Static and dynamic pupil characteristics in pseudoexfoliation syndrome and glaucoma

Iris Crypts Could Reduce the Chance of Angle Closure: A Computational Biomechanics Study Derived From Clinical and Human Iris Data

Purpose

To investigate the effect of crypts during pupil constriction and dilation on the potential for angle closure by performing finite element analysis using clinical and experimental data on human tissues.

Methods

A computational model was developed to determine the influence of small crypts (surface area of ∼0.015 mm2) and large crypts (surface area of 0.300 mm2) on the anterior chamber angles during pupil dilation. The model needed permeability data from human subjects; hence, 21 enucleated human eyes (72 hours postmortem) were procured and subjected to a flow setup previously reported. Finally, 66 subjects were recruited to measure pupil constriction and dilation levels from optical coherence tomography (OCT) videos.

Results

The hydraulic permeability of the human iris stroma was determined to be 2.55 ± 1.93 × 10-5 mm2/Pa · s. The average iris constriction and dilation durations were 0.710 ± 0.213 seconds and 1.24 ± 0.401 seconds, respectively, with pupil diameter changes of 1.16 ± 0.39 mm and 0.75 ± 0.27 mm, respectively. The computational models had starting anterior chamber angles of 51.30° and final anterior chamber angles of 26.81° once steady state had been reached. In an extreme case with decreased anterior border layer (ABL) permeability, the anterior chamber angle narrowed to 12.37°, but the presence of crypts kept the angle above 20.36°, highlighting the potential of crypts in preventing angle closure.

Conclusions

Our findings on the biomechanics of crypts in the iris may drive the development of novel treatments by altering ABL morphology, providing an alternative bypass for angle closure prevention in high-risk patients.

Mydriasis Stability During Cataract Surgery in Patients with Systemic Comorbidities Using a Standardised Combination of Intracameral Mydriatics and Anaesthetic

BACKGROUND

This study aimed to evaluate mydriasis stability during cataract surgery in patients with systemic comorbidities such as diabetes mellitus (DM) and pseudoexfoliation syndrome (PXF) after a standardised combination of intracameral mydriatics and anaesthetic (SCIMA). Stable mydriasis is crucial for safe and effective phacoemulsification.

METHODS

Patients were included if they achieved pupil dilation ≥6.0 mm during the qualifying visit. A total of 103 patients were enrolled, divided into three groups: cataract with diabetes (C + DM group, n = 35), cataract with PXF (C + PXF group, n = 32), and cataract without those comorbidities (C group, n = 36). SCIMA was administered, and pupil diameters were measured at key surgical stages. Stability was defined as a pupil diameter of ≥6.0 mm without additional pharmacological intervention and no significant change in its diameter (≥3.0 mm).

RESULTS

Stable mydriasis was achieved in 90.3% of patients: 97.1% in the C + DM group, 90.6% in the C + PXF group, and 83.3% in the C group, with no statistically significant differences (p = 0.14).

CONCLUSIONS

SCIMA effectively maintains mydriasis stability during cataract surgery, even in patients with systemic comorbidities, ensuring greater surgical safety.

Effectiveness of a Standardized Combination of Intracameral Mydriatics and Anaesthetic on Mydriasis during Cataract Surgery with Coexisting Diseases

PURPOSE

To examine the effectiveness of a standardized combination of intracameral mydriatics and anesthetic (SCIMA) on mydriasis in patients with coexisting diseases such as diabetes mellitus (DM) and pseudoexfoliation syndrome (PXF) during phacoemulsification.

METHODS

Patients with cataract were included in the study if they achieved pupil dilation diameter ≥ 6.0 mm after the administration of mydriatic eyedrops (ME) during the first visit (V1). During the second visit (V2), pupil size measurements were obtained for phacoemulsification surgery with SCIMA. Effective mydriasis was defined as a pupil diameter ≥ 6.0 mm just prior to capsulorhexis without the use of additional pupil dilating agents. The measurements after ME administration during V1 and after SCIMA use during V2 were compared.

