The effects of phenylephrine on pupil diameter and accommodation in rhesus monkeys

PURPOSE: Phenylephrine is used to dilate the iris through alpha-adrenergic stimulation of the iris dilator muscle. Sympathetic stimulation of the ciliary muscle is believed to be inhibitory, decreasing accommodative amplitude. Investigations in humans have suggested some loss of functional accommodation after phenylephrine. It is unclear whether this loss is due to direct action of phenylephrine on the ciliary muscle or to secondary optical factors associated with mydriasis. The purpose of this study was to determine whether phenylephrine affects Edinger-Westphal (EW)-stimulated accommodation in rhesus monkeys. METHODS: The time course for maximum mydriasis was determined by videographic pupillography after phenylephrine instillation in 10 normal rhesus monkeys. Static and dynamic EW-stimulated accommodative responses were studied in five iridectomized rhesus monkeys before and after phenylephrine instillation. Accommodative amplitude was measured with a Hartinger coincidence refractometer. Dynamic accommodative responses were measured with infrared photorefraction, and functions were fitted to the data to determine peak velocity versus accommodative response relationships. RESULTS: The maximum dilated pupil diameter of 8.39 +/- 0.23 mm occurred 15 minutes after administration of phenylephrine. In iridectomized monkeys, postphenylephrine accommodative amplitudes were similar to prephenylephrine amplitudes. Dynamic analysis of the accommodative responses showed linear peak velocity versus accommodative amplitude relationships that were not statistically different before and after phenylephrine. CONCLUSIONS: alpha-Adrenergic stimulation causes a strong pupil dilation in noniridectomized monkey eyes but does not affect EW-stimulated accommodative amplitude or dynamics in anesthetized, iridectomized rhesus monkeys.     

不同年龄健康人眼调节状态超声生物显微镜对比观察

目的 了解健康人眼在不同调节状态下,睫状体、晶状体形态位置动态变化的特点及其与年龄变化的关系.方法 利用超声生物显微镜(UBM),对70名不同年龄组正常人眼注视远、近不同距离视标时睫状体、晶状体形态位置的变化进行动态观察和统计学分析.结果 (1)视远时,睫状体厚度平均值(1.08±0.15)mm,睫状突长度平均值(1.92±0.29)mm, 睫状突宽度平均值(0.74±0.11)mm,晶状体中央厚度平均值(3.46±0.45)mm;视近时,睫状体厚度平均值(1.16±0.17)mm,睫状突长度平均值(2.05±0.27)mm,睫状突宽度平均值(0.67±0.09)mm,晶状体中央厚度平均值(3.57±0.42)mm;视近与视远相比,睫状体前部厚度增加、睫状突长度增加,睫状突宽度变小,晶状体中央厚度增加,各参数经独立样本t检验,P值均<0.05,差异有统计学意义.(2)随年龄增加,视远、视近时各形态参数与年龄间经Pearson检验存在相关性.结论 人眼视近时,睫状体各部肌纤维协调收缩,使睫状突变长变尖,睫状体向前向内移动,松弛悬韧带,晶状体借自身弹性变凸,中央厚度变厚,前后径增加.同时,随年龄增长,人眼调节力逐渐下降.支持Helmholtz的调节松弛学说.利用UBM可实时观察人眼调节时眼前节结构形态和位置的变化情况.     

Immunohistochemical study of the extracellular matrices related to accommodation in monkeys

