Zonula Research Articles

Evaluation of the mechanical behaviour and estimation of the elastic properties of porcine zonular fibres

The mechanical behaviour of zonular fibres greatly affects the accommodation process in mammalian eyes. This paper introduces a detailed measurement procedure for the purpose of obtaining the force–displacement diagram necessary to evaluate the mechanical properties of porcine zonular fibres in situ. It is a complex technique, keeping the integrity of the zonular bundles between the crystalline lens and the ciliary muscle cells. We present a brief description of the measurement procedure both in theory and in practice, along with the force–displacement diagrams acquired from a porcine sample group. The strengths of this newly developed method are the unequivocal force transmission between the sample and the transducer, and the intact connection between the ciliary body and the crystalline lens via zonular fibres. With the aid of these measurements, we define an estimated material model for the zonular apparatus both analytically and using the finite element method. The two different evaluation methods show close agreement in the calculated Young׳s modulus for the zonular fibres. The range of the calculated elastic modulus is 200–250kPa. This new measuring method is adaptable to human specimens. Despite its complexity, the entire procedure and the evaluation part are reproducible. The constitutive model aims to shed light on the mechanics of the accommodation process.

Impact of lens thickness on hyper mature cataract surgical complications: preliminary results of a prospective study

AbstractPurpose There are no objective parameter allowing to predict the risk of surgical difficulties in white hyper mature cataracts. Lens density can be assessed by pentacam, but this tool is not commonly available. Our purpose was to assess the correlation between lens thickness (LT) and surgery complications.Methods We conducted a prospective, observational, and monocentric study. We included all patients operated on for white hyper mature cataract from january 2013 to march 2014. We selected patients with a visual acuity (VA) lower than 20/200 on the Monoyer scale. We excluded patients suspect of zonula fibers weakness. Morphological features assessed were LT, axial length, depth of anterior chamber and vitreous length, measured by A or B ulrasound scan. The other parameters assessed were the surgical duration, complications during surgery, VA and corneal edema at the seventh day after surgery (analogic scale from 0 to 3).Results We included 30 eyes of 29 patients. Mean LT was 4.11 ± 0.64 mm, with a median of 3,89 mm. The Pearson correlation coefficient (PCC) between LT and operative duration was 0.27. The PCC between lens thickness and length of anterior chamber was ‐0.32. The PCC between LT and BCVA at the 7th day after surgery was ‐0.53. Two groups were defined: group 1 with LT < 3.89mm, and group 2 with LT > 3.89mm. Mean length of the anterior chamber were respectively 3.48 and 3.02 mm (p=0.01). Three per operative complications were noted.Conclusion LT in white hyper mature cataract did not seem to be correlated with duration of the surgery. However, it seemed to be inversely correlated with the depth of anterior chamber and with visual acuity at the 7th day.

Effects of Clostridium butyricum combined with glutamine on the expression of intestinal tight junction protein in stress mouse model

