Accuracy assessment of artificial intelligence IOL calculation formulae: utilizing the heteroscedastic statistics and the Eyetemis Analysis Tool.

OBJECTIVES: To analyse the accuracy of artificial intelligence (AI)-driven intraocular (IOL) calculation formulae, together with established formulae using the heteroscedastic methodology and the Eyetemis Analysis Tool. METHODS: Data from 404 eyes who underwent uneventful phacoemulsification with implantation of the SN60WF IOL were retrospectively reviewed. IOL power calculations were performed using the Barrett Universal II (BUII), EVO 2.0, Hoffer QST, K6, Ladas Super Formula (LSF), Nallasamy, PEARL-DGS and RBF 3.0 formulae. The SD of the prediction error (PE), served as the primary metric for accuracy. The mean absolute deviation (MAD) and the predictability rates within intervals from ±0.25 D to ±1.50 D were also evaluated. The Eyetemis Analysis Tool was used for further validation. RESULTS: The SD ranged from 0.468 (Nallasamy) to 0.510 (LSF). The Nallasamy formula had a significantly lower SD than the BUII (0.505, p = 0.025) and K6 (0.489, p = 0.022) formulae. The Nallasamy formula also exhibited the lowest MAD (0.358) with a significant difference compared with the Hoffer QST formula (0.384, p < 0.001). Finally, a significantly higher percentage of eyes achieving ± 0.50 D of the target refraction was seen using the Nallasamy formula (77.19%) compared with the Hoffer QST (71.04%, p = 0.019) and Ladas Super Formula (70.79%, p = 0.030) formulae. CONCLUSIONS: The Nallasamy formula, incorporating AI technology, demonstrated superior accuracy according to the analysis guidelines for PE statistics for non-gaussian datasets recommended by Holladay et al. and the online Eyetemis Analysis Tool.

Post-Penetrating Keratoplasty Assessment of Endothelial Function With a Scleral Lens Challenge.

ABSTRACT: Patients who have undergone penetrating keratoplasty may have corneal edema because of endothelial cell dysfunction. Scleral lens wear may exacerbate edema, particularly if lens fit is suboptimal. Distinguishing between edema because of inherent endothelial cell dysfunction and swelling because of scleral lens-related hypoxia can be challenging. It is necessary, however, to identify the most likely cause of increased corneal thickness to determine whether the patient simply needs refitting for a different lens design or needs additional surgical intervention. This case report describes the utility of corneal tomographic imaging before and after scleral lens wear both to estimate endothelial cell function and to direct decisions when designing a scleral lens for a post-transplant eye.

Appropriateness of Ophthalmology Recommendations From an Online Chat-Based Artificial Intelligence Model.

Objective: To determine the appropriateness of ophthalmology recommendations from an online chat-based artificial intelligence model to ophthalmology questions. Patients and Methods: Cross-sectional qualitative study from April 1, 2023, to April 30, 2023. A total of 192 questions were generated spanning all ophthalmic subspecialties. Each question was posed to a large language model (LLM) 3 times. The responses were graded by appropriate subspecialists as appropriate, inappropriate, or unreliable in 2 grading contexts. The first grading context was if the information was presented on a patient information site. The second was an LLM-generated draft response to patient queries sent by the electronic medical record (EMR). Appropriate was defined as accurate and specific enough to serve as a surrogate for physician-approved information. Main outcome measure was percentage of appropriate responses per subspecialty. Results: For patient information site-related questions, the LLM provided an overall average of 79% appropriate responses. Variable rates of average appropriateness were observed across ophthalmic subspecialties for patient information site information ranging from 56% to 100%: cataract or refractive (92%), cornea (56%), glaucoma (72%), neuro-ophthalmology (67%), oculoplastic or orbital surgery (80%), ocular oncology (100%), pediatrics (89%), vitreoretinal diseases (86%), and uveitis (65%). For draft responses to patient questions via EMR, the LLM provided an overall average of 74% appropriate responses and varied by subspecialty: cataract or refractive (85%), cornea (54%), glaucoma (77%), neuro-ophthalmology (63%), oculoplastic or orbital surgery (62%), ocular oncology (90%), pediatrics (94%), vitreoretinal diseases (88%), and uveitis (55%). Stratifying grades across health information categories (disease and condition, risk and prevention, surgery-related, and treatment and management) showed notable but insignificant variations, with disease and condition often rated highest (72% and 69%) for appropriateness and surgery-related (55% and 51%) lowest, in both contexts. Conclusion: This LLM reported mostly appropriate responses across multiple ophthalmology subspecialties in the context of both patient information sites and EMR-related responses to patient questions. Current LLM offerings require optimization and improvement before widespread clinical use.

