Ultrasound biomicroscopy. III. Accuracy and agreement of measurements

Evaluation of ciliary cleft changes after phacoemulsification using ultrasound biomicroscopy in dogs with cataracts

Introduction

Glaucoma is one of the most serious complications that causes irreversible blindness after phacoemulsification in dogs; however, a clear mechanism has not been elucidated. This study aimed to analyse the possible anatomical factors associated with glaucoma after phacoemulsification using parameters that reflect the anatomical characteristics of dogs.

Materials and methods

A total of 69 eyes of 48 dogs were included in this study. The patients were divided into three groups: normal eye (n = 18), cataract (n = 39), and post-phacoemulsification for at least 2 months after surgery (post-phaco, n = 12). For further analysis, the dogs were subdivided into two groups according to cataract stage: phacoemulsification non-candidate and candidate groups. Non-cataracts and incipient cataracts were categorized into the non-candidate group, whereas immature and mature cataracts were categorized into the candidate group. Measurements of the ciliary cleft parameters, including the area of the ciliary cleft (CCA), length of the ciliary cleft (CCL), width of the ciliary cleft (CCW), iridocorneal angle, and angle opening distance, were obtained using ultrasound biomicroscopy.

Results

CCA, CCL, and CCW were significantly higher in the candidate group than in the non-candidate group. CCA, CCL, and CCW were significantly reduced in the post-phaco group compared to those in the cataract group. Based on these results, we found that the ciliary cleft expanded in cataract-affected eyes and narrowed after phacoemulsification. This may indicate that the space between the trabecular meshworks became narrower, potentially leading to an increase in the resistance of the aqueous humor.

Conclusion

A narrowed ciliary cleft after phacoemulsification may be an anatomical factor associated with glaucoma.

Biometric assessment of pseudophakic subjects during objective accommodative stimulation: a prospective observational study

Clinical relevance: Ultrasound biomicroscopy is an objective method for assessing changes in anterior segment biometry. There is a paucity of data on the reliability of this method. A reliable method for assessing anterior segment changes during physiologically driven accommodation can be a useful tool for clinicians, researchers, and industry.Background: To assess the test-retest reliability of ultrasound biomicroscopy for measurements of change in anterior chamber depth during a distance to near fixation task in pseudophakic subjects.Methods: Subjects were adults with monofocal intraocular lenses implanted in both eyes who completed a 6-month post-operative period and had monocular uncorrected distance visual acuity of 6/15 (0.4 logMAR) or better. The change in anterior chamber depth during a distance to near fixation task was measured with a 35-MHz VuMAX HD ultrasound biomicroscopy device (Sonomed Escalon, New Hyde Park, NY) during two separate visits. An asymmetrical vergence paradigm allowed evaluation of anterior segment biometry at 22-µm axial resolution in one eye, while the fellow eye fixated on the target. To assess the test-retest reliability, 2-sided 95% CI from a paired t test was calculated for the difference in anterior chamber depth change from distance to near between visits.Results: The mean (standard deviation) near-focused anterior chamber depth measured by ultrasound biomicroscopy was 4.331 (0.237) and 4.333 (0.241) mm at visits 1 and 2, respectively. In response to a change in fixation from distance (4 m) to near (40 cm), the mean anterior chamber depth change was -0.012 (0.038) and 0.003 (0.039) mm at visits 1 and 2, respectively. Analysis of the difference in the change in anterior chamber depth between visits was -0.015 mm (95% CI, -0.035 to 0.003).Conclusion: Ultrasound biomicroscopy is a repeatable, objective method for assessing change in anterior segment biometry during physiological changes in fixation from distance to near.

Anterior ophthalmic imaging

Improvements in imaging chips and computer processing power have brought major advances in imaging of the anterior eye. Digitally captured images can be visualised immediately and can be stored and retrieved easily. Anterior ocular imaging techniques using slitlamp biomicroscopy, corneal topography, confocal microscopy, optical coherence tomography (OCT), ultrasonic biomicroscopy, computerised tomography (CT) and magnetic resonance imaging (MRI) are reviewed. Conventional photographic imaging can be used to quantify corneal topography, corneal thickness and transparency, anterior chamber depth and lateral angle and crystalline lens position, curvature, thickness and transparency. Additionally, the effects of tumours, foreign bodies and trauma can be localised, the corneal layers can be examined and the tear film thickness assessed.

Clinical Features of Iris Cysts in Long-Term Follow-Up

This study evaluated the characteristics and clinical course of patients with iris cysts in the long-term follow-up (24–48 months). We retrospectively analyzed the medical records of 39 patients with iris cysts (27 women and 12 men). Age, visual acuity, intraocular pressure (IOP), slit-lamp evaluation, and ultrasound biomicroscopy images were assessed. The mean age at diagnosis was 40.6 ± 17.48 years. Thirty (76.9%) cysts were peripheral, five (12.8%) were located at the pupillary margin, two (5.1%) were midzonal, and two (5.1%) were multichamber cysts extending from the periphery to the pupillary margin. A total of 23 (59%) cysts were in the lower temporal quadrant, 11 (28.2%) were in the lower nasal quadrant, and 5 (12.8%) were in the upper nasal quadrant. Cyst size was positively correlated with patient age (rs = 0.38, p = 0.003) and negatively correlated with visual acuity (rs = −0.42, p = 0.014). Cyst growth was not observed. The only complication was an increase in IOP in three (7.7%) patients with multiple cysts. The anatomical location of the cysts cannot differentiate them from solid tumors. The vast majority of cysts are asymptomatic, do not increase in size, and do not require treatment during long-term follow-up.

