Lens thickness in atopic cataract: case-control study.

PURPOSE: To examine whether atopic cataracts are associated with thinner lenses. SETTING: Department of Ophthalmology, Jikei University Hospital, Tokyo, Japan. DESIGN: Retrospective matched case-control study. METHODS: 31 eyes with atopic cataracts, 62 with nonatopic cataracts, and 31 without cataracts were analyzed. Each group was matched for age (±4 years) and sex. RESULTS: The mean lens thickness (LT) was 3.76 ± 0.40 mm, 3.94 ± 0.49 mm, and 4.11 ± 0.40 mm in eyes with atopic cataracts, nonatopic cataracts, and normal lenses, respectively. Repeated-measures analysis of variance showed that the LT in the atopic cataract group was significantly thinner than that in the nonatopic cataract ( P = .036) and normal lens ( P < .001) groups. In multivariate logistic regression analysis, a thinner LT was negatively correlated with age (odds ratio [OR], 0.91; 95% CI, 0.86-0.96) and positively correlated with anterior subcapsular cataract (ASC) (OR, 5.61; 95% CI, 1.97-15.99). Atopy was not a significant factor. 24 (38.7%) of the 62 eyes with nonatopic cataracts and 24 (77.4%) of the 31 eyes with atopic cataracts had ASC. CONCLUSIONS: The lenses of eyes with atopic cataracts were thinner than those of controls. Atopic cataracts frequently present with anterior subcapsular opacity, which is associated with lens thinning.

Free radical production by femtosecond laser lens irradiation in porcine eyes.

PURPOSE: To investigate the relationship between the generation of free radicals and femtosecond laser lens irradiation. SETTING: AMO Laboratory, Tokyo, Japan. DESIGN: Ex vivo studies. METHODS: Hydroxyphenyl fluorescein (HPF) was injected into the anterior chamber of fresh 6-month-old porcine cadaver eyes (N = 31). After laser irradiation, a plate reader was used to measure the fluorescence of the aqueous humor samples. Relative fluorescence units (RFU) were calculated by subtracting the average control value from the measured values of all the samples. Experiment 1: After determining the RFU in the 7 laser-irradiated eyes, the relationship with the amount of laser energy was then assessed. Experiment 2: To clarify the issue regarding the degree of attenuation of the fluorescence intensity, HPF was simultaneously injected into 2 eyes, with 1 eye irradiated and the other eye used as a control. After dividing the RFU of the laser-irradiated eye by the control RFU, the laser irradiation-control RFU ratio was calculated, and the relationship with the laser irradiation energy amount then assessed. RESULTS: There was a significant correlation between the femtosecond laser lens irradiation energy and the RFU in the aqueous humor (P < .05, analysis of variance). CONCLUSIONS: Femtosecond laser lens irradiation increases the quantity of free radicals in the aqueous humor, with the extent of the increase dependent on the amount of laser energy. These results suggest that excessive laser irradiation during femtosecond laser-assisted cataract surgery might cause corneal endothelial damage because of the free radicals created during the procedure.

Influence of irrigation dynamic pressure-assisted hydrodissection on intraocular pressure and the posterior chamber-anterior hyaloid membrane barrier during cataract surgery.

PURPOSE: To evaluate the effects of irrigation dynamic pressure-assisted hydrodissection (irrigation-hydro: iH) on intraocular pressure (IOP) and the posterior chamber-anterior hyaloid membrane (PC-AHM) barrier in porcine eyes. STUDY DESIGN: Experimental. METHODS: In Experiment 1, IOP was recorded while irrigating the anterior chamber (AC), during iH, and during phacoemulsification and aspiration in 20 porcine eyes using bottle heights of 50, 70, and 90 cm. Under the same conditions, IOP was recorded during conventional manual cortical cleaving hydrodissection (manual hydro: mH) in 20 porcine eyes. In Experiment 2, after iH, ACs were perfused for 5 seconds with balanced salt solution containing 1.0-µm fluorescein beads in 20 porcine eyes using bottle heights of 70, 118, and 169 cm. PC-AHM barrier staining grade was evaluated by the Miyake-Apple view. RESULTS: iH proved successful in all cases. In Experiment 1, IOP during iH was relatively stable and peak IOP was below the baseline bottle height-dependent pressure. No eyes showed a peak IOP > 75 mmHg during iH, but 8 eyes showed a peak IOP > 75 mmHg during mH. In Experiment 2, neither AHT nor ruptured capsules were observed at any bottle height. CONCLUSION: Unlike mH, IOP during iH was relatively stable without any high peak IOP. Thus, iH offers a simple technique for reducing peak IOP and avoiding disturbance of the PC-AHM barrier.

