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Biomedical subjects

R F Steinert

Publications and source records attributed to R F Steinert.

At least 37 records · Page 2Linked to original sources
PubMed1997

Radial keratotomy increases outflow facility in the porcine eye in vitro.

PURPOSE: To investigate the biomechanical effect induced by radial keratotomy on outflow facility in paired, enucleated whole porcine eyes. METHODS: Freshly enucleated porcine eyes were perfused at a constant pressure of 10 mm Hg. Radial keratotomy (RK), with a 3.5 mm central clear zone and eight radial incisions, was performed using a diamond knife with the blade length set at 100% of the paracentral corneal thickness, as measured by pachymetry. The fellow eye of each pair received sham RK as a control. RESULTS: Seven pairs of eyes were perfused (RK group n = 7, control n = 7). There was no significant difference in the mean baseline of outflow facility between the paired experimental and control eyes preoperatively (p = 0.5). After RK, outflow facility increased by 46% (p < 0.001) in the treatment group, compared to a 7% (p < 0.04) increase in the control group, resulting in a 39% increase in outflow facility attributed to RK (p < 0.001). CONCLUSIONS: Radial keratotomy produced a statistically significant acute increase in outflow facility in freshly enucleated porcine eyes. We believe that this increase results from steepening of the peripheral corneal curvature and the concomitant stretching of the iridocorneal angle. Further studies are needed to evaluate this effect in human eyes and in vivo.

Animals↗
PubMed1997

Wound healing anomalies after excimer laser photorefractive keratectomy: correlation of clinical outcomes, corneal topography, and confocal microscopy.

PURPOSE: To further the understanding of wound healing anomalies affecting visual function after myopic photorefractive keratectomy (PRK). METHOD: Analysis of a clinical database of PRK on 133 eyes with myopia of -1.5 to -7.0 D and 43 eyes with myopia of -6.0 to -12.0 D. Visual function was analyzed by subgroups of 1) no topographic anomalies; 2) topographic central islands; and 3) topographic keyhole patterns. The natural course of healing was documented over 6 months with visual acuity measurements, clinical observation, and corneal topography. In vivo clinical-pathologic correlations were made by scanning confocal microscopy. RESULTS: Topographic anomalies were identified 1 month post-PRK in 48 eyes (40.3%) with low-moderate myopia and in 14 eyes (32.5%) with moderate-high myopia. For patients with 6 month follow-up, these rates declined to 25% and 23%, respectively. At 1 month post-PRK, topographic anomalies significantly reduced uncorrected and best-corrected visual acuity and refractive predictability. By 6 months post-PRK, the small number of eyes with persistent anomalies had visual outcomes similar to patients with normal topography. A simple approach to anti-island pre-treatment reduced islands slightly and keyhole anomalies significantly (anti-island pre-treatment vs no pretreatment: islands 25% vs 31.8%; keyholes 2.3% vs 17.6%; p = 0.021) but with decreased predictability of induced refractive change at 1 month post-PRK. Confocal microscopy in vivo demonstrated prominent deposition of subepithelial extracellular material 1 to 2 months after PRK that diminished by 6 to 8 months, but persisted in the presence of central islands. Scar formation appeared to represent an elevated plaque of new collagen with active keratocytes. CONCLUSIONS: Topographic anomalies of wound healing are common after PRK. Vision and predictability are reduced by anomalies 1 month post-PRK but anomalies often resolve by 6 months. Marked improvement of vision occurs even when anomalies persist. Central islands appear to consist of persistent dense subepithelial extracellular deposits. Local scars are caused by new collagen deposition.

Adult↗
PubMed1996

Hydrogel intracorneal lenses in aphakic eyes.

