Takeshi Kumagami

Acute Corneal Epithelial Change after Instillation of Benzalkonium Chloride Evaluated Using a Newly Developed in vivo Corneal Transepithelial Electric Resistance Measurement Method

Objective: Acute corneal permeability change after instillation of benzalkonium chloride (BAC) was evaluated using a newly developed in vivo corneal transepithelial electric resistance (TER) measurement method. Method: Corneal TER was measured by Ag/AgCl electrodes placed in the anterior aqueous chamber and on the cornea of live rabbit eyes. TER was measured and TER change after instillation of 0.05% BAC solution was monitored. After TER measurement, cornea was excised and fixed for transmission and scanning electron microscopy. For the control study, physiologic saline was used instead of BAC. Results: The TER of normal rabbit cornea was 602.3 ± 195.0 Ωcm2. TER decreased instantly after instillation of 0.05% BAC. In 5 s, TER decreased to 58.3 ± 5.2%. In 60 s, TER decreased to 18.5 ± 3.2%. At all time points, TER after instillation of 0.05% BAC was significantly lower than that of the control (p < 0.0001). Dissociation of tight junctions and the destruction of superficial cell membranes were observed under electron microscopy. Conclusion: Corneal epithelial change with increased permeability is rapid and intense after the instillation of highly concentrated BAC solution, accompanied by disorder of tight junctions and cell membranes of superficial cells. The newly developed in vivo corneal TER measurement method is suitable for assessing acute corneal change after drug instillation.

Evaluation of acute corneal barrier change induced by topically applied preservatives using corneal transepithelial electric resistance in vivo.

Purpose: We evaluated acute changes in corneal barrier function after instillation with preservatives using corneal transepithelial electric resistance (TER) in vivo and cytotoxicity tests in vitro. Methods: The corneal TER of live rabbits was measured using a volt-ohm meter and silver/silver chloride electrodes. The cornea was exposed to the preservatives benzalkonium chloride (BAC; 0.001%, 0.002%, 0.005%, 0.01%, and 0.02%), 0.04% paraben, 0.5% chlorobutanol, 0.005% chlorhexidine digluconate, 2% boric acid, and 0.01% ethylenediaminetetraacetic acid, and then changes in the TER were monitored for 60 seconds. Cultured normal rabbit corneal epithelial cells were exposed to the same preservatives for 60 seconds in vitro, and cell viability was evaluated using the WST-1 assay. Results: The TER instantly decreased and became significantly lower than the control within 10 seconds after instillation with 0.01% and 0.02% BAC (P < 0.01) and within 60 seconds after that with 0.005% BAC (P < 0.01). The TER decreased concomitantly with increasing BAC concentration. Cell viability after instillation with 0.005%, 0.01%, and 0.02% BAC for 60 seconds was significantly lower than that of the control (P < 0.0001). None of the other preservatives significantly altered the TER or cell viability. Decreases in the TER correlated with cell viability (r = 0.94, P < 0.0001). Conclusions: Instillation with BAC immediately disrupted the corneal epithelium. Corneal epithelial cell death is supposed to be associated with a decline in barrier function; thus, corneal TER measurement in vivo can assess the acute toxicity of preservatives added to ophthalmic drugs.

Influence of alkyl chain length of benzalkonium chloride on acute corneal epithelial toxicity.

Purpose: To evaluate acute corneal epithelial toxicity induced by benzalkonium chloride (BAC) homologs with different alkyl chain lengths using an in vivo electrophysiological method. Methods: BAC homologs with C12, C14, and C16 alkyl chain lengths were used at concentrations of 0.0025%, 0.005%, and 0.01%, respectively. Cytotoxicity of BAC homologs on the normal rabbit corneal epithelial cells was examined by using a WST-1 assay. Corneal transepithelial electrical resistance (TER) was measured in living Japanese white rabbits by 2 Ag/AgCl electrodes placed in the anterior aqueous chamber and on the cornea. TER changes were then evaluated after a 60-second exposure to these BAC homologs. Morphological changes in corneal epithelium after exposure to the BAC homologs were examined using scanning electron microscopy. The antimicrobial activity of BAC homologs against Escherichia coli was also assessed. Results: All BAC homologs caused cytotoxicity and corneal barrier dysfunction in a concentration-dependent manner. However, the degree of corneal toxicity differed among the BAC homologs. Based on cytotoxicity and TER measurement, C14-BAC caused the greatest corneal impairment followed in order of severity by mixed BAC/C16-BAC and C12-BAC. Scanning electron microscopy images indicated an intact corneal epithelium after exposure to 0.005% C12-BAC, whereas 0.005% C14-BAC damaged the epithelium. There were no remarkable differences noted in the antimicrobial activity among the BAC homologs. Conclusions: Acute corneal epithelial toxicity induced by BAC homologs depends on the alkyl chain length. Thus, the use of C12-BAC instead of commercially available BAC is potentially safer for patients undergoing ophthalmological pharmacotherapy.