The Effectiveness of Ultrasound Biomicroscopic and Anterior Segment Optical Coherence Tomography in the Assessment of Anterior Segment Tumors: Long-Term Follow-Up

Background

Differential diagnosis and follow-up of small anterior segment tumors constitute a particular challenge because they determine further treatment procedures. The aim of this study was to evaluate the efficacy of the UBM (ultrasound biomicroscopy) and AS-OCT (anterior segment optical coherent tomography) in distinguishing different types of anterior segment lesions.

Methods

It was a retrospective, noncomparative study of case series of 89 patients with the suspicion of anterior segment tumor referred to the Ophthalmology Clinic, Medical University of Białystok, Poland, between 2016 and 2020. UBM was used to assess tumor morphology including height, location, and internal and external features. In cases in which UBM did not provide enough data, the AS-OCT images were analyzed. The data on demographics, best corrected visual acuity (BCVA), intraocular pressure (IOP), and rate of complications were also collected. Patients were followed up from 1 to 48 months.

Results

The mean observation period was 26.61 ± 16.13 months. Among the patients, there were 62 women and 27 men at a mean age of 55.59 ± 19.48 (range: from 20 to 89 years.) The types of tumors were cysts (41%), solid iris tumors (37.1%), ciliary body tumors (7.9%), peripheral anterior synechiae (PAS 3.4%), corneal tumors (4.5%), and others (5.6%). Patients with cysts were younger than patients with solid iris tumor (p=0.002). Women had a cyst as well as solid iris tumor more frequently than men, but less often a ciliary body tumor (p < 0.05). The horizontal size of tumor was positively correlated with patients' age (r_s = 0.38 and p=0.003) and negatively correlated with visual acuity (r_s = −0.42 and p=0.014). During the 4 years of diagnosis, only 2.2% of lesions exhibited growth (growth rate of 0.02 mm per year). Among 15 cases in which visualization with UBM was not satisfactory (mostly iris nevi), AS-OCT was helpful in diagnosis of 13 patients.

Conclusions

Both UBM and AS-OCT are effective methods in detection and diagnosis of tumors of the anterior eye segment, but in some cases, AS-OCT adds additional value to the diagnosis. Many lesions can be managed conservatively because they did not demonstrate growth during 4 years of the follow-up period.

Assessment of Anterior Segment Changes in Pseudophakic Eyes, Using Ultrasonic Biomicroscopic Imaging, after Pars Plana Vitrectomy with Silicone Oil or Gas Tamponade

Objective. To evaluate the morphological changes of the anterior segment using ultrasonic biomicroscopy (UBM) imaging in pseudophakic patients who underwent pars plana vitrectomy (PPV) with silicone oil or gas (C₃F₈) internal tamponade agent injection. Method. This prospective study included pseudophakic patients with planned PPV, divided into two groups according to internal tamponade agent: those in which silicone oil was used (n = 27, Group 1) and those in which gas (C₃F₈) was used (n = 24, Group 2). UBM measurements were performed in the supine position before and one week after surgery. Results. In patients of Group 1, postoperative trabecular meshwork-ciliary process distance (T-CPD) and iris-ciliary process distance (I-CPD), according to preoperative values, were found to be statistically significantly reduced, and postoperative mean value of scleral thickness (ST) and intraocular pressure (IOP), according to preoperative value, was found to be statistically significantly increased. In patients of Group 2, postoperative mean values of anterior chamber depth (ACD), ciliary body thickness (CBT), T-CPD, I-CPD, and IOP, according to preoperative values, were found to be statistically significantly reduced. Preoperatively, in Group 2 patients, according to Group 1 patients, TIA and IOP were found to be statistically significantly increased. Preoperative and postoperative IOP between the measured parameters with UBM showed no statistically significant correlation. Conclusions. Gases cause more morphological changes in the anterior segment structures. It is thought that complications such as increased intraocular pressure can be seen more frequently for this reason.

Assessment of central corneal thickness and corneal endothelial morphology using ultrasound pachymetry, non-contact specular microscopy, and Confoscan 4 confocal microscopy

BACKGROUND

The aim was to compare the repeatability, reproducibility and inherent precision of ultrasound pachymetry (USP), noncontact specular microscopy (SP-2000P) and the Confoscan 4 confocal microscope (z-ring CS4) in measuring endothelial cell density (ECD), coefficient of variation of cell size (CV), and central corneal thickness (CCT) in normal eyes.

METHODS

In this prospective study, one eye was selected from each of 30 subjects for the measurements of ECD, CV and CCT, which were taken by two observers. Results were analyzed statistically by repeated-measures analysis of variance (ANOVA) for intra-observer repeatability, inter-observer reproducibility, unpaired t-test, paired t-test, and Bland-Altman analyses to determine limits of agreement (LOA) between the three instruments.

