Biomedical subjects

Ronald R Krueger

Publications and source records attributed to Ronald R Krueger.

6 recordsLinked to original sources

PubMed2003

Secondary microkeratome-induced flap interference with the pathway of the primary flap.

PURPOSE: To report a flap-related complication that occurs when a secondary microkeratome pass interferes with the pathway of a complicated first microkeratome pass. DESIGN: Small, retrospective, noncomparative, interventional case series. PARTICIPANTS: Three patients. METHODS: In three cases, each patient experienced a different flap-related complication with the original surgery, followed by interference of a secondary flap with the primary. The first patient experienced a free cap, followed by an interference of the secondary flap at the nasal portion of the free cap. The second patient experienced a buttonhole, followed by secondary flap interference in the superior quadrant adjacent to the buttonhole. The third patient experienced a decentered flap originally, followed by secondary flap interference temporally. MAIN OUTCOME MEASURES: Visual result after secondary microkeratome-induced flap-related complications. RESULTS: All three patients had poor best spectacle-corrected visual acuity on the first postoperative day, with subsequent visual recovery. All three patients had induced flattening on keratometry along the axis where stromal tissue was removed. In addition, two patients required multiple enhancements to achieve desired visual outcomes. CONCLUSIONS: Complications related to the primary microkeratome pass add further risk for complications to arise during a second microkeratome pass. A secondary microkeratome pass should be attempted only if the original flap cannot be identified, if it is the result of primary flap complication, or if the desired treatment zone is notably larger than the diameter of the original flap. Intraoperative pachymetry of the residual stromal bed should be performed routinely. It is important to examine the stromal bed closely for loose or displaced slivers of tissue and to remove them before excimer treatment.

Adult↗

PubMed2003

Update on customized excimer ablations: recent developments reported in 2002.

Customized corneal ablation is an exciting frontier in refractive surgery that incorporates wavefront technology to detect and correct higher order aberrations in addition to spherocylindrical refractive errors. The goal is to achieve super normal vision in terms of acuity and contrast. As the concept of wavefront customized ablations is still new, there are a number of aspects of its clinical application that need analysis and understanding. Numerous reports have appeared in the literature during the past year that address the developments, concerns, and limitations of wavefront technology and custom ablation. We have attempted to summarize and discuss the significant reports in this current review. Our focus is on the optical and physiologic limits of wavefront customized correction, including the effect of accommodation, aging, and flap creation on the aberration profile. In addition, we also present the laser technology requirements, and clinical outcomes of customized excimer ablations that are reported to date.

Cornea↗

PubMedDate not supplied

Changes in mesopic vision after photorefractive keratectomy for myopia.

PURPOSE: To evaluate the mesopic functions of excimer laser treated eyes with different treatment diameters and different laser beam delivery systems. METHODS: In Group 1, 38 eyes were treated with the Aesculap Meditec MEL 60 ArF scanning laser beam excimer laser. The treatment diameter was 5.0 mm. In Group 2, 38 eyes were treated with the Aesculap Meditec MEL 70(G-Scan) flying spot excimer laser; the chosen treatment diameter was 6.5 mm. In Group 3, there were 38 eyes with no treatment; vision was corrected only with spectacles (control group). All eyes had 20/20 best spectacle-corrected visual acuity before surgery, as did the control group. Measurements were carried out preoperatively and at 12 months following surgery. All eyes exhibited normal corneal wound healing, and subepithelial haze was <0.5 according to Hanna's scale. Mesopic functions (mesopic vision and glare sensitivity) were tested with the Mesoptometer II. RESULTS: The average preoperative refractive error in Group 1 was -3.40 D; in Group 2, -3.38 D; in Group 3, -3.44 D. In Group 1, 34% of the treated eyes met the night driving requirements (recognition at 1:5 contrast level), whereas in Group 2, 85%, and in Group 3, 95% of the eyes fulfilled this criteria. When contrast vision was tested under glare conditions in Group 1, 31.6%; in Group 2, 80%; and in Group 3, 94.7% of the eyes identified the target orientation (Landolt ring) at contrast level 1:5. CONCLUSIONS: The unoperated spectacle wearers had better results in all tested functions. The larger 6.5-mm treatment diameter with the use of the flying spot laser beam delivery system resulted in better mesopic function and contrast vision under mesopic conditions than the smaller 5.0-mm diameter.

Adult↗

PubMedDate not supplied

Aberration-sensing and wavefront-guided laser in situ keratomileusis: management of decentered ablation.

