Toshimitsu Kasuga

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).

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.

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.

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.

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.

Hypothyroidism and Glaucoma in The United States

Purpose To investigate the association between hypothyroidism and glaucomatous disease. Methods This cross-sectional study included all subjects above the age of 40 years from two nationwide surveys: the 2008 National Health Interview Survey (NHIS) as well as the 2007 and 2008 National Health and Nutrition Examination Survey (NHANES). The presence or absence of glaucoma, thyroid disease and other demographic and health-related information including comorbidities was ascertained via interview. Blood samples were collected from NHANES subjects and analyzed for thyrotropin (TSH). Results A total of 13,599 and 3,839 NHIS and NHANES participants respectively were analyzed to assess for a possible relationship between self-reported glaucoma, and self-reported hypothyroidism as well as self-reported thyroid disease. The unadjusted odds ratio (OR) for NHIS showed a significant association between self-reported glaucoma and self-reported hypothyroidism (OR 1.46, 95% confidence interval [CI] 1.07-1.99). Multivariate logistic regression analysis adjusted for age, gender, race, comorbidities, and health-related behavior, however, showed no association between self-reported glaucoma and hypothyroidism or thyroid disease in both surveys (OR 1.60, 95%CI 0.87-2.95 for NHIS; OR 1.05, 95%CI 0.59-1.88 for NHANES). Conclusion A previously reported association between hypothyroidism and glaucomatous disease was not confirmed in two large U.S. health survey populations. While such an association was noted in the univariate analysis for the NHIS survey, such a relationship was not found in the multivariate analysis after adjustment for potential confounding variables.

Correlation between central corneal thickness and myopia in Taiwan

The aim of the study was to explore the correlation between central corneal thickness (CCT) and the degree of myopia in Taiwanese adults. A total of 528 individuals were enrolled to undergo myopic laser refractive surgery from January 2004 to December 2006. Preoperative CCT was measured using the Orbscan corneal topography system and refractive status was determined by cycloplegic spherical equivalent. The relationship between CCT and refractive error was investigated by interindividual and intraindividual analyses. Participants had a mean age of 34.8 ± 7.3 years, and 79.9% were female. The mean refractive error was -7.27 ± 2.96 diopters and the mean CCT measurement was 560 ± 35 μm. CCT revealed that there was no association with age. However, CCT was significantly (p = 0.012) less in females than in males. The CCT also showed no significant association with refractive error (p = 0.49). Among the 67 participants with myopic anisometropia, the mean difference between both eyes was 3.09 ± 1.06 diopters. There was no association between the intereye CCT difference and refractive error (p = 0.57). The results remained the same after adjusting for age and sex. In conclusion, there was no correlation between CCT and the degree of myopia among adults in Taiwan. These data might contribute to the ongoing discussion about the role of CCT in the higher incidence of development and progression of glaucoma in myopic individuals.

Ethnic Variation in Optic Disc Size by Fundus Photography

Abstract Purpose: To compare optic disc size among Caucasian, Chinese, African, Filipino and Hispanic subjects recruited from a university-based general ophthalmology clinic. Methods: In this retrospective cross-sectional study, optic disc size was calculated from fundus photographs. Differences in age, sex and spherical equivalent among the ethnic groups were examined with either Kruskal--Wallis test or Chi-square test. Ethnic differences in optic disc size were evaluated with linear mixed-effects regression models that adjusted for age, sex, spherical equivalent, glaucoma status, lens status and use of both eyes in the same subject. Results: Five hundred and seventy-four eyes of 305 subjects were analyzed. The mean and standard deviation of the optic disc size were 2.16 ± 0.41 mm2 for Caucasian, 2.30 ± 0.56 mm2 for Chinese, 2.31 ± 0.41 mm2 for Filipino, 2.38 ± 0.40 mm2 for African and 2.40 ± 0.38 mm2 for Hispanic subjects. Age and spherical equivalent differed among the ethnic groups by Kruskal--Wallis test (p < 0.05). Sex differed among the ethnic groups by Chi-square test (p < 0.05). Ethnic differences in optic disc size were not observed among African, Hispanic, Filipino and Chinese subjects in linear mixed-effects regression analyses (p > 0.05). However, Caucasian differed from the other ethnicities in linear mixed-effects regression analyses (p < 0.05). Conclusions: Optic disc size was significantly smaller in Caucasian compared to the other ethnic groups. Optic disc size differences among non-Caucasian ethnic groups were not significant.