Objective To investigate the mechanism of the permeability of intestinal mucosa in the pathogenesis of irritable bowel syndrome (IBS) and the interventional effects of Clostridium butyricum combined with glutamine.Methods According to random number method,fifty BALB/c mice were divided into control group,experimental control group,glutamine group,Clostridium butyricum group and combination group.IBS mice model was established by water-avoidance stress (WAS) experiment.The defecating time of mice and fecal water content were detected by dyed stool after mice gavaged with methylcellulose (1.5％).The pathological injury of intestine was assessed by hematoxylin and eosin staining.The visceral sensitivity was evaluated by colorectal distention test (CRD).The changes of the permeability of intestine was evaluated by detecting the changes of serum D-lactic acid (D-LA),level of diamine oxidase (DAO),expressions of intestinal epithelial cells (IEC) cell tight junction protein (TJ) (occludin-1,claudin-1,zonula occludens-1 (ZOL-1)) at protein level.The interventional effects of Clostridium butyricum combined with glutamine were evaluated.t test was performed for comparison between groups,and analysis of variance was used for comparison among multi-groups.Results Compared with the control group,the defecating time of experimental control group was significantly shorten ((100.40±14.80) min vs (75.88±12.20) min and water content of fecal significantly increased ((54.76±9.98)％ vs (74.95±7.15)％,t =3.692 and 4.023; P=0.002 and 0.002).The lowest threshold of visceral sensitivity significantly decreased ((40.87 ± 4.82) mmHg (1 mmHg=0.133 kPa) vs (27.80±3.18) mmHg; t=8.761,P＜0.01),while the mucosal pathological injury score significantly increased (0.50±0.15 vs2.60±0.97; t＝6.034,P＜0.01).The level of D-LA ((1 476±246.8) ng/L vs (913.6±90.1) ng/L)) and DAO ((3 391.0±256.9) vs (5 096.0±725.2) ng/L) significantly increased (t=40.920 and 29.810; both P＜0.05),and the expression of tight junction protein ZOL-1 (0.165±0.005 vs0.119±0.003),occludin-1 (0.104±0.016 vs 0.022±0.006) significantly decreased (t=19.830 and 19.830; both P＜0.01).Compared with the experimental control group,after intragastric intervention the defecating time of glutamine group,Clostridium butyricum group and combination group increased ((90.50±3.78),(97.56±8.79) and (99.89±11.90) min and water content of fecal decreased ((69.33±6.71)％,(58.07±8.97)％ and (56.74±8.12)％) and the differences were statistically significant (F=10.020 and 8.740; both P＜0.01).The results of Clostridium butyricum group and combination group were good (F=2.481 and 4.874; both P＜0.05).And the lowest threshold of visceral sensitivity significantly increased ((31.80±2.69),(36.04±5.06) and (38.93±3.30) mmHg; F=2.420,P＜0.05),the result of combination group was the best (F=3.550,P＜0.01).Jejunal mucosal injury was significantly reduced (2.00 ± 0.94,1.30 ± 0.68 and 1.30±0.48; F＝11.350,P＜0.01).After intragastric intervention,serum levels of D-LA ((1 370.0± 78.9),(1 066.0±155.5) and (1 039.0±129.0) ng/L) and DAO ((4 808.0±477.4),(3 713.0± 595.0) and (3 725.0±615.9) ng/L) of glutamine group,Clostridium butyricum group and combination group significantly decreased (F＝37.480 and 27.670; both P＜0.01).The level of ZOL-1(0.126± 0.014,0.125±0.006,0.138±0.004) and occludin 1 (0.037±0.013,0.073±0.028,0.078±0.027) of glutamine group,Clostridium butyricum group and combination group significantly increased,and the differences were statistically significant (F=5.867 and 10.630; both P＜0.05).The change of ZOL-1 of combination group was more than that of Clostridium butyricum group (t =5.457,P ＜ 0.05).Conclusions WAS experiment can induce visceral hypersensitivity,increase the permeability of intestine and reduce the function of intestinal epithelial barrier.Clostridium butyricum and glutamine are effective in the recovery of visceral hypersensitivity and the permeability of mucosal epithelia cells. Key words: Stress; Tight junctions protein; Intestinal permeability; Clostridium butyricum; Glutamine

Morphological alterations within the peripheral fixation of the iris dilator muscle in eyes with pigmentary glaucoma.

To analyze the peripheral fixation of the iris dilator muscle in normal eyes and in eyes with pigmentary glaucoma (PG). Using 63 control eyes (age 18 months-99 years), the peripheral iris dilator was investigated by light microscopy, immunohistochemistry, and electron microscopy. Development was studied using 18 differently aged fetal eyes stained immunohistochemically against α-smooth muscle (SM) actin. The peripheral iris dilator muscle in PG was analyzed using semithin and ultrathin sections of six glutaraldehyde-fixed eyes from three donors aged 38, 62, and 74 years. In normal eyes, the peripheral end of the iris dilator muscle is arranged in a sphincter-like manner. Arcade-shaped tendinous connections associated with myofibroblasts (iridial strands) anchor the iris dilator within the elastic-fibromuscular ciliary meshwork that also serves as fixation area for the elastic tendons of the inner ciliary muscle portions. The iridial strands are innervated and can adapt their length during accommodation. The PG eyes show incomplete circular bundles and iridial strands that are mainly anchored to the iris stroma and the flexible uveal parts of the trabecular meshwork. The normal anchorage of the peripheral iris dilator and its presumably neuronally regulated length adaptation stabilize the peripheral iris during accommodation. Insufficient fixation in PG could promote posterior bowing of the iris with rubbing against the zonular fibers and pigment liberation from the iris pigmented epithelium.

