 16 green; 18 blue) were developed and analyzed. Survey answers from 29 individuals that had passed the qualifying workflow were invited to identify "best matches" between the prominent iris colors and the silicone inks. From this color-match data, brown, blue, and green prototype artificial irises were printed with the silicone ink that aesthetically matched the three prominent colors. The iris was printed using a simplified three-layer five-branch starburst design at scale (12.8 mm base disc, with 3.5 mm pupil). This proof-of-concept workflow produced color-matched silicone prosthetic irises at scale from a panel of silicone inks using prominent iris colors extracted from slit lamp images. Future work will include printing a more intricate iris crypt design and testing for biocompatibility.

Iris color as a predictive factor for intraoperative floppy iris syndrome.

To assess the influence of iris color on the predisposition for intraoperative floppy iris syndrome (IFIS) during cataract surgery. Medical records of patients who underwent cataract surgery in two medical centers between July 2019 and February 2020 were reviewed. Patients younger than 50years, with preexisting ocular conditions affecting pupillary size or anterior chamber depth (ACD), and combined procedures were excluded. The remaining patients were questioned via telephone regarding their iris color. The association of IFIS occurrence and severity with iris color was tested using univariant and multivariant analyses. Overall, 155 eyes of 155 patients were included, 74 with documented IFIS and 81 without. The mean age was 74.03 ± 7.09years, and 35.5% were female. The most common iris color among study eyes was brown (110/155, 70.97%), followed by blue (25/155, 16.13%) and green (20/155, 12.90%). Compared to brown-colored eyes, blue irises exhibited a 4.50-fold risk for IFIS (OR = 4.50, 95% CI: 1.73-11.70, p = 0.002), and green irises 7.00-fold risk (OR = 7.00, 95% CI: 2.19-22.39, p = 0.001). After adjusting for possible confounders, the results remained statistically significant (p < 0.01). Light-colored irises tended to exhibit a more severe IFIS compared to the brown iris group (p < 0.001). IFIS bilaterality was also affected by iris color (p < 0.001), with a 10.43-fold risk for fellow eye IFIS in the green iris group compared to eyes with brown irises (OR = 10.43, 95% CI: 3.35-32.54, p < 0.001). Light iris color was associated with a significantly increased risk of IFIS occurrence, severity, and bilaterality on univariate and multivariate analysis in this study.

Colour stability during production of printed ocular prostheses

AbstractOcular prostheses have been used for centuries to restore patient confidence, psychosocial relationships and to improve quality of life. Methodology for producing accurate prostheses has improved with technological discoveries. Recently, hand painting ocular prostheses has been the go‐to method for creating life like prostheses. However, digital printing a print to envelope around an acrylic prosthesis has been shown to decrease treatment and rehabilitation times, whilst still producing high‐definition ocular prostheses. Despite these improvements, little is known about the colour stability of digitally printed ocular prostheses. To better understand the colour stability of digital prostheses 30 samples simulating ocular prostheses were created, containing 10 with blue iris, 10 combination/green iris and 10 with sepia (brown) irises. Colour measurements were taken using a data spectrophotometer, from two defined points, the iris and sclera for both pre‐polymerisation and post‐polymerisation to assess colour variance. Colour coordinate data was gathered and was analysed using a one‐way analysis of variance test and a paired t‐test, both with alpha = 0.05. Significant colour variations were found for each iris colour and for the sclera. The sclera showed the largest colour variation with a ΔE of 4.75, followed by the brown irises, the green irises and then blue irises with ΔE values of 3.29, 2.47 and 1.82, respectively. This is a significant decrease compared to current hand painting methods which have an average colour variance of ΔE = 20. This shows a large increase in colour stability which can drastically improve patient satisfaction and quality of life.

Evaluation of the prevalence of congenital sensorineural deafness in a population of 72 client-owned purebred white cats examined from 2007 to 2021

