Kenneth R. Kenyon

LIMBAL AUTOGRAFT TRANSPLANTATION FOR OCULAR SURFACE DISORDERS

Limbal autograft transplantation is presented in 26 consecutive cases comprising both acute and chronic chemical injury (20 cases), thermal burns (2 cases), contact lens-induced keratopathy (3 cases), and ocular surface failure after multiple surgical procedures (1 case), with follow-up ranging from 2 to 45 months (mean, 18 months). The operative technique usually involved transfer of two free grafts of limbal tissue from the uninjured or less injured donor eye to the severely injured recipient eye, the latter having been prepared by limited conjunctival research and superficial dissection of fibrovascular pannus without keratectomy. Clinical results in 21 patients with follow-up of 6 months or more have consistently shown improved visual acuity (17 cases), rapid surface healing (19 cases), stable epithelial adhesion without recurrent erosion or persistent epithelial defect (20 cases), arrest or regression of corneal neovascularization (15 cases), and probable increased success for lamellar or penetrating keratoplasty (8 cases). No intraoperative complications were encountered, and no adverse reactions developed in donor eyes. Impression cytology in selected cases showed restoration of the corneal epithelial phenotype and regression of goblet cells from the recipient cornea. Therefore, limbal autograft transplantation is recommended for treatment of widespread ocular surface damage with loss of limbal epithelial stem cells and, specifically, for chemical or thermal burns, contact lens-induced keratopathy, and selected persistent corneal epithelial defects.

The Incidence of Ulcerative Keratitis among Users of Daily-Wear and Extended-Wear Soft Contact Lenses

The wearing of contact lenses has increased dramatically in the past decade; over 4 million people in the United States now use extended-wear soft contact lenses, and 9 million use daily-wear soft contact lenses. Numerous reports have caused concern that the use of soft contact lenses, especially extended-wear lenses, may result in a substantial risk of ulcerative keratitis. To examine this issue, we conducted a prospective study in five New England states to estimate the incidence of ulcerative keratitis among those who use cosmetic extended-wear and daily-wear soft contact lenses. To obtain the numerator for each estimate of incidence, we surveyed all practicing ophthalmologists in the study area to identify all new cases diagnosed over a four-month period. To provide the denominator, we conducted a survey of 4178 households to estimate the number of persons who wore each type of soft contact lens. The annualized incidence of ulcerative keratitis was estimated to be 20.9 per 10,000 persons using extended-wear soft contact lenses for cosmetic purposes and 4.1 per 10,000 persons using daily-wear soft contact lenses for cosmetic purposes (P less than 0.00001).

The relative risk of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. A case-control study. Microbial Keratitis Study Group.

Over 13 million people in the United States wear soft contact lenses for refractive correction. Ulcerative keratitis is considered the most serious adverse effect of the use of contact lenses. We performed a case-control study with 86 cases patients, estimating separately for hospital-based (n = 61) and population-based (n = 410) controls the relative risk of ulcerative keratitis among users of extended-wear as compared with daily-wear soft contact lenses. The relative risk of ulcerative keratitis for extended-wear as compared with daily-wear lenses among the population-based controls was 3.90 (95 percent confidence interval, 2.35 to 6.48) and among the hospital-based controls, 4.21 (95 percent confidence interval, 1.95 to 9.08). Thirty-eight percent of those with extended-wear lenses used them only during the day, and 11 percent of those with daily-wear lenses occasionally wore them overnight. When lens wearers were distinguished according to their overnight use of lenses, the users of extended-wear lenses who wore them overnight had a risk 10 to 15 times as great as the users of daily-wear lenses who did not, and the users of daily-wear lenses who sometimes wore them overnight had 9 times the risk of the users of such lenses who did not. For the users of extended-wear lenses, the risk of ulcerative keratitis was incrementally related to the extent of overnight wear. A reduction in risk associated with more frequent attention to lens hygiene was almost significant. We conclude that soft contact lenses worn overnight carry a significantly greater risk for ulcerative keratitis than soft lenses worn only during the day.

Conjunctival Autograft Transplantation for Advanced and Recurrent Pterygium

The technique and results of conjunctival autograft transplantation for advanced and recurrent pterygium are presented for 57 eyes of 54 patients. The pterygia were primary in 16 eyes and recurrent in 41; among the latter group, 14 patients had diplopia resulting from cicatricial involvement of the medial rectus muscle. In all cases, free conjunctival grafts from the superotemporal bulbar conjunctiva of the same eye were used to resurface exposed sclera and extraocular muscle. There were no intraoperative complications. Postoperative follow-up ranges from 1 to 67 months, with a mean of 24 months. Only three pterygia have recurred (5.3%); two were successfully remedied by a second conjunctival autograft, whereas the third did not require an additional procedure. In all 14 patients with diplopia, extraocular movement was restored. We recommend this surgical approach as a safe and effective means of treating pterygia complicated by conjunctival scarring with extraocular muscle involvement and requiring concurrent fornix reconstruction.

Central corneal thickness measurement with a retinal optical coherence tomography device versus standard ultrasonic pachymetry.

