Ciliary muscle and anterior segment characteristics in pre-presbyopic adults with Down syndrome

PURPOSE

Previous research has shown that accommodation deficits are common in individuals with Down syndrome (DS), but the origin and mechanisms behind these deficits are still unknown. The aim of this study was to investigate the characteristics of different ocular structures involved in accommodation, in particular the ciliary muscle (CM), in a population of individuals with DS to further understand this deficit and its mechanisms.

METHODS

Thirty-two volunteer participants of pre-presbyopic age with (n = 16) and without DS (n = 16) were recruited. Temporal and nasal images of the CM were acquired using anterior segment optical coherence tomography (AS-OCT) while participants fixated an eccentrically located target. Analysis of CM parameters was undertaken using validated semi-automated software. Axial length, anterior chamber depth, lens thickness and corneal curvature were obtained with the Topcon Aladdin Optical Biometer and Corneal Topographer. Non-cycloplegic refractive error and accommodative ability were obtained with an open-field autorefractor and dynamic retinoscopy, respectively. Independent t-tests were conducted to determine differences in CM and other anterior segment parameters between participants with and without DS.

RESULTS

No significant differences were found in the CM parameters studied between participants with and without DS (p > 0.05). In contrast, significant differences were found in visual acuity (p < 0.001), accommodative response (p < 0.001) and corneal curvature (K1 p = 0.003 and K2 p < 0.001) between participants with and without DS.

CONCLUSIONS

Despite having poorer accommodation, pre-presbyopic adults with DS do not have a different CM morphology to that found in typically developing adults. These findings suggest that the accommodative deficit found in this population is not due to a mechanical deficit of the CM.

Impact of accommodative insufficiency and accommodative/vergence therapy on ciliary muscle thickness in the eye

PURPOSE

Recent evidence suggests that the ciliary muscle apical fibres are most responsive to accommodative load; however, the structure of the ciliary muscle in individuals with accommodative insufficiency is unknown. This study examined ciliary muscle structure in individuals with accommodative insufficiency (AI). We also determined the response of the ciliary muscle to accommodative/vergence therapy and increasing accommodative demands to investigate the muscle's responsiveness to workload.

METHODS

Subjects with AI were enrolled and matched by age and refractive error with subjects enrolled in another ciliary muscle study as controls. Anterior segment optical coherence tomography was used to measure the ciliary muscle thickness (CMT) at rest (0D), maximum thickness (CMTMAX) and over the area from 0.75 mm (CMT0.75) to 3 mm (CMT3) posterior to the scleral spur of the right eye. For those with AI, the ciliary muscle was also measured at increasing levels of accommodative demand (2D, 4D and 6D), both before and after accommodative/vergence therapy.

RESULTS

Sixteen subjects with AI (mean age = 17.4 years, SD = 8.0) were matched with 48 controls (mean age = 17.8 years, SD = 8.2). On average, the controls had 52-72 μm thicker ciliary muscles in the apical region at 0D than those with AI (p = 0.03 for both CMTMAX and CMT 0.75). Differences in thickness between the groups in other regions of the muscle were not statistically significant. After 8 weeks of accommodative/vergence therapy, the CMT increased by an average of 22-42 μm (p ≤ 0.04 for all), while AA increased by 7D (p < 0.001).

CONCLUSIONS

This study demonstrated significantly thinner apical ciliary muscle thickness in those with AI and that the ciliary muscle can thicken in response to increased workload. This may explain the mechanism for improvement in signs and symptoms with accommodative/vergence therapy.

Intraocular accommodative movements in monkeys; relationship to presbyopia

Our goal was to quantify the age-related changes in the dynamic accommodative movements of the vitreous and aqueous humor in iridic, aniridic, phakic and aphakic primate eyes. Six bilaterally iridic and four bilaterally iridectomized rhesus monkeys, ranging in age from 6 to 25 years, received a stimulating electrode in the midbrain Edinger-Westphal nucleus to induce accommodation, measured by a Hartinger coincidence refractometer. One of the four iridectomized monkeys underwent unilateral extracapsular and another monkey underwent intracapsular lens extraction. Eyes were imaged utilizing specialized techniques and contrast agents to resolve intraocular structures. During accommodation the anterior hyaloid membrane and the posterior lens capsule bowed backward. Central vitreous fluid and structures/strands moved posteriorly toward the optic nerve region as peripheral vitreous, attached to the vitreous zonule, was pulled forward by ciliary muscle contraction. Triamcinolone particles injected intravitreally were also observed in the anterior chamber and moved from the anterior chamber toward the cleft of the anterior hyaloid membrane and then further posteriorly into the vitreous-filled cleft between the vitreous zonule and the ciliary body pars plana. These accommodative movements occurred in all eyes, and declined with age. There are statistically significant accommodative movements of various intravitreal structures. The posterior/anterior fluid flow between the anterior chamber and the vitreous compartments during accommodation/disaccommodation represents fluid displacement to allow/facilitate lens thickening. The posterior accommodative movement of central vitreous fluid may result from centripetal compression of the anterior tips of the cistern-like structure attached to the vitreous zonule, and posterior displacement of the central trunk of the cistern during ciliary muscle contraction and centripetal muscle movement. The findings may have implications for presbyopia.

Effect of age in the ciliary muscle during accommodation: Sectorial analysis

PURPOSE

To compare changes in the ciliary muscle area at different sectors between pre-presbyopic and presbyopic eyes during accommodation by means of an anterior segment optical coherence tomographer (OCT).

METHODS

The anterior ciliary muscle area was measured in 20 healthy and phakic pre-presbyopic eyes, whose mean age was 23.3±4.4 years, and in 20 healthy and phakic presbyopic eyes, whose mean age was 46.5±5.2 years. The relative change in the cross-sectional area of the ciliary muscle was measured at the nasal, inferior, and temporal sectors between 0 and -3 D of vergence, in -1 D step. A linear model was used to assess the correlation of each eye parameter with the accommodative demand.

RESULTS

Each population group showed a significant increase in the anterior ciliary muscle area for each sector. The maximum increase in the ciliary muscle area within the pre-presbyopic group was about 30%, and for the presbyopic one was about 25%. At the same time, it was obtained that the larger the vergence, the larger the variability. Furthermore, the linear model showed a positive tendency between the change in the ciliary muscle area of each sector and the vergence for both population groups, which coefficient of determination was in all cases greater than 0.93.

CONCLUSION

The anterior ciliary muscle area tends to increase with accommodation. The presbyopic nasal, inferior, and temporal ciliary muscle seem to have the same contractile capability as the young presbyopic ciliary muscle. These results might help to increase the evidences in the knowledge regarding the modern understanding of accommodation biometry and biomechanics.