BackgroundData on sensorineural deafness (CSD) in purebred white client-owned cats is limited as most of the information on this disease entity is assured from mixed-breed experimental colonies. It is known that cats with blue irises are more predisposed to CSD having been described as a condition in which many structures in the inner ear are damaged resulting in hearing loss. Cats with CSD are born deaf or lose their hearing irreversibly within the first 4-5 weeks of life. It is important to diagnose cats with this hereditary condition in order to eliminate affected individuals from breeding. The objectives of this study were to ensure data on prevalence of CSD in a population of 72 client-owned purebred white cats in Poland according to the color of the irises and to determine if there are any predispositions with regard to CSD among different breeds of cats in which the dominant W gene is present.ResultsConducted study included 72 purebred white cats from six different breeds. The prevalence of CSD in the conducted study was 16.7%, CI95 [8.9%; 23.3%]. Unilateral deafness (11.1%, CI95 [4.9%; 20.7%]) was more common than bilateral CSD (5.6%, CI95 [1.5%; 13.6%]). The studies did not show any association between sex and CSD, p = .46. No association between the blue color of irises and deafness in the studied population could be found, p = .91. When compared to the rest of the examined population, no association was found between CSD and a particular breed.ConclusionsOverall prevalence of CSD regarding the examined population of purebred client-owned cats was reported as lower when compared to previous studies concerning purebred cats. Cats with blue irises are more likely to be deaf in accordance to the current state of knowledge, however in the conducted study, no significant association between the presence of blue irises and deafness in white purebred cats could be identified. In order to eliminate CSD from the population, it is necessary to conduct examinations and diagnose CSD in white cats with blue irises as well as with irises of color other than blue. Association between particular breed and CSD wasn’t identified.

Síndrome Waardenburg Tipo I condición inusual en población pediátrica. A propósito de un caso

Introducción: El síndrome de Waardenburg (SW) es un trastorno genético poco frecuente con una incidencia de 1 por 40000 habitantes. Es originado por mutaciones en múltiples genes; estas alteraciones genéticas ocasionan anomalías en el desarrollo de los tejidos derivados de las células de la cresta neural y producen hallazgos fenotípicos característicos como iris de color azul claro o heterocromía del iris, poliosis, sordera neurosensorial, entre otros.&#x0D; Objetivo: Describir un caso clínico poco frecuente con hallazgos clínicos típicos del síndrome de Waardenburg tipo 1.&#x0D; Material y métodos Estudio descriptivo, retrospectivo, presentación de un caso clínico.&#x0D; Resultados: Se presenta un caso clínico de un pre–escolar masculino, de 3 años de edad, con antecedentes patológicos familiares: abuelo paterno, padre y hermano paterno con probable antecedente genético de SW. Se establece la importancia del índice W en el diagnóstico y clasificación del síndrome. Los hallazgos aquí reportados muestran la variabilidad de las manifestaciones fenotípicas según la clasificación. Así contribuye a un diagnóstico precoz y oportuno para actuar en beneficio de la salud de los niños. &#x0D; Conclusiones: El Síndrome de Waarbendurg que se presenta en este caso clínico es de tipo 1, hallazgo inusual en Pediatría, se diferencia del tipo 2 clínicamente por la distopía cantorum, que es característica de WS tipo 1, se reporta este caso con el fin de contribuir en el diagnóstico precoz y a una calidad de vida.

Decline in prevalence of congenital sensorineural deafness in Dalmatian dogs in the United Kingdom.

BackgroundCongenital sensorineural deafness (CSD) is the most common type of deafness in Dalmatian dogs.ObjectivesTo use results of CSD screening in Dalmatian dogs in the United Kingdom in genetic analysis and to determine any changes in the prevalence of CSD in this breed over time.AnimalsA total of 8955 Dalmatian puppies undergoing hearing function screening using brainstem auditory evoked response (BAER) between July 1992 and February 2019.MethodsResults of BAER testing and pigmentation phenotypic data were linked to the UK Kennel Club Dalmatian pedigree database. Mixed model analysis was used to estimate variance parameters.ResultsThe overall prevalence of CSD was 17.8% (13.4%, unilateral; 4.4%, bilateral). Heritability of CSD was approximately 0.3 (across models) and significantly >0. Genetic correlations between CSD and blue irises (+0.6) and pigmented head patch (−0.86) were large in magnitude and significantly different form 0. Significant improving phenotypic and genetic trends were identified, likely as the result of selection against deafness, equivalent to avoiding breeding with the 4% to 5% of animals with the highest genetic risk of CSD.Conclusions and Clinical ImportanceA decrease in the prevalence and genetic risk of CSD implies breeders have been selecting for hearing dogs. Selective breeding based on estimated breeding values (EBVs) can help further decrease the prevalence of CSD in Dalmatians in the future.

