About

William R. Barlow, Jr., MD, is an experienced comprehensive ophthalmologist and ocular surgeon with a specific interest in cataract and refractive surgery. He has experience performing complex cataract surgery, femtosecond laser cataract surgery, and refractive surgeries, such as LASIK, PRK, ICL, and clear lens extraction using premium intraocular lens technologies, including toric, multifocal, and accommodative intraocular lenses. He also provides medical and surgical care for a variety of other ocular conditions. Dr. Barlow is a team ophthalmologist for the Utah Jazz. His research interests include cataract surgical techniques, equipment, and intraocular lens calculations.

Research topics

• Computer Science
• Physics
• Geology
• Structural engineering
• Thermodynamics
• Medicine
• Electrical engineering
• Mathematics
• Surgery
• Acoustics
• Materials science
• Engineering

Selected publications

• Energy Output Variability Among Phacoemulsification Tips Using Calorimetry

  Medical Devices Evidence and Research · 2025-10-01

  articleOpen access

  Purpose: To determine if using different phacoemulsification (phaco) tips will impact thermal energy output utilizing calorimetry. Methods: The Alcon Centurion was used with the Infiniti OZil handpiece and balanced, hybrid, or MST Dewey A1 mini tip. Settings were 100% power, continuous torsional or longitudinal ultrasound, 0mmHg vacuum limit, and flow rate 12mL/min. Outflow tubing was removed from the handpiece and inflow tubing was manually occluded. The handpiece tip was placed into the calorimeter filled with 50mL of degassed deionized water and ultrasound was initiated for 1 minute. Temperature rise and cumulative dissipated energy (CDE) were recorded; ten trials were performed for each group. Results: Statistically significant differences in energy output, measured in Joules, were found between all three tips in both ultrasound modes. Balanced tips showed the highest output, Dewey tips had the lowest. Hybrid tips had significantly increased output in longitudinal mode, whereas Dewey tips had significantly decreased output in longitudinal mode. No significant differences were seen in CDE between tips in either ultrasound mode, but significant increases were seen in longitudinal mode within each tip. Conclusion: This study demonstrated differences in thermal energy production of three different phaco handpiece tips. This provides insight into how thermal injuries occur and what might cause these differences. Our methodology provides a novel way for accurate energy measurement at the tip, though it differs when compared to external energy production measurements. Surgeons should take into consideration the significant variability in thermal energy created by handpiece tips. Plain Language Summary: Modern cataract surgery employs phacoemulsification, a technique that breaks apart a cataract using ultrasonic energy. A rare but possible complication of this technology is thermal (heat) injury. Several factors contribute to energy generation during cataract fragmentation, such as friction at the incision site and impedance of flow rate. This study examines the thermal energy produced at the handpiece tip, where ultrasonic movement occurs. The energy delivered to the eye from the handpiece consists of mechanical energy in the form of kinetic and acoustic energy, leading to cavitation, mechanical disruption of the lens, and heat. It remains unclear how the design of phacoemulsification tips influences the energy transfer from piezoelectric crystals to the mechanical energy delivered to the eye. We used calorimetry to measure the thermal energy output, measured in Joules, between three different tips in longitudinal (forward and backward) and torsional (side to side) ultrasound modes, using the same settings, handpiece, and machine. The handpiece tip was submerged in the calorimetry chamber with water and operated for 60 seconds; a temperature probe measured the temperature change. The temperature changes were converted to energy and compared, and the energy measurement generated by the machine was recorded. We found significant differences in energy output between the three tips in both ultrasound modes, the Dewey tip demonstrated the lowest energy output and the balanced tip had the highest, in torsional and longitudinal mode. We found the measured energy differed significantly from the machine-generated measurement. These findings highlight the variability in energy output and expand on the potential contributing factors to energy generation and thermal injury in cataract surgery. Keywords: cataract surgery, output, thermal injury, ultrasound mode, variability

  PublisherOA PDFDOI

• Temperature Change of Ophthalmic Viscosurgical Devices in a Bi-Chamber Set-Up at a Flow of 0 and 20mL/min

  Clinical ophthalmology · 2023-02-01 · 1 citations

  articleOpen access

  Purpose: To understand the role of ophthalmic viscosurgical devices (OVDs) in corneal incision contracture (CIC). Specifically, the aim was to evaluate with the tip of the phacoemulsification needle free of OVD, how various OVDs near the tip and sleeve may transmit thermal energy to the incision site. Methods: A small chamber was filled with balanced saline solution (BSS), and a thin membrane was placed on the surface. OVD was placed atop the membrane. A temperature probe was placed in the OVD, while the handpiece pierced the membrane. The experiment was run both with and without flow and vacuum. Temperature measurements were gathered for each of the OVDs at four separate time points at 0 and 20mL/min flow. Results: As expected, there was a more pronounced temperature increase in all test groups with no fluid flow. While the temperature increase was not significantly different from BSS for any of the OVDs tested at either 0 or 20mL/min, Viscoat showed the most variable results at both flow settings. Conclusion: As long as the phaco tip is not in OVD, residual OVD near the incision is not exothermic and so not an additional risk for CIC.

  PublisherOA PDFDOI

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

  Clinical ophthalmology · 2022-04-01 · 1 citations

  articleOpen access

  Purpose: 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.

