Ophthalmic Instruments Research Articles

Corneal Biomechanical Parameters after 60-Year-Old.

To determine the distribution of corneal biomechanical parameters in an elderly population. This cross-sectional study was conducted in subjects above 60 years living in Tehran. The participants were selected using multi-stage cluster sampling. Corneal biomechanical parameters were measured in a randomly selected subsample of this population using the Reichert Ocular Response Analyzer (Reichert Ophthalmic Instruments, Inc., Buffalo, NY, USA). Of 470 subjects, the data of 420 participants aged over 60 years were analyzed (mean age: 69.3 ± 6.5 years and range: 61-88 years), 363 (86.4%) of whom were male. The mean and standard deviation of corneal hysteresis (CH) and corneal resistance factor (CRF) were 8.37 ± 1.55 mmHg (95% confidence interval [CI]: 8.02-8.72) and 9.06 ± 1.70 mmHg (95% CI: 8.69-9.44), respectively. The mean CH was 8.27 ± 1.54 mmHg in men and 9.25 ± 1.28 mmHg in women, and the mean CRF was 9.00 ± 1.71 mmHg in men and 9.63 ± 1.37 mmHg in women. According to the results of multiple linear logistic regression analysis, CH had a significant association with younger age (β = -0.05, P = 0.032), female sex (β = 1.83, P < 0.001), reduced maximum keratometry (β = -0.22, P = 0.06), and increased anterior chamber volume (β = 0.01, P = 0.007). CRF had a significant correlation with a younger age (β = -0.06, P = 0.02), female sex (β = 1.01, P = 0.05), central corneal thickness (β = 0.02, P < 0.001), and reduced maximum keratometry (β = -0.39, P = 0.010). The mean CH and CRF values were low in this sample of the Iranian population aged over 60 years indicating the weaker elasticity of the corneal connective tissue.

Evaluation of Corneal Biomechanical Indices in Distinguishing Between Normal, Very Asymmetric, and Bilateral Keratoconic Eyes

PURPOSE: To evaluate the ability of biomechanical indices provided by the Ocular Response Analyzer (ORA; Reichert Ophthalmic Instruments) and dynamic Scheimpflug analyzer (Corvis ST; Oculus Optikgeräte GmbH) to distinguish between normal eyes and eyes with very asymmetric ectasia (VAE) and mild and moderate keratoconus. METHODS: This prospective, observational, and monocentric study included normal eyes (defined as keratoconus percentage index &lt; 60, Belin/Ambrósio total deviation value [BAD-D] &lt; 1.6, inferior-superior keratometry [I-S value] &lt; 1.45 and maximum keratometry [Kmax] &lt; 47) and eyes with clinical bilateral keratoconus (mild and moderate) and VAE (defined as unilateral keratoconus, where one eye showed a clinical keratoconus and the fellow eye was topographically normal [VAE-NT] or topographically and tomographically normal [VAE-NTT]). All eyes were measured by the Pentacam (Oculus Optikgeräte GmbH), ORA, and Corvis ST. Receiver operating characteristic curve analysis was performed to test the diagnostic ability. RESULTS: Fifty-eight normal eyes and 238 ectatic eyes were included. The highest area under the curve (AUC) was provided by the Corvis Biomechanical Index (CBI) with an AUC of 0.979, followed by ORA corneal resistance factor (0.865), and corneal hysteresis (0.824) separating normal eyes from all ectatic subgroups. The AUC of the CBI was statistically significantly higher than all other parameters (DeLong test, P &lt; .001). A sensitivity of 100% and 70.9%, respectively, and a specificity of 93.1% was found to distinguish normal eyes from VAE-NT and VAE-NTT using a cut-off value of 0.2. CONCLUSIONS: The assessment of biomechanical properties is an additional important method to evaluate corneal ectasia independent of its stage. The CBI provides further information for ectasia screening in cases where corneal topography and tomography are clinically not suspicious by using a cutoff of 0.2. [ J Refract Surg . 2022;38(6):364–372.]

