Peripheral Lens Research Articles

Model of zonular forces on the lens capsule during accommodation

How the human eye focuses for near; i.e. accommodates, is still being evaluated after more than 165 years. The mechanism of accommodation is essential for understanding the etiology and potential treatments for myopia, glaucoma and presbyopia. Presbyopia affects 100% of the population in the fifth decade of life. The lens is encased in a semi-elastic capsule with attached ligaments called zonules that mediate ciliary muscle forces to alter lens shape. The zonules are attached at the lens capsule equator. The fundamental issue is whether during accommodation all the zonules relax causing the central and peripheral lens surfaces to steepen, or the equatorial zonules are under increased tension while the anterior and posterior zonules relax causing the lens surface to peripherally flatten and centrally steepen while maintaining lens stability. Here we show with a balloon capsule zonular force model that increased equatorial zonular tension with relaxation of the anterior and posterior zonules replicates the topographical changes observed during in vivo rhesus and human accommodation of the lens capsule without lens stroma. The zonular forces required to simulate lens capsule configuration during in vivo accommodation are inconsistent with the general belief that all the zonules relax during accommodation.

Contemporary Approach to Narrow Angles.

Glaucoma is the leading cause of irreversible blindness worldwide. Among all glaucoma types, primary angle closure glaucoma (PACG) affects approximately 23 million people worldwide, and is responsible for 50% of glaucoma-related blindness, highlighting the devastating consequences of this disease. The main mechanism of PACG is relative pupillary block. High-risk populations are female gender, Asian ethnicity, high hyperopia, short axial length, and a thick/anteriorly positioned lens. This review discusses the clinical diagnosis, classification, and management of patients with a narrow angle with and without intraocular pressure (IOP) elevation and glaucomatous optic nerve damage, including laser peripheral iridotomy (LPI), endocycloplasty (ECPL), lens extraction, and goniosynechialysis.

Gradient myopic defocus causes scleral tissue reinforcement and structural scleral remodelling

Aims/Purpose: To determine histological effects of lens induced refractive change on scleral remodelling in chicks.Methods: 18 Ross‐Ross chicks were raised for 14 days on a 14 hr light/10 hr dark cycle. 6 chicks were allowed to develop normally. 6 chicks wore conventional ‐10D lenses for the full 14 days. 6 chicks wore conventional ‐10D lenses for the first 7 days and myopia progression control (MPC) lenses or the next 7 days. MPC lenses had a central power of ‐10D and a gradient power rise at pupil edge (+ 2.75D). Birds were euthanized after 14 days and eyes were routinely processed for histopathological evaluation. Whole mount H&E‐stained tissue sections were microscopically analysed using bright field microscopy.Results: All lens treated birds developed significant myopia as expected Total scleral thickness was significantly reduced in the group wearing conventional ‐10 lenses (p < 0.05), but remained comparable to the normal control group for the MPC lenses treated birds. New appositional growth of the cartilaginous sclera was observed in all MPC lenses treated eyes and only in those eyes. The thickness of the cartilaginous component of the sclera was 135 ± 6, 153 ± 5, 125 ± 8 μm for conventional myopic, MPC lenses treated, and control birds respectively. There was a significant increase in the cartilaginous scleral thickness in the MPC lenses treated birds compared to the other two groups (p < 0.03), but not between the conventional ‐10D lens treated and control birds (p > 0.05).Conclusions: It is possible to induce appositional growth in hyaline cartilage in the chick sclera. In our study, this has only been achieved by using MPC lenses to reverse previously induced experimental myopia with conventional minus lenses. Our finding suggests that gradient decrease in peripheral lens power and the resulting differential level of defocus it causes could be a potential trigger of scleral reinforcement through stimulation of cartilage growth in the chick sclera.

Effective Decrease in Myopia Progression With Two Mechanisms of Management.

