Anterior Zonules Research Articles

Successful Management of Cataract in Patient With Long Anterior Zonules and Small Pupil :A Rare Case

Introduction : Long anterior zonules (LAZ) are rare disease with prevalence was 1–2%, characterized by zonular fibers that extend centrally leading to a small zonule-free zone (ZFZ), which raises the risk of complications during zonular cutting while continuous curvilinear capsulorhexis (CCC). This leads to two options whether to perform phacoemulsification through a small CCC within the small ZFZ or an adequately sized CCC. The objective of this study was to report challenging management of phacoemulsification surgery with LAZ eyes with small pupil
 Case Illustration : A 62 y.o female had visual acuity(VA) 0.7(logMAR) due to corticonuclear cataract in left eye. She had history complicated cataract surgery with secondary sulcus fixated IOL in her fellow eye. The IOP was normal, no phacodenesis and pseudoexfoliative material observed in left eye. The posterior segment was normal. The left eye observed otherwise normal in initial examination. Intraoperatively, after viscomidriasis technique the ZFZ identified in the area of 2.0-2.5 mm from central. Five millimeter CCC can be achieved in the central area and phacoemulsification with the help of CTR (Capsular Tension Ring) safely performed and one piece IOL was implanted in the bag.
 Discussion : On the first postoperative day, VA was improves to 0.4(logMAR), IOL central and clear corneal with minimal inflammation. One week after surgery, the VA 0.3(logMAR) and no sign of IOL decenteration.
 Conclusion : Phacoemulsification in eyes with LAZs can be safely performed with CTR through an adequately sized CCC without significant complications. A combination of early recognising high-risk eye, proficient skills, and surgical instruments can improve outcome.

The major influence of anterior and equatorial zonular fibres on the far-to-near accommodation revealed by a 3D pre-stressed model of the anterior eye

PurposeTo explore the synergistic function of the ligaments in eye, the zonular fibres, that mediate change in eye lens shape to allow for focussing over different distances. MethodsA set of 3D Finite Element models of the anterior eye together with a custom developed pre-stress modelling approach was proposed to simulate vision for distant objects (the unaccommodated state) to vision for near objects (accommodation). One of the five zonular groups was cut off in sequence creating five models with different zonular arrangements, the contribution of each zonular group was analysed by comparing results of each specific zonular-cut model with those from the all-zonules model in terms of lens shape and zonular tensions. ResultsIn the all-zonular model, the anterior and equatorial zonules carry the highest tensions. In the anterior zonular-cut model, the equatorial zonular tension increases while the posterior zonular tension decreases, resulting in an increase in the change in Central Optical Power (COP). In the equatorial zonular-cut model, both the anterior and posterior zonular tensions increase, causing a decreasing change in COP. The change in COP decreases only slightly in the other models. For vitreous zonular-cut models, little change was seen in either the zonular tension or the change in COP. ConclusionsThe anterior and the equatorial zonular fibres have the major influence on the change in lens optical power, with the anterior zonules having a negative effect and the equatorial zonules contributing a positive effect. The contribution to variations in optical power by the equatorial zonules is much larger than by the posterior zonules.

Anterior segment phenotypic changes in late-onset retinal degeneration with Ser163Arg mutation in CTRP5/C1QTNF5.

