Ultrasound biomicroscopic and conventional ultrasonographic study of ocular dimensions in primary angle-closure glaucoma

Effect of primary iris and ciliary body cyst on anterior chamber angle in patients with shallow anterior chamber

OBJECTIVE

To evaluate the prevalence of primary iris and/or ciliary body cysts in eyes with shallow anterior chamber and their effect on the narrowing of the anterior chamber angle.

METHODS

Among the general physical check-up population, subjects with shallow anterior chambers, as judged by van Herick technique, were recruited for further investigation. Ultrasound biomicroscope (UBM) was used to detect and measure the cysts located in the iris and/or ciliary body, the anterior chamber depth (ACD), the angle opening distance at 500 µm (AOD500), and the trabecular-iris angle (TIA). A-scan ultrasonography was used to measure the ocular biometry, including lens thickness, axial length, lens/axial length factor (LAF), and relative lens position (RLP). The effect of the cyst on narrowing the corresponding anterior chamber angle and the entire angle was evaluated by the UBM images, ocular biometry, and gonioscopic grading. The eye with unilateral cyst was compared with the eye without the cyst for further analysis.

RESULTS

Among the 727 subjects with shallow anterior chamber, primary iris and ciliary body cysts were detected in 250 (34.4%) patients; among them 96 (38.4%) patients showed unilateral single cyst, 21 (8.4%) patients had unilateral double cysts, and 42 (16.8%) patients manifested unilateral multiple and multi-quadrants cysts. Plateau iris configuration was found in 140 of 361 (38.8%) eyes with cysts. The mean size of total cysts was (0.6547 ± 0.2319) mm. In evaluation of the effect of the cyst size and location on narrowing the corresponding angle to their position, the proportion of the cysts causing corresponding angle narrowing or closure among the cysts larger than 0.8 mm (113/121, 93.4%) was found to be significantly higher than that of the cysts smaller than 0.8 mm (373/801, 46.6%), and a significant higher proportion was also found in the cysts located at iridociliary sulcus (354/437, 81.0%) than in that at the pars plicata (131/484, 27.1%). In evaluating the effect of the cyst on the entire anterior chamber angle, the eyes with multiple and multi-quadrants cysts manifested significant narrowing of the entire anterior chamber angle as compared with the eyes without cysts, based on the data analysis in comparison of TIA, AOD500, and gonioscopic grading evaluation. The unilateral single or double cysts in the eyes had no significant effect on narrowing of anterior chamber angle as compared with eyes without cysts. The iris and/or ciliary body cysts did not seem to affect the axial length, ACD, lens thickness, RLP, LAF.

CONCLUSIONS

The prevalence of primary iris and ciliary body cyst was 34.4% in the subjects with shallow anterior chamber. The cysts larger than 0.8 mm, locating at iridociliary sulcus, or multiple and extensive cysts were inclined to cause the angle narrowing or closure.

The role of anterior segment optical coherence tomography in glaucoma

The anterior segment optical coherence tomography provides an objective method to assess the anterior segment of the eye, including the anatomy of the anterior chamber angle. This technology allows both qualitative and quantitative analyses of the angle and has shown potential in detecting and managing angle-closure glaucoma. In addition, it has a role in identifying pathology in some forms of secondary open-angle glaucoma and postsurgical management of glaucoma. Limitations of this technology include its cost and inability to visualize well structures posterior to the iris, such as the ciliary body. This paper focuses on potential benefits and limitations of anterior segment optical coherence tomography when compared with conventional gonioscopy and ultrasound biomicroscopy. Various clinical entities will be described to discuss its potential role in glaucoma practice.

Increased iris-lens contact following spontaneous blinking: mathematical modeling

The purpose of this work was to study in silico how iris root rotation due to spontaneous blinking alters the iris contour. An axisymmetric finite-element model of the anterior segment was developed that included changes in the iris contour and the aqueous humor flow. The model geometry was based on average values of ocular dimensions. Blinking was modeled by rotating the iris root posteriorly and returning it back to the anterior. Simulations with maximum rotations of 2°, 4°, 6°, and 8° were performed. The iris-lens contact distance and the pressure difference between the posterior and anterior chambers were calculated. When the peak iris root rotation was 2°, the maximum iris-lens contact increased gradually from 0.28 to 0.34mm within eight blinks. When the iris root was rotated by 6° and 8°, the pressure difference between the posterior and anterior chambers dropped from a positive value (1.23Pa) to negative values (-0.86 and -1.93Pa) indicating the presence of reverse pupillary block. Apparent iris-lens contact increased with steady blinking, and the increase became more pronounced as posterior rotation increased. We conclude that repeated iris root rotation caused by blinking could maintain the iris in a posterior position under normal circumstances, which would then lead to the clinically observed anterior drift of the iris when blinking is prevented.

Rabbit models for continuous curvilinear capsulorhexis instruction

PURPOSE

To develop a rabbit model for continuous curvilinear capsulorhexis (CCC) instruction.

SETTING

University of California San Francisco, San Francisco, California, USA.

DESIGN

Experimental study.