Age-related posterior ciliary muscle restriction - A link between trabecular meshwork and optic nerve head pathophysiology

The ciliary muscle plays a major role in controlling both accommodation and outflow facility in primates. The ciliary muscle and the choroid functionally form an elastic network that extends from the trabecular meshwork all the way to the back of the eye and ultimately attaches to the elastic fiber ring that surrounds the optic nerve and to the lamina cribrosa through which the nerve passes. The ciliary muscle governs the accommodative movement of the elastic network. With age ciliary muscle mobility is restricted by progressively inelastic posterior attachments and the posterior restriction makes the contraction progressively isometric; placing increased tension on the optic nerve region. In addition, outflow facility also declines with age and limbal corneoscleral contour bows inward. Age-related loss in muscle movement and altered limbal corneoscleral contour could both compromise the basal function of the trabecular meshwork. Further, recent studies in non-human primates show that the central vitreous moves posteriorly all the way back to the optic nerve region, suggesting a fluid current and a pressure gradient toward the optic nerve. Thus, there may be pressure and tension spikes on the optic nerve region during accommodation and these pressure and tension spikes may increase with age. This constellation of events could be relevant to glaucomatous optic neuropathy. In summary, our hypothesis is that glaucoma and presbyopia may be literally linked to each other, via the choroid, and that damage to the optic nerve may be inflicted by accommodative intraocular pressure and choroidal tension "spikes", which may increase with age.

Safety of Using Matrix Metalloproteinase Inhibitor in Experimental Glaucoma Filtration Surgery

We evaluated the safety of matrix metalloproteinase (MMP) inhibitor in experimental glaucoma filtration surgery in an animal model. Fifteen New Zealand white rabbits underwent an experimental trabeculectomy and were randomly allocated into 3 groups according to the adjuvant agent: no treatment group (n = 5), 0.02% mitomycin C (MMC) soaking group (n = 5), and MMP inhibitor (ilomastat) subconjunctival injection group (n = 5). Slit lamp examination with Seidel testing, pachymetry, and specular microscopy was performed preoperatively and postoperatively. The conjunctiva and ciliary body toxicity were evaluated with scores according to the pathologic grading systems. Electron microscopy was used to examine the structural changes in cornea, conjunctiva, and ciliary body. In the ilomastat-treated group, there was no statistically significant change in central corneal thickness preoperatively and at 28 days postoperatively (P = 0.655). There were also no significant changes in specular microscopy findings over the duration of the study in the ilomastat-treated group. The conjunctival toxicity score was 1 in the control group, 1.5 in the ilomastat-treated group, and 2 in the MMC-treated group. When assessing ciliary body toxicity scores, the ilomastat-treated group score was 0.5 and the MMC-treated group score was 1.5. Transmission electron microscopy did not show structural changes in the cornea and ciliary body whereas the structural changes were noticed in MMC group. A single subconjunctival injection of MMP inhibitor during the experimental trabeculectomy showed a less toxic affect in the rabbit cornea, conjunctiva, and ciliary body compared to MMC.

Functional Anatomy of the Outflow Facilities

In order to understand the pathophysiology, select optimal therapeutic options for patients and provide clients with honest expectations for cases of canine glaucoma, clinicians should be familiar with a rational understanding of the functional anatomy of the ocular structures involved in this group of diseases. The topographical extension and the structural and humoral complexity of the regions involved with the production and the outflow of aqueous humor undergo numerous changes with aging and disease. Therefore, the anatomy relative to the fluid dynamics of aqueous has become a pivotal yet flexible concept to interpret the different phenotypes of glaucoma.

Physiological constraints for an intraocular inductive distance sensor

In this paper the design restrictions of an inductive sensor for an intraocular lens with focus control on the basis of a marker implanted in the ciliary muscle of the eye are discussed in the framework of anatomical and physiological influences and constraints: limitations on the marker size, influences of tissue conduction and effects of off-axis implantation of the marker with respect to the coil.

Bringing accommodation into focus: the several discoveries of the ciliary muscle

Since at least the 16th century, many investigators have speculated on the presence of a specialized muscle in the front of the eye designed to somehow alter its disposition to bring about changes in focus. By the 1850s, when Hermann von Helmholtz offered the first plausible theory of accommodation, the anatomy of the ciliary muscle was well known. The credit for this knowledge is generally given to Ernst Brücke and William Bowman, who published their observations on the muscle independently in the 1840s. In fact, not only were Bowman and Brücke wrong about the role of the ciliary muscle in accommodation, and for different reasons, but they shared this distinction with at least 3 investigators who came before them. In the 3 decades before 1840, Philip Crampton, Robert Knox, and William Wallace had all zeroed in on the ciliary muscle, describing its anatomy in varying detail. If none understood its precise role in accommodation--all ignored the work of Thomas Young, who by 1800 had proved that the lens must somehow round up to achieve near vision--each deserves a share of the credit for its discovery.

Effect of cAMP on short-circuit current in isolated human ciliary body

BACKGROUND

Cyclic adenosine monophosphate (cAMP) could activate chloride channels in bovine ciliary body and trigger an increase in the ionic current (short-circuit current, Isc) across the ciliary processes in pigs. The purpose of this study was to investigate how cAMP modulates Isc in isolated human ciliary processes and the possible involvement of chloride transport across the tissue in cAMP-induced Isc change.

METHODS

In an Ussing-type chamber system, the Isc changes induced by the cAMP analogue 8-bromo-cAMP and an adenylyl cyclase activator forskolin in isolated human ciliary processes were assessed. The involvement of Cl(-) component in the bath solution was investigated. The effect of Cl(-) channel (10 µmol/L niflumic acid and 1 mmol/L 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)), K(+) channel (10 mmol/L tetraethylammonium chloride (TEA)), or Na(+) channel blockers (1 mmol/L amiloride) on 8-bromo-cAMP-induced Isc change was also studied.

RESULTS

Dose-dependently, 8-bromo-cAMP (10 nmol/L-30 µmol/L) or forskolin (10 nmol/L-3 µmol/L) increased Isc across the ciliary processes with an increase in negative potential difference on the non-pigmented epithelium (NPE) side of the tissue. Isc increase induced by 8-bromo-cAMP was more pronounced when the drug was applied on the NPE side than on the pigmented epithelium side. When the tissue was bathed in low Cl(-) solutions, the Isc increase was significantly inhibited. Finally, niflumic acid and DIDS, but not TEA or amiloride, significantly prevented the Isc increase induced by 8-bromo-cAMP.

CONCLUSIONS

cAMP stimulates stroma-to-aqueous anionic transport in isolated human ciliary processes. Chloride is likely to be among the ions, the transportation of which across the tissue is triggered by cAMP, suggesting the potential role of cAMP in the process of aqueous humor formation in human eyes.

