Cortical Cataract and Refractive Error

Time trends and heterogeneity in the disease burden of visual impairment due to cataract, 1990–2019: A global analysis

Objectives

This study aimed to estimate the disease burden of cataract and evaluate the contributions of risk factors to cataract-associated disability-adjusted life years (DALYs).

Materials and methods

Prevalence and DALYs of visual impairment due to cataract were extracted from the Global Burden of Disease (GBD) study 2019 to explore time trends and annual changes. Regional and country-level socioeconomic indexes were obtained from open databases. The time trend of prevalence and DALYs was demonstrated. Stepwise multiple linear regression was used to evaluate associations between the age-standardized rate of DALYs of cataract and potential predictors.

Results

Global Prevalence rate of visual impairment due to cataract rose by 58.45% to 1,253.9 per 100,000 population (95% CI: 1,103.3 to 1,417.7 per 100,000 population) in 2019 and the DALYs rate rose by 32.18% from 65.3 per 100,000 population (95% CI: 46.4 to 88.2 per 100,000 population) in 1990 to 86.3 per 100,000 population (95% CI: 61.5 to 116.4 per 100,000 population) in 2019. Stepwise multiple linear regression model showed that higher refractive error prevalence (β = 0.036, 95% CI: 0.022, 0.050, P < 0.001), lower number of physicians per 10,000 population (β = −0.959, 95% CI: −1.685, −0.233, P = 0.010), and lower level of HDI (β = −134.93, 95% CI: −209.84, −60.02, P = 0.001) were associated with a higher disease burden of cataract.

Conclusion

Substantial increases in the prevalence of visual impairment and DALYs of cataract were observed from 1990 to 2019. Successful global initiatives targeting improving cataract surgical rate and quality, especially in regions with lower socioeconomic status, is a prerequisite to combating this growing burden of cataract in the aging society.

Prevalence and Risk Factors for Adult Cataract in the Jingan District of Shanghai

Purpose. We report the prevalence of age-related cataract (ARC) in the Jingan district of Shanghai and analyze the risk factors for ARC to be better prepared for the increasing burden of cataracts as a significant cause of visual impairment worldwide. Methods. From March to June 2010, a population-based, cross-sectional study was conducted in a community selected by stratified cluster sampling in the Jingan district of Shanghai. Residents aged 40 and older were recruited and investigated by questionnaires and ophthalmic examination. Univariate and multivariate logistic regression models were used to evaluate the association of these risk factors with any cataract. Results. A total of 2894 subjects aged 40 years and above were included in our study. Nine hundred forty-eight people (32.8%) were diagnosed with cataract, including 845 with bilateral cataracts (29.2%) and 292 with moderate and severe visual impairment (low vision, 10.1%). There were significant differences in low vision among different age groups and gender (Χ2age = 84.420, $P$ age < 0.001, Χ2gender = 7.696, $P$ gender = 0.021). For any cataract, we found age (OR = 1.107, 95% CI: 1.094–1.120) and refractive error (OR = 1.352, 95% CI: 1.127–1.622) were independent risk factors. Conclusion. The prevalence of cataract is estimated to be nearly one-third of the sample, increasing with age. We provided further evidence that age and refractive error are independent cataract risk factors.

The impact of cataract progression on accuracy of intraocular lens power measurement

Purpose

The aim of this study was to assess the impact of cataract progression using the Haigis formula-calculated intraocular lens (IOL) power and investigate the accuracy of IOL power measured at different time points.

Methods

This prospective study was performed on 75 eyes of 75 patients who underwent uneventful cataract surgery. Preoperative ocular parameters including axial length (AL), keratometry (K), anterior chamber depth (ACD), corneal astigmatism, corrected distance visual acuity (CDVA) and uncorrected distance visual acuity (UDVA) examined at the two time points, more than 3 months preoperatively and preoperative 1 day were compared. The ocular parameters measured in the two time points were used to calculate the predicted implanted IOL power and the actual IOL power was chosen on the basis of parameters measured earlier before surgery using the Haigis formula. The mean numerical error (MNE) and mean absolute error (MAE) predicted by the two time points were also compared.

Results

There were significant differences in the ACD, IOL power, UDVA and CDVA (P<0.01), but no statistical differences in AL, mean K and corneal astigmatism (P>0.05) during the average of 5.6 months before surgery. No statistically significant difference was detected in MNE (P>0.05), while the MAE had a significant difference in the two time points (P<0.05).