Spontaneous dislocation of in-the-bag intraocular lens primarily in cases with prior vitrectomy:

Purpose To report cases of late onset spontaneous in-the-bag dislocation of the intraocular lens (IOL) and to compare these results with past reports. Methods We retrospectively studied 21 eyes of 18 patients with dislocation of the entire capsular bag containing the IOL. Gender, age, interval between original surgery and IOL dislocation, and the predisposing factors were examined. Cases occurring after trauma were excluded. Results The mean ± SD age of the 12 men (57.1%) and 9 women included in the study was 67.8±8.6 years at the time of the IOL removal procedure. The interval between the original surgery and the IOL dislocation was 7.9±8.6. Associated clinical conditions included vitrectomy in 8 eyes (40.0%) of 7 patients, high myopia in 3 eyes (14%) of 2 patients, uveitis in 2 eyes (9.5%) of 2 patients, retinitis pigmentosa in 2 eyes (9.5%) of 1 patient, and pseudoexfoliation in 1 eye (4.8%) of 1 patient. There was no identifiable associated condition in 2 eyes (9.5%) of 2 patients, who were comparatively younger than the other cases. This result differs from previously published reports that have found a higher frequency of pseudoexfoliation and lower frequency of prior vitrectomy. Conclusions In-the-bag IOL dislocation was frequently associated with prior vitrectomy and sometimes occurred without specific conditions.

Systemic factors influence the prognosis of diabetic macular edema after pars plana vitrectomy with internal limiting membrane peeling.

Background: To evaluate the prognostic factors for the best-corrected visual acuity (BCVA) and foveal average retinal thickness after vitrectomy with internal limiting membrane (ILM) peeling for diabetic macular edema. Design: Retrospective, single-center study. Participants: This study involved 31 eyes of 27 patients who had undergone vitrectomy with ILM peeling between January 2005 and March 2008. Methods: Relationships between preoperative systemic or ocular factors and BCVA or foveal average retinal thickness before and 6 months after the operation were evaluated. Main Outcome Measures: BCVA and foveal average retinal thickness before and 6 months after the operation. Results: The mean logarithm of the minimum angle of resolution improved from 0.84 ± 0.64 (mean ± standard deviation) preoperatively to 0.64 ± 0.38 six months postoperatively (p = 0.393). Foveal average retinal thickness significantly improved from 473 ± 146 µm preoperatively to 318 ± 108 µm 6 months after the operation (p < 0.0001). Preoperative foveal average retinal thickness was significantly thicker with cardiovascular disease or cerebral infarction (p = 0.0019) or cystoid macular edema (p = 0.0028), while preoperative BCVA was significantly lower when an epiretinal membrane (p = 0.042) was present. Foveal average retinal thickness at the 6-month follow-up was significantly thicker when patients had a higher body mass index (p = 0.0088), were not on dialysis (p = 0.012), or did not have proliferative diabetic retinopathy (p = 0.013). BCVA at the 6-month follow-up was significantly lower in the group with no history of diabetes treatment until diabetic retinopathy was found (p = 0.023) and in patients with a higher preoperative glycosylated hemoglobin (p = 0.033). Conclusions: Preoperatively, BCVA and foveal average retinal thickness were primarily associated with ocular factors, while they were strongly associated with systemic factors, postoperatively. Ocular factor improvements may be related to the surgical procedure.