La Vie En Rose - Danièle Sylvie Aron-Rosa

La Vie En Rose - Danièle Sylvie Aron-Rosa

Local curvatures and its measurements of an optical surface or a wavefront: a review

The mathematical tools to calculate surface and wavefront local curvatures have been growing in importance because, when studying and evaluating some optical systems, the local curvature becomes extremely important. Many practical methods have been created to measure the wavefront shape and local curvatures as well as many mathematical tools to describe them. These methods are very useful in ophthalmology mainly for corneal evaluation, but the methods are now being used in other fields of optical metrology, especially in optical testing, interferometric wavefront description, and others. In some instruments and optical devices, mainly ophthalmic and optometric instruments, the local curvatures distribution over the pupil of an optical system is more important than the wavefront topography. A typical example is a human eye, in which corneal topographers, eye aberrometers, and several other instruments are used to measure the local curvatures. In particular, the main aspects of the curvature calculation at a given point for different slopes in any direction are introduced. The principal curvatures, mean, Gaussian, cylindrical, tangential, and sagittal curvatures are described. In the second part of this review, we describe the main methods and devices for wavefront sensing, measuring elevations, slopes, or curvatures. We conclude with a description of some methods to measure and calculate local curvatures from wavefront sensors by measuring the wavefront elevations, the transverse aberrations (slopes), or directly the curvatures.

Reducing topical drug waste in ophthalmic surgery: multisociety position paper.

This position article on reducing topical drug waste with ophthalmic surgery was written by the Ophthalmic Instrument Cleaning and Sterilization Task Force, comprising representatives of the ASCRS, American Academy of Ophthalmology, American Glaucoma Society, and Outpatient Ophthalmic Surgery Society. Drug waste significantly increases the costs and carbon footprint of ophthalmic surgery. Surgical facilities should be permitted to use topical drugs in multidose containers on multiple patients until the manufacturer's labeled date of expiration, if proper guidelines are followed. Surgical patients requiring a topical medication not used for other patients should be allowed to bring that partially used medication home for postoperative use. These recommendations are based on published evidence and clarification of policies from multiple regulatory and accrediting agencies with jurisdiction over surgical facilities. Surveys suggest that most ambulatory surgery centers and hospitals performing cataract surgery are wasting topical drugs unnecessarily.

Translation model for CW chord to angle Alpha derived from a Monte-Carlo simulation based on raytracing.

The Chang-Waring chord is provided by many ophthalmic instruments, but proper interpretation of this chord for use in centring refractive procedures at the cornea is not fully understood. The purpose of this study is to develop a strategy for translating the Chang-Waring chord (position of pupil centre relative to the Purkinje reflex PI) into angle Alpha using raytracing techniques. The retrospective analysis was based on a large dataset of 8959 measurements of 8959 eyes from 1 clinical centre, using the Casia2 anterior segment tomographer. An optical model based on: corneal front and back surface radius Ra and Rp, asphericities Qa and Qp, corneal thickness CCT, anterior chamber depth ACD, and pupil centre position (X-Y position: PupX and PupY), was defined for each measurement. Using raytracing rays with an incident angle IX and IY the CW chord (CWX and CWY) was calculated. Using these data, a multivariable linear model was built up in terms of a Monte-Carlo simulation for a simple translation of incident ray angle to CW chord. Raytracing allows for calculation of the CW chord CWX/CWY from biometric measures and the incident ray angle IX/IY. In our dataset mean values of CWX = 0.32±0.30 mm and CWY = -0.10±0.26 mm were derived for a mean incident ray angle (angle Alpha) of IX = -5.02±1.77° and IY = 0.01±1.47°. The raytracing results could be modelled with a linear multivariable model, and the effect sizes for the prediction model for CWX are identified as Ra, Qa, Rp, CCT, ACD, PupX, PupY, IX, and for CWY they are Ra, Rp, PupY, and IY. Today the CW chord can be directly measured with any biometer, topographer or tomographer. If biometric measures of Ra, Qa, Rp, CCT, ACD, PupX, PupY are available in addition to the CW chord components CWX and CWY, a prediction of angle Alpha is possible using a simple matrix operation.

