Comparison of ultrasound biomicroscopic parameters after laser iridotomy in eyes with primary angle closure and primary angle closure glaucoma

Comparison of intraocular lens power calculation formulas in patients with a history of acute primary angle-closure attack

BACKGROUND

To compare the accuracy of nine intraocular lens (IOL) power calculation formulas, including three traditional formulas (SRK/T, Haigis, and Hoffer Q) and six new-generation formulas (Barrett Universal II [BUII], Hill-Radial Basis Function [RBF] 3.0, Kane, Emmetropia verifying optical [EVO], Ladas Super, and Pearl-DGS) in patients who underwent cataract surgery after acute primary angle closure (APAC).

METHODS

In this retrospective cross-sectional study, 44 eyes of 44 patients (APAC) and 60 eyes of 60 patients (control) were included. We compared the mean absolute error, median absolute error (MedAE), and prediction error after surgery. Subgroup analyses were performed on whether axial length (AL) or preoperative laser peripheral iridotomy affected the postoperative refractive outcomes.

RESULTS

In the APAC group, all formulas showed higher MedAE and more myopic shift than the control group (all P < 0.05). In APAC eyes with AL ≥ 22 mm, there were no differences in MedAEs according to the IOL formulas; however, in APAC eyes with AL < 22 mm, Haigis (0.49 D) showed lower MedAE than SRK/T (0.82 D) (P = 0.036) and Hill-RBF 3.0 (0.54 D) showed lower MedAE than SRK/T (0.82 D), Hoffer Q (0.75 D) or Kane (0.83 D) (P = 0.045, 0.036 and 0.027, respectively). Pearl-DGS (0.63 D) showed lower MedAE than Hoffer Q (0.75 D) and Kane (0.83 D) (P = 0.045 and 0.036, respectively). Haigis and Hill-RBF 3.0 showed the highest percentage (46.7%) of eyes with PE within ± 0.5 D in APAC eyes with AL < 22 mm. Iridectomized eyes did not show superior precision than the non-iridotomized eyes in the APAC group.

CONCLUSIONS

Refractive errors in the APAC group were more myopic than those in the control group. Haigis and Hill-RBF 3.0 showed high precision in the eyes with AL < 22 mm in the APAC group.

Pentacam changes in primary angle-closure glaucoma after different lines of treatment

AIM

To assess the changes in the anterior chamber parameters using Pentacam following four different lines of treatment of primary angle-closure glaucoma (PACG).

METHODS

A retrospective comparative study included 126 patients (126 eye) presented within 24-48h after acute angle-closure glaucoma (AACG). Patients were divided into 2 groups: group A (68 eyes) with controlled intraocular pressure (IOP) ≤21 mm Hg, which included subgroup A1 (34 eyes) with clear lens underwent Nd:YAG laser peripheral iridotomy (LPI) and subgroup A2 (34 eyes) with cataract underwent standard phacoemulsification; and group B (58 eyes) with uncontrolled IOP, which included subgroup B1 (30 eyes) with clear lens underwent trabeculectomy and subgroup B2 (28 eyes) with cataract underwent combined phacoemulsification and trabeculectomy. Patients were followed up for at least 3mo. Primary outcomes were Pentacam anterior segment measurements [anterior chamber angle (ACA) and depth (ACD)]. Secondary outcomes were changes in IOP, visual acuity (VA) and recorded complications.

RESULTS

At the 3rd month, there was significant increase in the ACA values in all studied groups compared to preoperative values (P<0.001). The highest percent of increase in ACA was recorded in phacotrabeculectomy group B2 (128.40%). There was significant increase in ACD values at 3rd month compared with baseline values (P<0.001) for groups A1, A2, and B2; without change in B1 trabeculectomy group. The maximum deepening of ACD was noticed in group B2 with 94.27% increase. Significant decrease in postoperative IOP in groups A2, B1 and B2 (P<0.001, P=0.014, and P<0.001 respectively). In group A1 there was significant increase in 3rd month postoperative IOP from baseline values (P<0.001). The maximum decrease in IOP was noticed in group B2 with 59.54% decrease. VA improvement in 3rd month postoperative was recorded in all studied groups, maximum VA improvement was observed in group B2 up to 0.2 logMAR.

