Biomedical subjects
Publications and source records attributed to James A Davison.
The ReSTOR intraocular lens presents a unique apodized diffractive design within a refractive foldable acrylic optic, which makes an unprecedented level of mulifocal optical performance available. We describe the history and principles of diffractive optics used in the development of this refractive-diffractive IOL.
PURPOSE: To compare the phacoemulsification times and powers used in 3 phacoemulsification machine configurations. SETTING: Wolfe Eye Clinic, Marshalltown, Iowa, USA. METHODS: A randomized prospective study of 410 consecutive cases was conducted. All cases were performed using the Alcon Legacy 20000 phacoemulsification machine. Configurations were the Standard Legacy 20000 machine (n=165), Advantec upgraded Legacy 20000 (n=112), and Advantec upgraded Legacy 20000 with NeoSoniX (n=133). Preoperative measurements included the patient's age and cataract grade using the nuclear color (NC) scale of the Lens Opacities Classification System III (LOCS III). Intraoperative measurements included machine-measured phacoemulsification time and average percentage of maximum power expenditure. An independent statistician performed analysis of covariance on NC for each of the machine configurations. RESULTS: The mean age in years and the NC value were similar in each group. There was no significant difference in phacoemulsification time in minutes among the 3 machines: Standard=1.17, Advantec=1.12, NeoSoniX=1.16. The average percentage of maximum power consumption was similar for Standard Legacy 20000 at 38.00% and Advantec Legacy 20000 at 37.97% but significantly less for Advantec Legacy 20000 with NeoSoniX at 27.56% (P<.001). With the NeoSoniX-incorporated machine, compared with Standard and Advantec, a 27.5% reduction in ultrasonic energy power expenditure was observed all grades of nuclear density. CONCLUSIONS: The addition of 15% amplitude NeoSoniX rotational energy reduced total ultrasonic power expenditure by 27.5% for all cataract nuclear densities.
A simultaneous surgeon and side-view camera video analysis demonstrated that in situ fracture requires more ultrasonic power behind the iris than the stop-and-chop technique, which requires a longer period of manipulation of larger fragments in the anterior chamber.
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A 74-year-old woman had uneventful phacoemulsification with implantation of a single-piece hydrophobic acrylic intraocular lens (IOL) (SA30AL) in her left eye. Two weeks after the surgery, the patient presented for ophthalmological consultation reporting pseudophakic dysphotopsia, which she had subjectively noted since surgery. Explantation/exchange of the IOL was performed 3 months after the surgery. The IOL was strongly attached to the capsule, which was fibrotic and contracted; explantation of the capsular bag complex in toto was done. To our knowledge, this is the first case of explantation of this IOL design with clinicopathological correlation.
PURPOSE: To report the incidence of neodymium:YAG (Nd:YAG) laser posterior capsulotomy after phacoemulsification and implantation of AcrySof (Alcon) intraocular lenses (IOLs). SETTING: Private practice, Wolfe Clinic, Marshalltown, Iowa, USA. METHODS: A retrospective diagnosis and procedure code review of 12419 consecutive cases having phacoemulsification and AcrySof IOL implantation from January 1995 through December 2002 was performed. The outcome parameter was the incidence of Nd:YAG laser posterior capsulotomies. RESULTS: An Nd:YAG laser posterior capsulotomy was performed in 763 (6.1%) of the 12419 cases. The incidence of posterior capsulotomy was approximately 1% at 1 year, increasing in linear fashion by approximately 1% to 2% per year. CONCLUSIONS: The Nd:YAG laser posterior capsulotomy rate after implantation of AcrySof IOLs was relatively low; the cumulative rate was approximately 1% to 2% new cases per year over a 7-year period, with a plateau suggested at year 6.
PURPOSE: To report the correlation of features of cataracts graded by the Lens Opacities Classification System, version III (LOCS III), with phacoemulsification energy expenditure and the balanced salt solution (BSS) volume used during cataract surgery. SETTING: Wolfe Clinic, Marshalltown, Iowa, USA. METHODS: This was a retrospective review of 2364 cases operated on by a single surgeon from January 1998 to July 2000 in which the cataract had been graded at the slitlamp using the 4 grading scales of the LOCS III: nuclear opalescence (NO), nuclear color (NC), cortical cataract (C), and posterior subcapsular cataract (P). Polynomial best-fit lines were derived using regression analysis correlating the 4 preoperative LOCS III characteristics with 3 intraoperative observations: machine-measured phacoemulsification time, mean power expenditure, and BSS volume. RESULTS: As determined by best-fit lines and their coefficient of determination (R(2)), there were exponential relationships between machine-measured phacoemulsification time and the degree of NC (R(2) = 0.48) and NO (R(2) = 0.40). Trends existed between NC and NO and the amount of BSS used (R(2) = 0.08 and R(2) = 0.07, respectively). No relationships were observed between the LOCS III classes of cataract, C and P, at any intraoperative observation. CONCLUSIONS: Exponentially, greater phacoemulsification energy was required as NC and NO increased. The LOCS III cataract grading system enhanced the ability to estimate ultrasonic energy expenditure and BSS volume use during phacoemulsification. Preoperative LOCS III cataract classification can help to create a more formally organized, integrated, customized operative plan.