Corneal hysteresis and intraocular pressure are altered in silicone-hydrogel soft contact lenses wearers

PurposeThe aim of this work is to determinate the effects in the physical parameters in terms of intraocular pressure (IOP) and central corneal thickness (CCT) and corneal biomechanics in terms of corneal resistance factor (CRF) and corneal hysteresis (CH) of wearing silicone-hydrogel soft contact lenses (SiH-CLs) in young adult subjects during a short-term follow-up.Methods40 eyes of 20 healthy patients with a mean age of 22.87 ± 4.14 were involved in this study. Subjects with corneal diseases, dry eye, irregular astigmatism or who have been previous contact lens wearers were excluded. The ocular response analyzer (Reichert Ophthalmic Instruments) was used to measure CH, CRF and IOP and Scheimpflug imaging (the GALILEI™ Dual Scheimpflug camera analyzer, Ziemer) was used to measure CCT before and 10 days (Group 1) and 20 days (Group 2) after wearing the SiH-CLs.ResultsIOP was significantly decreased 10 days after using the SiH-CLs (p = 0.009). Within the 20 days' period, Group 2 revealed an even more pronounced decrease in IOP (p = 0.003) while CH increased significantly (p = 0.04). CCT and CRF did not show a significant change during the period of SiH-CLs use. Our finding allowed obtaining an empirical expression that relates IOP, CCT, CRF and CH within a biomechanical compensation experimental model.ConclusionsCorneal biomechanical parameters and physical properties of the cornea may be altered due to SiH-CLs use. Our findings could have an impact on the management of glaucoma progression and ocular hypertension.

Influence of Fine Management Combined With PDCA Cycle Method on Disinfection Qualified Rate and Performance Grade of Ophthalmic Precision Instruments

ObjectiveThe aim of this study is to explore the influence of fine management combined with the plan-do-check-action (PDCA) cycle method on the management of ophthalmic precision instruments.MethodsThe ophthalmic precision instruments centralized in the disinfection supply room of our hospital were selected as the research objects and divided into groups A and B. Traditional instrument management method was adopted in group A, and fine management combined with the PDCA cycle method based on the group A was adopted in group B. The instrument management risk scores, the qualified rate of disinfection, instrument performance grade, and incidence of toxic anterior segment syndrome (TASS) of the two groups were compared.ResultsThe risk scores of instrument management and incidence of TASS in group B were lower than those in group A (p < 0.05). The qualified rate of disinfection and instrument performance grades in group B were higher than those in group A (p < 0.05).ConclusionFine management combined with the PDCA cycle method can improve the qualified rate of disinfection of ophthalmic precision instruments, optimize the performance of instruments, reduce the risk of instrument management, and reduce the incidence of TASS.

Beware what lurks on the surface - persistent contamination of high-touch surfaces on slit lamps despite regular cleaning.

High-touch surfaces contributing to infection transmission are particularly concerning in the ophthalmology clinic where frequent contact exists between ophthalmologists and various ophthalmic instruments. Areas of surface contamination from an ophthalmologist's contact with the slit lamp environment were identified using ultraviolet fluorescence as a surrogate for pathogen contamination. Ultraviolet fluorescent product was applied on the ophthalmologist's hands after thorough hand washing to indicate the contamination that may be derived from multiple sources in the ophthalmology clinic, such as touching the patient or the patient's folder during eye examinations and transfers. The ophthalmology clinic was run normally, with the ophthalmologist wiping down patient-contact surfaces on the slit lamp and performing thorough hand hygiene after every patient. Using ultraviolet black light, persistence of surface contamination in the slit lamp environment was identified and evaluated across five days. High-touch surfaces of suboptimal disinfection were inclined towards those touched only by the ophthalmologist, for example: joystick and chin-rest adjustment knob, as compared to patient-contact surfaces. Persistent contamination on the same surfaces revealed inefficacy of current hand hygiene and clinical disinfection practices. This poses a significant risk for pathogen transmission and underscores the importance of including these specific clinician high-touch surfaces in existing cleaning protocols.