Late-onset retinal degeneration (L-ORD) is a rare retinal dystrophy with anterior segment (AS) abnormalities, including long anterior zonules (LAZ) and iris atrophy. This investigation evaluates AS changes in a L-ORD cohort. Prospective, longitudinal study including L-ORD individuals (Ser163Arg) with ocular exam and standard slit-lamp photographs between 2011 and 2022. AS images were merged and assessed for LAZ number and zonule-free zone (ZFZ) radius. Further clinical findings such as iris atrophy patterns were reported descriptively. Twelve eyes of 6 patients (4 males, median age = 60.5years) were included, showing a median of 160 (11-372) LAZs, mainly localized superiorly (39%) and inferiorly (24%). There was a high inter-ocular correlation (rs = 0.94, p < 0.01), no difference in LAZ count between eyes (p = 0.82), and an inverse relationship between LAZ and age (r = - 0.82; p < 0.05). The ZFZ had median 2.1mm (1.3-5.4), with no inter-ocular difference (p = 0.31). Iris transillumination defects occurred in 11/12 eyes, with 4 major patterns identified: pupillary ruff rarefaction (10/12), patchy atrophy (6/12), notched defects (6/12), and radial streaks (2/12). In a short-term follow-up of 5.9years, 4 eyes showed a reduction in LAZ count to median 139.5 (67-169) (p = 0.50) and a concomitant increase in ZFZ measurement to median 2.2 (1.7-2.6) (p = 0.17). This study confirms symmetric LAZs count and ZFZ in L-ORD, with ZFZ measurements smaller than in previous cohorts. A reduction in LAZs count and an increase in ZFZ with age were suggested longitudinally, yet findings need further evaluation as follow-up was limited to two cases.

Late-Onset Retinal Degeneration: Clinical Perspectives.

Late-onset retinal degeneration (L-ORD) is a type of retinal dystrophy marked by nyctalopia and subretinal pigment epithelium deposits, which eventually promote retinal atrophy with final visual compromise. L-ORD may also present with changes in the anterior segment, notably long anterior zonules and iris atrophy, distinguishing it from other inherited eye conditions. Although it can clinically simulate age-related macular degeneration, L-ORD has a different course of progression and prognosis, requiring adequate diagnosis for patient counseling. This review summarizes the main clinical, genetic, pathophysiological, diagnostic, and therapeutic aspects of L-ORD to help ophthalmologists identify and manage this rare ocular disease.

Long anterior lens zonules with retinal stripes: a case report

BackgroundLong anterior lens zonules (LAZs) is a rare disease that was mostly conducted among African Americans. Through the observation of a Chinese patient, we discoverd that the disease may show different characteristics in Asians.Case presentationA patient with vision loss due to a macular hole was found to have several special clinical signs during vitrectomy combined with phacoemulsification and intraocular lens implantation surgery in our hospital, including radially oriented lines on the anterior capsule with pigment, a shallow anterior chamber, slightly high intraocular pressure, and radial retinal stripes in the peripheral retina. Finally, he was diagnosed with long anterior lens zonule syndrome.ConclusionClinicians need to pay more attention to the rare disease LAZs. It is important to tear the appropriate size of the anterior capsule so as to avoid radial capsular tearing and intraocular lens dislocation.

The Zonular Stripes

Long anterior zonules [LAZ] are zonules having anomalous anterior insertion on the lens capsule, thus reducing the size of zonule-free zone. This article describes a diabetic elderly female who presented to us for cataract surgery. Examination showed presence of bilateral persistent pupillary membrane [PPM] along with long anterior zonules. Association of PPM with LAZ has been established in literature but bilateral PPM-LAZ association is a unique finding. The article also illustrates different phenotypes of LAZ and their clinical associations. LAZ eyes have propensity for sight threatening diseases like glaucoma, retinal diseases etc. Hence, a thorough ocular examination is warranted.

Long Anterior Zonules and Angle Closure Disease.