PURPOSE: The mechanism of accommodation was studied by immunohistochemical staining of extracellular matrices in monkey eyes. METHODS: Frozen sections from five pairs of post-mortem eyes donated by physiologists were used. The antigens listed in Table 1 were selected, and a 2- or 3-step staining technique was used. Confocal laser microscopy was used to evaluate the staining and take photographs. Many frames were reconstituted for the Figures. RESULTS: a) The ciliary muscle was divided into circular and longitudinal portions by arrangement of alpha-smooth muscle actin and surrounded by dense nets of alpha-elastin at the inner border under pigmented ciliary epithelium. Elastin nets extended into the stroma of the ciliary processes. In the lens, elastin was observed in the equatorial and central subcapsular area. b) Zonules were heavily stained by fibrillin-1 as bundles. Continuous fibers connected the surface of ciliary processes with the lens capsule, and were also anchored along the ciliary epithelium toward the pars plana. Type IV collagen was seen in circumferential lens capsule and between the lens fibers, especially in the equator and central cortex. c) There was more alpha-1A adrenoceptor in the longitudinal than the circular portion of the ciliary muscle. CONCLUSION: Our results provide an argument against Helmholtz's theory, but in favor of Tsherning's theory. The accommodation to near might be accomplished by contraction of circular ciliary muscle held by elastin nets pulling the zonules centripetally. The zonular tension puts pressure on the equator and also pulls the lens capsule anterocentrally. This coordination of the matrices will shorten the equatorial plane of the lens and expand the inter-lens-fiber space, making the polar axis wider. As to the far accommodation, longitudinal muscle will pull the zonules peripherally, narrowing the inter-fiber space.     

Changes in accommodation with age: static and dynamic

Accommodative amplitude decreases with age, not with aging. The decrease is largely completed by age 40 years; only minor residual accommodation is present in most subjects after the mid-40s. Dynamical measurements show the accommodative response of subjects over 30 years of age to be significantly slowed (time constants of accommodation increases). Accommodation amplitude is less than 3 D by 30 years of age. Thus prepresbyopia is a sign of continual development, not of deterioration of the accommodative mechanism. Accommodation, or the change of clear vision with change in lens power, has been studied by many distinguished scientists including Descartes and Thomas Young. Helmholtz's "Theory of Accommodation" is a dual, indirect, active theory. There are both lenticular, including lens and capsule, and also extralenticular mechanisms, comprised of the zonule of Zinn or suspensory ciliary ligament and the ciliary muscle itself. The ciliary muscle does not act directly on the lens but indirectly through its action on the zonule of Zinn. Active contraction of the ciliary muscle, a unified muscle, produces accommodation; relaxation of the ciliary muscle permits relaxation of accommodation.     

Accommodative ciliary body and lens function in rhesus monkeys, I: normal lens, zonule and ciliary process configuration in the iridectomized eye

PURPOSE: The underlying causes of presbyopia, and the functional relationship between the ciliary muscle and lens during aging are unclear. In the current study, these relationships were studied in rhesus monkeys, whose accommodative apparatus and age-related loss of accommodation are similar to those in humans. METHODS: Centripetal ciliary body and lens equator movements were measured during accommodation in 28 eyes of 21 rhesus monkeys (ages, 5.7-26 years) by goniovideography. Ultrasound biomicroscopy was performed in 21 eyes of 17 monkeys. Narrowing of the angle between the anterior aspect of the ciliary body and the inner aspect of the cornea was used as a surrogate indicator of forward ciliary body movement during accommodation. RESULTS: Average centripetal ciliary body movement in older eyes (age > or =17 years, n = 16) was approximately 20% (0.09 mm) less than in young eyes (age, 6-10 years, n = 6), but not enough to explain the 60% (0.21 mm) loss in centripetal lens movement nor the 76% (10.2 D) loss in accommodative amplitude. Average forward ciliary body movement was 67% (49 degrees ) less in older (n = 11) versus young (n = 6) eyes. Maximum accommodative amplitude correlated significantly with the amplitude of centripetal lens movement (0.02 +/- 0.003 mm/D; n = 28; P < 0.001) and with forward ciliary body movement (3.34 +/- 0.54 deg/D; n = 21; P = 0.01). CONCLUSIONS: Decreased lens movement with age could be in part secondary to extralenticular age-related changes, such as loss of ciliary body forward movement. Ciliary body centripetal movement may not be the limiting component in accommodation in the older eye.     