Intraocular pressure reduction after cataract extraction in normal eyes: influence of ethnicity and anterior segment parameters - response.

We thank Ngo and Tan for their interest in our article examining the effect of ethnicity and anterior segment parameters on intraocular pressure (IOP) reduction following phacoemulsification cataract extraction.1 It has been brought to our attention that a prior study by Pohjalainen et al. reported IOP reduction by a mean of 13.2% at four months, and 21.2% at the final follow up visit, which occurred between 1 to 2.7 years after surgery.2 These results suggest that peak IOP lowering effect may occur after 3 months. We agree that potential differences in IOP reduction between ethnic groups might manifest later than 3 months postoperatively and a more extensive follow up schedule is warranted to confirm our findings. In addition to a more extensive follow up schedule, future studies should also examine the association between ethnicity and phacoemulsification-induced changes in anterior segment parameters that have not been examined in our study, such as iris thickness, iris curvature, pupil diameter, anterior chamber area, and anterior chamber width. In addition, Ngo and Tan describe results from their patients in which IOP reduction is not greater in narrow versus open angle subjects. Our study, as well as prior studies, has supported the idea that improved access to the trabecular meshwork—i.e., greater opening of the angle—is the main mechanism by which IOP is reduced.3 However, the findings from Ngo and Tan support an alternative theory that enhanced function of the trabecular meshwork may play a role in IOP reduction following phacoemulsification. Wang et al. demonstrated that interleukin-1 alpha could be induced by phacoemulsification ultrasound energy.4 Interleukin-1 alpha, an inflammatory cytokine, has been shown to decrease IOP in human anterior segment tissue culture.5 Therefore, IOP reduction following phacoemulsification may be only partially mediated by anatomic changes in the anterior chamber. It is possible that IOP reduction after phacoemulsification is multifactorial.

Comparison of optic nerve head topography and retinal nerve fiber layer in eyes with narrow angles versus eyes from a normal open angle cohort - a pilot study.

Purpose: To compare the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) in eyes with narrow angles and normal intraocular pressure (IOP) to normal control eyes. Materials and methods: A total of 70 eyes of 52 subjects with narrow angles and 40 eyes of 34 normal subjects were enrolled. Narrow angle eyes were defined as the following: (i) the pigmented trabecular meshwork was not visible for ≥ 180° on gonioscopy, (ii) untreated IOP ≤ 21 mmHg, (iii) no peripheral anterior synechiae (PAS) was observed, and (iv) optic discs were without glaucomatous changes, defined as neuroretinal rim thinning, focal notching, disc hemorrhages, or focal RNFL defects. ONH and peripapillary RNFL imaging were obtained with Heidelberg Retina Tomograph (HRT II) and Fourier-domain optical coherence tomography (RTVue OCT). Results: No significant difference was found in mean age between the two groups (p = 0.06), but the narrow angle group had significantly more women (p = 0.04). The narrow angle group had significantly higher IOP and smaller mean angle width (both p < 0.001). Vertical cup-to-disc ratio (VCDR) was significantly larger in the narrow angle group (p = 0.02). In visual field (VF) results, the mean deviation (MD) was significantly lower and pattern standard deviation (PSD) was significantly higher in the narrow angle group (both p < 0.001). After adjusting for disc area, the RNFL thickness of the inferior-temporal region was significantly thinner in the narrow angle group (135 ± 21.7 µm) compared with normal group (149 ± 22.1 µm, p < 0.01). This finding remained significant after Bonferroni correction for multiple comparisons. Smaller angle width was a significant predictor of RNFL thinning in the inferior-temporal region (p < 0.001). Conclusion: These data suggest that eyes with narrow angles may develop glaucomatous optic nerve damage in the absence of IOP elevation during office hours.