Toshihiko Shiwa

Functional evaluation of corneal endothelium by combined measurement of corneal volume alteration and cell density after phacoemulsification.

PURPOSE: To assess a new method of functional evaluation of corneal endothelium using combined measurement of corneal volume alteration and cell density (CD) after phacoemulsification. SETTING: Nippon Medical School Hospital, Tokyo, Japan. METHODS: Phacoemulsification was performed in 28 cases. The corneal volume within 3.0 mm and 10.0 mm circles of the cornea was measured using Scheimpflug imaging (Pentacam, Oculus, Inc.) and the cell density, using specular microscopy (Noncon Robo, Konan Medical). The volume stress index (VSI), a parameter for measuring functional evaluation, was calculated by dividing the volume increase within the 3.0 mm circle (preoperative corneal volume − corneal volume at time of measurement) by the central cell density value. The resulting value is indicative of the amount of postoperative increase in corneal volume with which each corneal endothelial cell should be able to cope. RESULTS: Three months after surgery, the 3.0 mm corneal volume returned to preoperative values, while the 10.0 mm corneal volume remained significantly higher than preoperatively. The cell density values did not significantly change throughout the study. The VSI showed a significant decrease by 7 days after surgery followed by a gradual decrease until the end of the study. At 3 months, the VSI value was significantly smaller than at 1 day. CONCLUSION: The corneal volume increase after surgery may be indicative of the degree of the endothelial damage in the area; thus, the VSI may be useful in the functional assessment of the corneal endothelium.

Arcuate keratotomy to treat corneal astigmatism after cataract surgery: A prospective evaluation of predictability and effectiveness

OBJECTIVE Although several nomograms are available for the incisional keratotomy to correct naturally occurring astigmatism, astigmatic keratotomy in eyes after cataract surgery has not been well analyzed. The predictability and effectiveness of arcuate keratotomy in pseudophakic eyes were studied. DESIGN A prospective, multicenter study. PARTICIPANTS One hundred four eyes of 86 patients with residual corneal astigmatism of 1.5 diopters (D) or more after cataract surgery were examined. INTERVENTION Arcuate keratotomy was performed in nine centers by nine surgeons. MAIN OUTCOME MEASURES The amount of astigmatic correction was calculated using the vector analysis of preoperative and 6-month postoperative refractive cylinder results. RESULTS Multiple regression analysis showed that optical zone size, number of incisions, and incision length had significant correlations with the amount of astigmatic correction. The regression equation was expressed as effects = (-0.643 x optical zone size) + (0.998 x incision number) + (0.057 x incision length) + 2.356. The parameter of predictability (r2: 35%) was lower than that reported for congenital astigmatism (48 to approximately 56%). A new nomogram was derived based on the multiple regression equation. CONCLUSIONS Astigmatic keratotomy in pseudophakic eyes is less predictable than that in eyes with idiopathic astigmatism, but the procedure is sufficiently effective in reducing the residual astigmatism after cataract surgery. Individual nomograms are necessary for astigmatic keratotomy in eyes with naturally occurring and postsurgical astigmatism.

Alteration of free radical development by ophthalmic viscosurgical devices in phacoemulsification

PURPOSE: To determine the effect of ophthalmic viscosurgical devices (OVDs) and irrigation/aspiration (I/A) settings on free radical development during phacoemulsification. SETTING: Department of Ophthalmology, Nippon Medical School, Tokyo, Japan. METHODS: Free radicals were detected by the electron spin resonance (ESR) spin‐trap method. After a spin‐trapping agent, 5,5‐dimethyl‐1‐pyrroline N‐oxide 1%, was mixed with the irrigating solution, phacoemulsification simulation was performed in an eye model at 100% ultrasound power levels for 10, 20, and 30 seconds. A high I/A setting (35 mL/min with 250 mm Hg vacuum) and a low I/A setting (15 mL/min with 60 mm Hg vacuum) were used in combination with no OVD, sodium hyaluronate 1% (Healon), sodium hyaluronate 2.3% (Healon5), sodium hyaluronate 3%–chondroitin sulfate 4% (Viscoat), or sodium hyaluronate 1% (Opegan). Immediately after phacoemulsification, the solution in the anterior chamber was collected and signals from the spin adduct were measured using an ESR spectrometer. RESULTS: With the low setting, all OVDs significantly suppressed the signals for up to 20 seconds. At 30 seconds, the signals were still significantly smaller in all OVD groups, except Healon, than those in the no‐OVD. With the high setting, the effect was not significant in the Healon and Opegan groups at 10 seconds; by 20 seconds and after, only Viscoat showed significant suppression. CONCLUSIONS: Free radical development in phacoemulsification can be altered by OVD properties and I/A settings. To reduce oxidative stress to the corneal endothelium, attention should be paid to the retention of OVDs in the anterior chamber during phacoemulsification.