Polyoxyethylene Hydrogenated Castor Oil Modulates Benzalkonium Chloride Toxicity: Comparison of Acute Corneal Barrier Dysfunction Induced by Travoprost Z and Travoprost

PURPOSE To determine the element that modulates benzalkonium chloride (BAC) toxicity by using a new electrophysiological method to evaluate acute corneal barrier dysfunction induced by travoprost Z with sofZia (Travatan Z(®)), travoprost with 0.015% BAC (Travatan(®)), and its additives. METHODS Corneal transepithelial electrical resistance (TER) was measured in live white Japanese rabbits by 2 Ag/AgCl electrodes placed in the anterior aqueous chamber and on the cornea. We evaluated corneal TER changes after a 60-s exposure to travoprost Z, travoprost, and 0.015% BAC. Similarly, TER changes were evaluated after corneas were exposed for 60 s to the travoprost additives ethylenediaminetetraacetic acid disodium salt, boric acid, mannitol, trometamol, and polyoxyethylene hydrogenated castor oil 40 (HCO-40) with or without BAC. Corneal damage was examined after exposure to BAC with or without travoprost additives using scanning electron microscopy (SEM) and a cytotoxicity assay. RESULTS Although no decreases of TER were noted after exposure to travoprost Z with sofZia and travoprost with 0.015% BAC, a significant decrease of corneal TER was observed after 0.015% BAC exposure. With the exception of BAC, no corneal TER decreases were observed for any travoprost additives. After corneal exposure to travoprost additives with BAC, HCO-40 was able to prevent the BAC-induced TER decrease. SEM observations and the cytotoxicity assay confirmed that there was a remarkable improvement of BAC-induced corneal epithelial toxicity after addition of HCO-40 to the BAC. CONCLUSIONS Travoprost Z with sofZia and travoprost with BAC do not induce acute corneal barrier dysfunction. HCO-40 provides protection against BAC-induced corneal toxicity.

Imaging of laser-photocoagulated diabetic microaneurysm with spectral domain optical coherence tomography.

Purpose: To analyze the morphology of microaneurysms before and after direct photocoagulation using spectral domain optical coherence tomography. Methods: In 13 eyes of diabetic patients who underwent focal photocoagulation for clinically significant macular edema, microaneurysms were evaluated before, immediately after, 1 month after, and 2 months after photocoagulation with spectral domain optical coherence tomography. The microaneurysms were also evaluated by fluorescein angiography and color fundus photography. The patients underwent focal photocoagulation for microaneurysm. Results: The microaneurysms before photocoagulation in spectral domain optical coherence tomography were observed as circular or elliptical structures with hyperreflective foci within vessel walls. Immediately after photocoagulation, the microaneurysms were changed to indistinct lesions with hyperreflectivity around the microaneurysms. Acoustic shadows developed on the choroidal side of the microaneurysms. If photocoagulation for microaneurysms was appropriately done, retinal changes were limited to within the inner retina around the microaneurysms and no changes were observed in retinal pigment epithelium. Within 2 months after photocoagulation, the microaneurysms changed into fine scars and the retinal structure normalized. Average retinal thickness of the fovea was 432 ± 70 &mgr;m before the procedure but reduced to 373 ± 84 &mgr;m at 2 months post surgery. Conclusion: Focal photocoagulation may be a less invasive method for treating microaneurysms, and spectral domain optical coherence tomography is useful for evaluating the efficacy of photocoagulation.

Glaucoma in Atomic Bomb Survivors

Radiation has been associated with increases in noncancerous diseases. An effect of low-dose radiation on the prevalence of clinically detected glaucoma has not been previously reported. We therefore investigated the prevalence of glaucoma in A-bomb survivors and its possible association with radiation dose. A total of 1,589 people who participated in the clinical examination program for A-bomb survivors at the Radiation Effects Research Foundation (RERF) between October 2006 and September 2008 and who had reconstructed radiation doses, were recruited into this cross-sectional screening study. The prevalence of glaucoma and its dose-response relationship to A-bomb radiation were measured. Each subject underwent an initial screening consisting of an interview and ophthalmological examination. Questionable cases with any indication of ocular disease, including glaucoma, were referred to local hospitals for more comprehensive evaluation. A diagnosis of glaucoma was made based on specific optic disc appearance, perimetric results and other ocular findings. Of 1,589 eligible people, we detected 284 (17.9%) cases of glaucoma overall, including 36 (2.3%) cases of primary open-angle glaucoma with intraocular pressure levels greater than 21 mmHg, 226 (14.2%) cases of normal-tension glaucoma and 25 (1.6%) cases of primary angle-closure glaucoma. Seven glaucoma risk factors were examined as potential confounders but only two needed to be included in the final model. Binary regression using a generalized estimating equation method, with adjustment for gender, age, city, cataract surgery or diabetes mellitus, revealed an odds ratio at 1 Gy of 1.31 (95% confidence interval 1.11–1.53, P = 0.001) in the case of normal-tension glaucoma, but no association for other types of glaucoma. The prevalence of normal-tension glaucoma may increase with A-bomb radiation dose, but uncertainties associated with nonparticipation (59% participation) suggest caution in the interpretation of these results until they are confirmed by other studies.

