Biomedical subjects
Publications and source records attributed to R L Lindstrom.
The various types of posterior chamber intraocular lens malpositions, in increasing degrees of severity, are described. These include pupillary capture, optic decentration, malpositioned loop, windshield wiper, sunrise, sunset and lost lens syndromes. The etiologies, management, and prevention of these complications are discussed.
We placed human donor corneas in M-K medium at 4 degrees C for 24 hours, cultured them in minimal essential medium at 34 degrees C for two to five weeks, and then either (1) placed the corneas in M-K medium at 4 degrees C for 48 hours before transplantation (Group 1, 47 eyes); (2) placed the corneas in M-K medium at 4 degrees C for 16 hours before transplantation (Group 2, 17 eyes); or (3) transplanted the corneas without postculture cooling to 4 degrees C (Group 3, 11 eyes). We compared the corneas preserved by organ culture with an equal number of corneas transplanted during the same period, but preserved only in M-K medium at 4 degrees C for one to four days. The central endothelial cell losses noted two months after keratoplasty were significantly greater in the organ-cultured corneas than in the M-K-preserved corneas in each of the three groups. The mean endothelial cell loss in the 11 organ-cultured corneas in Group 3 was significantly less than that in the 64 organ-cultured corneas in Groups 1 and 2. The corneas in Group 1 were also examined one year after keratoplasty, and the cell losses in the organ-cultured grafts remained significantly greater than those in the M-K-preserved grafts.(ABSTRACT TRUNCATED AT 250 WORDS)
The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center, self-controlled clinical trial of a standardized technique of radial keratotomy in 435 patients who had physiologic myopia with a preoperative refraction between -2.00 and -8.00 diopters. The surgical technique consisted of eight incisions using a diamond micrometer knife with blade length determined by intraoperative ultrasonic pachymetry and the diameter of central clear zone determined by preoperative refraction. At one year after surgery, myopia was reduced in all eyes; 60% were within +/- 1.00 diopter of emmetropia; 30% were undercorrected and 10% were overcorrected by more than 1.00 diopter (range of refraction, -4.25 to +3.38 D). Uncorrected visual acuity was 20/40 or better in 78% of eyes. The operation was most effective in eyes with a refraction between -2.00 and -4.25 diopters. Thirteen percent of patients lost one or two Snellen lines of best corrected visual acuity. However, all but three eyes could be corrected to 20/20. Ten percent of patients increased astigmatism more than 1.00 diopter. Disabling glare was not detected with a clinical glare tester, but three patients reduced their driving at night because of glare. Between six months and one year, the refraction changed by greater than 0.50 diopters in 19% of eyes.
Corneal epithelial opacities similar to those seen in corneal epithelial basement membrane dystrophy were seen in 33 of 71 eyes following radial keratotomy. These changes were clinically indistinguishable from those seen in map-fingerprint-dot dystrophy with map type changes seen most often. Basement membrane changes tended to be transient (persisting less than 3 months in 75.3% of eyes) and not usually visually significant. However, three eyes had changes which persisted for 12 months. Most eyes with basement membrane changes had involvement of less than one-half quadrant of the corneal (68%). Involvement of two or more quadrants occurred in 9.4% of eyes with these changes. One eye had visually significant changes which persisted for 3 months. There were no episodes of recurrent erosion.
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We have documented diffuse, superficial, transverse fissures of blue polypropylene IOL loops that had been exposed to a prolonged inflammatory reaction. The cause and clinical significance of this process has not yet been determined. The polymethylmethacrylate optic showed no similar changes.
Seventeen patients with high astigmatism ranging from 5.63 to 19.50 diopters after penetrating keratoplasty had further surgery performed to reduce the astigmatism. Twelve patients had a mean reduction of 4.70 diopters ranging from 1.75 to 10.50 diopters. Four patients had a mean increase of 4.81 diopters with a range from 2.13 to 9.00 diopters. We have found that large amounts of astigmatism can be corrected with relaxing incisions within or circumferential to the graft-host interface but the predictability of the surgical outcome is not satisfactory in all cases.
Paired human donor corneas were studied to determine the effects of temperature, osmolarity, and media shifts on the endothelium of corneas stored in McCarey-Kaufman (MK) medium initially and then shifted to standard organ culture medium. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated intact corneal endothelium in six of seven human control corneas stored in MK medium prior to fixation. Intact corneal endothelium was similarly demonstrated by specular microscopy, SEM, and TEM in seven of seven "MK-shifted" corneas. These data suggest that MK-stored donor corneas may be transferred into an organ culture system at 34 degrees C for prolonged storage with maintenance of corneal endothelial cell viability.
The National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study is a multicenter clinical trial for the evaluation of radial keratotomy. This article describes the questionnaire data collected on PERK patients and compares them with a similar group of myopic persons studied during the Rand Health Insurance Experiment (heretofore referred to as the Rand study). The PERK patients are young, white myopes who dislike being dependent on corrective lenses but perceive themselves to be more visually impaired than do comparable Rand study myopes. Most female subjects and a plurality of the male subjects have tried contact lenses and quit wearing them mainly because use of the lenses was inconvenient or bothersome. There is no evidence that patients are psychologically or socially deviant. Both male and female subjects expressed a fear of being without vision and cited impatience with the lenses as their major motivation for wanting surgery.