METHODS

Isolated rabbit lenses were immersed in 2% to 8% paraformaldehyde (PFA) fixative from 15 minutes to 6 hours. Rabbit eyes were treated by substituting aqueous with 2% to 4% PFA for 30 minutes to 6 hours, followed by washes with a balanced salt solution. Treated lenses and eyes were held in purpose-designed holders using vacuum. A panel of 6 cataract surgeons with 5 to 15 years of experience performed CCC on treated lenses and eyes and responded to a questionnaire regarding the utility of these models for resident teaching using a 5-item Likert scale.

RESULTS

The expert panel found that rabbit lenses treated with increasing amounts of fixative simulated CCC on human lens capsules from the third to the seventh decade of life. The panel also found fixative-treated rabbit eyes to simulate some of the experience of CCC within the human anterior chamber but noted a shallower anterior chamber depth, variation in pupil size, and corneal clouding under some treatment conditions.

CONCLUSIONS

Experienced cataract surgeons who performed CCC on these rabbit models strongly agreed that isolated rabbit lenses treated with fixative provide a realistic simulation of CCC in human patients and that both models were useful tools for capsulorhexis instruction. Results indicate that rabbit lenses treated with 8% PFA for 15 minutes is a model with good fidelity for CCC training.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Anterior chamber configuration changes after cataract surgery in eyes with glaucoma

PURPOSE

To evaluate changes in anterior chamber depth (ACD) and angle width induced by phacoemulsification and intraocular lens (IOL) implantation in eyes with glaucoma, using anterior segment optical coherence tomography (AS-OCT).

METHODS

Eleven eyes of 11 patients with angle-closure glaucoma (ACG) and 12 eyes of 12 patients with open-angle glaucoma (OAG) underwent phacoemulsification and IOL implantation. Using AS-OCT, ACD and angle parameters were measured before and 2 days after surgery. Change in intraocular pressure (IOP) and number of ocular hypotensive drugs were evaluated.

RESULTS

After surgery, central ACD and angle parameters increased significantly in eyes with glaucoma (p < 0.05). Prior to surgery, mean central ACD in the ACG group was approximately 1.0 mm smaller than that in the OAG group (p < 0.001). Post surgery, mean ACD of the ACG group was still significantly smaller than that of the OAG group. No significant differences were found in angle parameters between the ACG and OAG groups. In the ACG group, postoperative IOP at the final visit was significantly lower than preoperative IOP (p = 0.018) and there was no significant change in the number of ocular hypotensive medications used, although clinically, patients required fewer medications. In the OAG group, the IOP and number of ocular hypotensive drugs were almost unchanged after surgery.

CONCLUSIONS

The ACD and angle width in eyes with glaucoma increased significantly after phacoemulsification and IOL implantation. Postoperative ACD significantly differed between the ACG and OAG groups, whereas angle parameters did not differ.

An ultrasound biomicroscopy study of filtering blebs after deep sclerectomy with a new acrylic implant

PURPOSE

To identify the clinical and anatomic characteristics of filtering blebs after nonpenetrating deep sclerectomy (NPDS) using ultrasound biomicroscopy, and to evaluate its influence on intraocular pressure (IOP) control.

METHODS

We conducted a prospective interventional case series in 18 eyes of 18 patients who had undergone nonpenetrating deep sclerectomy with Esnoper® implant. A complete ophthalmic examination and ultrasound biomicroscopy (UBM) exploration were performed at 1, 3, and 6 months postoperatively.

RESULTS

Intraocular pressure significantly decreased from a mean of 23.5 mmHg (SD 3.5) preoperatively to a mean of 13.1 mmHg (SD 7.6), 13.2 mmHg (SD 4.3), and 13.3 mmHg (SD 3) at 1, 3, and 6 months postoperatively, respectively. At 6 months, lower IOP levels significantly correlated with hyporeflective blebs (r=-0.82, p=0.000), with the presence of hyporeflective suprachoroidal space (r=-0.67, p=0.003) and with the presence of hyporeflective area around the scleral lake (r=-0.55, p=0.02). The presence of these 3 filtration signs together correlated with lower IOP levels compared with the presence of only 1 or 2 (p=0.000, p=0.004, p=0.0005) at 1, 3, and 6 months postoperatively, respectively. A thinner trabeculo-descemetic membrane (TDM) was significantly correlated with lower postoperative IOP value at the first postoperative month (r=0.45, p=0.05). Intraocular pressure mean values and UBM characteristics were not significantly different between eyes with single NPDS and eyes following combined NPDS-phacoemulsification. At 6 months, eyes without goniopuncture had lower IOP values (p=0.02), higher bleb (p=0.015), and thinner TDM (p=0.01) than those needing goniopuncture.

CONCLUSIONS

Ultrasound biomicroscopy is a useful method to evaluate outflow mechanisms after NPDS and their correlation with postoperative IOP control.

Pupil dynamics in Chinese subjects with angle closure

OBJECTIVE

To evaluate the speed of pupil constriction (SPC) in response to a standardized change in illumination from dark to light using anterior segment optical coherence tomography (AS-OCT) in eyes with closed angles, compared to those with open angles.