Case of waardenburg syndrome type 1 in a family with dental abnormalities

Waardenburg syndrome type 1 (WS1; MIM #193500) is a rare autosomal-dominant auditory-pigmentary syndrome characterized by pigmentary abnormalities of the hair, skin, and eyes; congenital sensorineural hearing loss; and “dystopia canthorum.” The lateral displacement of the ocular inner canthi was caused by heterozygous mutation in the PAX3 gene on chromosome 2q36. This is the case report of a 7-year-old girl showing the characteristic features of WS1 with familial history. Four generations of the patient's family, comprising 32 members, were undertaken to determine the pattern of inheritance, expression of syndrome, and phenotypes. The clinical examination of the 32 family members (18 females, 14 males) showed that ten females (31.25%) and eight males (25%) were affected by WS1. The age of the patients ranged between 3 years and 76 years (mean 24.67 years). Out of 18 family members with WS1, ten members showed white forelock, six members showed dystopia canthorum, eight members had congenital sensorineural hearing loss, seven members had iris heterochromia, and three members had bilateral brilliant blue irises. Dental abnormalities were shown by nine family members including enamel hypoplasia, peg-shaped maxillary laterals, conical teeth, and class 3 malocclusion.

Prevalence of congenital sensorineural deafness in a population of client-owned purebred kittens in the United Kingdom.

BackgroundData about congenital sensorineural deafness (CSD) in white blue‐eyed cats derive mainly from research colonies, and information about client‐owned cats is limited.ObjectivesTo describe the prevalence of CSD in a client‐owned population of white purebred kittens and colored littermates in the United Kingdom.AnimalsOne hundred thirty‐two solid white client‐owned purebred kittens and 61 colored littermates, 6 to 21 weeks of age.MethodsRetrospective (56 cases) and prospective (137 cases) study. Hearing was assessed by brainstem auditory evoked response testing, and the entire litter was tested.ResultsCongenital sensorineural deafness was diagnosed only in solid white kittens, with a prevalence of 30.3% (15.9% bilateral, 14.4% unilateral). The prevalence of CSD was significantly higher in white kittens with 1 (44.4%) or 2 (50%) blue irises than in those without blue irises (22.2%). Kittens with at least 1 blue iris were 3.2 times more likely to have CSD than kittens without blue irises. In solid white kittens, CSD was diagnosed in 7 of 15 (46.7%) Turkish Vankedisi, 8 of 18 (44.0%) Maine Coon, 18 of 41 (43.9%) Norwegian Forest, 3 of 11 (27.3%) British Shorthair, 2 of 12 (16.7%) Devon Rex, 2 of 12 (8.3%) Persian, 1 of 21 (4.8%) Russian, and 0 of 2 Sphinx. The prevalence of CSD was significantly different in Norwegian Forest, Maine Coon, and Turkish Vankedisi kittens compared with Persian or Russian kittens.Conclusion and Clinical ImportanceWe identified a high prevalence of CSD in a population of client‐owned purebred white kittens in the United Kingdom and suggest differences in breed‐specific prevalence of CSD.

Distribution of iris color and its association with ocular diseases in a rural population of Iran

PurposeTo determine the distribution of iris color and its relationship with some ocular diseases in a rural population of Iran. MethodsTwo rural areas of the north and southwest of Iran were selected by a cross-sectional study using multi-stage cluster sampling. After selecting samples, the participants had an eye examination including measuring visual acuity, refraction, and Pentacam imaging. Then an eye examination for individuals was performed by slit-lamp. ResultsOut of 3851 invited people, 3314 participated in this study (participation rate, 86.05%). Dark brown [41.28%, confidence interval (CI) 95% = 31.88–50.68] and blue (0.99%, CI 95% = 0.57–1.41) were the most and the least type of iris colors among participants of this study. Compared to others, people with a dark iris have the biggest anterior chamber depth (ACD), angle and volume while central corneal thickness (CCT), keratometry and pupil were highest among people with a dark brown iris (P < 0.002). Considering the dark brown group as a base group, the chances of being afflicted to cataract among people with dark, light brown, green, and blue irises are 1.89 (CI 95% = 1.25–2.86), 1.53 (CI 95% = 1.17–2.01), 4.60 (CI 95% = 2.17–9.71), and 12.17 (CI 95% = 5.05–29.31), respectively. The chance of being afflicted to myopia among people with green irises and to hyperopia among people with blue irises were high (1.60, CI 95% = 1.08–2.36 and 3.20, CI 95% = 1.03–9.97, respectively). ConclusionsDark brown was the most prevalent iris color in rural areas of Iran. The index of cornea among people with dark and dark brown iris color is higher than other people, and people with light iris color are at a higher risk of developing eye disease such as cataract, corneal opacity, and refractive error. To determine this relationship and its usage for therapeutic and public health purposes, further studies are recommended.