RESULTS

Mean ECD, measured by SP-2000P and z-ring CS4, were 3115.50 ± 279.70 cells/mm(2) and 3167.50 ± 264.75 cells/mm(2), respectively (observer 1), and 3192.63 ± 249.42 cells/mm(2) (z-ring, observer 2). Mean CV measurements were 27.12 ± 2.51 and 27.10 ± 2.41 (SP-2000P and z-ring CS4, respectively; observer 1), and 27.17 ± 2.25 (z-ring, observer 2). Mean CCT values were 555.11 ± 35.83 μm (USP), 535.82 ± 41.10 μm (SP-2000P) and 552.57 ± 36.83 μm (z-ring CS4), and 554.97 ± 36.34 μm (z-ring CS4, observer 2). However, pairwise tests in all cases there was good repeatability and reproducibility as shown by inter-observer and intra-observer analysis of variance for each of the instruments.

CONCLUSIONS

The SP-2000P and the z-ring CS4 can be used interchangeably to measure ECD and CV. For CCT, the sample size was too small to test for differences of the CCT measurements between the three instruments.

Keeping an eye on decellularized corneas: a review of methods, characterization and applications

The worldwide limited availability of suitable corneal donor tissue has led to the development of alternatives, including keratoprostheses (Kpros) and tissue engineered (TE) constructs. Despite advances in bioscaffold design, there is yet to be a corneal equivalent that effectively mimics both the native tissue ultrastructure and biomechanical properties. Human decellularized corneas (DCs) could offer a safe, sustainable source of corneal tissue, increasing the donor pool and potentially reducing the risk of immune rejection after corneal graft surgery. Appropriate, human-specific, decellularization techniques and high-resolution, non-destructive analysis systems are required to ensure reproducible outputs can be achieved. If robust treatment and characterization processes can be developed, DCs could offer a supplement to the donor corneal pool, alongside superior cell culture systems for pharmacology, toxicology and drug discovery studies.

Comparison of central corneal thickness measurements using ultrasound pachymetry, ultrasound biomicroscopy, and the Artemis-2 VHF scanner in normal eyes

Purpose

To compare the precision of central corneal thickness (CCT) measurements taken with the handheld ultrasound pachymeter (USP), ultrasound biomicroscopy (UBM), and the Artemis-2 very high frequency ultrasound scanner (VHFUS) on normal subjects.

Design

Prospective study.

Methods

One eye from each of 61 normal subjects was randomly selected for this study. The measurements of the CCT were taken with the USP, VHFUS, and UBM. Results were compared statistically using repeated-measures analysis of variance (ANOVA), Pearson’s correlation coefficient, and limits of agreement.

Results

The average CCT (± standard deviation) was 530.1 ± 30.5 μm, 554.9 ± 31.7 μm, and 559.5 ± 30.7 μm for UBM, VHFUS, and USP respectively. The intraobserver repeatability analyses of variance are not significant for USP, UBM, and VHFUS. P-values were 0.17, 0.19, and 0.37 respectively. Repeated-measures ANOVA showed a significant difference between the three different methods of measuring CCT (P = 0.0001). The ANOVA test revealed no statistically significant difference between USP and VHFUS (P > 0.05), yet statistical significant differences with UBM versus USP and UBM versus VHFUS (P < 0.001). There were high correlations between the three instruments (P < 0.0001). The mean differences (and upper/lower limits of agreement) for CCT measurements were 29.4 ± 14.3 (2.7/56), 4.6 ± 8.6 (−14.7/23.8), and −24.8 ± 13.1 (−50.4/0.8) for USP versus UBM, USP versus VHFUS, and UBM versus VHFUS, respectively.

Conclusion

The UBM produces CCT measurements that vary significantly from those returned by the USP and the VHFUS, suggesting that the UBM may not be used interchangeably with either equipment for monitoring the CCT in the clinical setting.

Ultrasound biomicroscopic study of the stability of intraocular lens implants after phacoemulsification cataract surgery

PURPOSE

To assess the postoperative stability of three-piece intraocular lens (IOL) implants using ultrasound biomicroscopy (UBM).

METHODS

This is a prospective observational cohort case series. Best-corrected visual acuity (BCVA) assessment, slit lamp examination, refraction and UBM evaluation were performed preoperatively and at 1, 6, 12, 18 and 24 months postoperatively. The anterior chamber depth (ACD) and IOL tilt angles at the 12, 6, 3 and 9 o'clock meridians were assessed.

RESULTS

Twenty-one consecutive adult patients (21 study eyes) were recruited, but two dropped out from the study. The average age during cataract surgery was 71.7 years (60-83, SD 6.0). There were very slight changes in the refraction and IOL stability characteristics at all the postoperative follow-up time points. These were not found to be statistically significant, apart from the increase in ACD from months one (3.85 ± SD 0.29) to six (3.91 ± SD 0.26) (p = 0.01, paired t-test).

CONCLUSION

There was a small but statistically significant increase in ACD between the first and sixth postoperative month, but ACD remained stable thereafter. This was not associated with any significant changes in refraction or BCVA. In contrast, IOL optic tilt remained statistically unchanged throughout the 24-month study duration.

Effects of corneal thickness on intraocular pressure measured with three different tonometers

PURPOSE

To compare intraocular pressure (IOP) measured by a Goldmann applanation tonometer (GAT), a noncontact tonometer (NCT), and a portable noncontact tonometer (PNCT) in eyes of healthy volunteers, and to determine if a significant correlation exists between the IOP and the central corneal thickness (CCT).

