Ocular Manifestations of Acute Secondary Angle Closure Associated With Lens Subluxation

Purpose:To evaluate the clinical characteristics and ocular features of patients with acute secondary angle closure, associated with lens subluxation (ASAC-LS).Methods:We performed a retrospective study at the EENT Hospital of Fudan University, Shanghai, China. A total of 41 affected eyes from 41 patients were enrolled in this study. Furthermore, 20 affected eyes were part of the ASAC-LS cohort and 21 affected eyes were included in the acute primary angle closure (APAC) cohort. The best-corrected visual acuity (BCVA), intraocular pressure (IOP), axial length (AL), minimum corneal curvature (K1), maximum corneal curvature (K2), and anterior chamber depth (ACD) were measured and compared between the 2 cohorts. In addition, inter-eye (intraindividual) comparison was performed.Results:The ASAC-LS cohort exhibited younger ages, more frequent trauma history (35%), lower IOP (27.43 ± 13.86 mmHg vs. 41.27 ± 10.36 mmHg), longer AL (23.96 ± 2.60 vs. 22.49 ± 0.77 mm), shallower ACD (1.28 ± 0.38 vs. 1.58 ± 0.23 mm), and bigger ACD differences (0.99 ± 0.52 vs. 0.15 ± 0.19 mm), as compared with the APAC cohort (all p < 0.05). Moreover, eyes from the lens subluxation cohort experienced worse BCVA, higher IOP, and shallower ACD than their matched unaffected eyes (all p < 0.05). Although longer AL, shallower ACD, and bigger ACD differences were strongly correlated with lens subluxation in a univariate logistic regression analysis, only the ACD difference remained significant in the multivariate model (p = 0.004, OR = 1,510.50). Additionally, according to the receiver operating characteristic (ROC) curve analysis, both ACD and ACD differences had greater value in the differential diagnosis of ASAC-LS and APAC, with a cut-off value of 1.4 and 0.63 mm, respectively.Conclusions:Shallower ACD and larger ACD differences provide the promising diagnostic potential for patients with ASAC-LS.

Frequently Experienced Problems in the Early Stages after Prescribing Rigid Gas Permeable Contact Lenses

Prescribing rigid gas-permeable (RGP) lenses involves a series of processes that determine the most appropriate final lens through the trial use of test lenses based on the results of slit lamp microscopy, measuring refraction and corneal curvature, and corneal topography. The final prescription is reached by judging the dynamic lens movement, adequacy of the tear layer around the lens, corrected vision, and quality of vision. Various problems are encountered soon after prescribing lenses, including foreign body sensation, tear hypersecretion, decreased visual acuity, blurring, visual acuity change, redness, dryness, sudden pain, lens centering, and lens fallout. Here, we examine these problems and how to solve them.

Association of Corneal Biomechanics Properties with Myopia in a Child and a Parent Cohort: Hong Kong Children Eye Study

Associations between corneal biomechanics, axial elongation and myopia are important but previous results are conflicting. Our population-based study aimed to investigate factors associated with corneal biomechanics, and their relationships with myopia in children and adults. Data from 3643 children and 1994 parents showed that children had smaller deformation amplitudes (DA) than parents (p < 0.001). A larger DA was significantly associated with elongated axial length (AL; children: ß = 0.011; adults: ß = 0.0013), higher corneal curvature (children: ß = 0.0086; adults: ß = 0.0096), older age (children: ß = 0.010; adults: ß = 0.0013), and lower intraocular pressure (IOP; children: ß = −0.029; adults: ß = −0.031) in both cohorts. The coefficient of age for DA in children was larger than in adults (p < 0.001), indicating that the DA change with age in children is faster than in adults. DA was significantly associated with spherical equivalent (p < 0.001) resulting from its correlation with AL and corneal curvature. In conclusion, the cornea is more deformable in adults than in children, whereas corneal deformation amplitude increases faster with age in children than that in adults, along with AL elongation. Longer AL, steeper corneal curvature, older age and smaller IOP correspond to a more deformable cornea. The association between corneal deformation amplitude and refraction was mediated via AL and corneal curvature.

Evaluation of the Relationships between Corneal Parameters, Ocular Biometry, and Myopia Magnitude

Axial length of the eye correlates with the magnitude of myopia. However, there are conflicting reports on the relationship between certain corneal parameters with myopia magnitude. The objective of this study was to compare ocular biometry and corneal parameters between emmetropic and myopic groups. Participants (n=127) were categorized as emmetropia (spherical equivalent, SE, ±0.50D), low myopia (-0.75D≤SE<-6.00D) and high myopia (SE≥-6.00D). The difference in axial length, anterior chamber depth, and vitreous chamber depth between emmetrope, low myope, and high myope were highly significant (one-way ANOVA, all p<0.001) with significant correlations between SE and all these parameters (simple regressions, all p<0.001). However, central corneal thickness, corneal radius of curvature, and corneal asphericity between these groups, and the correlations between the ocular parameters with SE were not significantly different (all p>0.05). Corneal curvature correlated significantly with axial length (p=0.001) but not with myopia magnitude (p=0.91). Rather than myopia magnitude, axial length appears to be more sensitive to detect changes in corneal curvature in myopes. In conclusion, myopic patients’ axial length should be carefully considered for interventions that involve the cornea, such as orthokeratology and refractive surgery.

