Timo Tervo

Laser in situ keratomileusis flap margin: wound healing and complications imaged by in vivo confocal microscopy

PURPOSE To examine the healing response of laser in situ keratomileusis flap margin in vivo. METHODS Forty-three eyes of 43 patients who had undergone myopic (n = 39) or hyperopic (n = 4) laser in situ keratomileusis were examined once after surgery. The flap margin was imaged by in vivo confocal microscopy at various depths, and the wound healing response, flap alignment, and complications were evaluated. Ten eyes were examined on day 3 postoperatively, 13 eyes at 1 to 2 weeks, 10 eyes at 1 to 2 months, five eyes at 3 months, and five eyes at 6 months or later. RESULTS At 3 days after laser in situ keratomileusis, the surface epithelium and basal epithelium appeared normal. Keratocyte activation was strongest at 1 to 2 weeks and 1 to 2 months, and an increased amount of haze was observed correspondingly. Intrastromal epithelial cells forming a plug could occasionally be perceived in the wound gape. Wound constriction was completed in most cases by 3 to 6 months or later. Good alignment was observed in 12 of 43 flaps (27.9%) and moderate and poor alignment in 17 of 43 flaps (39.5%) and 13 of 43 flaps (30.2%), respectively. Poor alignment was not associated with lamellar epithelial ingrowth. Epithelial ingrowth was associated with dense haze at the interface. Diffuse lamellar keratitis was imaged in two corneas after hyperopic laser in situ keratomileusis. CONCLUSIONS The laser in situ keratomileusis incision wound at the flap margin appears to heal after the sequence observed in incisional wounds in nonhuman primates. Complications, such as lamellar epithelial in growth and diffuse lamellar keratitis, were often observed, particularly after hyperopic laser in situ keratomileusis.

EPIDERMAL GROWTH FACTOR (EGF) IN OCULAR FLUIDS: PRESENCE, ORIGIN AND THERAPEUTICAL CONSIDERATIONS

Epidermal growth factor (EGF) is a potent stimulator of cell proliferation and maturation (Cohen & Elliott, 1963; Cohen et al., 1975). EGF is known to occur in a variety of human body tissues and fluids (Carpenter 1985; Pesonen et al., 1987, Hayashi & Sakamoto, 1988). However, although EGF promotes healing of the corneal endothelium in various sepcies (Fabricant et al., 1982; Raymond et al., 1986), no EGF has been detected so far in the anterior chamber fluid of humans (van Setten et al., 1988). Although normally present in tear fluid (van Setten et al., 1989; Ohashi et al., 1989), EGF enhances epithelial migration and promotes wound healing when applied topically to the cornea (Savage & Cohen 1973; Ho et al., 1974; Daniele et al., 1979; Woost et al., 1985; Watanabe et al., 1987; Calel & Fagerholm 1987; Schultz et al., 1988; Singh & Foster 1987). The combined application of EGF and fibronectin (FN), a glycoprotein that promotes cell adhesion (Ruoslahti, 1988) on the cornea is also under investigation (Schultz et al., 1988; Kawaba et al., 1984; Singh & Foster, 1989). However, although EGF is clearly a powerful therapeutic agent for enhancing corneal wound healing (Burstein, 1987; Tripathi et al., 1990), ex-

Substance P Immunoreaction and Acetylcholinesterase Activity in the Cornea and Gasserian Ganglion

Nerves showing acetylcholinesterase (AChE) activity or immunoreactivity for substance P (SP) were demonstrated in the human cornea. AChE-positive fibres were found in stromal nerve trunks from where they penetrated Bowmans membrane and formed a basal epithelial plexus. Intraepithelial terminals arose from this network. SP immunoreactive nerve fibres showed similar architecture but were fewer. Both SP immunoreaction and histochemical AChE reaction were demonstrated consecutively in the same tissue section cut from both human and rabbit cornea. Stromal nerve trunks were found to contain SP immunoreactive and AChE-positive nerve fibres. However, the AChE-positive fibres were much more frequent than those immunoreactive for SP. In the rabbit Gasserian ganglion all neurons showed AChE activity but only some 20% were SP positive. It is concluded that all the sensory trigeminal nerve fibres of the cornea show AChE activity but only a proportion of them contain SP-like material.

INTEGRINS AS RECEPTORS FOR EXTRACELLULAR MATRIX PROTEINS IN HUMAN CORNEA

Abstract Extracellular matrix (ECM) proteins form distinct proteinfamilies that play a role during tissue maturation, wound healing and maintenance of tissue architecture. Recent studies show that there are tissue type ‐specific variations in their expression. ECM proteins function by complexing with each other and also by interacting with their cellular receptors, called integrins. Integrins are heterodimeric membrane.