Intraocular electro-optic lens with ciliary muscle controlled accommodation

In this paper a concept is proposed of an intraocular lens implant with electro-optic accommodation of a variable-focus hybrid liquid-crystal-based lens. The dioptric strength of the lens is electronically controlled by a signal that is derived from the change of inductance of a sensing coil due to a marker implanted in the nearby contracting or decontracting ciliary muscle. Analytical, numerical and experimental results are reported on the dependency of the frequency of a Colpitts oscillator circuit on the location of a nearby conductive marker. A concept is also reported on the use as an electro-optic lens of a device based on a liquid crystal in planar alignment, which is held between a flat and a curved window coated with optically transparent and electrically conductive layers.

ARL13B, PDE6D, and CEP164 form a functional network for INPP5E ciliary targeting

Mutations affecting ciliary components cause a series of related genetic disorders in humans, including nephronophthisis (NPHP), Joubert syndrome (JBTS), Meckel-Gruber syndrome (MKS), and Bardet-Biedl syndrome (BBS), which are collectively termed "ciliopathies." Recent protein-protein interaction studies combined with genetic analyses revealed that ciliopathy-related proteins form several functional networks/modules that build and maintain the primary cilium. However, the precise function of many ciliopathy-related proteins and the mechanisms by which these proteins are targeted to primary cilia are still not well understood. Here, we describe a protein-protein interaction network of inositol polyphosphate-5-phosphatase E (INPP5E), a prenylated protein associated with JBTS, and its ciliary targeting mechanisms. INPP5E is targeted to the primary cilium through a motif near the C terminus and prenyl-binding protein phosphodiesterase 6D (PDE6D)-dependent mechanisms. Ciliary targeting of INPP5E is facilitated by another JBTS protein, ADP-ribosylation factor-like 13B (ARL13B), but not by ARL2 or ARL3. ARL13B missense mutations that cause JBTS in humans disrupt the ARL13B-INPP5E interaction. We further demonstrate interactions of INPP5E with several ciliary and centrosomal proteins, including a recently identified ciliopathy protein centrosomal protein 164 (CEP164). These findings indicate that ARL13B, INPP5E, PDE6D, and CEP164 form a distinct functional network that is involved in JBTS and NPHP but independent of the ones previously defined by NPHP and MKS proteins.

Nifedipine enhances the relaxant effects of cyclo-oxygenase inhibitors on the bovine ciliary muscle

BACKGROUND/AIMS

The inhibition of cyclo-oxygenase (COX) enzymes and the blockade of Ca (2+) channels play an important role in the regulation of smooth muscle relaxation. This study was designed to investigate the relaxant effects of celecoxib, DFU (5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2(5H)-furanone), and indomethacin, cyclo-oxygenase (COX-1 and -2) inhibitors, in the absence or presence of a nifedipine, L-type Ca(2+) channel blocker, on bovine ciliary muscle.

METHODS

Ciliary muscle strips (n = 12) were mounted in organ baths and tested for changes in isometric tension in response to celecoxib, DFU, and indomethacin. The relaxant effects of celecoxib, DFU, and indomethacin on carbachol-induced contractions in the presence or absence of nifedipine were investigated.

RESULTS

Celecoxib (10(-7)-10(-4) M), DFU (10(-7)-10(-4) M), indomethacin (10(-7)-10(-4) M), and nifedipine (10(-7)-10(-4) M) inhibited the carbachol-induced contractions in a concentration-dependent manner. The E(max) value of indomethacin was significantly higher than the E(max) values of celecoxib and DFU in ciliary muscle (P < 0.05), with no significant change in pD(2) values (P > 0.05). The relaxation responses by celecoxib, DFU, and indomethacin were significantly increased in the presence of nifedipine (10(-6) M). There were no significant differences between pEC50 and values of celecoxib, DFU, and indomethacin in the absence of nifedipine (10(-6) M) (P > 0.05), but E(max)values were significantly increased (P < 0.05).

CONCLUSIONS

These results suggest that the celecoxib, DFU, and indomethacin cause relaxation in ciliary muscle precontracted with carbachol. Blockade of calcium channels with nifedipine in ciliary muscle may increase the relaxant effect of celecoxib, DFU, and indomethacin. The topical or systemic use of celecoxib, DFU, and indomethacin with nifedipine can cause blurred near vision due to ciliary muscle relaxation, and in ocular pain conditions caused by ciliary spasm, the pain can be decreased more easily by combined use of these drugs.

Voltage-gated potassium channel Kv1.3 in rabbit ciliary epithelium regulates the membrane potential via coupling intracellular calcium

BACKGROUND

The cell layer of the ciliary epithelium is responsible for aqueous humor secretion and maintenance. Ion channels play an important role in these processes. The main aim of this study was to determine whether the well-characterized members of the Kv1 family (Kv1.3) contribute to the Kv currents in ciliary epithelium.

METHODS

New Zealand White rabbits were maintained in a 12 hours light/dark cycle. Ciliary epithelium samples were isolated from the rabbits. We used Western blotting and immunocytochemistry to identify the expression and location of a voltage-gated potassium channel Kv1.3 in ciliary body epithelium. Membrane potential change after adding of Kv1.3 inhibitor margatoxin (MgTX) was observed with a fluorescence method.

RESULTS

Western blotting and immunocytochemical studies showed that the Kv1.3 protein expressed in pigment ciliary epithelium and nonpigment ciliary epithelium, however it seemed to express more in the apical membrane of the nonpigmented epithelial cells. One nmol/L margatoxin, a specific inhibitor of Kv1.3 channels caused depolarization of the cultured nonpigmented epithelium (NPE) membrane potential. The cytosolic calcium increased after NPE cell depolarization, this increase of cytosolic calcium was partially blocked by 12.5 micromol/L dantrolene and 10 micromol/L nifedipine. These observations suggest that Kv1.3 channels modulate ciliary epithelium potential and effect calcium dependent mechanisms.

CONCLUSION

Kv1.3 channels contribute to K+ efflux at the membrane of rabbit ciliary epithelium.

Species variation in biology and physiology of the ciliary epithelium: similarities and differences

Glaucoma is a leading cause of irreversible blindness worldwide. Lowering intraocular pressure (IOP) is the only strategy documented to delay the appearance and retard the progression of vision loss. One major approach for lowering IOP is to slow the rate of aqueous humor formation by the ciliary epithelium. As discussed in the present review, the transport basis for this secretion is largely understood. However, several substantive issues are yet to be resolved, including the integrated regulation of secretion, the functional topography of the ciliary epithelium, and the degree and significance of species variation in aqueous humor inflow. This review discusses species differences in net secretion, particularly of Cl(-) and HCO(3)(-) secretion. Identifying animal models most accurately mimicking aqueous humor formation in the human will facilitate development of future novel initiatives to lower IOP.

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.