CONCLUSION

Pentacam can be a helpful tool in studying and comparing the effect of the different lines of management of PACG on the anterior chamber measures. Phacotrabeculectomy was proved to be an effective line for managing PACG with resultant significant increase in the anterior chamber parameters, IOP reduction as well as maximum VA improvement. LPI has only temporary effect on IOP with significant changes in ACA and ACD. Phacoemuslification alone can be an option in treating PACG. Trabeculectomy resulted in temporary increase in the anterior chamber parameter which subsequently returned to baseline values.

Noninvasive and Noncontact Sequential Imaging of the Iridocorneal Angle and the Cornea of the Eye

Purpose

High-resolution imaging of the critical anatomic structures of the eye, especially of the anterior chamber, in vivo, remains a challenge, even with currently available state-of-the-art medical imaging techniques. This study aims for the noninvasive and noncontact sequential imaging of the iridocorneal angle, especially the trabecular meshwork (TM) and the cornea of the eye in high-resolution using a newly developed imaging platform.

Methods

Bessel beam scanned light sheet fluorescence microscopy is used to attain high-resolution images of the TM. The ability of the Bessel beam to self-reconstruct around obstacles increases the image contrast at the TM region inside eye by reducing scattering and shadow artifacts. With minimal modifications, the excitation arm of the developed imaging system is adapted for noncontact, high-resolution corneal imaging.

Results

High-resolution images of the TM structures and cellular-level corneal structures are obtained in ex vivo porcine eyes, and subsequently in New Zealand white rabbit, in vivo. The spatial resolution of the developed system is 2.19 µm and has a noncontact working distance of 20 mm.

Conclusions

A high-resolution imaging platform for noncontact sequential imaging of the TM and the cornea of the eye is developed. This imaging system is expected to be of potential interest in the evaluation and diagnosis of glaucoma and corneal diseases.

Translational Relevance

The developed prototype offers the plausibility of in vivo, noncontact, and high-resolution imaging of the iridocorneal angle and cornea of the eye that will aid clinicians in diagnosing open-angle glaucoma and corneal diseases better.

Evaluation of the role of ultrasound biomicroscopy in advanced retinoblastoma: A prospective study on Asian Indian children

Aim: To evaluate the role of ultrasound biomicroscopy (UBM) in retinoblastoma (RB).Methods: Children with advanced unilateral RB were included. UBM was performed to look for tumour invasion into the anterior segment (AS) and for evaluation of quantitative parameters. Enucleation was done and UBM findings were correlated with histopathology. The main outcome measures were sensitivity and specificity of UBM for detecting AS invasion and comparison of quantitative parameters between the tumour affected and fellow eyes.Results: Fifty patients were evaluated. The mean age was 2.76 ± 1.63 years. Enucleation was performed in 50 eyes. The sensitivity and specificity of UBM for AS invasion were 80% (95% CI, 44-97%) and 95% (95% CI, 83-99%), respectively. UBM showed a sensitivity and specificity of 100% (95% CI, 59-100%) and 95% (95% CI, 84-99%), respectively, for iris invasion, 88% (95% CI, 47-100%) and 100% (95% CI, 92-100%), respectively, for ciliary body invasion, and 63% (95% CI, 24-91%) and 100% (95% CI, 92-100%), respectively, for anterior chamber (AC) angle invasion. Quantitative parameters were studied in 100 eyes. As compared to the fellow eyes, the AC angle was narrow (p < 0.05), posterior chamber was shallow (p = 0.004) and zonular length was increased (p = 0.001) in RB eyes.Conclusion: This clinicopathological study provides valuable insights into the role of UBM for evaluation of anterior extension of RB and for assessment of architectural changes in the AS due to the tumour.

Longitudinal Change in Peripheral Anterior Chamber Depth of Eyes with Angle Closure after Laser Iridotomy

Purpose

To investigate longitudinal changes in peripheral anterior chamber depth (pACD) of eyes with angle closure after laser iridotomy (LI) and factors related to prognosis.

Design

Retrospective cohort study.

Methods

Eyes with primary angle closure (PAC), acute PAC, or chronic angle closure glaucoma (CACG) that underwent LI (LI group) and eyes that underwent phacoemulsification and intraocular lens insertion (PEA + IOL group) were employed. Longitudinal changes in pACD were evaluated with a scanning peripheral anterior chamber depth analyzer (SPAC) in addition to routine ophthalmic examination.