To ascertain the effectiveness of 0.01% atropine treatment to inhibit myopia progression and the possible additive potency with peripheral defocus contact lenses over 3 years and the rebound effect 1 year after cessation of treatment. This prospective study included 127 children aged 8 to 5 years, divided into three treatment groups: 0.01% atropine and single-vision spectacles (At+SV, n = 36), 0.01% atropine and peripheral defocus contact lens (At+PDCL, n = 30), and 0.01% atropine and dual-focus contact lens (At+DF, n = 25). A control group was prescribed single-vision spectacles (n = 36). Cycloplegic spherical equivalence refraction was measured every 6 months during 3 years of treatment and 1 year after cessation. Myopia progression decreased over 3 years of treatment, more during the second and third years than the first year, to a statistically significant degree in the atropine groups (P < .01): in the first, second, and third years, respectively, -0.42 ± 0.34, -0.19 ± 0.18, -0.22 ± 0.19 diopters (D) in the At+SV group, -0.26 ± 0.21, -0.14 ± 0.37, and -0.15 ± 0.31 D in the At+PDCL group, and -0.22 ± 0.15, -0.15 ± 0.22, and -0.11 ± 0.14 D in the At+DF group. Myopia progressed 1 year after cessation of treatment: -0.29 ± 0.28 D in the At+SV group, -0.13 ± 0.28 D in the At+PDCL group, and -0.09 ± 0.18 D in the At+DF group. After 3 years, there was no statistically significant difference in myopia progression between the At+SV and At+PDCL or At+DF groups (P < .05). Low-dose atropine has been substantiated in this cohort as an effective treatment to decelerate myopia progression over 3 years, more effective in the second and third years of treatment. The combination treatment did not exhibit a statistically significant advantage over monotherapy in this cohort. The At+DF group exhibited a statistically lower rebound effect than the At+SV group. [J Pediatr Ophthalmol Strabismus. 2024;61(3):204-210.].

Изменение толщины хориоидеи в лечении первичного закрытия угла передней камеры глаза

Purpose. To compare choroidal thickness before and after laser peripheral iridotomy (LPI) and lens extraction (LE) in patients with primary angle closure (PAC). Material and methods. The prospective study included 60 patients (60 eyes) with PAC aged 41 to 80 years. LPI was performed in 30 eyes, LE was performed in 30 eyes. All patients underwent Swept Source optical coherence tomography. The parameters of the anterior and posterior segments of the eye were analyzed including the choroidal thickness in the macula (in foveola, in diameters of 1 mm, 2 mm and 3 mm from it) as well as intraocular pressure (IOP) and number of medicines. Results. After LE, choroidal thickness significantly increased (from 341±59 to 345±57 µm, p=0.000) in the foveola as well as in all sectors (p&lt;0.05) except for the nasal one, 3 mm from the center of the foveola (p=0.05). After LPI, choroidal thickness significantly increased in all sectors (all p&lt;0.05) except for the superior (p=0.124) and temporal (p=0.103) sectors 3 mm from the center of the foveola as well as in the foveola itself (from 343±58 to 341±60 µm, p=0.519). There was no significant difference in choroidal thickness in the macula between the groups after treatment (all p&gt;0.05). Conclusion. An increase the choroidal thickness in patients with PAC after LPI and LE suggests the involvement of the choroid in the mechanisms of the hypotensive response to the treatment. Key words: primary angle closure, SS-OCT, choroidal thickness, laser peripheral iridotomy, lens extraction

Machine learning-couched treatment algorithms tailored to individualized profile of patients with primary anterior chamber angle closure predisposed to the glaucomatous optic neuropathy.

Primary angle closure glaucoma (PACG) is still one of the leading causes of irreversible blindness, with a trend towards an increase in the number of patients to 32.04 million by 2040, an increase of 58.4% compared with 2013. Health risk assessment based on multi-level diagnostics and machine learning-couched treatment algorithms tailored to individualized profile of patients with primary anterior chamber angle closure are considered essential tools to reverse the trend and protect vulnerable subpopulations against health-to-disease progression. To develop a methodology for personalized choice of an effective method of primary angle closure (PAC) treatment based on comparing the prognosis of intraocular pressure (IOP) changes due to laser peripheral iridotomy (LPI) or lens extraction (LE). The multi-parametric data analysis was used to develop models predicting individual outcomes of the primary angle closure (PAC) treatment with LPI and LE. For doing this, we suggested a positive dynamics in the intraocular pressure (IOP) after treatment, as the objective measure of a successful treatment. Thirty-seven anatomical parameters have been considered by applying artificial intelligence to the prospective study on 30 (LE) + 30 (LPI) patients with PAC. Based on the anatomical and topographic features of the patients with PAC, mathematical models have been developed that provide a personalized choice of LE or LPI in the treatment. Multi-level diagnostics is the key tool in the overall advanced approach. To this end, for the future application of AI in the area, it is strongly recommended to consider the following:Clinically relevant phenotyping applicable to advanced population screeningSystemic effects causing suboptimal health conditions considered in order to cost-effectively protect affected individuals against health-to-disease transitionClinically relevant health risk assessment utilizing health/disease-specific molecular patterns detectable in body fluids with high predictive power such as a comprehensive tear fluid analysis. The online version contains supplementary material available at 10.1007/s13167-023-00337-1.

