Factors influencing intraocular pressure, corneal thickness and corneal biomechanics after congenital cataract surgery

Drug delivery from a ring implant attached to intraocular lens: An in-silico investigation

Multiple iterations required to design ocular implants, which will last for the desired operational period of months or even years, necessitate the use of in-silico models for ocular drug delivery. In this study, we developed an in-silico model to simulate the flow of Aqueous Humor (AH) and drug delivery from an implant to the Trabecular Meshwork (TM). The implant, attached to the side of the intraocular lens (IOL), and the TM are treated as porous media, with their effects on AH flow accounted for using the Darcy equation. This model accurately predicts the physiological values of Intraocular Pressure (IOP) for both healthy individuals and glaucoma patients, as reported in the literature. Results reveal that the effective diffusivity of the drug within the implant is the critical parameter that can alter the bioavailability time period (BTP) from a few days to months. Intuitively, BTP should increase as effective diffusivity decreases. However, we discovered that with lower levels of initial drug loading, BTP declines when effective diffusivity falls below a specific threshold. Our findings further reveal that, while AH flow has a minimal effect on the drug release profile at the implant site, it significantly impacts drug availability at the TM.

Characterization of Limbus Biomechanical Properties Using Optical Coherence Elastography

The elasticity of the limbus is crucial for ocular health, yet it remains inadequately explored. This study employs acoustic radiation force optical coherence elastography (ARF-OCE) to evaluate the biomechanical properties of the limbus under varying intraocular pressures. The method was validated using a heterogeneous phantom and subsequently applied to ex vivo porcine limbus samples. Elastic wave velocity at specific locations within the limbus was calculated, and the corresponding Young's modulus values were obtained. Spatial elasticity distribution maps were generated by correlating Young's modulus values with their respective locations in the two-dimensional structural images. The results indicate that ARF-OCE enhances the understanding of limbus biomechanical behavior and holds potential for diagnosing regional variations caused by ocular diseases.

Incidence Rate of Secondary Glaucoma Following Congenital Cataract Surgery: An In-Depth Systematic Review and Meta-Analysis

PURPOSE

To assess the incidence of secondary glaucoma in children following congenital cataract surgery.

DESIGN

Systematic review and meta-analysis.

METHODS

The PubMed, Embase, Cochrane Library, and Web of Science databases were searched from inception through March 16, 2023. Studies reporting congenital cataract surgery and glaucoma were enrolled. The quality of the selected studies was assessed using the Newcastle Ottawa Scale, and data analysis was executed utilizing R software.

RESULTS

A total of 36 published studies with 3151 patients (4717 eyes) were included in the analysis. The incidence rate of glaucoma following congenital cataract surgery was 6.6% (95% CI: 3.9%, 9.9%). The incidence of secondary glaucoma in the primary intraocular lens (IOL) implantation group (3.3% [95% CI: 1.5%, 5.8%]) and the secondary IOL implantation group (3.5% [95% CI: 0%, 11.4%]) were lower compared to the aphakia group (13.5% [95% CI: 7.7%, 20.6%]). The incidence rate among children with congenital cataracts from Asia (6.9% [95% CI: 4.1%, 10.4%]) was higher than that in European children (0.9% [95% CI: 0%, 3.0%]; P < .01). A correlation was identified between the age at cataract surgery and the incidence of secondary glaucoma (P = .02).

CONCLUSIONS

This meta-analysis found that the incidence of secondary glaucoma following congenital cataract surgery is approximately 6.6%. Children with IOL implantation exhibit a lower incidence of secondary glaucoma, with a lower incidence noted in European children compared to their Asian counterparts. The age at cataract surgery is an important risk factor to consider.

The comparison of corneal densitometry in cases with glaucoma following childhood cataract surgery and juvenile glaucoma

PURPOSE

To compare the corneal densitometry (CD) in pediatric cases with glaucoma following childhood cataract surgery and juvenile open-angle glaucoma (JOAG).

METHODS

This prospective comparative study involved 13 eyes with JOAG, 12 eyes with pseudophakic glaucoma, 13 eyes with aphakic glaucoma, and 15 control subjects. Pentacam HR Scheimpflug corneal topography was employed to evaluate corneal thickness (CCT) and CD values.

RESULTS

The mean intraocular pressure (IOP) and CCT were significantly higher in aphakic glaucoma cases than the other groups (p = 0.001). In aphakic eyes, the mean CD values were higher in most of the anterior, center, and posterior layers of 0-2 mm, 2-6 mm, 6-10 mm, and total zones (p < 0.001 for all). In pseudophakic eyes, the mean CD values were statistically similar with that of aphakic eyes and higher than that of JOAG and control eyes in all layers of 0-2 mm zone and in anterior layer of 10-12 mm and anterior and total layers of 2-6 mm zones (p < 0.05 for all). The CD values demonstrated significant correlations with CCT values in both aphakic and pseudophakic eyes. However, a significant correlation of CD values with IOP was only demonstrated in aphakic eyes (p = 0.01 for all).