[Association between iris color and ciliary body pigmentation: possible implications for cyclophotoablation treatment]

BACKGROUND

Cyclophotoablation for glaucoma treatment is dependent on the amount of laser energy absorbed by the ciliary body and related to the degree of its pigmentation. Iris color may be assessed by observing the eye, but it is unknown whether it correlates with ciliary body pigmentation.

AIM

We evaluated whether ciliary pigmentation correlates with iris color.

METHODS

The pigmented epithelium of the ciliary processes of 31 enucleated eyes was qualitatively scored for six histological parameters and correlated with iris color.

RESULTS

The dark iris group (n = 19) had significantly increased histological parameters of pigmentation such as aggregation of melanosomes, compared to the light iris group (n = 12) (p < 0.01).

CONCLUSION

Iris color correlates with ciliary pigmentation and may serve as one of the factors determining laser power needed for cyclophotoablation.

Evidence for the involvement of cannabinoid CB1 receptors in the bimatoprost-induced contractions on the human isolated ciliary muscle

PURPOSE

To evaluate the bimatoprost effects in the isolated human ciliary muscle and to assess how these response can be modulated by AL8810 and SR141716A.

METHODS

In a myograph system (isometric force measurement), ciliary muscles were exposed cumulatively to PGF(2alpha), latanoprost, travoprost, bimatoprost, and anandamide (0.1 nM-10 microM). Experiments were also conducted in the presence of AL8810 (FP receptor antagonist; 100 nM) or SR141716A (CB(1) receptor antagonist; 10-100 nM). Contractions were expressed as the percentage of 10 microM carbachol-induced contractions.

RESULTS

In quiescent tissues, concentration-response curves for bimatoprost, anandamide, PGF(2alpha,) latanoprost, and travoprost were constructed. Bimatoprost showed an important contractile effect on isolated human ciliary muscle strips (E(max) = 125% +/- 0.09%); the maximal effect was higher than that obtained with carbachol. Contractions were inhibited by SR141716A (10 and 100 nM) and AL8810 (100 nM).

CONCLUSIONS

This study showed evidence of direct interaction of bimatoprost with the contractility of the human ciliary muscle through interaction with cannabinoid CB(1) receptor and prostanoid FP receptors.

Optomechanical response of human and monkey lenses in a lens stretcher

PURPOSE

To quantify the forces necessary to change the shape and optical power of human and monkey lenses.

METHODS

Cynomolgus monkey (n = 48; age: 3.8-11 years), rhesus monkey (n = 35; age: 0.7-17 years) and human (n = 20, age 8-70 years) eyes obtained postmortem, including the lens, capsule, zonules, ciliary body, and sclera were mounted in an optomechanical lens-stretching system. Starting at zero load, the lenses were symmetrically stretched in a stepwise fashion in 0.25- or 0.5-mm steps. The load, lens diameter, inner ciliary body diameter, and lens power were measured at each step and the diameter- and power-load responses were quantified.

RESULTS

The diameter- and power-load responses were found to be linear in the physiologically relevant range of stretching. The average change in cynomolgus, rhesus, and human lens diameter, respectively, was 0.094, 0.109, and 0.069 mm/g in young lenses, and 0.069, 0.067, and 0.036, mm/g in older lenses. For the same lenses, the average change in lens power was -3.73, -2.83, and -1.22 D/g in young lenses and -2.46, -2.16, and -0.49 D/g in older lenses.

CONCLUSIONS

The force necessary to change the lens diameter and lens power increases with age in human and monkey lenses. The results agree with the Helmholtz theory of accommodation and with presbyopia theories that predict that the force required to disaccommodate the lens increases with age.

Fibroblast growth factor-hedgehog interdependence during retina regeneration

The embryonic chick is able to regenerate the retina after it has been removed. We have previously shown that proliferating stem/progenitor cells present in the ciliary body/ciliary marginal zone (CB/CMZ) of the chick eye are responsible for regeneration, which can be induced by ectopic fibroblast growth factor-2 (FGF2) or Sonic hedgehog (Shh). Here, we reveal the mechanisms showing how FGF2 and Shh signaling are interdependent during retina regeneration. If the FGF pathway is inhibited, regeneration stimulated by Shh is inhibited. Likewise, if the Hedgehog pathway is inhibited, regeneration stimulated by FGF2 is inhibited. We examined early signaling events in the CB/CMZ and found that FGF2 or Shh induced a robust Erk phosphorylation during the early stages of retina regeneration. Shh also up-regulated the expression of several members of the FGF signaling pathway. We show that ectopic FGF2 or Shh overexpression increased the number of phosphohistone 3 (PH3)-positive cells in the CB/CMZ and inhibition of either pathway decreased the number of PH3-positive cells. Additionally, both FGF and Hh signaling are required for cell survival in the CB/CMZ, whereas Hh and not FGF signaling plays a role in maintaining the identity of the retinal progenitor population in this region. Combined, our results support a model where the FGF and Hedgehog pathways work together to stimulate retina regeneration.

[Expression of regulatory and tissue-specific genes controlling regenerative potencies of the eye tissues in vertebrates]

Comparative analysis of the early transformations of differentiated cells of the pigment epithelium, ciliary fold epithelium, and Muller glia in the eye of lower vertebrates and mammals during retina regeneration and cultivation was performed for the first time. Dedifferentiation and proliferation of cells and formation of progenitor multipotent cells, which are a source of retina regeneration in adult newts, were characterized using cell, molecular, and genetic markers. Neurospheres were formed during cultivation of the differentiated cells, in which progenitor multipotent cells were found that transformed into neurons of retina and brain and into glial cells. Comparative analysis of changes in the pigment epithelium cells during retina regeneration and during cultivation of differentiated cells of the pigment and ciliary epithelia and Muller glia suggests similar cell transformations at the early stages of transdifferentiation.

Characteristics of Progenitor Cells Derived from Adult Ciliary Body in Mouse, Rat, and Human Eyes

PURPOSE

To isolate and characterize progenitor cells derived from adult mammalian ciliary body.

METHODS

The authors isolated progenitor cells from the ciliary body of adult mice, rats, and human cadaver eyes and determined quantitative growth characteristics of groups of progenitor cells called neurosphere (NS) cells, including individual cell diameter, NS diameter, percentage of NS-forming cells, and cell number per eye in mouse, rat, and human eyes. The immunolabeling and ultrastructure of NS cells were investigated by confocal and transmission electron microscopy.

RESULTS

Average diameters of individual cells and neurospheres after 1 week in culture were similar in mice, rats, and humans (cell diameters: 22 +/- 1.1, 21 +/- 0.3, 25 +/- 0.4 mum; NS diameters: 139 +/- 22, 137 +/- 9, 141 +/- 11 mum, respectively). Mean numbers of cells per NS were estimated to be 1183 in mice, 5360 in rats, and 685 in humans. Molecules that were identified by immunolabeling in NS cells included nestin, Chx-10, vimentin, GFAP, and Pax-6. Thy-1 was expressed in some NS cells. Ultrastructurally, NS cells displayed abundant rough endoplasmic reticulum and many cellular processes but no characteristics of mature retinal neurons or glia.