Inside-out and outside-in: Tips and tricks in posterior lenticonus.

Posterior lenticonus is a congenital condition characterized by the thinning and bowing of posterior lenticular capsule. Cataract develops when normal intra-lenticular pressure bulges the posterior capsule at the circumscribed portion of inherent thin posterior lens capsule, leading to derangement of lamellar lens fibers. This condition poses a surgical challenge as the presentation varies from thin, bulging posterior capsule to large, pre-existing posterior capsular dehiscence. This video highlights the tips for the surgical management of various scenarios of posterior lenticonus. In this video, tips for surgical management of various scenarios of posterior lenticonus are illustrated. Intraoperatively, ruptured posterior capsule is suspected by the presence of a fish-tail sign. The anterior capsulotomy is relatively easier in a flatter anterior lens capsule, owing to reduced intra-lenticular pressure. Hydro-dissection is avoided to prevent extension of pre-existing posterior capsular dehiscence or creation of rupture in a thinned-out capsule. The peripheral lens cortex aspiration is initiated first, followed by in each quadrant. In a presence of ruptured posterior capsule by vigilant inspection at this stage, the surgeon should change the direction of lens matter aspiration by aspirating the central lenticular matter first, followed by peripheral cortex like "inside-out". In absence of posterior capsule dehiscence, peripheral cortex is aspirated first, followed by central lens matter aspiration like "outside-in". Adequate anterior vitrectomy is performed until there are no vitreous tags. In the presence of pre-existing posterior capsular defect, the lens matter is aspirated from the center (inside-out), whereas in the absence of capsular defect, the lens matter is aspirated from the periphery (outside-in). https://youtu.be/8G6BCbFwr8Q.

Impacts of the gradient-index crystalline lens structure on its peripheral optical power profile

Abstract The crystalline lens makes an important contribution to the peripheral refraction of the human eye, which may affect the development and progression of myopia. However, little has been known about the peripheral optical features of the crystalline lens and its impacts on the peripheral ocular refraction. This study aims to investigate the relationship between the structural parameters of the crystalline lens and its peripheral power profile over a wide visual field. The peripheral power profile is defined with respect to the entrance and exit pupil centers along the chief rays. Analysis is performed by three-dimensional ray tracing through the gradient refractive index (GRIN) lens models built from measurement data. It has been found that the vergence of the wavefronts at the entrance and the exit pupil centers of the lens show an approximate linear correlation to each other for each field angle. The exponent parameters of the axial refractive index profile and the axial curvature profile, and the asphericity of the posterior lens surface are found to be the most influential parameters in the peripheral power profiles. The study also shows that there can be significantly different, sometimes unrealistic, power profiles in the homogeneous lens model compared with its corresponding GRIN model with the same external geometry. The theoretical findings on the peripheral lens properties provide a new perspective for both wide-field eye modelling and the design of intraocular lenses to achieve normal peripheral vision.

Angle closure secondary to lens remnants in a patient with presumed aphakia: case report

BackgroundEyes with a short axial length or anterior chamber depth often develop narrowed anterior chamber angles in association with an enlarging crystalline lens. We report a case of a patient who presented in angle closure, with a distant history of prior intervention for congenital cataracts and was presumed to be aphakic.Case presentationA 78-year-old male presented with acute onset unilateral eye pain and blurred vision. He was found to have increased intraocular pressure, anteriorly bowed iris, and angle closure. Despite prior documentation of aphakia after treatment for congenital cataracts, detailed workup revealed residual crystalline lens material pushing the peripheral iris anteriorly. Further history confirmed that the patient underwent a procedure in the 1940’s to remove lens material centrally but was not truly aphakic. The patient was treated with anterior chamber paracentesis and intraocular pressure lowering drops. His intraocular pressure remains controlled with medical therapy alone.ConclusionsPatients that appear to be aphakic centrally may still present with angle closure secondary to residual peripheral lens material. This case highlights the importance of keeping this etiology on the differential in a patient with presumed aphakia.