Latent TGF-β binding protein-2 is essential for the development of ciliary zonule microfibrils.

Latent TGF-β-binding protein-2 (LTBP-2) is an extracellular matrix protein associated with microfibrils. Homozygous mutations in LTBP2 have been found in humans with genetic eye diseases such as congenital glaucoma and microspherophakia, indicating a critical role of the protein in eye development, although the function of LTBP-2 in vivo has not been well understood. In this study, we explore the in vivo function of LTBP-2 by generating Ltbp2(-/-) mice. Ltbp2(-/-) mice survived to adulthood but developed lens luxation caused by compromised ciliary zonule formation without a typical phenotype related to glaucoma, suggesting that LTBP-2 deficiency primarily causes lens dislocation but not glaucoma. The suppression of LTBP2 expression in cultured human ciliary epithelial cells by siRNA disrupted the formation of the microfibril meshwork by the cells. Supplementation of recombinant LTBP-2 in culture medium not only rescued the microfibril meshwork formation in LTBP2-suppressed ciliary epithelial cells but also restored unfragmented and bundled ciliary zonules in Ltbp2(-/-) mouse eyes under organ culture. Although several reported human mutant LTBP-2 proteins retain normal domain structure and keep the fibrillin-1-binding site intact, none of these mutant proteins were secreted from their producing cells, suggesting secretion arrest occurred to the LTBP-2 mutants owing to conformational alteration. The findings of this study suggest that LTBP-2 is an essential component for the formation of microfibril bundles in ciliary zonules.

Zonula Occludens protein-1 as a potential prognostic factor in B cell lymphoma

Zonula Occludens protein-1 as a potential prognostic factor in B cell lymphoma

Developments in the correction of presbyopia II: surgical approaches

To discuss the various static and dynamic surgical approaches which attempt to give presbyopes good vision at far, intermediate and near viewing distances. Static methods broadly adopt the same optical techniques as those used in presbyopic contact lens correction and aim to satisfy the needs of the presbyope by increasing binocular depth-of-focus, often using monovision as well as simultaneous-imagery. Dynamic methods generally attempt to make use of at least some of the still-active elements of the accommodation system. They include procedures which are supposed to modify the relative geometry of the ciliary muscle and lens, or which reduce the stiffness of the presbyopic lens either by replacing it with other natural or man-made material or by subjecting it to femtosecond laser treatment. Alternatively the natural lens may be replaced by some form of intraocular lens which changes power as a result of forces derived from the still-active ciliary muscle, zonule and capsule, or other sources. At present, multifocal intraocular lenses appear to offer the most consistent and reliable surgical approach to surgical presbyopic correction. They have obvious advantages in convenience and stability over optically-similar, simultaneous-image presbyopic contact lenses but this must be balanced against their relative inflexibility in cases of patient dissatisfaction. Dynamic methods remain largely experimental. Although some approaches show promise, as yet no method has demonstrated a reliable, long-term ability to correct distance refractive error and to appropriately change ocular power in response to changes in viewing distance over the normal range of interest.

A reasonable option in vitrectomized eyes: manual small incision cataract surgery.

Dear Sir,It is known that cataract surgery is challenging in vitrectomized eyes.Cataract surgeons may have encountered with posterior capsular complications and nucleus drop events even with minimal ocular manipulations and low irrigation bottle height.Inadvertent damage to the zonular fibers,posterior or peripheral lens capsule with ocutome or microvitreoretinal(MVR)blade in previous

Hurricane cortical aspiration technique: One-step continuous circular aspiration maneuver

We describe a modification of the original standard radial aspiration technique. The modified technique--hurricane 1-step continuous circular cortical aspiration--has the potential to improve this part of phacoemulsification surgery with benefits in surgical time and possible decreases in fluid, corneal edema, and traction on the zonular fibers through better distribution of tractional forces. The first results were encouraging and without complications. No author has a financial or proprietary interest in any material or method mentioned.