Measuring axial length of the eye from magnetic resonance brain imaging

BackgroundMetrics derived from the human eye are increasingly used as biomarkers and endpoints in studies of cardiovascular, cerebrovascular and neurological disease. In this context, it is important to account for potential confounding that can arise from differences in ocular dimensions between individuals, for example, differences in globe size.MethodsWe measured axial length, a geometric parameter describing eye size from T2-weighted brain MRI scans using three different image analysis software packages (Mango, ITK and Carestream) and compared results to biometry measurements from a specialized ophthalmic instrument (IOLMaster 500) as the reference standard.ResultsNinety-three healthy research participants of mean age 51.0 ± SD 5.4 years were analyzed. The level of agreement between the MRI-derived measurements and the reference standard was described by mean differences as follows, Mango − 0.8 mm; ITK − 0.5 mm; and Carestream − 0.1 mm (upper/lower 95% limits of agreement across the three tools ranged from 0.9 mm to − 2.6 mm). Inter-rater reproducibility was between − 0.03 mm and 0.45 mm (ICC 0.65 to 0.93). Intra-rater repeatability was between 0.0 mm and − 0.2 mm (ICC 0.90 to 0.95).ConclusionsWe demonstrate that axial measurements of the eye derived from brain MRI are within 3.5% of the reference standard globe length of 24.1 mm. However, the limits of agreement could be considered clinically significant. Axial length of the eye obtained from MRI is not a replacement for the precision of biometry, but in the absence of biometry it could provide sufficient accuracy to act as a proxy. We recommend measuring eye axial length from MRI in studies that do not have biometry but use retinal imaging to study neurodegenerative changes so as to control for differing eye size across individuals.

Corneal biomechanics in a pediatric population

AbstractPurposeThe purpose of the study is to explore the relationship between biomechanical corneal parameters and axial length in a pediatric population.MethodsWe conducted a prospective study that included 82 eyes from 41 pediatric patients. All patients were submitted to a complete ophthalmologic examination that included autorefractometry (before and after pharmacological cycloplegia), slit lamp and fundus examination, ocular tonometry. Additionally, the patients underwent examination with Ocular Response Analyzer (Reichert Ophthalmic Instruments Inc., Depew, NY) to determine corneal hysteresis (CH), corneal resistance factor (CRF) and with Aladdin biometer (Topcon, Tokyo, Japan) to determine axial length (AL) and central corneal thickness (CCT). Statistical analysis was performed using IBMSPSS Statistics 26.ResultsOur study included 82 eyes, from 41 patients (63.41% female, 36.59% male). The average age was 13.29 years old (12.92 in females, 13.93 in males). Average CH, CRF, and spherical power, respectively, were similar between sexes: 12.30 mmHg, 12.47 mmHg, −0.70 D respectively in females, 12.89 mmHg, 13.31 mmHg and −1.27 D respectively in males. Mean AL and CCT are larger in males than in females, in a statistically significantmanner. Average AL is 23.69 mm in females, 24.52 mm in males (p = 0.007) and average CCT is 0.558 mm in females and 0.583 mm in males (p = 0.003). We also found a statistically significant moderate negative correlation between CH and AL in the pediatric population (Pearson’s r of −0.350, p = 0.001), and also in both sexes (Pearson’s r of −0.419, p = 0.002 in females and −0.437, p = 0.016 in males).ConclusionsOur study reveals that in the pediatric population, at similar age, males have a thicker central cornea and longer axial length. Furthermore, in these patients, a high axial length is correlated to a low corneal hysteresis. Further studies are needed to explore these data and to confirm these findings in adults.

Evaluation of corneal biomechanical properties in spherical and toric soft contact lens wear

Purpose: Corneal hysteresis (CH) and corneal resistance factor was found to be less for patient wearing toric contact lens as compared to soft spherical CH was calculated as the difference in air pressures between force-in applanation (P1) and force-out applanation (P2), or (P1–P2). Materials and Methods: This was the prospective study, 40 eyes of 22 patients with mean age of 22.09 ± 4.05 years. Eleven eyes were fitted with soft toric contact lens and 29 eyes were fitted with soft spherical contact lens. Dry eye, keratoconic or any systemic pathology were excluded. Soft toric and soft spherical contact lenses (Comfilcon A, Coopervision, and Southampton, UK) were fitted. The Ocular response Analyzer (Reichert Ophthalmic Instruments, Depew, New York, USA) was used to measure CH before and after 3 months using soft toric and soft spherical contact lenses. Descriptive statistics were used to analyze the demographic data. Paired t-test was employed for analyzing the difference between the base line value of CH with soft toric and soft spherical contact lens wearers after 3 months. Independent t-test was used to find the association between CH and gender. Results: CH was found to be lesser after 3 months of soft toric contact lens wear, as compared with soft spherical contact lenses. Mean increase of CH was found to range from 10.44 ± 0.96to 10.80 ± 0.96 mmHg (P = 0.000). Conclusion: In this study, there was a decrease in CH after using soft toric contact lenses and increase after using soft spherical contact lenses for 3 months. The increased CH with soft spherical contact lens was reversible in nature. However, CH may differ between lens type and modality of wear which can lead to long-term changes in the corneal biomechanical properties.