Eph-ephrin Signaling Affects Eye Lens Fiber Cell Intracellular Voltage and Membrane Conductance.

The avascular eye lens generates its own microcirculation that is required for maintaining lifelong lens transparency. The microcirculation relies on sodium ion flux, an extensive network of gap junction (GJ) plaques between lens fiber cells and transmembrane water channels. Disruption of connexin proteins, the building blocks of GJs, or aquaporins, which make up water and adhesion channels, lead to lens opacification or cataracts. Recent studies have revealed that disruption of Eph-ephrin signaling, in particular the receptor EphA2 and the ligand ephrin-A5, in humans and mice lead to congenital and age-related cataracts. We investigated whether changes in lens transparency in EphA2 or ephrin-A5 knockout (–/–) mice is related to changes in GJ coupling and lens fluid and ion homeostasis. Immunostaining revealed changes in connexin 50 (Cx50) subcellular localization in EphA2–/– peripheral lens fibers and alteration in aquaporin 0 (Aqp0) staining patterns in ephrin-A5–/– and EphA2–/– inner mature fiber cells. Surprisingly, there was no obvious change in GJ coupling in knockout lenses. However, there were changes in fiber cell membrane conductance and intracellular voltage in knockout lenses from 3-month-old mice. These knockout lenses displayed decreased conductance of mature fiber membranes and were hyperpolarized compared to control lenses. This is the first demonstration that the membrane conductance of lens fibers can be regulated. Together these data suggest that EphA2 may be needed for normal Cx50 localization to the cell membrane and that conductance of lens fiber cells requires normal Eph-ephrin signaling and water channel localization.

Intraocular endoscopy: A review.

Optimal visualization is one of the most challenging aspects of performing vitreoretinal surgery. In situations where conventional microscopic techniques provide poor posterior visualization, the adjunctive skill set of endoscopic visualization may be needed. This allows for by-passing the opaque anterior segment media and getting access to the posterior segment pathology. Endoscopic vitrectomy is a useful and unique adjunct to microincision vitreoretinal surgery. The optical set-up of endoscopy allows for clinical approaches that are impossible with regular microscope viewing systems. These include the ability to observe across optically significant anterior segment opacities and directly visualize the posterior segment of the eye. It also allows for visualizing the difficult-to-access retroirideal, retrolental, and anterior retinal structures. Surgical access to anatomic spaces like the pars plana, pars plicata, ciliary sulcus, ciliary body, and peripheral lens is tedious. This is made simpler by endoscopy. In this review, we summarize and review the usage of the intraocular endoscope as a diagnostic and therapeutic armamentarium across a wide spectrum of ocular pathologies.

Re:bodying the virtual

This visual essay is composed of an associative thread of images that are sourced from several collaborative projects we (A + R) have conducted over the past six years. The context in which these collaborations took place include a symposium, exhibitions, various video works, and the teaching of a semi-virtual interior design studio in Melbourne. A crucial aspect within these situations was a shared spatial and didactical praxis that was located on opposite sides of the planet?—?Belgium and Australia. The collaboration was thus largely determined by the gaps between A + R: the geographical separation, the physicality or virtuality of site, and the millisecond delay of the video feed. The virtual screen that speared through each interaction meant that the technologies and processes employed were often undulating attempts to minimise these gaps. To compose this visual essay, the image archive of each collaborative project was examined through a peripheral lens, in order to create relations that interrogate the spatial and conceptual implications of bridging this physical distance. The anachronistic approach to the images allowed new forms of configurations to arise, emphasising the specific spatial situations over any previous context or anecdotal chronology. As a consequence, elaborating on the precise details of each project seems to be somewhat beside the point. In fact, prosaic descriptions detract from what is actually important about these interactions. The textual interspersions throughout the essay are attempts to develop a syntax for pointing out what is conceptually relevant. They try to unpack?—?or make more accessible?—?the visual argumentation that the essay is constructed from, without ever claiming or providing unisonal clarity. The words do not function as explanations, but instead as musings that attempt to mark?—?and disclose?—?the various typologies, as well as to narrate the transition between them. They are attempts to describe both the experience of the digital landscape and the terrain itself. In these thematic paragraphs, we have attempted to find language that resonates with the configurations of site that come together through the juxtapositions within the visual sequence. The collected imagery has been curated to lay bare the constituting components of this shared experience within digital space. In this way, the essay as a whole can be read as a subjective taxonomy of our digital communication of place as well as a truly digital simultaneous compression of it into one singular entity. Ultimately, the resulting transmedial constellation of images, text, places, objects, and projects aims to interrogate the kind of interiorities that are generated when two bodies interact from distant locations through predominantly digital platforms. It describes an exchange between the virtual spaces that we occupy and the physicality of the bodies and objects that remain essential for this virtual occupation.