BACKGROUND: The theoretical benefits of synthetic keratophakia over conventional corneal lamellar procedures are the elimination of donor concerns and superior refractive predictability. Additionally, synthetic material can be inspected for optical quality and power, and it can be sterilized. Furthermore, visual recovery should be more rapid since epithelium is not removed from the central part of the cornea and the need for keratocyte repopulation is eliminated. OBJECTIVE: To present results on patients who received an intracorneal implant (Kerato-Gel, Allergan Medical Optics, Irvine, Calif) that was made from lidofilcon A, a glucose-permeable hydrogel with an equilibrium water content of 68%. METHODS: The intracorneal implants were implanted in 35 adult patients for correction of aphakia. Inclusion criteria excluded patients with aphakia who were candidates for intraocular lenses. RESULTS: A total of 19 patients were followed up through 2 years postoperatively. For 16 patients with 2-year postoperative refractive data, the average spherical equivalent was -0.63 +/- 2.07 diopters (D). At 2 years, 88% of patients were within +/- 3.00 D of plano and 50% were within +/- 1.00 D. the mean change in Snellen's line for corrected visual acuity was -3.25 lines at 2 years for all patients and -2.0 lines for a subgroup of five patients who were free of vision-limiting preoperative disease. CONCLUSIONS: Results suggest that this intracorneal implant is well tolerated by the cornea and can provide predictable refractive results in patients with high-risk aphakia. Limitations of the procedure are uneven microkeratome resections, loss of best-corrected visual acuity, and irregular astigmatism in some patients. Although these data show good evidence of biocompatibility of the implant material, technical surgical progress is needed to advance this procedure into clinical therapeutic practice.

Adult↗
PubMed1996

Comparison of suture-in and suture-out postkeratoplasty astigmatism with single running suture or combined running and interrupted sutures.

PURPOSE: To evaluate postkeratoplasty astigmatism between two suture techniques 2 to 4 years postoperatively in a group of patients previously studied 9 months postoperatively. METHODS: Thirty-two patients who underwent penetrating keratoplasty were randomly assigned to one of two groups. Group 1 (16 patients) had a 24-bite single running 10-0 nylon suture with postoperative suture tension adjustment; group 2 (16 patients) had combined 16-bite running and eight interrupted 10-0 nylon sutures with selective postoperative removal of interrupted sutures. During long-term follow-up, the running suture was removed in 19 patients (59%). RESULTS: Postoperative astigmatism was slightly lower in patients with the single running suture technique when sutures were in place and was slightly greater after the sutures were removed compared with the combined running and interrupted suture technique (sutures in: single running suture +/- SD, 2.6 +/- 1.2 diopters [five patients, 31%]; combined running and interrupted sutures, 3.8 +/- 1.1 diopters [eight patients, 50%]; sutures out: single running suture, 3.3 +/- 1.3 diopters [11 patients, 69%]; combined running and interrupted sutures, 2.8 +/- 1.5 diopters [eight patients, 50%]). These differences were not statistically significant (sutures in, P < .13; sutures out, P < .46). Averages of follow-up were group 1,48.3 +/- 10.6 months and group 2, 46.3 +/- 13.0 months. Follow-up ranged from 23 to 60 months. CONCLUSIONS: Postoperative astigmatism 4 years after penetrating keratoplasty is similar for these two suturing techniques, with or without residual sutures. A single running suture results in more rapid visual rehabilitation and less early astigmatism compared with the combined interrupted and running suture technique.

Adult↗
PubMed1996

Enlargement of incision width during phacoemulsification and folded intraocular lens implant surgery.

PURPOSE: The authors investigated the dimensional stability of incisions during phacoemulsification and small-incision intraocular lens (IOL) implantation. METHODS: Forty-six eyes undergoing temporal clear corneal phacoemulsification and folded silicone IOL implantation were measured with an internal-incision gauge after initial keratome entry, cataract removal, and folded IOL implantation. RESULTS: The initial incision created by a diamond keratome was wider than the physical keratome width by a mean of 0.16 mm. After completion of phacoemulsification and irrigation/aspiration, the incision further widened by a mean of 0.09 mm. Both forceps insertion of a three-piece silicone IOL and injector insertion of a plate haptic silicone IOL resulted in further incision enlargement by a mean of 0.26 mm. Widening the incision before IOL insertion did not eliminate even further incision expansion during the IOL insertion. CONCLUSIONS: The phacoemulsification incision enlarges at each step of the procedure. Irreversible incision stretching or incision tearing occurs, rather than reversible elastic incision deformation. Clinical studies that assume the initial keratome size equals the final incision size may be erroneous.