Assessment of a Vision-Based Technique for an Automatic Van Herick Measurement System

The adoption of Artificial Intelligence methods within the instrumentation and measurements field is nowadays an attractive research area. On the one hand, making machines learn from data how to perform an activity, rather than hard code sequential instructions, is a convenient and effective solution in many modern research areas. On the other hand, AI allows for the compensation of inaccurate or not complete models of specific phenomena or systems. In this context, this paper investigates the possibility to exploit suitable Machine Learning techniques in a vision-based ophthalmic instrument to perform automatic Anterior Chamber Angle (ACA) measurements. In particular, two CNN&#x2013;based networks have been identified to automatically classify acquired images and select the ones suitable for the Van&#x2013;Herick procedure. Extensive clinical trials have been conducted by clinicians, from which a realistic and heterogeneous image dataset has been collected. The measurement accuracy of the proposed instrument is derived by extracting measures from the images of the aforementioned dataset, as well as the system performances have been assessed with respect to differences in patients&#x2019; eye color. Currently, the ACA measurement procedure is performed manually by appropriately trained medical personnel. For this reason, Machine Learning and Vision&#x2013;Based techniques may greatly improve both test objectiveness and diagnostic accessibility, by enabling an automatic measurement procedure.

Sutureless Manual Extracapsular Cataract Extraction with Club

Purpose: To evaluate the efficacy and safety of cataract extraction through small pupil with the help of a specially designed instrument called club. Study Design: Interventional case series. Place and Duration of Study: Euro eye clinic from January 2019 to December 2019. Methods: Seventeen consecutive patients with pupil diameter of &lt;4mm after maximal pharmacological dilatation were recruited for study. Inclusion criteria was patients with less than 4mm pupil size after maximum pharmacological dilation. Patient with previous anterior segment surgery and small pupil with posterior synechea were excluded. The instrument (club) was originally designed for breaking posterior synechae. Sutureless Manual Extracapsular Cataract Extraction (SMECE), more commonly known as MSICS, was performed in all cases. After tunnel formation and capsulotomy, club was used to bring lens edge out in pupillary margin. Lens was then maneuvered into anterior chamber and expressed out. Results: All 17 patients had successful SMECE. In one patient pupil was stretched before applying instrument. None of the patients had posterior capsular rupture or hyphaema. Conclusion: This instrument designed in Center of Ophthalmic Instrument and Equipment Designing (COIED) is very useful, safe and cost effective. In Extra Capsular Cataract Extraction (ECCE) or SMECE, surgeons usually do keyhole iridotomy, mechanical stretching or multiple sphincterotomies for managing small pupil. With this new instrument, cataract extraction can be done without surgical trauma to the pupil, thus preserving pupil shape. Key Words: Sutureless Manual Extra capsular Cataract Extraction (SMECE), Manual Small Incision Cataract Surgery (MSICS), Miosis.

Prediction of CW chord as a measure for the eye's orientation axis after cataract surgery from preoperative IOLMaster 700 measurement data.