Purpose. To demonstrate the capability of a standard, commercially available optical coherence tomography device (originally designed to measure retinal thickness) to image the human cornea in vivo and to measure central corneal thickness (CCT) in normal and edematous corneas. The intrapatient precision and interpatient variability of this novel application was compared to standard ultrasonic pachymetry. Also, the correlation of both methods was investigated. Methods. CCT measurements using optical coherence tomography (OCT) and ultrasonic pachymetry (PACH) were obtained in 36 normal eyes and 16 eyes with corneal edema. Results. Direct in vivo imaging of the cornea and measurements of CCT by OCT could be performed in all eyes. In normal subjects, CCTOCT was 530 ± 32 &mgr;m and CCTPACH was 581 ± 34 &mgr;m. The two methods showed a highly significant correlation with a standardized regression coefficient of 0.988. The difference between both methods was constant over the range of CCT (mean difference, 49.4 ± 5.9 &mgr;m). The mean intrapatient SD of CCT measurements was 4.90 &mgr;m and 4.96 &mgr;m for OCT and PACH, respectively. In patients with corneal edema, mean CCTOCT was 601 ± 59 &mgr;m, and mean CCTPACH was 667 ± 68 &mgr;m. The difference between the two techniques increased slightly with increasing corneal edema (mean difference, 66.9 ± 10.9 &mgr;m). Conclusion. Imaging of the human cornea can be performed by a standard retinal OCT device, and OCT measurement of CCT shows excellent correlation to values obtained by PACH, giving similar readings separated by a constant difference. In corneal edema, the difference between the two methods is additionally increased, but continues to demonstrate excellent consistency.

Adverse Reactions to Virgin Silk Sutures in Cataract Surgery

During the past 3 years, 12 patients (14 eyes) were encountered with severe reactions to virgin silk sutures used in cataract surgery. These reactions included nodular episcleritis, peripheral corneal ulceration, and wound necrosis with dehiscence, sometimes resulting in endophthalmitis or epithelial downgrowth. Conjunctival and scleral histopathologic studies in four eyes showed acute and chronic inflammation with multinucleated giant cells. Successful treatment included removal of the virgin silk sutures, resuturing with 10-0 nylon sutures, securing the necrotic tissue with cyanoacrylate adhesive, and resection of the inflamed superior conjunctiva. All four patients who had bilateral cataract surgery experienced either simultaneous flare-ups of both eyes or accelerated reactions after surgery on the second eye, which suggests a possible role of prior sensitization.

Ocular Manifestations of Graft-vs-Host Disease

In patients who have graft-vs-host disease (GVHD) after bone marrow transplantation, ocular involvement occurs in approximately 60% of cases. Among 13 such GVHD patients, the most frequent ocular manifestations included keratoconjunctivitis sicca, cicatricial lagophthalmos, and sterile conjunctivitis and uveitis. The severe ocular complications of persistent corneal epithelial defects and both noninfected and infected stromal ulceration were related to the concomitant dry-eye condition and could be managed by conventional therapy including topical lubricants and antibiotics, punctal occlusion, bandage soft contact lenses, tarsorrhaphy, tissue adhesive, conjunctival flap, and conjunctival homograft. Postmortem and surgical tissues from four patients revealed conjunctival and corneal epithelial thinning and keratinization, lacrimal inspissation without inflammatory infiltration, and diffuse choroiditis. Keratoconjunctivitis sicca in GVHD patients might be a combined result of drug toxicity effects and GVHD. The frequent and potentially severe ocular problems in these patients suggest that close ophthalmic monitoring is mandatory in bone marrow transplant recipients.

Possible Mechanisms for the Loss of Goblet Cells in Mucin-deficient Disorders

By studying the pathological changes in human conjunctival flaps and the conjunctival transdifferentiation in rabbits, we have identified and correlated two pathological processes with the loss of goblet cells: (1) loss of vascularization, and (2) intense inflammation. Loss of vascularization may be correlated with the loss of goblet cells in the chronic cicatricial stage of various mucin-deficient disorders, whereas inflammation may be responsible for their absence in the acute inflammatory stage. The exact interrelationship between these two processes remains unknown. The loss of goblet cells appears to be an early sign of a spectrum of squamous metaplasia, an abnormality of epithelial differentiation. We therefore speculate that loss of vascularization and intense inflammation may have an important effect on epithelial differentiation.

Conjunctival autograft for primary and recurrent pterygia : Surgical technique and problem management

The surgical technique and postoperative problem management of conjunctival autograft transplantation for advanced primary and recurrent pterygium are reviewed. Problems such as graft edema, corneoscleral dellen, and epithelial inclusion cysts infrequently occur. Corneal astigmatism, Tenons granuloma, retraction and/or necrosis of the graft, and muscular disinsertion are even less frequently encountered. Limbal-conjunctival autograft for recalcitrant recurrent cases is proposed.

Specializations of the Unit Membrane

The three-layered unit membrane is a structure showing several modifications not only in its thickness but also in the nature and amount of materials associated with its outer and inner surfaces. Indeed, the presence of associated layers is so constant that one is led to wonder whether the unit membrane as commonly defined should not be regarded as merely the central component in a complex and highly variable structure which marks cell boundaries. The variation in thickness first pointed out by Ledbetter (1962) for the plant cell has since been described by Sjostrand (1963) among others, in the animal cell. In plant cells, for example the plasma membrane and that of the tonoplast measure about 100–120 A, whereas the limiting membranes of the mitochondria and chloroplasts fall in the 50–70 A range. This kind of variation is now so well known that it requires neither illustration nor further comment.