Angle closure disease was present in 59.3% of eyes with long anterior zonules (LAZ). The cause is multifactorial including a thick anteriorly positioned crystalline lens, shorter axial length, and increased lens thickness to axial length factor. To study the profile of eyes with LAZ presenting in a glaucoma clinic in a tertiary eye care centre and understand the pathogenesis of angle closure disease in these eyes. This was a retrospective cross-sectional study.All patients with LAZ seen from January 2014 to December 2018 were included. Demographic and clinical characteristics were noted. LAZ eyes (177 eyes of 177 patients) were compared with an equal number of age and sex-matched controls. LAZ was defined as radially oriented zonular fibers (both pigmented and nonpigmented), extending central to the normal zonular termination zone on the anterior lens surface >1 mm beyond their usual insertion of 1.42±0.24 mm from the lens equator onto the mid peripheral zone or central to it, as seen on slit-lamp examination, following pupillary dilation by a single examiner. Glaucoma was defined according to the International Society for Geographical and Epidemiological Ophthalmology classification. The following biometric parameters were compared: anterior chamber depth (ACD), axial length (AXL), lens thickness (LT), lens position (LP=ACD+0.5×LT), relative lens position (RLP=LP/AXL); lens thickness to axial length factor (LAF=(LT/AXL)×10). LAZ eyes without angle closure disease were also compared with controls. Mean age of patients with LAZ was 64.8±8.1 years. Of these, 63.3% were females. Angle closure disease was present in 59.3% (105/177) patients. Majority of these eyes were primary angle closure suspects (PACS) (53.3%, n=56). Significant differences were found between LAZ eyes and controls for LT (4.8±0.38 mm vs. 4.49±0.40 mm, P<0.0001), ACD (2.68±0.39 mm vs. 3.0±0.32 mm, P<0.0001), AXL (22.37±0.79 mm vs. 22.94±1.1, P<0.0001), LAF (2.14±0.19 vs. 1.96±0.21, P<0.0001), and LP (5.07±0.37 vs. 5.3±0.25, P<0.0001). Angle closure was present in more than half the eyes with LAZ. Majority of these eyes were PACS or had primary angle closure. LAZ eyes had a thicker lens, shallow AC, a shorter axial length and an increased LAF as compared with age and sex matched normal controls. The presence of LAZ may be an indicator of increased risk for angle closure.

Ocular characteristics and phacoemulsifi cation in eyes with long anterior zonules

Ocular characteristics and phacoemulsifi cation in eyes with long anterior zonules

Krukenberg's Spindles Strongly Suggest Long Anterior Zonule Associated Pigment Dispersion Mechanism in Older Patients.

PurposeThe purpose of this study was to further investigate factors associated with Krukenberg’s spindle (KS) presence in a primary eye care setting.MethodsAs part of a larger investigation, several practitioners in an academic eye care facility in Chicago, IL, USA evaluated patients for the long anterior zonule (LAZ) trait during 2011 to 2018, and data were collected on ocular/systemic health, lifestyle, and demographic variables, including the presence of a KS. Multivariate regression was used to assess relationships to KS presence.ResultsAnalysis included 3501 subjects with mean age of 51 ± 15 years (18–98 years; 65% women; and 84% African American). Among the right eyes, 57 (1.6%) had a KS, with this group having a mean age of 62 ± 13 years (25–86 years; 75% women; and 82% African American). There were 120 subjects (3.4%) with right eye LAZ, with mean age of 64 ± 11 years (36–91 years; 77% women; and 92% African American). There were 19 of 57 (33.3%) KS eyes that also had LAZ. Controlling for other factors, variables with the strongest relationship to KS presence were the LAZ trait (odds ratio [OR] = 12.2, 95% confidence interval [CI] = 6.5 to 22.8, P < 0.0001) and advancing age (OR = 1.3 per decade, 95% CI = 1.3 to 1.9, P < 0.0001).ConclusionsIn the population studied, KS presence had its strongest relationship to the LAZ trait and advancing age. The KS-LAZ relationship may not be well-known, but these data strongly suggest that pigment dispersion signs, such as a KS, should prompt the clinician to consider the LAZ trait as a potential etiology, especially because LAZ is associated with higher IOP and possibly glaucoma.

Phacoemulsification in eyes with long anterior zonules.

To study the safety of phacoemulsification in eyes with long anterior zonules (LAZs). Institute. Retrospective interventional case series. All patients with clinically proven LAZs who had undergone phacoemulsification by a single surgeon from January 2014 to December 2018 were included. All cases of LAZs with cataract extraction by procedures other than phacoemulsification or combined with any other ocular surgery were excluded. Sixty-five eyes of 52 patients were analyzed. Phacoemulsification with capsulorhexis that involves sacrificing the LAZs was performed. The primary outcome measures were the incidence of capsulorhexis extension or the need to rescue intraoperatively and the rate of intraoperative complications. Secondary outcomes assessed were the percentage of eyes within ±0.5 diopters (D) and ±1 D of the target refraction. Sixty-five eyes (52 patients) were analyzed; the mean age of patients was 67.3 ± 7.4 years. The successful completion of an adequately sized capsulorhexis without extension or rescue was seen in 100% of cases. The incidence of intraoperative complications was 1.5% (posterior capsular rupture in 1 eye). The mean postoperative corrected distance visual acuity was 0.05 ± 0.1 (logarithm of the minimum angle of resolution) at a mean of 26.8 ± 7.6 days. The mean spherical equivalent was -0.15 ± 0.7 D. Eyes within ±0.5 D and ±1.00 D of the target refraction were 77% and 94%, respectively. Phacoemulsification in eyes with LAZs can be safely performed through an adequately sized capsulorhexis by sacrificing, ie, cutting or breaking, the anteriorly inserted zonules 360 degrees without significant intraoperative complications.