Surgical management of dislocated intraocular lens in vitreous cavity

Objective To analyze the causes,operative methods and the clinical results of patients with dislocated intraocular lens (IOL) in vitreous cavity.Methods eight eyes of 8 cases of dislocated IOL in vitreous cavity were analyzed retrospectively.The causes,surgical treatment and complications of IOL falling into the vitreous cavity were concluded.Results The causes of intraocular lens dislocation included lens zonules broken (1 case),incomplete capsular membrane (6 cases) and trauma (1 case).Two patients were treated with removing dislocated IOLs and transscleral suture fixation of new IOLs.For the other 6 eyes,the original dislocated IOLs were sutured to the ciliary sulcus without expanding the incision.Conclusion Some dislocated IOLs can be treated by removing and transscleral suture fixation of a new IOL.For most dislocated IOLs,the original IOLs can be sutured to the ciliary sulcus,which has good clinical effect with few surgical complications. Key words: Lens, intraocular; Dislocation; Vitreous; Management, surgical; Vision

Microfibril-associated glycoprotein-1 controls human ciliary zonule development in vitro.

The ciliary zonule in the eye, also known as Zinn’s zonule, is composed of oxytalan fibers, which are bundles of microfibrils consisting mainly of fibrillin-1. However, it is still unclear which of the microfibril-associated molecules present in the ciliary zonule controls oxytalan fibers. Microfibril-associated glycoprotein-1 (MAGP-1) is the only microfibril-associated molecule identified in the human ciliary zonule. In the present study, we used siRNA against MAGP-1 in cultures of human non-pigmented ciliary epithelial cells to examine the extracellular deposition and appearance of fibrillin-1 employing Western blotting and immunofluorescence. MAGP-1 suppression led to a reduction of fibrillin-1 deposition. Immunofluorescence also confirmed that RNAi-mediated down-regulation of MAGP-1 led to suppression of fiber development. These results suggest that MAGP-1 plays a crucial role in the extracellular deposition of fibrillin-1 during formation of the human ciliary zonule.

The changes of anatomic and topographic characteristics of eye anterior segment after uncomplicated cataract phacoemulsification

Aim. To study the changes of anatomic and topographic characteristics of the eye anterior segment after uncomplicated cataract phacoemulsification using corneal incision with intraocular soft lens implantation. Methods. The data of ultrasound biomicroscopy and noncontact tonometry of 58 eyes (56 patients, 32 females, 24 males aged 54 to 78 years) before and after cataract phacoemulsification were analyzed. Paitents with survived ocular trauma, refractive keratoplasty, glaucoma, uveitis, and surgical complications (incomplete capsulorrhexis, posterior capsule rupture, ciliary zonule disinsertion, corneal burn). Apart from the common examinations (visual acuity testing, tonometry, tonography, eye A- and B-ultrasonography, biomicroscopy), all patients underwent eye ultrasound biomicroscopy. Results. Anterior chamber depth increased from 2.73±0.10 to 4.17±0.06 mm (p ≤0.001). Trabecula-iris distance measured at 500 μm from the scleral spur, increased from 0.38±0.02 to 0.47±0.02 mm (p ≤0.001). Anterior chamber angle increased from 28.69±1.87 to 42.73±1.56 degrees (p ≤0.001), the angle between the iris and the sclera increased from 32.78±1.39 to 41.36±0.84 degrees (p ≤0.001), the angle between the sclera and ciliary processes increased from 39.48±1.29 to 45.30±1.16 degrees (p ≤0.001). Intraocular pressure according to the non-contact tonometry data decreased from 18.16±1.29 to 13.55±0.95 mm Hg (p ≤0.001). Conclusion. Anterior chamber depth, trabecula-iris distance, anterior chamber angle, the angle between sclera and iris and the angle between sclera and ciliary processes increased significantly after phacoemulsification with intraocular lens implantation. Intraocular pressure decreased significantly according to the non-contact tonometry data.

