The Burden of Caring for and Treating Glaucoma: The Patient Perspective.

PURPOSE: To understand the treatment burden experienced by patients receiving care for primary open-angle glaucoma. DESIGN: Semistructured, one-on-one, qualitative interviews. PARTICIPANTS: Patients with primary open-angle glaucoma and age ≥40 years who were scheduled for a follow-up glaucoma appointment at the Kellogg Eye Center. Researchers used purposeful sampling to ensure that there was representation of a range of ages, disease stages, total number of medical conditions, distance traveled to clinic, history of glaucoma surgery, employment, and education. Interviews were conducted until thematic saturation was obtained. METHODS: Participants were interviewed using a semi-structured interview guide that addressed aspects of glaucoma care that give them burden, how this burden impacts their lives, and factors that influence the burden and its impact. Researchers analyzed the transcripts using inductive thematic analysis and grounded theory to generate themes that emerged from the interviews and to map these themes into a conceptual model of glaucoma treatment burden. MAIN OUTCOME MEASURES: Themes related to glaucoma treatment burden generated by qualitative analysis. RESULTS: A total of 22 patients participated in the study. Study participants described 10 categories of glaucoma care activities that cause treatment burden, 8 themes for consequences of glaucoma treatment burden, and 25 themes of factors that influenced the workload created by the various glaucoma care activities and the consequences that they experienced because of these activities. CONCLUSIONS: Participants expressed that the treatment of glaucoma creates a burden for patients that is distinct from the burden of the disease process itself and that this burden negatively affects their quality of life and can potentially cause vision-threatening issues with medication and appointment adherence. We observed considerable variation in the extent to which participants experienced this burden and its consequences, much of which was explained by the influencing factors the participants described. Understanding glaucoma treatment burden and its influencing factors is important as we work to deliver patient-centered care and prevent vision loss.

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.

A Worldwide Price Comparison of Glaucoma Medications, Laser Trabeculoplasty, and Trabeculectomy Surgery.

Importance: Medical and surgical interventions for glaucoma are effective only if they are affordable to patients. Little is known about how affordable glaucoma interventions are in developing and developed countries. Objective: To compare the prices of topical glaucoma medications, laser trabeculoplasty, and trabeculectomy relative with median annual household income (MA-HHI) for countries worldwide. Design, Setting and Participants: Cross-sectional observational study. For each country, we obtained prices for glaucoma medications, laser trabeculoplasty, and trabeculectomy using government pricing data, drug databases, physician fee schedules, academic publications, and communications with local ophthalmologists. Prices were adjusted for purchasing power parity and inflation to 2016 US dollars, and annual therapy prices were examined relative to the MA-HHI. Interventions costing less than 2.5% of the MA-HHI were considered affordable. Main Outcomes and Measures: Daily cost for topical glaucoma medications, cost of annual therapy with glaucoma medications, laser trabeculoplasty, and trabeculectomy relative to MA-HHI in each country. Results: Data were obtained from 38 countries, including 17 developed countries and 21 developing countries, as classified by the World Economic Outlook. We observed considerable variability in intervention prices compared with MA-HHI across the countries and across interventions, ranging from 0.1% to 5% of MA-HHI for timolol, 0.1% to 27% for latanoprost, 0.2% to 17% for laser trabeculoplasty, and 0.3% to 42% for trabeculectomy. Timolol was the most affordable medication in all countries studied and was 2.5% or more of MA-HHI in only 2 countries (5%). The annual cost of latanoprost was 2.5% or more of MA-HHI in 15 countries (41%) (15 developing countries [75%] and no developed countries). The cost of laser trabeculoplasty was 2.5% or more of the MA-HHI in 15 countries (44%) (11 developing countries [65%] and 4 developed countries [24%]). The cost of trabeculectomy was 2.5% or more of the MA-HHI in 28 countries (78%) (18 developing countries [95%] and 10 developed countries [59%]). In 18 countries (53%), laser trabeculoplasty cost less than a 3-year latanoprost supply. Conclusions and Relevance: For many patients worldwide, the costs of medical, laser, and incisional surgical interventions were 2.5% or more of the MA-HHI. Successfully reducing global blindness from glaucoma requires addressing multiple contributing factors, including making glaucoma interventions more affordable.

