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Biomedical subjects

Ronald R Krueger

Publications and source records attributed to Ronald R Krueger.

At least 19 recordsLinked to original sources
PubMed2006

Comatic aberration as a cause of monocular diplopia.

Three patients (5 eyes) presented with complaints of monocular diplopia and no history of ocular trauma or surgery. The patients had comprehensive neuroophthalmic evaluation including manifest refraction, anterior segment and dilated fundus examination, and corneal topography. All patients also had wavefront analysis using the LADARWave system (Alcon). Two patients (4 eyes) also had hard contact lens overrefraction. The patients had a normal initial examination including corneal topography. One patient (2 eyes) did not experience resolution of diplopia with pinhole. No eye improved with manifest refraction or hard contact lens overrefraction. However, each patient had a significant amount of coma on wavefront analysis. Moreover, eyes with horizontal diplopia had horizontal coma and eyes with vertical diplopia had vertical coma as measured with the wavefront device. Higher-order optical aberrations such as coma may be associated with monocular diplopia. Wavefront technology may be useful in the workup of monocular diplopia.

Corneal Topography↗
PubMed2006

Monovision with laser vision correction.

This article reviews the advantages and disadvantages of various techniques used to achieve monovision, with an emphasis placed on monovision with laser vision correction.

Humans↗
PubMed2006

Reproducibility of wavefront measurements using the LADARWave aberrometer.

PURPOSE: To test reproducibility of lower and higher order aberration measurements using the Alcon LADAR-Wave system. METHODS: Measurements were obtained using the LADARWave aberrometer from 100 eyes (50 patients) who presented for refractive surgery. Each patient underwent 2 separate examinations a minimum of 1 day apart. Zernike polynomial values for these 2 separate measurements were recorded based on a calculated pupil size of 6.5 mm; reproducibility was assessed by analyzing the mean difference between the 2 measurements. RESULTS: The mean difference for defocus was 0.17 +/- 0.12 microm, which represented 2.6% +/- 1.9% of the mean defocus value (6.33 microm). The mean difference for astigmatism was 0.11 +/- 0.12 microm, which represented 23% +/- 26% of the mean astigmatism value (0.45 microm). The mean difference for coma was 0.06 +/- 0.06 microm, which represented 37% +/- 37% of the mean coma value (0.16 microm). The mean difference for spherical aberration was 0.04 +/- 0.04 microm, which represented 18% +/- 18% of the mean spherical aberration value (0.22 microm). CONCLUSIONS: Measurements for defocus were reproducible whereas measurements of astigmatism and higher order aberrations were more variable. The absolute root-mean-square differences between measurements were small, despite the many possible sources of error and variability. Surgical outcomes suggest that the LADARWave aberrometer is measuring at an appropriate clinical resolution.

Diagnostic Techniques, Ophthalmological↗
PubMed2005

[Corneal wound healing response following different modalities of refractive surgical procedures].

The corneal wound healing response following refractive procedures represents a subject of high relevance, due to its direct influence on the postoperative results. Technical modifications of current refractive procedures, like the automated flap creation with the femtosecond laser, LASEK, PRK with mitomycin C and Epi-LASIK have been proposed as alternatives to traditional LASIK and PRK. Several theoretical advantages have encouraged the diffusion of these new techniques; however, a better understanding of the corneal wound healing response following these procedures is required. The present text proposes a review of the corneal wound healing characteristics following different modalities of refractive surgical procedures.

Corneal Surgery, Laser↗
PubMed2005

First safety study of femtosecond laser photodisruption in animal lenses: tissue morphology and cataractogenesis.