Evolutionary history inferred from the de novo assembly of a nonmodel organism, the blue-eyed black lemur.

Lemurs, the living primates most distantly related to humans, demonstrate incredible diversity in behaviour, life history patterns and adaptive traits. Although many lemur species are endangered within their native Madagascar, there is no high-quality genome assembly from this taxon, limiting population and conservation genetic studies. One critically endangered lemur is the blue-eyed black lemur Eulemur flavifrons. This species is fixed for blue irises, a convergent trait that evolved at least four times in primates and was subject to positive selection in humans, where 5′ regulatory variation of OCA2 explains most of the brown/blue eye colour differences. We built a de novo genome assembly for E. flavifrons, providing the most complete lemur genome to date, and a high confidence consensus sequence for close sister species E. macaco, the (brown-eyed) black lemur. From diversity and divergence patterns across the genomes, we estimated a recent split time of the two species (160 Kya) and temporal fluctuations in effective population sizes that accord with known environmental changes. By looking for regions of unusually low diversity, we identified potential signals of directional selection in E. flavifrons at MITF, a melanocyte development gene that regulates OCA2 and has previously been associated with variation in human iris colour, as well as at several other genes involved in melanin biosynthesis in mammals. Our study thus illustrates how whole-genome sequencing of a few individuals can illuminate the demographic and selection history of nonmodel species.

Differences between wavefront and subjective refraction for infrared light.

To determine the accuracy of objective wavefront refractions for predicting subjective refractions for monochromatic infrared light. Objective refractions were obtained with a commercial wavefront aberrometer (COAS, Wavefront Sciences). Subjective refractions were obtained for 30 subjects with a speckle optometer validated against objective Zernike wavefront refractions on a physical model eye (Teel et al., Design and validation of an infrared Badal optometer for laser speckle, Optom Vis Sci 2008;85:834-42). Both instruments used near-infrared (NIR) radiation (835 nm for COAS, 820 nm for the speckle optometer) to avoid correction for ocular chromatic aberration. A 3-mm artificial pupil was used to reduce complications attributed to higher-order ocular aberrations. For comparison with paraxial (Seidel) and minimum root-mean-square (Zernike) wavefront refractions, objective refractions were also determined for a battery of 29 image quality metrics by computing the correcting lens that optimizes retinal image quality. Objective Zernike refractions were more myopic than subjective refractions for 29 of 30 subjects. The population mean discrepancy was -0.26 diopters (D) (SEM = 0.03 D). Paraxial (Seidel) objective refractions tended to be hyperopically biased (mean discrepancy = +0.20 D, SEM = 0.06 D). Refractions based on retinal image quality were myopically biased for 28 of 29 metrics. The mean bias across all 31 measures was -0.24 D (SEM = 0.03). Myopic bias of objective refractions was greater for eyes with brown irises compared with eyes with blue irises. Our experimental results are consistent with the hypothesis that reflected NIR light captured by the aberrometer originates from scattering sources located posterior to the entrance apertures of cone photoreceptors, near the retinal pigment epithelium. The larger myopic bias for brown eyes suggests that a greater fraction of NIR light is reflected from choroidal melanin in brown eyes compared with blue eyes.

The convergent evolution of blue iris pigmentation in primates took distinct molecular paths

How many distinct molecular paths lead to the same phenotype? One approach to this question has been to examine the genetic basis of convergent traits, which likely evolved repeatedly under a shared selective pressure. We investigated the convergent phenotype of blue iris pigmentation, which has arisen independently in four primate lineages: humans, blue-eyed black lemurs, Japanese macaques, and spider monkeys. Characterizing the phenotype across these species, we found that the variation within the blue-eyed subsets of each species occupies strongly overlapping regions of CIE L*a*b* color space. Yet whereas Japanese macaques and humans display continuous variation, the phenotypes of blue-eyed black lemurs and their sister species (whose irises are brown) occupy more clustered subspaces. Variation in an enhancer of OCA2 is primarily responsible for the phenotypic difference between humans with blue and brown irises. In the orthologous region, we found no variant that distinguishes the two lemur species or associates with quantitative phenotypic variation in Japanese macaques. Given the high similarity between the blue iris phenotypes in these species and that in humans, this finding implies that evolution has used different molecular paths to reach the same end. Am J Phys Anthropol 151:398–407, 2013.© 2013 Wiley Periodicals, Inc.

