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Acta Ophthalmologica Scandinavica Aug 2007This review describes the principles and practices involved in the calculation of intraocular lens (IOL) power. The theories behind formulas for calculating IOL power... (Review)
Review
This review describes the principles and practices involved in the calculation of intraocular lens (IOL) power. The theories behind formulas for calculating IOL power are described, using regression and optical methods employing 'thin lens' and 'thick lens' models, as well as exact ray-tracing methods. Numerical examples are included to illustrate the points made. The paper emphasizes the importance of establishing an accurate estimation of corneal power as well as an accurate technique for the measurement of axial length and accurate methods of predicting postoperative anterior chamber depth (ACD). It is concluded that current improvements in diagnostic and surgical technology, combined with the latest generation IOL power formulas, make the calculation and selection of appropriate IOL power among the most effective tools in refractive surgery today.
Topics: Anterior Chamber; Biometry; Cornea; Humans; Lens Implantation, Intraocular; Lenses, Intraocular; Optics and Photonics; Phacoemulsification; Refraction, Ocular
PubMed: 17403024
DOI: 10.1111/j.1600-0420.2007.00879.x -
Clinical & Experimental Optometry Jan 2021Proper selection of phakic intraocular lens diameter is necessary to avoid complications related with excessive vaulting after its implantation.
CLINICAL RELEVANCE
Proper selection of phakic intraocular lens diameter is necessary to avoid complications related with excessive vaulting after its implantation.
BACKGROUND
Horizontal corneal diameter, measured as white-to-white distance, is one of the parameters used for phakic intraocular lens diameter calculation. Agreement was assessed between three parameters: white-to-white distance obtained with swept source optical coherence tomography, and white-to-white distance obtained with Scheimpflug camera and angle-to-angle parameter obtained with anterior segment optical coherence tomography.
METHODS
This study included 55 eyes of 43 patients. The white-to-white distance was measured with two biometry techniques: swept source optical coherence tomography and Scheimpflug camera. The angle-to-angle was measured with anterior segment optical coherence tomography. Analysis of agreement was performed by the Bland-Altman method. For every patient, simulation of Visian Implantable Collamer Lens (ICL) sizing was performed using the Online Calculation and Ordering System with different white-to-white distance or angle-to-angle.
RESULTS
Statistically significant differences were found between swept source optical coherence tomography biometer and anterior segment optical coherence tomography (p = 0.001) and between swept source optical coherence tomography and Scheimpflug camera (p < 0.001). However, there was a good correlation between swept source optical coherence tomography and Scheimpflug camera (intraclass correlation co-efficient = 0.623), with a shift toward higher white-to-white distance values on swept source optical coherence tomography. A relatively high correlation intraclass correlation co-efficient (0.772) and lack of statistically significant differences (p = 0.068) between anterior segment optical coherence tomography and Scheimpflug camera results were observed. Simulation of phakic intraocular lens sizing showed that swept source optical coherence tomography white-to-white distance should not be used interchangeably with Scheimpflug camera white-to-white distance or angle-to-angle.
CONCLUSION
White-to-white distance measured with swept source optical coherence tomography was significantly different from values obtained with other methods. Angle-to-angle may support ICL sizing, helping in verification of white-to-white distance values obtained with other devices.
Topics: Anterior Chamber; Biometry; Humans; Phakic Intraocular Lenses; Tomography, Optical Coherence
PubMed: 32519362
DOI: 10.1111/cxo.13101 -
BMC Ophthalmology Feb 2022A simple technique to facilitate removal of subincisional cortex in cataract surgery is presented.
BACKGROUND
A simple technique to facilitate removal of subincisional cortex in cataract surgery is presented.
METHODS
A disposable 27-gauge blunt needle attached to a 5.0-ml syringe containing balanced salt solution (BSS) is introduced through the side port incision into the anterior chamber. The tip of the needle is directed toward the capsule fornix beneath the incision site, and BSS is flushed to disperse the remaining cortex. Thereafter, the coaxial irrigation/aspiration device is used to remove the loosened cortex.
