Comparison of yellow dye, continuous wave Nd:YAG, and argon green laser on experimentally induced corneal neovascularization.

BACKGROUND: Corneal neovascularization is generally undesirable because it can lead to corneal scarring, lipid deposits, and corneal graft failure. To eliminate these vessels, several techniques are available including laser photocoagulation. METHODS: This prospective study was designed to compare the effectiveness of three laser wavelengths (continuous wave Nd:YAG, 1064 nm; argon green 514 nm; and yellow dye, 570 nm) to obliterate experimentally induced corneal neovascularization in the rabbit. Corneal vascularization was created in 12 rabbits by placing 7-0 silk sutures through two quadrants of the cornea. Once neovascularization was complete, the suture was removed and one of the three lasers was applied to occlude vessels at one of the neovascular sites. The other site was used as a control. RESULTS: The yellow wavelength, when compared with the green required fewer exposures to occlude corneal vessels. At no time during observation was any laser more effective than the control. In the continuous wave Nd:YAG group, tissue necrosis was needed to achieve closure of vessels. CONCLUSIONS: Yellow and green laser light are equally effective in eliminating the corneal vessels. Continuous wave Nd:YAG, as used here, appears to be a poor choice.

Treatment of myopic astigmatism with the 193 nm excimer laser utilizing aperture elements.

In this paper, we examine the 193 nm excimer laser's efficacy and safety in treating myopic astigmatism. The VISX Twenty/Twenty excimer laser uses aperture elements to effect astigmatic photorefractive keratectomy. In 70 patients with six months follow-up, the average postoperative sphere was -0.14 and the average postoperative cylinder was -0.54. Seventy-one percent of these patients had uncorrected visual acuity of 20/40 or better at six months. In 12 patients with one year follow-up, the average postoperative sphere was -0.05 and the average postoperative cylinder was -0.59. Eighty-three percent of these patients had uncorrected acuities of 20/40 or better; none had a clinically significant loss of best corrected acuity. This investigation demonstrates that the excimer laser can be used to treat myopic astigmatism successfully.

The role of fibroblast inhibitors on corneal healing following photorefractive keratectomy with 193-nanometer excimer laser in rabbits.

Corneal stromal haze has been seen following photorefractive keratectomy with the 193-nanometer excimer laser. Topical antimetabolites aimed at decreasing the haze have been investigated in the rabbit model. We used the VISX 193-nanometer excimer laser to create 6.0-millimeter, -5.00-diopter ablations in 10 Dutch rabbits. Each rabbit was randomized to treatment groups using topical prednisolone acetate, 5-fluorouracil, heparin, prednisolone and heparin, or prednisolone and 5-fluorouracil. Topical agents were instilled twice daily for 2 weeks. Corneal stromal haze developed in all of the eyes. At 2 weeks, there was a significant difference between the degree of haze in the treated eyes and in the untreated controls (P = .02). At 6 weeks, no significant difference remained (P = .07). There were no significant differences in corneal haze among the treatment groups. Thus, all treatments reduced haze at 2 weeks, but the effect was transient, with controls clearing to an equivalent haze by 6 weeks. We conclude that the agents investigated in this rabbit model provided only a transient benefit in reducing corneal haze following excimer laser photoablation.

Transscleral fixation of posterior chamber intraocular lenses in the absence of capsular support.

We present results obtained by transscleral ciliary sulcus fixation of posterior chamber intraocular lenses in secondary implantation, lens exchange, and in primary implantation of transsclerally fixated lenses during complicated cataract extraction. Follow-up data on 38 patients, 17 of whom have been followed for more than 12 months, are included. We conclude that the procedure is safe, effective, and predictable.

Further studies of four incision radial keratotomy.

This investigation evaluated the results of radial keratotomy on 52 eyes in 30 patients; 32 eyes had follow-up of greater than one year. The spherical equivalent refraction for 91% of these patients was within 1 diopter of emmetropia. We have followed five eyes between one and two to three years after surgery, observing a continued effect of the surgery with a mean gain in the hyperopic direction of +0.72 diopters. Initial overcorrections must be avoided in radial keratotomy.

Epikeratophakia: technique modifications and visual results compared to the national study.

Twenty-eight epikeratophakia procedures have been performed at the University of Minnesota since December 1985. This report describes several technique modifications and compares the refractive and visual outcome of these cases with the national results. There have been 17 aphakic cases (13 adult and four pediatric), seven myopic procedures, and four keratoconus cases. Of the adult aphakic cases, 80% were within 3 diopters of emmetropia at six months, with four cases showing an undercorrection. In the myopic group, five cases showed an overcorrection at six months and all patients were within two Snellen lines or better than their preoperative best corrected vision. The major complications included one graft removal for failure to epithelialize, an interface hematoma, and a severe overcorrection to +9.37 diopters in a myopic patient. A no-keratectomy technique was used in the aphakic and myopic groups. A variation on centering the Hessburg-Barron trephine and removing the epithelium was performed and allowed for more accurate trephine placement.

Visual results following vitreous loss and primary lens implantation.