CONCLUSION

The probable effects of childhood cataract surgery especially aphakia might cause corneal backscatter of light and increased CD in all layers in all zones of the cornea. Increased CD values and its correlation with CCT and IOP in aphakic glaucoma eyes may be of importance in clinical management.

[Central corneal thickness in black children examined under general anesthesia at the Yalgado Ouédraogo University Medical Center]

INTRODUCTION

Central corneal thickness measurement permits an evaluation of physiological and pathological corneal changes. It allows for an intra-ocular pressure correction factor. Our purpose was to determine the mean central corneal thickness in children aged 0 to 72 months and to examine factors that might affect it.

PATIENTS AND METHODS

This was a cross-sectional hospital study which took place from February to December 2019 in the ophthalmology service of YO University Medical Center. It included healthy eyes of children 0-72 months of age examined under general anesthesia. Ultrasonic pachymetry was used to measure the central corneal thickness. The studied variables were age, sex, CCT, corneal diameter, intraocular pressure, and cup/disc ratio.

RESULTS

One hundred and twenty-seven healthy eyes of 78 children 0-72 months of age were included. The mean age was 22 months. The overall mean CCT was 554.01±34.21μm. It was 556.58μm for children from 0 to 36 months of age and 536.12μm for subjects over 36 months. The mean CCT was 555.96±32.96μm in boys and 551.80±36.16μm in girls. In patients who underwent bilateral CCT measurement, the mean CCT was 554.74±35.67μm in the right eye and 549.76±24.08μm in the left eye. Lower IOP's were found in patients with thicker corneas (p=0.00).

CONCLUSION

The CCT values for black children over 36 months of age was similar to the CCT in black adults.

Postoperative Changes in Central Corneal Thickness and Intraocular Pressure in a Prospective Cohort of Congenital Cataract Patients

PURPOSE

To evaluate changes in central corneal thickness (CCT) and intraocular pressure (IOP) in children after surgery for congenital cataracts and to investigate the association between CCT and IOP.

METHODS

For this prospective observational cohort study, we recruited patients undergoing surgery for unilateral or bilateral congenital cataracts. CCT and IOP were measured before surgery and 1, 3, 6, 12, and 24 months after surgery.

RESULTS

Seventy-six children (152 eyes) were enrolled; 33 eyes were unaffected by cataracts, 77 were aphakic, and 42 were pseudophakic. In aphakic eyes, mean CCT increased by 31.14 ± 44.32 μm at 12 months postoperation and 33.09 ± 35.42 μm at 24 months postoperation; this increase was significantly higher than that in pseudophakic eyes 12 months after surgery (8.36 ± 19.91 μm; P < 0.001) and 24 months after surgery (0.31 ± 14.19 μm; P = 0.024). However, no significant differences in IOP were found between the different phakic states at 12 and 24 months postoperation (P = 0.672 and P = 0.080, respectively). There were also no significant differences in CCT and IOP before and after surgery in the unaffected eyes.

CONCLUSIONS

Mean CCT peaked at 12 months, and the mean IOP remained normal in both the aphakic and pseudophakic eyes during this study. CCT and IOP were positively correlated, regardless of the phakic status or age, a relationship which suggests that both parameters should be monitored closely in postsurgical patients for up to 12 months and in this time, may impact the ability to diagnose glaucoma.

A comparison of Icare PRO and Perkins tonometers in anesthetized children

AIM

To compare intraocular pressure (IOP) measurements obtained with the Perkins applanation tonometer and Icare PRO (ICP) rebound tonometer in anesthetized aphakic or strabismus children. Furthermore, intra-operator correlation and inter-operator correlation have been evaluated, along with the effects of central corneal thickness (CCT) on IOP measurements.

METHODS

Seventy children undergoing examination under anesthesia with sevoflurane for aphakic patients and for surgery for strabismus were included. IOP have been measured twice immediately after anesthesia induction with both Perkins applanation tonometer (PAT) and ICP in one eye and by two different operators with both devices in the fellow eye. Furthermore, CCT was measured with ultrasound pachymetry Pacline (Optikon). Agreement between the device measurements has been evaluated using Bland-Altman analyses. Repeatability and reproducibility of the device have been evaluated with intraclass correlation coefficient (ICC) with a value > 0.75 associated with excellent reliability. The relationship between IOP and CCT has been evaluated with Spearman's correlation coefficient r and determination coefficient r².