Self-reported Eyeglass Use by US Medicare Beneficiaries Aged 65 Years or Older.

Importance: Medicare benefits do not include coverage for eyeglasses except after cataract surgery. Understanding the implications of a change to this policy would require knowing the number of Medicare beneficiaries who use eyeglasses, but no recent estimates are available. Objective: To estimate the number of older adults with Medicare who use eyeglasses. Design, Setting, Participants: This cross-sectional study used data from the 2015 US National Health and Aging Trends Study. Nationally representative data from 7497 respondents were reviewed and sample weights were applied so that the data represented 43.9 million Medicare beneficiaries aged 65 years or older. The estimates were based on the following 4 groupings of beneficiaries: (1) number who used eyeglasses for distance vision correction and had distance vision impairment, (2) number who did not use eyeglasses for distance vision correction and had distance vision impairment, (3) number who used eyeglasses for near vision correction and had near vision impairment, and (4) number who did not use eyeglasses for near vision correction and had near vision impairment. The prevalence of self-reported use of glasses was estimated using the results of this survey and the Medicare enrollment file. Data were analyzed from July 12, 2017, to November 30, 2017. Main Outcomes and Measures: Self-reported use of eyeglasses or contact lenses. Results: Of the estimated 43.9 million Medicare beneficiaries aged 65 years or older in 2015, approximately 40.5 million (92.4%; 95% CI, 91.6%-93.1%) reported using eyeglasses for either distance or near vision correction. Differences in sociodemographics were observed between those who reported using eyeglasses. Individuals who were older, were nonwhite, had lower educational levels, were less affluent, and had prior cataract surgery were significantly less likely to use eyeglasses. Approximately 27 million beneficiaries (61.7%; 95% CI, 60.3%-63.1%) used eyeglasses for distance vision correction, and approximately 37.2 million beneficiaries (84.8%; 95% CI, 83.8%-85.8%) used eyeglasses for near vision correction. Conclusions and Relevance: Potential sociodemographic disparities in eyeglass use by age, race/ethnicity, educational level, and income were identified. This finding suggests that innovative public policy solutions are needed to address these disparities among the large number of Medicare beneficiaries who use eyeglasses.

Association of Social Support Network Size With Receipt of Cataract Surgery in Older Adults.

Importance: Cataract-related vision impairment is an important public health issue that tends to affect older adults. Little is known about the association between older adults' social support networks and their likelihood of receiving cataract surgery. Objective: To determine if older adults with smaller social support networks are less likely to receive cataract surgery. Design, Setting, and Participants: Retrospective cohort study. The National Health and Aging Trends Study, a nationally representative US survey, administered annually from 2011 to 2015 to a cohort of Medicare beneficiaries 65 years and older with no cataract surgery prior to the start of the study. Main Outcomes and Measures: Multivariable logistic regression was performed to evaluate if the number of persons in an individual's social support network influenced whether that individual received cataract surgery during a given year of the study. Results: Overall, 3448 participants were interviewed from 2011 to 2015 for a total of 9760 observations. Of these observations, 3084 (weighted, 38.81%; 95% CI, 37.28-40.35) were aged 70 to 74 years, 5211 (weighted, 52.32%; 95% CI, 50.19-54.44) were women; 5899 (weighted, 78.53%; 95% CI, 76.29-80.61) were white, 2249 (weighted, 9.55%; 95% CI, 8.45-10.78) were black, 537 (weighted, 7.18%; 95% CI, 5.88-8.73) were Hispanic, and 303 (weighted, 4.74%; 95% CI, 3.56-62.9) reported other races. Medicare beneficiaries with smaller social support networks (0-2 individuals) were less likely to receive cataract surgery in a given year (adjusted odds ratio, 0.60; 95% CI, 0.37-0.96) than those with larger support networks (≥3 individuals). The adjusted predicted proportion of Medicare beneficiaries undergoing cataract surgery was 4.7% (95% CI, 2.7%-6.7%) and 7.5% (95% CI, 6.9%-8.1%) for those with small and large social support networks, respectively. Having fewer non-spouse/partner family members in the support network was associated with decreased odds of receiving cataract surgery (adjusted odds ratio, 0.60; 95% CI, 0.43-0.85), but having spouses/partners (adjusted odds ratio, 0.97; 95% CI, 0.77-1.22) and nonfamily members (adjusted odds ratio, 0.90; 95% CI, 0.72-1.11) did not have a significant association. Conclusions and Relevance: Medicare beneficiaries with fewer non-spouse/partner family members in their social support networks were less likely to receive cataract surgery. These findings suggest that attention should be given to patients with smaller support networks to ensure that they receive cataract surgery when it is indicated.