METHODS

This was a prospective, comparative, observational study. Study subjects with primary angle-closure glaucoma (PACG) and/or primary angle-closure (PAC) were recruited along with a group of normal as controls. Videos of iris and anterior segment changes in response to illumination were captured with real-time video recording from AS-OCT and analysed frame by frame, beginning from a dilated to a constricted pupil. Customized software was used to measure speed of iris constriction, anterior chamber depth (ACD), anterior chamber width (ACW), iris thickness, and pupil diameter (PD). SPC was defined as the rate of pupil diameter change in response to illumination.

RESULTS

One hundred and sixty three Chinese subjects were recruited in this study. A total of 137 of 163 eligible videos (82.5%) were available for analysis, comprising 87 subjects with closed angles (all had undergone laser peripheral iridotomies before) and 50 with open angles. SPC was less in eyes with closed angles (1.22 mm/sec vs 1.56 mm/sec, p<0.001), after adjusting for age and ACW, and was positively correlated with axial length, ACD, anterior chamber angle status, PD in the dark, and iris thickness in the dark, (all r>0.2, all p<0.05). In multivariate analysis, SPC was independently associated with anterior chamber angle status (closed angle vs open angle) (β=0.276, p=0.016) and PD in dark (β= 0.129, p=0.009), after adjusting for age, ACW, ACD, iris thickness and vertical cup-to-disc ratio.

CONCLUSIONS

Compared to those with open angles, eyes with closed angles in Chinese subjects have slower speed of pupil constriction in response to dark-light change, even after adjusting for biometric factors associated with angle closure. The results suggest that differences in irido-pupillary dynamics may play a role in the pathogenesis of angle closure.

Accuracy of intraocular lens power calculation formulas in primary angle closure glaucoma

Purpose

To compare the accuracy of intraocular lens (IOL) power calculation formulas in eyes with primary angle closure glaucoma (ACG).

Methods

This retrospective study compared the refractive outcomes of 63 eyes with primary ACG with the results of 93 eyes with normal open angles undergoing uneventful cataract surgery. Anterior segment biometry including anterior chamber depth, axial length, and anterior chamber depth to axial length ratio were compared by the IOL Master. Third generation formulas (Hoffer Q and SRK/T) and a fourth generation formula (Haigis) were used to predict IOL powers in both groups. The predictive accuracy of the formulas was analyzed by comparison of the mean error and the mean absolute error (MAE).

Results

In ACG patients, anterior chamber depth and the anterior chamber depth to axial length ratio were smaller than normal controls (all p < 0.05). The MAEs from the ACG group were larger than that from the control group in the Haigis formula. The mean absolute error from the Haigis formula was the largest and the mean absolute error from the Hoffer Q formula was the smallest.

Conclusions

IOL power prediction may be inaccurate in ACG patients. The Haigis formula produced more inaccurate results in ACG patients, and it is more appropriate to use the Hoffer Q formula to predict IOL powers in eyes with primary ACG.

Ultrasound biomicroscopic assessment of angle parameters in patients with primary angle closure glaucoma undergoing phacoemulsification

PURPOSE

To evaluate the effect of phacoemulsification and foldable intraocular lens (IOL) implantation on biometric determinants of the anterior chamber angle in primary angle closure glaucoma (PACG) using ultrasound biomicroscopy (UBM).

METHODS

Forty-six eyes of 46 patients with chronic PACG and cataract having a patent laser iridotomy were included in this prospective, interventional case series. Angle parameters were measured using UBM before surgery and 3 months after phacoemulsification with IOL implantation. Intraocular pressure (IOP) was measured by applanation tonometer and records of glaucoma medication administered were maintained. Main outcome measures were IOP, central anterior chamber depth (ACD), trabecular iris angle (TIA), and angle opening distance at 250 and 500 µm from scleral spur (AOD250 and AOD500).

RESULTS

The mean age of study participants was 56.5 ± 9.9 years (range 44-75). The preoperative mean IOP was 25.0 ± 5.4 mmHg on maximum antiglaucoma medication, which was reduced to 15.8 ± 3.8 mmHg (p = 0.0001) at 3 months. Number of antiglaucoma medications also decreased from 2.4 ± 1.1 to 0.4 ± 1.1 (p = 0.0001). There was a significant widening of the anterior chamber angle with the TIA increasing significantly after phacoemulsification (p<0.001) with an associated increase in AOD250, AOD500, and ACD (p<0.001).

CONCLUSIONS

Phacoemulsification in eyes with PACG results in significant widening of the anterior chamber angle. This results in better IOP control after surgery and decreases the need for glaucoma medications. These findings are of clinical significance in obviating the need for simultaneous filtering surgery in eyes with PACG undergoing phacoemulsification cataract surgery.

Bilateral simultaneous acute angle closure glaucoma precipitated by non-prescription cold and flu medication

We present a case of a 63-year-old woman who presented to an ED with bifrontal headache, nausea and vomiting and reduced visual acuity. Examination revealed bilateral elevated intraocular pressures, corneal haze, shallow anterior chambers and poorly reactive, mid-dilated pupils. Diagnosis was made of simultaneous bilateral acute angle closure glaucoma. A complete drug history revealed that she had been using an over-the-counter cold and flu remedy whose active ingredients included atropa belladonna, an herb with anticholinergic properties. It is likely that drug-induced dilatation of the individual's pupils precipitated this angle closure emergency. In the report we discuss the risk factors for angle closure glaucoma, and review the local and systemic drugs known to trigger this sight-threatening emergency.