PURPOSE: To clarify the feasibility of aberration-sensing and wavefront-guided laser in situ keratomileusis (LASIK) to manage grossly decentered ablation and to discuss the limitations of the technology. METHODS: Three patients with previous decentrations of the ablation zone between 1.5 to 2.0 mm were scheduled for wavefront-guided LASIK. All patients reported monocular diplopia and halos. Wavefront aberrations were measured with a Tscherning-type aberrometer. Laser ablation was done with a WaveLight Allegretto in a one-step procedure with ablation profiles calculated only from the individual wavefront map. Decentrations were determined from corneal topography. RESULTS: Three months after surgery, patient WM and patient SU had gained uncorrected and best spectacle-corrected visual acuity. The root mean square-wavefront error decreased up to 61% and 33%, respectively, for total and higher order aberrations (Zernike modes of 3rd order and higher). There was significant enlargement of the optical zone determined by corneal topography, and both patients no longer reported diplopia and halos at 3 months postoperatively. The optical aberration of the third patient (RE), after a 5.00-D overcorrection with a 2-mm decentration, was too high for aberration-sensing; retinal images obtained from the wavefront device were too smeared and not of sufficient contrast. In addition, this patient had a residual corneal thickness of 416 microm and thus wavefront-guided LASIK was not done. CONCLUSIONS: Wavefront-guided LASIK offers a new way of managing grossly decentered laser ablations. Unfortunately, there are still patients who have aberrations too large for wavefront sensing or with other clinical limitations such as a residual corneal thickness too thin for further treatment.

Adult↗

PubMedDate not supplied

First clinical results with the femtosecond neodynium-glass laser in refractive surgery.

PURPOSE: We evaluated four femtosecond laser intrastromal cutting procedures: creation of a corneal flap for laser in situ keratomileusis (LASIK), tunnel and entry cut for intracorneal ring, corneal flap and removable lens for keratomileusis, and intrastromal ablation for myopia and hyperopia. METHODS: A clinical trial using a femtosecond surgical laser (IntraLase Corporation) was performed in partially sighted eyes. Femto-LASIK treatment was performed on 46 eyes up to -14.00 D; 16 patients received intracorneal ring segments (Femto-ICRS); 5 patients each with one highly myopic eye had femtosecond laser keratomileusis (FLK), and 13 patients each with one myopic or hyperopic eye had intrastromal ablation (ISPRK). In Femto-LASIK, excimer laser ablation was done under the flap. In Femto-ICRS, ring segments were introduced into the laser-created channels. In femtosecond laser keratomileusis, a lens-shaped block of stroma was removed manually from under the flap. RESULTS: No difference was found between the results obtained with Femto-LASIK and a standard microkeratome. No refractive effects occurred when the created flap was not elevated. In cases of Femto-ICRS and conventional ICRS produced the same refractive results. With Femto-ICRS, no intraoperative complications occurred and visual acuity improved immediately after surgery. In femtosecond laser keratomileusis, high myopia was corrected without using excimer laser ablation; centralization of the treatment area was excellent. In intrastromal ablation, 1 to 2 hours after surgery the corneas were highly transparent; refractive results were stable. CONCLUSIONS: Femtosecond lasers can produce precise intrastromal cutting, offering significant safety and other advantages (no razor blades, corneal trauma, partial resections, or sterilization issues) over current techniques.

Adult↗

PubMedDate not supplied

Laser epithelial keratomileusis: outcome of initial cases performed by an experienced surgeon.

PURPOSE: To evaluate refractive outcome and objective clinical data, and determine efficacy, predictability, and safety of laser epithelial keratomileusis (LASEK) for myopic treatments. METHODS: We performed a retrospective non-comparative single-surgeon case series on the first 20 LASEK procedures (Alcon LADARVision 4000 laser). Mean patient age was 41.2 years (range 21 to 60 yr): 13 men and 7 women. Mean preoperative spherical equivalent refraction was -6.47+/-2.78 D. Corneal haze, uncorrected and spectacle-corrected visual acuity and manifest refraction were evaluated. RESULTS: Of 20 eyes studied, 3 were corrected for monovision. In the non-monovision group, 20/40 or better visual acuity was achieved in 94% (16 eyes) at 1 month, 100% (13 eyes) at 3 months, and 91% (10 eyes) at 6 months after LASEK; 20/20 or better was achieved in 12% (2 eyes) at 1 month, 46% (6 eyes) at 3 months, and 45% (5 eyes) at 6 months. Corneal haze at 1 month was grade 0.5 in 35% (7 eyes), 1 in 20% (4 eyes) and 2 in 10% (2 eyes). At 3 months, 62% (12 eyes) had grade 0.5 and 31% (6 eyes) had grade 1. At 6 months, 58% (12 eyes) had grade 0.5, 25% (5 eyes) had grade 1, and 8% (2 eyes) had grade 2. CONCLUSIONS: LASEK is a challenging procedure. Creating the epithelial flap is not simple and may have contributed to the high haze incidence in our study.

Adult↗