Cortisone, heparin and argon laser in the treatment of corneal neovascularization

Abstract  Chemical burns and contact lenses can induce corneal neovascularization. The pathogenic mechanisms of angiogenesis are not well understood. A heparin‐cortisone combination has been shown to inhibit traumatic angiogenesis and argon laser photocoagulation has been useful in the treatment of corneal graft neovascularization.

Tear Fluid Changes after Photorefractive Keratectomy

Correction of refractive errors by excimer laser photorefractive keratectomy (PRK) is based on remodelling of the corneal curvature by highly controlled photoablation of the anterior corneal stroma.1 Tear fluid cytokines or other modulators produced by inflammatory cells, nerve cells, corneal epithelial or stromal cells, or extracellular matrix are likely to regulate the healing of the photoablated area.2–9 As the healing of the wound determines the refractive result, it is most important to study the mechanisms that control the healing response.

Pseudomembranous and membranous conjunctivitis Immunohistochemical Features

Abstract A 63‐year‐old man, who had for one month been on sulfasalazine therapy, developed general malaise, high fever, severe stomatitis, and bilateral necrotizing pseudomembranous conjunctivitis with corneal erosion, identical to that seen in the Stevens‐Johnson syndrome. Topical therapy with antibiotics and aprotinin rapidly healed the corneal surfaces, while densely adherent true membranes developed on the conjunctiva, and were removed surgically several times during the next week. After the acute stage, subtle subepithelial conjunctival scarring, superficial punctate keratitis, dry eye syndrome and fluctuating irregular corneal astigmatism became evident, but good visual acuity, lid function and ocular motility were retained. Histopathologic study of conjunctival membranes from two cases of membranous conjunctivitis revealed polymorphonuclear leukocytes within a matrix composed of fibrin, tenascin and fibronectin. In older membranes, histiocytes were additionally found. Surgical debridement of such membranes removes a substratum of inflammatory debris that is likely to promote secondary infection, fibrosis and symblepharon formation, and may decrease rather than increase subsequent scarring of the necrotized conjunctiva.

Leukocyte rolling and extravasation in surgical inflammation after mechanical and laser-induced trauma in human patients

Acute inflammations main characteristics are exudation of fluid and plasma proteins and emigration of leukocytes, predominantly neutrophils into inflamed tissue. We have previously demonstrated that leukocyte extravasation can be directly monitored in human patients in vivo after tunnel cataract operation, but at the same time we noticed that only certain manipulations trigger also leukocyte extravasation. To define the type of surgical manipulations triggering leukocyte extravasation, we tested a set of surgical manipulations affecting distinct anatomical components of the conjunctiva. This set included various combinations of epithelial, nerve, and/or blood vessel damage. Manipulations tested here were surgical conjunctival biopsy, low-energy Argon laser treatment (80 mJ) closing a venule temporarily, high-energy argon laser treatment (480 mJ) to occlude a venule firmly, and 193 nm eximer laser-based conjunctival phototherapeutic keratectomy (160 mJ). These manipulations were compared to previous findings on conjunctival inflammation following the standard cataract operation. In mechanical trauma models (cataract operation and conjunctival biopsy) clinical signs of inflammation, number of leukocytes rolling, and number of tissue emigrated leukocytes were notably higher compared to pre-operative levels on one day after the operation. No specific anatomical triggering component for inflammation, including epithelial, nerve, and/or blood vessel damage, was indentified, but rather the trauma mechanism itself appeared to be an essential factor. Surprisingly, in laser-induced traumas no increase in number of rolling cells, rolling velocity slowing, or elevation of tissue emigrated leukocytes took place compared to pre-operative levels. These findings suggest that laser-induced traumas differ fundamentally from the mechanical traumas at all levels of leukocyte extravasation cascade, and at least in our setup, inflammatory reaction can be avoided or triggered depending on surgical method used.

Wound Healing Modulators in Tear Fluid

Unexpected variations in corneal wound healing affect the predictability of photorefractive keratectomy (PRK). Several modulators coming from tears, inflammatory cells, extracellular matrix, nerve cells, corneal epithelial cells, or stromal fibroblasts can regulate the complex wound healing process. This report evaluates the presence and release of these modulators in tear fluid following PRK. The release of plasmin, cellular fibronectin, tenascin and calcitonin gene-related peptide (CGRP) into tears following excimer laser keratectomy has been shown to be increased during the first postoperative days. Lately studies have focused on growth factors/cytokines. The release of hepatocyte growth factor (HGF), transforming growth factor-βl (TGF-βl), vasoendothelial growth factor (VEGF), and tumor necrosis factor-α (TNF-α) in tear fluid is also significantly increased during the first two days after excimer laser-induced corneal wound. These healing modulators are likely to regulate epithelial differentiation, proliferation, and migration; cell-to-cell and cell-to-matrix interactions; stromal extracellular matrix production; and transition of keratocytes into contractile myofibroblast-like cells. They are possibly also involved in the formation of postoperative stromal scar.