Suture Fixation to Reduce Graft Detachment in Descemet Stripping Endothelial Keratoplasty.

PURPOSE: The aim of this study was to report the outcomes of graft fixation using interrupted, full-thickness sutures on graft detachment after Descemet stripping endothelial keratoplasty (DSEK). METHODS: All DSEK procedures performed at Mayo Clinic, Rochester, MN, from 2015 through 2022 were retrospectively reviewed. Risk factors for graft detachment were defined as previous incisional glaucoma surgery, previous penetrating keratoplasty, or absence of the normal lens-capsule barrier. Cases were categorized into sutured, high-risk grafts; unsutured, high-risk grafts; and unsutured, low-risk grafts. The primary outcome was graft detachment, and secondary outcomes were early graft failure and graft clarity at 12 months after surgery. RESULTS: Demographics between the high-risk groups were similar for sex and age at the time of surgery. Graft detachment occurred in 4 of 97 sutured, high-risk eyes (4.1%) and 24 of 119 unsutured high-risk eyes (20.2%) ( P = 0.002). In comparison, graft detachment occurred in 18 of 181 unsutured low-risk eyes (9.9%). The incidence of early graft failure was 2.1%, 5.0%, and 3.3% and late graft failure by 12 months was 9.8%, 12.8%, and 4.2%, respectively. CONCLUSIONS: In eyes with high-risk factors for graft detachment, suture fixation of the graft in DSEK decreased graft detachment to a rate at least as low as that in low-risk eyes.

The effect of patient age on some new and older IOL power calculation formulas.

PURPOSE: To assess the accuracy of intraocular lens (IOL) power calculation in different age groups using various IOL calculation formulas. METHODS: Data from 421 eyes of 421 patients ≥60 years old (ages: 60-69, n = 131; 70-74, n = 105; 75-84, n = 158 and ≥85, n = 27), who underwent uneventful cataract surgery with SN60WF IOL implantation at John A. Moran Eye Center, Salt Lake City, USA, were retrospectively obtained. The SD of the prediction error (PE), median and mean absolute PEs and the percentage of eyes within ±0.25, ±0.50, ±0.75 and ±1.00 D were calculated after constant optimizations for the following formulas: Barrett Universal II (BUII), Emmetropia Verifying Optical (EVO) 2.0, Haigis, Hoffer Q, Hoffer QST, Holladay 1, Kane, Radial Basis Function (RBF) 3.0 and SRK/T. Results were compared between the different age groups. RESULTS: Predictability rates within 0.25D were lower for the eldest age group compared with the other groups using the EVO 2.0 (33% vs. 37%-53%, p = 0.045), Kane (26% vs. 35%-50%, p = 0.034) and SRK/T (22% vs. 31%-49%, p = 0.002). Higher median absolute refractive errors for all formulas were observed in the oldest group [range: 0.39 D (Haigis, Hoffer QSR)-0.48 D (Kane)], followed by the youngest group [range: 0.30 D (RBF 3.0)-0.39 D (Holladay 1, SRK/T)] but did not reach statistical significance. No significant differences between the groups in the distribution parameter were seen. CONCLUSION: Current IOL power calculation formulas may have variable accuracy for different age groups. This should be taken into account when planning cataract surgery to improve refractive outcomes.

Measurement of Phacoemulsification Vacuum Pressure in the Oertli CataRhex3.

Purpose: To determine the actual vacuum pressure generated by the Oertli CataRhex 3® (Oertli), using an external measuring system. Methods: The effective vacuum pressure created by the Oertli was measured with a pressure device that was continuous with the vacuum tubing system while closed to the external environment. Measurements were taken with the machine set to 300 and 500 mmHg at flow rates of 20, 35, and 50 mL/min and at bottle heights of 60, 80, and 100 cm. Pressures were recorded after the foot pedal was depressed to vacuum setting (second position), and the pressure was allowed to stabilize. Subsequently, it was compared to the pressure value displayed by the machine. Results: Externally measured vacuum pressure was on average 13.02% greater (39.05 mmHg) than displayed vacuum pressure at 300 mmHg (P < 0.005) and 8.60% greater (42.98 mmHg) than displayed vacuum at 500 mmHg (P < 0.005). The average difference between displayed and measured pressure increased with increasing bottle heights. Conclusion: On average, the vacuum pressure generated in the Oertli was found to be significantly higher than the machine's reading when the machine was set at 300 mmHg and 500 mmHg. Adjusting vacuum had variable effects on the measured versus displayed pressure readings.