Humans↗
PubMed1995

Long-term clinical results of AMO PhacoFlex model SI-18 intraocular lens implantation.

The AMO PhacoFlex Model SI-18 was the first commercially available three-piece silicone intraocular lens (IOL) for use in small incision cataract surgery. Allergan Medical Optics' silicone IOLs have been implanted in more than 750,000 patients worldwide over the past eight years. This report of the FDA clinical investigation of the AMO PhacoFlex model SI-18 IOL summarizes one year follow-up data from the initial premarket approval clinical trial on 500 core patients implanted with the SI-18 lens. One-year follow-up data from 5,860 patients in the modified core group and three-year follow-up data on the 500 patient core/modified core group are also presented. At three years postoperatively, 91.3% of best case core/modified core patients achieved 20/40 or better corrected visual acuity. Overall incidence of persistent complications at three years was 3.2%.

Aged↗
PubMed1995

Long-term results of epikeratoplasty for keratoconus.

By analysis of outpatient records at the Massachusetts Eye and Ear Infirmary, the clinical course of 10 consecutive patients who underwent epikeratoplasty for keratoconus was reviewed to determine their clinical and functional status 5 years after surgery. Eight of 10 patients (80%) had clear, intact lenticules at 12 months. During a mean follow-up of 67 months (range = 35-101 months), each maintained long-term stability of best corrected vision, refractive astigmatism, and keratometric astigmatism. The mean uncorrected visual acuity improved from 20/660 to 20/134, whereas the mean spectacle corrected acuity improved from 20/260 to 20/30. All but one patient had a spectacle acuity equal to hard contact lens acuity. However, no patients were corrected to 20/20 at the end of the follow-up period. Refractive and keratometric astigmatism stabilized by 12 months (mean = 3.62 and 3.05 D, respectively), and decreased slightly during the longer period of follow-up (mean = 2.94 and 2.17 D, respectively). Epikeratoplasty is a useful method of visual rehabilitation in highly selected cases of keratoconus in which there is no central opacity, preoperative hard contact lens acuity is worse than 20/40, the average keratometry is < 60 D, contact lens intolerance is present, and in which the patient will tolerate some degree of reduced contrast sensitivity and < 20/20 high contrast acuity.

Contrast Sensitivity↗
PubMed1994

One-year results of excimer laser photorefractive keratectomy for low to moderate myopia.

OBJECTIVE: Excimer photorefractive keratectomy is a promising method to reduce myopia. We evaluated the effectiveness, predictability, stability, and safety of photorefractive keratectomy performed by two surgeons at a single site with a 1-year follow-up. METHODS: An excimer laser (Summit Excimed UV200, Summit Technology, Waltham, Mass) was used to treat 47 eyes. Preoperative uncorrected visual acuity averaged 20/277 and ranged from 20/60 to 20/500. Spherical equivalent averaged -3.9 diopters and ranged from -1.5 to -6.1 D. RESULTS: One year postoperatively, best corrected visual acuity averaged 20/13 and ranged from 20/10 to 20/20. No patients lost any of best corrected visual acuity. The uncorrected visual acuity at 1 year averaged 20/20 and ranged from 20/10 to 20/200. Ninety-four percent of eyes had an uncorrected visual acuity of 20/40 or better; 83%, 20/25 or better; and 74%, 20/20 or better. An initial hyperopic overcorrection is followed by gradual regression to emmetropia during a 12-month period. Refractive spherical equivalent averaged 0.44 D and ranged from -3 to +2.6 D at 1 year. The proportion of eyes within 1 D of emmetropia was 80% at 1 year. The most significant shifts in refraction occurred between the first and second months, but small shifts occurred up to 12 months. Subgrouping the results according to age revealed a significantly greater effect with larger residual hyperopia in those older than 40 years. Patient satisfaction with the procedure was high. CONCLUSION: During a 1-year period, excimer photorefractive keratectomy appears to be an effective, predictable, stable, and safe method to reduce myopia. Age may play a role in the effectiveness of the procedure, with greater hyperopia resulting in those older than 40 years.

Adult↗
PubMed1994

Effect of folding instruments on silicone intraocular lenses.

