Glaucoma Diagnostic Performance of Macular Ganglion Cell Complex Thickness Using Regular and Long Axial Length Normative Databases

The risks of misdiagnosing a healthy individual as glaucomatous or vice versa may be high in a population with a large majority of highly myopic individuals, due to considerable morphologic variability in high myopic fundus. This study aims to compare the diagnostic ability of the regular and long axial length databases in the RS-3000 Advance SD-OCT (Nidek) device to correctly diagnose glaucoma with high myopia. Patients with high myopia (axial length ≥ 26.0 mm) in Chang Gung Memorial Hospital, Taiwan between 2015 and 2020 were included. Glaucoma was diagnosed based on glaucomatous discs, visual field defects and corresponding retinal nerve fiber layer defects. The sensitivity, specificity, diagnostic accuracy and likelihood ratios of diagnosing glaucoma via mGCC thickness in both superior/inferior and GChart mapping using the regular and long axial length normative databases. The specificity and diagnostic accuracy of mGCC thickness for distinguishing glaucomatous eyes from nonglaucomatous eyes among highly myopic eyes were significantly improved using the long axial length database (p=0.046). There were also significant proportion changes in S/I mapping as well as GChart mapping (37.3% and 48.0%, respectively; p<0.01) from abnormal to normal in the myopic normal eye group when using the long axial length normative database. The study revealed that clinicians could utilize a long axial length database to effectively decrease the number of false-positive diagnoses or to correctly identify highly myopic normal eyes misdiagnosed as glaucomatous eyes.

Axial length growth difference between eyes after monocular laser refractive surgery: eight patients who underwent myopic laser ablation for both eyes at intervals of several years

Background Myopia is a global public health issue. Controlling myopia progression is a primary focus of myopia studies today. Peripheral retinal myopic defocus is considered the mechanism for reduced myopia progression in orthokeratology studies. The topographic change in the front corneal surface after laser refractive surgery and orthokeratology procedures may appear similar. The purpose of this study was to explore the role of myopic laser ablation on axial length (AL) growth. Methods Myopic patients who underwent monocular excimer laser refractive surgery first in one eye and then in another eye several years later because of myopia occurrence or myopia progression were recruited. The axial length elongation and refraction (spherical equivalent) between the two eyes were observed and compared. Results A total of 8 myopic patients were enrolled in the study. The AL increased from 24.52 ± 0.96 mm to 24.68 ± 1.03 mm but without significance (T = 1.49, P > 0.05) in the ablated eyes. The AL increased significantly from 23.73 ± 0.91 mm to 24.26 ± 0.95 mm in the nonablated eyes (T = 6.76, P < 0.001). The AL elongation of the ablated eyes with 0.16 ± 0.30 mm growth was significantly lower than that of the nonablated eyes with 0.53 ± 0.32 mm growth (T = 8.98, P < 0.001). The spherical equivalent (SE) increased significantly in the ablated eyes (− 0.59 ± 0.21 (D), T = 6.36, P < 0.001) and in the nonablated eyes (− 0.97 ± 0.55 (D), T = 4.91, P < 0.01), and the difference between the two eyes was significant (T = 3.05, P < 0.05). Conclusions The inhibitory effect of myopic laser ablation on AL elongation reported in the limited case studies argues for animal research on its efficacy as a new intervention for myopia progression.

Development and Verification of an Adjustment Factor for Determining the Axial Length Using Optical Biometry in Silicone Oil-Filled Eyes

The aim of this prospective clinical study was to establish and verify an adaptation for axial length (AL) measurement in silicone oil (SO)-filled pseudophakic eyes with a Scheimpflug and partial coherence interferometry (PCI)-based biometer. The AL was measured with a Pentacam AXL (OCULUS Optikgeräte GmbH, Wetzler, Germany) and IOLMaster 700 (Carl Zeiss Meditec, Jena, Germany). The coefficients of variation (CoV) and the mean systematic difference (95% confidence interval (CI)) between the devices were calculated. After implementing a setting for measuring AL in tamponaded eyes with a Pentacam based on data of 29 eyes, another 12 eyes were examined for verification. The mean AL obtained with the Pentacam was 25.53 ± 1.94 mm (range: 21.70 to 30.76 mm), and with IOLMaster, 24.73 ± 1.97 mm (ranged 20.84 to 29.92 mm), resulting in a mean offset of 0.80 ± 0.08 mm (95% CI: 0.77, 0.83 mm), p < 0.001. The AL values of both devices showed a strong linear correlation (r = 0.999). Verification data confirmed good agreement, with a statistically and clinically non-significant mean difference of 0.02 ± 0.04 (95% CI: −0.01, 0.05) mm, p = 0.134. We implemented a specific adaptation for obtaining reliable AL values in SO-filled eyes with the Pentacam AXL.