Effect of bottle height on the corneal endothelium during phacoemulsification.

PURPOSE: To directly measure intraocular pressure (IOP) in simulated phacoemulsification and to assess the usefulness of lowering the bottle height in protecting the corneal endothelium in clinical phacoemulsification. SETTING: Nippon Medical School Hospital, Tokyo, Japan. METHODS: Simulated phacoemulsification was performed in porcine eyes with 2 bottle heights, 65.0 cm (BH 65 group) and 19.0 cm (BH 19 group). The IOP was continuously measured with a microprobe. In a clinical study, phacoemulsification was performed with a bottle height of 60.0 cm (BH 60 group) and of 30.0 cm (BH 30 group). One day, 1 week, and 1 and 3 months after surgery, cell density and corneal volumes were measured using specular microscopy and rotating Scheimpflug photography, respectively. RESULTS: In the simulation study, IOP fluctuated between 50 mm Hg and 60 mm Hg in the BH 65 group and between 20 mm Hg and 30 mm Hg in the BH 19 group. In the clinical study of 31 eyes, the rate of cell density decrease was significantly lower in the BH 30 group than in the BH 60 group at all time points. The rate of increase in corneal volume was significantly lower in the BH 30 group than in the BH 60 group at 1 month. CONCLUSIONS: Intraoperative IOP in phacoemulsification with a usual bottle height appeared to exceed the normal range. Phacoemulsification with a low bottle height was less harmful to the corneal endothelium.

Radial keratotomy to treat myopicrefractive error after cataract surgery

PURPOSE To assess the predictability and effectiveness of radial keratotomy in patients with myopic refractive error and unacceptable anisometropia after cataract surgery. SETTING A prospective multicenter study. METHODS This study comprised 40 eyes of 40 Japanese patients who had had cataract surgery. Radial keratotomy was performed, and the 6 month postoperative data were analyzed. RESULTS Mean patient age was 71.0 years +/- 7.4 (SD) (range 51 to 84 years) and mean preoperative anisometropia -3.41 +/- 1.69 D (range -1.25 to -7.75 D). The surgery decreased mean anisometropia to -1.01 +/- 0.94 D (P < .000001, Wilcoxon signed-rank test), a mean reduction of 2.22 +/- 1.23 D (range 0.75 to 5.88 D). Postoperative anisometropia ranged from 0.81 to -3.13 D. The surgical effects were overestimated by the nomograms developed for the correction of naturally occurring myopia in the eyes of white patients. Multiple regression analysis revealed that optical zone size and number of incisions were significantly correlated with the amount of myopic correction, and the regression equation (R2 = 0.77) was expressed as follows: Effects = (-1.45 x optical zone size) + (0.24 x incision number) + 7.60. A new nomogram was derived based on this equation. CONCLUSIONS Radial keratotomy was a safe and efficient procedure to treat myopic refractive error in pseudophakic eyes. Separate nomograms are necessary for white and Asian populations.

Temperature in the anterior chamber during phacoemulsification

Purpose To evaluate changes in the aqueous humor temperature using 2 phacoemulsification units (Stellaris 28.5 kHz device and Whitestar Signature 40 kHz device). Setting Nippon Medical School, Musashikosugi Hospital, Kawasaki City, Kanagawa, Japan. Design Experimental study. Methods Aqueous humor temperatures were measured with a temperature probe set in the anterior chamber during ultrasound (US) oscillation in porcine eyes under 5 conditions. Results Continuous longitudinal oscillation caused a rapid rise in aqueous humor temperature, while the pulse and elliptical modes suppressed temperature elevation. Reducing the number of US tip vibrations did not reduce the temperature in the anterior chamber. However, raising the vacuum setting allowed the aspirations to rise to the set value, thereby lowering the temperature in the anterior chamber. Conclusion Because differences in the phacoemulsification settings can lead to temperature elevations in the anterior chamber, surgeons must carefully monitor these settings to prevent corneal tissue damage. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Anterior chamber irrigation with an ozonated solution as prophylaxis against infectious endophthalmitis