Optimization of Phacoemulsification Tip Gauge on the Oertli CataRhex3 in an in vitro Setting.

Purpose: To evaluate the effect of each of the tip sizes available for the Oertli CataRhex3® phacoemulsification machine on efficiency. Methods: Porcine lenses were fixed in formalin for 2 hours, then cut into 3.0 mm cubes. We studied three Oertli tips, all of which had a 30-degree bevel: easyTip 2.2 mm (20G), easyTip 2.8 mm (19G), and CO-MICS (21G). For the 19G and 20G tips, vacuum was set at 600 mmHg, irrigation rate at 50 mL/min, continuous power 70%, and bottle height 85 cm. For the 21G tip, vacuum was set at 450 mmHg; irrigation and power settings were identical to those used for the easyTip tips. We measured time to removal and chatter events to determine efficiency. Results: Results from 20 trials for each tip showed that the larger the gauge size, the more quickly lens fragments were removed. Chatter events demonstrated an increasing trend with smaller tip gauge. The 19G tip used an average time to fragment removal of 2.8 seconds; the 20G, 3.2 seconds; and the 21G, 4.6 seconds. Increasing tip diameter from 21G to 20G decreased emulsification time by 33% (P = 0.02). Increasing the diameter from 21G to 19G further decreased time to emulsification by 42% (P = 0.003). The 21G tip had a mean 1.4 events/cube; 20G, 0.35 events; and 19G, 0.1 events. Differences in mean chatter events for each tip were each statistically significant. Conclusion: These data suggest that when evaluated by chatter events and emulsification time, the 2.8 mm (19G) easyTip proves to have greatest efficiency.

Optimum on-time and off-time combinations for micropulse phacoemulsification in venturi vacuum mode.

PURPOSE: To measure the time to fragment removal and number of chatter events using various combinations of micropulse on times and off times (measured in milliseconds) of longitudinal ultrasound (US) using a venturi-based phacoemulsification system. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, USA. DESIGN: Experimental study. METHODS: Pig lenses were hardened with formalin and cut into 2.0 mm cubes. The time to fragment removal (efficiency) and frequency of fragments bouncing off the tip (chatter) were measured with the venturi-based system. Micropulse longitudinal US was tested. Parameters were combinations of 5, 6, and 7 milliseconds on, with 5, 6, and 7 milliseconds off. Twenty runs each of 9 combinations were completed. RESULTS: There was a statistically significant difference between on/off duty cycle combinations. The 6 on/7 off group had higher efficiency than the 5 on/6 off and 7 on/7 off groups. Six on/5 off was more efficient than 5 on/6 off. When data were pooled and on times alone were used, 6 milliseconds on time was more efficient than 5 or 7 milliseconds. No efficiency differences in off times were found. No significant chatter differences were observed. CONCLUSIONS: Using micropulse longitudinal US in venturi vacuum mode, 6 milliseconds on was the most efficient on time. Five, 6, and 7 milliseconds off times had similar efficiency. These data suggest that the most efficient setting with lowest US energy use is 6 milliseconds on and 7 milliseconds off.

Optimization of the Oertli CataRhex 3® phacoemulsification machine.

PURPOSE: The aim of this study was to determine optimal bottle height, vacuum, aspiration rate, and power settings of the Oertli CataRhex 3® phacoemulsification machine. METHODS: Porcine lens nuclei were hardened with formalin and cut into 2.0 mm cubes. Lens cubes were emulsified using the easyTip® 2.2 mm at 30°. Fragment removal time (efficiency) and fragment bounces off the tip (chatter) were measured. Settings tested included bottle height of 60, 80, 100 and 120 cm; aspiration rate of 40, 45, and 50 mL/min; vacuum of 400, 500, and 600 mmHg; and power of 50, 60, 70, 80, 90, and 100%. RESULTS: Efficiency and chatter increased in a linear fashion with increasing vacuum to 600 mmHg (P=0.017, P=0.046, respectively). The most efficient aspiration rate was 50 mL/min, although this finding lacked statistical significance (P=0.66). Increasing power increased efficiency up to 80% without increasing chatter (P=0.042, P=0.71, respectively). Compared to all other power settings, chatter was increased at 100% (P=0.014). CONCLUSION: The most efficient machine settings were vacuum at 600 mmHg, aspiration rate at 50 mL/min, and power at 80%.