Comparison of ultrasound biomicroscopic configurations among primary angle closure, its suspects, and nonoccludable angles: the Kumejima Study

PURPOSE

To quantitatively characterize the ultrasound biomicroscopy (UBM) configurations of the peripheral anterior chamber (AC) in primary angle closure (PAC) and its suspects and to evaluate the diagnostic performance of the UBM parameters to differentiate PAC/PAC suspects in a population-based setting.

DESIGN

Cross-sectional study.

METHODS

A random 461 of 4632 residents 40 years or older on a southwest island in Japan underwent UBM under light and dark conditions.

RESULTS

Of the 374 eligible randomly sampled residents (after excluding 87 with a history of intraocular surgeries, ocular trauma, or iritis; a physical or mental disability making the UBM measurement difficult; or refusal to undergo UBM measurements), reliable UBM images were obtained in 301 right eyes (80.4%). In 45 eyes with PAC/PAC suspects compared to 256 with nonoccludable angles, the angle-opening distance (AOD), trabecular-iris angle (TIA), and trabecular-ciliary process distance (TCPD) under light and dark conditions were smaller (P < .001), while the iris thickness was smaller only under dark conditions (P = .040). Dark-light changes in the AOD and TIA were significantly smaller in the PAC/PAC suspects than in the nonoccludable angles (P < .03); the iris thicknesses did not differ significantly between them. Areas under the receiver operating characteristic curves of the AOD at 500 μm from the scleral spur (AOD500) and TIA in light were 0.94, suggesting these parameters were good for differentiating PAC/PAC suspects. The ideal cutoff values for the AOD500 and TIA under light conditions were 0.17 mm (sensitivity, 0.82; specificity, 0.96) and 15.2 degrees (sensitivity, 0.83, specificity, 0.93), respectively.

CONCLUSIONS

Eyes with PAC/PAC suspects had shallow ACs, anteriorly located ciliary bodies, and smaller dark-light changes in the peripheral AC depth, while the iris thickness was similar to that in eyes with nonoccludable angles. The peripheral AC depth under light conditions could most clearly differentiate PAC/PAC suspects from nonoccludable angles.

Angle closure glaucoma: a mechanistic review

PURPOSE OF REVIEW

With recent advances in imaging techniques such as anterior segment optical coherence tomography and ultrasound biomicroscopy, there is a better understanding of nonpupil block mechanisms and novel risk factors contributing to the pathogenesis of angle closure glaucoma.

RECENT FINDINGS

Recent studies suggest that multiple anatomical and physiological factors interplay in the pathogenesis of angle closure glaucoma. The association of greater iris convexity, area and thickness with narrow angles could result in a more anterior bowing and crowding of the peripheral iris. Other novel anatomic parameters such as greater lens vault, smaller anterior chamber width, area and volume, independently increase the risk of having angle closure. Dynamic increase or lesser reduction in iris volume during dilation supports the theory of physiological predisposition to the disease process. Choroidal expansion has been demonstrated in untreated and treated, acute and chronic primary angle closure eyes. It remains unknown whether this finding is a cause or effect in this condition.

SUMMARY

With a wider availability of imaging tools and a better understanding of risk factors and mechanisms, clinicians maybe able to more accurately identify those at greater risk of developing angle closure disease and tailor their treatment according to the predominant factor(s) involved.

Relationship between relative lens position and appositional closure in eyes with narrow angles

PURPOSE

To investigate the relationship between relative lens position (RLP) and appositional closure in eyes with narrow angles.

METHODS

Ultrasound biomicroscopy (UBM) was used to measure anterior chamber depth (ACD) and lens thickness (LT), and the IOLMaster to measure axial length (AL). The number of quadrants with appositional closure was assessed by UBM under dark conditions. The RLP was calculated thus: RLP = 10 × (ACD + 0.5 LT) /AL.

RESULTS

This study comprised 30 consecutive patients (30 eyes) with narrow-angle eyes defined as Shaffer grade 2 or lower and without peripheral anterior synechiae (24 women, 6 men; mean age ± SD, 67.3 ± 10.4 years; range, 42-87 years). Under dark conditions, 66.7% of the eyes with narrow angles showed appositional closure in at least one quadrant. Of the various ocular biometric parameters, only the RLP significantly decreased with appositional closure in at least one quadrant (P = 0.005).

CONCLUSION

A decrease in the RLP can be predictive of appositional closure for narrow-angle eyes under dark conditions.

Ocular refractive and biometric characteristics in patients with thalassaemia major

BACKGROUND

Thalassaemia major is associated with characteristic findings in craniofacial bony structures and thereby may render abnormal bony orbit and subsequently distinctive ocular biometry. The purpose of the present study was to evaluate the ocular refractive and biometric characteristics in patients with thalassaemia major.

METHODS

This case-controlled study comprised 94 eyes of 47 patients with thalassaemia major and 88 eyes of 44 age- and sex-matched healthy control subjects. All participants had a complete ocular examination including slitlamp biomicroscopy, fundoscopy, ocular biometry, keratometry, refraction and analysis using Fourier transformation.