RESULTS

103 patients (103 eyes) were divided into 3 groups: cataract and DM (n = 35), cataract and PXF (n = 32), and cataract without DM or PXF (n = 36). SCIMA administration allowed the achievement of effective mydriasis (≥6.0 mm) in all groups (n = 103; 100%). Mydriasis was significantly larger (p ≤ 0.001) after ME (7.3 mm) than after SCIMA (6.8 mm) administration.

CONCLUSIONS

Patients with cataract and such comorbidities as DM or PXF are likely to achieve effective pharmacological mydriasis during cataract phacoemulsification after SCIMA application. Mydriasis after ME is slower and larger, while SCIMA is faster.

Influence of Pilocarpine Eyedrops on the Ocular Biometric Parameters and Intraocular Lens Power Calculation

Objective

To evaluate the influence of pilocarpine eyedrops on the ocular biometric parameters and whether these parameter changes affect the intraocular lens (IOL) power calculation in patients with primary angle-closure glaucoma (PACG).

Methods

Twenty-two PACG patients and fifteen normal subjects were enrolled. Ocular biometric parameters including the axial length (AL), anterior chamber depth (ACD), lens thickness (LT), mean keratometry (Km), and white-to-white distance (WTW) were measured by using a Lenstar LS 900 device before and at least 30 minutes after instillation of 2% pilocarpine eyedrops. Lens position (LP) was calculated, and the IOL power prediction based on the ocular biometric parameters was performed using the Barrett Universal II, Haigis, Hoffer Q, Holladay I, or SRK/T formulas before and after pilocarpine application.

Results

In both PACG and normal groups, pilocarpine eyedrops induced a slight but statistically significant increase in the mean AL (0.01 mm for both groups) and mean LT (0.02 mm and 0.03 mm, respectively) but a significant decrease in the mean ACD (0.03 mm and 0.05 mm, respectively) and mean LP (0.02 mm and 0.04 mm, respectively). No significant changes in the mean Km and WTW were noticed in both groups. In addition, the IOL power calculation revealed insignificant changes before and after the pilocarpine instillation in both groups, regardless of the formula used.

Conclusions

Pilocarpine eyedrops can induce slight changes in the ocular biometric parameters including the AL, ACD, LT, and LP. However, these parameter changes will not result in a significant difference in IOL power estimation.

How are pupillary parameters affected in pseudoexfoliation syndrome? A quantitative study

PURPOSE

We evaluated the effects of pseudoexfoliation syndrome on dynamic, static pupillary parameters (scotopic, mesopic, photopic) and the pupil dilation speed, with automatic pupillometry.

MATERIAL AND METHODS

The study group included 140 eyes with clinically visible pseudoexfoliation material (PXM) of 110 patients. The study group was compared with the control group formed by including 140 eyes of 110 patients. Scotopic measurements at 0.4 lx illumination, mesopic measurements at 4 lx illumination, and photopic measurements at 40 lx illumination were performed. Dynamic measurements were made at 500 lx illumination. The mean pupil dilation speed at 10th second was calculated. In addition, the eyes (80 patients) with clinically unilateral PXM were compared with the other eyes of the patients.

RESULTS

The mean scotopic, mesopic, photopic and dynamic pupil diameters of eyes with clinical PXM were compared with the control group, all values were found to be significantly lower in eyes with PXM. (p < 0.0001, p < 0.0001, p < 0.0001, p < 0.0001, respectively). The mean speed of pupil dilation at the 10th second was also significantly lower in the pseudoexfoliation syndrome group (p < 0.0001). The measurement results of the patients with clinical PXM were significantly lower than the other unaffected eyes (p = 0.001, p = 0.004, p = 0.048, p = 0.035, respectively). The mean speed of pupil dilation at 10th second was also significantly lower in eyes with PXM (p = 0.009).

CONCLUSION

Results clearly reveal that pseudoexfoliation syndrome affects iris mechanisms. Although pseudoexfoliation syndrome is a systemic syndrome, we can say that the emergence of iris dysfunction findings is parallel with the clinical observation of PXM.