Development of a rapid point-of-care patient reported outcome measure for cataract surgery in India.

BACKGROUND: For patient undergoing cataract surgery in India, existing patient-reported outcome (PRO) measures are either not culturally relevant, have not been adequately validated, or are too long to be used in a busy clinical setting. We sought to develop and validate a brief and culturally relevant point-of-care PRO measure to address this need. METHODS: Twelve items from the Indian Visual Functioning Questionnaire (IND-VFQ) were selected based on preliminary data. Patients 18 years and older were prospectively recruited at Aravind Eye Care System in Madurai, India. Clinical and sociodemographic data were collected and the 12-item short-form IND-VFQ (SF-IND-VFQ) was administered pre- and post-operatively to 225 patients; Factor analysis and Rasch modeling was performed to assess its psychometric properties. RESULTS: One item that did not fit a unidimensional scale and had poor fit with the Rasch model was eliminated from the questionnaire. The remaining 11 items represented a single construct (no residual correlations> 0.1) and were largely unaffected by differential item functioning. Five items had disordered thresholds resolved by collapsing the response scale from four to three categories. The survey had adequate reliability (0.80) and good construct (infit range, 0.77-1.29; outfit range, 0.56-1.30) and content (item separation index, 5.87 logits) validity. Measurement precision was fair (person separation index, 1.97). There was evidence that items were not optimally targeted to patients' visual ability (preoperatively, - 1.92 logits; overall, - 3.41 logits), though the survey measured a very large effect (Cohen's d 1.80). In a subset of patients, the average time to complete the questionnaire was 2 min 6.3 s. CONCLUSIONS: The SF-IND-VFQ is a valid, reliable, sensitive, and rapidly administered point-of-care PRO measure to assess changes in visual functioning in patients undergoing cataract surgery in India.

Trends in Use of Ambulatory Surgery Centers for Cataract Surgery in the United States, 2001-2014.

Importance: Cataract surgery is commonly performed at ambulatory surgery centers (ASCs) and hospital outpatient departments (HOPDs). These venues differ in many ways, including surgical efficiency, patient throughput, patient safety, and costs per surgery. Objective: To determine trends in use of ASCs and HOPDs for cataract surgery from 2001 to 2014 and factors affecting the site of surgery. Design, Setting, and Participants: This retrospective longitudinal cohort analysis involved individuals 40 years and older who underwent cataract surgery between January 2001 and December 2014 from a nationwide US managed care network. Data were analyzed from February 2016 to February 2017. Main Outcomes and Measures: We identified all enrollees who underwent cataract surgery and determined whether the surgery was performed at an ASC or HOPD. We calculated the proportion of surgeries performed at each site each year from 2001 to 2014. Multivariable logistic regression identified characteristics of enrollees who had cataract surgery at an ASC vs a HOPD. We also assessed geographic variation in the proportion of cataract surgeries performed at ASCs in 306 communities throughout the United States. Results: Of the 369 320 enrollees included in this study, 208 319 (56.4%) were female, and the mean (SD) age was 66.3 (10.4) years. All enrollees underwent cataract surgery (531 325 surgeries) from 2001 to 2014. Of these, 237 046 (64.2%) underwent cataract surgery at an ASC. The proportion of cataract surgeries performed at ASCs increased from 43.6% in 2001 to 73.0% in 2014. Compared with enrollees with incomes less than $40 000, those with incomes greater than $100 000 were 20% more likely to undergo cataract surgery at an ASC (odds ratio, 1.20; 95% CI, 1.12-1.29). Enrollees with better overall health were no more likely to undergo cataract surgery at an ASC (odds ratio, 1.00; 95% CI, 0.99-1.00) than at an HOPD. Enrollees who lived in communities without certificate of need laws were more than twice as likely to have surgery at an ASC (odds ratio, 2.49; 95% CI, 2.35-2.63). The proportion of cataract surgeries performed at ASCs from 2012 to 2014 varied considerably, from 1.6% in La Crosse, Wisconsin, to 98.8% in Pueblo, Colorado. Conclusions and Relevance: We observed a large shift in the site of cataract surgery from HOPDs to ASCs from 2001 to 2014. Future research is needed to assess the effect of this transition in site of surgical care on patient access to surgery, surgical outcomes, patient safety, and societal costs.