Assessment of factors affecting flicker ERGs recorded with RETeval from data obtained from health checkup screening

The purpose of this study was to determine the ocular, sex- and age-specific, anthropometric, and hematologic factors that affect the implicit times and amplitudes of the flicker ERGs recorded with the RETeval system from individuals 40- to 89-years-of-age. Flicker ERGs were recorded with the RETeval system from 330 individuals who had normal fundus and OCT images. Univariate and multivariate regression analyses were performed to identify factors associated with the implicit times and amplitudes of the RETeval flicker ERGs. Univariate regression analyses showed significant correlations between the implicit times and the BCVA, age, axial length, blood sugar level, and BUN in both eyes. Multivariate regression analyses identified age and axial length as two independent factors that were significantly correlated with the implicit times of the RETeval flicker ERGs. Univariate regression analyses also showed significant correlations between the amplitudes and age, platelet count, HDL level, and creatinine level in both eyes. However, smoking habits, body mass index, and blood pressure were not correlated with the RETeval flicker ERGs. We conclude that age and some ophthalmologic and hematologic findings except for anthropometric findings were suggested to significantly affect the measurements of the RETeval flicker ERGs.

Evaluation of the B/F Ratio Distribution of Cataract Patients Without Corneal Abnormalities and Its Effect on Ocular Parameters

Purpose: To evaluate the distribution of the posterior-anterior corneal radius ratio (B/F ratio; posterior corneal radius/anterior corneal radius) in patients without corneal abnormalities, and to investigate which parameters affect this ratio. Methods: Five thousand eyes from 5,000 patients who underwent cataract surgery were recruited to this study. We explored the linear relationship between B/F ratio and 13 variables using Principal Component-Multivariate Linear Regression Analysis. Results: The B/F ratio was negatively correlated with the difference between simulated keratometry (SimK) and true net power (TNP), central corneal thickness, spherical aberration (SA), and posterior corneal astigmatism and positively correlated with posterior corneal radius, corneal posterior surface, axial length (AL) and anterior corneal radius. Several variables (central corneal thickness, difference between SimK and TNP and asphericity coefficient (Q-value) of the posterior corneal surface) had the highest loading on the final score. B/F ratio reflects the refractive state and anatomical structure of the cornea: thus, higher B/F ratios were associated with larger posterior corneal surface curvature radius, longer axial length, thinner central corneal thickness, lower high order aberrations of the cornea and SA, and the numerical difference between simK and TNP gradually reduced. In clinical practice, for patients with lower B/F ratio, special care should be taken in the choice of system used for intraocular lens (IOL) measurements.

Analysis of Lens Thickness Distribution Based on Swept-Source Optical Coherence Tomography (SS-OCT)

Objective. This study aimed to analyze the distribution of lens thickness (LT) and its associations in age-related cataract patients based on swept-source optical coherence tomography (SS-OCT). Methods. This cross-sectional study included 59,726 Chinese age-related cataract patients. Only right-eye data were included in the study. Repeated measures of ocular parameters were performed using an IOL Master 700 device. The distributions of ocular biometric data including anterior chamber depth (ACD), LT, axial length (AL), central corneal thickness (CCT), white-to-white (WTW), and mean keratometry (MK) and their associations with age were assessed. The anterior segment (AS) was measured as the sum of CCT, ACD, and LT, while the vitreous chamber depth (VCD) was calculated as the difference between AL and AS. The values of LT : AL, AS : AL, and VCD : AL in different AL groups and their changes are the main outcome measures used to observe the proportion of the anterior and posterior segments of the eye. Results. Biometric data were available for 59,726 individuals. The mean age was 68.81 years (range = 40–100); 40.62% were male and 59.38% were female. Mean anterior chamber depth (ACD) was 3.02 ± 0.44 mm, mean LT was 4.51 ± 0.44 mm, mean axial length (AL) was 23.89 ± 1.92 mm, mean central corneal thickness (CCT) was 0.53 ± 0.03 mm, mean white-to-white (WTW) was 11.64 ± 0.44 mm, and mean keratometry (MK) was 44.27 ± 1.65 diopter. Female patients had shorter AL, shallower ACD, smaller CCT and WTW, decreased LT, and steeper corneas ( p < 0.005). ACD revealed the strongest negative correlation ( p ≤ 0.001, r = –0.682) with LT. Age ( p ≤ 0.001, r = 0.348) showed a moderate positive correlation, whereas MK ( p ＜ 0.05, r = 0.011), CCT ( p ≤ 0.001, r = 0.041) had a weak positive correlation and WTW ( p ≤ 0.001, r = –0.034) had a weak negative correlation with LT. A nonlinear correlation was found between LT and AL. LT increased with age in both males and females. LT changed variably in eyes with AL less than 27 mm, LT decreased as AL increased, then LT gradually increased as AL increased in extremely long and extra-long eyes ( p ≤ 0.001). LT : AL and AS : AL decreased as AL increased, VCD : AL gradually increased as AL increased in highly myopic eyes, and VCD : AL increased by about 0.01 for every 1 mm increase in AL. Conclusions. Among Chinese age-related cataract patients, we found LT to have the strongest relation with ACD. The lens was thicker in elderly patients and women. The correlation between LT and AL is not a simple negative correlation; with the increase of age, LT decreases first and then increases. The proportion of VCD is constantly rising with the elongation of AL.