Results

Forty-eight eyes of LI groups (69.8 ± 8.5 years) and 21 eyes of PEA + IOL group (65.6 ± 12.7 years) were enrolled. Mean follow-up times of LI group and PEA + IOL group were 43.4 ± 12.7 months and 36.5 ± 2.5 months, respectively. LI significantly increased pACD as indicated by the SPAC grade change from 3.8 ± 1.1 to 4.6 ± 1.2 (p < 0.001). However, SPAC grade was gradually reduced and reached the pre-LI level by the third year of follow up. PEA + IOL also significantly increased SPAC grade from 6.7 ± 1.6 to 8.7 ± 2.0 (p < 0.001), but no time-related change was observed. Twenty-three cases of LI group presented with deterioration of glaucoma control. The type of angle closure, plateau iris configuration, peripheral anterior synechia, and glaucomatous visual field defects were significantly associated with prognosis of glaucoma after LI.

Conclusions

Peripheral ACD is temporarily deepened by LI, but returns to the pre-LI level in approximately three years. The type of angle closure and some factors may be related to glaucoma prognosis after LI.

Low iris and anterior chamber volume is associated with deepening after laser peripheral iridotomy in primary angle closure suspects

PURPOSE

To evaluate the association between baseline ocular variables and the widening of the anterior chamber angle by laser peripheral iridotomy (LPI) in primary angle closure suspects (PACS) using a new Fourier-domain swept-source anterior segment optical coherence tomography (FD-ASOCT).

METHOD

Sixty-six PACS eyes of 41 individuals were enrolled in this prospective interventional case series. An FD-ASOCT (Casia SS-1000 OCT; Tomey, Nagoya, Japan) was used to measure biometric baseline variables and at 1 month after the LPI. Paired t test was used to compare the difference between pre-and post-LPI measurements. Multivariate regression analysis was used to test for an association between baseline iris thickness and volume, anterior chamber depth and volume, and lens vault with a widening of the angle after an LPI. Changes in trabecular iris space area and angle opening distance after the LPI were main outcome measures.

RESULTS

The mean age of participants was 58.6 ± 8.7 years, 68.2% of whom were female. The angle opening distance, recess area, and trabecular iris surface area at 500 μm increased by 48 to 73% (all P < 0.001). Lens vault and iris volume did not change. A low anterior chamber volume and low iris volume were associated with angle greater deepening by LPI.

CONCLUSION

Eyes with a shallow anterior chamber and thinner irises are more likely to experience angle opening from an LPI.

'Van Herick Plus': a modified grading scheme for the assessment of peripheral anterior chamber depth and angle

AIM

To evaluate the accuracy of a new, modified grading scheme involving a short vertical slit beam, at the inferior angle for peripheral anterior chamber depth (PAC) and angle estimation and its correlation with anterior segment optical coherence tomography (ASOCT).

METHODS

A cross-sectional study of consecutive phakic patients, above 40 years of age, was performed. Using a short, vertical slit beam not reaching the pupil, the inferior angle at the sclerolimbal junction was evaluated, photographed and assessed by a ratio of peripheral anterior chamber depth to peripheral corneal thickness (PAC:PCT) and iridocorneal angle (ICA) on ImageJ software. The inferior angle at the same meridian was also recorded on ASOCT.

RESULTS

Based on the PAC:PCT ratio, the subjects were divided into four groups: I (<1/4), II (1/4-1/2), III (>1/2-1) and IV (>1). The clinically assessed angle by short vertical slit beam correlated well with ASOCT values, trabecular-iris angle (TIA) (r=0.918; p<0.001) and scleral spur angle (r=0.903, p<0.001). The mean difference between ICA and TIA on ASOCT was 0.797⁰; 95% limits of agreement:-5.767⁰ to 7.361⁰ (±1.96 SD). For angles graded narrow on ASOCT (TIA <20⁰), using a cut-off of peripheral PAC:PCT <1/4, the area under the curve was 0.918 with a sensitivity of 85.2% and a specificity of 88.2%. There was good agreement between ImageJ parameters with those assessed subjectively on photograph of the slit beam examination by a glaucoma fellow (weighted kappa=0.74) as compared with a general ophthalmologist, where there was moderate agreement (weighted kappa=0.57).

CONCLUSION

A short, vertical slit lamp beam evaluation at the inferior angle is an easy and relatively accurate method for both peripheral anterior chamber depth and angle assessment. It correlated well with ASOCT and can be used as a more reliable screening tool to identify eyes with possibly occludable angles.