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%.

Corneal biomechanical properties after laser-assisted in situ keratomileusis and photorefractive keratectomy.

BACKGROUND: The purpose of this study was to evaluate the effects of laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) on corneal biomechanical properties. METHODS: We used the ocular response analyzer to measure corneal hysteresis (CH) and corneal resistance factor (CRF) before and after refractive surgery. RESULTS: In all, 230 eyes underwent LASIK and 115 eyes underwent PRK without mitomycin C (MMC). Both procedures decreased CH and CRF from baseline. When MMC was used after PRK in 20 eyes, it resulted in lower corneal biomechanical properties at 3 months when compared to the other procedures, but all three procedures had similar values at 12 months. CONCLUSION: Significant but similar decreases in corneal biomechanical properties after LASIK, PRK without MMC, and PRK with MMC were noted.

Optimization and comparison of a 0.7 mm tip with the 0.9 mm tip on an active-fluidics phacoemulsification platform.

PURPOSE: To assess the effect of varying levels of torsional power on phacoemulsification efficiency using an active-fluidics phacoemulsification platform with a 0.7 mm Sonata tip. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: A 0.7 mm tip was used to emulsify 2.0 mm porcine lenses that had been hardened in formalin. The torsional power was varied from 10% to 100% at intervals of 10%, and efficiency and chatter were recorded. A comparison of the 0.7 mm tip with the 0.9 mm Balanced tip was also performed. Using a torsional power setting of 90% and 100%, the 0.7 mm tip and the 0.9 mm tip efficiency times were recorded. RESULTS: The study showed an increase in efficiency as torsional power increased. The relationship was linear and more efficient up to 90% (R2 = .8025, P = .0005). Chatter was only observed at a torsional power setting of 60%. In addition, a head-to-head comparison of the 0.7 mm tip with the 0.9 mm tip showed that both tips were statistically similar in efficiency times, despite the smaller diameter of the 0.7 mm tip. CONCLUSIONS: The optimum torsional power setting with the Centurion platform in conjunction with the 0.7 mm tip was 90%. The efficiency of the 0.7 mm tip and the 0.9 mm tip was statistically similar.

Intraocular pressure study using monitored forced-infusion system phacoemulsification technology.

PURPOSE: To optimize phacoemulsification efficiency by varying the intraocular pressure (IOP) using the Centurion Vision System, a monitored forced-infusion system. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Laboratory investigation. METHODS: Porcine lenses were soaked in formalin and divided into 2.0 mm cubes; 0.9 mm balanced tips were used. Intraocular pressure levels were tested from 30 to 110 mm Hg at 10 mm Hg intervals. Vacuum was set at 500 mm Hg, aspiration at 35 mL/min, and torsional power at 60%. Efficiency (time to lens removal) and chatter (number of lens fragment repulsions from the tip) were measured. RESULTS: There was a linear relationship between efficiency and IOP. Increasing IOP led to an increase in efficiency (ie, to a decrease in time necessary to remove the lens fragment) (R(2) = .5769, P = .0176). Chatter correlated with IOP in the range of 30 to 50 mm Hg (R(2) = .4506, P = .0448) and was minimal at higher IOPs. CONCLUSIONS: Increasing IOP in the monitored forced-infusion system improved efficiency. Chatter was also decreased or eliminated with increasing IOP. Additional studies will be required to understand the reasons for these findings. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Comparison of Vacuum and Aspiration on Phacoemulsification Efficiency and Chatter Using a Monitored Forced Infusion System.