Clinical characteristics and surgical outcomes of phacoemulsification in true exfoliation syndrome

To review the clinical characteristics and surgical outcomes of patients with true exfoliation syndrome of the lens capsule having phacoemulsification cataract surgery. Hong Kong Eye Hospital, Kowloon, Hong Kong. Case series. Eyes of patients with true exfoliation syndrome diagnosed clinically or intraoperatively had standard phacoemulsification and intraocular lens (IOL) implantation. The anterior capsules removed during capsulorhexis were sent for histological confirmation. Twenty-four eyes of 18 patients were included. All eyes were confirmed to have true exfoliation syndrome by histological examination of the anterior lens capsule. Seven eyes (29.2%) had preexisting chronic glaucoma; 5 (20.8%) had laser iridotomy before the diagnosis. During phacoemulsification, all eyes had a continuous curvilinear capsulorhexis without complications. Trypan blue staining was used during capsulorhexis in 11 eyes (45.8%). Posterior capsule rupture occurred during lens chopping in 1 eye (4.2%). No loose zonular fibers or radial extension of capsulorhexis occurred. Capsular bag IOL implantation was successfully performed in all cases except the 1 with a posterior capsule rupture, in which an anterior chamber IOL was implanted. Phacoemulsification was safely performed in eyes with true exfoliation syndrome. Trypan blue staining can be used to facilitate capsulorhexis creation. Ultrasound biomicroscopy or anterior segment optical coherence tomography may be useful in preoperative assessment of such cases. The disease may be associated with glaucoma and laser iridotomy.

Ocular Phenotype ofFbn2-Null Mice

Fibrillin-2 (Fbn2) is the dominant fibrillin isoform expressed during development of the mouse eye. To test its role in morphogenesis, we examined the ocular phenotype of Fbn2(-/-) mice.Ocular morphology was assessed by confocal microscopy using antibodies against microfibril components.Fbn2(-/-) mice had a high incidence of anterior segment dysgenesis. The iris was the most commonly affected tissue. Complete iridal coloboma was present in 37% of eyes. Dyscoria, corectopia and pseudopolycoria were also common (43% combined incidence). In wild-type (WT) mice, fibrillin-2-rich microfibrils are prominent in the pupillary membrane (PM) during development. In Fbn2-null mice, the absence of Fbn2 was partially compensated for by increased expression of fibrillin-1, although the resulting PM microfibrils were disorganized, compared with WTs. In colobomatous adult Fbn2(-/-) eyes, the PM failed to regress normally, especially beneath the notched region of the iris. Segments of the ciliary body were hypoplastic, and zonular fibers, although relatively plentiful, were unevenly distributed around the lens equator. In regions where the zonular fibers were particularly disturbed, the synchronous differentiation of the underlying lens fiber cells was affected.Fbn2 has an indispensable role in ocular morphogenesis in mice. The high incidence of iris coloboma in Fbn2-null animals implies a previously unsuspected role in optic fissure closure. The observation that fiber cell differentiation was disturbed in Fbn2(-/-) mice raises the possibility that the attachment of zonular fibers to the lens surface may help specify the equatorial margin of the lens epithelium.