The angles alpha and kappa are widely discussed for centring refractive procedures, but they cannot be determined with ophthalmic instruments. The purpose of this study is to investigate the Chang-Waring chord (position of the Purkinje reflex PI relative to the corneal centre) derived from an optical biometer before and after cataract surgery and to study the changes resulting from cataract surgery. The analysis was based on a large dataset of 1587 complete sets of preoperative and postoperative IOMaster 700 biometry measurements from two clinical centres, each containing: valid data for pupil and corneal centre position, the position of the Purkinje reflex PI originated from a coaxial fixation target, keratometry (K), axial length (AL), anterior chamber depth (ACD), lens thickness (LT), central corneal thickness CCT, and horizontal corneal diameter W2W. The Chang-Waring chord CW was derived from pupil centre and Purkinje reflex PI analysed preoperatively and postoperatively, and a multilinear regression model together with a feedforward neural network algorithm was set up to predict postoperative CW chord from preoperative CW chord, K and biometric distances of the eye. The Y component of CW chord shows a slight shift in the inferior direction in both left and right eyes, before and after cataract surgery. The X component shows some shift in the temporal direction, which is more pronounced preoperatively and slightly reduced postoperatively but with a larger variation. The change in CW chord from preoperative to postoperative shows a slight shift in the superior and nasal directions. Our algorithms for prediction of postoperative CW chord using preoperative CW chord, keratometry and biometry as input data performed with a multilinear regression and a feedforward neural network approach were able to reduce the variance, but could not properly predict the postoperative CW chord X and Y components. The CW chord as the position of the Purkinje reflex PI with respect to the pupil centre can be directly measured with any biometer, topographer or tomographer with a coaxial fixation light. The mean Y component does not differ between right and left eyes or preoperatively and postoperatively, but the mean temporal shift of the X component preoperatively is slightly reduced postoperatively, but with a larger scatter of the values.

Corneal Surgery in the Cat: Diseases, considerations and techniques.

The ability to recognize, diagnose and treat corneal disease is essential for maintaining vision and comfort in feline patients. Being able to correctly identify appropriate techniques for surgical cases is of particular importance for success when performing corneal surgery. Many different corneal diseases present with similar clinical signs, and it can be hard to determine the appropriate treatment for individual patients. It is essential for the clinician to understand the indications for corneal surgery, instrumentation needed and microsurgical principles prior to attempting these procedures. The prognosis following surgery and potential complications should be discussed with the client. This review article aims to assist in decision-making and to provide detailed guidance for primary care clinicians considering referral of cats for corneal surgery. The review outlines common feline corneal diseases and associated surgical therapies performed by veterinary ophthalmologists, highlighting appropriate instrumentation and case selection. Some surgeries are explained in depth for ophthalmologists and residents in training. Although some procedures may be performed with common surgical equipment and supplies, most require specialized ophthalmic instrumentation and expertise, which entails significant microsurgical training and practice, as well as financial investment. Most of the procedures require an operating microscope for the best surgical outcomes; however, surgical loupes may be sufficient in some cases. Evidence base: This review article compiles information from many published references on feline corneal diseases and surgeries, complemented by the experience of the authors.

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus - Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year.

The etiology of keratoconus (KC) is probably multifactorial but remains essentially unknown. Previous scientific observations have suggested that hypothyroidism might play a role in the development and progression of KC. The purpose of this study was to analyze the tomographic and biomechanical parameters in KC patients with or without hypothyroidism. Twenty-eight patients with KC and hypothyroidism (HT group) and fifty-six KC patients without thyroid dysfunction (WHT group) with matching gender and age were analyzed. Mean age was 40.3 years (range 14 - 57) in the HT group and 40.3 years (range 14 - 57) in the WHT group. Routine ophthalmic examinations consisted of corneal tomography and biomechanical parameters. We extracted the following KC parameters from the Pentacam (Pentacam HR, Oculus, Wetzlar, Germany): Keratoconus Index (KI), maximum keratometry (Kmax), astigmatism, and thinnest pachymetry (TP). From the ocular response analyzer (ORA, Reichert Ophthalmic Instruments, Depew, NY, USA), we extracted corneal hysteresis (CH), corneal resistance factor (CRF), and KC match index (KMI). The comparison of the tomographic and biomechanical values from cross-sectional and longitudinal analyses showed no significant differences between the HT and WHT groups. The severity of KC based on tomographical and biomechanical parameters does not seem to depend on the presence of hypothyroidism.

Analysis of ocular structural parameters and higher-order aberrations in Chinese children with myopia.