RESULTS
This technique was used in 60 eyes of 60 patients with difficulty of removing cortical remnant in the subincisional space. Subincisional cortical material was successfully removed in 93.3% (56/60 eyes). There were no intraoperative and postoperative complications related to this procedure.
CONCLUSIONS
The hydro-dispersion technique is a simple and safe approach to remove the subincisional cortical material that is difficult to manage with the standard coaxial irrigation/aspiration device.
Topics: Anterior Chamber; Cataract Extraction; Humans; Lens, Crystalline; Phacoemulsification; Postoperative Complications; Therapeutic Irrigation
PubMed: 35177028
DOI: 10.1186/s12886-022-02314-0 -
Eye (London, England) Jan 2020Differentiating the two main forms of primary glaucoma (open-angle and closed-angle glaucoma) depends on the correct assessment of the anterior chamber angle (ACA). This... (Review)
Review
Differentiating the two main forms of primary glaucoma (open-angle and closed-angle glaucoma) depends on the correct assessment of the anterior chamber angle (ACA). This assessment will determine the management plan and prognosis for the disease. The standard method of examining the angle has been, for many years, slit-lamp gonioscopy. This method, although clinically still useful, is less robust for patient follow up and clinical research, given its low reproducibility. Several imaging technologies have been developed in recent years to improve the evaluation of the ACA and overcome the shortcomings of gonioscopy. These recent advances include three-dimensional and 360° analysis by Swept-Source OCT (SS-OCT, CASIA, Tomey, Nagoya, Japan), the introduction of deep learning algorithms for automatic imaging classification and new goniophotographic systems. SS-OCT allows for the first time the assessment of the circumferential extension of angle closure with moderate to good diagnostic performance compared with gonioscopy. Deep learning algorithms are showing promising results for the automation of imaging analysis, and may potentially save physicians' time in regards of the interpretation of the images. Lastly, goniophotograph systems have the distinct advantage of recordability of gonioscopic findings and are most closely matched to the findings of slit-lamp gonioscopy.
Topics: Anterior Chamber; Anterior Eye Segment; Glaucoma, Angle-Closure; Gonioscopy; Humans; Intraocular Pressure; Japan; Prospective Studies; Reproducibility of Results; Tomography, Optical Coherence
PubMed: 31666710
DOI: 10.1038/s41433-019-0655-0 -
Translational Vision Science &... May 2021To establish anterior chamber measurements in children and investigate the influence of demographic factors on anterior chamber development.
PURPOSE
To establish anterior chamber measurements in children and investigate the influence of demographic factors on anterior chamber development.
METHODS
Handheld optical coherence tomography was used to scan the anterior chamber of participants' eyes, without sedation. ImageJ was used to generate quantitative anterior chamber measurements, including central corneal thickness (CCT), anterior chamber width, trabecular meshwork length (TML), Schwalbe's line-angle opening distance (SL-AOD), and trabecular iris surface area (SL-TISA). The average anterior chamber measurements per age group, with 95% prediction intervals, were estimated using fractional polynomial modeling. Mixed regression models were used to evaluate the influence of age, gender, eye, angle, and refractive error variation on anterior chamber measurements.
RESULTS
Scans from 223 healthy children (2 days to 15 years of age) and 59 adults (16 to 47 years of age) were included. The anterior chamber width, TML, Schwalbe's line-angle opening distance, and Schwalbe's line-trabecular iris surface area significantly increased, whereas CCT decreased with aging (all P < 0.001). The anterior chamber has a rapid phase of development during the first 18 months of age and reaches maturity by the age of 5 years. Girls have significantly smaller anterior chambers compared with boys (all P < 0.001). There was no difference between right and left eye development (all P > 0.05). The temporal TML development was significantly greater than the nasal TML (P < 0.05). CCT development was negatively correlated with refractive power.
CONCLUSIONS
This novel, non-invasive study describes the postnatal development of anterior chamber in newborn children.
TRANSLATIONAL RELEVANCE
Our established quantitative measurements have potential clinical use in understanding anterior segment diseases.
