Ellen Anderson Penno

Incidence and management of intraoperative and early postoperative complications in 1000 consecutive laser in situ keratomileusis cases.

OBJECTIVE To identify intraoperative and early postoperative complications of laser in situ keratomileusis (LASIK) surgery learning curve and to offer recommendations on prevention and management. DESIGN Retrospective noncomparative case series. PARTICIPANTS The first 1000 consecutive myopic LASIK eyes (April 1995-February 1997) operated on by one surgeon (HVG) were examined. INTERVENTION Myopic LASIK surgery was performed with the Chiron Corneal Shaper and NIDEK EC-5000 excimer laser. MAIN OUTCOME MEASURES The preoperative and 6-month postoperative spherical equivalent, best-corrected visual acuity, and corneal status were recorded, as was the incidence of intraoperative and early postoperative complications. The rate of retreatments was also recorded. RESULTS There were 32 (3.2%) intraoperative complications and surgical events recorded, including 19 (1.9%) microkeratome-related flap complications and 13 (1.3%) nonmicrokeratome-related surgical events such as inability to obtain sufficient suction. There were 18 (1.8%) postoperative complications requiring repositioning of microwrinkled or shifted flaps. Six-month spherical equivalent was -0.52 diopter [D] +/- 1.19 D for eyes with microkeratome complications, -0.56 D +/- 1.07 D for the group with nonmicrokeratome-related intraoperative events, and -0.78 D +/- 0.92 for eyes requiring postoperative flap repositioning. None of the 32 eyes with intraoperative complications and surgical events lost 2 or more lines of vision. One eye in the postoperative complications group lost two lines of vision. The rate of microkeratome complications related to surgical technique and the overall surgery times decreased over the course of the first 1000 myopic LASIK cases. CONCLUSION The complications encountered during the early learning curve of LASIK surgery have not in this series resulted in a significant loss of best-corrected visual acuity. With increasing surgical experience, the incidence of complications, along with surgical times, has decreased.

Accuracy of Orbscan pachymetry measurements and DHG ultrasound pachymetry in primary laser in situ keratomileusis and LASIK enhancement procedures

Purpose: To assess the accuracy and variability in pachymetry measurements obtained by Orbscan and by DGH ultrasound in primary laser in situ keratomileusis (LASIK) and LASIK enhancement procedures. Setting: Gimbel Eye Centre, Calgary, Alberta, Canada. Methods: A retrospective analysis of 906 consecutive primary LASIK and 183 consecutive LASIK enhancement procedures for which preoperative DGH ultrasound and Orbscan pachymetry measurements were obtained. The theoretical residual corneal thickness was compared to measurements by both instruments in 60 eyes that had primary procedures and enhancements. Results: In primary LASIK eyes, the DGH ultrasound measurements were thicker than the Orbscan measurements by a mean of 18.4 &mgr;m ± 17.4 (SD). The DGH ultrasound measurements were thicker than the Orbscan measurements by a mean of 50.1 ± 40.7 &mgr;m in preenhancement pachymetry measurements. The DGH ultrasound measurements were consistent with theoretical residual corneal thickness, 493.0 ± 42.0 &mgr;m versus 487.0 ± 31.0 &mgr;m (P = .65), while Orbscan measurements were statistically less than the theoretical residual corneal thickness, 431.0 ± 42.0 &mgr;m versus 468.0 ± 39.0 &mgr;m (P = .0001). Conclusion: DGH ultrasound was a more accurate measurement of corneal pachymetry than Orbscan. The discrepancies between DGH ultrasound and Orbscan pachymetry measurements were more prominent in eyes that had had LASIK.

Intraoperative management of posterior capsule tears in phacoemulsification and intraocular lens implantation.

OBJECTIVE This paper presents the incidence, causes, and management of posterior capsule (PC) tears and their postoperative outcomes in a large series of eyes that underwent cataract removal and intraocular lens (IOL) implantation, operated on by one surgeon. DESIGN Retrospective, noncomparative case series. PARTICIPANTS Eighteen thousand four hundred seventy consecutive eyes (1992-1999) were reviewed with the assistance of electronic medical records for incidence of PC tears in patients seeking treatment at an outpatient cataract surgery clinic. INTERVENTION Eyes in this series underwent continuous curvilinear capsulorrhexis (CCC), nucleofractis phacoemulsification, and IOL implantation under topical anesthesia. Different intraoperative surgical strategies such as posterior continuous curvilinear capsulorrhexis (PCCC) were used in the management of PC tears. MAIN OUTCOME MEASURES Routine preoperative and postoperative visual and refractive outcomes were recorded, including incidence of lens capsule tears, IOL position, and postoperative complications. RESULTS Posterior capsule tears occurred in 83 of 18,470 eyes, resulting in an overall incidence of 0.45%. Of these 83 eyes with PC tears, 49% received vitrectomy. Fifty-one of 83 PC tears (61.4%) were amenable to be converted to PCCC. Of these 51 procedures, 50 eyes had PC IOL in-the-bag fixation. One eye had PCCC with optic capture. There were no eyes with dropped nuclei or nuclear fragments requiring pars plana vitrectomy. Seventeen eyes (20.5%) had Neuhann anterior capsule rhexis fixation with the haptics placed in the sulcus and IOL securely in the bag. Ten eyes (12.1%) had the IOL placed in the sulcus, and 5 eyes (6.0%) required anterior chamber IOL fixation. None of the 83 PC tears resulted in clinically evident cystoid macular edema, retinal detachment, or endophthalmitis. CONCLUSIONS With an intact CCC and with conversion of PC tears to PCCC, in-the-bag fixation of IOLs can be achieved in most eyes.

