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Biomedical subjects

R L Lindstrom

Publications and source records attributed to R L Lindstrom.

At least 19 recordsLinked to original sources
PubMed1997

Laser In Situ keratomileusis (LASIK) for the treatment of low moderate, and high myopia.

PURPOSE: To evaluate the efficacy, safety and predictability of LASIK in the treatment of low, moderate and high myopia. METHODS: A perspective study of LASIK for low myopia of -0.75 to -6.00 with less than +1 D of astigmatism and for moderate and high myopia of -6.12 to -20 D with astigmatism up to +4.50 D was performed at our institution from March through November, 1996. The Chiron automated corneal shaper was used for the initial flap, and either the Summit or VISX laser was used for the refractive ablation. Preoperative refraction, uncorrected and corrected visual acuity were compared to postoperative refraction, uncorrected and corrected visual acuity. One day and 1 month results were available on all patients. RESULTS: In the low myopia group 101 eyes underwent LASIK with a mean preoperative spherical equivalent of -4.16 +/- 1.41 D (-0.75 D to -6.00 D). Mean preoperative astigmatism was +0.4 +/- 1.29 D (0 to 0.75 D). At 1 day, 48% were 20/25 or better and 80% were 20/40 or better. The day 1 mean spherical equivalent was +0.4 +/- 0.75 D with 86% between +/- 1.00 D of emmetropia. At 1 month, 50% were 20/25 or better and 90% were 20/40 or better. The 1 month mean spherical equivalent was -0.26 +/- 0.65 D with 89% between +/- 1.00 D of emmetropia. In the high myopia group 198 eyes underwent LASIK with a preoperative mean spherical equivalent of -8.34 +/- 2.15 D)-6 to -20D) and a mean preoperative astigmatism of +1.18 +/- 0.88 D (0 to +4.5 D). At 1 day postoperatively, 17% were 20/25 or better, and 61% were 20/40 or better. The mean day one spherical equivalent was -0.26 +/- 1.56 D with 58% between +/- 1.00 D of emmetropia. At 1 month, 35% were 20/25 or better and 71% were 20/40 or better. The 1 month mean spherical equivalent was -0.28 +/- 1.18 with 63% within +/- 1.00 D of emmetropia. CONCLUSION: Early results of using LASIK to treat low, moderate and high degrees of myopia with and without astigmatism appear promising, although longer follow-up and nomogram refinement are needed.

Adult↗
PubMed1996

Corneoscleral melt after pterygium surgery using a single intraoperative application of mitomycin-C.

A 59-year-old man underwent pterygium excision with intraoperative application of 0.2 mg/ml (0.02%) mitomycin-C placed on the scleral bed for 3 min. A sliding conjunctival flap was used to cover the exposed limbus and sclera. Five weeks after the original surgery, the patient had mild trauma and noted decreased vision. At that time, it was noted that he had a corneoscleral melt with perforation. The patient was managed with a lamellar transplant in this area. Intraoperative single-dose application of topical mitomycin-C can be associated with serious complications. This case occurred despite the fact that this patient received the lowest dose used in a series of 25 eyes using the same technique without any other complications. Although topical mitomycin-C is effective as an adjunct to pterygium surgery and may reduce recurrence, the safety and efficacy of various concentrations and dosing schedules need further definition.

Chemotherapy, Adjuvant↗
PubMed1995

Minimally invasive radial keratotomy: mini-RK.

Radial keratotomy (RK) is a common surgical technique for correcting myopia. The RK incisions, like any corneal incisions, permanently weaken the cornea and this structural weakening can cause several complications and side effects, including diurnal fluctuation, progressive hyperopic shift, and the potential for traumatic rupture of the keratotomy scars. I describe a new technique--minimally invasive RK (mini-RK)--that reduces the millimeters of cornea incised and present preliminary laboratory and clinical results. In a cadaver eye study, eight short, deep incisions extending from the 3.0 mm optical zone to the 7.0 mm optical zone produced 92% of the efficacy of full-length incisions to the 11.0 mm optical zone. This finding was confirmed by intraoperative surgical keratometry in six patients in whom a 1% increase in central corneal flattening was achieved when incisions were extended from the mini-RK configurations to full length. In a retrospective evaluation of 100 patients with -1.0 to -6.0 diopters (D) of myopia, 92% of eyes were within 1.0 D of emmetropia and 94% had 20/40 or better uncorrected visual acuity. No significant complications were encountered. Mini-RK may be a useful alternative to reduce the invasiveness of RK but retain its efficacy in eyes with low to moderate myopia.

Adult↗
PubMed1994

Results one year after using the 193-nm excimer laser for photorefractive keratectomy in mild to moderate myopia.

As part of a clinical trial, photorefractive keratectomy using the VISX 2015 193-nm excimer laser was performed on 91 healthy eyes of 91 patients. Preoperative refractive errors (spherical equivalent) ranged from -1.00 to -7.50 diopters (mean, -4.16 +/- 1.41 diopters). No patient had more than 1 diopter of refractive astigmatism. Six months postoperatively, the average residual refractive error was +0.09 +/- 0.63 diopters (range, -2.13 to +1.63 diopters). Correction within 1 diopter of that attempted was attained in 85 eyes (93%). Uncorrected visual acuity of 20/40 or better was attained in 86 eyes (95%) and was 20/25 or better in 67 eyes (74%). At one year, follow-up information was available on 85 eyes of 85 patients. The average residual refractive error was -0.15 +/- 0.65 diopters (range, -2.50 to +1.63 diopters). Correction within 1 diopter of that attempted was attained in 85 eyes (93%). Uncorrected visual acuity was 20/40 or better in 83 eyes (98%) and was 20/25 or better in 68 eyes (80%). One patient lost three lines of best-corrected visual acuity because of corneal haze, dropping from 20/15 to 20/30, whereas all other patients returned to best-corrected visual acuity within one line of their preoperative best-corrected visual acuity. Photorefractive keratectomy with the 193-nm excimer laser appears to be a useful treatment modality for the reduction of mild to moderate myopia.

