Appearance of the Human Eye: Optical Contributions to the “Limbal Ring”

Was Marilyn Monroe myopic and an early adopter of colored contact lenses? A review of the evidence and the early history of colored contact lenses

Wide availability and uptake of contact lenses came with the development of the first polymethyl methacrylate corneal lenses during the late 1940s. It is less well known that colored contact lenses were developed simultaneously. These innovations allowed both a degree of spectacle independence for ametropes and an ability to vary eye color. The impact on facial and ocular cosmesis was substantial, particularly for public figures such as actors. We have obtained contact lenses and matching casts manufactured by their inventor, Kevin M. Tuohy. Measurements of these suggest they were made for a myope, and we provide indirect evidence that the lenses were made for Marilyn Monroe. We also provide evidence that Monroe is likely to have been myopic, used colored contact lenses to change her eye color and may have been an early sufferer of contact lens overwear syndrome. The importance of ocular cosmesis can be overlooked in ophthalmic practice, yet it is of great interest to and importance for patients. It appears that discomfort, and even risk, will be tolerated to achieve a particular appearance. This is reflected in current techniques aimed at achieving improved cosmesis.

Large irides enhance the facial attractiveness of Japanese and Chinese women

Since large eyes are often perceived to enhance facial attractiveness, many individuals are motivated to change their eyes' appearance. Colored contact lenses are often used by young women to darken the limbal rings of their irides, to increase their facial attractiveness. Among Westerners, wearing contact lenses with limbal rings enhances facial attractiveness; a similar effect might exist for East Asians whose irides are darker; although, the mechanism underlying these preferences in Westerners and East Asians might differ. In this study, we investigated whether larger irides increased the attractiveness of Japanese and Chinese women, and whether this effect was accompanied by changes in perceived friendliness or youthfulness. We manipulated eye size by enlarging only the iris or the whole eye, and asked participants to rate face stimuli in terms of facial attractiveness, friendliness, and youthfulness. We found that larger irides enhanced not only attractiveness but also perceived youthfulness and friendliness, and that there was a significant correlation between attractiveness and friendliness. Further, iris-enlarged faces were perceived as more attractive even when the iris was originally dark, as enlarged dark irides were confused with dilated pupils, which are often perceived as a sign of attraction.

Diversity in Primate External Eye Morphology: Previously Undescribed Traits and Their Potential Adaptive Value

Comparative examinations of external eye morphology in primates initially focused on communicative functions of the eye. Subsequent work has failed to find consistent associations between specific eye morphologies and communicative functions. In this article, we review the field of primate external eye morphology and inspect publicly available and unpublished photographs. We identify and describe five commonly occurring traits that have not received attention so far. We cross-examined the clinical and psychological literature to propose potential adaptive functions. These potential adaptive functions include communicative functions, but also photoregulatory functions and photoprotective functions.

Put a (Limbal) Ring on It: Women Perceive Men's Limbal Rings as a Health Cue in Short-Term Mating Domains

Limbal rings are dark annuli encircling the iris that fluctuate in visibility based on health and age. Research also indicates their presence augments facial attractiveness. Given individuals' prioritization of health cues in short-term mates, those with limbal rings may be implicated as ideal short-term mates. Three studies tested whether limbal rings serve as veridical health cues, specifically the extent to which this cue enhances a person's value as a short-term mating partner. In Study 1, targets with limbal rings were rated as healthier, an effect that was stronger for female participants and male targets. In Study 2, temporally activated short-term mating motives led women to report a heightened preference for targets with limbal rings. In Study 3, women rated targets with limbal rings as more desirable short-term mates. Results provide evidence for limbal rings as veridical cues to health, particularly in relevant mating domains.

Atomic force microscopy and scanning electron microscopy analysis of daily disposable limbal ring contact lenses

BACKGROUND

Limbal ring (also known as 'circle') contact lenses are becoming increasingly popular, especially in Asian markets because of their eye-enhancing effects. The pigment particles that give the eye-enhancing effects of these lenses can be found on the front or back surface of the contact lens or 'enclosed' within the lens matrix. The purpose of this research was to evaluate the pigment location and surface roughness of seven types of 'circle' contact lenses.

METHODS

Scanning electron microscopic (SEM) analysis was performed using a variable pressure Hitachi S3400N instrument to discern the placement of lens pigments. Atomic force microscopy (Dimension Icon AFM from Bruker Nano) was used to determine the surface roughness of the pigmented regions of the contact lenses. Atomic force microscopic analysis was performed in fluid phase under contact mode using a Sharp Nitride Lever probe (SNL-10) with a spring constant of 0.06 N/m. Root mean square (RMS) roughness values were analysed using a generalised linear mixed model with a log-normal distribution. Least square means and their corresponding 95% confidence intervals were estimated for each brand, location and pigment combination.

RESULTS

SEM cross-sectional images at 500× and 2,000× magnification showed pigment on the surface of six of the seven lens types tested. The mean depth of pigment for 1-DAY ACUVUE DEFINE (1DAD) lenses was 8.1 μm below the surface of the lens, while the remaining lens types tested had pigment particles on the front or back surface. Results of the atomic force microscopic analysis indicated that 1DAD lenses had significantly lower root mean square roughness values in the pigmented area of the lens than the other lens types tested.

CONCLUSIONS

SEM and AFM analysis revealed pigment on the surface of the lens for all types tested with the exception of 1DAD. Further research is required to determine if the difference in pigment location influences on-eye performance.

Preliminary Evidence that the Limbal Ring Influences Facial Attractiveness

The limbal ring of the eye appears as a dark annulus where the iris meets the sclera. Both width and opacity of the limbal ring are influenced by iris pigmentation and optical properties of the region. With age the limbal ring becomes less prominent, making it a probabilistic indicator of youth and health. This raises the question: Are judgments of facial attractiveness sensitive to this signal in a potentially adaptive way? Here we show that the answer is yes. For male and female observers, both male and female faces with a dark and distinct limbal ring are rated as more attractive than otherwise identical faces with no limbal ring. This result is observed not just for upright faces but also for inverted faces, suggesting that the limbal ring is processed primarily as a local feature rather than as a configural feature in the analysis of facial beauty. We also discuss directions for future research that can clarify the role of the limbal ring in the visual perception of facial attractiveness.

Perceived direction of gaze from eyes with dark vs. light irises

PURPOSE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.