Prosthetic replacement of the ocular surface ecosystem for corneal irregularity: Visual improvement and optical device characteristics

To describe patterns of prescribing Prosthetic Replacement of Ocular Surface Ecosystem (PROSE) in irregular corneas and compare various components of lens design. Design: Retrospective, observational case series. 244 eyes of 173 patients with keratoconus (n=178), pellucid marginal degeneration (n=21), keratoglobus (n=6), following refractive surgery (n=19) and following keratoplasty (n=20) fitted with the PROSE device were retrospectively analyzed. Simulated keratometry value along the steep meridian (Steep-K) and anterior chamber depth (ACD) were measured using Scheimpflug imaging. Improvement in visual acuity and parameters of lens design such as vault, front surface eccentricity (FSE) and toricity were analyzed and compared across all conditions. PROSE improved visual acuity, both uncorrected (median, 1.30 logMAR) and spectacle-corrected (median, 0.60 logMAR), to a median of 0.22 logMAR. Positive correlation was observed between Steep-K and ACD with lens vault, especially in keratoconus. Multiple regression analysis established ACD as the most reliable factor while choosing vault. FSE value of 0.6 was the most common across diagnostic subgroups. The distribution of FSE values did not differ between keratoconus patients with Steep keratometry of <60D or those >60D. In every diagnostic subgroup, at least 20% of eyes required a lens design of with-the-rule toricity of haptic. The PROSE device resulted in significant improvement in vision in this population. A trend of prescribing higher lens vault with increased keratometry value was evident especially in keratoconus. ACD appeared to be more important than Steep K in vault selection. An FSE of 0.6 and vertical peripheral lens toricity were used most frequently in this subset of patients.

English

AIM OF THE STUDY: To clinically analyse visual outcome and intraocular pressure control in surgically treated cases of lens induced glaucoma. MATERIALS AND METHODS: 100 patients with LENS INDUCED GLAUCOMA attending glaucoma services of Regional Institute of Ophthalmology and Government Ophthalmic Hospital were included in the study. Patients with presence of phacolytic, phacomorphic, lens particle, phaco anaphylaxis glaucoma and subluxated or dislocated lens with elevated intraocular pressure were included in the study. Patients with previous history of Primary Open Angle glaucoma and primary angle closure glaucoma, other secondary glaucomas, uncontrolled diabetes and IHD were excluded. All were subjected to detailed anterior segment examination, best corrected visual acuity, intraocular pressure measurement either by Goldmann applanation tonometry or in cases with presence of corneal edema rebound tonometry reading was recorded, fundus examination, gonioscopic examination were done. Surgical procedures like SICS/ECCE or combined surgery in cases with peripheral anterior synechiae or lens removal with secondary iol implantation were done. Surgical complications were analysed in patients undergoing sics/ecce/lens removal with secondary IOL and combined surgery and followed up periodically with visual acuity and intraocular pressure measurements and gonioscopic examination. RESULTS: In our study, 52% cases were in the age group of 56 -60 years, there was a slight male preponderance (59%), 47% presented with an IOP of 28-32mmhg. 60% cases were phacolytic glaucomas, 29% were phacomorphic glaucomas, 10% were lens particle glaucomas, 1% was due to subluxated lens induced glaucoma. 72% cases had PCIOL in other eye, 57% had a visual acuity in 6/36-6/18 range in other eye. At the end of six weeks the visual acuity for maximum number of cases (55%) was in the range 6/36-6/18, 20% cases had vision of range 3/60-6/60, 20% cases had vision of range 6/12-6/9. Hence visual improvement occurred in 95% of cases at the end of sixth post-operative week. 68% of cases had striate keratopathy, Post-operative iritis was present in all cases (100%), zonular dehiscence occurred in 43% cases, 12% cases had posterior capsular rent and 5% cases had vitreous loss. Out of 10 lens particle glaucoma cases, 50% (5 cases) had a good vision of 6/12 when compared to other types of lens induced glaucoma. Intraocular pressure was in the range of 12-14mmhg in 60% cases, 16-18mmhg in 40% cases at the end of six weeks. CONCLUSION: In our study, most of the patients had good vision in fellow eye and PCIOL status. This shows that patients ignored the reduced vision in affected eye due to good vision in fellow eye so their daily life was not affected until they developed symptoms. In lens induced glaucoma, surgery is the main stay of treatment after adequate control of intraocular pressure and inflammation with medications. Following surgery, intraocular pressure reduction occurs in all cases and visual improvement occurs in 95% cases.