Current Concepts in True Exfoliation Syndrome.

True exfoliation syndrome is characterized by the peeling of a translucent membrane from the anterior lens capsule. The condition increases with age and despite the classic association with occupations involving intense heat, most cases are idiopathic. We have proposed a new clinical classification system dividing true exfoliation syndrome into 4 successive stages based on characteristic changes in the anterior capsule. We have also proposed a new mechanism related to iris movement and aqueous flow accounting for the capsular delamination. We have found that a detached flap occurs exclusively in areas that lack the anterior zonules. In our series of 259 consecutive patients, 47 (19.5%) patients developed primary open-angle glaucoma, 26 (10.0%) had primary angle-closure glaucoma, and 15 (5.8%) were primary angle-closure suspects. Twenty-six (10.0%) patients demonstrated spontaneous phacodonesis or anterior lens dislocation, of whom 14 also had secondary angle-closure and 2 had open-angle glaucoma. Histologic studies have shown that the lens dislocation is associated with a lack of anterior zonular support. All patients developed cataracts, predominantly nuclear sclerosis. The double-ring sign frequently occurs during capsulorhexis.

Long Anterior Lens Zonules and Intraocular Pressure.

PurposeTo investigate the relation between intraocular pressure (IOP) and the idiopathic long anterior zonule (LAZ) trait.MethodsPatients presenting for primary eye care were examined for LAZ, identified as radially oriented zonular fibers with central extension >1.0 mm beyond the normal anterior lens insertion zone (estimated via slit lamp beam length). Ocular, systemic health, and lifestyle data were collected via comprehensive exam and questionnaire. Multivariate regression was used to assess the relationship between IOP (Goldmann) and LAZ.ResultsThere were 2169 non-LAZ and 129 LAZ subjects (mean age: 49.8 ± 15.0 vs. 62.6 ± 10.2 years; 63.6% vs. 76.0% female; 83.2% vs. 91.5% African American). Right eyes with >trace LAZ (n = 59 of 110) had higher unadjusted mean IOP than control eyes (16.4 ± 3.3 vs. 15.0 ± 3.3 mm Hg, P = 0.005), and with control for numerous factors, LAZ eyes had an average IOP of approximately 1.3 ± 0.4 mm Hg higher (P = 0.003) than non-LAZ eyes. Final model covariates included sex (P = 0.001); spherical-equivalent refractive error (D; P < 0.0001); body mass index (kg/m2; P < 0.001); presence of diabetes (P < 0.001); having >high school education (P < 0.001); systolic blood pressure (mm Hg; P < 0.0001); being an ever smoker (P = 0.006); and having history of any site cancer (P = 0.01).ConclusionsThe LAZ trait, with potential prevalence near 2%, was associated with a higher IOP. This observation is consistent with the hypothesis that the trait is a marker for underlying mechanisms that elevate glaucoma risk.