Anterior segment morphology after laser iridotomy in primary angle closure suspects

PURPOSE

To evaluate and compare the changes in anterior segment parameters in primary angle closure suspects before and after laser peripheral iridotomy and intrasession repeatability of measurements before laser iridotomy as assessed by Scheimpflug-Placido disc topographer.

METHODS

Before laser iridotomy, 56 eyes of 56 primary angle closure suspect patients underwent anterior segment analysis with the Sirius Scheimpflug-Placido disc topographer system using glaucoma analysis mode, which was repeated a week after iridotomy. Anterior segment parameters such as central anterior chamber depth, central corneal thickness, anterior chamber volume and iridocorneal angle were analysed before and after laser iridotomy and compared with paired t-test. Three consecutive scans were obtained to assess the intrasession repeatability of measurements before iridotomy by a single examiner and intraclass correlation co-efficient was calculated. Multivariate regression analysis was performed to evaluate the predictors associated with iridocorneal angle narrowing.

RESULTS

Intraclass correlation co-efficient values ranged from 0.982 for anterior chamber volume to 0.998 for the iridocorneal angle. After laser iridotomy, mean central anterior chamber depth increased from 2.14 ± 0.29 mm to 2.21 ± 0.28 mm (p = 0.04), mean anterior chamber volume increased from 96.2 ± 16.98 mm³ to 98.14 ± 15.87 mm³ (p < 0.0001) and mean iridocorneal angle widened from 33.38 ± 3.96° to 34.82 ± 4.27° (p = 0.01), compared with pre-iridotomy status. There was no change in central corneal thickness, intraocular pressure or pupil diameter. Multivariate regression analysis model showed that at one week after iridotomy, iridocorneal angle opening was positively correlated with age (β = 0.773, p = 0.005) and anterior chamber volume (β = 1.308, p < 0.0001).

CONCLUSIONS

Laser peripheral iridotomy induces significant changes in the 3-D anterior segment morphology in primary angle closure suspect patients. The Scheimpflug-Placido disc topographer provides reproducible measurements of the iridocorneal angle and other parameters measured and hence, may become clinically useful for non-invasive detection of potentially occludable angles. Predictors of iridocorneal angle widening after iridotomy were older age and anterior chamber volume.

Changes in choroidal thickness after prophylactic iridectomy in primary angle closure suspect eyes using enhanced depth imaging optical coherence tomography

Purpose:

The aim of the present study was to evaluate the effect of surgical peripheral iridectomy (SPI) on choroidal thickness in primary angle-closure suspect (PACS) eyes.

Materials and Methods:

This was a prospective observational case series of 30 subjects with PACS. Ocular biometry was performed before SPI (baseline) and then 1 week later. Choroid was imaged by enhanced depth imaging optical coherence tomography (EDI-OCT). The choroidal thickness of the subfoveal area at 1 and 3 mm diameter around the fovea was determined. Central anterior chamber depth (ACD), lens thickness (LT), vitreous chamber depth (VCD), and axial length (AL) were measured by A-scan ultrasound. Parameters were compared before SPI (baseline) and 1 week later.

Results:

Thirty eyes of 30 patients with mean age of 61.53 ± 7.98 years were studied. There was no significant difference in the choroidal thickness at all macular locations before and after SPI (all P > 0.05). Mean subfoveal choroidal thickness was 279.61 μm ± 65.50 μm before and 274.54 μm ± 63.36 μm after SPI (P = 0.308). There was also no significant change in central ACD, LT, VCD, and LT after SPI (all P > 0.05).

Conclusions:

SPI does not appear to alter choroidal thickness in PACS eyes, as assessed using EDI-OCT. Long-term follow-up of PACS eyes treated with SPI may provide further insight into the effects of this treatment modality on the choroid.

Changes in ocular biometry and anterior chamber parameters after pharmacologic mydriasis and peripheral iridotomy in primary angle closure suspects

PURPOSE

The aim of this study was to evaluate the effects of pharmacologic mydriasis and Peripheral Iridotomy (PI) on ocular biometry and anterior chamber parameters in primary angle closure suspects.

METHODS

In this prospective interventional case series, 21 primary angle closure suspects were enrolled. Intraocular pressure, refraction, ocular biometry (Lenstar, LS900), and anterior chamber parameters (Pentacam HR) were measured at four occasions: before PI (before and after mydriasis with phenylephrine) and two weeks after PI (before and after mydriasis). The study was conducted on both eyes and only one eye per patient, in random, was included in the analysis.

