Imaging of the Ciliary Body: A Major Review

The effect of aging on the ciliary muscle and its potential relationship with presbyopia: a literature review

Background

The ciliary muscle is known to play a part in presbyopia, but the mechanism has not received a comprehensive review, which this study aims to achieve. We examined relevant articles published from 1975 through 2022 that explored various properties of the muscle and related tissues in humans and rhesus monkeys. These properties include geometry, elasticity, rigidity, and composition, and were studied using a range of imaging technologies, computer models, and surgical methods. We identified a notable age-related displacement of the ciliary muscle apex that is characterized by anterior and medial shifts, and hypothesized to be primarily attributed to the accrual of connective tissue and tension exerted by the thickening lens. Other factors could also contribute to the movement, particularly the "inward bowing" of the sclera. Another noteworthy observation is that while the ciliary muscle experiences increasing constraint with advancing age due to adjacent anatomical structures, its contractile capacity remains unaltered, alongside the sustained constancy in both the concentration of muscarinic receptors and their binding affinity. Overall, more studies on human ciliary muscle are needed, as it ages differently from that of monkeys' ciliary muscle. These studies should explore other perspectives, including those regarding changes in the physical properties of the tissue and its relationship with other connected tissues.

Methodology

This literature review utilized a systematic methodology to identify and analyze pertinent studies of the presbyopia and ciliary muscles. The approach encompassed a thorough examination of available literature across different academic databases, such as PubMed, Embase, and Cochrane Library.

Results

Many studies have identified age-related thickening in the ciliary muscle and its potential causes, including the heightened deposition of connective tissues and traction exerted by the thickening lens. Notably, these inquiries culminated in the formulation of a geometric theory positing that the morphology of the ciliary muscle and its spatial relationship with adjacent structures exert pivotal influence over the tension exerted on zonular fibers.

Conclusion

The decline in the accommodative response of the muscle is prevalent in advanced age, with reduced mobility likely attributable to the increased stiffness of the Bruch's Membrane-Choroid Complex (BMCC), where the tendons of the ciliary muscle insert, as well as the thickening and stiffening of the lens. Importantly, the ciliary muscle forces do not change with age.

Lens height paraments comparison according to ciliary sulcus width (CSW): a pilot study of the predictive role of CLR and STSL for vault after ICL implantation

BACKGROUND

To assess the relationship between postoperative implantable collamer lens (ICL) vault and lens height obtained from two different measurements.

METHODS

A retrospective case series study enrolled eyes with horizontally implanted ICL. Crystal lens rise (CLR) and the distance between STS plane and anterior crystalline lens surface (STSL) were measured in the horizontal and vertical directions using ultrasound biomicroscopy (UBM). We compared the differences in the parameters measured in both horizontal and vertical directions. The participants were categorized into three groups according to ciliary sulcus width (CSW) which is defined as the distance between the posterior angle of the iris and the anterior angle of the ciliary process: narrow CSW group (NSG); medium CSW group (MSG); and wide CSW group (WSG). The correlations between CLR/STSL and vault were examined in each of the three groups. Biased correlation analysis was used further to contrast the correlation between CLR/STSL and vault.

RESULTS

This retrospective study included 223 myopic eyes. Vertical STSL (VSTSL) and vertical CLR (VCLR) exhibited significantly greater values compared to their horizontal counterparts (both P < 0.05). None of the indicators were statistically different between the three groups. In both NSG and MSG, STSL/CLR correlated with vault, while in WSG, only STSL correlated with vault (r=-0.316, P = 0.013). In contrast to HCLR, the correlation between HSTSL and vault remained after controlling for HCLR (r=-0.162, P = 0.015).

CONCLUSIONS

STSL should deserve more attention in the preoperative evaluation of ICL compared to CLR especially when CSW is large.

BCLA CLEAR presbyopia: Mechanism and optics

With over a billion adults worldwide currently affected, presbyopia remains a ubiquitous, global problem. Despite over a century of study, the precise mechanism of ocular accommodation and presbyopia progression remains a topic of debate. Accordingly, this narrative review outlines the lenticular and extralenticular components of accommodation together with the impact of age on the accommodative apparatus, neural control of accommodation, models of accommodation, the impact of presbyopia on retinal image quality, and both historic and contemporary theories of presbyopia.

Risk factors associated with haptic malposition in eyes implanted with implantable collamer lenses

PURPOSE

To examine the risk factors for haptic malposition in eyes with implantable collamer lens (ICL).

SETTING

Eye and ENT Hospital, Fudan University, Shanghai, China.

DESIGN

Prospective nonrandomized observational study.

METHODS

This study included 134 (77.9%) of 172 initially enrolled patients who underwent ICL implantation and completed a 1-year follow-up. The extent of haptics present in the ciliary sulcus (ICS) was measured. Patients were categorized based on ICS count (0 to 4). The position of the haptics was quantified as the distance between the iris root and the terminal tip of ICL haptics (iris root to haptic tip, IRH). The related factors to the ICS count and its correlation with the central vault were analyzed.

RESULTS

ICS distribution was 0 ICS in 19 eyes (14.2%), 1 in 22 eyes (16.4%), 2 in 32 eyes (23.9%), 3 in 29 eyes (21.6%), and 4 in 32 eyes (23.9%). Parameters like maximum ciliary body thickness (CBTmax, P = .008), iris-ciliary process distance (ICPD, P < .001), and ciliary process length ( P = .034) varied significantly across ICS groups. A multiple linear regression analysis revealed that the iris-ciliary angle ( P = .006), CBTmax ( P = .007), the distance between the sulcus-to-sulcus plane and the anterior crystalline lens surface (STSL, P = .035), and ICL size ( P = .015) were significantly associated with IRH. Spherical equivalents ( P = .042), STSL ( P = .001), and ICS count ( P = .020) significantly correlated with the central vault.

CONCLUSIONS

Shortened ciliary process is a primary risk for haptic malposition. The ICS count significantly relates to the central vault.

Descriptive Analysis of Footplate Position After Myopic Implantable Collamer Lens Implantation Using a Very High-Frequency Ultrasound Robotic Scanner

Purpose

To assess the position of the haptics of the implantable collamer lens (ICL) in myopic eyes using a high-frequency ultrasound robotic scanner.

Methods

This was a prospective, single-arm, observational study carried out at the Instituto Zaldivar SA (Mendoza, Argentina) in a sample of 52 eyes who have been submitted to successful ICL implantation prior to enrollment. Images of the eyes were obtained using a very-high frequency digital ultrasound robotic scanner (VHFDU) to establish the position of the ICL in the posterior chamber and its relation to the ciliary sulcus. New parameters for lens position analysis were also described.

Results

In 81% of cases (42 eyes), the ICL rests on the ciliary body (CB) in both temporal and nasal sides, being slightly lower than 6% (3 eyes) those that rest on the sulcus in both sides, with significant correlations between ICL position and vault values (p<0.05). Cases in which the ICL position was CB-CB yielded central vault values across the whole range determined within the sample, but most of the eyes where the ICL rests on both the sulcus in one side and the CB in the other yield greater central vault values. Correlation was significant between ICL position and retroposition distance on the temporal side (Spearman's rho -0.487, p<0.001). A significant but weaker correlation was also found between ICL position and retroiridian space (p<0.05).

Conclusion

ICL for myopia footplates tend to locate outside of the sulcus in a significant percentage of patients after successful implantation. VHFDU assessment in eyes implanted with an ICL to properly study the lens footplate position and posterior anatomical relations provides important additional information besides post-surgery vault.