Excimer laser photoablation. Clinical results and treatment of complications in 1992.
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Animals↗
Biomedical subjects
P S Binder
Publications and source records attributed to P S Binder.
Three versus four radial keratotomy incisions.
Radial keratotomy (RK) is currently performed with four or eight semi-radial incisions. To evaluate the effect of a theoretically more stable three-incision RK pattern, centripetal incisions were made in 16 human donor eyes (eight pairs), using a double-edged diamond blade set to 90% of central pachymetry and a 3.5 mm optical clear zone. Intraocular pressure was maintained at 15 mm Hg during surgery and while keratometry readings were made. One randomly selected eye of each pair had three radial incisions made at 12, 4 and 8 o'clock; the other eye had four radial incisions at 12, 3, 6, and 9 o'clock. Corneal flattening was 6.08 diopters (D) with four incisions and 4.84 D with three incisions (P less than .05). Astigmatism increased 0.44 D and 0.69 D, respectively (P greater than .1). Histologically measured mean incision depth (77.4%) did not differ significantly between the groups (P greater than .1). This study shows that 80% of the effect of a four-incision RK pattern can be obtained with a theoretically more stable three-incision pattern.
Aged↗
Evaluation of tear protein deposits on contact lenses from patients with and without giant papillary conjunctivitis.
Giant papillary conjunctivitis (GPC) associated with contact lens wear is believed to result from an irritative or allergic response to accumulated lens surface deposits. In a masked study, contact lenses worn short-term (2 weeks or less) or long-term (2-12 months), and obtained from patients with and without active GPC, were examined for deposited proteins: IgA, IgE, IgG, IgM, lactoferrin, and lysozyme. Using immunohistochemical methods lenses were separately graded on a 4+ scale for extent of protein coverage. All lenses showed substantial deposits (averaging 50-75% lens coverage) of the normal tear proteins, with the exception of IgE which averaged less than 25% lens coverage; maximum protein deposition was apparent on lenses worn for only 3 days. Both symptomatic and asymptomatic persons deposited similar amounts of the common tear proteins on their contact lenses, with the exception of IgM. A statistically significant increase in IgM deposition was found when the short-term GPC lenses were compared to short-term asymptomatic lenses. Our data suggest that the development of GPC does not depend on amount of deposition of the normal tear proteins IgA, IgG, IgE, lactoferrin or lysozyme. Differences observed in IgM deposition may reflect an immune response in GPC.
Conjunctivitis, Allergic↗
Fitting the SoftPerm contact lens after keratoplasty.
We fit 22 eyes (20 patients) with the SoftPerm lens following keratoplasty when the potential acuity meter test exceeded the best corrected spectacle refraction. Fourteen eyes had more than 4 D of astigmatism. Fourteen of the 22 lenses were worn successfully for more than 3 months. Nineteen of 22 eyes achieved better acuity than with spectacles alone. Separation of the lens at the bonded junction and an inability to insert and remove the lens accounted for the majority of failures. We consider the SoftPerm lens whenever we encounter high astigmatism cases that have better potential acuity readings than best corrected spectacle acuity.
Adult↗
Propagation of human corneal endothelium in vitro effect of growth factors.
Endothelial cells were obtained from 23 human corneal-scleral rims. Donors were 0.2-37 yr of age. Most cultures obtained from donors under 30 yr ceased to grow after the seventh passage (3-24 weeks). Growth from 17- and 25-yr-old donors were maintained for nine passages (26 weeks) and 18 passages (100 weeks), respectively. Cultures were established from 12 rims, using growth factors in uncoated culture flasks or epidermal growth factor (EGF) in an extracellular matrix-coated (ECM) flask. EGF improved the growth potential of the cells; a combination of an ECM-coated-tissue culture flask with EGF in the medium provided an improved environment for continuous growth.
Adolescent↗
The coupling phenomenon and corneal transplantation.
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Astigmatism↗
Air/liquid corneal organ culture: a light microscopic study.
