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Biomedical subjects

G O Waring

Publications and source records attributed to G O Waring.

At least 145 records · Page 8Linked to original sources
PubMed1986

Hydrogel keratophakia: a microkeratome dissection in the monkey model.

High water content intracorneal implants were fabricated from Vistamarc hydrogel (Vistakon, Inc.) at 58%, 68%, and 72% water content and a range of powers from +7.25 to +17.00 dioptres. The Barraquer microkeratome technique was used to implant the lens at 59.0 +/- 9% (+/- SD) depth in the corneas of 14 rhesus monkey eyes. The contralateral eye served as a control. Three eyes were lost to the study because of complications. The remaining 11 animals were followed up for 51 +/- 2 weeks with the refractive yield being 118 +/- 34% and the keratometric yield being 92 +/- 30%. The measured and theoretically expected refractive changes have a linear regression line correlation coefficient of 0.74, whereas the respective keratometric data had a correlation coefficient of 0.04. The measured refraction became stable within 2 to 3 dioptres after 20 postoperative weeks. The hydrogels were well tolerated within the corneal tissue. There was a minimum of interface problems except along the edge of the implant. Implants with abruptly cut edges versus a fine wedge tended to have more light scattering collagen at the implant margin.

Animals↗
PubMed1986

Decreased fibronectin levels in aqueous humor after corneal injury.

Fibronectin plays an important role in wound healing and cell differentiation. The present study measures fibronectin levels in aqueous humor from injured corneas. In response to transcorneal freezing treatments, a thickened scar-like matrix is deposited on the posterior surface of rabbit corneas. This posterior collagenous layer (PCL) is visible grossly and has a uniform diameter. Aqueous humor from eyes with established posterior corneal scarring has significantly less fibronectin compared with control eye aqueous humor. Tissue culture experiments show that corneal endothelial cells from control eyes and PCL-associated cells from injured eyes produce similar amounts of fibronectin. The marked decline in fibronectin levels in aqueous humor in scarred corneas supports the hypothesis that fibronectin plays a role in the pathological events which result from corneal injury.

Animals↗
PubMed1985

Slit-lamp microscopic appearance of corneal wound healing after radial keratotomy.

Radial keratotomy offers a unique opportunity to study corneal wound healing because the corneas are normal, the fine knife blades disrupt adjacent tissue minimally, no sutures are used, there is minimal inflammation, and few postoperative drugs are administered. We studied corneal wounds with a slit-lamp microscope as they healed from two weeks to three years after radial keratotomy in 84 eyes of 51 consecutive patients enrolled in the Prospective Evaluation of Radial Keratotomy (PERK) Study. One day after surgery, the incisions were surrounded by edema. At two weeks, a dense, gray, diffusely marginated opacity occupied 0.1 mm on both sides of the incision. At three months, the area adjacent to the incision was filled with discrete, fine, gray spicules that protruded at right angles from the incision. At six months, the gray cloudiness had completely disappeared, and the individual spicules were more prominent. By one year, the spicules were disappearing from the anterior portion of the incision and were concentrated primarily in the posterior part of the incisions. At two and three years, the incision scar was fainter and the spicules had disappeared from all but the deep posterior part of the wound. We believe that these spicules correspond to the reorganization of the stroma along the edges of the corneal incision. The persistence of the spicules suggests that wound healing in radial keratotomy may not be complete until two years or more after surgery.

Cicatrix↗
PubMed1985

Postoperative astigmatism after central vs eccentric penetrating keratoplasties.

Six patients with markedly eccentric penetrating keratoplasties had severe corneal astigmatism (mean, 10.38 +/- 2.91 diopters). In four of these patients the flat meridian was lying in the direction of graft displacement. Laboratory experiments disclosed no statistically significant difference in diameter between the major and minor axes of the corneal buttons in the centrally and eccentrically trephined eyes and we could not elucidate the mechanism of the severe astigmatism. However, in the eccentrically trephined eyes the longer axis consistently lay in the direction of decentration whereas in the centrally trephined eyes the long axis was oriented randomly.

Astigmatism↗
PubMed1985

Results of the prospective evaluation of radial keratotomy (PERK) study one year after surgery.

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.

Adult↗
PubMed1985

Evolution of radial keratotomy for myopia.

The basic principles of radial keratotomy for myopia were described in 1898: radial incisions flatten the cornea in the direction of the incision, deep incisions were more effective, and some of the result diminished as the cornea healed. Since then the surgical procedure has undergone evolution and refinement, with changes now occurring rapidly. The acronym STEPS provides a useful guide in evaluating the operation: safety, technique of surgery, efficacy, predictability, stability, and each of these subjects will be discussed.

Animals↗
PubMed1984

Changes in corneal curvature induced by sutures and incisions.