Evaluation of changes in retinal fiber layer thickness in pseudoexfoliation syndrome using spectral domain optical coherence tomography

Background: Pseudoexfoliation syndrome (PEX) is a disorder characterized by the progressive accumulation of fibrillary extracellular deposits in several ocular tissues including the iris, anterior chamber angle, lens capsule, and zonules. It is an independent risk factor for glaucomatous optic nerve damage. Retinal nerve fiber layer thickness analysis using optical coherence tomography (RNFL-OCT) is a documented investigative tool to detect preperimetric glaucoma and helps to detect glaucoma early. Objective: The objective of this study was to evaluate the retinal nerve fiber thickness in eyes with PEX using OCT and to compare them with healthy controls. Materials and Methods: This prospective cross-sectional control study was conducted at GMC, Srinagar, in which retinal nerve fiber thickness 50 patients of PEX and 50 healthy control subjects were compared using Cirrus spectral domain OCT (Carl Zeiss). Complete ocular and physical examination was also done in all subjects. Results: Mean age of Group A (PEX group) was 59.06 ± 6.5 years and of Group B (control) was 57.04 ± 7.1 years (P = 0.51). Both groups were gender matched with male preponderance (P = 0.41). Mean average peripapillary RNFL thickness was 76.13 μm ± 13.65 in Group A (PEX group) and 82.61 ± 12.78 μm in Group B (control group) (P = 0.10). Mean superior RNFL thickness was 94.17 ± 16.25 in PEX group and 100.23 μm ± 13.21 in control group (P = 0.09). Mean inferior RNFL thickness was 89.67 μm ± 18.25 in PEX group and 102.45 μm ± 12.50 in control group (P = 0.03). Mean nasal RNFL thickness was 62.36 μm ± 15.36 in PEX group and 64.66 μm ± 13.71 (P = 0.56) in control group. Mean temporal RNFL thickness was 58.34 μm ± 14.32 in PEX group and 63.11 μm ± 15.25 (P = 0.08) in control group. Mean RNFL thickness was seen decreased in all PEX patients in all quadrants; however, statistically significant differences were detected only in inferior quadrant groups. Conclusion: RNFL thickness is decreased in PEX patients. SD-OCT is a very reliable investigative tool to measure RNFL thickness, which helps in detecting preperimetric glaucoma.

Morphologic Patterns Formed by the Anomalous Fibers Occurring Along the Anterior Capsule of the Crystalline Lens in People With the Long Anterior Zonule Trait

People with the long anterior zonule (LAZ) trait, which may have prevalence near 2%, have zonular fibers that extend more central than usual along the anterior capsule of the crystalline lens. The anomalous fibers can be observed in vivo with clinical slit lamp biomicroscopy after pharmacologic pupil dilation, and although minimally studied, the LAZ trait may have importance to glaucoma, retinal degeneration, and cataract surgery. To further characterize LAZ morphology, a custom computer program was used to trace LAZ fibers seen on retro-illumination photos acquired during previous study at an academic, urban eye care facility in Chicago, IL. There were 59 African-Americans (54 female; median age = 70 years, 53-91 years) included in the analysis. After initial review of the zonule tracings, we identified three basic LAZ patterns. We called one pattern (47% of right eyes) a "non-segmental LAZ pattern," which was predominated by fibers that could be visually traced to the dilated pupil border where they became obscured by the iris. Another pattern (35% of right eyes), the "segmental LAZ pattern," was predominated by fibers that appeared to terminate abruptly without detectable extension to the pupil border. The third pattern (18% of right eyes), the "mixed LAZ pattern," had a more equivalent mixture of the other two fiber morphologies. Compared to the "non-segmental" group, the "segmental" LAZ eyes had smaller central zonule-free zones (P < 0.0001), and they tended to exhibit fewer LAZ fibers (P = 0.07). These data improve understanding of LAZ clinical anatomy and may be helpful to future investigation. Anat Rec, 300:1336-1347, 2017. © 2017 Wiley Periodicals, Inc.