Purpose: To assess the validity of anterior chamber irrigation with an ozonated solution as prophylaxis against endophthalmitis. Setting: Department of Ophthalmology, Nippon Medical School, Tokyo, Japan. Methods: Viability of human corneal endothelium in culture was assessed by the WST‐8 assay, lactate dehydrogenase (LDH) release assay, and trypan blue exclusion assay after exposure to a 4 to 40 parts per million (ppm) solution for 10 to 60 seconds. The in vivo effect was observed 1 week after irrigation of a 4 ppm solution in the rabbit anterior chamber by trypan blue exclusion assay. Bactericidal efficacy of the anterior chamber irrigation with the 4 ppm solution was examined by bacterial colony count of the aqueous humor following methicillin‐resistant Staphylococcus aureus (MRSA) contaminated intraocular lens implantation in the porcine eye. Results: The WST‐8 assay revealed no significant reduction of viability with 10‐second exposure to a 4 ppm solution. Lactate dehydrogenase release and trypan blue exclusion assays similarly demonstrated little damage after 60‐second exposure to a 4 ppm solution. In the rabbit cornea 1 week after treatment, damage caused by 30‐second exposure to a 4 ppm solution was not significant. The MRSA colony count documented almost complete bactericidal action with 5‐second exposure to the 4 ppm solution when no ophthalmic viscosurgical device existed in the anterior chamber. Conclusion: Limited damage to the corneal endothelium after 10‐second exposure and potent bactericidal action with 5‐second exposure suggests the validity of anterior chamber irrigation with a 4 ppm ozonated solution as prophylaxis against endophthalmitis.

Efficacy of Ophthalmic Viscosurgical Devices in Preventing Temperature Rise at the Corneal Endothelium during Phacoemulsification

ABSTRACT Purpose: To investigate temperature alterations in the aqueous humor and the corneal endothelium during phacoemulsification, and to evaluate the effect of ophthalmic viscosurgical devices in preventing a temperature rise at the corneal endothelium during phacoemulsification. Methods: Temperatures of the aqueous humor and corneal endothelium were measured using two temperature probes set in the anterior chamber during ultrasound oscillation in porcine eyes, with or without ophthalmic viscosurgical devices. Results: Without an ophthalmic viscosurgical device, temperatures in both the aqueous humor and the corneal endothelium rapidly rose during the ultrasound oscillation, while with an ophthalmic viscosurgical device, the temperature elevation of the corneal endothelium site was suppressed compared with the aqueous humor. Conclusion: Surgeons need to be especially aware of ophthalmic viscosurgical device retention during phacoemulsification, because it can protect the corneal endothelium from heat generated during this procedure.

A Novel “Slit Side View” Method to Evaluate Fluid Dynamics during Phacoemulsification

Due to recent technical advances in cataract surgeries, there has been a significant improvement in the safety and surgical outcomes of phacoemulsification. However, the corneal endothelium can be damaged during phacoemulsification by multiple factors. Therefore, we used a slit lamp to analyze the fluid dynamics of ophthalmic viscosurgical devices (OVDs) in the anterior chamber during phacoemulsification. In this experimental study, extracted porcine eyes were injected with OVDs stained with fluorescein through a side port of the eye and then fixed on a slit lamp microscope. After inserting a phaco tip, phacoemulsification simulation was then performed on the iris plane. Subsequent movements of OVDs in the anterior chamber were observed during the procedure by using a slit lamp microscope. Aspiration and removal of cohesive OVDs from the inside of the anterior chamber occurred within a few seconds after the ultrasonic vibration. Aspiration of dispersive OVDs occurred gradually, with some of the OVDs remaining on the side of the anterior chamber side in an irregular shape. This shape enabled the OVD to trap the air, thereby preventing the air from directly touching the corneal endothelium. Viscoadaptive OVDs remained inside the anterior chamber as a lump, with the infusion solution flowing between the corneal endothelium and the OVD, thus leading to the eventual aspiration of the OVD. Viscous dispersive OVDs remained as a lump between the corneal endothelium and the phaco tip. However, once the infusion solution flowed between the cornea and the OVD, the OVD detached from the corneal endothelium, indicating that this type would likely be aspirated and removed. This method, termed the “slit side view,” enables viewing of the movement of OVDs during surgery, as well as observation of the fluid dynamics in the anterior chamber.