The effect of increasing power when grooving using phacoemulsification.

PURPOSE: To determine optimal power settings on the Centurion Vision System during the grooving step in cataract surgery. METHODS: Intact porcine lenses hardened by formalin and placed in a chamber designed to simulate the anterior chamber of the eye were used to test longitudinal power at 40%, 70%, and 100% and torsional power at 0%. Flow rate was set at 40 mL/min. Vacuum was set at 400 mmHg, intraocular pressure was set at 50 mmHg, and a balanced phacoemulsification tip with a 20 degree tip and a 30 degree bevel was used. Efficiency (time to groove the lens in half) was determined. RESULTS: Increasing longitudinal power from 40% to 70% increased efficiency by 28% (P<0.05), and by 32% (P<0.05) when increasing longitudinal power from 40% to 100%. There was no statistically significant increase in efficiency from 70% to 100%. CONCLUSION: For the tested variables, a longitudinal power of 70% was determined to be most efficient during the grooving step of cataract surgery for equivalent 3-4+ nuclei. Further increases in power demonstrated no statistically significant improvement in efficiency.

An unusual case of idiopathic calcinosis of the eyelid.

Idiopathic subepidermal calcinosis, also known as idiopathic calcinosis cutis, is a rare condition, which typically presents as a small, hard, subepithelial mass in the absence of systemic disease and trauma. We report on an atypical case of idiopathic calcinosis, which appeared in an otherwise healthy 61-year-old female along the tarsus of her right upper eyelid. The purpose of this case report is to demonstrate idiopathic calcinosis in an unusual location that is deep to the dermis and to discuss the vast differential diagnosis of this entity.

Association between Chronic Obstructive Pulmonary Disease and Exfoliation Syndrome: The Utah Project on Exfoliation Syndrome.

PURPOSE: Exfoliation syndrome (XFS) is associated with genetic variants of lysyl oxidase-like 1 (LOXL1), a key enzyme in the stabilization of extracellular matrix (ECM) and elastin, and in connective tissue repair. Because patients with chronic obstructive pulmonary disease (COPD) have increased and altered elastin degradation, an association between XFS and COPD was hypothesized and analyzed. Impact of XFS on survival in patients with COPD was evaluated. DESIGN: Case-case and case-control comparison with 5:1 age- and sex-matched controls. SUBJECTS: Total of 2943 patients with XFS, 20 589 patients with COPD, and 162 patients with both disorders seen between 1996 and 2015 were identified from Utah Population Database-linked medical records. Controls were selected and matched by sex and birth year to patients in a 5:1 ratio. METHODS: Unconditional logistic regression, using International Classification of Diseases, Ninth Revision codes (365.52 and 366.11) to define XFS and an outcome of COPD (496.0), was used to calculate the odds ratio (OR) to estimate risk of COPD in patients with XFS, adjusting for age and sex. Model covariates included race, obesity, and tobacco use. MAIN OUTCOME MEASURES: Whether XFS patients have an increased risk of developing COPD; whether COPD patients have an increased risk of XFS; and, in COPD patients, whether survival differs between those with XFS and those without. RESULTS: In XFS patients, risk of a COPD diagnosis was increased compared with that of non-XFS controls (OR = 1.41; 95% confidence interval [CI], 1.17-1.70; P < 0.0004), particularly in a tobacco users subset (OR = 2.17; 95% CI, 1.15-4.09; P = 0.02). COPD patients and controls with no COPD did not differ in their risk of an XFS diagnosis. COPD patients with XFS had significantly better survival than patients with COPD and no XFS history. CONCLUSIONS: XFS patients may have an increased risk of a COPD diagnosis compared with non-XFS individuals. In COPD patients, risk of XFS was not increased compared with those with no COPD history. In COPD patients with XFS, survival is significantly improved compared with COPD patients with no XFS history.

Effect of high vacuum and aspiration on phacoemulsification efficiency and chatter using a transversal ultrasound machine.