The Clinical Spectrum and a New Theory of Pathogenesis of True Exfoliation Syndrome

To describe the clinical spectrum and a new theory of pathogenesis of true exfoliation syndrome. Cross-sectional and prospective, observational case series. Consecutive patients with characteristic peeling of the anterior lens capsule. After maximal mydriasis, slit-lamp biomicroscopy, and photography, imaging of the anterior capsule and zonules was performed. The condition was classified into 4 clinical stages: annular anterior capsule thickening with a distinct splitting margin (stage 1), an inward detached crescentic flap lying on the anterior lens (stage 2), a floating and folding translucent membrane behind the iris (stage 3), and a broad membrane within the pupil (stage 4). Serial photography was performed at each 3-month follow-up visit. Ultrastructural examination of dislocated lenses and excised anterior capsules was performed. Detached membrane morphologic features, zonular defects, pigment deposition, glaucoma, phacodonesis, and cataract. We enrolled 259 patients (424 eyes). Ages ranged from 52 to 97 years (mean age, 75.2±7.1 years). Eleven patients were associated with trauma (n= 1) or intense heat (n= 10), whereas 248 were idiopathic. Two hundred ten patients were followed up every 3 months, with a mean follow-up of 9.6±6.1 months (range, 3-50 months). The detachment started along the anterior zonular insertions in association with zonular disruption. It progressed centrally to higher stages, manifesting a spectrum of disease. Several stages coexisted in a single eye. At the final visit, including 49 patients who were examined once, there were 70, 87, 85, and 17 patients in stages 1, 2, 3, and 4, respectively. All stages shared common histologic findings consisting of diffuse capsular lamellar separation and anterior zonular disruption. All developed cataract. Pigment deposition on the membrane was present in 178 patients (68.7%). Twenty-six patients (10%) had spontaneous phacodonesis. Eighteen eyes (4.2%) demonstrated secondary delamination. Capsular lamellar separation and anterior zonular disruption are characteristic findings. Aging, heat exposure, and trauma are risk factors. Initial capsular splits occur along the insertions of disrupted anterior zonules. The peeling progresses centrally in association with iris movement and aqueous flow. A second detachment can occur.

Anterior Chamber Depth, Lens Thickness, and Related Measures in African American Females With Long Anterior Zonules: A Matched Study With Control for Refractive Error.

To investigate anterior chamber depth (ACD), lens thickness (LT), vitreous body length (VBL), and axial length (AL) in African American females with long anterior zonules (LAZ) while controlling for refractive error. The eyes of 50 African American females with LAZ were compared with 50 controls matched with age, race, sex, and refractive error. Central ACD, LT, VBL, and AL measurements were obtained in a masked manner using a-scan ultrasonography. LAZ cases had a mean age±SD of 67.1±7.6 years (range, 52 to 85 y) and a mean refractive error of +1.85±1.41 D (-1.75 to +4.75 D). Parameters were similar for controls. Mean ACD for cases was 2.45±0.34 mm and 2.57±0.38 mm for controls. Mean LT for cases was 4.94±0.43 mm and 4.83±0.45 mm for controls. Mean VBL for cases was 15.00±0.72 mm and 15.17±0.76 mm for controls. Mean AL for cases was 22.39±0.82 mm and 22.57±0.76 mm for controls. Using multiple logistic regression to control for any residual differences in age and refractive error, no significant differences were present between LAZ eyes and control eyes relative to the a-scan variables (P>0.1). When refractive error was controlled for, this group of African American females with LAZ did not exhibit clinically significant differences in ACD, LT, VBL, and AL as compared with controls.

Clinical Associations of Long Anterior Zonules: A Review

Background and Aim: The presence of long anterior zonules [LAZ] in the eye was first described in 1907. They have been reported to be associated with potentially blinding ocular diseases like retinal degeneration and glaucoma. Despite this it is understudied and little is known about their pathophysiology and natural history. This review discusses the different aspects of the long anterior zonule phenotype and suggests areas for further research.Methods: We reviewed the available literature on eyes with LAZ and describe their characteristics and associations under different clinical subheadings.Conclusion: Current evidence suggests that patients with long anterior zonules need to be investigated carefully for associated retinal disease and glaucoma. Asymptomatic cases need to be followed up closely for the development of these potentially blinding ocular diseases. Prospective studies are required to shed more light on the inheritance ,pathogenesis and natural history of long anterior zonules.Keywords: long anterior zonules, glaucoma, late onset retinal macular degeneration, pigment dispersion, pigmented lens striae

Reviews, opinions and insights for future clinical trials: an overview of PPCR journal