Influence of different disinfecting solutions on the color change of artificial irises used in ocular prostheses

Making an artificial iris with an aesthetically acceptable color is an important aspect of ocular rehabilitation. This work evaluated the influence of different disinfecting solutions on changes to the color of artificial irises used in ocular prostheses. Fifty samples simulating ocular prostheses were produced with cobalt blue artificial irises and divided (n = 10) according to the disinfectant used: neutral soap, Opti‐free, Efferdent, 1% hypochlorite, and 4% chlorhexidine. The samples were disinfected for 120 days and subjected to a color readings by spectrophotometry, using the CIE L*a*b* system, before the disinfection period (B), after 60 days of disinfectant exposure (T1), and after 120 days of disinfectant exposure (T2). Color differences (ΔE) were calculated for the intervals between T1 and B (T1B), and between T2 and B (T2B). The data were evaluated by analysis of variance and the Tukey Honestly Significantly Different (α = 0.05). All disinfectant groups exhibited color changes. The mean color change observed for all groups overall during T2B (ΔE = 3.51) was significantly greater than that observed during T1B (ΔE = 2.10). All groups exhibited greater color change for the b* values when compared to the a* and L* values. There were no significant differences between the disinfectant groups. It can be concluded that the time period of disinfection and storage significantly affected the stability of artificial iris color, independent of the disinfectant used. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 56–62, 2014

Reproducibility of straylight measurement by C-Quant for assessment of retinal straylight using the compensation comparison method

Straylight gives the appearance of a veil of light thrown over a person's retinal image when there is a strong light source present. We examined the reproducibility of the measurements by C-Quant, and assessed its correlation to characteristics of the eye and subjects' age. Five repeated straylight measurements were taken using the dominant eye of 45 healthy subjects (age 21-59) with a BCVA of 20/20: 14 emmetropic, 16 myopic, eight hyperopic and seven with astigmatism. We assessed the extent of reproducibility of straylight measures using the intraclass correlation coefficient. The mean straylight value of all measurements was 1.01 (SD 0.23, median 0.97, interquartile range 0.85-1.1). Per 10years of age, straylight increased in average by 0.10 (95%CI 0.04 to 0.16, p < 0.01]. We found no independent association of refraction (range -5.25 dpt to +2 dpt) on straylight values (0.001; 95%CI -0.022 to 0.024, p = 0.92). Compared to emmetropic subjects, myopia reduced straylight (-.011; -0.024 to 0.02, p = 0.11), whereas higher straylight values (0.09; -0.01 to 0.20, p = 0.09) were observed in subjects with blue irises as compared to dark-colored irises when correcting for age. The intraclass correlation coefficient (ICC) of repeated measurements was 0.83 (95%CI 0.76 to 0.90). Our study showed that straylight measurements with the C-Quant had a high reproducibility, i.e. a lack of large intra-observer variability, making it appropriate to be applied in long-term follow-up studies assessing the long-term effect of surgical procedures on the quality of vision.

Perceived Direction of Gaze from Eyes with Dark vs. Light Irises

Much of the previous research on the perceived direction of gaze has not specified eye color or pupil visibility. This study tests whether the lightness or darkness of a gazer's irises (typically brown vs. blue) affects their perceived direction of gaze. Twenty-five observers judged the direction of horizontal gaze from a model whose LCD-imaged head gazed toward points on the plane of the observer's face. The model's head was displayed with its natural brown irises and also with its irises digitally altered to look blue without pupils, blue with centered pupils, and blue with nasally decentered pupils. True gaze location was compared with the judged gaze location for each type of iris. For all iris types, observers judged that monocular gaze was biased outward from its true direction for all gaze locations, including central, whereas binocular gaze was close to centered and had a greater slope. Blue eyes with no pupil and blue eyes with a centered pupil exaggerated this perceived outward deviation for monocular gaze but binocular gaze remained the same. When the pupils were nasally decentered by a typical amount, straight monocular as well as binocular gaze appeared to be centered. The direction of monocular gaze from eyes that differ in the darkness of their irises is perceived differently, and, within the blue irises, small differences in pupil centration made surprisingly large differences in the perceived directions of gaze.

