在調節中虹膜所扮演的角色

http://www.ncbi.nlm.nih.gov/pubmed/21357397

這篇論文實驗中，將雞的虹膜切除，觀察水晶體與眼壓的變化。

結論是虹膜對於眼的屈光與生長的影響極小，意指在正視化與近視的發展過程中，虹膜並不會造成影響。眼壓也沒有受到手術的影響，意指對房水排出也不具重要角色


Borishs Clinical Refraction/Accommodation,  the Pupil,  and Presbyopia/Kenneth J.  Ciuffreda
瞳孔對調節的影響主要在三方面，進光量、焦深及週邊像差

這是瞳孔直徑對焦深所做的圖形，瞳孔越小焦深越大(影像較不易感到模糊)。

這是瞳孔大小與視力的關係圖。紅線代表正常情況下(小瞳孔進光量減少)瞳孔直徑與視力的關係，3~4mm最佳。虛線代表經過亮度補償後(將網膜亮度調整一致，排除進光量影響，也就是只剩周邊像差的影響)與視力的關係，瞳孔越大，像差越大，視力越差。

Invest Ophthalmol Vis Sci. 2011 Jul 1;52(7):4710-6. Print 2011 Jun.

The role of the iris in chick accommodation.

Ostrin LA, Liu Y, Choh V, Wildsoet CF.

Source

School of Optometry, University of California Berkeley, Berkeley, California 94720, USA. laostrin@gmail.com

Abstract

PURPOSE:

Peripheral defocus, higher-order aberrations, and accommodation interact with pupil size to influence retinal image quality and possibly eye growth. Iridectomy (ID) provides a fixed, enlarged pupil. Results from in vitro studies suggest that ID may reduce or eliminate accommodation in the chicken. This paper further investigates the effects of ID on chicken accommodation, eye growth, and refractive development.

METHODS:

Refraction, biometry, and corneal curvature were measured, before, and after topical instillation of nicotine in 43 White-Leghorn chickens that had undergone monocular ID. Intraocular pressure (IOP) was measured, and eyes were imaged with anterior segment optical coherence tomography (OCT) during accommodation. In vitro preparations were used to examine accommodation responses in a lens-scanning instrument.

RESULTS:

Iridectomy induced small but significant decreases in anterior and vitreous chamber depths and an increase in lens thickness (LT). IOP was similar in iridectomized and control eyes from 1 week on. In vivo, nicotine induced similar accommodative changes in iridectomized and control eyes. OCT images revealed a forward displacement of the iris during accommodation in control eyes. Iridectomized and control eyes showed similar increases in LT. In vitro, iridectomized eyes showed minimal nicotine-induced accommodation.

CONCLUSIONS:

Refraction and eye growth were minimally affected by ID in chickens, implying that emmetropization was unaffected and supporting the use of ID as a tool in emmetropization and myopia studies. The greatly attenuated accommodative responses in vitro for iridectomized eyes suggest a role of biomechanical factors in the chick. IOP was unaffected by the surgery, implying that the iris musculature is not essential for maintaining aqueous outflow pathways.