CONCLUSIONS

Progenitor cells from adult mammalian ciliary body have significant, but limited, proliferation potential and express markers characteristic of other progenitor cells and seen during early retinal development. The ciliary body could be a source of cells for transplantation in experimental rodent eyes and for autotransplantation in human eyes.

[Relationship between ciliary muscle contraction and the pseudo accommodation after the implantation of foldable intraocular lenses]

OBJECTIVE

To investigate the relationship between high frequency component of accommodative microfluctuation (HFC) and the pseudo accommodation after the implantation of foldable intraocular lenses (IOL).

METHODS

With ARK-730A accommodation analyzer we checked HFC in 50 cases (50 eyes) of patients who had good pupil reaction to light and the pupil diameter was 2.0 approximately 3.5 mm approximately. Three months after the implantation of foldable IOL, the relationship among ciliary muscle accommodative microfluctuation, IOL movement and pseudo accommodation was analyzed.

RESULTS

There was positive correlation between ciliary muscle accommodative microfluctuation and IOL movement (r = 0.702, P < 0.01), between IOL movement and pseudo accommodation (r = 0.861, P < 0.01), and between ciliary muscle accommodative microfluctuation and pseudo accommodation (r = 0.915, P < 0.01). Pseudo accommodation was greater in patients who showed more ciliary muscle accommodative microfluctuation and IOL movement.

CONCLUSION

HFC induces IOL movement, and it is one of the most important reasons for pseudo accommodation after foldable IOL implantation.

Edinger-Westphal and pharmacologically stimulated accommodative refractive changes and lens and ciliary process movements in rhesus monkeys

During accommodation, the refractive changes occur when the ciliary muscle contracts, releasing resting zonular tension and allowing the lens capsule to mold the lens into an accommodated form. This results in centripetal movement of the ciliary processes and lens edge. The goal of this study was to understand the relationship between accommodative refractive changes, ciliary process movements and lens edge movements during Edinger-Westphal (EW) and pharmacologically stimulated accommodation in adolescent rhesus monkeys. Experiments were performed on one eye each of three rhesus monkeys with permanent indwelling electrodes in the EW nucleus of the midbrain. EW stimulated accommodative refractive changes were measured with infrared photorefraction, and ciliary process and lens edge movements were measured with slit-lamp goniovideography on the temporal aspect of the eye. Images were recorded on the nasal aspect for one eye during EW stimulation. Image analysis was performed off-line at 30 Hz to determine refractive changes and ciliary body and lens edge movements during EW stimulated accommodation and after carbachol iontophoresis to determine drug induced accommodative movements. Maximum EW stimulated accommodation was 7.36+/-0.49 D and pharmacologically stimulated accommodation was 14.44+/-1.21 D. During EW stimulated accommodation, the ciliary processes and lens edge moved centripetally linearly by 0.030+/-0.001 mm/D and 0.027+/-0.001 mm/D, with a total movement of 0.219+/-0.034 mm and 0.189+/-0.023 mm, respectively. There was no significant nasal/temporal difference in ciliary process or lens edge movements. 30-40 min after pharmacologically stimulated accommodation, the ciliary processes moved centripetally a total of 0.411+/-0.048 mm, or 0.030+/-0.005 mm/D, and the lens edge moved centripetally 0.258+/-0.014 mm, or 0.019+/-0.003 mm/D. The peaks and valleys of the ciliary processes moved by similar amounts during both supramaximal EW and pharmacologically stimulated accommodation. In conclusion, this study shows, for the first time, that the ciliary processes and lens edge move centripetally, linearly with refraction during EW stimulated accommodation. During pharmacological stimulation, the ciliary processes move to a greater extent than the lens edge, confirming that in adolescent monkeys, lens movement limits the accommodative optical change in the eye.

Relaxant effects of β-adrenoceptor agonist formoterol and BRL 37344 on bovine iris sphincter and ciliary muscle

We investigated the relaxant effect of beta2-adrenoceptor agonist formoterol and beta3-adrenoceptor agonist BRL 37344 on bovine iris sphincter and ciliary muscle and measured cAMP and cGMP levels. Iris sphincter (n = 16) and ciliary muscle (n = 16) strips were mounted in organ baths and tested for changes in isometric tension in response to formoterol and BRL 37344. Their relaxant effects on serotonin-induced contractions in the presence or absence of metoprolol, ICI 118.551 and SR 59230A (beta1-, beta2-, beta3-adrenoceptor antagonist, respectively) were investigated. Their effects on cAMP and cGMP levels in iris sphincter (n = 12) and ciliary muscle (n = 12) were evaluated. Formoterol (10(-11)-10(-5) M) and BRL 37344 (10(-10)-10(-5) M) decreased the serotonine-induced contractions in a concentration-dependent manner. Emax values of formoterol were significantly higher than those of BRL 37344 in iris sphincter and ciliary muscle, with no significant change in pD2 values. The relaxation responses by formoterol and BRL 37344 were antagonized with ICI 118.551 (10(-6) M) and SR 59230A (10(-6) M). cAMP levels of formoterol- and BRL 37344-treated tissues were significantly higher than those of the control tissues. cGMP levels of BRL 37344-treated tissues were significantly higher than those of control tissues, but this effect of BRL 37344 was less significant than its effect on cAMP levels. beta-adrenoceptor relaxation responses in bovine iris sphincter and ciliary muscle are mediated by a mixed population of beta2- and beta3-adrenoceptor subtypes, with a predominant contribution of cAMP. Potency of formoterol and BRL 37344 was similar, but efficacy of formoterol was better than BRL 37344.

Accommodating intraocular lenses: a critical review of present and future concepts

BACKGROUND

Significant efforts have been made to develop lens implants or refilling procedures that restore accommodation. Even with monofocal implants, apparent or pseudoaccommodation may provide the patient with substantial though varying spectacle independence. True pseudophakic accommodation with a change of overall refractive power of the eye may be induced either by an anterior shift or a change in curvature of the lens optic.

MATERIALS AND METHODS

Passive-shift lenses were designed to move forward under ciliary muscle contraction. This is the only accommodative lens type currently marketed (43E/S by Morcher; 1CU by HumanOptics; AT-45 by Eyeonics). The working principle relies on various hypothetical assumptions regarding the mechanism of natural accommodation. Dual-optic lenses were designed to increase the dioptric impact of optic shift. They consist of a mobile front optic and a stationary rear optic which are interconnected with spring-type haptics. With active-shift lens systems the driving force is provided by repulsing mini-magnets. Lens refilling procedures replace the lens content by an elastic material and provide accommodation by an increase of surface curvature.