Simultaneous bilateral laser in situ keratomileusis: Safety and efficacy1

OBJECTIVE To compare the safety and efficacy of simultaneous bilateral to sequential bilateral laser in situ keratomileusis (LASIK) surgery for the correction of myopia. DESIGN Retrospective, nonrandomized, comparative trial. PARTICIPANTS A total of 2142 consecutive simultaneous and sequential bilateral myopic LASIK surgery eyes operated from March 1996 through June 1998 for the correction of myopia were reviewed. INTERVENTION Two surgeons (HVG and JAV) performed myopic LASIK using the Nidek EC-5000 excimer laser and either the Chiron Automated Corneal Shaper or the Bausch & Lomb Hansatome microkeratome. MAIN OUTCOME MEASURES The incidence of intra- or perioperative complications for sequential and simultaneous bilateral LASIK for myopia was recorded. Refractive and visual outcomes at 3 to 6 months postoperative were analyzed. Deviations from targeted spherical equivalent (SE), uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and retreatment rates are reported. RESULTS Laser in situ keratomileusis was performed on the first eye of 1853 patients scheduled for simultaneous bilateral myopic LASIK. Of these, 28 (1.5%) first eyes had intraoperative or perioperative complications. The second eye surgery was cancelled in 11 cases, and 1842 second eyes completed simultaneous surgery; 13 (0.7%) intraoperative or perioperative complications occurred. Of these 41 complications in simultaneous cases, 1 eye lost 1 line of BCVA at 6 months follow-up. Two hundred eighty-nine patients were scheduled for sequential bilateral myopic LASIK. Five (1.8%) first eyes of the sequential cases had intraoperative complications compared with four (1.4%) sequential second eyes. There was no loss of BCVA in any sequential bilateral case with complications at a minimum at 6 months follow-up. There was no statistically significant difference between intra- and perioperative complication rates comparing simultaneous to sequential bilateral LASIK. Three to 6 months postoperative visual and refractive data were reviewed; except when comparing simultaneous first eye postoperative SE to sequential first eye, there was no statistically significant difference in refractive or visual outcomes, including deviation from targeted SE, UCVA, BCVA, and retreatment rates. CONCLUSION Simultaneous bilateral LASIK is as safe and effective as sequential surgery. Simultaneous bilateral LASIK may offer several benefits to the patient.

Diffuse lamellar keratitis: isolation of endotoxin and demonstration of the inflammatory potential in a rabbit laser in situ keratomileusis model

Purpose: To systematically examine sources of endotoxin contamination in eye centers as a potential cause of diffuse lamellar keratitis (DLK) and to demonstrate the inflammatory potential of endotoxin in a rabbit model of laser in situ keratomileusis (LASIK) surgery. Setting: University of Calgary, Calgary, Alberta, Canada. Methods: In this prospective study, all water sources that routinely come in contact with LASIK instruments, including sterilizer reservoirs, eyedrops, microkeratome blades, and cleaning solutions, were examined for endotoxins at 5 eye centers. Bacterial cultures were performed on water samples from 5 sterilizer reservoirs. A LASIK flap was created in 8 rabbit eyes using an Automated Corneal Shaper® microkeratome (Bausch & Lomb). The flaps were reflected, and a dose of endotoxin at various concentrations was placed on the interface. After 1 minute, the flap was irrigated and repositioned. The rabbit eyes were examined daily with a slitlamp biomicroscope for 3 days for the development of DLK, which was classified on a scale from grade 1 to 4 (mild to severe). The rabbits were killed at the conclusion of the study, and the interfaces were stained to rule out infectious etiologies. Results: Endotoxin was detected in significant concentrations in tap water, filtered and distilled water, instrument washbasins, and sterilizer reservoirs at all 5 centers. The cultures of the water samples taken from the sterilizer reservoirs ranged from no growth to the presence of >100 colony‐forming units of Flavobacterium and Pseudomonas aeruginosa. Endotoxins caused DLK‐like interface inflammation in all eyes tested. Examination of stained scrapings showed no microorganisms in the interface of the rabbit eyes. Conclusion: Endotoxin contamination was detected in water sources that routinely come in contact with LASIK instruments. Endotoxins were capable of inducing interface inflammation in a rabbit model and may therefore be a significant factor in epidemic DLK.