RESULTS

The mean age of the participants was 60±7 years and 17 (81%) were female. There were no significant differences in intraocular pressure, refraction, keratometry, biometric and anterior chamber parameters between groups, except for anterior chamber volume, which showed increments with PI and mydriasis. The corresponding values for anterior chamber volume were as follows: 88.2±13.7mm(3) before PI, undilated; 106.3±18.8 before PI, dilated; 99.0±14.6 after PI, undilated, and 107.4±16.5 after PI, dilated (P<0.001).

CONCLUSIONS

This study showed no change in the ocular biometric and anterior chamber parameters including iridocorneal angle after PI and/or pharmacologic mydriasis except for increments in anterior chamber volume. This factor has the potential to be used as a numerical proxy for iris position in evaluating and monitoring patients with primary angle closure suspects after PI.

Comparison of ultrasound biomicroscopy and spectral-domain anterior segment optical coherence tomography in evaluation of anterior segment after laser peripheral iridotomy

AIM

To quantitatively assess narrow anterior chamber angle using spectral-domain anterior segment optical coherence tomography (SD-AS-OCT) and ultrasound biomicroscopy (UBM), and to evaluate the correlations and consistency between SD-AS-OCT and UBM.

METHODS

Fifty-five eyes from 40 patients were examined. Patients were diagnosed with primary angle-closure glaucoma (PACG) remission (11 eyes from 8 patients), primary angle closure (PAC, 20 eyes from 20 patients) and PAC suspect (24 eyes from 12 patients). Each eye was examined by SD-AS-OCT and UBM after laser peripheral iridotomy (LPI). The measurements of SD-AS-OCT were angle open distance (AOD), anterior chamber angle (ACA), trabecular iris angle (TIA), and trabecular iris space area (TISA). UBM measurements were AOD and TIA. Correlations of AOD500 and TIA500 between UBM and AS-OCT were assessed. All parameters were analysed by SPSS 16.0 and MedCalc.

RESULTS

ACA, TIA and AOD measured by SD-AS-OCT reached a maximum at the temporal quadrant and minimum at the nasal quadrant. TISA reached the maximum at the inferior and minimum at the superior quadrant. Group parameters of AOD500 and AOD750 showed a linear positive correlation, and AOD750 had less variability. UBM outcomes of AOD500 and TIA500 were significantly smaller than those of SD-AS-OCT. The results of the two techniques were correlated at the superior, nasal and inferior quadrants.

CONCLUSION

Both UBM and SD-AS-OCT are efficient tools for follow-up during the course of PACG. We recommended using parameters at 750 µm anterior to the sclera spur for the screening and follow-up of PACG and PAC. The two methods might be alternatives to each other.

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.

Application of anterior segment optical coherence tomography in glaucoma

Optical coherence tomography (OCT) is a cross-sectional, three-dimensional, high-resolution imaging modality that uses low coherence interferometry to achieve axial resolution in the range of 3-20 μm. Two OCT platforms have been developed: time domain (TD-OCT) and spectral (or Fourier) domain (SD/FD-OCT). Visante anterior segment OCT (Carl Zeiss Meditec) is a TD-OCT widely used for anterior segment imaging. The SD-OCT systems with both posterior and anterior segment imaging capabilities include the RTVue, iVue (Optovue), the Cirrus (Carl Zeiss Meditec), and the Spectralis (Heidelberg Engineering, Inc.). Each of the SD-OCTs has a wavelength in the range of 820-879 nm. Anterior segment OCT is a non-contact method providing high resolution tomographic cross-sectional imaging of anterior segment structures. Anterior segment OCT provides qualitative and quantitative assessment of the anterior segment structures important to the pathogenesis and the anatomical variations of glaucoma, and the approach to and success of treatment. We summarize the clinical applications of anterior segment OCT in glaucoma.

Anterior segment imaging in glaucoma

Anterior segment imaging allows objective assessment of the anterior segment of the eye, particularly the anterior chamber angle. Both qualitative and quantitative analyses are possible and aid in detecting and managing closed-angle and open-angle mechanisms in various forms of glaucoma. This review focuses primarily on anterior segment optical coherence tomography and ultrasound biomicroscopy, with emphasis on principles of technology, commercially available devices, and clinical applications in glaucoma with potential advantages and disadvantages of each technology.