RESULTS

Findings with passive-shift lenses have been contradictory. While uncorrected reading vision results were initially reported to be favorable with the 1CU, and excellent with the AT-45 lens, distant-corrected near vision did not exceed that with standard monofocal lenses in later studies. Mean axial shift from laser interferometric measurements under stimulation with pilocarpine showed a moderate anterior shift with the 1CU, while the AT-45 paradoxically exhibited a small posterior shift. With the 1CU, the shift-induced accommodative effect was calculated to be less than +0.5 D in most cases, while +1 D was achieved in a single case only. Ranges and standard deviations were very large in relation to the mean values. Under physiological near-point stimulation, however, no shift was seen at all. Prevention of capsule fibrosis by extensive capsule polishing did not enhance the functional performance. Dual optic lenses are under clinical investigation and are reported to provide a significant amount of accommodation. However, possible long-term formation of interlenticular opacifications remains to be excluded. Regarding magnet-driven active-shift lens systems, initial clinical experience has been promising. Prevention of fibrotic capsular contraction is crucial, and it has been effectively counteracted with a special capsular tension ring, or lens fixation technique, together with capsule polishing. Lens refilling has been extensively studied in the laboratory and in primates. Though it offers great potential for fully restoring accommodation, a variety of problems must be solved, such as achieving emmetropia in the relaxed state, adequate response to ciliary muscle contraction, satisfying image quality over the entire range of accommodation and sustained functioning. The key problem, however, is again after-cataract prevention.

CONCLUSIONS

As opposed to psychophysical evaluation techniques, laser interferometry measures what shift lenses are designed to provide: axial shift on accommodative effort. While under pilocarpine some movement was recorded, no movement at all was found under near-point stimulation with any of the lenses currently marketed. In contrast, magnetic-driven active-shift lens systems carry the potential of sufficiently topping up apparent accommodation to provide for clinically useful accommodation while using conventional lens designs with proven after-cataract performance. Dual optic implants significantly increase the impact of axial optic shift. The main potential problem, however, is delayed formation of interlenticular regenerates. Lens refilling procedures offer the potential of fully restoring accommodation due to the great impact of increase in surface curvature on refractive lens power. However, various problems remain to be solved before clinical use can be envisaged, above all, again, after-cataract prevention. The concept of passive single-optic shift lenses has failed. Concomitant poor capsular bag performance makes these lenses an unacceptable trade-off. Magnet-assisted systems potentially combine clinically useful accommodation with satisfactory after-cataract performance. Dual optic lenses theoretically offer substantial accommodative potential but may allow for interlenticular after-cataract formation. Lens refilling procedures have the greatest potential for fully restoring natural accommodation, but will again require years of extensive laboratory and animal investigations before they may function in the human eye.

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.

Age-related behavior of posterior chamber lenses in myopic phakic eyes during accommodation measured by anterior segment partial coherence interferometry

PURPOSE

To evaluate age-related position shifts of the crystalline lens and the implantable contact lens (ICL, Staar Surgical) by a new, commercially available, anterior segment partial coherence interferometer, the ACMaster (Carl Zeiss Meditec), during accommodation in myopic eyes.

SETTING

ALZ Augenklinik, Munich, Germany.

METHODS

Fifty-three eyes of 29 consecutive patients were measured after myopic ICL implantation before and during subjective accommodation to a stimulus of 3 diopters (D) by anterior segment partial coherence interferometry (PCI). Nine eyes were also measured with a 5.00 diopters (D) stimulus; 14 eyes were measured repeatedly at different visits. The mean patient age was 33 years +/- 9 (SD) (range 21 to 59 years). The preoperative mean sphere was -7.6 +/- 1.9 D (range -5.0 to -11.5 D) and the cylinder, -1.4 +/- 1.1 D (range 0 to -4.25 D).

RESULTS

Older patients had a tendency toward smaller vaults on desaccommodation between the ICL and the crystalline lens compared to younger individuals. In younger patients, there was a decrease of the vault on accommodation, whereas it increased in older persons (P = .005). During accommodation, the more the anterior lens surface shifted forward, the more the ICL bulged (P = .005). The change in vaulting was significantly larger at 5.00 D than at 3.00 D accommodation stimulus (P = .012).

CONCLUSIONS

The behavior of ICLs in relation to the crystalline lens during accommodation varied with age and could be shown by PCI. The position shift of the ICL depended on the initial vault at desaccommodation and the ability of the anterior lens surface to bulge forward. Even though the crystalline lens stiffened, and therefore accommodation deteriorated with age, there was still a movement of the ICL, pointing to the role of the ciliary muscle movement in 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.

Localization and ontogeny of aquaporin-1 and -4 expression in iris and ciliary epithelial cells in rats

The precise localization of aquaporin (AQP)1 and AQP4 was studied in iris and ciliary epithelial cells, in both mature and developing rats, to elucidate the molecular mechanisms underlying aqueous humor balance. Anterior segments of eyes dissected from embryonic day (E)13, E15, E18, and E20, postnatal day (P)0, P7, and P14, and postnatal week 8 rats were subjected to immunofluorescence analysis with AQP isoform-specific antibodies. In adult rat eye, AQP1 was localized to the apical and basolateral plasma membranes of iris epithelial cell layers and of anterior ciliary non-pigmented epithelial (NPE) cells. Conversely, AQP4 was localized to the basolateral plasma membrane of NPE cells in ciliary epithelium and the posterior iris. Developmentally, AQP1 was detected as early as E15 in immature iris and ciliary epithelial cells, and expression persisted throughout development up to adulthood. In contrast, AQP4 was first observed at P7 in the developing pars plicata, and the AQP4-positive area gradually spread to cover the entire pars plicata as development proceeded. These findings indicate that both AQP1 and AQP4 contribute to aqueous humor secretion in the rat eye, thereby maintaining proper intraocular pressure. Moreover, AQP appears to play a major role in aqueous humor secretion in early eye development. This study thus provides a basis for understanding the molecular mechanisms of aqueous humor secretion in pathological and physiological conditions.

Accommodation: mechanism and measurement

A clear understanding of the anatomy of accommodative structures, the mechanism of accommodation, and the causes of presbyopia is necessary to understand whether accommodation may be restored to the presbyopic eye. Not withstanding the significant challenges that are faced owing to age-related changes in the eye, theoretically, it may be possible to restore accommodation to a presbyopic eye with an artificial accommodative intraocular lens.

[The in vitro electrical parameters of the isolated porcine ciliary epithelium]

PURPOSE

To study the characteristics of ion transport across the isolated porcine ciliary epithelium to offer the good model for human ciliary epithelium study.

METHODS

Fresh isolated pig ciliary epithelium was mounted in a modified Ussing-type chamber to measure the electrical parameters and the effect of 0.1mM ouabain was investigated.