METHODS

A total of 144 healthy participants were randomly assigned to one of two groups; in the first group, IOP was measured first with the NCT and then with the GAT. In the second group, IOP was measured first with the PNCT and then with the GAT. Subsequently, the CCT of all subjects was measured with an ultrasonic pachymeter.

RESULTS

The IOPs determined by the GAT and NCT and were strongly correlated, as were those determined by the GAT and PNCT, in both groups. However, a Bland-Altman plot showed that the correlations between the GAT and NCT and between the GAT and the PNCT measurements were not significant. With all three instruments, the IOP readings varied with the CCT. The mean IOPs obtained with the GAT increased by 0.23 mmHg with each 10-microm increase in CCT (0.23 mmHg/10 microm). The comparable value for the NCT was 0.29 mmHg/10 microm, and that for the PNCT was 0.31 mmHg/10 microm.

CONCLUSIONS

For measurements of IOP in normal eyes, the GAT is the tonometer least affected by the CCT, compared with the PNCT and NCT. A PNCT is more likely to be affected by variations in CCT than the GAT.

Quantitative ultrasound method to detect and monitor laser-induced cavitation bubbles

An ultrasound technique to measure the spatial and temporal behavior of the laser-induced cavitation bubble is introduced. The cavitation bubbles were formed in water and in gels using a nanosecond pulsed Nd:YAG laser operating at 532 nm. A focused, single-element, 25-MHz ultrasound transducer was employed both to detect the acoustic emission generated by plasma expansion and to acoustically probe the bubble at different stages of its evolution. The arrival time of the passive acoustic emission was used to estimate the location of the cavitation bubble's origin and the time of flight of the ultrasound pulse-echo signal was used to define its spatial extent. The results of ultrasound estimations of the bubble size were compared and found to be in agreement with both the direct optical measurements of the stationary bubble and the theoretical estimates of bubble dynamics derived from the well-known Rayleigh model of a cavity collapse. The results of this study indicate that the proposed quantitative ultrasound technique, capable of detecting and accurately measuring laser-induced cavitation bubbles in water and in a tissue-like medium, could be used in various biomedical and clinical applications.

Functional Assessment of Two Different Accommodative Intraocular Lenses Compared with a Monofocal Intraocular Lens

PURPOSE

To evaluate selected functional and physical properties of 2 models of accommodative intraocular lenses (IOLs) compared with those of a standard monofocal IOL.

DESIGN

Prospective randomized comparative trial.

PARTICIPANTS

Subjects were divided into 3 groups. In group 1, 30 eyes (19 subjects) received 1CU IOL implantation; in group 2, 29 eyes (19 subjects) received AT-45 IOL implantation; and in group 3, 21 eyes (21 subjects) were implanted with a monofocal IOL as a control.

INTERVENTION

Cataract surgery with implantation of the 1CU and AT-45 accommodative IOL models in the study groups, and the ACR6D monofocal IOL in the control group.

MAIN OUTCOME MEASURES

Far and near distance visual parameters were assessed at 1, 6, and 12 months after surgery in the accommodative IOL groups, and at 1 and 12 months in the control group. Anterior segment anatomy was investigated by ultrasound biomicroscopy, with and without visual accommodative stimulation.

RESULTS

The accommodative IOL groups significantly differed from the controls in terms of lower near-distance refractive addition (NDRA) and better distance-corrected near visual acuity (DCNVA), with P<0.001 at 1 year. The anterior IOL displacement during accommodation (DeltaACD) was significantly larger in the study groups, and this correlated with DCNVA. Until 6 months, the DeltaACD correlated with the solicited sclerociliary process rotation only in the study groups.

CONCLUSION

This 12-month study demonstrated that the accommodating IOLs achieved better clinical results than the monofocal IOL in terms of DCNVA and NDRA. These results support the hypothesis that accommodative IOLs proportionally react to ciliary body rotation, although this relationship became less evident at 12 months.

Anterior capsule cover and axial movement of intraocular lens

PURPOSE

To measure optic shift (OS) of a single piece monofocal intraocular lens (IOL) with varying relationships between anterior capsule cover and IOL optic.

METHODS

This is a prospective randomized masked study of 150 eyes undergoing phacoemulsification. Eyes received either option: 360 degrees total capsule cover (group I); partial cover (group II); or no cover (group III). OS was calculated as difference in anterior chamber depth after administration of cyclopentolate 1% and pilocarpine 2% on IOLMaster at separate visits at 6 months follow-up. Subsequently, using retro-illumination photographs, percentage area of capsule cover was calculated. OS within and between groups I and II was analyzed. The impact of one quartile change in area of capsule cover on percentage change in OS was measured for both groups. Unpaired t-test, correlation, and regression were applied.

RESULTS

In groups I, II, and III, mean age of patients was 56.68+/-6.38, 57.09+/-7.34, 59.15+/-6.35 years, respectively; mean OS (mm) was 1.25+/-0.28, 1.20+/-0.24; 0.95+/-0.26 (P=0.013), respectively; and percentage area of capsule cover (%) was 47.35+/-10.48, 33.83+/-10.11, 0.16+/-0.13 (P=0.001), respectively. Mean percentage area of capsule cover in group I vsgroup II was significant (P=0.001). OS was 1.22+/-0.26 mm in groups I and II (combined) vs0.95+/-0.26 mm in group III (P=0.004, (0.06, 0.33)). OS in group I vsgroup II was not significant (P=0.46). Correlation coefficient was r=0.38 (P<0.001). With every increment on quartile (a quartile is any of the three values which divide the sorted data set into four equal parts, so that each part represents one-fourth of the sample or population) class of area of capsule cover the OS increased by 0.12 mm.