Air/liquid organ culture of tissues with stratified epithelial layers has been shown to encourage tight packing of cells and promote cellular differentiation. In this study human corneas cultured in a air/liquid environment were compared to paired, conventionally-cultured corneas to determine if the long-term morphology could be improved. Fourteen paired human corneas were cultured at 37 degrees C in covered culture dishes for 1 to 3 weeks. Air/liquid cultured corneas were placed epithelial-side up in a fixed position and culture medium was added to a level so that during rocking the corneal epithelia were intermittently exposed to air/liquid environments. Mate corneas were cultured using the conventional method. In this method corneas are fully submerged, epithelial-side down, in culture medium. After 3 weeks of culture significantly less epithelial intercellular edema was noted for the air/liquid cultures (p = 0.033), compared to conventional cultures. Significant improvements in cellular structure of the endothelial layers, after 1 and 3 weeks incubation (p = 0.029 and 0.000) and stromal layers, after 3 weeks in culture (p = 0.024), were also noted. We have shown that slight modifications of the organ culture environment lead to improvements in corneal morphology. Air/liquid corneal organ culture has promise for use in corneal wound healing studies and long-term culture.
Aged↗
High-voltage electron microscopy of normal human cornea.
Conventional transmission electron microscopy (CTEM) was compared with high-voltage electron microscopy (HVEM) on 11 normal human corneas (age range, 30 weeks of gestation to 92 yr). Epithelial anchoring fibrils were noted between the basal epithelial cells and Bowman's layer (BL) as previously reported. Parallel pairs of fibers, 27.5 nm in diameter, were observed crossing into the anterior stromal lamellae from BL; their termination sites, however, were not identified. The lateral termination of BL was marked by the presence of a keratocyte lying directly below the end of the multilaminar basal lamina. In this region, BL tapered and became interwoven with the scleral collagen fibrils in the substantia propria. The HVEM accentuated the orthogonal relationship of collagen bundles apparently emerging from the stromal keratocytes. The posterior corneal stroma appeared to be attached to the anterior surface of Descemet's membrane (DM) by fibers 22.3 nm in diameter that were associated frequently with a dense amorphous material. In the periphery, DM tapered to a thin strand, 0.5 microns in thickness, containing cable-like strands of banded collagen. The posterior nonbanded portion continued laterally and anteriorly in a series of folds between the fibrous collagen sheets of the anterior trabecular meshwork. In addition, HVEM enhanced the visibility of extracellular matrix interactions in the lateral terminations of BL and DM, attachment fibers from BL to the stroma and from the stroma to DM, and keratocyte and collagen fiber orientations not seen easily by CTEM.
Adolescent↗
Radial keratotomy in the 1990s and the PERK Study.
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Follow-Up Studies↗
A comparison of wound healing in sutured and unsutured corneal wounds.
We compared corneal wound healing in 25 clear transplants with 26 keratotomy specimens and sutured and unsutured corneal wounds in a monkey model. Monkey wounds healed faster than human wounds, but healing time within the same species varied. Sutured wounds were characterized by subepithelial fibroplasia, recovery of collagen fiber continuity and absence of epithelial plugs. Unsutured wounds had no subepithelial fibroplasia but had fibroblasts and collagen fiber orientation parallel to wounds. Unsutured wounds in corneas containing sutures had subepithelial fibroplasia, and fibroblast orientation and fiber deposition parallel to the wound. Epithelial ingrowth and incarceration of Bowman's layer and/or Descemet's membrane in unsutured wounds appeared to disrupt wound healing. Abnormalities in wound healing in sutured or unsutured wounds are associated with lamellar distortion, a modified inflammatory response, and individual wound healing responses.
Adult↗
Corneal epithelial and stromal reactions to excimer laser photorefactive keratectomy. III. The excimer laser and radial keratotomy: two vastly different approaches for myopia correction.
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Humans↗
Substance P contracts the human iris sphincter: possible modulation by endogenous enkephalinase.
Substance P-immunoreactive neurons have been found in the irides of many species including humans. In several species, substance P has been shown to induce contraction of the sphincter muscle but this action of substance P has not been previously demonstrated in the human eye. Using an eye cup model in which the sensitivity of the iris muscle to substance P is increased compared to the isolated sphincter muscle, we have observed that nanomolar amounts of substance P induced contraction of the sphincter in the human iris. This contractile response was enhanced in eyes pretreated with thiorphan, an enkephalinase inhibitor, suggesting that endogenous enkephalinase (E.C. 3.4.24.11) may modulate the substance P contraction in the human iris. Further support for this hypothesis was the finding of enkephalinase-like immunoreactivity and enzyme activity in the human iris sphincter muscle.
Aged↗
The effect of epinephrine and benzalkonium chloride on cultured corneal endothelial and trabecular meshwork cells.