The Faulkner holding and folding forceps, the Fine folder, and the Prodigy inserter (PRO-1A) were evaluated to assess their effects on silicone intraocular lenses (IOLS) after the lenses were folded. The IOLs were evaluated before folding and at two and 24 hours after folding for haptic dimension, optic quality, and surface quality. None of the instruments caused a clinically important effect on the IOLs 24 hours after folding. The cross-sectional area required for IOL insertion was calculated for each folder. The Prodigy required the smallest cross-sectional area and the Faulkner the largest when folding a 24 diopter lens. We also describe a protocol that can be used to evaluate new IOL folders.

Cataract Extraction↗
PubMed1994

Electron microscopic findings in a cornea with recurrence of herpes simplex keratitis after excimer laser phototherapeutic keratectomy.

Excimer laser phototherapeutic keratectomy is emerging as an alternative therapy to corneal transplantation for the treatment of multiple corneal diseases. We report three cases of recurrence of herpes simplex keratitis after treatment of herpetic corneal scars with the excimer laser. In two cases, the patients underwent subsequent corneal transplantation. One corneal button examined with transmission electron microscopy (TEM) demonstrated a well-differentiated epithelium over the area of ablation, a linear, continuous basal lamina, and no viral particles. Anterior stromal scarring may have resulted from the laser treatment itself or may represent incomplete ablation of previous scars. Whether reactivation of the virus was stimulated by the laser or occurred as part of the natural history of the disease is uncertain. We recommend that patients who undergo excimer laser treatment for herpes simplex scarring receive careful follow-up including antiviral coverage.

Adult↗
PubMed1993

Postkeratoplasty astigmatism with single running suture or interrupted sutures.

In a prospective randomized clinical trial we compared astigmatism after penetrating keratoplasty with two different suture techniques between two groups of patients (38 patients). The first group (18 patients) had a 24-bite single running 10-0 nylon suture (single running suture) with postoperative suture adjustment to decrease astigmatism. The second group (20 patients) had a combination of a 16-bite running 10-0 nylon suture and eight interrupted 10-0 nylon sutures (combined running and interrupted sutures) with selective postoperative removal of interrupted sutures to decrease astigmatism. The single running suture resulted in a lower postoperative astigmatism than a combined running and interrupted suture technique (single running suture, 2.7 +/- 2.2 diopters; combined running and interrupted sutures, 3.9 +/- 2.5 diopters; P < .02). Average length of follow-up was similar in both groups (single running suture, 9.0 +/- 2.2 months and combined running and interrupted sutures, 8.4 +/- 2.2 months). Minimal length of follow-up was six months in both groups. No running sutures were broken. The adjustable single running suture technique provided greater control of astigmatism after penetrating keratoplasty than a technique using a combination of a 16-bite running suture and eight interrupted sutures.

Adult↗
PubMed1993

Intrinsic stability of 'self-sealing' unsutured cataract wounds.

Many operative and postoperative factors can influence cataract wound stability and postoperative astigmatism. The final outcome is fundamentally dependent on the intrinsic biomechanical stability of the corneal dome in the presence of the wound. We determined the stability of the central and peripheral cornea with computer-assisted topographic analysis of six freshly enucleated human globes. Self-sealing, unsutured, scleral tunnel wounds 4.0 mm in length were dissected, with widths varying from 1.4 to 6.0 mm. Intraocular pressure was elevated in 5-mm increments from 15 to 40 mm Hg without measurable topographic change in the visual axis or superior cornea. We conclude that these long scleral tunnel wounds do not necessarily destabilize the cornea within the usual range of intraocular pressure. Postoperative-induced astigmatism is therefore due to other operative and postoperative factors. Some of these factors may be identifiable with this model and controlled or eliminated.

Astigmatism↗
PubMed1993

A randomized trial of intraocular lens fixation techniques with penetrating keratoplasty.