CONCLUSION

The OS differed significantly between total and partial cover groups combined vsno cover group.

[Ultrasound biomicroscopy of posterior chamber phakic intraocular lenses: a comparative study between ICL and PRL models]

PURPOSE

To evaluate the anatomic relationships of the implantable contact lens (ICL) and the phakic refractive lens (PRL) posterior chamber phakic intraocular lenses (PCP IOL) using ultrasound biomicroscopy (UBM).

MATERIAL AND METHODS

Seventeen phakic myopic eyes corrected with ICL, and 14 phakic myopic eyes that had had PRL implantation, were examined retrospectively using UBM. The main parameters measured and compared were anterior chamber depth, central and peripheral distance between PCP IOL and the crystalline lens, and exact lens haptic position.

RESULTS

The mean distance between the PCP IOL and the central endothelium was 2398+/-203 microm and 2640+/-230 microm in the ICL and PRL groups, respectively. The central vault between the implant and the crystalline lens was greater in eyes with ICL (ICL, 402+/-194 microm; PRL, 256+/-187 microm, p<0.05). However, the incidence of lens contact on the peripheral level was higher in the ICL group (41%) than in the PRL group (29%), and the difference between the two implants in the peripheral crystalline lens-PCP IOL distance was significant (p<0.05). Both IOL haptics appeared to be correctly positioned in the sulcus in 13 (76%) eyes of the ICL group, and on the zonule in eight eyes (57%) of the PRL group.

CONCLUSIONS

PCP IOL implantation is a safe procedure for the correction of high myopia with regard to refractive results. UBM provides a unique tool to noninvasively evaluate the relations of these implants within the posterior chamber, and helps to analyze the mechanisms of crystalline lens and iris complications.

Gender Variation in Ocular Biometry and Ultrasound Biomicroscopy of Primary Angle Closure Suspects and Normal Eyes

PURPOSE

To compare A-scan biometry and ultrasound biomicroscopy of primary angle closure suspects (PACS) with age-matched normal Indian eyes.

PATIENTS AND METHODS

Subjects with primary angle closure suspects (n=57 eyes) and normal eyes (n=57 eyes) underwent A-scan biometry and ultrasound biomicroscopy. Anterior chamber depth (ACD), anterior chamber angle (ACA), axial length (AXL), lens thickness, relative lens position (RLP), central corneal thickness (CCT), angle opening distance 500, trabecular-ciliary process distance (TCPD), iris-ciliary process distance, iris thickness, and scleral-ciliary process angle were measured. The subjects were divided into males, females, and combined groups for analysis. The parameters were compared using independent sample t test with Bonferroni correction for multiple comparisons.

RESULTS

In the combined group, the PACS subjects presented a significantly low ACD, AXL, CCT, AOD500, TCPD, ACA (P<0.001), and RLP (P=0.04). In males, RLP was anterior (P=0.002) and in females, the lens thickness (P<0.001) was significantly thicker among the PACS group.

CONCLUSIONS

ACD, AXL, CCT, TCPD, ACA, and angle opening distance 500 of the PACS group were significantly lower than in normals. In females, the lens in PACS was thicker than in normals. Lens in males was more anterior-placed in PACS group than in normals.

Evaluation of intra- and interobserver reliability and image reproducibility to assess usefulness of high-resolution ultrasonography for measurement of anterior segment structures of canine eyes

OBJECTIVE

To evaluate the usefulness of high-resolution ultrasonography (HRUS) for measurements of anterior segment structures in canine eyes.

ANIMALS

4 clinically normal Beagles.

PROCEDURE

Images were obtained from 8 eyes with a handheld 20-MHz transducer. Eleven anterior segment structures on each image were measured 5 times by 2 independent observers. Coefficients of variation (CVs) for measurements were used to assess intraobserver reliability. Interobserver reliability was assessed by comparing measurements obtained by the 2 observers from the same images. Five images were sequentially obtained from 2 locations (ie, superior and temporal) to evaluate image reproducibility. Anterior segment structures were measured once on each image; image reproducibility was assessed by use of the CV for each parameter measured. Imaging location was assessed by comparison of CV for measurements from each location.

RESULTS

CVs were < 10% for observer A for all measurements except the ciliary cleft area (11.63%). The CVs were > 10% for observer B for measurements of the angle recess area (18.51%) and ciliary cleft width (17.44%) and area (16.01%). Significant differences in measurements between observers were found for 5 of 11 anterior segment structures. Imaging the superior aspect of the globe provided the most reproducible images, although image reproducibility was still somewhat variable, with the highest and lowest CVs for measurements of 33.01% and 11.32%, respectively, in the superior position.

CONCLUSIONS AND CLINICAL RELEVANCE

High-resolution ultrasound images can be used to reliably measure various anterior segment structures. Clinically relevant findings in the anterior segment of canine eyes may be detectable by use of HRUS.