Late traumatic flap dislocation after laser in situ keratomileusis

&NA; Three patients who had laser in situ keratomileusis (LASIK) experienced severe direct corneal trauma 3 to 38 months postoperatively. Flap dislocation resulted in all 3 patients. Presentation following trauma ranged from a few hours to 9 days. All patients were successfully managed by surgical flap repositioning, and all maintained a best corrected visual acuity of 20/20. A literature review of traumatic flap dislocation cases and the most recent methods of diagnosis and management are included.

Combined cataract surgery, intraocular lens implantation, and viscocanalostomy.

PURPOSE To describe 2 techniques of combined viscocanalostomy and phacoemulsification and report the results. SETTING Gimbel Eye Centre, Calgary, Alberta, Canada. METHODS Combined viscocanalostomy, phacoemulsification, and intraocular lens implantation was performed in 83 eyes. A shared scleral incision was made in 46 eyes and a clear corneal incision separate from the viscocanalostomy site, in 37 eyes. A retrospective review of these cases was performed. RESULTS Intraocular pressure (IOP) was significantly lower in both groups 2 and 8 weeks and 6 months postoperatively. The decline in IOP postoperatively over time was also comparable. There were no cases of hypotony, choroidal detachment, filtrating bleb, or postoperative cystoid macular edema in either group. Complications included IOP spikes in 2 eyes in the shared-incision group at 1 day (to 43 and 30 mm Hg, respectively). In early shared-incision cases, there was 1 obvious Descements puncture in 1 eye and a torn scleral flap requiring extra suturing in another eye. CONCLUSION Combined viscocanalostomy, cataract extraction, and IOL implantation was safe and efficacious in lowering IOP whether a shared scleral incision or a separate clear corneal incision was used for phacoemulsification.

Effect of contact lens wear on central corneal thickness measurements

Purpose: To compare central corneal thickness measurements as a function of contact lens wear in patients presenting for refractive surgery. Setting: Gimbel Eye Centre, Saskatoon, Saskatchewan, Canada. Methods: A retrospective study of charts yielded 634 eyes meeting the inclusion criterion. Pachymetry measurements of spectacle‐wearing control eyes were compared to those of full‐time soft contact lens wearers and rigid gas‐permeable contact lens wearers. All measurements were taken with the DGH ultrasonic pachymeter by a single observer. Results: Soft contact lens wearers had a mean reduction in corneal thickness measurements of 22 &mgr;m compared to the control population (P = .00001). Rigid gas‐permeable lens wearers had a reduction of 24 &mgr;m compared to the control population (P = .00001). Conclusion: There was a clinically significant reduction in corneal thickness measurements associated with full‐time contact lens wear.

Prevention and Management of Microkeratome-related Laser in situ Keratomileusis Complications

PURPOSE To review the most commonly encountered laser in situ keratomileusis (LASIK) microkeratome-related complications, and the most up-to-date methods in their prevention and treatment. METHODS A review of microkeratome-related complications including epithelial complications, bleeding, thin flap, button hole, free cap, incomplete pass, and corneal perforation was conducted. The most recent techniques for prevention and treatment of each complication were included. RESULTS AND CONCLUSION Microkeratome complications are difficult to predict. With proper attention to anatomical and mechanical considerations, many can be reduced or prevented. [J Refract Surg 2000;16(suppl):S226-S229].

The effect of transmission bandwidth on the quality of ophthalmological still and video images

We have examined the minimum realtime transmission speed for video-angiography with the Rodenstock scanning laser ophthalmoscope (SLO) with respect to spatial and contrast resolution. An SLO fluorescein video-angiography sequence was recorded using high-quality media and relayed to a remote site at transmission speeds ranging from T3 (4.5 Mbit/s) to 0.125 T (197 kbit/s). Images were compared with each other subjectively by an ophthalmologist and objectively with image processing software. When compared qualitatively there was little difference between the T3 andT1 images. The T1 images scored well on clarity and contrast, while 0.5 T was satisfactory but inferior to T1. Transmission speeds below 0.5 T were inadequate. The digital analysis showed a slight difference between T3 and T1. We calculated that there was up to a 92% loss of resolution at 0.25T and up to a 98% loss at 0.125 T. Based on our quantitative and qualitative analysis, a T3 line provided the highest bandwidth and best resolution, as expected. However, 0.5T gave satisfactory results for realtime consultations and appears to be the minimum speed required for ophthalmic purposes, producing few motion artefacts and good resolution.