RESULTS

The potential difference (PD) across the preparations was (-0.6 +/- 0.1) mV and was consistently negative at the aqueous side. The short circuited current (SCC) and resistance (R) were found to be (-10.9 +/- 1.2) microA/cm2 and (54.6 +/- 1.6) omegacm2 respectively. Both PD and SCC were firstly hyperpolarized (stimulation) and then depolarized when 0.1 mM ouabain was applied to the aqueous side.

CONCLUSION

The polarity of transepithelial PD of the isolated porcine ciliary epithelium was negative at the aqueous side, implying an anion transport may be important in the aqueous humor formation (AHF). Na+, K+ -ATPase is located on the PE and NPE cells of the porcine ciliary epithelium and plays an important role in

Initial destination of the disaccommodation step response

Peak velocity and peak acceleration of disaccommodation step responses remain invariant of response magnitude for a constant starting position and they increase linearly with proximity of starting position. This suggests that disaccommodation response is initiated towards an initial (default) destination and is switched mid-flight to attain the desired final destination. The dioptric location of initial destination was estimated from the x-intercept of regression of peak velocity on response starting position. The x-intercept correlated well with subject's cycloplegic refractive state and poorly with their dark focus of accommodation. Altering the dark focus by inducing fatigue in the accommodative system did not alter the x-intercept. These observations suggest that cycloplegic refractive state is a good behavioral correlate of initial destination of disaccommodation step responses.

Nicotinic Signal Transduction Machinery

Nicotinic synapses employ acetylcholine to activate ligand-gated ion channels that are cation-selective in vertebrates. Although the resulting nicotinic cholinergic transmission is famously excitatory at the neuromuscular junction, it plays many additional roles in the CNS. Most prevalent is that of modulation, usually involving calcium and signal transduction. Because of this, it is becoming increasingly important not only to understand the mechanisms that guide nicotinic receptors to appropriate locations but also to identify the postsynaptic machinery making possible the requisite signal transduction. Clearly, the kinds of components tethered in the vicinity of the receptor will assume a major role in determining the consequences of receptor activation. One of the most abundant and interesting nicotinic receptors in this respect is the species comprised of the alpha7 gene product (Broide and Leslie, 1999). These alpha7 homopentameric nicotinic acetylcholine receptors (alpha7 nAChRs) have a high relative permeability to calcium, rivaling that of NMDA receptors. But unlike NMDA receptors, alpha7 nAChRs promote calcium influx without requiring a coincident event such as membrane depolarization. As a result, the receptors are well equipped to regulate calcium-dependent events in neurons, particularly when depolarization might be occluded.

Prostaglandins E1 and E2, but not F2alpha or latanoprost, inhibit monkey ciliary muscle contraction

PURPOSE

To investigate the effects of prostaglandin (PG) E1, E2, F2alpha, and latanoprost acid on the electrically evoked contractile response of isolated rhesus monkey ciliary muscle.

METHODS

Longitudinal ciliary muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100 Hz, 0.3 ms, 10 V) was applied through a pair of platinum plate electrodes.

RESULTS

The ciliary muscle produced atropine-sensitive excitatory contraction in response to field stimulation. PGE1 and PGE2 (1 microM) attenuated the contraction to levels that were 68% and 65.1%, respectively, of the normal amplitude. However, PGF2alpha and latanoprost acid (1 microM) did not significantly change the response amplitude.

CONCLUSIONS

Our results indicate that PGF2alpha and latanoprost acid do not interact with the prostanoid receptor involved at the pre- and/or postsynaptic site. Therefore, it is unlikely that the hypotensive action by these agents is due to relaxation of the ciliary muscle.

Activation of canonical Wnt pathway promotes proliferation of retinal stem cells derived from adult mouse ciliary margin

Adult retinal stem cells represent a possible cell source for the treatment of retinal degeneration. However, only a small number of stem cells reside in the ciliary margin. The present study aimed to promote the proliferation of adult retinal stem cells via the Wnt signaling pathway. Ciliary margin cells from 8-week-old mice were dissociated and cultured to allow sphere colony formation. Wnt3a, a glycogen synthase kinase (GSK) 3 inhibitor, fibroblast growth factor (FGF) 2, and a FGF receptor inhibitor were then applied in the culture media. The primary spheres were dissociated to prepare either monolayer or secondary sphere cultures. Wnt3a increased the size of the primary spheres and the number of Ki-67-positive proliferating cells in monolayer culture. The Wnt3a-treated primary sphere cells were capable of self-renewal and gave rise to fourfold the number of secondary spheres compared with nontreated sphere cells. These cells also retained their multilineage potential to express several retinal markers under differentiating culture conditions. The Wnt3a-treated cells showed nuclear accumulation of beta-catenin, and a GSK3 inhibitor, SB216763, mimicked the mitogenic activity of Wnt3a. The proliferative effect of SB216763 was attenuated by an FGF receptor inhibitor but was enhanced by FGF2, with Ki-67-positive cells reaching over 70% of the total cells. Wnt3a and SB216763 promoted the proliferation of retinal stem cells, and this was partly dependent on FGF2 signaling. A combination of Wnt and FGF signaling may provide a therapeutic strategy for in vitro expansion or in vivo activation of adult retinal stem cells.

Retinal properties and potential of the adult mammalian ciliary epithelium stem cells

The ciliary epithelium (CE) in the adult mammalian eye harbors a mitotic quiescent population of neural stem cells. Here we have compared the cellular and molecular properties of CE stem cells and populations of retinal progenitors that define the early and late stages of histogenesis. The CE stem cells and retinal progenitors proliferate in the presence of mitogens and share the expression of universal neural and retinal progenitor markers. However, the expression of the majority of retinal progenitor markers (e.g., Chx10) is transient in the former when compared to the latter, in vitro. They are similar to early than late retinal progenitors in their proliferative response to FGF2 and/or EGF. Analysis of the differentiation potential of CE stem cells shows that they are capable of generating both early (e.g., retinal ganglion cells) and late (e.g., rod photoreceptors) born retinal neurons. However, under identical differentiation conditions, i.e., in the presence of 1% FBS, they generate more early-born retinal neurons than late-born retinal neurons showing a preference for generating early retinal neurons. Transcription profiling of these cells and retinal progenitors demonstrate that they share approximately 80% of the expressed genes. The CE stem cells have more unique genes in common with early retinal progenitors than late retinal progenitors. Both proliferative/differential potential and transcription profiles suggest that CE stem cells may be a residual population of stem cells of optic neuroepithelium, representing a stage antecedent to retinal progenitors.

