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Biomedical subjects

Alan S Crandall

Publications and source records attributed to Alan S Crandall.

12 recordsLinked to original sources
PubMed2006

Intraocular lens exchange due to incorrect lens power.

PURPOSE: To evaluate patients who had intraocular lens (IOL) exchange for unexpected postoperative refractive errors, determine the sources associated with the errors, and derive an empiric approach to estimating the power for IOL exchange. DESIGN: Retrospective review of interventional case series. PARTICIPANTS: Twenty-two eyes that underwent IOL exchange for correcting unexpected refractive errors after cataract surgery with IOL implantation were reviewed. INTERVENTION: All the IOLs for IOL exchange were placed in-the-bag. The same type of IOLs was used for original IOL implantation and IOL exchange in 91% (20/22) of eyes. MAIN OUTCOME MEASURES: Uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), refraction, and reasons for IOL exchange. The equation derived from refractive change and change in IOL power was developed to calculate IOL power for exchange. RESULTS: Of the 22 cases, the identified reasons were keratometry errors in 5 (23%) and incorrect axial length (AL) determination in 3 (14%). In 3 other cases, a wrong IOL was implanted. After IOL exchange, 82% (18/22) of eyes were within +/-0.50 diopters (D) and 86% (19/22) within +/-1.00 D of emmetropia. Uncorrected visual acuity was 20/40 or better in 82% of eyes, and BSCVA was 20/40 or better in 95% (21/22) of eyes. The correlation between change of refraction and IOL power was significant (P<0.002). CONCLUSIONS: Among the identified causes, incorrect corneal power determination was the most frequent reason for incorrect IOL power implantation, followed by error in AL measurement and inserting a wrong IOL. The pre-exchange refraction can be used theoretically to calculate the IOL power for exchange.

Cataract Extraction↗
PubMed2006

Ab externo scleral suture loop fixation for posterior chamber intraocular lens decentration: clinical results.

PURPOSE: To evaluate the efficacy and safety of an ab externo suture retrieval and scleral fixation technique in the treatment of subluxated posterior chamber intraocular lenses (PC IOLs). SETTING: Academic tertiary care centers. METHODS: Surgical databases from 2 surgeons were reviewed for consecutive cases from March 2000 to April 2004 in which the ab externo scleral suture fixation technique was used and a minimum follow-up of 3 months was completed. Patient charts were reviewed for 15 eyes that had decentered in-the-bag PC IOLs, 12 eyes with subluxated sulcus or bag-sulcus positioned PC IOLs, and 3 eyes with PC IOLs dislocated into the vitreous. RESULTS: The mean time from cataract extraction to PC IOL stabilization was 3.4 years (range 2 days to 10.9 years). Surgical repositioning was successfully performed in all patients. After a mean follow-up of 14.7 months, the mean best corrected visual acuity (BCVA) improved from 20/140 to 20/40 (P = .0001). All patients had stable or improved BCVA. All patients with a successfully completed procedure achieved an adequately centered PC IOL postoperatively. One patient (3.3%) developed a significant intraoperative vitreous hemorrhage requiring the procedure to be aborted, but reoperation 3 months later was successful. Postoperative complications included persistent elevated intraocular pressure in 2 eyes (6.7%) and chronic cystoid macular edema in 1 eye (3.3%) that resolved with medication. CONCLUSION: The ab externo suture loop retrieval and scleral fixation technique was effective in repositioning decentered, subluxated, or dislocated PC IOLs with excellent visual outcomes.

Adolescent↗
PubMed2006

Analysis of intraocular lens power calculation for eyes with previous myopic LASIK.

PURPOSE: To evaluate the effectiveness of a manual keratometry (K) adjusted value for intraocular lens (IOL) power calculation in patients who underwent cataract surgery following previous myopic LASIK. METHODS: Sixteen eyes of 14 consecutive patients who underwent cataract surgery after previous LASIK were evaluated retrospectively. All IOL powers were calculated using an adjusted K value (K minus 1.0 diopter [D]) with the Binkhorst II formula aiming for -0.75 to -1.00 D final refraction. Additionally, the IOL power for each eye was retrospectively calculated using K, refractive-derived K, and adjusted K with the Binkhorst II, Holladay I, and SRK/T formulas. The final refraction was used as a criterion of accuracy of each approach. RESULTS: Uncorrected visual acuity > or = 20/40 was achieved in 14 (87.5%) of 16 eyes. The mean postoperative spherical equivalent refraction was -0.41 +/- 0.57 D (range: +0.50 to -2.00 D). Twelve (75%) of 16 eyes were within +/- 0.50 D of emmetropia and 15 (94%) of 16 eyes were within +/- 1.00 D. No eye was > +1.00 D. CONCLUSIONS: Using an adjusted K with the Binkhorst II formula, aiming for -0.75 to -1.00 D, and with the Holladay I formula, aiming for -0.50 to -1.00 D, measuring K with a regular manual keratometer permits determination of an IOL power after myopic LASIK without the need of preoperative LASIK refractive data.