Accommodation and presbyopia

The mechanism of accommodation has been studied for at least four hundred years. The most interesting aspect of accommodation is that its time course is well in advance of other physiological functions – it begins to decline by adolescence and is lost about two-thirds of the way through the normal line span. The state of presbyopia is reached when accommodation has declined sufficiently to interfere with close tasks requiring acute vision. Presbyopia is generally considered to originate with the 'plant' of the accommodative system, either within the lens and its capsule or within their support structures. One of the lenticular theories, the Hess–Gullstrand theory, is distinguished from other theories by its claim that as age increases there is an increasing excess amount of ciliary muscle contraction beyond the ability of the lens and capsule to respond to it. For all other theories, the maximum possible amount of ciliary muscle contraction is always necessary to produce maximum accommodation, at least beyond the age at which it reaches its peak. From my review of the present understanding of the mechanisms of accommodation and the theories of the development of presbyopia, I conclude that there is overwhelming evidence against the Hess–Gullstrand theory and that it is unlikely that changes in the ciliary muscle contractility contribute significantly to the development of presbyopia.     

Changes in crystalline lens radii of curvature and lens tilt and decentration during dynamic accommodation in rhesus monkeys

Dynamic changes in crystalline lens radii of curvature and lens tilt and decentration were measured during centrally stimulated accommodation in four iridectomized eyes of two adolescent rhesus monkeys. Phakometry measurements were performed dynamically using a custom-built, video-based, Purkinje-image instrument. Lens anterior and posterior radii were calculated from reflections of paired light sources from the ocular surfaces (Purkinje images PI, PIII, and PIV). Lens tilt and decentration were calculated assuming linearity between Purkinje image positions, eye rotation, lens tilt, and decentration. Because the monkey eyes were iridectomized, Purkinje images were referred to the mid-point of the double first Purkinje image (PI). Mean unaccommodated values of anterior and posterior lens radii of curvature were 11.11 +/- 1.58 mm and -6.64 +/- 0.62 mm, respectively, and these decreased relatively linearly with accommodation in all eyes, at a rate of 0.48 +/- 0.14 mm/D and 0.17 +/- 0.03 mm/D for anterior and posterior lens surfaces, respectively. Tilt and decentration did not change significantly with accommodation except for tilt around the horizontal axis, which changed at a rate of 0.147 +/- 0.25 deg/D. These results are important to fully characterize accommodation in rhesus monkeys.     

Magnetic resonance imaging of aging, accommodating, phakic, and pseudophakic ciliary muscle diameters

PURPOSE: To quantify in vivo accommodative changes in the aging human ciliary muscle diameter in phakic and pseudophakic eyes. SETTING: Department of Surgery/Bioengineering, UMDNJ-Robert Wood Johnson Medical School, Piscataway, and the Institute of Ophthalmology and Visual Science UMDNJ-New Jersey Medical School, Newark, New Jersey, USA. METHODS: Images were acquired from 48 eyes of 40 people between the ages of 22 and 91 years, 1 eye of 32 phakic volunteers and both eyes of 8 patients who had monocular implantation of a single-piece AcrySof intraocular lens (IOL) (Alcon Laboratories). Images were acquired during physiological accommodation and with accommodation at rest, and the diameter of the ciliary muscle ring was measured. RESULTS: Results show the ciliary muscle remains active throughout life. The accommodative change in its diameter (mean 0.64 mm) (P<.00001) was undiminished by age or IOL implantation. Preliminary data showed that the accommodative decrease in muscle diameter in phakic and pseudophakic eyes was statistically identical. The phakic eyes had a marked decrease in ciliary muscle diameter with advancing age for both accommodative states (P<.000001 and P<.000001), which did not appear to be altered by IOL implantation. The lens equator was constant with age in the unaccommodated human eye, resulting in decreased circumlental space with advancing age in the phakic eyes. CONCLUSION: Although the undiminished ability of the ciliary muscle to decrease its diameter with accommodation can be relied on in strategies for presbyopia correction, even in advanced presbyopia, the decreasing circumlental space and its potential effects on zonular tension must also be considered.     