Morphological changes in glaucomatous eyes and the role of TGFβ2 for the pathogenesis of the disease

This review summarizes the Ernst H. Bárány Prize Lecture given at the XVI. meeting 2004 of the International Society of Eye Research in Sydney, Australia. The article describes the author's early studies starting with the determination of the site of aqueous humour outflow resistance and its regulation through ciliary muscle contraction, which were performed in collaborations with Bárány. It continues with the qualitative and quantitative evaluation of the trabecular meshwork (TM) changes seen in different kinds of glaucoma diseases. A comparison of correlations between meshwork pathology, IOP, and axon loss in the optic nerve between eyes with pseudoexfoliation glaucoma (PEXG) and primary open angle glaucoma (POAG) indicates that in the secondary glaucoma (PEXG) optic neuropathy is mainly induced by an increase in IOP. In eyes with POAG, the correlations point towards a more complex pathogenesis of the disease. Common factors might be involved in both the TM and the optic nerve changes. In vitro studies performed in cell cultures of human TM cells and optic nerve astrocytes as well as organ culture studies of the anterior eye segment indicate that TGFbeta2 might be one of the factors involved in the development of POAG. The paper is primarily focused on studies performed by the author and complete reference to other previous or contemporary studies is therefore not given as the purpose is not to present a comprehensive review article.

Steepening of corneal curvature with contraction of the ciliary muscle

PURPOSE

To measure the changes of corneal curvature during contraction of the ciliary muscle.

SETTING

Department of Ophthalmology, St. Luke's International Hospital, Tokyo, Japan.

METHODS

Twenty-eight eyes of 14 healthy volunteers under 40 years old were enrolled in this prospective randomized controlled study and divided into pilocarpine and control groups. Intraocular pressure (IOP), pupil diameter, and corneal topography were measured before and 40 minutes after instillation of topical pilocarpine 4% or balanced salt solution. Corneal topography was analyzed for the mean ring-power of Placido rings 1 through 25, average corneal power (ACP), and for spherical equivalent, regular astigmatism, asymmetry, and high-order irregularity by Fourier analysis.

RESULTS

Pilocarpine had no effect on IOP, but it did cause a significant decrease in mean pupil diameter. Simultaneously, pilocarpine increased the mean ring powers for Placido rings 1 through 4 and the ACP (+0.13 diopters (D) +/- 0.17 [SD]; P=.017). By Fourier analysis, the mean spherical component for the central 3.0 mm of the cornea increased in the pilocarpine group (+0.08 +/- 0.15 D; P=.020). There were no changes in components of regular astigmatism, asymmetry, and high-order irregularity.

CONCLUSIONS

The central cornea steepened in curvature and increased in power owing to contraction of the ciliary muscle. The results suggest that changes in corneal curvature increase refractive power during accommodation.

The accommodation of lens implants

Efforts devoted to the production of accommodative lens implants may be premature as there is conflicting information about the functional performance of the aged ciliary muscle which may determine their performance. Additional doubts exist on the performance of the ageing lenticular capsule in connection with some types of implant. Not only do these matters need resolving, but the change in the optical power of the eye needs also to be large enough for reading glasses to become unnecessary. However, not all these strictures apply to the development of accommodative lens implants for children who may be aphakic following operations, e.g. for congenital cataracts.

Roles of cell-adhesion molecules nectin 1 and nectin 3 in ciliary body development

Nectins are Ca2+-independent immunoglobulin-like cell-cell-adhesion molecules consisting of four members. Nectins homophilically and heterophilically trans-interact to form a variety of cell-cell junctions, including cadherin-based adherens junctions in epithelial cells and fibroblasts in culture, synaptic junctions in neurons, and Sertoli cell-spermatid junctions in the testis, in cooperation with, or independently of, cadherins. To further explore the function of nectins, we generated nectin 1–/– and nectin 3–/– mice. Both nectin 1–/– and nectin 3–/– mice showed a virtually identical ocular phenotype, microphthalmia, accompanied by a separation of the apex-apex contact between the pigment and non-pigment cell layers of the ciliary epithelia. Immunofluorescence and immunoelectron microscopy revealed that nectin 1 and nectin 3, but not nectin 2, localized at the apex-apex junctions between the pigment and non-pigment cell layers of the ciliary epithelia. However, nectin 1–/– and nectin 3–/– mice showed no impairment of the apicolateral junctions between the pigment epithelia where nectin 1, nectin 2 and nectin 3 localized, or of the apicolateral junctions between the non-pigment epithelia where nectin 2 and nectin 3, but not nectin 1, localized. These results indicate that the heterophilic trans-interaction between nectin 1 and nectin 3 plays a sentinel role in establishing the apex-apex adhesion between the pigment and non-pigment cell layers of the ciliary epithelia that is essential for the morphogenesis of the ciliary body.

Influence of pupillary diameter, ciliary muscle tone, and ambient light on nerve fiber layer measurements with scanning laser polarimetry

PURPOSE

To evaluate the influence of the pupillary diameter, ciliary muscle tone, and room light on nerve fiber layer measurements with the scanning laser polarimeter (GDx).

METHODS

One randomly selected eye of ten normal volunteers was examined with the GDx in a two-day protocol under eight testing conditions (pilocarpine 1%, phenylephrine 10%, tropicamide 1%, or no drops with room lights on or off). The twelve parameters, obtained by the GDx, were compared under the eight testing conditions, using two way ANOVA for repeated measurements and Tukey HSD post hoc test.

RESULTS

Ten of the twelve parameters were statistically significantly different (P < 0.05) when measured under the three medication or no medication conditions, controlling for the ambient light status. There were no significant differences when measured with the light on or off, controlling for use of drops.

CONCLUSIONS

Nerve fiber layer measurements with the GDx were influenced by drugs affecting pupillary diameter, but not by the status of room light or ciliary muscle tone.

The origin of extrinsic nitrergic axons supplying the human eye

Nitrergic nerve fibres of intrinsic and extrinsic origin constitute an important component of the autonomic innervation in the human eye. The intrinsic source of nitrergic nerves are the ganglion cells in choroid and ciliary muscle. In order to obtain more information on the origin of extrinsic nitrergic nerves in the human eye, we obtained superior cervical, ciliary, pterygopalatine and trigeminal ganglia from six human donors, and stained them for neuronal nitric oxide synthase (nNOS) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D). In the superior cervical ganglia, nNOS/NADPH-D-positive varicose axons were observed whereas perikarya were consistently negative. Fewer than 1% of perikarya in the ciliary ganglia were labelled for nNOS/NADPH-D. The diameter of nNOS/NADPH-D-positive ciliary perikarya was between 8 and 10 microm, which was markedly smaller than the diameter of the vast majority of negative perikarya in the ciliary ganglion. More than 70% of perikarya in the pterygopalatine ganglia were intensely labelled for both nNOS and NADPH-D. In trigeminal ganglia, 18% of perikarya were nNOS/NADPH-D-positive. The average diameter of trigeminal nNOS/NADPH-D perikarya was between 25 and 45 microm. Pterygopalatine and trigeminal ganglia are the most likely sources for extrinsic nerve fibres to the human eye.