Anterior segment parameters and tear functions in patients with thalassemia major

Aim: To determine whether the biomicroscopic, topographic and biomechanical properties of the anterior segment and the tear function have changed in Thalassemia Major (TM) patients.Material and Methods: Eighty-eight eyes of patients with TM and 102 eyes of healthy controls paired with age, gender, and spherical equivalent were included in this cross- sectional case-control study. Biomicroscopic, topographic and biomechanical findings of anterior segment and Schirmer test measurements were compared between the two groups.Results: The mean age was found to be 15.11±6.01years in TM group, and 13.83±4.92 years in the control group (p=0.17). In 34 (38.63%) patients with TM, minor peripheral lens opacities were detected. Visual acuity was 20/20 in all patients with lens opacity. The mean iridocorneal angle (ICA) was 44.67±5.86 and the topographic anterior chamber depth (ACD) was 3.65±0.28 mm in the TM patients. Mean ICA was 48.78 ± 6.51 and topographic ACD was 3.76±0.30 mm in the control group (p0.001 and P=0.02 respectively). The mean Schirmer test result was 14.06±4.13 mm in patients with TM and 16.2±3.75 mm in the control group (p=0.001).Conclusion: In contrast to previous literature, we did not found any vision decreasing complications in the TM group. Although peripheral lenticular opacities were detected in some of the patients with TM, none of the patients had an anterior segment finding that could reduce visual acuity. Intraocular lens calculation formulas and surgical technique may be affected due to decreased ICA and ACD values in patients with TM.

Visualization of adult fish lens fiber cells

The crystalline lens of a vertebrate eye is a gradient-index lens and grows throughout life by addition of new lens fiber cells in the periphery. In fish, the growing ball-shaped lens maintains sophisticated optical properties throughout life by maintaining the distribution of refractive index relative to the increasing radius of the lens. During this process, the central fibers must increase refractive index by increasing the cytosolic concentration of crystallin proteins. However, only the youngest, most peripheral lens fiber cells have the ability to synthesize proteins. Unfortunately, the hardness of fish lenses makes investigation of the cellular anatomy impossible with traditional histological methods. We have developed a method for visualizing lens fiber cells across the diameter of the lens in adult fish. The method relies on sectioning embedded lenses with a high-speed power saw and observing the cut surface with a scanning electron microscope (SEM). The combination of SEM and image analysis allowed for precise tracking of the positions of individual cell fiber cells. As an application of the method, we present a cell thickness profile, i.e. the distribution of cells thicknesses and their relative positions along the lens's radius. Combined with detailed optical studies, which by mathematical reasons only are possible on ball-shaped lenses, our method can lead to new insights into the mechanism governing the functional and cellular development of vertebrate lenses.

Vitrector induced lens injury during peripheral iridectomy in implantable collamer lens surgery

A 38-year-old female underwent bilateral implantable collamer lens (ICL) implantation for hyperopic astigmatism. While performing intraoperative peripheral iridectomy (PI), iris and anterior lens capsule was drawn to anterior vitrectomy cutter which result in large PI and injury to anterior lens capsule. Anterior lens capsule injury closed by fibrosis and the patient has 20/20 vision and static traumatic lens changes without any undesirable sequelae at the last follow up. Performing PI preoperatively by laser or alternatively by scissor intraoperatively is advisable to avoid above mentioned complication and a close observation is recommended when lens injury encountered.

Computational simulation of aqueous humour dynamics in the presence of a posterior-chamber versus iris-fixed phakic intraocular lens.