Computer image analysis of ultrasound biomicroscopy of primate accommodation

PURPOSE: To assess and correct images of the eye for movements that can confound the evaluation of the presence, direction, and magnitude of intraocular movement of the crystalline lens equator during centrally induced ciliary muscle contraction (accommodation). METHOD: Ultrasound biomicroscopic (UBM) video images of a cynomologus monkey crystalline lens were obtained from an independent source. The images, prior to, during, and following electrical stimulation of the Edinger-Westphal (EW) nucleus were compared for evidence of movement of the crystalline lens equator. Extraocular eye movements were assessed by use of objective computer imaging analysis techniques. RESULTS: Extraocular eye movements were identified and reduced by using objective computer imaging analysis techniques to register and realign the corneal images. Highly significant corrections are required to effect corneal realignment. Analysis of paired and registered images from this data source indicates that any movements of the primate lens equator are not detectable when maximum accommodation was induced by EW stimulation. CONCLUSION: The displacement of the edge of the primate crystalline lens equator during electrically induced contraction of the ciliary muscle is a small displacement phenomenon, only analysable after confounding extraocular movements are removed from the compared images.     

Light and electron microscopy of the anterior chamber angle structures following surgical disinsertion of the ciliary muscle in the cynomolgus monkey.

Light and electron microscopic studies were done on 11 cynomolgus monkey eyes which had undergone total iris removal followed by surgical disinsertion of the ciliary muscle from the scleral spur 4.7 to 14.4 months earlier. Anterior chamber perfusion to measure gross outflow facility had been performed one to nine times postoperatively. Over most of the circumference in most eyes (1) the ciliary muscle had been retrodisplaced from the scleral spur and had reattached to the sclera more posteriorly; (2) ciliary muscle, trabecular meshwork, and Schlemm's canal appeared normal. A cyclodialysis cleft was never seen. Fixation of some eyes in the in vivo and in vitro presence of pilocarpine demonstrated the contractibility of the retrodisplaced muscle. In isolated areas where the ciliary body had been surgically cut, scar tissue of varying thickness connected scleral spur, sclera, ciliary body, zonule, and lens capsule, but did not infiltrate trabecular meshwork or Schlemm's canal. In such sectors, plasma cell-like cells replaced trabecular endothelial cells and were also present in the scar tissue, ciliary muscle, and surrounding vessel walls in the scar and sclera. In sectors of two eyes, a previously existing trabecular operculum extended posteriorly and completely covered the meshwork. The meshwork in these sectors was poorly perfused by aqueous humor, and electron-dense deposits were present beneath the inner wall of Schlemm's canal. Four totally iridectomized and two unoperated eyes from these monkeys were also examined; ciliary muscle, trabecular meshwork, and Schlemm's canal appeared normal in all, despite the numerous anterior chamber perfusions.     

Spatially variant changes in lens power during ocular accommodation in a rhesus monkey eye

This study investigated the changes in ocular aberrations that occur over the entire lens equatorial diameter during accommodation in iridectomized rhesus monkey eyes to understand the nature of accommodative lenticular deformation. Accommodation was centrally stimulated to a range of different response amplitudes (0 D to approximately 11 D), and ocular aberrations were measured with a Shack-Hartmann wavefront sensor in both eyes of one previously iridectomized 10-year-old rhesus monkey. At the highest amplitude in the two eyes, aberrations were analyzed over entrance pupil diameters ranging from 3 to 8 mm in steps of 1 mm. Root mean square error of the total measured aberrations, excluding defocus, increased systematically with increasing accommodation from about 1 to 3.5 microns. Spherical aberration became systematically more negative, and vertical coma increased significantly in magnitude with accommodation. There was a strong accommodative change in power near the center of the lens and little change in power at the periphery. At the highest accommodative state, decreasing the analyzed entrance pupil diameter from 8 to 3 mm considerably reduced the wavefront error. The greater increase in optical power near the central region of the lens, combined with an accommodative pupillary miosis, would serve to maximize accommodative refractive change while maintaining acceptable image quality.     