Phase delaying the human circadian clock with a single light pulse and moderate delay of the sleep/dark episode: no influence of iris color

BackgroundLight exposure in the late evening and nighttime and a delay of the sleep/dark episode can phase delay the circadian clock. This study assessed the size of the phase delay produced by a single light pulse combined with a moderate delay of the sleep/dark episode for one day. Because iris color or race has been reported to influence light-induced melatonin suppression, and we have recently reported racial differences in free-running circadian period and circadian phase shifting in response to light pulses, we also tested for differences in the magnitude of the phase delay in subjects with blue and brown irises.MethodsSubjects (blue-eyed n = 7; brown eyed n = 6) maintained a regular sleep schedule for 1 week before coming to the laboratory for a baseline phase assessment, during which saliva was collected every 30 minutes to determine the time of the dim light melatonin onset (DLMO). Immediately following the baseline phase assessment, which ended 2 hours after baseline bedtime, subjects received a 2-hour bright light pulse (~4,000 lux). An 8-hour sleep episode followed the light pulse (i.e. was delayed 4 hours from baseline). A final phase assessment was conducted the subsequent night to determine the phase shift of the DLMO from the baseline to final phase assessment.Phase delays of the DLMO were compared in subjects with blue and brown irises. Iris color was also quantified from photographs using the three dimensions of red-green-blue color axes, as well as a lightness scale. These variables were correlated with phase shift of the DLMO, with the hypothesis that subjects with lighter irises would have larger phase delays.ResultsThe average phase delay of the DLMO was -1.3 ± 0.6 h, with a maximum delay of ~2 hours, and was similar for subjects with blue and brown irises. There were no significant correlations between any of the iris color variables and the magnitude of the phase delay.ConclusionA single 2-hour bright light pulse combined with a moderate delay of the sleep/dark episode delayed the circadian clock an average of ~1.5 hours. There was no evidence that iris color influenced the magnitude of the phase shift. Future studies are needed to replicate our findings that iris color does not impact the magnitude of light-induced circadian phase shifts, and that the previously reported differences may be due to race.

Acislo Antonio Palomino de Castro y Velasco’s Immaculate Conception

Acislo Antonio Palomino de Castro y Velasco’s <i>Immaculate Conception</i>

Influence of eye colors of Caucasians and Asians on suppression of melatonin secretion by light

This experiment tested effects of human eye pigmentation depending on the ethnicity on suppression of nocturnal melatonin secretion by light. Ten healthy Caucasian males with blue, green, or light brown irises (light-eyed Caucasians) and 11 Asian males with dark brown irises (dark-eyed Asians) volunteered to participate in the study. The mean ages of the light-eyed Caucasians and dark-eyed Asians were 26.4 +/- 3.2 and 25.3 +/- 5.7 years, respectively. The subjects were exposed to light (1,000 lux) for 2 h at night. The starting time of exposure was set to 2 h before the time of peak salivary melatonin concentration of each subject, which was determined in a preliminary experiment. Salivary melatonin concentration and pupil size were measured before exposure to light and during exposure to light. The percentage of suppression of melatonin secretion by light was calculated. The percentage of suppression of melatonin secretion 2 h after the start of light exposure was significantly larger in light-eyed Caucasians (88.9 +/- 4.2%) than in dark-eyed Asians (73.4 +/- 20.0%) (P < 0.01). No significant difference was found between pupil sizes in light-eyed Caucasians and dark-eyed Asians. These results suggest that sensitivity of melatonin to light suppression is influenced by eye pigmentation and/or ethnicity.

Does a pleiotropic gene explain deafness and blue irises in white cats?

The prevalence of deafness is high in cat populations in which the dominant white gene is segregating. The objective of this study was to investigate whether there is a gene that is responsible for deafness as well as for blue eyes and to establish a plausible mode of inheritance. For this purpose, data from an experimental colony with deaf cats were analyzed. The hearing status was determined by acoustically evoked brain stem responses (BAER). Complex segregation analyses were conducted to find out the most probable mode of inheritance using maximum likelihood procedures. The prevalence of deafness and partial hearing in the experimental colony was 67% and 29%, respectively. The results of the bivariate segregation analysis support the hypothesis of a pleiotropic major gene segregating for deafness and blue iris colour. The high heritability coefficients for both traits, 0.55 and 0.75 respectively, indicate that beside the major gene there is an important influence of polygenic effects.