  PublisherOA PDFDOI

• Effect of low and passive flow on OVD thermal properties during phacoemulsification

  Canadian Journal of Ophthalmology · 2022-07-19 · 2 citations

  article
  PublisherDOI

• Measurement of Phacoemulsification Vacuum Pressure in the Oertli CataRhex3

  Clinical ophthalmology · 2022-06-01 · 5 citations

  articleOpen access

  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. Keywords: phacoemulsification, Oertli CataRhex 3, vacuum pressure, bottle height, flow rate

  PublisherOA PDFDOI

• Optimizing Tip Diameter in Phacoemulsification of Varying Lens Sizes: An in vitro Study

  Clinical ophthalmology · 2021-11-01 · 2 citations

  articleOpen access

  PURPOSE: We assessed the effect of two lens cube sizes, three tip sizes, and two ultrasound (US) approaches on phacoemulsification efficiency and chatter. METHODS: After porcine lens nuclei were soaked in formalin, we divided them into cubes measuring 2.0 mm or 3.0 mm. We collected efficiency and chatter data for 30-degree bent 19 G, 20 G, and 21 G tips with a continuous torsional US system; and for straight 19 G, 20 G, and 21 G tips with a micropulse longitudinal US system. RESULTS: The average time needed for removal was always higher for the 3.0 mm lens cube than for the 2.0 mm lens cube. Statistically significant differences were observed between the 19 G and 21 G tips with micropulse longitudinal US using a 2.0 mm cube and a 3.0 mm cube, and with continuous transversal US using a 2.0 mm lens cube and a 3.0 mm cube. We did not observe significant differences between 19 G and 20 G tips with either cube size in either US system. However, we noted identical trends for both cube sizes with both US approaches; 19 G tips performed better than 20 G and 21 G tips. CONCLUSION: Regardless of the lens size, 19 G needles were the most efficient, and had both the fewest outliers and the smallest standard deviations.

  PublisherOA PDFDOI

• Effects on phacoemulsification efficiency and chatter at variable longitudinal ultrasound settings when combined with constant torsional energy

  Journal of Cataract & Refractive Surgery · 2020 · 8 citations

  • Computer Science
  • Mathematics
  • Materials science

  PURPOSE: To evaluate longitudinal power settings for optimally efficient lens fragment removal, using the Centurion machine. SETTING: John A. Moran Eye Center, University of Utah, Salt Lake City, USA. DESIGN: Experimental study. METHODS: Porcine lens nuclei were cut into 2.0 mm cubes. Experiments were conducted at 100% torsional power; vacuum set at 500 mm Hg, aspiration 50 mL/min, and intraocular pressure 110 mm Hg. A 20-degree tip with a 30-degree bevel was used. Longitudinal power was tested between 20% and 100%. Efficiency (time for fragment removal) and chatter (the number of times the fragment bounced from the tip) were measured. RESULTS: A linear increase in efficiency was observed from 20% to 100% longitudinal power (R = 0.9281, slope = -0.0271). An efficiency slope change occurred at 60% power, with the largest incremental change in efficiency between 20% and 60% (R = 0.9756, slope = -0.0394) and a lesser change between 60% and 100% (R = 0.9827, slope = -0.0121). Chatter analysis showed minimal events at 20% to 60%, but a significant increase at >80% (P = .005). This increase appeared to be incremental (R = 0.8929). CONCLUSIONS: Increasing longitudinal power, with all other settings constant, increased efficiency. Greatest efficiency gains were observed between 20% and 60%. At 80% and 100%, chatter events increased significantly. With a goal of recommending optimally efficient settings while minimizing excess energy and chatter, adding 60% of longitudinal power to 100% torsional power was shown to be the best setting to increase efficiency and avoid repulsion in these vacuum and aspiration settings.

  PublisherDOI

• &lt;p&gt;Optimization of the Oertli CataRhex 3&lt;sup&gt;&amp;reg;&lt;/sup&gt; phacoemulsification machine&lt;/p&gt;

  Clinical ophthalmology · 2019-04-01 · 6 citations

  articleOpen access

  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%. Keywords: cataract, blindness, underserved countries, vacuum, aspiration rate, power

  PublisherOA PDFDOI

• &lt;p&gt;The effect of increasing power when grooving using phacoemulsification&lt;/p&gt;

  Clinical ophthalmology · 2019-04-01 · 8 citations

  articleOpen access

  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: <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.

  PublisherOA PDFDOI

• Impact of torsional micropulse on phacoemulsification efficiency and chatter

  Canadian Journal of Ophthalmology · 2019-04-03 · 8 citations

  article
  PublisherDOI

Frequent coauthors

• Jeff H. Pettey

  University of Utah

  84 shared

• Randall J. Olson

  79 shared

• Brian Zaugg

  77 shared

• Ashlie Bernhisel

  Mayo Clinic in Arizona

  59 shared

• Joshua Heczko

  Nassau University Medical Center

  32 shared

• Brian C. Stagg

  24 shared

• Sami Kabbara

  18 shared

• Isha Gupta

  Creative Commons

  16 shared

Education

• M.D.

  Medical College of Wisconsin

• Other

  John A. Moran Eye Center