The zonula, lens, and circumlental space in the normal iridectomized rhesus monkey eye

PURPOSE: To document zonular orientation and suspension of the lens during accommodation, and age-related changes of the circumlental space (CLS) at rest and during accommodation, in living iridectomized rhesus monkey eyes. METHODS: The CLS was measured in 34 iridectomized eyes of 24 living rhesus monkeys, age 5.7 to 26 years, in the resting and accommodated state, and the orientation of the zonula and suspension of the lens during accommodation was assessed qualitatively. RESULTS: The nonaccommodated CLS decreased significantly with age in both the nasal and temporal quadrants and tended to do so at a slightly faster rate in the temporal quadrant. The CLS correlated significantly with the accommodative amplitude: the greater the CLS the greater the accommodative amplitude. Multiple regression analysis indicated that age and CLS together are better predictors of accommodative amplitude than is age alone. The zonula appeared taut in the nonaccommodated eye throughout the age range despite the age-related decline in CLS. CONCLUSIONS: Characterization of age-related changes in the accommodative apparatus may help to model the system for hypothesis testing. The CLS may be an indicator of presbyopia-related processes in surrounding tissues. However, these results do not prove that the width of the CLS, in and of itself, has a causal relationship with accommodative amplitude, or that changes in the CLS play a pathophysiological role in presbyopia.     

Comparison of pilocarpine-induced and stimulus-driven accommodation in phakic eyes

With the recent introduction of potentially accommodative intraocular lenses (IOL), there is a need for methods to evaluate their accommodative potential. In most studies assessing IOL movement, pilocarpine is used to stimulate contraction of the ciliary muscle. The aim of this study is to determine if pilocarpine-induced ciliary muscle contraction is comparable to physiological stimulus-driven accommodation in young and presbyopic subjects. Ten emmetropic young subjects (23-25 years) and 11 emmetropic presbyopic subjects (51-62 years) were included in this study. Anterior chamber depth (ACD) and lens thickness (LT) were assessed with partial coherence interferometry (PCI). A moveable stimulus was coupled to the PCI equipment for measurement of biometric lens changes. ACD was measured with the stimulus at infinity and then at the subjects individual nearpoint, and after application of two drops of 2% pilocarpine. In young subjects, there was no significant difference in lens change between nearpoint and pilocarpine stimulation. Presbyopic subjects showed no relevant lens change when accommodating at the nearpoint, however, under pharmacologically induced ciliary muscle contraction with pilocarpine, there was a significant forward shift of the anterior and posterior lens pole, leading to a translational forward lens shift of about 150 microm. This study demonstrates that pilocarpine acts "physiologically" in young phakic subjects, but is a "superstimulus" in presbyopic phakic subjects. Therefore, IOL movement may be overestimated when using pilocarpine to stimulate accommodation.     

Slit-lamp studies of the rhesus monkey eye: III. The zones of discontinuity

The rhesus monkey lens exhibits two zones of discontinuity, one anteriorly and one posteriorly. They are first discernible by slit-lamp photography as performed in this study at around age 7 years in iridectomized eyes, and become more distinct with increasing age. Their thickness and distance from each other along the polar axis are independent of lens age, but their distance from the lens surface increases with increasing age. Upon accommodation, the distance between the two zones increases while all other distances along the polar axis remain unchanged, indicating that, as in the human, overall alterations in rhesus lenticular shape and thickness with accommodation primarily reflect changes in the shape of the central region. The curvature of each zone becomes sharper in a linear fashion with accommodation, with the slope of the relationship being similar to those for lens surfaces.     

Accommodative changes in lens diameter in rhesus monkeys

PURPOSE: Some debate surrounds the accommodative mechanism in primates, particularly whether the lens equatorial diameter increases or decreases during accommodation. This study has been undertaken to measure the relationship between changes in lens diameter and refraction during accommodation in rhesus monkeys. METHODS: Photorefraction was used to measure accommodation, and goniovideography was used to measure accommodative changes in lens diameter in the iridectomized eyes of two rhesus monkeys. Accommodation was stimulated through the full amplitude available to each eye by stimulation of the Edinger-Westphal nucleus of the brain. Dynamic measurement of refractive changes followed by dynamic measurements of changes in lens diameter for the same stimulus current amplitudes allow the relationship between refraction and lens diameter to be determined. RESULTS: Lens diameter decreased relatively linearly during accommodation by 0.055 mm/diopter (D), resulting in an overall decrease in lens diameter of approximately 7% of the unaccommodated lens diameter for approximately 12 D of accommodation. CONCLUSIONS: The rhesus monkey lens diameter decreases systematically with the refractive change during accommodation in accordance with the Helmholtz accommodative mechanism and in contrast to the accommodative mechanism originally proposed by Tscherning.     