Adult↗
PubMed2005

A retrospective study of endophtalmitis rates comparing quinolone antibiotics.

PURPOSE: To compare endophthalmitis rates between topical quinolone antibiotics over a four-year period in a university setting. DESIGN: Retrospective, cross-sectional (prevalence) study. METHODS STUDY POPULATION: Nine thousand seventy-nine patients who underwent a phacoemulsification procedure at a University Eye Center. INTERVENTIONS: The following interventions were conducted: use of a nosocomial infectious reporting database retrospective analysis of prospectively collected data to establish endophthalmitis rates; prevalence analysis of postoperative quinolone antibiotics; analysis of endophthalmitis rate vs postoperative quinolone prescribed. MAIN OUTCOME MEASURES: Occurrence of endophthalmitis after cataract surgery. RESULTS: During a four-year period involving 9079 phacoemulsification procedures, 26 cases of bacterial postoperative endophthalmitis were reported (rate = 0.286%). Eight of the 26 cases were considered complicated; 18 cases were uncomplicated. Among cases performed during this period, postoperative prescription volumes for ciprofloxacin (Ciloxan, Alcon Laboratories, Inc., Fortworth, Texas) and ofloxacin (Ocuflox, Allergan, Inc., Irvine, California) antibiotic drops were nearly identical, with 4538 patients receiving ciprofloxacin (49.98%) and 4541 patients receiving ofloxacin (50.02%). There were 22 endophthalmitis patients (85%) who had used topical ciprofloxacin and 4 patients (15%) who had used topical ofloxacin postoperatively. The difference in infectious rates between antibiotics was highly significant (P < .00026). For uncomplicated cases, 14 patients received ciprofloxacin and 4 patients received ofloxacin. This difference was also significant (P < .015). CONCLUSIONS: Differences in pharmacokinetic and pharmacodynamic properties exist among quinolone antibiotics, which may affect endophthalmitis incidence following cataract surgery.

Administration, Topical↗
PubMed2005

Changing indications for and improving outcomes of intraocular lens exchange.

PURPOSE: To evaluate the indications for and outcomes of intraocular lens (IOL) exchange at the same clinical setting over the past decade, as well as compare the efficacy and safety of anterior chamber lens (AC-IOL) and posterior chamber lens (PC-IOL) implantation for IOL exchange. DESIGN: Retrospective, nonrandomized case series. METHODS: The charts of all patients who had an IOL exchange at the Eye Institute of Utah between January 1998 and December 2004 were reviewed. The rate, indications, and outcomes are compared with the data of our previous study conducted between 1986 and 1990. RESULTS: This study comprised 51 eyes of 51 consecutive patients. The rate of IOL exchange was 0.77% of all cataract surgeries during the time considered. Incorrect IOL power (41.2%), decentration/dislocation (37.3%), and glare (7.8%) were the most common indications for IOL exchange. An AC-IOL was used in 14 eyes (27.5%) and a PC-IOL in 37 eyes (72.5%) for IOL exchange. None of the PC-IOLs was sutured to the sclera or iris. Overall, 90.2% of patients obtained a best-spectacle corrected visual acuity (BSCVA) of 20/40 or better. All eyes in AC-IOL group and 94.6% of eyes in PC-IOL group maintained within 1 line or improved 2 to 5 lines of the pre-exchange vision. CONCLUSIONS: The improvements in IOL design and materials as well as surgical techniques have greatly minimized the incidence, changed the indications for, and improved the visual outcomes of IOL exchange over the past decade. Our study suggests that the open loop, flexible AC-IOL poses no greater risk than PC-IOL with respect to visual outcome and safety for IOL exchange. An AC-IOL may be preferable to a PC-IOL suture fixation for IOL exchange in the absence of posterior capsular support.

