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

Nasal trabeculo-ciliary angle and relative lens vault as predictors for intraocular pressure reduction following phacoemulsification

PURPOSE

To evaluate quantitative relationships between biometric measurements and expected intraocular pressure reduction following phacoemulsification.

DESIGN

A prospective, comparative clinical study.

METHODS

Forty nine candidates for phacoemulsification were included. Intraocular pressure was measured preoperatively and after 7 and 30 days. Ocular biometrics were measured using optical biometry and ultrasound biomicroscopy preoperatively and 1 month postoperatively.

RESULTS

Patients were sub-grouped into open-angle glaucoma (12 eyes), angle-closure glaucoma (18 eyes), and cataract-only groups (19 eyes). The mean intraocular pressure reduction was -1.67 ± 2.73, -13.11 ± 7.98, and -7.50 ± 3.58 mmHg in the cataract-only, angle-closure glaucoma, and open-angle glaucoma groups (p = 0.001). The delta-intraocular pressure at day 7 showed positive correlations with lens vault and relative-lens vault (p = 0.005 and 0.001). It showed negative correlations with lens position, relative-lens position, anterior chamber depth, aqueous depth, and nasal and temporal angles in addition to lens thickness, anterior vault, nasal trabeculo-ciliary angle, and temporal-trabeculo-ciliary angle at the end of the follow-up period. Regression analysis revealed significant associations between preoperative intraocular pressure and both nasal-trabeculo-ciliary angle and anterior vault (p = 0.038 and 0.019) and delta-intraocular pressure and both nasal-trabeculo-ciliary angle and relative-lens vault (p = 0.001 and ≤0.001) with an area under the curve of 0.71 for relative-lens vault. For every degree decrease in nasal-trabeculo-ciliary angle, there was an expected 0.33 mmHg intraocular pressure reduction with no expected change if nasal-trabeculo-ciliary angle decreased to <22°.

CONCLUSIONS

The relationship between anterior-segment-biometrics could determine intraocular pressure behavior after phacoemulsification. The preoperative nasal-trabeculo-ciliary angle and relative-lens vault could be significant predictors for postoperative intraocular pressure reduction.

Evaluation of Refractive Status and Ocular Biometric Parameters in Primary Angle Closure Disease

INTRODUCTION

The aim of the study was to evaluate the refractive status and ocular biometric parameters in subjects with angle closure in Malaysia.

METHODS

This cross-sectional study was conducted on 171 primary angle closure patients (268 eyes). Visual acuity, refraction, and ocular biometry (central anterior chamber depth [ACD], axial length [AL], and lens thickness) were recorded. Vitreous cavity length (VL) and relative lens position (RLP) were calculated.

RESULTS

A total of 92 Primary Angle Closure Suspect (PACS), 30 Primary Angle Closure (PAC), and 146 Primary Angle Closure Glaucoma (PACG) eyes were included. Chinese ethnicity formed the majority (n = 197, 73.5%), followed by Malay (n = 57, 21.3%) and Indian (n = 14, 5.2%). There was a significant female preponderance with a female to male ratio of 1.85. Mean age was 65.7 ± 7.7 years. Mean spherical equivalent was +0.33 ± 1.29 D. Approximately half (n = 137, 51%) of the eyes were hyperopic (spherical power ≥+0.5), with PACG having the highest percentage of hyperopia (n = 69, 50.4%). Myopia and emmetropia were present in 48 (17.9) and 83 (31%) eyes, respectively. Although AL and VL in myopia patients were significantly longer than emmetropic and hyperopic eyes (p < 0.001), the ACD was not significantly different (p = 0.427). While the RLP is smaller in myopic eyes, lens thickness was increased in hyperopic eyes. PACG was significantly higher in elderly patients compared to PACS and PAC (p = 0.005). A total of 37 (13.8%) eyes were blind (vision worse than 3/60) and 19 of them (51.3%) were female patients.

CONCLUSION

A decrease in RLP is predictive of angle closure disease in myopic eyes, whereas increased lens thickness contributes to angle closure disease in hyperopic eyes.

Effect of Visibility of the Ciliary Body Processes on Ocular Biometric Parameters in Patients with Primary Angle Closure

PURPOSE

To evaluate the differences in ocular biometric parameters between eyes with primary angle closure (PAC) with and without visible ciliary body processes (CBP) (PAC+CBP and PAC-CBP) and normal open-angle controls.

STUDY DESIGN

Cross-sectional study.

METHODS

Eyes with PAC and normal open-angle controls underwent detailed ocular examinations and gonioscopy to determine the visibility of the CBP. The following ocular biometric parameters were determined using A-scan ultrasound biometry: axial length (AL), anterior chamber depth (ACD), lens thickness (LT), and vitreous length (VL). The lens-axial length factor (LAF) and relative lens position (RLP) were also calculated. Continuous variables were assessed by analysis of variance with Bonferroni correction. Multiple linear regression analysis was performed to adjust for confounding factors. Area under the receiver operating characteristic curves were calculated to determine the diagnostic capability of biometric parameters.