PURPOSE: To determine through safety studies the tissue effects and potential cataractogenesis of laser modification of the crystalline lens (photophaco modulation). SETTING: Laser Zentrum Hannover, Hannover, Germany. METHODS: Six fresh porcine lenses and 6 living rabbit eyes (with the contralateral eye as a control) were radiated with a low-energy femtosecond laser to induce lens fiber disruption. After 3 months, the rabbit eyes were extracted and tested for light scatter and lens function and fixed for histology and ultrastructure. RESULTS: After laser treatment, all lenses displayed a tightly packed array of intralenticular bubbles, which resolved with time. In the porcine eyes, the bubbles coalesced unless spacing of 9 mum or greater was applied at an energy of 2 microJ. In the rabbit eyes, an energy of 1 microJ and spacing of 10 microm was chosen for transcorneal delivery, showing minimum bubble coalescence. After 3 months, the rabbit lenses showed good transparency, with only 1 rabbit having cataract formation unrelated to the laser. Laser scanning studies show essentially identical values for the back focal length and sharpness of focus (variability of back focal length). Ultrastructurally, the rabbit eyes showed a 0.5 microm electron dense border layer with adjacent normal lens architecture. CONCLUSIONS: Femtosecond laser photodisruption of the ocular lens yields a self-limited lesion with bubbles that resolve with time. In living animal eyes, no cataract formation was found with no loss of lens function or induced light scatter after 3 months. These results suggest that use of a low-energy femtosecond laser might be safe when modifying the lens for presbyopia correction.

Animals↗
PubMed2004

Thygeson's superficial punctate keratitis recurrence after laser in situ keratomileusis.

PURPOSE: To report a case of recurrent Thygeson's superficial punctate keratitis (SPK) in a patient submitted to photorefractive keratectomy (PRK) in one eye and laser in situ keratomileusis (LASIK) in the fellow eye. DESIGN: Observational case report. METHODS: A 32-year-old woman was diagnosed with Thygeson's SPK 5 years before undergoing PRK on the right eye and LASIK on the left eye to correct -3.00 + 1.50 x 20 and -3.75 sph, respectively. RESULTS: The patient presented with recurrence of Thygeson's SPK in the left eye 10 months after the LASIK procedure and no recurrence on the right eye, which was treated with PRK. CONCLUSIONS: This case report suggests that PRK may be a better option than LASIK in patients with ocular history of Thygeson's SPK. However, no strong conclusion can be established until further studies confirm the hypothesis of a lower recurrence rate of Thygeson's SPK following PRK compared with LASIK.

Adult↗
PubMed2004

Correlation of aberrations with visual acuity and symptoms.

Standard refractive surgery (photorefractive keratectomy and laser in situ keratomileusis)induces optical changes in the wavefront aberrations of the eye. Higher-order optical changes are induced, especially spherical aberration and coma. Wavefront sensing performed after refractive surgery has revealed a decrease in low-contrast acuity and contrast sensitivity, comprising the patient's night vision and leading to symptoms such as halos, starburst, and glare.

Adult↗
PubMed2004

The required technology for customized corneal ablation.

The introduction of wavefront sensing technology and customized corneal ablation has revolutionized the field of refractive surgery. Yet, in order for customized laser vision correction to reach its full potential, a number of technological requirements must be addressed by the specific laser vision correction platform offering this customized procedure. At present,several different technology platforms exist. A more thorough understanding of these platforms will help in evaluating which system is best at eliminating aberrations. The following technology is required to provide what is considered optimal within the current state of knowledge in this field: (1) scanning spot laser delivery, (2) robust eye tracking,(3) an accurate wavefront device, and (4) the wavefront-laser interface.

Cornea↗
PubMed2004

Wavefront analysis in post-LASIK eyes and its correlation with visual symptoms, refraction, and topography.

PURPOSE: To evaluate the information assessed with the LADARWave wavefront measurement device and correlate it with visual symptoms, refraction, and corneal topography in previously LASIK-treated eyes. PARTICIPANTS: One hundred five eyes (58 patients) of individuals who underwent LASIK surgery were evaluated. DESIGN: Retrospective, noncomparative case series. MAIN OUTCOME MEASURES: Complete ophthalmologic examination, corneal topography, and wavefront measurements were performed. Correlations were made between the examinations and symptoms. METHODS: Wavefront measurements were assessed with the LADARWave device. Manifest, cycloplegic refraction, and topographic data were compared with wavefront refraction and higher order aberrations. Visual symptoms were correlated to higher order aberrations in 3 different pupil sizes (5-mm, 7-mm, and scotopic pupil size). Pearson's correlation coefficient and generalized estimating equations were used for statistical analysis. RESULTS: In post-LASIK eyes, wavefront refraction components were poorly correlated to manifest and cycloplegic components. The comparison between manifest, cycloplegic, and wavefront refraction with total amount of higher order aberrations showed no strong correlation. The comparison between topography and manifest, cycloplegic, and wavefront refraction did not show strong correlation. Visual symptoms analysis showed correlation of double vision with total coma and with horizontal coma for the 5-mm and 7-mm pupil size; correlation between starburst and total coma for the 7-mm pupil size; and correlation of double vision with horizontal coma, glare with spherical aberrations and with total aberrations, and starburst with spherical aberrations for the scotopic pupil size. Scotopic pupil size had a positive association with starburst and a negative association with double vision. CONCLUSIONS: The LADARWave wavefront measurement device is a valuable diagnostic tool in measuring refractive error with ocular aberrations in post-LASIK eyes. A strong correlation between visual symptoms and ocular aberrations, such as monocular diplopia with coma and starburst and glare with spherical aberration, suggest this device is valuable in diagnosing symptomatic LASIK-induced aberrations. Horizontal coma was correlated with double vision, whereas vertical coma was not.