A transcriptome atlas of the mouse iris at single-cell resolution defines cell types and the genomic response to pupil dilation

The iris controls the level of retinal illumination by controlling pupil diameter. It is a site of diverse ophthalmologic diseases and it is a potential source of cells for ocular auto-transplantation. The present study provides foundational data on the mouse iris based on single nucleus RNA sequencing. More specifically, this work has (1) defined all of the major cell types in the mouse iris and ciliary body, (2) led to the discovery of two types of iris stromal cells and two types of iris sphincter cells, (3) revealed the differences in cell type-specific transcriptomes in the resting vs. dilated states, and (4) identified and validated antibody and in situ hybridization probes that can be used to visualize the major iris cell types. By immunostaining for specific iris cell types, we have observed and quantified distortions in nuclear morphology associated with iris dilation and clarified the neural crest contribution to the iris by showing that Wnt1-Cre-expressing progenitors contribute to nearly all iris cell types, whereas Sox10-Cre-expressing progenitors contribute only to stromal cells. This work should be useful as a point of reference for investigations of iris development, disease, and pharmacology, for the isolation and propagation of defined iris cell types, and for iris cell engineering and transplantation.

Dynamic volume-rendered optical coherence tomography pupillometry

PURPOSE

To assess intrapupillary space (IPS) changes in healthy subjects with regard to decreased iris motility in patients with pseudoexfoliation glaucoma (PEXG) or non-arteritic anterior ischaemic optic neuropathy (NAION) in a feasibility study in a clinical environment.

METHODS

Scotopic and photopic IPS measurements using three-dimensionally rendered swept-source optical coherence tomography (SS-OCT) data were obtained and compared for all subjects. Intrapupillary space (IPS) parameters were evaluated such as absolute volumetric differences, relative light response for volumetric ratios and pupillary ejection fraction (PEF) for functional contraction measurements.

RESULTS

From a total of 122 IPS from 66 subjects, 106 IPS were eligible for comparison providing values for 72 normal, 30 PEXG and 4 NAION eyes. In healthy, PEXG and NAION subjects, scotopic overall mean IPS was 8.90, 3.45 and 4.16 mm³ , and photopic overall mean IPS was 0.87, 0.74 and 1.13 mm³ , respectively. Three-dimensional contractility showed a mean absolute difference of 8.03 mm³ for normals (defined as 100% contractility), 2.72 mm³ for PEXG (33.88% of normal) and 3.03 mm³ for NAION (38.50% of normal) with a relative light response ratio between scotopic and photopic volumes of 10.26 (100%), 4.69 (45.70%) and 3.67 (35.78%), respectively. Pupillary ejection fraction (PEF) showed a contractile pupillary emptying of 88.11% for normals, 76.92% for PEXG and 70.91% for NAION patients.

CONCLUSION

This 3D pupillometry OCT assessment allows for quantitative measurements of pupil function, contractility and response to light. More specifically, PEF is presented as a potential (neuro)-pupillary outcome measure that could be useful in the monitoring of ophthalmic disorders that affect pupillary function.

Ophthalmic Viscosurgical Devices (OVDs) in Challenging Cases: a Review

Ophthalmic viscoelastic devices (OVDs) are currently used in cataract surgery and have significantly improved the safety and effectiveness of this surgical procedure. OVDs are classified according to the zero-shear viscosity and the cohesion-dispersion index in cohesive, dispersive, and viscoadaptives. OVDs create and maintain anterior chamber depth and visibility, protecting the corneal endothelium and other intraocular tissues during surgery. The selection of the most adequate OVD is especially relevant when performing cataract surgery in challenging cases, such as in hard, mature cataracts, flat anterior chamber, pseudoexfoliation syndrome, intraoperative floppy iris syndrome, or glaucoma surgery. In such cases, OVD is crucial for facilitating the surgical procedure and the associated minimal complication rate. The use of a combination of OVDs (soft-shell technique and modifications), the use of blue-colored OVDs, and the combination of sodium hyaluronate with lidocaine have also been described as useful tools in some of these challenging cases.