RESULTS

84 PAC+CBP eyes, 57 PAC-CBP eyes, and 32 normal open angle control eyes were evaluated. The means of the ocular biometric values were significantly different among the three groups. AL, ACD, LT, VL, LAF, and RLP were also significantly different among the three groups in the multivariate regression analysis. AL, ACD, and VL were lower in the PAC+CBP group and LT, RLP, and LAF were greater in the PAC+CBP group than in the PAC-CBP and control groups. LAF ≥ 2.4 is the cutting point with the highest sensitivity and specificity to differentiate PAC+CBP from PAC-CBP.

CONCLUSIONS

The ocular biometric parameters in the PAC+CBP group were more strongly associated with a crowded anterior segment than in the other groups. Visibility of CBP in PAC-affected eyes may serve as a surrogate for an anterior segment crowding mechanism and help to select the most appropriate treatment in individual cases.

Ethnic differences in lens parameters measured by ocular biometry in a cataract surgery population

Purpose

To investigate whether differences exist in lens position and other lens parameters among major ethnic groups with cataractous eyes, which may help explain racial differences in angle closure risk.

Methods

This retrospective, cross-sectional study included 807 adult patients who had cataract surgery between years 2014 and 2016 at the University of California, San Francisco (UCSF). Adult patients of white, Asian, Hispanic and African-American ethnicity were included. Lens position (LP), defined as anterior chamber depth (ACD) + 1/2 lens thickness (LT), was assessed using measurements from optical biometry. Other assessed biometric parameters included axial length (AL), relative lens position (RLP) (defined as LP/AL), and anterior chamber depth (ACD).

Results

A total of 807 patients and 1361 eyes were included in this study from a database of patients having cataract surgery. Mean age was 69.2 years (age range from 18 to 101 years old), and 60.3% of patients were women. The mean LP measurements were 5.54±0.32 mm for white, 5.38±0.32 mm for Asian, 5.32±0.30 mm for Hispanic, and 5.40±0.28 mm for African-American participants. After adjusting for age, sex, and AL, significant differences were found when comparing LP in paired comparisons among White cohort with Asians (P<0.001), Hispanics (P<0.001) and African-Americans (P = 0.003). Additionally, when comparing RLP, similar significant results were found when comparing Whites with Asians (P<0.001), Hispanics (P<0.001) and African-Americans (P = 0.002). Lastly, pair-wise comparison of LT between ethnic groups showed significant differences while comparing Asians with Whites (P = 0.001) and Asians with African-Americans (P<0.001).

Conclusion

The results of this study suggest that the LP of Hispanic, Asian, and African-American patients are significantly smaller than that of White patients, and among all ethnic groups, Hispanics and after Asians have the smallest LP (P<0.001) and RLP (P<0.001). These findings may have implications for the relative risk of angle closure and the potential IOP response after cataract surgery among different ethnic groups.

Comparison of slit lamp-adapted optical coherence tomography features of fellow eyes of acute primary angle closure and eyes with open angle glaucoma

PURPOSE

The aim of this study was to assess the possibility of discriminating a narrow and occludable chamber angle by means of digital gonioscopy.

METHODS

In a prospective controlled clinical study 40 eyes of 40 patients were enrolled. 20 patients that had suffered acute angle closure glaucoma (ACG) on the fellow eye were compared to 20 patients with open angle glaucoma (OAG). Anterior segment imaging with SL-OCT (Heidelberg Engineering, Heidelberg, Germany) enabled the delineation, by means of automatic signal analysis, of several important parameters of the anterior chamber angle region, which were compared to those revealed from direct contact glass gonioscopy and ultrasound biometry.

RESULTS

The anterior segment structures were automatically recognized by the SL-OCT software in 70 % of the ACG patients and in all of the OAG cases (100 %) (p = 0.025). Anterior chamber angle (ACA) was 15.55° ± 6.92° in the ACG group and 34.6° ± 8.9° in the OAG group, whereas angle opening distance (AOD) was 199.55 ± 62.29 μm in ACG and 452.67 ± 123.91 μm in OAG. A good correlation was found in the direct gonioscopic findings (r = 0.85, p < 0.001), but there were significant differences between both groups (p < 0.001). Mean real central anterior chamber depth (rACD) was evaluated to be 1.75 and 2.79 mm in ACG and OAG, respectively, showing a significant difference (p < 0.0001) and the highest (although not statistically significant) sensitivity and specificity above all other parameters tested in discriminating between OAG and ACG eyes. Discrimination criteria revealed a relevant narrowing of the anterior chamber angle region for values below 22° (ACA), 276 μm (AOD) and 2.08 mm (rACD).

CONCLUSIONS

Digital gonioscopy by means of SL-OCT allowed a non-invasive and objective imaging of the anterior chamber configuration that could be used as a screening method for narrow and occludable angles. The method could contribute to a timely identification of angle closure and alert clinicians to further determine whether a peripheral iridotomy should be performed.