Kazuaki Kadonosono

Treatment of retinal detachment resulting from myopic macular hole with internal limiting membrane removal

PURPOSEnTo examine the efficacy of vitrectomy with internal limiting membrane removal for retinal detachment resulting from a macular hole in highly myopic eyes.nnnMETHODSnEleven consecutive highly myopic eyes (11 patients) with retinal detachment resulting from a macular hole were treated by vitrectomy with removal of the internal limiting membrane, which was stained with indocyanine green and sulfur hexafluoride gas injection. Postoperatively, the patients were instructed to remain prone for 2 weeks. The excised specimens were evaluated with transmission electron microscopy.nnnRESULTSnThe mean postoperative follow-up was 9.2 +/- 2.3 months (range, 7 to 13 months). In 10 of the 11 eyes (91%) the retina was reattached during the initial surgery. Redetachment occurred in one eye, which was successfully treated during the second surgery. Best-corrected visual acuity improved in all eyes and ranged from 20/400 to 20/50. Pathologic examination showed that the internal limiting membrane and epiretinal tissues were present in all specimens.nnnCONCLUSIONSnThe use of indocyanine green staining can facilitate removal of a macular internal limiting membrane and overlying epiretinal membrane, resulting in complete relief of the macular traction. Primary removal of the internal limiting membrane may contribute to a high initial success rate for retinal reattachment and be an important adjuvant to the treatment of retinal detachment resulting from a macular hole in highly myopic eyes.

Perifoveal microcirculation before and after vitrectomy for diabetic cystoid macular edema

PURPOSEnTo quantify the perifoveal microcirculation in diabetic eyes before and after successful vitreous surgery for cystoid macular edema without posterior vitreous detachment, and to determine whether improvement in perifoveal microcirculation is associated with improvement in postoperative visual acuity.nnnMETHODSnIn a prospective study, vitreous surgery was performed on 11 eyes of nine consecutive diabetic patients with cystoid macular edema, and their mean perifoveal capillary blood flow velocity was measured by fluorescein angiography with a scanning laser ophthalmoscope. Visual acuity was measured preoperatively and postoperatively, and the results were converted to the logarithm of the minimum angle of resolution (logMAR). The correlation between changes in logMAR visual acuity and capillary blood flow velocity was evaluated.nnnRESULTSnIn all nine eyes of seven patients with successful vitreous surgery, the cystoid macular edema resolved within 6 months after surgery, and the mean capillary blood flow velocity was significantly increased compared with that before surgery (2.19 mm per second versus 2.68 mm per second, P =.021); the changes in capillary blood flow velocity were significantly correlated with the changes in the logMAR visual acuity (P =.024).nnnCONCLUSIONSnVitreous surgery may improve perifoveal microcirculation in the eyes of diabetic patients with cystoid macular edema and resolve the macular edema. Improvement of perifoveal microcirculation may be an important factor affecting visual outcome.

Effect of intracameral anesthesia on the corneal endothelium

Purpose: To evaluate the effects of intracameral anesthesia on the corneal endothelium. Setting: Department of Ophthalmology, Yokohama City University School of Medicine, Yokohama, Japan. Methods: This study comprised 24 eyes of 12 white rabbits. One eye of 3 rabbits each was injected with preservative‐free lidocaine at concentrations of 0.02, 0.2, or 2% and the fellow eye injected with balanced salt solution (BSS®) as a control. The anesthetic agent was injected into the anterior chamber using a bimanual technique. Immediately after enucleation, the cornea was examined by scanning electron microscopy. Results: Scanning electron microscopy revealed no abnormal findings in the eyes injected with lidocaine 0.02 or 0.2% when compared with eyes in the control group. Scanning electron microscopy of the eyes injected with lidocaine 2% showed irregular hexagonal endothelial cells and a significant loss of microvilli. Conclusion: Intracameral anesthesia with high concentrations of lidocaine risks corneal endothelial damage but at the low concentration usually used in cataract surgery did not appear to have an adverse effect. J Cataract Refract Surg 1998; 24:1377‐1381

Expression of matrix metalloproteinase-7 in choroidal neovascular membranes in age-related macular degeneration

PURPOSEnMatrix metalloproteinases are a family of extracellular matrix-degrading enzymes associated with neovascularization. We evaluated the expression and localization of matrix metalloproteinase-7 in choroidal neovascular membranes in age-related macular degeneration.nnnMETHODSnImmunofluorescence and transmission electron microscopic examinations were performed on subfoveal neovascular membranes that had been surgically removed from seven eyes of seven patients with age-related macular degeneration.nnnRESULTSnMatrix metalloproteinase-7 was expressed in all specimens and distinctly expressed in the thickened layer of Bruch membrane and basement membrane-like structure around retinal pigment epithelial cells.nnnCONCLUSIONSnMatrix metalloproteinase-7 was expressed in Bruch membrane of choroidal neovascular membranes in age-related macular degeneration. Matrix metalloproteinase-7 may be an important factor for the development of the submacular neovascular membrane in age-related macular degeneration.