RESULTS

There were no significant differences in spherical equivalent (p = 0.66) and total astigmatism (p = 0.83) between groups. Mean uncorrected vision and visual acuities (logMar) were similar (p = 0.32 and p = 0.71, respectively). Compared with controls, thalassaemic patients had a shorter axial length (23.01 ± 0.12 [SEM] mm versus 23.46 ± 0.12 mm, p = 0.035), thicker crystalline lens (4.01 ± 0.11 mm versus 3.87 ± 0.1 mm, p = 0.046) and steeper average keratometry (44.02 ± 0.24 D versus 43.44 ± 0.24, p = 0.03). Fifty-seven per cent of thalassaemic patients had against-the-rule astigmatism (total), while 64.6 per cent of controls showed a with-the-rule pattern (p < 0.05). These patterns were also found for corneal astigmatism. The magnitudes of total, corneal and lenticular astigmatism were similar among groups. Regression analysis showed significant correlation between corneal (J0 and J45) and total (J0 and J45) astigmatism. The correlations were less prominent between lenticular and total J0 and J45. The mean intraocular pressure was 14.68 ± 0.27 mmHg and 13.3 ± 0.26 mmHg in the thalassaemia and control groups, respectively (p < 0.001). Six eyes (12.8 per cent) of four patients in the thalassaemia group had posterior subcapsular cataract, while the condition had not been observed in controls (p = 0.049).

CONCLUSIONS

Shorter axial length, thicker lens, steeper corneal curvature and more against-the-rule pattern were characteristic findings in patients with thalassaemia major.

Reverse pupillary block slows iris contour recovery from corneoscleral indentation

Corneoscleral indentation changes the iris contour and alters the angle between the iris and cornea. Although this effect has long been observed, the mechanism by which it occurs remains poorly understood. Previous theoretical research has shown that corneoscleral indentation can deform the eye globe and consequently rotate the iris root. In this work, we studied the fluid-structure interaction between the iris and aqueous humor, driven by iris root rotation. The iris root rotation obtained from our previous whole-globe model was used as a boundary condition for a fluid-structure interaction finite element model of the anterior eye. We studied the effect of two parameters-rotation angle and indentation speed-on the iris contour and aqueous humor dynamics. We found that posterior rotation of the iris root caused posterior bowing of the iris. After the iris root was returned to its original orientation, the aqueous humor was trapped in the anterior chamber because the iris tip pinned against the lens (reverse pupillary block). After 0.5-2 min of simulation, aqueous humor secretion into the posterior chamber and outflow from the anterior chamber allowed the system to return to its original steady state flow condition. The faster or farther the iris root rotated, the longer it took to return to steady state. Reverse pupillary block following corneoscleral indentation is a possible explanation for the clinical observation that prevention of blinking causes the iris to drift forward.

Comparison of visual function between phakic eyes and pseudophakic eyes with a monofocal intraocular lens

PURPOSE

To compare all-distance visual acuity and contrast visual acuity with and without glare (glare visual acuity) between phakic eyes with a clear lens and pseudophakic eyes with a monofocal intraocular lens.

SETTING

Hayashi Eye Hospital, Fukuoka, Japan.

METHODS

This study comprised phakic), pseudophakic eyes in 4 age groups (40s, 50s, 60s, 70s). Corrected visual acuity from far to near, contrast visual acuity, and glare visual acuity were examined.

RESULTS

The mean corrected intermediate and near visual acuities were significantly better in phakic eyes than in pseudophakic eyes in patients in their 40s and 50s (P<or=.0215); corrected distance visual acuity was similar. In the 60s and 70s age groups, there was no statistically significant difference in corrected visual acuity at any distance. The region of accommodation at which eyes achieved a corrected visual acuity of 20/29 or 20/40 was greater in phakic eyes than in pseudophakic eyes in the 40s and 50s age groups (P<or=.0302) but was similar in 60s and 70s age groups. In all age groups, there were no significant differences in photopic or mesopic contrast visual acuity or glare visual acuity.

CONCLUSIONS

In patients in their 40s and 50s, the region of accommodation in phakic eyes was greater than in pseudophakic eyes; the region was similar in patients in their 60s and 70s. Because contrast sensitivity with and without glare was similar at all ages, visual function appeared to be comparable in patients 60 years and older.

Anterior-segment imaging for assessment of glaucoma

This article summarizes the physics, technology and clinical application of ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT) for assessment of the anterior segment in glaucoma. UBM systems use frequencies ranging from approximately 35 to 80 MHz, as compared with typical 10-MHz systems used for general-purpose ophthalmic imaging. OCT systems use low-coherence, near-infrared light to provide detailed images of anterior segment structures at resolutions exceeding that of UBM. Both technologies allow visualization of the iridocorneal angle and, thus, can contribute to the diagnosis and management of glaucoma. OCT systems are advantageous, being noncontact proceedures and providing finer resolution than UBM, but UBM systems are superior for the visualization of retroiridal structures, including the ciliary body, posterior chamber and zonules, which can provide crucial diagnostic information for the assessment of glaucoma.