The safety and efficacy of phaco-sleeve irrigation-assisted hydrodissection during femtosecond laser-assisted cataract surgery.

Femtosecond laser-assisted cataract surgery (FLACS) changes the intraoperative environment due to the generation of intracapsular gas that induces a high intracapsular volume. Manual hydrodissection (mH) may induce high intracapsular pressure (ICP) and additional intracapsular volume, thereby leading to capsular block syndrome (CBS). Since the phaco-sleeve irrigation-assisted hydrodissection (iH) technique is used to initially groove and split the lens and remove the intracapsular gas, this can reduce the intracapsular volume while bypassing the intracapsular lens prior to the hydrodissection. As iH uses the phaco tip to intentionally vacuum the intraocular fluid for use in inducing the irrigation jet from the sleeve side holes, the ICP cannot surpass the set irrigation pressure, thereby avoiding CBS. Using this technique, we performed FLACS without CBS in 310 cataract eyes. Our findings suggest that the iH technique may be beneficial for patients by preventing CBS during FLACS.

Irrigation dynamic pressure-assisted hydrodissection during cataract surgery.

The irrigation dynamic pressure-assisted hydrodissection technique (irrigation-hydro [iH]) does not require performing manual hydrodissection using a syringe and cannula to achieve cortical-capsular cleavage during cataract surgery. Since the iH technique uses the phaco tip to intentionally vacuum the intraocular fluid in order to induce the irrigation dynamic pressure for cortical-capsular cleavage, there is a reduction in the intraocular pressure (IOP) from the bottle-height-dependent hydrostatic pressure. Thus, since the peak irrigation pressure derived from the phaco tip sleeve will be limited by the height of the irrigation fluid bottle, this is advantageous in helping to avoid excessively high IOP during cortical-capsular hydrodissection. Using this technique, we were able to effectively perform phacoemulsification without complications in 607 of 609 cataract eyes. Our findings show that utilization of the iH technique would be of benefit to patients, as it prevents high-pressure hydrodissection-related complications, such as capsular block syndrome and tears in the anterior hyaloid membrane during cataract surgery.

Use of the phaco tip technique for lens cleavage and removal during cataract surgery.

Use of the phaco tip technique for lens cleavage and removal does not require manual hydrodissection using a syringe and cannula, or cortical removal using an irrigation/aspiration tip. The phaco tip is the only surgical instrument required for this technique. Its advantages include maintaining a stable intraocular pressure during cortical cleaving hydrodissection and lens removal, which includes the cortex.

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.

Development of a short version of the visual function questionnaire using item-response theory.