Changes in Caucasian eyes after laser peripheral iridotomy: an anterior segment optical coherence tomography study

BACKGROUND

To evaluate by anterior segment optical coherence tomography (AS-OCT) the changes in the anterior chamber structures in Caucasian eyes after laser peripheral iridotomy (PI).

METHODS

Retrospective study of consecutive Caucasian primary angle closure suspect (PACS), primary angle closure (PAC) or primary angle closure glaucoma (PACG) patients who underwent laser PI over a 25-month period at a specialist glaucoma practice. The AS-OCT images of the temporal and nasal angles (in light and dark) before and after laser PI were analysed. The parameters studied were trabecular-iris angle (TIA), angle opening distance (AOD), trabecular-iris space area (TISA), trabecular-iris contact length (TICL), iris thickness (IT) and maximum iris bow height (MIBH).

RESULTS

Images of 71 eyes of 71 patients were assessed. The mean age at laser PI was 60.3 ± 10.0 years. Forty (56.3%) were women, and 14 (19.7%) had PACG. The mean time from laser PI to the follow-up AS-OCT scan was 5.92 ± 3.22 weeks. The IT did not alter significantly after laser PI, but there were significant increases in the TIA, AOD and TISA, as well as a significant decrease in MIBH, in both light and dark. There was no difference in the magnitude of change seen between the temporal and nasal angles, or between PACS/PAC and PACG eyes.

CONCLUSION

In Caucasian eyes, laser PI resulted in significant angle widening (increased TIA, AOD and TISA) and iris profile flattening (decreased MIBH) at the temporal and nasal angles based on AS-OCT imaging in both light and dark.

Quantitative analysis of anterior chamber following peripheral laser iridotomy using Pentacam in eyes with primary angle closure

Purpose. To quantify the effects of laser peripheral iridotomy (LPI) on peripheral anterior chamber depth (PACD), central internal anterior chamber depth (CACD), and anterior chamber volume (ACV) using Rotating Scheimpflug Imaging System, i.e., Pentacam, on Asian Indian eyes. Methods and Materials. This was an institutional, prospective, nonrandomized, interventional study. Sixty-eight eyes of 68 consecutive patients with primary angle closure were enrolled. Pentacam scanned the anterior ocular segment with the 25-image acquisition scan protocol and PACD, CACD, and ACV values were obtained. The PACD was measured in nasal, temporal, superior, and inferior meridian at 4 mm and 8 mm circles. Nd:YAG laser iridotomy was performed. Preiridotomy, immediate postiridotomy, 1 week and 1 month postiridotomy data for PACD, CACD, and ACV were acquired. The t test and repeated-measures analysis of variance (ANOVA) and one-way ANOVA were used for statistical significance. Results. Pre-LPI ACV increased immediately after iridotomy (28.4 mm3; p=0.001), at 1 week (15.9 mm3; p=0.001), and at 1 month post-LPI (19.8 mm3; p=0.00). There was no change in CACD (p>0.05). Significant PACD deepening was observed at 4 mm and 8 mm in all meridians (p<0.001) at all visits. Conclusions. Laser peripheral iridotomy significantly increased the PACD and ACV. Extent of the LPI-induced PACD increase was enhanced with increasing distance from the optical axis.

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.

Glaucoma and clinical characteristics in Vietnamese Americans

PURPOSE

To assess the proportions of glaucoma types and clinical characteristics in Vietnamese Americans in a single-center, retrospective study.

METHODS

Medical charts of Vietnamese-American patients who visited a single private practice in Northern California from 1998-2007 were reviewed. The main outcome measures included the distribution and characteristics of glaucoma types, and clinical parameters associated with the presence of various glaucomas.

RESULTS

Data from 2247 patients aged 18-98 years were reviewed. Glaucoma was determined for 305 patients (13.6%). Among this group, 54.8% had primary open-angle glaucoma (POAG), 26.9% had primary angle-closure glaucoma (PACG), 13.4% had mixed mechanism glaucoma (MMG), and 4.9% had secondary glaucoma. In the MMG group (41 patients), 27 patients who initially had open angles developed narrow angles and underwent laser peripheral iridotomy (LPI) with a mean follow up of 6.4 years from the time of iridotomy. The other 13 patients had glaucoma progression with open angles after LPI. One POAG patient had neovascular glaucoma due to retinal vein occlusion several years later. Compared to the PACG group, the MMG group had significantly lower baseline intraocular pressure (25.0 vs. 20.2 mmHg, p = 0.007) but with no difference in biometry.