PURPOSE: To compare the efficiency of surgical procedures using 2 phacoemulsification tips. SETTING: Wolfe Clinic, Marshalltown, Iowa, USA. METHODS: A randomized prospective study of 256 consecutive cases was conducted. The patients were adults having phacoemulsification by a modified in situ fracture technique. All cases were done by 1 surgeon using the Alcon Legacy 20000 phacoemulsification machine with high-vacuum cassettes and tubing. One of 2 45-degree Aspiration Bypass System (ABS) phacoemulsification tips was used. The straight tip has a 0.9 mm outside diameter (n = 127). The flared tip has a 0.76 mm outside diameter shaft that flares to a 1.02 mm tip (n = 129). Measurements at the time of surgery included metered phacoemulsification time, percentage power used, total phacoemulsification time, and milliliters of balanced salt solution (BSS(R)) used. RESULTS: No posterior capsule tear, vitreous loss, incision thermal damage, incision leak, or suture closure occurred. There were no cases of iris aspiration into the working end of the phacoemulsification needle; however, the iris was aspirated into the ABS opening of the flared tip in 1 case. Similar measurements for the straight and flared tips included, respectively, metered phacoemulsification time, 1.4 minutes each; mean power percentage, 41% and 39%; total phacoemulsification time, 2 minutes 11 seconds and 2 minutes 15 seconds; and overall BSS volume, 77 mL and 75 mL. The anterior capsule tear rates for straight (5.5%) and flared (1.6%) tips were similar. CONCLUSIONS: The flared ABS phaco tip with a 0.76 mm shaft outside diameter provided the physical advantages of shaft diameter reduction and required ultrasonic energy expenditures, BSS volumes, and surgical times similar to those of the straight ABS ultrasonic tip with a 0.9 mm outside diameter.
PURPOSE: To report the clinical performance characteristics of single-piece acrylic Alcon SA30AL and SA60AT intraocular lenses (IOLs). SETTING: A private practice in Marshalltown, Iowa, USA. METHODS: In a review of 2630 consecutive cases operated on from January 2000 through July 2001, ease of IOL insertion and integrity of the haptic architecture were evaluated in a prospective fashion at implantation. Subgroups of cases were studied prospectively to evaluate 3 factors: same-day incision competence after implantation (postoperative intraoperative pressure [IOP], 107 cases); 2- to 5-week A-constant validation (200 cases); 1-day, 2-week, and 1- and 5-month descriptions of optic centration with respect to pupil and capsule anatomy (79 cases); and a 1-day versus 9-month photographic comparison of IOL centration (70 cases). A retrospective evaluation of the population's diagnostic codes tabulated complications including increased postoperative iritis, cystoid macular edema, neodymium:YAG (Nd:YAG) laser intervention for posterior capsule opacification, and pseudophakic dysphotopsia. A retrospective review of a subgroup of 140 consecutive cases was done to categorize postoperative optic clarity. RESULTS: Overall, the IOLs were easy to implant with no haptic or optic damage using a forceps or the Monarch injector. Subgroup studies confirmed good performance in the following parameters: There were no cases of incision incompetence evidenced by an abnormally low postoperative IOP. The lowest postoperative IOP was 6 mm Hg, with the overall mean IOP increasing to 29 mm Hg from the 17 mm Hg measured a mean of 102 minutes after surgery. The manufacturer's published A-constant was almost identical to that obtained in review (118.4 versus 118.38 for the SA30AL and 118.35 for the SA60AT). In verbal descriptions, IOL optic centration was assessed to be within 0.4 mm of perfect in 75 (95%) of 79 cases. Slitlamp photographs showed that 52 (98%) of 53 IOLs were in the same position 9 months after surgery as on the day of surgery. One IOL optic appeared to rotate 14 degrees. There were no cases of decentration greater than 1.0 mm in either optic centration subgroup. Given a normal postoperative topical steroid regimen, there were no cases of substantially increased or prolonged iritis. There were 17 cases (0.65%) of macular edema. An Nd:YAG laser posterior capsulotomy was performed in 0.64% (13/2044) in the SA30AL group over a mean of 9 months (range 2 to 23 months) and in 0.34% (2/586) in the SA60AL group over a mean of 5.5 months (range 5 to 6 months). Pseudophakic dysphotopsia was diagnosed in 26 eyes of 18 patients (1% of 2630 cases), with 1 patient requiring an IOL exchange. Optic glistenings were observed in 11 (11%) of 100 SA30AL cases at a mean follow-up of 8 months. No glistenings in 40 cases were seen in the SA60AT group at a mean follow-up of 3 months. CONCLUSIONS: The single-piece acrylic lenses performed well in all regards. Although not as intense as observed with the earlier 3-piece designs, pseudophakic dysphotopsia occurred in a few patients with the single-piece acrylic lens. Intraocular lens exchanges with single-piece IOLs may be accomplished with less difficulty early rather than late.