PURPOSE: To evaluate the effect of vacuum and aspiration rates on phacoemulsification efficiency and chatter using a monitored forced infusion system. DESIGN: In vitro animal study. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, Utah. PROCEDURES: Formalin-soaked porcine lenses were divided into 2 mm cubes (tip diameter, 0.9 mm). Vacuum levels were tested at 200, 300, 400, and 500 mm Hg; aspiration rates at 20, 35, and 50 mL/min. Torsional power was set at 60% and intraocular pressure at 50 mm Hg. RESULTS: Increasing vacuum increased efficiency regardless of aspiration rates (R(2) = 0.92; P = .0004). Increasing aspiration further increased efficiency when vacuum was at 400 and 500 mm Hg (P = .004 for 20 vs 35 mL/min, P = .0008 for 35 vs 50 mL/min). At 200 and 300 mm Hg, efficiency only improved when increasing aspiration to 35 mL/min (P < .0001 with 20 vs 35 + 50 mL/min). Chatter improved with increasing vacuum, up to 400 mm Hg (P = .003 for 200 vs 300 mm Hg and P = .045 for 300 vs 500 mm Hg). A similar trend of improved chatter was seen with increasing levels of aspiration. CONCLUSIONS: Vacuum improved efficiency up to 500 mm Hg independent of flow. Flow has an additive effect on efficiency through 50 mL/min, when vacuum is at 400 mm Hg or higher, and only up to 35 mL/min at vacuums less than 400 mm Hg. Chatter correlated with both vacuum and flow such that increasing either parameter decreases chatter, up to 400 mm Hg with vacuum.

Comparison of a torsional and a standard tip with a monitored forced infusion phacoemulsification system.

PURPOSE: To compare the relative efficiency and chatter of the 30-degree 0.9 mm Kelman tip (standard tip) and Ozil Intrepid Balanced tip (torsional tip) with identical optimum settings. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Porcine nuclei were fixed in formalin and cut into 2.0 mm cubes. Lens cubes were phacoemulsified with standard and torsional tips at 60% and 100% torsional amplitude with 0%, 25%, 50%, 75%, and 100% longitudinal power with monitored forced infusion. Experiments were performed at a constant vacuum, aspiration rate, and intraocular pressure. RESULTS: Linear regression showed increased efficiency with up to 75% longitudinal power at 60% torsional amplitude for both tips (P = .046 standard; P = .0093 torsional). Longitudinal did not significantly increase efficiency at 100% torsional power for either tip. Torsional tips were on average 29% more efficient than standard tips throughout the range tested (P < .0001), and 100% torsional power was on average 45% more efficient than 60% torsional power (P = .0028). Chatter was minimal except at 100% longitudinal power, which was greater than at 75% longitudinal power (P < .0001). At 100% longitudinal power, torsional tips had more chatter than standard tips (at 60% torsional, P < .0001; at 100% torsional, P = .0022). CONCLUSIONS: Increasing up to 75% longitudinal power increased the efficiency at 60% torsional for standard and torsional tips. Torsional tips were more efficient than standard tips. Chatter was generally minimal. Torsional tips showed more chatter than standard tips at 100% longitudinal power. FINANCIAL DISCLOSURE: None of the authors has a financial or proprietary interest in any material or method mentioned.

Effect of pulsing ultrasound on phacoemulsification efficiency.