Aging changes in ocular tissues and their influences on accommodative functions

It is well known that the amplitude of accommodation deteriorates with aging. However, it is not clear what kinds of morphological changes of age-dependent deterioration of amplitude of accommodation accompany in the crystalline lens and the ciliary muscle, which are the most important involved tissues in the accommodation mechanism. In the present study morphological changes of these tissues were investigated in relation to the deterioration of the accommodative amplitude. Age-dependent deterioration of the subjective amplitude of accommodation obtained by an accommodometer (VDT Accommodometer NP-200, Toyo-Medical, Nagoya) and the objective amplitude by an autorefractometer with a built-in infrared optometer (NIDEK AA 2000 Accommodometer, NIDEK, Gamagori, Japan) were compared. The objective amplitude was 2-3 dptr less than the subjective amplitude for all ages, but change of both curves with aging were parallel. The crystalline lens measured by an ultrasonic A-scan instrument, Alpha 20/20 (Storz, U.S.A.), showed continuous increase in thickness with aging and by accommodative contraction. The crystalline lens in the fifties was as same in thickness as the accommodatively contracted lens in the twenties but the increasing ratio of lens thickness in accommodative contraction decreased with aging and it reached a minimum in the sixties. Scanning electron microscopy (JSM F-15, JOEL Co, Tokyo) revealed three types of characteristic substructures on the cell surface of the crystalline lens fiber, ie, interlocking protrusion, ball-and-socket junction and microplica or the tongue-and-groove junction. In the lenticular nucleus the microplica was prominent on the cell surface throughout all ages but the ball-and-socket junction was sparse in number. On the other hand, the ball-and-socket junction was well developed on the cell surface in the superficial cortex of the lens. The microplica on the cell surface in the superficial cortex was recognizable but indistinct. The microplica and ball-and-socket junction seemed to shift relative to each other in the deeper cortex of the lens. The interlocking protrusion was recognized throughout the whole lens, but was prominent in the lenticular nucleus. The crystalline lens fibers of advanced age were irregural in shape and the spherical substructure, large and small in size, and frequently formed suggesting the cataractous change. Delicate shift of the ciliary processes after conjunctival application of 4% pilocarpine was confirmed by an angioendoscope (Angio Fiber Imaging System FCA-8000. Fukuda Electronics K.K., Tokyo) which was inserted into the vitreous space of cynomorgus monkey eyes.(ABSTRACT TRUNCATED AT 400 WORDS)     

Age-related changes in human ciliary muscle and lens: a magnetic resonance imaging study

PURPOSE: To use high-resolution magnetic resonance (MR) images of the eye to directly measure the relationship between ciliary muscle contraction and lens response with advancing age. METHODS: A General Electric, 1.5-Tesla MR imager and a custom-designed eye imaging coil were used to collect high-resolution MR images from 25 subjects, 22 through 83 years of age. A nonmagnetic binocular stimulus apparatus was used to induce both relaxed accommodation (0.1 diopter [D]) and strong accommodative effort (8.0 D). Measurements of the ciliary muscle ring diameter (based on the inner apex), lens equatorial diameter, and lens thickness were derived from the MR images. RESULTS: Muscle contraction is present in all subjects and reduces only slightly with advancing age. A decrease in the diameter of the unaccommodated ciliary muscle ring was highly correlated with advancing age. Lens equatorial diameter does not correlate with age for either accommodative state. Although unaccommodated lens thickness (i.e., lens minor axis length) increases with age, the thickness of the lens under accommodative effort is only modestly age-dependent. CONCLUSIONS: Ciliary muscle contractile activity remains active in all subjects. A decrease in the unaccommodated ciliary muscle diameter, along with the previously noted increase in lens thickness (the "lens paradox"), demonstrates the greatest correlation with advancing age. These results support the theory that presbyopia is actually the loss in ability to disaccommodate due to increases in lens thickness, the inward movement of the ciliary ring, or both.     