PURPOSE: To examine the role of high vacuum and aspiration settings on efficiency using a transversal ultrasound (US) machine. SETTING: John A. Moran Eye Center Laboratory, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine lens nuclei were incubated in formalin for 2 hours and then cut into 2.0 mm cubes. Phacoemulsification was performed using the Whitestar Signature machine. Settings were bottle height 50 cm, on-time 6 milliseconds, and off-time 6 milliseconds. One hundred percent power was used for all 240 runs. Tested parameters were aspiration of 50 mL/min and 60 mL/min and vacuum of 500, mm Hg, 600 mm Hg, and 650 mm Hg. RESULTS: With continuous US, increasing aspiration from 50 mL/min to 60 mL/min significantly increased efficiency (23%). Increasing vacuum from 500 mm Hg to 650 mm Hg and from 600 mm Hg to 650 mm Hg significantly increased efficiency (20.2% and 13.6%, respectively). Higher vacuum and aspiration parameters did not influence the incidence of chatter events. In the micropulse US group, there was no significant efficiency increase with increasing vacuum or aspiration levels. There was a significant efficiency increase of continuous over micropulse US at an aspiration setting of 60 mL/min and vacuum settings of 600 mm Hg and 650 mm Hg. CONCLUSIONS: As aspiration and vacuum increased, efficiency increased under continuous transverse US. No significant efficiency improvement occurred at high aspiration and vacuum settings under micropulse US. At 60 mL/min aspiration and more than 600 mm Hg vacuum, continuous power was significantly more efficient than micropulse transverse US.

Optimum on-time duty cycle for a transversal ultrasound machine.

PURPOSE: To evaluate the optimum on-time setting for the most efficient removal of lens fragments using micropulse ultrasound (US) and Ellips FX transversal US in the Whitestar Signature Pro phacoemulsification machine. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine lens nuclei were soaked in formalin for 2 hours and cut into 2.0 mm cubes. The US machine was used with a bent 0.9 mm phaco tip and a 30-degree bevel. The off time was set to 6 milliseconds (ms) and the on time varied from 4 to 10 ms in 1 ms increments. Efficiency (time for fragment removal) and chatter (number of times the fragment bounced from the tip) were measured. RESULTS: A linear incremental increase in efficiency was observed between 4 ms and 6 ms. The most statistically significant efficiency was achieved with an on time of 6 ms. On times shorter than 6 ms were significantly less efficient (P = .05). Greater on times (7 to 10 ms) did not result in a significant difference in efficiency (P = .72), but did appear to have more chatter events when comparing on-time settings of 7 to 10 ms with 4 to 6 ms (P = .02). CONCLUSIONS: With micropulse transversal US, 6 ms of on time was as efficient as longer on times. To maximize phacoemulsification efficiency and minimize chatter events, an on time of 6 ms is recommended.

Effect of increasing flow when grooving during phacoemulsification.

PURPOSE: To determine optimum flow settings on the Centurion Vision System during the grooving step in cataract surgery. SETTING: John A. Moran Eye Center Laboratory, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Intact porcine lenses hardened by formalin and placed in a chamber designed to simulate the anterior chamber of the eye were used to test flow rate settings at 20 mL/min, 40 mL/min, and 60 mL/min. Vacuum was set at 400 mm Hg, longitudinal power at 80%, torsional power at 80%, and intraocular pressure at 50 mm Hg. A balanced phaco tip with a 20-degree tip and a 30-degree bevel was used. Efficiency (time to groove the lens in half) was determined. RESULTS: Increasing flow from 20 to 40 mL/min during grooving increased efficiency by 17% (P = .05), with no significant improvement shown at 60 mL/min. CONCLUSIONS: A flow rate of 40 mL/min was determined to be most efficient during the grooving step of cataract surgery. Further increases in flow rate showed no statistically significant improvement in efficiency, and with only 17% improvement flow rates less than 40 mL/min might be almost as efficient and might be safer.

Effect of chamber stabilization software on efficiency and chatter in a porcine lens model.

PURPOSE: To evaluate the effects of the use of programmable chamber stabilization software (Chamber Stabilization Environment) settings on efficiency and chatter in a porcine lens model. SETTING: John A. Moran Eye Center Laboratory, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine eyes were dissected and the lenses extracted. The lenses were then hardened and processed for the experiment. Phacoemulsification of the lens fragments was performed with the Whitestar Signature Pro with the Whitestar handpiece and a 0.9 mm straight Dewey tip with a 30-degree bevel. All arms of the study were run in peristaltic mode with 50 mL/minute aspiration, 100 cm bottle height, and on 100% power. The chamber stabilization software setting was used for each of the 4 study arms with a maximum vacuum of 500 mm Hg. Arm 1 included 20 runs with the up time set to 2000 milliseconds. Arm 2 was performed with similar settings but with an up time of 0 millisecond. Arms 3 and 4 were run with up times of 1000 milliseconds and 500 milliseconds, respectively. RESULTS: The mean efficiency time of each run was as follows: 0 millisecond = 1.4 seconds, 500 milliseconds = 0.95 seconds, 1000 milliseconds = 0.88 seconds, 2000 milliseconds = 0.93 seconds. When compared with 0 millisecond, each of the other arms were significantly faster. Chatter events were comparable between the study arms. CONCLUSION: The chamber stabilization software does not decrease efficiency when compared with full vacuum on if at least 500 milliseconds of up time is maintained.