Adult↗
PubMed2005

Optimal timing of capsular tension ring implantation: Miyake-Apple video analysis.

PURPOSE: To evaluate the appropriate timing for capsular tension ring implantation in cases of zonular weakness either prior to or after lens extraction using Miyake-Apple video analysis. SETTING: John Moran Eye Center, Salt Lake City, Utah, USA. METHODS: Four cadaver eyes were prepared using a standard Miyake-Apple protocol with image capture using digital video recording. After continuous curvilinear capsulorhexis and hydrodissection/viscodissection were performed, 2 eyes had early capsular tension ring implantation (CTR) and 2 eyes had CTR implantation after lens extraction. The 12.3 mm CTR was implanted in all eyes. Capsular bag torque and displacement, zonular elongation and stress, and ease of CTR placement were evaluated in each eye. RESULTS: Early CTR implantation resulted in significantly increased capsular torque and displacement of up to 4.0 mm compared to insertion in an empty capsular bag. There was significant zonular elongation and tension during early placement. CONCLUSION: In terms of minimizing further zonular stress and damage and capsular destabilization, the ideal timing for CTR placement is after lens extraction and decompression of the capsular bag.

Biocompatible Materials↗
PubMed2005

Nonpenetrating glaucoma surgery.

Nonpenetrating glaucoma surgery continues to evolve and improve. New technical refinements and increased experience among its practitioners have led to improved efficacy and longer duration of filter survival. These refinements include the use of intraoperative and postoperative antimetabolites, adjunctive space-maintaining devices, and postoperative yttrium-aluminum-garnet laser goniopuncture. Deep sclerectomy and viscocanalostomy vary significantly in their surgical approaches and mechanisms of aqueous outflow. An understanding of the microanatomy of the aqueous outflow structures is necessary to gain surgical access to Schlemm's canal and to augment aqueous outflow surgically through the trabecular meshwork. Indications and contraindications for nonpenetrating glaucoma surgery are discussed.

Glaucoma↗
PubMed2002

Topical versus retrobulbar anesthesia for combined phacotrabeculectomy: prospective randomized study.

PURPOSE: To compare the safety and efficacy of topical and retrobulbar anesthesia for combined phacotrabeculectomy. SETTING: Tertiary-care university hospital ambulatory surgical center. METHODS: In this prospective study, 40 consecutive patients having combined phacotrabeculectomy were randomized to receive topical (n = 20) or retrobulbar (n = 20) anesthesia. Operating conditions, patient comfort, and surgical outcome were evaluated. RESULTS: There was no significant between-group difference in operating conditions (P =.56), pain during (P =.41) or after (P =.23) surgery, or supplemental anesthesia required (P =.49). Few patients in either group were bothered by tissue manipulation or the microscope light, although more patients in the topical group were slightly bothered by touch sensation (P =.05). Chemosis, subconjunctival hemorrhage, and eyelid hematoma were seen almost exclusively in the retrobulbar group (P <.05). Inadvertent eye movement was present more frequently in the topical group (P =.04), although this did not pose a problem to the surgeon. CONCLUSION: Topical anesthesia is a safe and effective alternative to retrobulbar anesthesia for combined phacotrabeculectomy.

Administration, Topical↗
PubMed2002

A comparison of topical and retrobulbar anesthesia for trabeculectomy.

PURPOSE: To compare the safety and efficacy of topical versus retrobulbar anesthesia for primary trabeculectomy METHODS: A prospective study of 36 consecutive patients undergoing trabeculectomy who were randomized to receive topical (n = 18) or retrobulbar (n = 18) anesthesia. Operating conditions, patient comfort, and surgical outcome were evaluated. SETTINGS: Tertiary-care university hospital ambulatory surgical center. RESULTS: There were no differences in operating conditions (P = 0.14), pain during (P = 0.54) or after (P = 0.76) surgery, or supplemental anesthesia required (P = 0.34) between the two groups. Very few patients in either group were bothered by touch sensation, tissue manipulation, or the microscope light. Chemosis, subconjunctival hemorrhage and eyelid hemorrhage were seen exclusively in the retrobulbar group (P <0.03), and were all attributable to the injection. Inadvertent eye movement was present more frequently in the topical group (P = 0.01), although this did not pose a problem to the surgeon. No surgical complications were encountered in either group. CONCLUSION: Topical anesthesia is a safe and effective alternative to retrobulbar anesthesia for primary trabeculectomy.

Aged↗