The Biomechanical Response of the Cornea in Orthokeratology

Orthokeratology has been widely used to control myopia, but the mechanism is still unknown. To further investigate the underlying mechanism of corneal reshaping using orthokeratology lenses via the finite element method, numerical models with different corneal curvatures, corneal thicknesses, and myopia reduction degrees had been developed and validated to simulate the corneal response and quantify the changes in maximum stress in the central and peripheral corneal areas during orthokeratology. The influence of the factors on corneal response had been analyzed by using median quantile regression. A partial eta squared value in analysis of variance models was established to compare the effect size of these factors. The results showed central and peripheral corneal stress responses changed significantly with increased myopia reduction, corneal curvature, and corneal thickness. The target myopia reduction had the greatest effect on the central corneal stress value (partial eta square = 0.9382), followed by corneal curvature (partial eta square = 0.5650) and corneal thickness (partial eta square = 0.1975). The corneal curvature had the greatest effect on the peripheral corneal stress value (partial eta square = 0.5220), followed by myopia reduction (partial eta square = 0.2375) and corneal thickness (partial eta square = 0.1972). In summary, the biomechanical response of the cornea varies significantly with the change in corneal conditions and lens designs. Therefore, the orthokeratology lens design and the lens fitting process should be taken into consideration in clinical practice, especially for patients with high myopia and steep corneas.

Refractive lens power and lens thickness in children (6–16 years old)

To examine the refractive lens power (RLP) and lens thickness and their associated factors in children from North-Western China. Children from two schools (primary school and junior high school) in the North-Western Chinese province of Qinghai underwent a comprehensive ophthalmic examination including biometry and cycloplegic refractometry. The RLP was calculated using Bennett’s equation. The study included 596 (77.9%) individuals (mean age: 11.0 ± 2.8 years; range: 6–16 years) with a mean axial length of 23.65 ± 1.24 mm (range: 20.02–27.96 mm). Mean lens thickness was 3.30 ± 0.16 mm (range: 2.85–3.99 mm) and mean RLP was 24.85 ± 1.98D (range: 19.40–32.97). In univariate analysis, girls as compared to boys had a significantly thicker lens and greater RLP, shorter axial length, smaller corneal curvature radius and shorter corneal curvature radius (all P < 0.001). Both sexes did not differ significantly in refractive error (P = 0.11) and corneal thickness (P = 0.16). RLP was positively associated with refractive error (correlation coefficient r = 0.33; P < 0.001) and lens thickness (r = 0.62; P < 0.001) and negatively with axial length (r = − 0.70; P < 0.001). In univariate analysis, RLP decreased significantly with older age in the age group from age 6–13, while it plateaued thereafter, with no significant difference between boys and girls. In multivariate regression analysis, a higher RLP was associated with younger age (P < 0.001; standard regression coefficient β = − 0.07), female sex (P < 0.001; β = − 0.08), shorter axial length (P < 0.001; β = − 0.48) and higher lens thickness (P < 0.001; β = 0.42). In Chinese children, RLP with a mean of 24.85 ± 1.98D decreases with older age, male sex, longer axial length, and thinner lens thickness. Changes in RLP and axial length elongation are important players in the emmetropization and myopization.

Clinical Reliability of IOL Master 700 in Measurement of Pupil Diameter and Corneal Curvature

Purpose: To compare IOL Master 700 with autokeratometer and video pupillometer in measurement of pupil diameter and corneal curvature.Methods: Pupil diameter were measured with IOL Master 700 and video pupilometer, horizontal keratometry and vertical keratometry were measured with IOL Master 700 and autokeratometer in 100 eyes of 50 children. Paired t-test and Pearson's correlation analysis were used to compare the differences among the devices. Agreement between measurement was analyzed using Bland Altman plot and intraclass correlation coefficient.Results: Comparing IOL Master 700 and video pupilometer for pupil diameter, there was no significant difference (p > 0.05). There was also no significant difference between IOL Master 700 and autokeratometer in measurement of vertical keratometry (p > 0.05). However, regarding horizontal keratometry there was significant difference between IOL Master 700 and autokeratometer, horizontal keratometry measured with IOL Master 700 was steeper than with auto keratometer, +0.105 diopters (D) in right eye and +0.130 D in left eye (p < 0.05).Conclusions: There was good agreement between IOL Master 700 and comparator instruments in regards to pupil diameter and corneal curvature. IOL Master 700 can be helpful in uncooperative children for measuring pupil diameter and corneal curvature at the same time.