Topics: Adult; Anterior Chamber; Child, Preschool; Cross-Sectional Studies; Female; Humans; Infant, Newborn; Iris; Male; Middle Aged; Tomography, Optical Coherence; Trabecular Meshwork
PubMed: 34111257
DOI: 10.1167/tvst.10.6.13 -
Indian Journal of Ophthalmology Dec 2022
Topics: Child; Humans; Anterior Chamber; Lenses, Intraocular
PubMed: 36453376
DOI: 10.4103/ijo.IJO_1644_22 -
Veterinary Ophthalmology May 2022To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness...
OBJECTIVE
To determine corneal thickness (CT) and axial anterior chamber depth (ACD) using ultrasound biomicroscopy (UBM) in normal adult horses. To compare corneal thickness measurements between UBM and ultrasonic pachymetry.
ANIMALS STUDIED
Sixty eyes of 30 healthy adult horses aged 8-24 years.
PROCEDURES
Ultrasonic pachymetry (velocity of 1640 m/s) was utilized to obtain measurements of the central, superior, temporal, inferior, and nasal cornea. Triplicate images of the same corneal locations were acquired using UBM (50 MHz). Images of the axial anterior chamber were used to measure ACD. Intraocular pressure (IOP) was estimated using rebound tonometry, and axial globe length was measured using ultrasonographic biometry.
RESULTS
CT (mean ± SD µm) measured by UBM was 854 ± 61 (central), 994 ± 58 (superior), 930 ± 57 (temporal), 979 ± 55 (inferior), and 898 ± 48 (nasal). CT measured by UBM was greater than that measured by ultrasonic pachymetry at all locations and was statistically significant at all locations except inferior (p = 0.0006-0.048). No sex nor age effect was detected for CT at any location. The repeatability of ultrasonic pachymetry was superior to that of UBM. Mean ± SD ACD was 5.74 ± 0.41 mm. A weak positive correlation was identified between central CT and IOP and between central CT and axial globe length.
CONCLUSIONS
Normal data for CT and ACD of the adult horse obtained using UBM are provided. CT determined by UBM was greater relative to pachymetry at all corneal locations.
Topics: Animals; Anterior Chamber; Biometry; Cornea; Corneal Pachymetry; Horses; Microscopy, Acoustic
PubMed: 35084084
DOI: 10.1111/vop.12971 -
Eye (London, England) Jun 2022To describe anterior chamber angle (ACA) structures and parameters in primary congenital glaucoma (PCG) and normal infant eyes, using Hand-held anterior segment optical...
PURPOSE
To describe anterior chamber angle (ACA) structures and parameters in primary congenital glaucoma (PCG) and normal infant eyes, using Hand-held anterior segment optical coherence tomography (HH AS-OCT), as an in-office, non-contact technique.
METHODS
Normal and PCG-infants <24 months were examined, using HH AS-OCT (RTVue RT- 100, Optovue Inc., Fremont, CA). Sedation was not required. Corneal pachymetry map, ACA width and iris thickness (IT) were measured. Trabecular meshwork (TM), Schlemm's canal (SC), and scleral spur (SS) identification were assessed in both groups.
RESULTS
Forty-eight infants; (26 PCG-eyes and 22 normal-eyes) aged 9.12 ± 6.7 months, were included. Nasal and temporal ACA width in PCG infants was found significantly larger (39.3 ± 6.6° vs. 30.4 ± 5.6, and 40.1 ± 5.3° vs. 32.5 ± 6.2 respectively) (p < 0.001). IT was significantly reduced (121.7 ± 43.9 μm in PCG-infants, vs. 160.3 ± 38.6 μm in normal-eyes) (p < 0.01). TM was identified in all normal eyes (100%) and nine (34.6%) PCG- eyes. SC was identified in 16 (72.7%) normal eyes versus four (15.4%) PCG. In PCG-eyes, an abnormal structure occluding the angle was seen in seven (26.9%), and a hyper-reflective membrane in five (19.2%), the iris was anteriorly inserted in all PCG-eyes, and iridotrabeculodysgenesis was clearly identified (with constant iris anterior insertion). The abnormal tissue obscuring the angle was seen in younger PCG-infants and iris thinning appeared to be part of the pathology, not a result of IOP elevation.