Drug-induced intraocular lens movement and near visual acuity after AcrySof intraocular lens implantation

PURPOSE

To evaluate the factors influencing AcrySof intraocular lens (IOL) (Alcon Laboratories) movement and near visual acuity after cyclopentolate 1% and pilocarpine 2%.

SETTING

Department of Ophthalmology, University of Ankara, Ankara, Turkey.

METHODS

Thirty eyes of 22 patients with AcrySof IOL implantation were included in this prospective study. Near visual acuity (Jaeger) at 35 cm through best distance correction without an add and pupil diameter were measured and correlated with anterior chamber depth (ACD) measured with ultrasound biomicroscopy (UBM) after application of cyclopentolate 1% and pilocarpine 2%, respectively. The magnitude of the change in the ACD was correlated with the accommodation amplitude, patient age, time interval between surgery and imaging, preoperative axial length, capsulorhexis diameter, ACD during cycloplegia, IOL diameter, and presence of posterior capsule opacification (PCO).

RESULTS

Near visual acuity significantly decreased after application of cyclopentolate 1% and increased after application of pilocarpine 2% (P < .001) in all eyes. The IOL moved anteriorly in 8 (26%) eyes and posteriorly in 22 (74%) eyes after pilocarpine 2%. There was no correlation between the ACD and near visual acuity under cyclopentolate 1% (r = 0.06, P > .05) or pilocarpine 2% (r = 0.04, P > .05). There was a moderate correlation between the anterior IOL movement and accommodation amplitude (P < .05, r = 0.42). There was no correlation between the magnitude of the IOL movement and patient age, time interval between surgery and imaging, the preoperative axial length, capsulorhexis diameter, ACD during cycloplegia, IOL diameter, and the presence of PCO (P > .05).

CONCLUSIONS

There was better near visual acuity in all eyes with the AcrySof MAIOL, although most IOLs move slightly backward after of pilocarpine 2%. This points out pseudoaccommodation rather than pseudophakic accommodation. Ultrasound biomicroscopy is useful in determining the ACD and the relation between the IOL and the surrounding tissues after cataract surgery.

Anterior segment imaging: ultrasound biomicroscopy

Ultrasound biomicroscopy technology has become an indispensable tool in qualitative and quantitative assessment of the anterior segment. Advances in soft-ware design and algorithms will improve theoretical understanding of the pathophysiology of anterior segment disorders. Future applications of quantitative techniques will yield important information regarding mechanisms of angle closure, improving understanding of the dynamic functions of the iris,accommodation, presbyopia, and other aspects of anterior segment physiology and pathophysiology.

Ultrasound biomicroscopy of silicone posterior chamber phakic intraocular lens for myopia

PURPOSE

To study the intraocular position and anatomic relationships of PRL-III (phakic refractive lens) (PRL) posterior chamber phakic intraocular lens (PCP IOL) for high myopia using ultrasound biomicroscopy (UBM).

SETTING

Centro Oftalmológico Real Vision, and Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Universidad Complutense de Madrid, Madrid, Spain.

METHODS

Sixteen phakic myopic eyes that had had PRL implantation were examined by UBM 1 month after surgery. The PRL position, PRL-crystalline lens peripheral distance, and central distance between the corneal endothelium and the PRL were measured.

RESULTS

Both haptics were on the zonule in 6 eyes, in the ciliary sulcus in 5 eyes, and impacted in the ciliary body in 1 eye. In the 4 remaining eyes, the haptics were in mixed positions. The mean PCP IOL crystalline lens peripheral distance in the minor axis was 588.1 microm +/- 232.5 (SD), and the mean PCP IOL-endothelium central distance was 2082.8 +/- 277.6 microm.

CONCLUSIONS

Phakic refractive lens implantation should be done carefully because of the sulcus location of the haptics in many cases. This, with the iris-PRL contact, suggests caution for the long-term outcome.

Comparison of central corneal thickness measurements by specular microscopy, ultrasound pachymetry, and ultrasound biomicroscopy

PURPOSE

To compare the reproducibility and mean values of central corneal thickness (CCT) obtained by specular microscopy, ultrasound pachymetry, and ultrasound biomicroscopy (UBM).

SETTING

Department of Ophthalmology, University of Toronto, Toronto, Ontario, Canada.

METHODS

Thirty-one healthy volunteers were recruited for a sample size of 62 eyes. All subjects had pachymetric measurements by specular microscopy, ultrasound pachymetry, and UBM. Three separate measurements meeting criteria for centrality and perpendicularity were recorded for each eye.

RESULTS

The mean CCT by specular microscopy was 572 microm (95% confidence interval (CI), 566-578 microm), which was significantly greater than 550 microm (95% CI, 545-556 microm) (P<.001) and 555 microm (95% CI, 550-560 microm) (P<.001) by ultrasound pachymetry and UBM, respectively. The mean standard deviation (SD) of repeated measurements by specular microscopy was 7.82 microm, which was significantly greater than the mean SDs of 4.14 microm (P<.001) and 3.90 microm (P<.001) by ultrasound pachymetry and UBM, respectively. There was no statistically significant difference between the mean SDs by ultrasound pachymetry and UBM (P=.156).