We evaluated the effect of dipivefrin hydrochloride, epinephrine hydrochloride, epinephrine borate and their respective vehicles with and without the preservative benzalkonium chloride, on the in vitro growth characteristics of human corneal keratocytes, endothelial cells and trabecular meshwork. Epinephrine hydrochloride and borate at low concentrations (0.0002%) significantly inhibited growth of both trabecular meshwork and corneal endothelial cells. Higher concentrations (0.02%) of these same drugs induced the same effect on the growth of keratocytes in vitro. Similar observations were made on the effect of dipivefrin hydrochloride on human corneal cells in vitro. Benzalkonium chloride alone was demonstrated to be responsible for the growth inhibitory effects on trabecular cells. The susceptibility of trabecular meshwork cells in culture to the commonly used ophthalmic preservative benzalkonium chloride is demonstrated.
Benzalkonium Compounds↗
Refractive surgery in the United States.
In a mere 8 years, refractive corneal surgery in the United States has become a commonly practiced procedure. The major procedures being performed today are keratotomy for the correction of myopia and astigmatism and epikeratoplasty for the correction of aphakia. Current, on-going clinical studies involving intrastromal implantation of hydrogel materials have just begun. Clear lens extraction for myopia and intraocular lens implantation in high myopia at the time of cataract surgery are being used more commonly each day. Recognition of and modification of pre-existing corneal astigmatism at the time of cataract surgery has been able to provide patients with much improved visual acuity after surgery.
Astigmatism↗
Three techniques for combined ECCE, PC-IOL implantation, and keratoplasty.
Three different techniques are described for implanting posterior chamber lens implants during a combined extracapsular cataract extraction, posterior chamber lens implantation, and keratoplasty procedure. The implant can be placed immediately following cataract extraction, after which the cornea is replaced. If cortical remnants cannot be completely removed, the corneal transplant is sutured in place and a limbal incision made; the remaining remnants are then aspirated and a posterior chamber lens is implanted through the limbal incision. If no remnants remain, but the posterior chamber lens cannot be implanted due to positive vitreous pressure, the cornea is sewn into place with seven or eight interrupted sutures and the lens implanted through the remaining open quadrant, after which the corneal transplant procedure is completed.
Cataract Extraction↗
Cryotherapy for medically unresponsive acanthamoeba keratitis.
Five cases of culture-proven Acanthamoeba keratitis underwent cryotherapy to the host cornea as an adjunctive treatment to medical and surgical therapy. Four of the 5 cases had progression of disease while receiving medical therapy considered to be appropriate for Acanthamoeba keratitis. One case underwent cryotherapy to the entire cornea after the disease had recurred in two penetrating keratoplasties; the organisms were eliminated but the patient never recovered useful vision. Two cases underwent cryotherapy to the host cornea at the time of a second penetrating keratoplasty. The organism was eliminated in both cases. Two cases underwent cryotherapy to the host cornea at the time of primary corneal transplantation with elimination of the organism and recovery of excellent acuity. This study does not provide conclusive evidence that cryotherapy eliminated the organism, but suggests that it can be an adjunctive measure to medical and surgical therapy. The risks of the adverse effects of freezing of the cornea must be weighted against the possibility of recurrence after keratoplasty with spread of disease to the sclera or to the development of corneal melting and perforation. Prevention of Acanthamoeba keratitis is by far the best approach to this disease entity.
Acanthamoeba↗
Corneal surface ablation by 193 nm excimer laser and wound healing in rabbits.
The 193 nm argon fluoride excimer laser was used to ablate a 6 mm diameter area of the central rabbit cornea under various conditions of power, beam configuration and exposure time. High repetition rates or prolonged exposures produced charring and prevented rapid epithelial wound closure. Endothelial vacuolization, reduction in density, and displacement of cell material into Descemet's layer resulted in these experiments. A beam of low and uniform power intensity (40 pulses per second, 100 seconds at 23 mJ/cm2) reduced stromal damage, cellular infiltration, and epithelial irregularities including punctate staining and cell exfoliation. Epithelial rehealing occurred within two days. Basal lamina and hemidesmosomes were reformed by one week. Endothelial damage was not detected. Excimer laser ablation may allow removal of superficial dystrophies or scars, followed by rapid healing from normal corneal reparative processes.
Animals↗