CONCLUSION
Using HH AS-OCT permits tomographic examination of the ACA in PCG infants and may help in the understanding of disease pathology. Hence, may assist in optimizing treatment.
Topics: Anterior Chamber; Glaucoma; Glaucoma, Angle-Closure; Humans; Infant; Intraocular Pressure; Iris; Tomography, Optical Coherence; Trabecular Meshwork
PubMed: 34117386
DOI: 10.1038/s41433-021-01583-1 -
Pharmacology & Therapeutics May 2019Diabetes develops due to deficient functional β cell mass, insulin resistance, or both. Yet, various challenges in understanding the mechanisms underlying diabetes... (Review)
Review
Diabetes develops due to deficient functional β cell mass, insulin resistance, or both. Yet, various challenges in understanding the mechanisms underlying diabetes development in vivo remain to be overcome owing to the lack of appropriate intravital imaging technologies. To meet these challenges, we have exploited the anterior chamber of the eye (ACE) as a novel imaging site to understand diabetes basics and clinics in vivo. We have developed a technology platform transplanting pancreatic islets into the ACE where they later on can be imaged non-invasively for long time. It turns out that the ACE serves as an optimal imaging site and provides implanted islets with an oxygen-rich milieu and an immune-privileged niche where they undergo optimal engraftment, rich vascularization and dense innervation, preserve organotypic features and live with satisfactory viability and functionality. The ACE technology has led to a series of significant observations. It enables in vivo microscopy of islet cytoarchitecture, function and viability in the physiological context and intravital imaging of a variety of pathological events such as autoimmune insulitis, defects in β cell function and mass and insulin resistance during diabetes development in a real-time manner. Furthermore, application of the ACE technology in humanized mice and non-human primates verifies translational and clinical values of the technology. In this article, we describe the ACE technology in detail, review accumulated knowledge gained by means of the ACE technology and delineate prospective avenues for the ACE technology.
Topics: Animals; Anterior Chamber; Biomedical Research; Diabetes Mellitus; Humans; Islets of Langerhans Transplantation
PubMed: 30677477
DOI: 10.1016/j.pharmthera.2019.01.005 -
Translational Vision Science &... May 2021The purpose of this study was to develop a software package for the automatic classification of anterior chamber angle using anterior segment optical coherence...
PURPOSE
The purpose of this study was to develop a software package for the automatic classification of anterior chamber angle using anterior segment optical coherence tomography (AS-OCT).
METHODS
AS-OCT images were collected from subjects with open, narrow, and closure anterior chamber angles, which were graded based on ultrasound biomicroscopy (UBM) results. The Inception version 3 network and the transfer learning technique were applied in the design of an algorithm for anterior chamber angle classification. The classification performance was evaluated by fivefold cross-validation and on an independent test dataset.
RESULTS
The proposed algorithm reached a sensitivity of 0.999 and specificity of 1.000 in the judgment of closed and nonclosed angles. The overall classification of the proposed method in open angle, narrow angle, and angle-closure classifications reached a sensitivity of 0.989 and specificity of 0.995. Additionally, the sensitivity and specificity reached 1.000 and 1.000 for angle-closure, 0.983 and 0.993 for narrow angle, and 0.985 and 0.991 for open angle.
CONCLUSIONS
The experimental results showed that the proposed method can achieve a high accuracy of anterior chamber angle classification using AS-OCT images, and could be of value in future practice.
TRANSLATIONAL RELEVANCE
The proposed deep learning-based method that automate the classification of anterior chamber angle can facilitate clinical assessment of glaucoma.
Topics: Anterior Chamber; Anterior Eye Segment; Deep Learning; Glaucoma, Angle-Closure; Gonioscopy; Humans; Malocclusion; Tomography, Optical Coherence
PubMed: 34111263
DOI: 10.1167/tvst.10.6.19