Biocompatibility of chitosan carrier with rabbit corneal endothelium

Background There are a lot of studies about the carrier of corneal endothelial transplantation,but the best carrier has not been defined.Objective This study was to investigate the biocompatibility of chitosan carrier with rabbit corneal endothelium in vivo.Methods Fresh eye-balls were obtained from 10 New Zealand white rabbits.Rabbit corneal endothelial cells (CECs) were isolated and cultured on chitosan carrier in vitro.The morphology and density of rabbits CECs were observed every day,and the expressions of fibronectin (FN),collagen-1 (Coil-I) and Zonula occludens 1 (ZO-1) were detected by immunoinfluorescence.The morphology and ultrastructure of CECs were observed under the scanning and transmission electron microscope.Chitosan carrier with CECs was implanted into the anterior chamber of the left eyes in ten healthy New Zealand white rabbits,and only paracentesis of anterior chamber was performed in the right eyes as controls.The inflammation of ocular anterior segment was examined under the slit lamp microscope,and corneal thickness was measured 1 week,4 and 8 weeks after operation.Corneal endothelium cell density and morphology were examined under the corneal endothelial microscope at postoperative 2 weeks.Corneal samples were collected for the regular histopathological examination to observe the inflammatory reaction at postoperative 1 month and 3 months.Paired t test was used for statistical analyses between the control group (left eyes) and the experimental group (right eyes).The use and care of the animals followed the Statement of ARVO.Results CECs formed an intact monolayer of cells with the uniform shape and size on the chitosan membrane after incubated for 5 days.The cells reached confluence of 90％ 7 days after cultured with the 40％ hexagon cells.Under the scanning electron nicroscope,rabbit CECs showed the round or polygon in the shape with the microvillus on the cell surface.The cells connected closely by desmosome.The processes,pseudopodiums and microvillus on the cellular surface,vacuole in the cytoplasm,expanded endoplasmic reticulum with ribosome and abundant chromatin were exhibited under the transmission electron microscope.The immunofluorescence examination revealed the positive expressions of FN,Coll-Ⅰ and ZO-1 in the CECs on the chitosan carrier.In the in vivo experiment,the exudation in the anterior chamber and corneal edema were seen under the slit lamp microscope 3 days after implantation of chitosan carrier with CECs.However,the inflammation was gone 14 days after operation.The differences of the corneal thickness were no significant between the experimental group and the control group 1 week and 4,8 weeks after operation (t =1.377,P=0.265;t =1.795,P=0.165 ; t =0.390,P =0.760).In addition,no significant differences were found in the CECs density and the hexagon cells rate between the two groups(P =0.365,0.062).The histopathological examination showed that the inflammatory cells around the chitosan membrane were disappeared 3 months after operation and showed a good corneal structure.Conclusions Chitosan carrier has a good biocompatibility with rabbit CECs and anterior chamber,and it may be a potentially good carrier for CECs transplantation. Key words: Chitosan; Cornea; Endothelial cell; Biocompatibility; Biotoxity; Rabbit

Interpreting human eye accommodation from the perspective of morphological studies: A discussion with the author of ‘A novel concept of accommodation: Human eyes optical system based on hyperfocal distance-micro zoom '

Accommodation of the human eye ian extremely complex and dynamiprocess,which iaccomplished by the interaction between the central nervousystem and variouoculastructurethaare relevanto accommodation.Varioumechanismof accommodation have been puforward since the beginning of the 19th century,among which Helmhohz＇theory ithe mosfamous.However,iistill challenged by othetheories.So far,the mechanism of accommodation hanobeen fully understood.The mosdirecmethod to study accommodation ito observe changein the biometry of the oculastructureduring accommodation,which ialso the mosobjective interpretation of accommodative mechanisms.The rapid developmenof imaging technologiein regardto ophthalmology makethipossible.Thiarticle aimto describe the use of variouimaging technologiein oculaaccommodative studiein vivo from the perspective of morphology. Key words: Accommodation ; Morphology; Imaging technology; Ciliary muscle; Crystalline lens ; Zonularfibers ; Contend

Characterization of phenotype and molecular characteristics on Vibrio cholerae strains isolated in Shanghai, 1962-2011

To describe the phenotype and molecular characteristics of Vibrio (V.) cholerae strains isolated in Shanghai, from 1962 to 2011. K-B test was used to investigate the antibiotic resistance of V. cholerae strains. PCR was applied to detect seven virulence-related genes including cholera toxin (ctxA), zonula occludens toxin (zot), accessory cholera enterotoxin (ace), hemolysin (hlyA), toxin-coregulated pilus (tcpA) outer membrane protein (ompU) and the regulatory protein genes (toxR). Genetic relation was assessed by pulsed-field gel electrophoresis (PFGE) and the patterns were clustered by BioNumerics software. V. cholerae strains isolated from 1962 to 1996 were sensitive to most of the antibiotics. However, the strains isolated from 2005 to 2011 were resistant to many antibiotics. V. cholerae O139 group showed higher prevalence of resistance to several antibiotics compared with O1 group, and the resistance rate of the O139 toxigenic isolates was higher than that of the non-toxigenic isolates. Most of the O1 strains isolated from 2005 to 2011 were non-toxigenic while O139 strains isolated from 2005 to 2011 were almost toxigenic. There were no strains of ctxA+ detected from the rivers from 2005 to 2011. Main gene type of the O1 strains detected from the aquatic products was hlyA+ toxR+ ompU+, while that of the O139 strains was hlyA+ toxR+ ompU+ ctxA+ ace+ zot+ tcpA+. Using PFGE, 222 V. cholerae strains were subtyped into 121 molecular types. O139 strains were divided to three clusters and O1 strains to five clusters. The characteristics of V. cholerae strains isolated in Shanghai from 1962 to 2011 showed great changes, suggesting that more attention should be paid to the multiplication on antibiotic resistance of V. cholerae strains.