Conclusion

The IOL power measured earlier before surgery might result in a higher accuracy and the postoperative refractive outcome tended towards emmetropia.

Deformations and Ruptures in Human Lenses With Cortical Cataract Subjected to Ex Vivo Simulated Accommodation

Purpose

Human cortical opacities are most commonly accompanied by changes in lens fiber structure in the equatorial region at the lens nucleus–cortex interface. Cortex and nucleus have different elastic properties, which change with age. We therefore subjected ex vivo lenses to simulated accommodation and studied the internal deformations to better understand the mechanism of cortical cataract formation.

Methods

Nine human donor lenses (33–88 years old) were tested using a bespoke radial stretching device for anterior eye segments. Seven of the lenses exhibited cortical cataracts. The other two lenses, without cataract, were used as controls. Frontal and cross-sectional images of the lens obtained during stretching facilitated measurements on equatorial lens diameter and central lens thickness in the stretched and unstretched states.

Results

Stretching caused the lens equatorial diameter to increase in all cases. Conversely, the lens central thickness showed no systematic variation during stretching. For four of the lenses with cortical cataract, ruptures were observed during stretching at the nucleus–cortex boundary adjacent to the cortical cataracts. Ruptures were not observed in the control lenses or in the three other lenses with cortical cataract.

Conclusions

Internal ruptures can occur in aged ex vivo lenses subjected to simulated disaccommodation. These ruptures occur at the nucleus–cortex interface; at this location, a significant stiffness discontinuity is expected to develop with age. It is hypothesized that ruptures occur in in vivo lenses during accommodation—or attempted accommodation.

Repeatability and reproducibility of manifest refraction

PURPOSE

To evaluate the intraexaminer repeatability and the interobserver reproducibility of manifest refraction.

SETTING

Tertiary referral center.

DESIGN

Retrospective study.

METHODS

Patients attending at least 2 preoperative refractions before undergoing subsequent refractive surgery were included. All manifest refractions were performed by 1 of 4 experienced optometrists using an automated phoropter according to a standard protocol. The first manifest refraction was performed after obtaining automated refraction and measuring the spectacles of the patient. The second refraction was typically refined from the first also considering wavefront refraction and tomography/topography.

RESULTS

The latest 2 manifest refractions of 1000 eyes obtained at 2 separate visits showed a mean pairwise absolute difference of 0.16 ± 0.19 diopter (D) (range 0 to 1.38 D) in spherical equivalent (SE). This SD was better than 0.25 D (the minimum measurement increment of refraction itself). The 95% limit of agreement (LoA) was within 0.50 D for sphere, cylinder, and SE. The SD of the astigmatism axis was approximately 10 degrees, and the 95% LoA was within 22 degrees (the difference in axis decreasing significantly with the measured cylinder magnitude). The SD for corrected distance visual acuity (CDVA) was half a Snellen line and the 95% LoA was within 1.5 lines (with increasing deviation with worse vision). There were no clinically meaningful differences in reproducibility (2 optometrists) compared with repeatability (same optometrist) in sphere, axis, and CDVA.

CONCLUSIONS

Reproducibility was 0.16 D irrespective whether refractions were performed by 1 or 2 different optometrists. Obtaining multiple refractions preoperatively might increase the predictability of surgery and decrease the enhancement rate.

Panoramic Observation of Crystalline Lenses with 25 MHz Ultrasonography

Purpose

To visualize and assess in vivo the age-related changes in crystalline lens size and contour.

Methods

Seventy-nine healthy volunteers, 39 females and 40 males, with a mean age of 41.53 + 11.32 years (range: 21 to 60 years) were enrolled in this study. The axial lens thickness (ALT), equatorial lens diameter (ELD), and anterior (R_a) and posterior (R_p) lens surface radii of curvatures of the subjects' left eyes were measured with a 25 MHz ultrasound probe.

Results

The mean ALT and ELD were 4.178 mm + 0.288 mm and 9.209 mm + 0.214 mm, respectively. There was a statistically significant increase in both ALT (slope = 11 μm/year, r = 0.88, p < 0.01) and ELD (slope = 6 μm/year, r = 0.60, p < 0.01) with age. R_a negatively correlated, and R_p did not change with age.

Conclusion

There were no statistically significant relationships between any studied values and gender. Independent of gender, the lens grows equatorially and axially with age while its central anterior lens surface steepens and its posterior central surface curvature does not change.