The Role of the Iris in Chick Accommodation

Ostrin, Lisa A; Liu, Yue; Choh, Vivian; Wildsoet, Christine F.

doi:10.1167/iovs.10-6819

Cited by 14 publications

(11 citation statements)

References 36 publications

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“…This assertion is mainly due to the presence of a compact layer of smooth muscle cells throughout all the thickness of the iris in two species of raptors of different lifestyle, not detectable in the other species. Literature report that the avian iris is not only involved in pupillary reflex (as in mammals) but also in the reflex of lens accommodation, based on contraction of iris musculature which determine changes in curvature of the lens (Ostrin et al, 2011). These reflexes are closely connected to different predatory attitudes.…”

Section: Discussionmentioning

confidence: 99%

Morphological Study of the Iris Musculature in Diurnal and Nocturnal Raptors

et al. 2016

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COLI, A.; STORNELLI, M. R.; BARSOTTI, G.; CECCHERELLI, R.; GIANI, E.; LENZI, C. & GIANNESSI, E.Morphological study of the iris musculature in diurnal and nocturnal raptors. Int. J. Morphol., 34(2):503-509, 2016. SUMMARY:In literature it is established that the iris musculature consists of striate muscle fibers in birds while in mammals it consists of smooth muscles. Some authors report the presence of smooth muscle tissue also in the iris of some species of birds. In the present study we report on the iris muscle tissues (type of tissue, direction and mean diameter of muscle fibers or cells) in five species of Accipitriformes (diurnal raptors) and four species of Strigiformes (nocturnal raptors) because they show different way of life depending of their predatory behavior. This morphological study was carried out from raptors died or euthanized at the Wild Life Rescue Centre of Sea and Water birds in Livorno (Italy). From histological examination of iris serial radial sections we find both striated and smooth musculature even if with marked differences among analyzed species, not directly correlated with diurnal or nocturnal lifestyle. Striated fibers are always present, mainly with cross direction, throughout the iris stroma, while the histological differences concern the smooth cells. Indeed, harrier and sparrow hawk (Accipitriformes) and great horned owl and little owl (Strigiformes) show a compact layer of cross smooth muscle cells throughout the iris stroma. In the other species analyzed smooth muscle cells are slightly detectable as scattered or not detectable. Since the cross smooth muscle tissue allows to maintain a myotic state for extended periods of time, our results might be correlated more to the predatory behavior than the taxonomic order.

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Section: Discussionmentioning

confidence: 99%

Morphological Study of the Iris Musculature in Diurnal and Nocturnal Raptors

et al. 2016

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“…Speculation exists whether accommodation‐related defocus plays a role in emmetropisation. Several animal models of myopia are known to show active accommodation, including the chick, marmoset, and rhesus monkey, and have been utilised to examine the influence of accommodation in eye growth. Non‐human primates exhibit lenticular accommodation, similar to humans.…”

Section: Accommodationmentioning

confidence: 99%

Optical mechanisms regulating emmetropisation and refractive errors: evidence from animal models

Chakraborty

Ostrin

Benavente-Perez

et al. 2020

Clinical and Experimental Optometry

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Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non‐human primates, tree shrews, guinea pigs, and mice. Extensive research on optical, biochemical, and environmental mechanisms contributing to refractive error development in animal models has provided insights into eye growth in humans. Importantly, animal models have taught us that eye growth is locally controlled within the eye, and can be influenced by the visual environment. This review will focus on information gained from animal studies regarding the role of optical mechanisms in guiding eye growth, and how these investigations have inspired studies in humans. We will first discuss how researchers came to understand that emmetropisation is guided by visual feedback, and how this can be manipulated by form‐deprivation and lens‐induced defocus to induce refractive errors in animal models. We will then discuss various aspects of accommodation that have been implicated in refractive error development, including accommodative microfluctuations and accommodative lag. Next, the impact of higher order aberrations and peripheral defocus will be discussed. Lastly, recent evidence suggesting that the spectral and temporal properties of light influence eye growth, and how this might be leveraged to treat myopia in children, will be presented. Taken together, these findings from animal models have significantly advanced our knowledge about the optical mechanisms contributing to eye growth in humans, and will continue to contribute to the development of novel and effective treatment options for slowing myopia progression in children.

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“…Young chicken have been widely used in studies of eye growth regulation and myopia, [1][2][3][4] and, to a lesser extent, as a model of glaucoma. 5 Intraocular pressure (IOP) has been evaluated in a number of these studies, [6][7][8] with early studies of IOP making use of either applanation tonometry 7,[9][10][11] or direct manometry of cannulated eyes. 12 More recently, rebound tonometry has been become available as an additional option for measuring IOP, 13,14 with commercially available models specifically designed for use with small animals (TonoLab for mice and rats), large animals (TonoVet for rabbits, cats, dogs and horses), and humans (ICare and ICare Home).…”

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confidence: 99%

“…[36][37][38][39][40] Rebound tonometry has been utilized in two studies involving chicks. 6,35 In one of these studies involving 3-week old chicks, investigators found that IOP was significantly associated with corneal thickness and body weight. 35 However, rebound tonometry has not yet been validated or calibrated in chicks for the range of ages often utilized in eye growth studies.…”

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confidence: 99%

A Comparison of Applanation and Rebound Tonometers in Young Chicks

Ostrin

Wildsoet

2020

Current Eye Research

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Purpose: To assess the validity of and compare applanation and rebound tonometry readings of intraocular pressure in alert normal chicks from ages 3 to 45 days. Methods: Intraocular pressures (IOPs) were measured weekly in awake White Leghorn chicks, from ages 3-45 days (n = 22-30 per age group), with both applanation Tono-Pen and rebound TonoLab tonometers. Three repeated measurements on individual eyes were used to derive variance data for both instruments at each age. Calibration curves were also derived for each instrument and each age, weekly from ages 10-45 days (n = 3-4 per age group), from in situ manometry data collected over IOP settings of 0 to 100 mmHg in 5 mmHg steps in cannulated eyes. Results: The TonoLab showed less within measurement variability, but more variability with age, than the Tono-Pen. The coefficient of variation ranged from 3.8-8.3% for the TonoLab, compared to 11.0-19.7% for the Tono-Pen across all ages. For the youngest, 3 day-old chicks, mean IOPs recorded with the Tono-Pen and TonoLab were not significantly different (17.0 ± 5.6 and 15.2 ± 3.7 mmHg, respectively, P = .27). However, with increasing age, IOP readings significantly increased for the TonoLab (P < .001), whereas Tono-Pen readings did not. Compared to manometry settings, the Tono-Pen tended to underestimate IOPs while the TonoLab overestimated IOPs over the range 20-60 mmHg, saturating thereafter; there were also age-dependent differences for the TonoLab. Conclusions: Both the Tono-Pen and TonoLab gave IOP readings that differed from manometry settings in normal young chicks over some or all of the ages tested. These results reinforce the importance of calibrating clinical tonometers in animal studies involving IOP as a key variable.

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The Role of the Iris in Chick Accommodation

Cited by 14 publications

References 36 publications

Morphological Study of the Iris Musculature in Diurnal and Nocturnal Raptors

Morphological Study of the Iris Musculature in Diurnal and Nocturnal Raptors

Optical mechanisms regulating emmetropisation and refractive errors: evidence from animal models

A Comparison of Applanation and Rebound Tonometers in Young Chicks

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