Ultrasound biomicroscopic analysis of iris-sutured foldable posterior chamber intraocular lenses

PURPOSE

To report ultrasound biomicroscopic (UBM) findings of iris-sutured foldable posterior chamber intraocular lenses (PCIOLs).

DESIGN

Prospective, noninterventional consecutive case series.

METHODS

Fifteen eyes with foldable acrylic IOL implantation using peripheral iris suture fixation in the absence of capsular support were included. UBM was used to determinate the haptic position in relation to the ciliary sulcus and ciliary body in these eyes. Additionally, anterior chamber depth, lens tilt, site of suture fixation, focal iris or angle abnormalities, and relationship of iris to lens were determined. Main outcome measures were haptic position, anterior chamber depth, and iris anatomic changes.

RESULTS

Of the 30 haptics imaged, 16 (53.3%) were positioned in the ciliary sulcus. Nine (30%) haptics were found over the ciliary processes, and 5 (16.7%) were over pars plana. No patients were found to have peripheral anterior synechiae present at the haptic position. The mean (+/- standard deviation) depth of the anterior chamber was 3.84 +/- 0.36 mm. The iris profile was altered in all patients at the iris-haptic suture fixation site. No angle abnormalities or tilted lenses were found.

CONCLUSIONS

Iris-sutured PCIOL haptics were found to be in the ciliary sulcus or over the ciliary body with no significant tilt on UBM analysis. The procedure respects the angle anatomy, and no evidence of angle closure was found. The anterior chamber was deeper than has been reported previously for scleral sutured PCIOLs and was similar to that of pseudophakic eyes. This may have implications for surgical technique, IOL power calculations, and postoperative complications.

Rectification of width and area of the ciliary cleft in dogs

The width and area of the ciliary cleft (CCW and CCA) according to ultrasound biomicroscopy was rectified to compare dogs of different body sizes/weights, including toy breed (TBG), small breed (SBG), medium breed (MBG) and large/giant breed groups (LGBG). A linear correlation was detected between the natural log of body weight and the ocular axial length (OAL) reflecting the ocular size (OS; r=0.81, p<0.001). A significant positive correlation was found between OAL and the distance of the Schwalbe's line to the anterior lenticular capsule (SLD; r=0.87, p<0.001), suggesting that SLD could rectify canine OS. Rectified CCW (r-CCW) and CCA (r-CCA) were calculated using SLD and fixed SLD as the SLD mean (SLDM). The SLDM was 2.55 mm in this study, and r-CCW and r-CCA were calculated as r-CCW = CCW x (2.55/SLD) and r-CCA = CCA x (2.55/SLD)(2). The CCW values of TBG, SBG and MBG were narrower than those of LGBG (p<0.05). There were significant statistical differences in CCA between all groups other than TBG and SBG (p<0.05). There were no significant differences in r-CCW and r-CCA in any of the groups. In addition, CCW/SLD did not show significant changes in dogs with different body sizes/weights. These results suggested that r-CCW, r-CCA and CCW/SLD can be used for comparison between dogs of different body sizes/weights.

Biometric and corneal topographic characteristics in patients with Weill-Marchesani syndrome

PURPOSE

To determine the biometry of ocular structures and corneal topographic characteristics in patients with Weill-Marchesani syndrome.

SETTING

Department of Ophthalmology, Shiraz University of Medical Sciences, Shiraz, Iran.

METHODS

Patients with Weill-Marchesani syndrome (syndrome group) and age-matched normal subjects (control group) were evaluated. All had a complete ocular examination including refraction and analysis using Fourier transformation, slitlamp biomicroscopy, pachymetry, keratometry, and ocular biometry. The following A-scan parameters were measured: anterior chamber depth (ACD), lens thickness, axial length (AL), lens-AL factor, and relative lens position (RLP). Corneal topography examinations were performed in the syndrome group only.

RESULTS

The syndrome group comprised 7 female patients and the control group, 20 female subjects. The syndrome group had statistically significantly higher myopia and corneal astigmatism than the control group (P<.0001). Oblique astigmatism was common in the syndrome group, showing a strong right-left specificity (right eyes' axes in the 135-degree meridian, left eyes' axes in the 45-degree meridian). The syndrome group had a statistically significantly shorter AL, shallower ACD, thicker lens, higher calculated lens power, and a higher lens-AL factor (P<.0001). However, there was no statistically significant difference in RLP (P = .32). The syndrome group also had statistically significantly thicker corneas and higher keratometry values (P<.0001).

CONCLUSION

Characteristic ocular findings in patients with Weill-Marchesani syndrome were a steep, thick cornea with a strong right-left specificity of corneal astigmatism; a thick lens; a short AL; and a shallow ACD.

Comparison of ultrasound biomicroscopic changes after glaucoma triple procedure and trabeculectomy in eyes with primary angle closure glaucoma

PURPOSE

To evaluate ultrasound biomicroscopy changes in the anterior chamber angle (ACA) configuration after glaucoma triple procedure (GTP), compared with those seen after trabeculectomy, in eyes with primary angle closure glaucoma (PACG).