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A retrospective review of 51 secondary intraocular lens (IOL) implantations was made to determine the relative accuracy of the SRK regression formula and the refraction method described by Holladay in preoperative prediction of emmetropic IOL power. The regression formula accurately predicted emmetropia within 1 diopter (D) in 63% of patients; the refraction method accurately predicted within 1 D in only 26% of cases. The emmetropic power predicted by the two formulas differed by at least 1 D in 76% of patients. Precise measurement of preoperative variables is imperative to ensure accurate prediction of emmetropic IOL power in the patient considered for secondary implantation.
We evaluated the safety and efficacy of 2% methycellulose as an adjunct for cataract extraction with implantation in cat and monkey models. When used intraoperatively, methylcellulose reduced the iridovitreal bulge during surgery. No significant increase in clinical inflammation occurred nor was there statistically significant intraocular pressure elevation at 24 hours, 7 days, or 90 days. In the cat model, the central corneal thickness increased at day seven in both control and methylcellulose eyes; this thickness persisted to 90 days. The endothelial cell loss decreased significantly at day 90 in methylcellulose eyes. In the monkey model, no statistically significant increase in corneal thickness occurred in control or methylcellulose eyes at day seven. The endothelial cell loss was greater than in the cat model in both control and methylcellulose eyes; there was no statistically significant difference between the two. Two percent methylcellulose was safe in both the cat and monkey models. It facilitated surgery in both models and reduced the endothelial cell loss in the cat eye.
We report a case in which a posterior chamber lens subluxated superiorly, resulting in progressive loss of vision.
Forty-seven donor corneas were preserved in McCarey-Kaufman (M-K) medium at 4 degrees C for 1 day, then in organ culture at 34 degrees C for approximately 1 month, then in M-K medium at 4 degrees C for an additional two days before transplantation. The central donor endothelium was examined by specular microscopy before and after organ culture and 2 months after keratoplasty. No significant change in central endothelial cell density occurred during organ culture. The 47 transplants were compared with 47 grafts preserved only in M-K medium at 4 degrees C for approximately 36 hours. All transplants were performed by the same surgeon over the same period, and the two groups contained similar types of surgical procedures. The organ-cultured grafts were thicker on the first post-operative day and took longer to epithelialize . Two months after keratoplasty all of the 94 grafts were clear and thin, but the mean central endothelial cell loss was 28% in the 47 organ-cultured transplants and 10% in the 47 transplants preserved only in M-K medium (P less than 0.0001). These results indicate that the endothelium of corneas preserved by organ culture at 34 degrees C and then placed in M-K medium at 4 degrees C for 2 days may be more susceptible to surgical trauma than those preserved only in M-K medium at 4 degrees C.
A review of 100 patients who underwent penetrating keratoplasty revealed 47 who required therapeutic soft contact lenses in the early postoperative period. Twelve corneal ulcer-infiltrates, 11 of which were culture positive, occurred during soft contact lens wear (23% incidence of this complication in contact lens fitted eyes). The most common offending organism was coagulase-negative staphylococcus. The only statistically significant risk factor for infection if a lens was used was the presence of a persistent epithelial defect (p = 0.03). Factors which could not be statistically correlated with corneal ulcer-infiltrate included keratoconjunctivitis sicca, the type of contact lens, the method of donor cornea preservation, lens hygiene, antibiotic and steroid usage, the presence of blepharitis, preoperative bacterial keratitis, and the history of a previously failed penetrating keratoplasty.
Fungal contamination of organ-cultured corneas was studied retrospectively. Over a 3 1/2-year period, 5.2% of 696 corneas became contaminated by fungi in organ culture. The average length of time for fungal contamination to occur in organ culture was 11 days. The most frequent contaminating fungi were those of the Candida species. In addition to previously identified risk factors for donor cornea contamination, those corneas from donors given mechanical respiratory assistance at the time of death, those corneas with long postmortem times, and those corneas with positive postwash cultures were identified as being at higher risk for fungal contamination in organ culture.
The superior supporting footplate of the Tennant-Anchor anterior chamber lens can subluxate through a basal peripheral iridectomy. In each of the three cases reported herein, the implant migrated superiorly along the ciliary body pars plana. In two cases, the lens implant was stabilized by adhesions of the superior supporting footplate to the ciliary body. In the third case, lens movement (pseudophakodonesis) caused the inferior lens footplate to rub against the corneal endothelium, producing secondary iridocyclitis and cystoid macular edema which required intraocular lens removal and exchange. This complication may be prevented by performing a mid-peripheral iridectomy or iridotomy rather than a large basal iridectomy.
Pupil capture occurs in a small percentage of patients following posterior chamber lens implantation. We noted a 3% incidence in 100 patients using sulcus fixated planar J-loop lenses, a 1% incidence using sulcus fixated angulated J-loop lenses, and a 1% incidence in capsular bag fixated flexible Y-loop lenses. No patients lost vision from pupil capture, and no clinically significant late complications were observed. Pupil capture may be successfully treated in the early postoperative period in some patients by mydriasis and a noninvasive loop compression technique using Q-tips.