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Biomedical subjects

Roger F Steinert

Publications and source records attributed to Roger F Steinert.

10 recordsLinked to original sources
PubMed2006

Ultrasonic-generated fluid velocity with Sovereign WhiteStar micropulse and continuous phacoemulsification.

PURPOSE: To evaluate and compare ultrasonic turbulence created by conventional and micropulse ultrasound technology. SETTING: Sonora Medical Systems, Longmont, Colorado, USA. METHODS: A high-resolution digital ultrasound probe imaged the zone around a phacoemulsification tip. Doppler analysis allowed determination of flow. The fluid velocity was measured at 4 levels of ultrasound power at a constant flow, comparing the ultrasonic conditions of continuous energy to WhiteStar micropulses. RESULTS: In addition to the normal baseline irrigation and aspiration, fluid movement was detected directly below the phaco tip, produced by a nonlinear effect known as acoustic streaming. Acoustic streaming increased with increased phacoemulsification power for both conditions. At each of the 4 levels of power, fluid velocity away from the tip was less with micropulse technology than with continuous phacoemulsification. CONCLUSIONS: The demonstrated decrease in acoustic streaming flow away from the phaco tip with Sovereign WhiteStar micropulse technology compared to conventional ultrasound provides an objective explanation for clinical observations of increased stability of nuclear fragments at the tip and less turbulence in the anterior chamber during phacoemulsification. This methodology can be used to examine and compare fluid flow and turbulence under a variety of clinically relevant conditions.

Acetates↗
PubMed2005

ASCRS Binkhorst lecture 2004: the search for perfect vision: ophthalmology's Holy Grail?

Wavefront technology and wavefront-based vision correction are major advances but will not, in isolation, achieve the goal of perfect vision. Study of the animal kingdom teaches lessons of adaptation, leading to the conclusion that the human visual system is probably optimized for our ancestral hunter-gatherers, but today's visual demands have developed faster than the pace of evolution. Psychophysical studies of perception emphasize the importance of the visual processing system in the totality of visual function, with application today in areas such as multifocal intraocular lenses. The goal of "perfect vision" is more than optimized optics. A better understanding of visual function can be achieved only by a cooperative effort of ophthalmologists, vision scientists, and psychophysicists.

Animals↗
PubMed2004

Results of phototherapeutic keratectomy in the management of flap striae after LASIK.

OBJECTIVE: To evaluate the efficacy of phototherapeutic keratectomy (PTK) in reducing or resolving visually significant surface irregularities resulting from flap striae after LASIK. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Twenty-three eyes of 22 patients with flap striae after LASIK and reduced best-corrected visual acuity or visual symptoms that resolved with diagnostic contact lens fitting treated between January 2001 and April 2002 with at least 1 month of follow-up. The mean follow-up interval was 134 days (range, 30-354 days). INTERVENTION: Transepithelial PTK. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), resolution or reduction of preoperative symptoms, corneal haze, and best spectacle-corrected visual acuity (BSCVA). RESULTS: Mean BSCVA and UCVA improved significantly from 20/32 and 20/48 to 20/22 and 20/33 (P<0.0001 and P = 0.027), respectively, after PTK. There was a significant mean hyperopic shift of 0.88 diopters (D; P = 0.002, range, -1.38 to +3.88 D). Fourteen eyes (61%) were clinically clear, 6 eyes (23%) had trace haze, and 3 eyes (16%) had 1+ haze at the last follow-up visit. Mean spherical equivalent refractive error before LASIK was -7.23 D (range, -2.88 to -13.55 D). Twenty-two of 23 eyes had significant qualitative resolution or reduction of preoperative visual symptoms. CONCLUSIONS: In cases of visually significant LASIK flap striae, PTK is effective in improving best-corrected visual acuity and reducing visual symptoms. High myopia may be a risk factor for development of visually significant microstriae. Development of anterior stromal haze did not exceed 1+ density and was not correlated to either the number of laser pulses or the length of the follow-up period.

Adult↗
PubMed2002

Rotational malposition during laser in situ keratomileusis.

PURPOSE: To investigate the degree of rotational malposition in eyes undergoing laser in situ keratomileusis. DESIGN: Prospective observational study. METHODS: We measured the rotational position of 240 eyes of 169 patients who underwent treatment for myopic or hyperopic astigmatism with the Alcon Summit Autonomous (Orlando, Florida) LADARVision excimer laser. Immediately preoperatively, each eye was marked while the patient was seated upright. Rotational position was measured on the supine patient immediately before beginning the laser exposure. RESULTS: For all 240 eyes, mean +/- standard deviation (SD) torsional misalignment was 4.1 +/- 3.7 degrees (right eye 3.8 +/- 3.7 degrees, left eye 4.2 +/- 3.6 degrees). A total of 20 eyes (8%) had a deviation of greater than 10 degrees. CONCLUSIONS: A 4 degree and 10 degree misalignment would theoretically result in a 14% and 35% undercorrection of astigmatism, respectively. Preoperative marking of the upright patient and subsequent rotational alignment of the supine patient before laser treatment may reduce the error in correction of astigmatism during excimer laser vision correction surgery.

Astigmatism↗
PubMed2002

Topographic analysis of corneal regularity after penetrating keratoplasty.

PURPOSE: To evaluate the accuracy of the Holladay Diagnostic Summary of the EyeSys Corneal Analysis System in predicting the corneal visual acuity potential in patients who have undergone penetrating keratoplasty (PKP). METHODS: Astigmatism patterns, refractive and topographic astigmatism, best spectacle-corrected visual acuity (BSCVA), and hard contact lens (HCL) visual acuity of 54 patients were analyzed 3 months after PKP and compared with the Potential Corneal Acuity (PCA) value predicted by the Holladay Diagnostic Summary. RESULTS: Qualitative patterns of astigmatism (p = 0.01) and refractive (p = 0.002) and topographic (p = 0.0002) astigmatism were significantly correlated with PCA values. Using HCL visual acuities to correct the BSCVA (HCL-corrected BSCVA) for noncorneal causes of reduced vision, we found that the PCA values of 48.1% of the patients were within one line of the HCL-corrected BSCVA; 81.5% were within two lines; and 93.0% were within three lines. CONCLUSION: The Holladay PCA measurement may be useful in the postoperative evaluation of the optical quality of the central corneal surface in patients who have undergone PKP.

Adult↗
PubMedDate not supplied

The effects of automated registration on aberration measurement with the LADARWave aberrometer.

PURPOSE: To evaluate the effects of automating the registration process for wavefront measurement using the LADARWave aberrometer. Measures of interest include accuracy, repeatability, and speed of measurement. METHODS: Five separate registration images were collected for each of eight eyes of four individuals with varying iris color using the LADARWave aberrometer. Technicians manually aligned the images and the autoregistration feature was used to align the same images. Time, accuracy, and repeatability of the alignment were measured using objective techniques. The potential effect on positional error was evaluated using a retrospective reprocessing of LADARWave data from an existing sample dataset. RESULTS: Autoregistration was the fastest method of alignment, from five to seven times faster than manual registration. It was also the most consistent, with the lowest pupil/limbus offset error (45 microm). Technicians averaged 48 to 91 microm. The differences in wavefronts used to generate the composite wavefront image for surgery export were 18% lower with autoregistration. CONCLUSIONS: The autoregistration feature of the LADARWave aberrometer not only removes inter-technician variability, but reduces the time to perform image alignments and improves the consistency of the alignments. This helps reduce errors related to wavefront position, potentially improving outcomes.

Cornea↗