BACKGROUNDMyopia and high myopia are global public health concerns. Patients with high myopia account for 0.5%-5.0% of the global population. AIMTo examine diopters, axial length (AL), higher-order aberrations, and other ocular parameters in Chinese children with myopia, to analyze the influence of structural parameters associated with myopia on visual quality, and to provide a theoretical basis for the prevention and treatment of childhood myopia and high myopia.METHODSThis study included 195 children aged 6–17 years with myopia. The AL was measured with an ultrasonic ophthalmic diagnostic instrument, and the aberrations, corneal curvature (minimum K1, maximum K2, and average Km), central corneal thickness, anterior chamber depth, and anterior chamber angle were measured using a Sirius three-dimensional anterior segment analyzer. Using a standard formula, the corneal radius of curvature R (337.3/Km) and AL/R values were obtained.RESULTSThe diopter of high myopia compared with low-middle myopia was correlated with age and AL (r = -0.336, -0.405, P < 0.001), and AL of high myopia was negatively correlated with K1, K2, and Km (r = -0.673, -0.661, and -0.680, respectively; P < 0.001), and positively correlated with age and the anterior chamber depth (r = 0.214 and 0.275, respectively; P < 0.05). AL/R was more closely related to diopter than AL in children with myopia, and 94.4% of children with myopia had an AL/R of > 3.00.CONCLUSIONThe ocular structural parameters of children change because of different diopters. AL/R is more specific and sensitive than AL in evaluating the refractive status of myopia in children. An AL/R of > 3.00 may be used as a specific index of myopia in children. There are differences in AL/R between high myopia and low-middle myopia, which can be used for the classification of ametropia. The degree of myopia has a certain influence on higher-order aberrations.

Stereoacuity Among Patients with Refractive Error at University of Gondar, Northwest Ethiopia.

PurposeThis study aimed to assess the level of stereopsis, proportion of poor stereopsis, and factors influencing stereopsis in adults with refractive error.MethodsThis was a cross-sectional, descriptive study conducted on 153 adults with refractive error at Gondar University Hospital Tertiary Eye Care Center from April 08 to June 07, 2019. Structured questionnaires and ophthalmic instruments (Retinoscope, Worth Four Dot test and TNO Stereo plates) were used to collect the data. Data were entered and analyzed with Statistical Package for Social Sciences (SPSS) version 20. The result was summarized using summary statistics such as mean. Chi-squared test of association was applied between stereopsis and independent variables.ResultsThe level of stereopsis after correction of refractive error ranged from 1.89 to 2.65 log arc second. Before correction of refractive error, poor stereopsis was observed in 46.4% of the participants, while after correction, it dropped to 39.8% (CI: 95%: 31.1%–47.8%). Stereopsis after correction had a significant association with age, best visual acuity, type of refractive error, and fusional status at distance with a p value < 0.05.ConclusionGiven refractive error corrected, the mean stereopsis in patients with refractive error was 2.42 log arc second. Proportion of poor stereopsis was noted in 39.8% of the participants corrected for refractive error. Age, best corrected visual acuity, type of refractive error, and fusional status had a significant association with stereopsis. Further studies on stereoacuity on a large scale are recommended.

A review of additive manufacturing applications in ophthalmology.

Additive Manufacturing (AM) capabilities in terms of product customization, manufacture of complex shape, minimal time, and low volume production those are very well suited for medical implants and biological models. AM technology permits the fabrication of physical object based on the 3D CAD model through layer by layer manufacturing method. AM use Magnetic Resonance Image (MRI), Computed Tomography (CT), and 3D scanning images and these data are converted into surface tessellation language (STL) file for fabrication. The applications of AM in ophthalmology includes diagnosis and treatment planning, customized prosthesis, implants, surgical practice/simulation, pre-operative surgical planning, fabrication of assistive tools, surgical tools, and instruments. In this article, development of AM technology in ophthalmology and its potential applications is reviewed. The aim of this study is nurturing an awareness of the engineers and ophthalmologists to enhance the ophthalmic devices and instruments. Here some of the 3D printed case examples of functional prototype and concept prototypes are carried out to understand the capabilities of this technology. This research paper explores the possibility of AM technology that can be successfully executed in the ophthalmology field for developing innovative products. This novel technique is used toward improving the quality of treatment and surgical skills by customization and pre-operative treatment planning which are more promising factors.