RESULTS

Mean difference in IOP measurements between ICP and PAT was 1.97 mmHg ± 1.23 mmHg (p < 0.05). This difference appeared to be higher in aphakic patients (mean difference 2.15 ± 1.35) than in patients undergoing strabismus surgery (mean difference 1.83 mmHg ± 1.12). Intraclass correlation coefficient (ICC) is used to evaluate repeatability and reproducibility, which are both high for PAT (repeatability 0.96, reproducibility 0.76) compared with ICP (repeatability 0.81, reproducibility 0.70). Correlation coefficient between CCT and IOP is 0.66 for both ICP and PAT.

CONCLUSION

ICP tends to overestimate IOP compared to PAT. Repeatability and reproducibility are both high for PAT as compared to ICP. A significant correlation between IOP and CCT for both instruments has been demonstrated.

Influence of corneal diameter on surgically induced astigmatism in small-incision cataract surgery

OBJECTIVE

Clear corneal incisions (CCI) in cataract surgery create a variable amount of surgically induced astigmatism (SIA). As refractive outcomes become increasingly important, it is necessary to understand factors that impact SIA and refractive surprises. In this study, we evaluate the effect of horizontal corneal diameter (white-to-white, WTW) on SIA in 2.2 mm small-incision cataract surgery.

DESIGN

Prospective study at an academic-university-based outpatient clinic (Duke Eye Center).

PARTICIPANTS

We enrolled adults ≥18 years of age without prior corneal surgery or corneal pathology undergoing cataract surgery with a single surgeon (R.R.V.).

METHODS

All surgeries were uncomplicated and performed through a manually constructed, limbal, temporal, or superotemporal 2.2 mm CCI. Enrolled participants received standard-of-care evaluations and postoperative management. SIA was calculated at the first postoperative month using the Jaffe and Clayman vector analysis equation.

RESULTS

We enrolled 43 subjects (55 eyes) with a mean age of 71 years with WTW corneal diameter values ranging from 11.34 to 12.99 mm obtained from Lenstar^® (Haag-Streit Group, Koeniz, Switzerland). Postoperative SIA ranged from 0.072 to 1.6 D (mean 0.47 D, standard deviation 0.33 D). SIA was plotted against WTW and best fit to a linear regression model with a slope of -0.056 and an R² value of 0.006.

CONCLUSIONS

In this prospective study, WTW diameter had minimal effects on the SIA in uncomplicated small-incisional cataract surgery through a 2.2 mm temporal or superotemporal CCI with a single surgeon. Our findings suggest that corneal diameter does not play a clinically significant role in this population undergoing small-incisional cataract surgery.

Goldmann applanation tonometer versus ocular response analyzer for measuring intraocular pressure after congenital cataract surgery

PURPOSE

To compare intraocular pressure measured using the Goldmann applanation tonometer with that measured using the ocular response analyzer after congenital cataract surgery.

METHODS

This study included 113 eyes of 64 patients who underwent lensectomy and vitrectomy. In all, 36 eyes remained aphakic after surgery. Intraocular lens implantation was performed at the time of surgery in 47 eyes and secondarily in 30 eyes. Corneal hysteresis, corneal resistance factor, and cornea-compensated intraocular pressure were measured. The influences of independent factors on the difference between the cornea-compensated intraocular pressure and intraocular pressure measured with Goldmann applanation tonometer were investigated using linear regression analyses. Agreement between the two tonometers was investigated using the Bland and Altman and 95% limits of agreement analysis.

RESULTS

Central corneal thickness, corneal hysteresis, and corneal resistance factor were 591.2 ± 53.3 µm, 10.83 ± 2.27 mmHg, and 11.36 ± 2.14 mmHg, respectively. Cornea-compensated intraocular pressure (16.75 ± 4.82 mmHg) was significantly higher than intraocular pressure measured with Goldmann applanation tonometer (14.41 ± 2.27 mmHg, p < 0.001). Central corneal thickness (p = 0.02) and corneal hysteresis (p < 0.001) were identified as the main predictors of difference between cornea-compensated intraocular pressure and intraocular pressure measured with Goldmann applanation tonometer readings. A 95% limits of agreement for cornea-compensated intraocular pressure and intraocular pressure measured with Goldmann applanation tonometer was between -4.86 and 9.53 mmHg in the entire group. Cornea-compensated intraocular pressure showed the best agreement with intraocular pressure measured with Goldmann applanation tonometer in the primary pseudophakic subgroup as compared to the other subgroups.

CONCLUSION

The Goldmann applanation tonometer and ocular response analyzer cannot be used interchangeably for measuring intraocular pressure after congenital cataract surgery. The difference between the cornea-compensated intraocular pressure and intraocular pressure measured with Goldmann applanation tonometer was primarily affected by central corneal thickness and corneal hysteresis. Among the subgroups, the primary pseudophakic subgroup had the thinnest cornea and the highest corneal hysteresis values and demonstrated the best agreement between the two tonometers.