CONCLUSIONS

POAG is the major type of glaucoma in this clinic-based Vietnamese population. However, Vietnamese appear to have a relatively higher proportion of PACG than Caucasians and those of African descent. It is recommended that gonioscopy be part of the regular eye check-up for adult Vietnamese patients.

Optimal fast T2-weighted magnetic resonance microscopy imaging of the eye and its clinical application

PURPOSE

To compare a half-Fourier single-shot rapid acquisition with relaxation enhancement (RARE) sequence with a balanced steady-state free precession (b-SSFP) sequence in the evaluation of the eye using magnetic resonance (MR) microscopy imaging and to clarify the usefulness of RARE microscopy imaging in evaluating nonoperative glaucoma patients and patients who have undergone surgery for glaucoma or cataract.

MATERIALS AND METHODS

One-mm and 2-mm slice thickness images of RARE sequence and b-SSFP sequence using a 1.5 T MR unit and a 23-mm microscopy coil were obtained in eight healthy volunteers. The signal-to-noise (S/N) ratio of aqueous humor in the anterior chamber was measured quantitatively and visualization of the anterior chamber anatomy was assessed qualitatively. Furthermore, we evaluated 21 glaucoma patients (including six postoperative patients) and four patients after cataract surgery with 2-mm slice thickness RARE MRI.

RESULTS

The 2-mm slice thickness RARE imaging had a significantly greater S/N ratio than the 1-mm slice thickness RARE imaging (P < 0.05) and acquired the best image quality among the four types of images (P < 0.01). Additionally, 2-mm slice thickness RARE microscopy imaging could depict anterior chamber anatomy of glaucoma eyes and eyes after cataract surgery.

CONCLUSION

We believe that optimal fast T2-weighted MR microimaging might become a useful ophthalmologic examination technique.

Comparison of internal anterior chamber diameter measured with ultrabiomicroscopy with white-to-white distance measured using digital photography in aphakic eyes

PURPOSE

Measuring the anterior chamber diameter (AC) is important both for diagnostics and before ocular surgery. In clinical practice, horizontal AC diameter is usually estimated on the basis of measurements of corneal diameter (so-called white-to-white [WTW] distance). The usual method for selecting an appropriate size for an AC lens is to add 1 mm to WTW measurement. The purpose of this study was to compare AC diameter measured using ultrasound biomicroscopy (UBM) with WTW distance measured using digital photography in aphakic eyes.

METHODS

The data were gathered prospectively from a nonrandomized consecutive series of aphakic patients. The examined group consisted of 23 eyes of 23 adult patients, mean age 71.17 years. WTW diameter was measured in the 3 o'clock and 9 o'clock meridian on a digital photograph. Internal horizontal AC diameter measurements were performed in the 3 o'clock and 9 o'clock meridian with the Sonomed Ultrabiomicroscopy device with a 50-MHz probe.

RESULTS

Mean horizontal WTW diameter measured using digital photographs was 11.65+/-0.38 mm and mean horizontal internal AC diameter measured using UBM was 13.53+/-0.83 mm. A significant difference in mean WTW diameter measured using digital photography and UBM was found (Mann-Whitney U test, p<0.05). There was a significant correlation between these values (Spearman=0.70, p<0.001).

CONCLUSIONS

In order to obtain good and precise measurements of internal AC diameter, a method of direct visualization of the intraocular structures should be used. Despite the limits of a small case series, our results support the use of UBM technique for preoperative evaluation of the internal AC diameter and AC intraocular lens sizing in aphakic eyes.

Anterior chamber configuration in patients with glaucoma: MR gonioscopy evaluation with half-Fourier single-shot RARE sequence and microscopy coil

The purpose of the study was to determine the accuracy of half-Fourier single-shot rapid acquisition with relaxation enhancement high-spatial-resolution magnetic resonance (MR) imaging performed with a microscopy coil in the diagnosis of narrow anterior chamber angle in patients with glaucoma. Slit-lamp biomicroscopy served as the reference standard. The institutional review board approved this study, and written informed consent was obtained from the 20 recruited patients. There was excellent agreement between MR gonioscopy and slit-lamp biomicroscopy in the classification of anterior chamber angles as narrow or open (kappa = 0.89 [95% confidence interval: 0.69, 1.10]). MR gonioscopy has substantial potential as a technique used to evaluate glaucoma.