CONCLUSIONS

Although the CCT measurements by specular microscopy were significantly less reproducible than those by ultrasound pachymetry and UBM, the error levels were clinically acceptable. Both ultrasound pachymetry and UBM produced similar CCT measurements, which were significantly less than those generated by specular microscopy. One should be aware of the advantages and limitations of each machine and of possible differences in the CCT measurements by optical and ultrasound pachymetry.

Reliability of Corneal Thickness and Endothelial Cell Density Measures

PURPOSE

We evaluated the reliability and agreement between the Orbscan, an ultrasonic pachymeter (Humphrey 855), and the Konan SP 9000-LC in terms of central corneal thickness. The Konan was also used to study the reliability and agreement between endothelial cell density measures.

METHODS

Twenty-five normal subjects were examined on two occasions (mean separation = 9 +/- 5 days) by a single examiner using all three instruments for central corneal pachymetry. The Konan Center Method and a manual counting method were performed by two examiners to determine endothelial cell density. Reliability and agreement were assessed by calculating the 95% limits of agreement (LoA) and intraclass correlation coefficients (ICC).

RESULTS

For corneal pachymetry test-retest reliability, the 95% limits of agreement were -20 to +17 microm for the ultrasound, -27 to +22 microm for the Konan, and -13 to +13 microm for the Orbscan. There was fair-to-good agreement between the pachymeters (intraclass correlation coefficients range = 0.85 to 0.92). For endothelial cell density test-retest reliability, the 95% limits of agreement for the Konan Center Method was -498 to +530, and -482 to +333 cells/mm2 for examiners 1 and 2, respectively. The test-retest 95% limits of agreement for the manual overlaid grid method was -355 to +355, and -535 to +670 cells/mm2 for examiners 1 and 2, respectively.

CONCLUSIONS

The reliability and agreement of the Orbscan and Konan corneal pachymeters was good, although the reliability of the Konan for estimating endothelial cell density was fair, at best.

Ultrasound biomicroscopy examination of posterior chamber phakic intraocular lens position

OBJECTIVE

To better elucidate the in vivo position of the Collamer posterior chamber phakic intraocular lens (PCPIOL) and its relationship to the iris and the crystalline lens and to analyze possible variations over time.

DESIGN

Prospective observational case series.

PARTICIPANTS

Eighteen eyes of nine patients were included.

INTERVENTION

A Staar Collamer implantable PCPIOL was implanted for the correction of high myopia.

MAIN OUTCOME MEASURES

The eyes were studied with a 50-MHz ultrasound biomicroscopy UBM 840. The exact PCPIOL position and the distances between it and the crystalline lens were measured at 3, 6, and 12 months after surgery.

RESULTS

There were no intraoperative complications. In 13 eyes (72.22%), contact between the PCPIOL and the crystalline lens was found at some time during follow-up. In 3 eyes (16.6%), central contact could be demonstrated. We also observed that the contact zone and its extension can vary over time. In 2 eyes, rotation of the lens was observed.

CONCLUSIONS

We found contact between the PCPIOL and the crystalline lens in a high percentage of cases. There was also mobility of the lens in the posterior chamber, especially in the anteroposterior plane, and, as a consequence, both the contact zone and its extension would vary over time.

The efficacy of latanoprost is independent of the width of the ciliary body face

PURPOSE

To assess the relation between the intraocular pressure-lowering efficacy of latanoprost 0.005% and the area of the ciliary body face exposed to the anterior chamber as assessed by ultrasound biomicroscopy.

PATIENTS AND METHODS

Untreated, latanoprost-naive patients with ocular hypertension or open-angle glaucoma were enrolled in this prospective clinical trial. A radial, perpendicular ultrasound biomicroscopy image at the 6-o'clock position detailing Schwalbe line, scleral spur, and iris insertion was obtained. The distances between these structures were then measured and their relations to the intraocular pressure-lowering effect of latanoprost at 1, 2, 3, and 6 months were analyzed.

RESULTS

Fifty-four eyes (54 patients) were enrolled. The mean age of participants was 60.2 +/- 13.9 years, and mean pretreatment intraocular pressure was 26.4 +/- 3.8 mm Hg. The mean intraocular pressure reduction from baseline was 7.1 mm Hg (26.9%), 7.3 (27.7%), 7.8 (29.5%), and 7.7 (29.2%) at 1, 2, 3 and 6 months, respectively. The mean distance between the scleral spur and the iris insertion was 0.14 +/- 0.08 mm (range, 0.04-0.33 mm). There was a significant correlation between intraocular pressure reduction at 1 month and trabecular meshwork height, suggesting that intraocular pressure reduction was associated with increasing trabecular meshwork height (P < 0.05). No other correlation could be found regarding intraocular pressure reduction.

CONCLUSION

Although latanoprost lowers intraocular pressure by enhancing uveoscleral outflow, its efficacy is independent of the height of the ciliary face.

Ultrasound biomicroscopy of ZSAL-4 anterior chamber phakic intraocular lens for high myopia

PURPOSE

To evaluate the intraocular location and anatomic relationship to other structures of the ZSAL-4 angle-supported anterior chamber phakic intraocular lens (IOL) for high myopia using ultrasound biomicroscopy (UBM).

SETTING

Clínica de Nuestra Señora de la Concepción, Fundación Jiménez Díaz, and Instituto de Investigaciones Oftalmológicas Ramón Castroviejo, Madrid, Spain.