The effect of cataract extraction on the contractility of ciliary muscle

PURPOSE: To evaluate the changes in the pilocarpine-induced contractility of the ciliary muscle in eyes with presbyopia before and after cataract extraction using ultrasound biomicroscopy (UBM). DESIGN: Prospective interventional case series. METHODS: A clear corneal phacoemulsification and posterior chamber intraocular lens (AcrySof SA60AT; Alcon Laboratories, Fort Worth, Texas, USA) was implanted in 23 eyes in 15 subjects. UBM was performed with and without instilling 2% pilocarpine, as well as before and two months after cataract extraction. The mean (+/- standard deviation) age was 65.33 +/- 6.09 years (range, 56 to 75 years). The increase in the axial length of the ciliary body (CBAXL) was used as a surrogate indicator of the centripetal ciliary muscle contraction during accommodation. Images of the ciliary body were compared visually using Adobe Photoshop 7.0 (Adobe Systems Inc., San Jose, California, USA). RESULTS: The CBAXL value with and without pilocarpine before cataract extraction was 1.708 +/- 0.165 mm and 1.689 +/- 0.187 mm, respectively, which was not significantly different (P = .261). The CBAXL value with and without pilocarpine after cataract extraction was 1.998 +/- 0.375 mm and 1.675 +/- 0.279 mm, respectively, which was significantly different (P < .001). The visually compared configurations of the changes in the ciliary body were compatible with the analysis of the measured parameters. CONCLUSIONS: Pilocarpine induced only subtle movement of the ciliary body before cataract surgery. However, after cataract extraction, it induced significant centripetal movement of the ciliary body compared with that without pilocarpine. This shows that a lenticular sclerotic component may influence both lens movement and the contractility of the ciliary muscle, and is believed to be related to the presbyopia.     

Role of accommodation in experimental myopia in chicks.

We compared the morphology of the accommodative apparatus in myopic and control chicks using light microscopy and scanning and transmission electron microscopy. Results indicate no significant difference in ciliary muscle and ciliary fold structure between control chick eyes and eyes in which at least 10 D of myopia was induced by the application of a translucent goggle. Based on the assumption that sustained tonic contraction of the accommodative apparatus in the myopic eye would lead to morphological differences, we conclude that the myopic eye is not accommodating excessively during development. These results, in combination with previous findings concerning the role of accommodation in experimental myopia, strongly indicate that accommodation does not play a significant role in this type of experimental myopia in chicks.     

Intraocular lens movement caused by ciliary muscle contraction

PURPOSE: To investigate intraocular lens (IOL) movement, measured as a change in anterior chamber depth (ACD) caused by pilocarpine-induced ciliary muscle contraction. SETTING: Department of Ophthalmology, University of Vienna, Vienna, Austria. METHODS: In this prospective study, the ACD was measured using high-precision, high-resolution, dual-beam partial coherence interferometry in 62 pseudophakic eyes of 55 patients under pilocarpine- and cyclopentolate-induced ciliary muscle contraction and relaxation. The following were studied: 2 models of a ring-haptic IOL (designed to accommodate), a plate-haptic IOL, and 3 types of 3-piece IOLs. Measurements were performed 3 months after surgery. RESULTS: The ring-haptic IOLs and plate-haptic IOL showed a forward movement (ring haptic 43A, -116 microm; ring haptic 43E, -222 microm; plate haptic -162 microm). The 3-piece IOLs showed no change in ACD except in 1 IOL type in which there was backward movement (156 microm). CONCLUSIONS: Pilocarpine-induced ciliary muscle contraction caused forward movement of ring- and plate-haptic IOLs that resulted in an estimated accommodative amplitude of less than 0.50 diopter in most cases. The accommodating ring-haptic IOLs did not perform better than the conventional plate-haptic IOL.