Simulation of air-bag impact on post-radial keratotomy eye using finite element analysis

Purpose: To determine the physical and mechanical conditions of an impacting air bag that causes corneal rupture in a post‐radial keratotomy (RK) eye using a simulation model of the human eye. Setting: Numerical simulation study on a computer. Methods: The simulations were performed by a computer using the finite element analysis program PAM‐CRASH (Nihon ESI). The air bag was set to impact the surface of a post‐RK eye with 4, 6, or 8 corneal incisions at various velocities. Strain on the corneal tissue including scarred incisions exceeding 9.0% was assumed to indicate the possibility of corneal rupture. Results: At a medium velocity of 30 m/s, corneal rupture was likely to occur. At an air‐bag impact velocity of 40 m/s, 3 of 4, 5 of 6, and 8 of 8 incisions were likely to rupture in the case of 4‐, 6‐, and 8‐incision procedures, respectively, leading to likely globe rupture in all situations. Lacerations extended beyond the incisions and involved the intact cornea at a velocity of 40 m/s. If the corneal tissue strength reduction was increased to 90%, most incisions were likely to rupture at impact velocities greater than 35 m/s in all incision procedures. Conclusions: The results could partly reflect a reported case of globe rupture after RK and suggest that severe ocular trauma can be caused in the post‐RK eye by air bags at ordinary impact velocities.

Simulation of airbag impact on eyes after photorefractive keratectomy by finite element analysis method

BackgroundA simulation model of the human eye which we have developed was applied to simulated airbag ocular injury, to determine the physical and mechanical conditions of the impacting airbag that would cause globe rupture in a post-photorefractive keratectomy (PRK) eye.MethodsSimulations were performed with a computer using the finite element analysis program PAM-CRASH(Nihon ESI, Tokyo, Japan). The airbag was set to impact on the surface of post-PRK eyes—D3, D6, D10, and D15—and an intact eye at various impact velocities. Strain on the cornea and sclera exceeding 18.0% and 6.8%, respectively, was assumed to indicate the possibility of rupture of each tissue.ResultsIn contrast to the intact eye, in post-PRK eyes, at the lowest velocity of 20xa0m/s, some of the element reached the strain threshold in D15. At the medium velocity of 30xa0m/s, limited corneal rupture was observed in all situations. At the high velocity, 40xa0m/s, scleral laceration was found in eyes with all diopters, and apparent corneal rupture was observed in D10 and D15, indicating that globe rupture was very likely to occur.ConclusionThese results suggest that severe ocular trauma can be caused in post-PRK eyes by airbags at high impact velocities. Preoperative discussion with candidates for laser refractive surgery regarding the potential for severe ocular injury if the normal integrity of the eye is compromised by surgery may be appropriate. Research on modification of airbag design and deployment to minimize the risk of ocular injury is important.

A2e mediated phototoxic effects of endoilluminators

Aims: To compare the theoretical retinal threshold time for endoilluminators and experimental phototoxic effect using A2e laden retinal pigment epithelial (RPE) cells. Methods: The spectral irradiances of three types of 20 gauge and 25 gauge endoilluminators, currently commercially available from two manufacturers, were evaluated in conditions where the total beam spectral power was divided by the beam spot size at an estimated use distance of 5 mm from the retina. The retinal threshold time was calculated using the guidelines recommended by the International Commission on Non-Ionizing Radiation Protection. In vitro, A2e laden cells were evenly exposed to light for 30 minutes with a standard endoilluminator positioned 1 cm above the cells and the cell viability was assessed by WST-1 assay. Results: The retinal threshold times were within 1 minute for all the endoilluminators tested. A significant decrease in the viability of A2e laden RPE cells was observed after they were exposed to light from two of the three 20 gauge endoilluminators. Cell viability was not affected by the exposure to 25 gauge endoilluminators under the same conditions. There was no correlation between the theoretical threshold times and experimental data. Conclusions: Light exposure during vitrectomy can induce photochemical damage to the retina. Although the A2e laden RPE model may not correctly mimic a clinical situation, this model may be useful to estimate the possible photochemical damage to RPE cells that could not be deduced by a theoretical retinal hazard model.