PURPOSE: In clinical ophthalmology as in other fields, measuring patient-reported outcomes imposes a burden on patients. To decrease that burden, we used item-response theory (IRT) to develop and test a short version of the National Eye Institute's Visual Function Questionnaire (VFQ). METHODS: We analyzed VFQ data from 276 adults in Japan. Most of them had glaucoma, cataract, or macular degeneration. Their visual acuity (Snellen fraction) averaged 20/120 (range: 20/13 to 20/2000) for the better eye, and 20/200 (range: 20/13 to 20/2000) for the worse eye. We used a polytomous IRT model, the Generalized Partial Credit Model as implemented in software for parameter scaling of rating data (PARSCALE). To select items for inclusion in the short version we examined each item's location on the latent-trait continuum, its slope, and its frequency of missing data. We also ensured representation of all 7 domains that are important in Japan. To examine the characteristics of the resulting scale, we computed its test information (an index of precision that can vary with the value of the latent trait), and carried out validation testing. RESULTS: From 32 of the original VFQ items, we selected 11. The scale comprising those 11 items (the VFQ-J11) had test information greater than 9 for values of the latent trait between -2.0 and +0.8. The item thresholds were well-targeted for patients with vision problems. Scores on the VFQ-J11 correlated strongly and in the expected direction with measures of visual field and corrected visual acuity. As expected for a valid measure, those scores also improved by a large amount (almost one standard deviation) after cataract surgery. CONCLUSION: This 11-item instrument can provide reliable and the valid data on visual functioning in patients with ophthalmic problems. It is expected to be less of a burden on respondents, while it maintains good psychometric properties.

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.

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.

Incidence of endophthalmitis after cataract surgery in Japan.

PURPOSE: To estimate the incidence rate of endophthalmitis after cataract surgery performed by Japanese surgeons. METHODS: A sample of 20% of members of the Japanese Society of Ophthalmic Surgeons was randomly selected. Each member was sent a postal survey asking for information on the number of cataract surgeries performed in 2003 and the number of postsurgery cases of endophthalmitis. RESULTS: Replies were received from 78.7% (513/652) of survey recipients. The total number of cataract surgeries was 100 539, among which 52 cases of endophthalmitis occurred, resulting in an overall incidence rate of 0.052%. Incidence rates were 0.049% (38/78 170) for scleral incision phacoemulsification and 0.043% (9/20 894) for clear corneal incision phacoemulsification, with no significant difference between groups. The average annual volumes of surgery were 210 and 280 cases for surgeons who preferred scleral incision and clear corneal incision, respectively. There was a significant difference between volumes (Student's t-test, p < 0.01). The incidence of endophthalmitis was significantly lower with high-volume (> 300 cases/year) surgeons than with low-volume (< or = 300 cases/year) surgeons (0.040% versus 0.066%, chi-square test, p < 0.05). CONCLUSIONS: The incidence of endophthalmitis after cataract surgery in Japan as estimated by a postal survey was low (0.052%) and consistent with rates reported previously. Surgeons who preferred clear corneal incision performed significantly more surgeries annually, but the incidence of endophthalmitis was similar between scleral and clear corneal incision phacoemulsification surgery.

Psychometric properties of the 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25), Japanese version.

BACKGROUND: The importance of evaluating the outcomes of health care from the standpoint of the patient is now widely recognized. The purpose of this study is to develop and test a Japanese version of the National Eye Institute Visual Function Questionnaire (NEI VFQ-25). METHODS: A Japanese version was developed with a previously standardized method. The questionnaire and optional items were completed by 245 patients with cataracts, glaucoma, or age-related macular degeneration, by 110 others before and after cataract surgery, and by a reference group (n = 31). We computed rates of missing data, measured reproducibility and internal consistency reliability, and tested for convergent and discriminant validity, concurrent validity, known-groups validity, factor structure, and responsiveness to change. RESULTS: Based on information from the participants, some items were changed to 2-step items (asking if an activity was done, and if it was done, then asking how difficult it was). The near-vision and distance-vision subscales each had 1 item that was endorsed by very few participants, so these items were replaced with items that were optional in the English version. For example, more than 60% of participants did not drive, so the driving question was excluded. Reliability and validity were adequate for all subscales except driving, ocular pain, color vision, and peripheral vision. With cataract surgery, most scores improved by at least 20 points. CONCLUSION: With minor modifications from the English version, the Japanese NEI VFQ-25 can give reliable, valid, responsive data on vision-related quality of life, for group-level comparisons or for tracking therapeutic outcomes.

Measuring rectilinear flow within the anterior chamber in phacoemulsification procedures.