METHODS

Eight phakic myopic eyes corrected by ZSAL-4 angle-supported anterior chamber phakic IOLs were examined by UBM. The distance between the corneal endothelium and the IOL at the central and peripheral cornea and between the phakic IOL and the iris was measured.

RESULTS

The mean distance between the central cornea and the IOL was 2361.37 microm +/- 109.62 (SD); between the edge of the IOL optic and the endothelium, 1646.24 +/- 27.06 microm; and between the IOL and the iris, 354.46 +/- 41.61 microm. The IOL footplates appeared to be correctly positioned in the anterior chamber angle in all eyes.

CONCLUSION

The space between the IOL and the endothelium was greater in eyes with the ZSAL-4 angle-supported phakic IOL than in eyes with other angle-supported phakic IOLs. The possibility of intermittent contact between the IOL edge and the midperipheral cornea plays a minor role in the mechanism of endothelial damage with this lens model.

Quantitative assessment of the anterior segment using ultrasound biomicroscopy

The development of ocular imaging devices has progressed rapidly during the past 10 years. Ultrasound biomicroscopy has revolutionized the evaluation of the anterior segment of the eye. The qualitative information gathered using this technology has contributed to our understanding of the pathophysiology of angle-closure glaucoma, pigmentary glaucoma, and a variety of other anterior segment disorders. However, the area of quantitative analysis of ultrasound biomicroscopic images remains largely to be developed. This review describes the role of ultrasound biomicroscopy in the measurement of the anatomic structures and their configurations within the anterior segment. Included are previously published and established methods as well as methods in their early stages of development. Application of quantitative image analysis techniques should yield significant information about mechanisms of appositional angle closure, dynamic functions of the iris, accommodation, and presbyopia.

Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach

We determined the "normal" central corneal thickness (CCT) value in human corneas based on reported literature values for within-study average CCT values, and used this as a reference to assess the reported impact of physiological variables (especially age and diurnal effects), contact lens wear, pharmaceuticals, ocular disease, and ophthalmic surgery on CCT. With the expected CCT and its variance defined, it should be possible to determine the potential impact of differences in CCT in intraocular pressure (IOP) assessments, especially by applanation tonometry, using a meta-analysis approach. Some 600 sets of CCT data were identified from the worldwide literature over the period of 1968 through mid-1999, of which 134 included IOP measures as well. The within-study average CCT values and reported variance (SD) was noted along with the number of eyes and any special characteristics, including probable ethnic origin of the study subjects. Various sets of data were subjected to statistical analyses. From 300 data sets from eyes designated as normal, the group-averaged CCT was 0.534 mm. From 230 data sets where interindividual variance was reported, the group-averaged CCT was 0.536 mm (median 0.536 mm; average SD of 0. 031 mm, average coefficient of variation = 5.8%). Overall, studies using slit-lamp-based pachometry have reported marginally lower CCT values (average 0.530 mm, average SD 0.029 mm) compared to ultrasound-based studies (average 0.544, average SD 0.034 mm), which perhaps reflects the type of individual studied (non-surgical vs. pre-surgical patients) rather than the technique itself. A slight chronological increase in reported average CCT values (approximately 0.006 mm/decade) was evident, but a substantial chronological increase was evident for ultrasound pachometry studies (approximately 0.015 mm/decade). Within the meta-analysis-generated average and variance, age had no obvious impact on CCT measures for *whites, although an age-related decline in CCT is evident for non-whites. Any diurnal effects are likely concealed within the expected variance in CCT. Contact lens wear and pharmaceuticals generally produced changes in CCT that were well within the expected variance in CCT. Of the ocular diseases, only those associated with collagen disorders (including keratoconus) or endothelial-based corneal dystrophies (e.g., Fuchs) were likely to result in decreases or increases, respectively, of CCT beyond the normal variance. Routine contact lens wear and diseases such as diabetes seem unlikely to produce changes in CCT of a magnitude that would justify pachometry as a monitoring method beyond routine slit-lamp evaluation. Increases in CCT beyond the expected variance were reported after a range of intraocular surgeries (cataract operations, penetrating keratoplasty), whereas photorefractive surgery produces a measurable decrease in CCT. A meta-analysis of possible association between CCT and IOP measures of 133 data sets, regardless of the type of eyes assessed, revealed a statistically significant correlation; a 10% difference in CCT would result in a 3. 4 +/- 0.9 mm Hg difference in IOP (P </= 0.001, r = 0.419). The observed phenomenon was much smaller for eyes designated as healthy (1.1 +/- 0.6 mm Hg for a 10% difference in CCT, P = 0.023, r = 0. 331). For eyes with chronic diseases, the change was 2.5 +/- 1.1 mm Hg for a 10% difference in CCT (P = 0.005, r = 0.450), whereas a substantial but highly variable association was seen for eyes with acute onset disease (approximately 10.0 +/- 3.1 mm Hg for a 10% difference in CCT, P = 0.004, r = 0.623). Based on the meta-analysis, normal CCT in white adults would be expected to be within +/-11.6% (+/-2 SD) of 0.535 mm, i.e., 0.473-0.597 mm (95% CI, 0.474-0.596). The impact of CCT on applanation tonometry of healthy eyes is unlikely to achieve clinical significance, but for corneas of eyes with chronic disease, pachometry should be performed if the tonometry reveals IOP readi