Optimization of transversal phacoemulsification settings in peristaltic mode using a new transversal ultrasound machine.

PURPOSE: To determine the optimum bottle height, vacuum, aspiration rate, and power settings in the peristaltic mode of the Whitestar Signature Pro machine with Ellips FX tip action (transversal). SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine lens nuclei were hardened with formalin and cut into 2.0 mm cubes. Lens cubes were emulsified using transversal and fragment removal time (efficiency), and fragment bounces off the tip (chatter) were measured to determine optimum aspiration rate, bottle height, vacuum, and power settings in the peristaltic mode. RESULTS: Efficiency increased in a linear fashion with increasing bottle height and vacuum. The most efficient aspiration rate was 50 mL/min, with 60 mL/min statistically similar. Increasing power increased efficiency up to 90% with increased chatter at 100%. CONCLUSION: The most efficient values for the settings tested were bottle height at 100 cm, vacuum at 600 mm Hg, aspiration rate of 50 or 60 mL/min, and power at 90%.

The Effect of Pulsing on Transverse Ultrasound Efficiency and Chatter.

PURPOSE: To evaluate the effects of micropulse, long pulse, and continuous ultrasound on transverse ultrasound using Abbott Medical Optics' (AMO) WhiteStar Signature Pro with the Ellips FX handpiece. DESIGN: In vitro laboratory study. METHODS: This study was conducted at the John A. Moran Eye Center Laboratory, University of Utah, Salt Lake City, Utah, USA. Porcine lenses were hardened in formalin for 2 hours and equilibrated in basic salt solution (BSS) over a 24-hour period. The lenses were then cubed in 2.0 × 2.0-mm pieces. These pieces were stored in BSS until the time of experimentation. The AMO WhiteStar Signature Pro machine (Abbott Medical Optics) with the Ellips FX handpiece and a 0.9-mm bent Dewey tip with a 30-degree bevel (Microsurgical Technology Inc) were used for phacoemulsification. Three runs of 20 lenses each were performed, measuring efficiency and chatter. Transverse ultrasound varied in the 3 runs and included continuous, 6 ms on/off micropulse, and 50 ms on/off long pulse. RESULTS: Micropulse was more efficient than long pulse by 43% (P = .00003) and continuous by 42% (P = .000387). There were also less chatter events with micropulse than with long-pulse and continuous ultrasound. However, this difference did not reach significance. CONCLUSION: The 6 ms on and 6 ms off micropulse transverse 3-dimensional ultrasound is more efficient and produces fewer chatter events than both long-pulse and continuous ultrasound.

Vimentin knockdown decreases corneal opacity.

PURPOSE: Wound induced corneal fibrosis can lead to permanent visual impairment. Keratocyte activation and differentiation play a key role in fibrosis, and vimentin, a major structural type III intermediate filament, is a required component of this process. The purpose of our study was to develop a nonviral therapeutic strategy for treating corneal fibrosis in which we targeted the knockdown of vimentin. METHODS: To determine the duration of plasmid expression in corneal keratocytes, we injected a naked plasmid expressing green fluorescent protein (GFP; pCMV-GFP) into an unwounded mouse corneal stroma. We then injected pCMV-GFP or plasmids expressing small hairpin RNA in the corneal wound injury model (full-thickness corneal incision) to evaluate opacification. RESULTS: GFP expression peaked between days 1 and 3 and had prominent expression for 15 days. In the corneal wound injury model, we found that the GFP-positive cells demonstrated extensive dendritic-like processes that extended to adjacent cells, whereas the vimentin knockdown model showed significantly reduced corneal opacity. CONCLUSIONS: These findings suggest that a nonviral gene therapeutic approach has potential for treating corneal fibrosis and ultimately reducing scarring.