METHODS

Twenty-nine PACG eyes that underwent GTP were compared with 27 eyes that underwent trabeculectomy only, using ultrasound biomicroscopy. Anterior segment parameters such as anterior chamber depth, angle opening distance (AOD500), trabecular ciliary process distance, trabecular iris angle, iris ciliary process distance, iris thickness along the trabecular ciliary process distance line (ID1), scleral ciliary process angle, scleral iris angle, and angle recess area were measured preoperatively and at 3 months postoperatively; these parameters were then compared between the procedures.

RESULTS

Among the anterior segment parameters, postoperative increases in the anterior chamber depth, AOD500, and angle recess area were statistically significant in the eyes that underwent trabeculectomy. For the eyes that underwent GTP, all parameters except the iris ciliary process distance and ID1 were significantly increased after the operation.

CONCLUSIONS

For the eyes that underwent GTP, the ciliary body process was posteriorly positioned and the ACA was significantly increased after the operation, as compared with the eyes that underwent trabeculectomy. The posterior shift of the ciliary process only after GTP was indirect evidence that the lens plays an important role in ACA configuration in eyes with PACG.

Inaccuracy of intraocular lens power prediction for cataract surgery in angle-closure glaucoma

PURPOSE

To assess the accuracy of intraocular lens (IOL) power predictions for cataract surgery in eyes with primary angle-closure glaucoma (ACG). Because of shifting of the capsular bag apparatus and shortening of the axial length, preoperative calculation of IOL power may be inaccurate for eyes with ACG.

MATERIALS AND METHODS

This retrospective comparative case series comprised of 42 eyes from 42 patients with primary ACG and 45 eyes from 45 subjects with normal open-angles undergoing uneventful cataract surgery. Anterior segment biometry including anterior chamber depth, lens thickness, and axial length were compared. Using the SRK-II formula, the powers of the implanted IOL and the actual postoperative spherical equivalent (SE) refractive errors were compared between the two groups. Also, the absolute values of differences between predicted and residual SE refractive errors were also analyzed for each group.

RESULTS

In ACG patients, anterior chamber depth and axial length were shorter and the lens was thicker than normal controls (all p < 0.001). Even though residual SE refractive error was not significantly different (p = 0.290), the absolute value of the difference between predicted and residual SE refractive error was 0.64 +/- 0.50 diopters in AGC patients and 0.39 +/- 0.36 diopters in control subjects (p = 0.012). The number of eyes that resulted in inaccurate IOL power predictions of more than 0.5 diopters were 21 (50.00%) in the ACG group, but only 12 (26.67%) in the control group (p = 0.043).

CONCLUSION

IOL power predictions for cataract surgery in ACG patients can be inaccurate, and it may be associated with their unique anterior segment anatomy.

High-resolution ultrasound imaging of the eye - a review

This report summarizes the physics, technology and clinical application of ultrasound biomicroscopy (UBM) of the eye, in which frequencies of 35 MHz and above provide over a threefold improvement in resolution compared with conventional ophthalmic ultrasound systems. UBM allows imaging of anatomy and pathology involving the anterior segment, including regions obscured by overlying optically opaque anatomic or pathologic structures. UBM provides diagnostically significant information in conditions such as glaucoma, cysts and neoplasms, trauma and foreign bodies. UBM also can provide crucial biometric information regarding anterior segment structures, including the cornea and its constituent layers and the anterior and posterior chambers. Although UBM has now been in use for over 15 years, new technologies, including transducer arrays, pulse encoding and combination of ultrasound with light, offer the potential for significant advances in high-resolution diagnostic imaging of the eye.

Imaging the ocular anterior segment with real-time, full-range Fourier-domain optical coherence tomography

We have demonstrated a novel Fourier-domain optical coherence tomography system and signal-processing algorithm for full-range, real-time, artifact-free quantitative imaging of the anterior chamber. Cross-sectional full-range images comprising 1024 x 800 pixels (axial x lateral) were acquired and displayed at 6.7 images/s. Volumetric data comprising 1024 x 400 x 60 pixels (axial x lateral x elevation) were acquired in 4.5 seconds with real-time visualization of individual slices and 3-dimensional reconstruction performed in postprocessing. Details of the cornea, limbus, iris, anterior lens capsule, trabecular meshwork, and Schlemm's canal were visualized. Quantitative surface height maps of the corneal epithelium and endothelium were obtained from the volumetric data and used to generate corneal thickness maps.

Angle-closure: risk factors, diagnosis and treatment

INTRODUCTION

Primary angle-closure glaucoma (PACG) is the leading cause of blindness in East Asia. The disease can be classified into primary angle-closure suspect, primary angle closure (PAC), and PACG. Pupil-block, anterior nonpupil-block (plateau iris and peripheral iris crowding), lens related and retrolenticular mechanisms have been suggested as the four main mechanisms of angle closure.

RISK FACTORS

The risk factors for PAC are female gender, increasing age, Inuit or East Asian ethnicity, shallow anterior chamber, shorter axial length, and genetic factors.

DIAGNOSIS

The diagnosis of acute PAC is mainly clinical. Diagnosis can be made with careful slit lamp examination, including intraocular pressure (IOP) measurement and gonioscopy. The diagnosis of chronic PAC and chronic PACG also require a careful history to assess risk factors, slit lamp examination including IOP and gonioscopy. Further investigations may also be required including visual fields, ultrasound biomicroscopy, and other imaging methods.