Adult↗
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

Comparison of flap thickness reproducibility using microkeratomes with a second motor for advancement.

PURPOSE: To compare flap thickness and reproducibility of four different types of microkeratomes during LASIK. DESIGN: Retrospective, nonrandomized, comparative case series. PARTICIPANTS: Four hundred ninety consecutive eyes underwent LASIK and were evaluated by measuring the central flap thickness by subtractive pachymetry. METHODS: All flaps were created using the Bausch & Lomb (Miami, FL) Hansatome 180 head, the Alcon (Fort Worth, TX) Summit Krumeich Barraquer Microkeratome 160 head, the Moria (Antony, France) Carriazo Barraquer (CB) 130 head, or the Moria M2 110 head. RESULTS: The flap thickness measurements differed according to the microkeratome used and were 131+/-28 microm in 41 eyes (8.4%) with the Bausch & Lomb Hansatome 180 head, 162+/-21 microm in 127 eyes (25.9%) with the Alcon Summit Krumeich Barraquer Microkeratome (SKBM) 160 head, 157+/-40 microm in 65 eyes (13.3%) with the Moria CB 130 head, and 134+/-23 microm in 257 eyes (52.4%) with the Moria M2 110 head. The central flap thickness with the SKBM and Moria M2 was statistically significantly more reproducible than with the Moria CB (P< 0.0005). There is no correlation between flap thickness reproducibility and age, corneal thickness, or corneal keratometric values. However, considering all the microkeratomes, female gender had statistically significantly more variability than male gender (P<0.02). CONCLUSIONS: Based on these results, the greatest predictability of flap thickness was seen with the SKBM and Moria M2 microkeratomes, which both use a second motor for advancement. The greatest variability, noted with the Moria CB, was likely due to the manual translation feature and places further importance on the safety of the second motor and automation when performing LASIK.

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↗
PubMedDate not supplied

Intraoperative wavefront monitoring during laser thermal keratoplasty.

PURPOSE: Low energy laser thermal keratoplasty (LTK) is being proposed as an alternative to conventional holmium LTK in an effort to minimize corneal tissue necrosis, regression, and induced astigmatism. Real-time wavefront monitoring during surgery is also being proposed as a method for regulating induced aberrations and the treatment end point. We evaluated the feasibility of intraoperative wavefront monitoring during low energy LTK. METHODS: An investigational prototype system combining a Sunrise Hyperion laser with a Shack-Hartmann wavefront sensor (Wavefront Sciences COAS) was used to treat 20 hyperopic eyes with a low energy application of eight spots of 18mJ/shot (144mJ/pulse) at 5 Hz in two rings of 6 mm and 7-mm diameter, while monitoring the treatment with real-time dynamic wavefront sensing up to 10 captures/second of 4th order Zernike data. RESULTS: The integrated wavefront-monitored LTK unit showed good stability in measuring dynamic intraoperative wavefront refractions before, during, and after the low energy LTK treatment. The readings did not interfere with the application of holmium laser pulses, nor did the LTK treatment distort the captured wavefront readings. A steady improvement of the wavefront-derived spherical equivalent refraction followed the laser treatment pattern, with a mean attempted spherical equivalent refractive change of 1.66 D and mean achieved change of 1.71 D. CONCLUSION: Intraoperative wavefront monitoring was feasible during low energy LTK. With future adaptation, it might be possible to dynamically relay the captured wavefront information to the laser during ongoing treatment, to intraoperatively control the surgical endpoint for multiple aberration terms.

Cornea↗