To clarify the mechanisms by which incisions and sutures produce corneal astigmatism, we made incisions and wedge resections closed by sutures in the corneoscleral limbus of human eye bank eyes, studying the changes in corneal curvature by shadowgraph photography of the corneal contour, by central keratometry, and by measurement of corneal diameter. The compression of tissue within the sutures or the closure of an excision of a wedge of tissue by sutures induced astigmatism in the meridian of surgery regardless of changes in the sagittal depth of the anterior chamber. Sutures and wedge resections closed by sutures in the anterior part of the cornea compressed or removed more tissue from the anterior part than the posterior part, producing a depression of the limbal cornea toward the anterior chamber and steepening the central cornea in the meridian of surgery. The corneal diameter decreased in that meridian. In the opposite meridian, the cornea flattened, the corneal diameter increased, and the sagittal depth decreased.

Astigmatism↗
PubMed1984

Stellate iron lines in the corneal epithelium after radial keratotomy.

Biomicroscopic examinations of the corneal epithelium of 54 patients who had consecutive radial keratotomy operations in the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) study showed that abnormal stellate epithelial iron lines had appeared at the junction of the middle and inferior thirds of the cornea in 13 of 16 eyes (81%) examined six months after surgery, in 43 of 50 eyes (86%) examined 12 months after surgery, and in seven of nine eyes (78%) examined 24 months after surgery. The density and pattern of the deposits varied from a faint tan horizontal iron line studded with small branches to a dense yellow-brown deposit with eight radiating arms that extended between all of the incisions. Analysis of the configuration of the iron line and the central keratometric readings 12 months after surgery showed that the greater the reduction in the central keratometric measurement postoperatively, the more prominent the iron line. We attribute the occurrence and variation of the stellate epithelial iron line to irregularities in the surface of the cornea present in the first year after radial keratotomy.

Adult↗
PubMed1984

Psychosocial characteristics of candidates for the prospective evaluation of radial keratotomy (PERK) study.

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.

Adolescent↗
PubMed1984

Penetrating keratoplasty for exogenous Paecilomyces keratitis followed by postoperative endophthalmitis.

Three patients developed Paecilomyces lilacinus keratitis while being treated with topical corticosteroids and antibiotics. The first patient, a diabetic man, suffered superficial ocular trauma while being treated for recurrent anterior uveitis related to an iris-fixated intraocular lens. The second patient developed keratitis while being treated for anterior segment inflammation associated with herpes zoster ophthalmicus. The third patient, a woman with chronic lymphoma in remission, was receiving topical antibiotics and corticosteroids for a corneal transplant performed one year previously. All three patients underwent penetrating keratoplasty after progression to perforation or failure of medical therapy. Two eyes (cases 1 and 2) eventually required enucleation. The fungal isolates demonstrated in vitro resistance to amphotericin and natamycin with greater sensitivity to imidazole derivatives. Thus, we recommend prompt and prolonged topical treatment with miconazole or other imidazole derivatives along with avoidance of penetrating keratoplasty and corticosteroids.

Aged↗
PubMed1984

Clinical and pathologic description of 17 cases of corneal intraepithelial neoplasia.

In 17 patients with corneal intraepithelial neoplasia (dysplasia), the epithelium formed a gray plaque at the corneal limbus adjacent to a conjunctival papilloma in seven cases, leukoplakia in six cases, a pterygium in one case, and a pinguecula in one case. The lesion was an extension of a similar neoplastic process of the conjunctiva in 15 cases, was associated with chronic conjunctivitis in one case, and was isolated to the cornea in one case. Fine white dots mottled the opalescent, ground-glass sheet, whose fimbriated leading edge consisted of sharply demarcated gray fingers that extended to the visual axis in some cases. The disorder can wax and wane spontaneously, shown in one case observed for 16 years. Histopathologically, the thick, hypercellular corneal epithelium abutted sharply against adjacent normal epithelium and demonstrated both cellular pleomorphism and poor intercellular adhesion in the deeper layers. The adjacent conjunctival neoplastic lesions ranged from mild dysplasia to invasive squamous cell carcinoma. Ultrastructurally, the corneal epithelium showed a marked decrease in desmosomal attachments, an abundance of intracytoplasmic filaments characteristic of keratin, and a loss of epithelial basement membrane and hemidesmosomes. The lesion did not extend into Bowman's zone. We classify this dysplastic process as a mild form of corneal intraepithelial dysplasia, a term used to designate the spectrum of epithelial changes ranging from dysplasia to carcinoma in situ. The virulence of the corneal lesion itself is low.

Adult↗
PubMed1984

A cluster of cases of Mycobacterium chelonei keratitis associated with outpatient office procedures.

We studied three cases of keratitis caused by Mycobacterium chelonei, a nontuberculous mycobacterial species. The cases occurred in two women, 76 and 80 years old, and one man, 67 years old, treated as outpatients in the same office. One case followed suture removal and the other two occurred after posterior capsulotomy. Corneal lesions appeared within two to three weeks of trauma and were white, round infiltrates with indistinct margins and radiating projections. The lesions were found at all levels of the stroma and were associated with an epithelial defect. Anterior chamber reaction varied from a minimal response to a hypopyon. One patient responded to topical therapy with amikacin and erythromycin, but the other two patients required penetrating keratoplasties because of deep abscesses, which progressed toward the sclera despite therapy. These cases emphasized the possibility of rapidly growing nontuberculous mycobacteria producing serious ocular infections.

Aged↗