Qi N. Cui

Association between Baseline Iris Thickness and Prophylactic Laser Peripheral Iridotomy Outcomes in Primary Angle-Closure Suspects

OBJECTIVE To evaluate the association between baseline measurements of iris thickness at 3 positions and change in anterior segment biometric parameters after prophylactic laser peripheral iridotomy (LPI). DESIGN Prospective clinical cohort study. PARTICIPANTS Fifty-two eyes of 52 nonglaucomatous subjects with anatomically narrow angles. METHODS Anterior segment optical coherence tomography (ASOCT) images captured before and after LPI were analyzed using customized software, the Zhongshan Angle Assessment Program (ZAAP) (Zhongshan Ophthalmic Centre, Guangzhou, China). Differences in preoperative and postoperative measurements for anterior segment biometric parameters were compared by paired Student t tests. Multivariate linear regression models, adjusted for age, sex, ethnicity, and preoperative pupil diameter, were used to examine the association between the baseline measurements of iris thickness at 3 positions and the change in anterior segment biometric parameters after LPI. MAIN OUTCOME MEASURES Baseline iris thickness measured at 750 μm from the scleral spur (IT750), iris thickness measured at 2000 μm from the scleral spur (IT2000), and maximal iris thickness (ITM). Changes in iris curvature (ICURV) and trabecular-iris space area at 500 μm from the scleral spur (TISA500) and 750 μm from the scleral spur (TISA750) after LPI. RESULTS The ICURV significantly decreased, whereas TISA500 and TISA750 significantly increased after LPI (all P < 0.0001). Lower baseline IT750 was significantly associated with greater postoperative increases in TISA500 and TISA750 (both P < 0.05). Lower baseline IT2000 and ITM were significantly associated with greater postoperative decrease in ICURV (both P < 0.05). CONCLUSIONS Our results showed that lower baseline measurements of iris thickness are associated with greater decrease in ICURV and increases in TISA500 and TISA750 after LPI. This suggests that eyes with thinner irides undergoing LPI were more likely to exhibit greater magnitude of change in terms of flattening of the iris convexity (i.e., ICURV) and widening of the anterior chamber angle (i.e., TISA500 and TISA750).

Perception of Auditory, Visual, and Egocentric Spatial Alignment Adapts Differently to Changes in Eye Position

Vision and audition represent the outside world in spatial synergy that is crucial for guiding natural activities. Input conveying eye-in-head position is needed to maintain spatial congruence because the eyes move in the head while the ears remain head-fixed. Recently, we reported that the human perception of auditory space shifts with changes in eye position. In this study, we examined whether this phenomenon is 1) dependent on a visual fixation reference, 2) selective for frequency bands (high-pass and low-pass noise) related to specific auditory spatial channels, 3) matched by a shift in the perceived straight-ahead (PSA), and 4) accompanied by a spatial shift for visual and/or bimodal (visual and auditory) targets. Subjects were tested in a dark echo-attenuated chamber with their heads fixed facing a cylindrical screen, behind which a mobile speaker/LED presented targets across the frontal field. Subjects fixated alternating reference spots (0, +/-20 degrees ) horizontally or vertically while either localizing targets or indicating PSA using a laser pointer. Results showed that the spatial shift induced by ocular eccentricity is 1) preserved for auditory targets without a visual fixation reference, 2) generalized for all frequency bands, and thus all auditory spatial channels, 3) paralleled by a shift in PSA, and 4) restricted to auditory space. Findings are consistent with a set-point control strategy by which eye position governs multimodal spatial alignment. The phenomenon is robust for auditory space and egocentric perception, and highlights the importance of controlling for eye position in the examination of spatial perception and behavior.

Association between baseline angle width and induced angle opening following prophylactic laser peripheral iridotomy.