Comparison of Corneal Safety and Intraocular Pressure–Lowering Effect of Tafluprost Ophthalmic Solution with Other Prostaglandin Ophthalmic Solutions

PURPOSE The benzalkonium chloride (BAK) content of tafluprost ophthalmic solution (Tapros(®): tafluprost) has been reduced to balance corneal safety and preservative effectiveness (old formulation: 0.01%; new formulation: 0.001%). However, no reports have been published on its clinical effect. Therefore, we conducted a clinical research study to compare the safety of BAK-reduced tafluprost on the ocular surface with other prostaglandin ophthalmic solutions. METHODS This clinical study included 28 glaucoma patients (28 eyes) with a treatment history of latanoprost ophthalmic solution (Xalatan(®)) or travoprost ophthalmic solution (Travatan Z(®)), who presented with corneal epithelial disorders. The subjects were switched to BAK-reduced tafluprost, and its effect on the ocular surface was examined after 1 and 2 months of treatment [using fluorescein staining score, hyperemia, tear film breakup time, and intraocular pressure (IOP) lowering]. RESULTS In all analyzed subjects (N=27), the fluorescein staining score was significantly improved after switching to BAK-reduced tafluprost (P<0.0001). Conversely, the IOP-lowering effect was not notably changed. The subjects switched from latanoprost (n=10) showed significant improvement in fluorescein staining score (P<0.05) as well as in IOP lowering (P<0.01). The subjects switched from travoprost (n=17) also showed significant improvement in fluorescein staining score (P<0.001), but without a significant change in IOP lowering. CONCLUSIONS Tafluprost with reduced BAK has potential as a superior antiglaucoma drug, not only for its IOP-lowering effect, but also for its good corneal safety profile.

Injection Site and Pharmacokinetics After Intravitreal Injection of Immunoglobulin G

PURPOSE The aim of this study was to investigate whether the pharmacokinetics differ after immunoglobulin G (IgG) intravitreal injections are done in the different sites of the vitreous cavity of rabbit eyes. METHODS To examine the pharmacokinetics in the vitreous and the retina/choroid, fluorescein isothiocyanate-labeled IgG (5  μg/50  μL) was injected from the superior pars plana into the vitreous cavity of rabbit eyes. An original intravitreal injection guide was used to fix the tip of the injection needle, with the tip fixed in either the superior-anterior vitreous (superior group) or in the posterior vitreous (posterior group). At 1  h, 1, 4, and 7 days after injection, the eyes were enucleated and frozen. The vitreous was cut into superior, inferior, and posterior vitreous sections, whereas the retina/choroid was cut into superior, inferior, and posterior retina/choroid sections. The IgG concentrations in the vitreous and the retina/choroid sections were then determined. RESULTS In the posterior vitreous, the IgG concentration in the posterior group was significantly higher than that in the superior group at 1  h after injection (P < 0.05). However, 1 day after injection, no significant differences were noted between the 2 groups. At 4 days after injection, the drug was diffusely spread in both groups. In the posterior retina/choroid, the IgG concentration was essentially the same regardless of the injection site or the amount of time after injection. The IgG concentration in the superior retina/choroid was significantly higher in the superior group than in the posterior group at 1  h and 1 day after injection (P < 0.05). There were no differences noted between the 2 groups for the IgG concentrations in the 3 sections at 4 and 7 days after injection. CONCLUSIONS Intravitreally injected IgG remains in the area of the injection, with more than 1 day required for it to spread diffusely within the vitreous. In the posterior retina/choroid, results suggested that the concentration of IgG may be equal regardless of the injection site. In the superior retina/choroid area that was near the site of the injection, the concentration of drug tended to be higher.