Dear Colleagues, authors and readers of PPCR We are pleased to release the third issue of Principles and Practice of Clinical Research (PPCR – ISSN 2378- 1890). In this edition, four articles are available encompassing various areas of medical research. First, Camargo et al., in a short review, discuss skin anatomical characteristics and conditions that can influence endothelial function. In a second review, Khurana exposes the different aspects of the long anterior zonule phenotype and proposes some insights for future clinical trials. Thibaut & Laureys provide a systematic review on brain stimulations for patients with disorders of consciousness. The authors emphasize the importance of future controlled clinical trials to improve the understanding of potential treatments in such patients. Finally, Teixeira Santos et al. propose a mini review of the effects of transcranial direct current stimulation on working memory in elderly. They mention the interesting effects about it, however better parameters still need to be identified in order to improve the benefits of such stimulations. These four articles, that cover diversified areas of clinical research, provide a nice overview of the state of the art in each specific field, as well as interesting insights and the challenges that need to be addressed in future clinical trials. This issue illustrates the main goal of our journal, which is to promote the work and training of clinical researchers in various fields of research. We encourage our readers, both clinicians and researchers, to submit clinical trials, interesting case reports, study protocols or systematic review to our journal. We hope to receive many valuable manuscripts for the upcoming editions. With our very best regards!

Anteriorly located zonular fibres as a tool for fine regulation in accommodation.

To describe an anteriorly located system of zonular fibres that could be involved in fine-tuning of accommodation. Forty-six human and 28 rhesus monkey eyes were dissected and special preparations were processed for scanning electron microscopy and reflected-light microscopy. Additional series of frontal and sagittal histological and ultrathin sections were analysed in respect to the origin and insertion of anteriorly located zonules. The presence of sensory terminals at the site of the originating zonules within the connective tissue of the ciliary body was studied by immunohistochemistry. For in-vivo visualization ultrasound biomicroscopy (UBM) was performed on 12 human subjects. Fine zonular fibres originated from the valleys and lateral walls of the most anterior pars plicata that covers the anterior and inner circular ciliary muscle portion. These most anterior zonules (MAZ) showed attachments either to the anterior or posterior tines or they inserted directly onto the surface of the lens. At the site of origin, the course of the MAZ merged into the connective tissue fibres connecting the adjacent pigmented epithelium to the ciliary muscle. Numerous afferent terminals directly at the site of this MAZ-origin were connected to the intrinsic nervous network of the ciliary muscle. A newly described set of zonular fibres features the capabilities to register the tensions of the zonular fork and lens capsule. The close location and neural connection towards the circular ciliary muscle portion could provide the basis for stabilization and readjustment of focusing that serves fast and fine-tuned accommodation and disaccommodation.

The zonules selectively alter the shape of the lens during accommodation based on the location of their anchorage points.

To determine the role of anterior and posterior zonular tension on the optomechanical lens response during accommodation simulation. Ten eyes from nine hamadryas baboons (4.9 ± 0.7 years) and 20 eyes from 18 cynomolgus monkeys (5.4 ± 0.3 years) were dissected, leaving the lens, zonules, ciliary body, hyaloid membrane, anterior vitreous, and a segmented scleral rim intact. The lens preparation was mounted in a lens stretcher, and the outer scleral shell was displaced radially in a stepwise fashion. The load, lens, and ciliary body diameters, lens power, lens thickness, and the anterior and posterior radius of curvature were measured during stretching. The zonular fibers attached to either the posterior or anterior lens surface were then carefully transected and the experiment was repeated. Zonular transection was confirmed in four eyes via laser scanning confocal microscopy after immunostaining. The effect of zonular transection on the tissue response to stretching was quantified. Without anterior zonules, 48% and 97% of the changes in anterior and posterior radii are retained. Without posterior zonules, 81% and 67% of the changes in anterior and posterior radii are retained. The changes in lens shape were reduced after transecting either the anterior or posterior zonules; however, both surfaces still changed shape. While either the anterior or posterior zonules alone are capable of changing the shape of both lens surfaces, the anterior zonules have a greater effect on the anterior lens surface, and the posterior zonules have a greater effect on the posterior lens surface.