PURPOSE: To measure and photograph rectilinear flow generated in an anterior chamber model during different power phases of phacoemulsification. SETTING: Oki Eye Surgery Center, Tokyo, Japan. METHODS: An ultrasound (US) needle was fitted to a Sovereign WhiteStar (AMO) phacoemulsification unit. The sleeved needle was inserted into a silicone test chamber filled with balanced salt solution with glutation (BSS Plus). An LV-1610 laser Doppler vibrometer (Ono-Sokki) captured and processed the velocity and displacement of vibrations on the surface of the test chamber. Measurements were processed in a CF-520 Fast Fourier Transform (FFT) analyzer with the results shown in real time on the FFT analyzer and displayed on a computer monitor using 3-dimensional software. Four US delivery modes were measured: WhiteStar DB, WhiteStar CF, continuous mode, and short-pulse mode at 6 pulses per second (pps). Flow and vacuum were set at 20 cc/min and 200 mm Hg, respectively, and US power was 20% and 50%. Schlieren photography of the fluid flow was performed with an ultra-high-speed Memrecam fx 6000 camera (NAC Image Technology). RESULTS: The peak vibration velocity (m/s) and displacement at the distal end of the test chamber were greatest for continuous mode, followed by short pulse (6 pps), WhiteStar DB, and WhiteStar CF, in descending order. At 20% power, the US needle generated a peak velocity of 8.64 x 10(-3) m/s in continuous mode, 7.30 x 10(-3) m/s in short-pulse mode, 5.03 x 10(-3) m/s in DB mode, and 3.74 x 10(-3) m/s in CF mode. At 50% power, the US needle generated a peak velocity of 12.8 x 10(-3) m/s in continuous mode, 10.9 x 10(-3) m/s in short-pulse mode, 8.52 x 10(-3) m/s in DB mode, and 6.37 x 10(-3) m/s in CF mode. Schlieren photography showed the greatest wave speed, intensity, and turbulence in continuous mode and the least with the WhiteStar modes. CONCLUSIONS: Peak vibration velocity and amplitude of displacement were less with the WhiteStar delivery modes than with continuous power or short-pulse modes. A similar reduction was seen in the rectilinear flow under Schlieren photography. Attenuation of rectilinear flow and turbulence patterns may have clinical implications for the corneal endothelium during phacoemulsification.

Corneal thickness measurements: scanning-slit corneal topography and noncontact specular microscopy versus ultrasonic pachymetry.

PURPOSE: To compare central corneal thickness measurements taken with 3 pachymetry systems: Orbscan scanning-slit corneal topography/pachymetry, Topcon SP2000P noncontact specular microscopy, and Tomey ultrasonic pachymetry. SETTING: Multicenter study, Tokyo, Japan. METHODS: In 216 healthy eyes of 114 subjects, scanning-slit topography, noncontact specular microscopy, and ultrasonic pachymetry were used in that sequence to record central corneal thickness. In another 20 healthy eyes of 13 subjects, 2 sets of measurements were repeated for each pachymetry to assess repeatability. RESULTS: The mean central corneal thickness was compatible between scanning-slit topography (546.9 micrometers +/- 35.4 [SD] ) and ultrasonic pachymetry (548.1 +/- 33.0 micrometers); however, noncontact specular microscopy gave a significantly smaller mean (525.3 +/- 31.4 micrometers) than the other 2 tests (P<.001, Tukey multiple comparison). There were significant linear correlations between scanning-slit topography and noncontact specular microscopy (r = 0.846, P<.001), noncontact specular microscopy and ultrasonic pachymetry (r = 0.897, P<.001), and ultrasonic pachymetry and scanning-slit topography (r = 0.852, P<.001). Noncontact specular microscopy tended to show the best repeatability; however, the difference was not statistically significant (P =.663, repeated-measure analysis of variance). CONCLUSIONS: Corneal thickness readings were comparable between scanning-slit topography and pachymetry; noncontact specular microscopy gave significantly smaller values. The measurements of the 3 methods showed significant linear correlations with one another. All methods provided acceptable repeatability of measurements.