MANAGEMENT

In acute PAC, rapid control of the IOP needs to be achieved to limit optic-nerve damage. This can be carried out medically, and/or by laser iridoplasty. Both the affected and fellow eye should undergo laser peripheral iridotomy (PI). The aim of treating chronic PAC is to eliminate the underlying pathophysiological mechanism and to reduce IOP. This can be done by carrying out laser PI, iridoplasty, medical therapy, or surgery (trabeculectomy, lens extraction, combined lens extraction with trabeculectomy and goniosynechialysis).

CONCLUSION

Angle-closure glaucoma is usually an aggressive, visually destructive disease. By assessing the risk factors and diagnosing the mechanism involved in a patient's condition, the management of that patient can be tailored appropriately.

Ocular biometry in acute and chronic angle-closure glaucoma

AIM

To evaluate the biometric difference between eyes with acute angle-closure (AAC) attack, their uninvolved fellow eyes and eyes with chronic angle-closure glaucoma (CACG).

METHODS

Patients with prior laser iridotomy on both eyes for unilateral AAC attack or CACG were recruited. We compared ocular biometric parameters by A-scan ultrasonography of the acutely affected eyes with those of the uninvolved fellow eyes and with eyes affected by CACG.

RESULTS

Thirty-three patients with unilateral AAC attack and 41 patients with CACG were included. The eyes with AAC attack had a significantly shallower anterior chamber depth (ACD), thicker lens, shorter axial length, higher lens/axial length factor and more anteriorly positioned lens than the eyes with CACG. The uninvolved fellow eyes had a significantly shallower ACD, shorter axial length and higher lens/axial length factor compared with the eyes with CACG. Acutely affected eyes had a shallower ACD and more anteriorly positioned lens than did the uninvolved fellow eyes.

CONCLUSION

Eyes with AAC attack had a more crowded anterior segment compared with uninvolved fellow eyes and those affected by CACG. In addition to ACD, relative lens size, represented by the lens/axial length factor, and relative lens position appear to play important roles in the development of AAC attack.

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.

Prevalence of plateau iris syndrome in young patients with recurrent angle closure

BACKGROUND

To assess and describe the prevalence and clinical features associated with plateau iris syndrome (PIS) in young individuals with recurrent angle closure despite initial therapy.

METHODS

Chart review of 137 relatively young individuals (aged < 60 years) with symptoms of angle closure between 1995 and 2005. A follow-up period of 36 months after initial presentation was retrospectively analysed. Seventy-six patients with recurrent angle closure symptoms were clinically reviewed using gonioscopy and ultrasound biomicroscopy.

RESULTS

Based on chart analysis, 30 of 137 individuals were diagnosed with PIS (22%). After clinical review, 34 additional patients suffered from PIS as the underlying cause for persistent angle closure symptoms. The prevalence of PIS in our patient population with recurrent angle closure symptoms in spite of initial iridotomy or iridectomy was 54%.

CONCLUSION

Among angle closure in young individuals, PIS is not uncommon. The causative mechanism of PIS in young individuals is peripheral iris block, rather than pupillary block which is more often prevalent in older patients. For proper diagnosis and therapy, ultrasound biomicroscopy and gonioscopy should be performed on every young individual with angle closure symptoms.

Does an iridotomy provide protection against narrowing of the anterior chamber angle during Valsalva maneuvre in eyes with primary angle closure

PURPOSE

To evaluate changes at the anterior chamber angle during Valsalva manoeuver, in eyes having primary angle closure (PAC) and a patent laser peripheral iridotomy.

METHODS

Twenty-three eyes of 23 consecutive patients underwent a recording of applanation tonometry, measurement of the anterior chamber angle recess, angle opening distance, iris thickness, anterior chamber depth, and pupil size on ultrasound biomicroscopy before and during the Valsalva maneuver. The Valsalva manoeuver was standardized to a pressure of 40 mmHg for 15 s, using a manometer.

RESULTS

The mean baseline intraocular pressure changed from 18.86+3.79 to 26.73+4.73 mmHg during Valsalva, (P<0.0001). The anterior chamber angle recess narrowed from 16.62+6.24 to 6.5+4.02 degrees (P<0.0001). There was a significant increase in the thickness of the ciliary body from 0.92+0.25 to 1.17+0.31 mm (P=0.0006) and in the iris thickness from 0.47+0.17 to 0.57+0.11 mm (P=0.007). A significant increase in pupillary diameter (P=0.008) and a decrease in the angle opening distance (P<0.0001) also occurred during Valsalva, whereas there was no significant change in the anterior chamber depth (P=0.056). The angle recess during Valsalva had a positive correlation with the baseline anterior chamber angle (r=0.41, P=0.05) and a negative correlation with the ciliary body thickness (r=-0.52, P=0.046).

CONCLUSIONS

The induction of Valsalva maneuver in day-to-day activities can lead to significant anterior segment angle shallowing and can lead to progression from the PAC stage to primary angle closure glaucoma in such predisposed eyes. The presence of a patent laser iridotomy may not prevent irido trabecular apposition during the Valsalva maneuver.