PURPOSE: Pseudophakic corneal edema is the principal indication for penetrating keratoplasty in the United States. Currently, three techniques of intraocular lens (IOL) fixation during penetrating keratoplasty for this condition are commonly used--flexible anterior chamber IOL (AC IOL) implantation, iris suture fixation of a posterior chamber IOL (PC IOL), and transscleral suture fixation of a PC IOL. This study represents the first prospective, randomized comparison of these three techniques. METHODS: One hundred seventy-six consecutive patients with pseudophakic corneal edema who underwent penetrating keratoplasty with IOL exchange were randomized to one of the three implantation techniques. Standardized evaluations were performed at baseline and at 6, 12, and 18 months postoperatively. Life-table analysis provided cumulative risk estimates for specific complications. RESULTS: Randomization produced comparable groups at baseline. The cumulative risk of macular edema was significantly less for the iris fixation cohort than for either the AC IOL or scleral fixation group. A complications index was constructed based on the major adverse outcomes of glaucoma escalation, cystoid macular edema, IOL dislocation, and graft failure. A significantly lower risk of complication was found for iris compared with scleral fixation of PC IOLs. CONCLUSION: The authors conclude that transscleral fixation of the PC IOL at the time of penetrating keratoplasty for pseudophakic corneal edema is associated with a greater risk of adverse outcome than iris fixation of a PC IOL.

Aged↗
PubMed1992

A prospective, randomized, double-masked comparison of a zonal-progressive multifocal intraocular lens and a monofocal intraocular lens.

INTRODUCTION: Multifocal intraocular lenses (IOLs) have been designed to provide improved near visual acuity without spectacles compared with monofocal IOLs. Early studies have reported variables amounts of decreased visual acuity and contrast sensitivity with multifocal IOLs, and some patients have experienced halos and glare. METHODS: The authors performed a prospective, double-masked, multicenter evaluation of 62 patients randomized between a new zonal-progressive optic multifocal IOL and a monofocal IOL. RESULTS: Mean postoperative spherical equivalent, astigmatism, and uncorrected and best-corrected distance visual acuity were similar between the two groups. Patients with a multifocal IOL achieved significantly better uncorrected near visual acuity than patients with monofocal IOLs (J3+ versus J7; P less than 0.0001). With distance correction only, mean near visual acuity was J2 versus J5- (P = 0.0001). Best-corrected near visual acuity was J1 for both groups, with 1.36 diopters (D) for the multifocal group versus 2.37 D for the monofocal group (P less than 0.0001). Regan contrast sensitivity was lower for the multifocal patients at all contrast levels, and achieved statistical significance at very low contrast (11% contrast; P = 0.0024). Fifty-two percent of patients with a multifocal IOL reported that they did not need spectacles at all or used them only for their fellow eye, compared with 25% of the patients with monofocal IOLs. CONCLUSION: Both monofocal and multifocal implant patients were very satisfied with the results of their cataract extraction and IOL implant surgery. A small loss of contrast sensitivity with the multifocal IOL was demonstrated, consistent with theoretical predictions. The functional significance of the loss of contrast sensitivity appears to be small and counterbalanced by the advantage of improved uncorrected near visual acuity.

Aged↗
PubMed1991

Cystoid macular edema, retinal detachment, and glaucoma after Nd:YAG laser posterior capsulotomy.

A series of 897 Nd:YAG laser posterior capsulotomies were reviewed for the complications of cystoid macular edema, retinal detachment, new onset of glaucoma, and worsened preexisting glaucoma. After Nd:YAG capsulotomy, 11 patients (1.23%; 95% confidence interval, 0.51% to 1.95%) developed cystoid macular edema and eight patients (0.89%; 95% confidence interval, 0.28% to 1.5%) developed a retinal detachment. The new onset of glaucoma was observed in seven patients (0.78%; 95% confidence interval, 0.20% to 1.36%). Five patients (0.56%; 95% confidence interval, 0.07% to 1.05%) with preexisting glaucoma had persistent worsening of their glaucoma. Most patients with a complication had no identifiable risk factors in common. The numbers of laser pulses and energy delivered were not risk factors. Retinal detachment and cystoid macular edema developed most often many months after capsulotomy and many months to years after the cataract surgery. Patients undergoing Nd:YAG laser capsulotomy therefore require ongoing medical observation to detect and treat these serious complications.

Cataract Extraction↗