Implantation of an intraocular lens following vitreous loss at cataract surgery is a controversial decision. To address this issue, we retrospectively identified all cases performed at the University of Minnesota in the last three years that had either a posterior or an anterior chamber lens placed following anterior vitrectomy. Twenty patients had a posterior chamber lens implant; 14 had follow-up longer than six months. All these patients achieved 20/40 or better visual acuity, although one patient had a retinal detachment. Of the six patients with an anterior chamber lens implant, four achieved 20/40 or better acuity and two achieved 20/50 acuity with follow-up of six months; one patient had a retinal detachment. This review demonstrates that with a meticulous anterior vitrectomy, good visual results can be achieved, although the risk of retinal detachment is higher than in uncomplicated cases.

Implantation of a posterior chamber lens without capsular support during penetrating keratoplasty or as a secondary lens implant.

We have devised a technique to fixate a posterior chamber lens in the ciliary sulcus when no posterior capsular support exists. Our short-term follow-up of 22 eyes with lenses thus fixated has shown these eyes to be quiet and to have good pupillary motility after at least 3 months. We believe this new technique is a significant advancement in corneal and anterior segment surgery.

The surgical management of overcorrection in myopic epikeratophakia.

Three patients underwent myopic epikeratophakia that resulted in overcorrection. The surgical management of these cases involved resuturing the myopic lenticule to flatten the peripheral curvature and reduce the amount of minus power. A reduction in the overcorrection was achieved in all cases.

Complications of Nadbath facial nerve block and a review of the literature.

In a retrospective study of complications resulting from the Nadbath facial nerve block, we identified three patients (0.25%) over a 2-year period. Complications included dysphonia, laryngospasm, unilateral vocal cord paralysis, and a sensation of the inability to breathe. As it exits the stylomastoid foramen, the facial nerve lies close to the vagus, glossopharyngeal, and accessory nerves. Particular care must be taken, therefore, when giving Nadbath blocks in very thin individuals. The use of hyaluronidase, which enhances effusion of the anesthetic agent, should probably be withheld.

Four incision radial keratotomy.

Radial keratotomy is a constantly evolving procedure. This paper investigates the value of four incision radial keratotomy. The possible advantages of fewer incisions include increased corneal stability, lower risk of perforation, less potential of endothelial cell loss, decreased chance of overcorrection, and simplification of the procedure. We evaluated the results of four incision radial keratotomy in 55 eyes of 31 patients. Follow-up ranged from one to 18 months. Results in low myopia (-2.00 to -3.12 diopters) show 93% of the patients were 20/40 or better, 90% were within +/- 1 diopter of emmetropia, and no patients were overcorrected greater than 1 diopter. In moderate myopia (-3.25 to -4.37 diopters), 84% of the patients were 20/40 or better, 92% were within +/- 1 diopter of emmetropia, and no patients were overcorrected greater than 1 diopter. Regression analysis was performed and it was determined that the postoperative result was equal to .262 + [1.293 x preop spherical equivalent] - [1.166 x optical zone] + [0.56 x depth] + [.038 x age], R = .87.

Visual loss following suture removal postkeratoplasty.

Suture removal following penetrating keratoplasty continues to plague surgeons as one of the most unpredictable aspects of this procedure. The patients presented here will detail three cases of endophthalmitis and one case of expulsive hemorrhage following suture removal. These events cannot be predicted. However, certain steps can be taken to minimize these potentially blinding complications. These steps include avoidance of through and through sutures, follow-up examination within 24 h of suture removal to look for signs of would leak, graft dehiscence or infection, use of appropriate antibiotics, elimination of dacryocystitis prior to keratoplasty, and particular vigilance in immunocompromised patients.

Application of homologous fibronectin to persistent human corneal epithelial defects.

Six eyes with persistent corneal epithelial defects of various etiologies were treated in a randomized, prospective, double-masked study to evaluate the effect of fibronectin on corneal epithelial wound healing. Study eyes received homologous human fibronectin (300 micrograms/ml), mixed with gentamicin and artificial tears, 4 times a day. Control eyes received the mixture of gentamicin and artificial tears. If no healing occurred after 2 weeks, the drug was unmasked and where control drops had been given, the mixture containing fibronectin was administered in open-label fashion. All 4 eyes in diabetic patients had successful epithelial healing when treated with the fibronectin solution. The 2 remaining corneas, which had defects secondary to a thermal injury and a presumed infectious etiology, did not heal with fibronectin.

Fibronectin in alkali burns of the rabbit cornea.

Alkali burns of the cornea were made bilaterally in 16 albino rabbits. The eyes were then treated four times a day in a masked fashion with a solution either of fibronectin (250 micrograms/ml) plus gentamicin (1.5 mg/ml) or of gentamicin (1.5 mg/ml) plus hydroxypropyl methylcellulose (Tears Naturale). The eyes were examined daily in a masked manner for evidence of a corneal epithelial defect. On days 6-14, the fibronectin-treated eyes had more healed corneal defects (p less than 0.05, McNemar's test for matched pairs) than the control eyes. Fibronectin aided the healing of corneal alkali burns by decreasing the peeling back of the healing epithelium and by allowing re-epithelialization if peeling back had occurred. These properties of fibronectin helped to preserve a stable, intact corneal surface.