Adolescent↗
PubMed1994

Use of the 193 nm excimer laser for photorefractive keratectomy in low to moderate myopia.

As part of a Phase III clinical trial, photorefractive keratectomy using the VISX 2015 193 nm excimer laser was performed on 91 sighted eyes of 91 patients. Preoperative refractive errors (spherical equivalent) ranged from -1.00 diopters (D) to -7.50 D (mean -4.11 D +/- 1.43 D). At six months, average residual refractive error was 0.02 D +/- 0.64 D (range -2.21 D to +1.38 D). Ninety-three percent of eyes were within 1.00 D of attempted correction, 93% had uncorrected visual acuity of 20/40 or better, and 72% achieved uncorrected visual acuity of 20/25 or better. All patients returned to their best corrected visual acuity within one line of their preoperative best corrected visual acuity. Photorefractive keratectomy with the 193 nm excimer laser appears to be useful in reducing low to moderate myopia.

Adolescent↗
PubMed1994

Treatment of low, moderate, and high myopia with the 193-nm excimer laser.

PATIENTS AND METHODS: Photorefractive keratectomy using the VISX 2015 193-nm excimer laser was performed on 134 consecutive eyes of 97 myopic patients by the two authors. Preoperative refractive errors (spherical equivalent) ranged from -1.63 to -14.25 diopters (D) (mean, -5.76 +/- 2.40 D). Follow-up of 6 months was available on 110 eyes. At six months, the average residual refractive error was +0.16 +/- 1.13 D (range -2.88 to +3.38). Correction within 1 D of that attempted was obtained in 77 eyes (70%). Uncorrected visual acuity of 20/40 or better was achieved in 89 eyes (81%), and 20/25 or better in 54 eyes (49%). RESULTS: At one year, follow up was available on 57 eyes. The average residual refractive error was -0.22 +/- 0.87 D (range -3.00 to +2.00 D). Correction within 1 D was achieved in 47 eyes (82%). Visual acuity was 20/40 or better uncorrected in 50 eyes (88%), and 20/25 or better in 35 eyes (61%). One patient lost three lines of best corrected visual acuity and 4 patients lost 2 lines of best corrected visual acuity from corneal haze or irregular astigmatism, while all other patients returned to best corrected visual acuity within one line of their preoperative best corrected visual acuity. CONCLUSION: Photorefractive keratectomy with the 193-nm excimer laser appears to be a useful treatment modality for the reduction of low to moderate myopia.

Adult↗
PubMed1993

Assessment of the blood-aqueous barrier by fluorophotometry following poly(methyl methacrylate), silicone, and hydrogel lens implantation in rabbit eyes.

Intraocular lenses of silicone, hydrogel, or acrylic materials that can be implanted through small incisions are being proposed as an alternative to conventional poly(methyl methacrylate) lenses. The potential of each of these materials to stimulate intraocular inflammation is important in their selection as an implantable material. To investigate the potential of each material, we assessed by clinical slitlamp examination, fluorophotometry, and histopathology the inflammatory response induced in the rabbit eye following phacoemulsification and implantation of hydrogel, silicone, or poly(methyl methacrylate) intraocular lenses. All lenses seemed to be equally well tolerated. In general, the degree of inflammation seen clinically decreased over the four-month study; however, anterior segment fluorophotometry showed continued mild interruption of the blood-aqueous barrier in all lens groups. Fluorophotometry is a sensitive method to assess persistent subclinical anterior segment inflammation.

Animals↗
PubMed1993

Multifocal intraocular lenses and glare.

In a previous paper, we reported finding deficits in the contrast sensitivity functions of patients with diffractive multifocal intraocular lenses (IOL's). The results were consistent with optical measurements of the modulation transfer function (MTF) of the IOL. When this MTF is treated as a linear spatial frequency filter, it predicts the existence of a glare effect; contrast threshold for the recognition of target letters should be elevated by a bright, adjacent stimulus. We tested this prediction by measuring contrast thresholds for recognizing 0.2 degrees Sloan letters on a background luminance of 11.2 cd/m2. The letters were presented inside bright (300 cd/m2) annular rings with inner diameters ranging from 0.42 to 1.22 degrees. Thresholds were measured for seven multifocal subjects, age-matched groups of monofocal subjects and phakic-control subjects, and a young group. Multifocal subjects exhibited a greater glare effect than monofocal subjects, and they in turn exhibited a greater effect than phakic-control subjects. The observed glare effect for multifocal subjects was about twice that expected from the spatial filtering property of the multifocal IOL.

Adult↗
PubMed1993

Multifocal and bifocal implants.

Removal of cataract with intraocular lens implantation has been a well-accepted treatment for the past two decades. The development of monofocal intraocular lens technology has represented a significant advance over earlier treatments of cataract and, since the advent of widespread implantation of these lenses, most patients with cataract can achieve good postsurgical vision with the use of bifocal spectacles.

Astigmatism↗