PurposeTo compare aqueous humour (AH) dynamics in the presence of a precrystalline (Implantable Collamer Lens®; ICL) or iris-fixed (Artiflex®) phakic intraocular lens (PIOL).MethodsBy computational fluid dynamics simulation, AH flow was modelled through a peripheral iridotomy (PI) or central lens hole (both 360 μm) in the presence of an Artiflex or ICL lens, respectively. The impacts of AH flow were then determined in terms of wall shear stress (WSS) produced on the endothelium or crystalline lens. Effects were also modelled for different scenarios of pupil diameter (PD 3.5 or 5.5 mm), ICL vault (100, 350, 800 μm) and number of Artiflex iridotomies (1 or 2) and location (12 or 6 o’clock).ResultsFor a PD of 3.5 mm, AH volumes flowing from the posterior to the anterior chamber were 37.6% of total flow through the lens hole (ICL) and 84.2% through PI (Artiflex). For an enlarged PD (5.5 mm), corresponding values were 10.3% and 81.9% respectively, so PI constitutes a very efficient way of evacuating AH. Central endothelial WSS in Pa was lower for the large vault ICL and the Artiflex (1−03 and 1.1−03 respectively) compared to the PIOL-free eye (1.6−03). Crystalline lens WSS was highest for the lowest vault ICL (1−04).ConclusionsAH flow varied according to the presence of a precrystalline or iris-fixed intraocular lens. Endothelial WSS was lower for an implanted ICL with large vault and Artiflex than in the PIOL-free eye, while highest crystalline WSS was recorded for the lowest vault ICL.

Peripheral Defocus of the Monkey Crystalline Lens With Accommodation in a Lens Stretcher.

PurposeTo characterize the peripheral defocus of the monkey crystalline lens and its changes with accommodation.MethodsExperiments were performed on 15 lenses from 11 cynomolgus monkey eyes (age: 3.8–12.4 years, postmortem time: 33.5 ± 15.3 hours). The tissue was mounted in a motorized lens stretcher to allow for measurements of the lens in the accommodated (unstretched) and unaccommodated (stretched) states. A custom-built combined laser ray tracing and optical coherence tomography system was used to measure the paraxial on-axis and off-axis lens power for delivery angles ranging from −20° to +20° (in air). For each delivery angle, peripheral defocus was quantified as the difference between paraxial off-axis and on-axis power. The peripheral defocus of the lens was compared in the unstretched and stretched states.ResultsOn average, the paraxial on-axis lens power was 52.0 ± 3.4 D in the unstretched state and 32.5 ± 5.1 D in the stretched state. In both states, the lens power increased with increasing delivery angle. From 0° to +20°, the relative peripheral lens power increased by 10.7 ± 1.4 D in the unstretched state and 7.5 ± 1.6 D in the stretched state. The change in field curvature with accommodation was statistically significant (P < 0.001), indicating that the unstretched (accommodated) lens has greater curvature or relative peripheral power.ConclusionsThe cynomolgus monkey lens has significant accommodation-dependent curvature of field, which suggests that the lens asserts a significant contribution to the peripheral optical performance of the eye that also varies with the state of accommodation.

Further Enhancement of Intraocular Open-Capsule Devices for Prevention of Posterior Capsule Opacification.

PurposeWe improve the intraocular open-capsule devices (IOCD) for the prevention of posterior capsule opacification (PCO).MethodsA total of 45 New Zealand rabbit eyes were divided into six similar groups after crystalline lens evacuation. Each group was implanted with a hydrophilic intraocular lens (IOL) and a hydrophilic IOCD of different designs. In the first experiment (Part A), a square design ring with and without large apertures was compared to a round design ring without apertures. In the second experiment (Part B), a square design ring with large apertures was compared to square design IOCDs with small apertures of high and low density. PCO and Soemmering's ring were evaluated clinically, by the Miyake Apple view, and histologically. The results were compared to a control group of eyes implanted with a hydrophilic IOL only.ResultsAll devices showed significant prevention of PCO and Soemmering's ring compared to the control group. Part A: the square design with apertures had the lowest level of peripheral lens epithelial cells proliferation (protrusions). Part B: modifying the size and density of the apertures had no influence on those protrusions.ConclusionsThe IOCD significantly reduced the rate of PCO and its precursor, Soemmering's ring. The rings with the square edges and apertures produced the best results. The study was underpowered to determine the influence of the apertures design.Translational RelevanceThe IOCD has the potential to prevent up to 80% of the PCO cases; the most common complication after cataract surgery. The design of the ring is important for its success.