A Method of Circular Scleral Buckle Length Calculation in Retinal Detachment Surgery

Purpose. To develop a method of circular buckle length calculation for optimization of circular scleral buckling in retinal detachment surgery.Methods. At the first stage of the study a formula for calculation of optimal circular scleral buckle length for patients with various axial length (AL) of the eyeball was developed (90 eyes). These healthy eyes were divided into three groups, 30 eyes in each: group 1 — AL 19 to 23.5 mm, group 2 — AL 23.6 to 27 mm, group 3 — AL over 27 mm. In all the groups AL and equatorial diameter of the eyeball were measured with ultrasound A- and B- scanning (Тomey UD8000, Tomey AL 3000). Mathematic estimation of equatorial eyeball diameter dependence on AL was performed using correlation and regression analysis and the formula for optimal circular buckle length calculation was derived. At the second stage the derived formula was used in clinic during retinal detachment surgery in 15 eyes of 15 patients aged 28 to 44 years (37.6 ± 2.6) with subtotal retinal detachment occupying 2 to 3 quadrants. Follow-up period was 1 to 4 months (2.3 ± 0.5). For control, in all patient’s intraoperative measurement of the eyeball circumference in equatorial zone was performed.Results. The first step of the study revealed high correlation coefficient (r) between AL and equatorial eyeball diameter in groups 1 and 2, 0.89 and 0.87, respectively. In group 3 correlation coefficient was 0.57 which shows moderate correlation between AL and equatorial eyeball diameter. Group 3 (AL > 27 mm) was not included in deriving the formula for circular buckle length calculation. Finally, regression equation was obtained and the following formula for circular buckle length calculation was derived: L = 0.9π (8.05 + 0.66 AL), where L — circular buckle length, π = 3.14, AL — axial length of the eyeball. At the second stage of the study (eyes with AL less than 27 mm) anatomical attachment of the retina was achieved in all 15 cases (100 %), elevation of the buckle was 1.44 to 1.6 mm (1.5 ± 0.02), circular buckle shortening made 10 % of the initial eyeball diameter. Control measurement of eyeball diameter in equatorial zone coincided with calculated values, that is, equaled the data obtained from presented formula and from preoperative ultrasound measurement of equatorial eyeball diameter.Conclusions. The derived formula for circular buckle length calculation is highly effective for eyes with AL less than 27 mm: provides optimal height of impression roll (approximately 1.5 mm), reduces the risk of postoperative complications, it is simple in use and shortens the operation time. For calculation of circular buckle length for eyes with AL over 27 mm it is reasonable to use the data of preoperative ultrasound A-scan measurement of equatorial diameter of the eyeball.

Comparison of biometric methods in young children with congenital cataracts in their eyes

BACKGROUND: Relevant keratometric and biometric indicators are necessary for intraocular lens (IOL) power calculation, which is difficult to verify in young children. AIM: Evaluation of the accuracy of various ultrasound methods and optical biometry for axial length measurement in young children with congenital cataracts. MATERIAL AND METHODS: Forty-six children (74 eyes) with congenital cataracts (43 eyes) and pseudophakia (31 eyes) at the age of 6 months to 4 years were examined. Various methods measured the axial length: ultrasound A-scan under general anesthesia by US-4000, ultrasound B-scan without general anesthesia by Voluson E8, and optical biometry by AL-Scan in cases of transparent optics. RESULTS: The greater axial length difference was observed between A-scan and optical biometry (less by 0,78 mm) than between B-scan and optical biometry (more by 0,27 mm). The median axial length difference between A-scan and B-scan was equal for infants and young children with congenital cataracts (0,525 mm and 0,535 mm, respectively). CONCLUSION: Axial length should be measured by different methods in young children with their further comparison to obtaining more accurate biometric indicators for IOL power calculation. The decrease of 12 mm in axial length, which occurs during the A-scan, can lead to errors in the IOL calculation of 36 diopters and unplanned refraction in the long-term period.

Simulation and Optimization of the Nozzle Section Geometry for a Suspension Abrasive Water Jet

In order to improve the life cycle and cutting ability of a suspension abrasive water jet nozzle at the same time, hydrodynamics technology, an enumeration method and multiparameter orthogonal optimization are used to optimize the nozzle section geometry, taking the inlet diameter coefficient of the nozzle, the axial length coefficient of the contraction section and the contraction section curve as optimization variables, and selecting the peak velocity and the unit flow erosion rate as the indicators, it is concluded that the optimal contraction section curve is a Widosinski curve, the optimal inlet diameter coefficient of the nozzle is 0.333 and the optimal axial length coefficient of the contraction section is 2.857. Compared with the commercial product single cone nozzle, the performance of the optimal section nozzle improves by 5.64% and the life cycle increases by 43.2%. On this basis, the effects of operating parameters, including inlet pressure, abrasive particle flow rate and abrasive particle size, are further studied. It is determined that the optimal section nozzle has the best performance under the above operating parameters. It is demonstrated that by optimizing the nozzle section geometry, the cutting capacity and life cycle of the nozzle are improved, the performance of the nozzle can be significantly improved and the optimization of the performance of the nozzle is realized.