PURPOSE To evaluate the association between baseline angle width and laser peripheral iridotomy (LPI)-induced opening of the anterior chamber angle. METHODS Anterior segment optical coherence tomography images captured before and after LPI were analyzed to determine the angle opening distance at 250 μm (AOD250), 500 μm (AOD500), and 750 μm (AOD750) from the scleral spur; trabecular-iris space area at 500 μm (TISA500) and 750 μm (TISA750) from the scleral spur; angle recess area at 750 μm (ARA750) from the scleral spur; and trabecular-iris angle (TIA). Differences in preoperative and postoperative measurements for the anterior chamber angle width parameters were compared by paired Students t-tests. Univariate and linear mixed-effects regression models were used to examine the association between baseline and LPI-induced opening of anterior chamber angle width parameters. RESULTS Eighty-four eyes of 52 primary angle closure suspects were included in the analysis. AOD250, AOD500, AOD750, TISA500, TISA750, ARA750, and TIA significantly increased following LPI by paired Students t-tests (all P < 0.0001). Lower baseline measurements were significantly associated with greater postoperative opening in all anterior chamber angle width parameters in both univariate and linear mixed-effects regression analyses (all P < 0.05). CONCLUSIONS Our results showed significant opening of the anterior chamber angle width after LPI and demonstrated an inverse association between baseline and LPI-induced opening of the anterior chamber angle width, such that eyes with a more crowded anterior chamber angle undergoing LPI had a greater magnitude of increase in anterior chamber angle width after the procedure.

Association of Lens Vault with Narrow Angles among Different Ethnic Groups

Purpose: To compare lens vault between open-angle and narrow-angle eyes in African-, Caucasian-, Hispanic-, Chinese- and Filipino-Americans. Methods: In this prospective study, 436 patients with open angle and narrow angle based on the Shaffer gonioscopic grading classification underwent anterior-segment optical coherence tomography. The Zhongshan Angle Assessment Program was used to calculate lens vault. The narrow-angle group included 32 Chinese-Americans, 22 Filipino-Americans, 26 African-Americans, 24 Hispanic-Americans and 73 Caucasian-Americans. The open-angle group included 56 Chinese-Americans, 29 Filipino-Americans, 45 African-Americans, 27 Hispanic-Americans and 102 Caucasian-Americans. Linear mixed effect regression models, accounting for the use of both eyes and adjusting for age, sex, pupil diameter and spherical equivalent, were used to test for the ethnicity and angle coefficients. Tukey’s multiple comparison test was used for pairwise comparisons among the open-angle racial groups. Results: Significant difference in lens vault was found among the open-angle racial groups (P = 0.022). For the open-angle patients, mean values for the lens vault measurements were 265 ± 288 µm for Chinese-Americans, 431 ± 248 µm for Caucasian-Americans, 302 ± 213 µm for Filipino-Americans, 304 ± 263 µm for Hispanic-Americans and 200 ± 237 µm for African-Americans. Using Tukey’s multiple comparison for pairwise comparisons among the open-angle racial groups, a significant difference was found between African-American and Caucasian-Americans groups (P < 0.001). P values for the rest of the pairwise comparisons were not statistically significant. No significant difference was found among the narrow-angle racial groups (P = 0.14). Comparison between the open angle and narrow angle within each racial group revealed significant difference for all racial groups (P < 0.05). Conclusion: Among all the ethnicities included in this study, narrow-angle eyes have greater lens vault compared to open-angle eyes. With the exception of the comparison between African-Americans and Caucasian-Americans, differences in lens vault measurements among the racial groups with open angle were statistically insignificant. Our data suggest that other factors may play a greater role in predisposing Asian races to angle closure.

Ethnic differences in intraocular pressure reduction and changes in anterior segment biometric parameters following cataract surgery by phacoemulsification

To determine the association between ethnicity and changes in intraocular pressure and anterior segment biometric parameters following cataract surgery by phacoemulsification in nonglaucomatous subjects.

Eye position and cross-sensory learning both contribute to prism adaptation of auditory space.