PURPOSE: To evaluate pulse type technology used to remove lens fragments during phacoemulsification. SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Lens nuclei soaked in 10 mL of 10% neutral buffered formalin for 2 hours were placed in 10 mL of balanced salt solution. Lenses were cut into 2 mm × 2 mm cubes; no more than 36 hours later, cubes were randomly selected for testing. Two aspiration and 2 vacuum settings were assessed at moderate- and high-flow and vacuum (30 mL/min and 300 mm/Hg, low-flow vacuum; 50 mL/min and 500 mm/Hg, high-flow vacuum), with continuous 50 milliseconds on and off (long pulse) and 6 milliseconds on and off (micropulse) ultrasound. RESULTS: There was a significant difference in efficiency favoring micropulse compared with combined long pulse and continuous pulse in high-flow vacuum at 80% power (P = .018) and between combined long pulse and continuous pulse versus micropulse in high-flow vacuum at 20% power (P = .019). Low-flow vacuum micropulse was more efficient than continuous (19.7%) (P < .0001) and long pulse (22.7%) (P < .0001). Continuous and long pulses were not significantly different from one other. There was a significant difference in chatter rates between high-flow vacuum and low-flow vacuum when all results were compared (P < .0001), with no additional significant differences found. CONCLUSION: Micropulse technology was better than continuous and long pulse at moderate but not high-flow and vacuum settings. At the higher setting, chatter was observed less often, with all modalities more efficient than the lower setting.

Bent versus straight tips in micropulsed longitudinal phacoemulsification.

OBJECTIVE: The aim of this study was to evaluate bent and straight phacoemulsification tips to determine which tip is more efficient in removal of lens fragments, using micropulsed longitudinal ultrasound in phacoemulsification. DESIGN: In vitro laboratory study. METHODS: The John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, was the study setting. Pig lenses hardened in a manner comparable with dense human cataracts were cut into 2-mm cubes and removed with micropulsed longitudinal ultrasound using settings previously shown to be optimally efficient (6 milliseconds on and 6 milliseconds off for a bent tip). To verify this time as most efficient for a straight tip, we also tested times of 5, 6, and 7 milliseconds time on and off. The tips were either straight or with a 20-degree bend. Twenty cubes were used for each comparative run. RESULTS: For the straight tip, 6 milliseconds on (1.56 ± 0.815 seconds) was significantly more efficient than 7 milliseconds on (2.45 ± 1.56 seconds, p = 0.001) and not significantly more efficient than 5 milliseconds on (1.69 ± 0.86 seconds, p = 0.43). Five milliseconds off time (1.45 ± 0.76s) was more efficient than 6 milliseconds (2.06 ± 1.37 seconds, p = 0.004) and 7 milliseconds off (2.18 ± 1.24s, p = 0.001). The straight tip was more efficient than the bent tip (1.38 ± 0.83 versus 2.93 ± 2.14 seconds, p = 0.006). CONCLUSIONS: Results are contrary to accepted common belief. Micropulsed longitudinal phacoemulsification is more efficient with a straight rather than a bent tip.

Impact of micropulsed ultrasound power settings on the efficiency and chatter associated with lens-fragment removal.

PURPOSE: To determine the optimum power settings in micropulsed ultrasound (US). SETTING: John A. Moran Eye Center Laboratories, University of Utah, Salt Lake City, Utah, USA. DESIGN: Experimental study. METHODS: Pig lenses hardened to be comparable to dense human cataracts were cut into 2.0 mm cubes and removed using micropulsed longitudinal US with previously optimized settings (6 milliseconds on and 6 milliseconds off and using a 0.9 mm 30-degree beveled bent phaco tip). The aspiration was set at 40 mL/min and the vacuum level at 550 mm Hg. Twenty lens cubes were tested with the power set from 10% to 100% in increments of 10%. Primary outcome measures were efficiency time (time to lens removal) and chatter (number of times the lens fragment visibly bounced off the tip). RESULTS: Efficiency time decreased with increasing power. There was a correlation between power and efficiency time (R(2) = 0.41, P = .046), which was more substantial between 30% and 100% power (R(2) = 0.71, P = .004). The mean number of chatter events did not differ significantly between power settings (R(2) = 0.012, P = .1195). CONCLUSIONS: There was a 5-fold increase in efficiency between 10% power and 20% power, which likely indicates that there is a minimum power threshold for efficient breakup of the lens. Between 20% and 100% power, there was a linear, strong, and statistically significant improvement in efficiency in these lens fragments. In addition, with micropulsed US there was little chatter or microchatter throughout the power range. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.