An accommodative intraocular lens

Accommodation in the youthful, phakic human eye is accomplished by contraction of the ciliary body and subsequent release of the resting tension in the zonular fibers by which the crystalline lens ...

Tri-soft shell technique

Soft-shell techniques exist for lower viscosity dispersive with higher viscosity cohesive ophthalmic viscosurgical devices (OVDs) (soft-shell technique [SST]), viscoadaptive OVDs with balanced salt solution (ultimate soft-shell technique), intraoperative floppy-iris syndrome (soft-shell bridge), and many specific modifications for disinserted zonular fibers, frayed iris strands, Fuchs endothelial dystrophy, small holes in the posterior capsule with protruding vitreous, capsular dye use, and others. Soft-shell techniques exist because it is rheologically impossible to control the surgical environment with a single OVD as well as with an ordered combination of rheologically different OVDs. Surgeons frequently confuse these techniques because of their multitude. This paper unifies all SSTs into a single improved tri-soft shell technique (TSST), from which basic specific applications to unusual circumstances are simple and intuitive. As shown with previous SSTs, the TSST allows surgeons to perform complex tasks with greater surgical facility and to protect endothelial cells better than with single OVDs.

A novel concept of accommodation:Human eyes optical system based on hyperfocal distance-micro zoom

Based on a concept of the hyperfocal distance from photographic lens,this study proposes that emmetropia presents far-hyperfocal distance,near-hyperfocal distance and accommodative hyperfocal distance.When emmetropic presbyopias completely lose the ability of accommodation,its farthest blur point is not beyond 1.5 m,even not being at infinity,and the phenomenon of dark focus both completely match with the definition of hyperfocal distance.On the other hand,after cycloplegic mydriatics in emmetropia,it could be found in the region of depth-of-field that there is no change in the back depth of field (clearness in far vision),but change was found in the front depth of field (blur in near vision).It conforms well to the definition of the hyperfocal distance,demonstrating that human eyes belong to the hyperfocal distance optical system.Furthermore,it is reported that the emmetropic presbyopias rarely matched the spectacles higher than +2.50 D in their whole life;therefore,it can be inferred that their accommodative amplitude in youth is equal to this corrected value.This value accounts for about 4％ of the total refractive power in human eyes,so it is suggested that human eye is a micro zoom optical system.Based on the objective existence of hyperfocal distance,the author proposes that human eye is an integrated accommodative mechanism.It includes three components:the accommodative mechanism of near vision,the measuring and controlling mechanism of near vision,and the general control of near vision.This paper discusses the accommodative mechanism of near vision and the resting mechanism of distance vision based on the hyperfocal distance,and considers that when human eye transfer into the accommodation of near vision from the normal distance vision of hyperfocal distance.There are three different pushing forces contributing to lens deformation and its anterior shift,and these forces cause four different accommodative efforts,which constitute the real accommodative efforts in the relative tissue.This paper also points out that it is only the mode of pushing accommodation that can make the lens vary refraction quickly and greatly,and control the amount of deformation effectively.That can not be achieved by the stretching mode proposed by Tscherning & Schachar,because some authors have verified that excessive pulling would result in decline in the refraction,which would be difficult to regulate and control the eye.Similarly,the self-bulging mode of Helmholtz & Gullstrand will not work neither,because it is unable to control the amount of lens deformation that is its fatal defect. Key words: Accommodation; Hyperfocal; Emmetropia; Lens; Ciliary muscle; Zonule; Iris; Pupil; Depth of focus; Dark focus