The lens capsule and zonulae

Ultrasound Biomicroscopy Observation of Suspicious Primary Angle Closure Combined with the Relaxation of Zonule

Purpose

To investigate the difference in anterior segment parameters between suspicious primary angle closure (PACS) patients and normal patients as assessed by ultrasound biomicroscopy (UBM).

Methods

From June 2019 to November 2020, 39 patients (50 eyes) with PACS in the Ophthalmology Department of Qingdao University Affiliated Hospital who underwent phacoemulsification and intraocular lens implantation were selected as the PACS group. 32 patients (50 eyes) who underwent phacoemulsification and intraocular lens implantation were selected as the normal group. In addition to routine preoperative examinations such as visual acuity, noncontact intraocular pressure, axis length (AL), and ocular B-ultrasound examination, UBM examinations were also performed, including measuring the central anterior chamber depth (ACD), the maximum transverse diameter of the ciliary process at both ends (STS), the vertical distance between the anterior apex of the lens and the maximum transverse diameter at both ends of the ciliary processes (h), and angle opening distance (AOD500), iris-zonule distance (IZD), trabecular-ciliary process distance (TCPD), trabecular-iris angle (TIA), iris thickness (IT), trabecular-ciliary process angle (TCPA), and anterior placement of the ciliary body (APCB) at four quadrants (superior, nasal, inferior, and temporal quadrants).

Results

Compared with the normal group, the PACS group showed statistically differences in AL, ACD, h, ACD/AL, h/STS, IZD, AOD500, TCPD, TIA, TCPA, and APCB (P < 0.05), and there were no significant differences in STS and IT between the two groups (P > 0.05). In the PACS group, there were significant differences in AL, ACD, h, ACD/AL, h/STS, IZD, TCPD, TCPA, and APCB between PACS patients with zonular relaxation and without zonular relaxation (P < 0.05), while there were no significant differences in STS, AOD500, TIA, and IT (P > 0.05).

Conclusion

UBM quantitatively enables to identify the anterior segment morphology, especially the zonules in patients of suspicious primary angle closure combined with the relaxation of zonule. Accurate measurement of UBM can be used to predict whether patients with PACS are combined with zonular relaxation, so as to provide a clinical imaging evidence for the diagnosis.

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 expression and function of netrin-4 in murine ocular tissues

Netrin-4, a member of the netrin family, is a potent regulator of embryonic development. It promotes neurite extension and regulates pulmonary airway branching, vasculogenesis patterning, and endothelial proliferation in pathological angiogenesis. The initial characterization of netrin-4 expression was focused on epithelial-derived organs (kidney, lung and salivary gland) and the central nervous system. Ocular development is an ideal system to study netrin-4 expression and function, as it involves both ectodermal (cornea, lens and retina) and mesodermal (sclera and choroid) derivatives and has an extensive and well-characterized angiogenic process. Netrin-4 is expressed in all ocular tissues. It is a prominent component of the basement membranes of the lens and cornea, as well as all three basement membranes of the retina: the inner limiting membrane, vascular basement membranes, and Bruch's membrane. Netrin-4 is differentially deposited in vascular basement membranes, with more intense anti-netrin-4 reactivity on the arterial side. The retinal microcirculation also expresses netrin-4. In order to test the function of netrin-4 in vivo, we generated a conventional mouse lacking Ntn4 expression. Basement membrane formation in the cornea, lens and retina is undisrupted by netrin-4 deletion, demonstrating that netrin-4 is not a major structural component of these basement membranes. In the Ntn4 homozygous null (Ntn4-/-) cornea, the overall morphology of the cornea, as well as the epithelial, stromal and endothelial stratification are normal; however, epithelial cell proliferation is increased. In the Ntn4-/- retina, neurogenesis appears to proceed normally, as does retinal lamination. In the Ntn4-/- retina, retinal ganglion cell targeting is intact, although there are minor defects in axon fasciculation. In the retinal vasculature of the Ntn4-/- retina, the distribution patterns of astrocytes and the vasculature are largely normal, with the possible exception of increased branching in the deep capillary plexus, suggesting that netrin-4 may act as a negative regulator of angiogenesis. These data, taken together, suggest that netrin-4 is a negative regulator of corneal epithelial cell proliferation and retinal vascular branching in vivo, whereas netrin-4 may be redundant with other members of the netrin family in other ocular tissue development. Ntn4-/- mice may serve as a good model in which to study the role of netrins in vivo of the pathobiologic vascular remodeling in the retina and cornea.

Contributions of mouse genetic background and age on anterior lens capsule thickness

Accurate lens capsule thickness measurements are necessary for studies investigating mechanical characteristics of the capsule. Confocal Z-axis imaging was used to measure the anterior lens capsule thickness of living intact lenses with minimal tissue manipulation. Measurements of the anterior capsule thickness is reported for the first time in young and old mice from four inbred strains, BALB/c, FVB/N, C57BL/6, and 129X1, and the outbred strain ICR. Our data demonstrates that the mouse anterior lens capsule continues to grow postnatally similar to that described in other mammals. It is also shown there is a significant difference in anterior lens capsule thickness between unrelated mouse strains, suggesting that capsule thickness is a quantitative trait shared by strains with common ancestry. Measurements, taken from other regions of FVB/N capsules revealed the anterior pole to be the thickest, followed by the equatorial region and posterior pole. In addition to mouse, anterior capsule measurements taken from intact cattle, rabbit, rat lenses, and human capsulotomy specimens correlated with the overall size of the animal.