Evaluation of the safety of xenon/bandpass light in vitrectomy using the A2E-laden RPE model

BackgroundThe purpose of the study was to investigate the brightness of the xenon/bandpass light in vitrectomy and assess its phototoxic effects using A2E-laden retinal pigment epithelial (RPE) cells.MethodsThe total luminous flux and spectral irradiance of 20- and 25-gauge endoilluminators connected to xenon lamps were measured and compared to those of 20- and 25-gauge endoilluminators connected to a halogen lamp. In vitro, A2E-laden cells were evenly exposed to xenon/bandpass light for 5 to 30 min positioned at 1xa0cm and 2xa0cm for a standard light probe and an implantable “chandelier” light probe, respectively, above the cells, and the cell viability was assessed using WST-1 assay. The cell viability was compared with cells exposed to 30 min of halogen light projected through a 20-gauge endoilluminator.ResultsThe maximal total luminous flux of xenon/bandpass light emitted through the 20-gauge endoilluminator was 2.8 times higher than that of the halogen light. The total luminous flux of the 25-gauge endoilluminators was 0.6-1.1 times greater than the 20-gauge endoilluminators connected to the halogen light. The viability of the A2E-laden cells after exposure to the xenon/bandpass light was no different than that of the cells exposed to the halogen light when the total luminous flux of these lights was at the same level. Xenon/bandpass light from an implantable “chandelier” light probe induced A2E-mediated RPE damage to a similar extent as that of the halogen light through a 20-gauge endoilluminator.ConclusionsA2E-mediated phototoxicity of xenon/bandpass light is comparable to that of halogen light.

Simulation of air-bag impact on an eye with transsclerally fixated posterior chamber intraocular lens using finite element analysis

Purpose: To determine the physical and mechanical conditions of an impacting air bag that would rupture an eye with a transsclerally fixated posterior chamber intraocular lens (IOL). Setting: Numerical simulation study on a computer. Methods: Simulations in a model human eye were performed with a computer using the finite element analysis program PAM‐CRASH (Nihon ESI). The air bag was set to impact the surface of an eye with a transsclerally fixated posterior chamber IOL at various velocities. The tensile force limit of a 10‐1 polypropylene suture was assumed to be 0.16 N, which is specified in the U.S. Pharmacopeia XXII. Results: At the lowest velocity of 20.0 m/s, 10‐0 polypropylene sutures were not likely to break. Sutures fixating the IOL might break and a corneoscleral incision was likely to open after 0.3 second at the medium impacting velocity (30 m/s). Suture rupture was very likely at the highest velocity (40 m/s) since the tensile force on the sutures continuously exceeded the breaking force after the impact. Conclusions: In an eye with a transsclerally fixated posterior chamber IOL, severe ocular trauma can be caused by an air bag at high velocity. Small individuals such as elderly women are at greater risk for air‐bag ocular injury. Further research on modifying air‐bag design and deployment is important to minimize the risk for ocular injury.

Low-frequency coding variants in CETP and CFB are associated with susceptibility of exudative age-related macular degeneration in the Japanese population.

Age-related macular degeneration (AMD) is a major cause of blindness in the elderly. Previous sequencing studies of AMD susceptibility genes have revealed the association of rare coding variants in CFH, CFI, C3 and C9 in European population; however, the impact of rare or low-frequency coding variants on AMD susceptibility in other populations is largely unknown. To identify the role of low-frequency coding variants on exudative AMD susceptibility in a Japanese population, we analysed the association of coding variants of 34 AMD candidate genes in the two-stage design by a multiplex PCR-based target sequencing method. We used a total of 2,886 (1st: 827, 2nd: 2,059) exudative AMD cases including typical AMD, polypoidal choroidal vasculopathy, and retinal angiomatous proliferation and 9,337 (1st: 3,247 2nd: 6,090) controls. Gene-based analysis found a significant association of low-frequency variants (minor allele frequency (MAF)u2009<u20090.05) in CETP, C2 and CFB. The association of CETP remained after conditioned with all known genome-wide association study (GWAS) associated variants. In addition, when we included only disruptive variants, enrichment of rare variants (MAFu2009<u20090.01) was also observed after conditioned with all GWAS associated variants (Pu2009=u20091.03u2009×u200910−6, odds ratio (OR)u2009=u20092.48). Haplotype and conditional analysis of the C2-CFB-SKIV2L locus showed a low-frequency variant (R74H) in CFB would be individually associated with AMD susceptibility independent of the GWAS associated SNP. These findings highlight the importance of target sequencing to reveal the impact of rare or low-frequency coding variants on disease susceptibility in different ethnic populations.