Optical prisms shift visual space, and through adaptation over time, generate a compensatory realignment of sensory-motor reference frames. In humans, prism-induced lateral shifts of visual space produce a corresponding shift in sound localization. We recently reported that sound localization shifts towards eccentric eye position, approaching approximately 40% of gaze over several minutes. Given that eye position affects sound localization directly, prism adaptation may well reflect contributions of both eye position and sensory adaptation; while the visual world is shifted by the prisms, the eyes must also shift simply to gaze ahead. To test this new concept of prism adaptation, 10 young (18-27 year) adults localized sound targets before and after 4 h of adaptation to base-right or base-left prisms that induced an 11.4 degrees shift left or right, respectively. In separate sessions subjects were exposed to: (1) natural binaural hearing; (2) diotically presented inputs devoid of meaningful spatial cues; or (3) attenuated hearing to simulate hearing loss. These preliminary results suggest that the prism adaptation of auditory space is dependent on two independent influences: (1) the effect of displaced mean eye position induced by the prisms, which occurs without cross-sensory experience; and (2) true cross-sensory learning in response to an imposed offset between auditory and visual space.

Comparison of anterior segment morphology following prophylactic laser peripheral iridotomy in Caucasian and Chinese eyes

To compare anterior segment biometric parameters between Caucasians and Chinese before and after laser peripheral iridotomy.

Advancing age alters the influence of eye position on sound localization

Vision and audition provide spatial information about the environment to guide natural behavior. Because the eyes move in the head while the ears remain head-fixed, input conveying eye position in the head is required to maintain audiovisual congruence. Human perception of auditory space was previously shown to shift with changes in eye position, regardless of the target’s frequency content and spatial cues underlying horizontal and vertical localization. In this study, we examined whether this interaction is altered by advancing age. Head-restrained young (18–44 yo), middle-aged (45–64 yo), and elderly (65–81 yo) human subjects localized noise bursts under conditions of transient and sustained ocular deflection. All three age groups demonstrated a time-dependent shift of auditory space in the direction of eye position. Moreover, this adaptation showed a clear decline with advancing age, but only for peripheral auditory space (beyond ±10° from midline). Alternatively, adaptation in the periphery may occur, but is more sluggish than in the central field and therefore not fully observed in this experiment. The age-dependent effect cannot be readily explained by senescent peripheral hearing loss, suggesting a change in central processing of auditory space in relation to the control of gaze.

The Effect of Cumulative Dissipated Energy on Changes in Intraocular Pressure After Uncomplicated Cataract Surgery by Phacoemulsification.

Purpose:To investigate the association between ultrasound energy, expressed as cumulative dissipated energy (CDE), and changes in intraocular pressure (IOP) after uncomplicated cataract surgery by phacoemulsification. Methods:In this prospective study, nonglaucomatous subjects underwent cataract surgery by phacoemulsification. IOP was compared by clustered linear regression at 4 separate time-points: preoperative, 1 day, 1 month, and 3 months after cataract surgery. Changes in the IOP were evaluated as a function of CDE using univariate and multivariate clustered linear regression models, which adjusted for sex, ethnicity, age, axial length, spherical equivalent, mean preoperative Shaffer gonioscopy grade of all 4 quadrants, cataract grade, preoperative IOP, central corneal thickness, and use of both eyes in the same subject. Results:One hundred sixty-one eyes (89 Asian, 49 white, 12 African, and 11 Hispanic) from 116 nonglaucomatous subjects were analyzed. The 161 eyes included 81 right and 80 left eyes. The 89 Asian eyes included 46 Chinese, 35 Filipino, and 8 Vietnamese. Preoperative IOP was 14.9±3.2 mm Hg. Postoperative IOP significantly increased to 16.0±4.9 mm Hg at 1 day (P=0.037) and decreased to 12.4±3.1 and 12.3±3.0 mm Hg at 1 and 3 months, respectively (both P<0.0001). IOP changes at 1 day, 1 month, and 3 months did not demonstrate significant associations with CDE measurements in either univariate or multivariate clustered linear regression analyses (all P>0.05). Conclusions:The amount of ultrasound energy delivered to the eye during phacoemulsification, expressed as CDE, was not associated with postoperative changes in IOP.

Effect of mitomycin c and 5-flurouracil adjuvant therapy on the outcomes of Ahmed glaucoma valve implantation.

To examine the effect of mitomycin c and 5‐flurouracil on treatment outcomes following Ahmed glaucoma valve implantation.