Respirable particles in the excimer laser plume.

PURPOSE: To determine whether respirable-size particles are present in the excimer laser plume following ablation of the corneal stroma. SETTING: Outpatient laser vision correction facility. METHODS: In this experimental study, an excimer laser was used to ablate 2 eye-bank corneas. Material from the plume was collected with filter paper that was coupled to a smoke evacuator. The filter paper was examined and photographed with an electron microscope. The particle size was measured with a computer program using digitized images of the photographs. As a control, room air was sampled using a smoke evacuator connected to a holder containing filter paper prior to the tissue ablation. RESULTS: Ninety-eight particles were measured. The mean diameter was 0.22 microm +/- 0.056 (SD). No particles were seen on the control filter paper. CONCLUSIONS: The plume created during excimer laser ablation of the cornea contained respirable-size particles. It is not known whether inhalation of these particles poses a significant health hazard. However, we recommend that a mask be worn by the surgeon and technical personnel assisting in excimer laser surgery. The plume should also be evacuated.

Hyperopic laser in situ keratomileusis to treat overcorrected myopic LASIK.

PURPOSE: To evaluate the safety and efficacy of hyperopic laser in situ keratomileusis (LASIK) in treating hyperopia caused by overcorrected myopic LASIK and to evaluate a new technique to place the hyperopic treatment after lifting the initial myopic flap. SETTING: Open-access outpatient excimer laser surgical facility. METHODS: A retrospective analysis was performed of 54 eyes in 47 patients who had spherical hyperopic LASIK by 21 surgeons for the treatment of significant hyperopia after overcorrected LASIK for myopia. In 42 eyes, the initial LASIK flaps were lifted and in 12 eyes, new flaps were cut. The mean age of the 25 men (53%) and 22 women (47%) was 48.2 years +/- 8.4 (SD). Outcome measures included refractive error, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and complications. The mean follow-up was 2.97 months. RESULTS: In eyes in which postoperative emmetropia was attempted (n = 45), the mean spherical equivalent improved from +1.21 +/- 0.49 diopters (D) preoperatively to -0.38 +/- 0.50 D postoperatively (P <.001). The mean UCVA improved from 20/38.6 +/- 16.3 to 20/27.4 +/- 9.4 (P <.001). At the last follow-up, 69% of eyes were within +/-0.5 D and 96% were within +/-1.0 D of emmetropia; 42% had a UCVA of 20/20 and 96% had a UCVA of 20/40 or better. No eyes lost 2 or more lines of BSCVA. No vision-threatening complications occurred. Results in patients who had initial flaps lifted and those who had new flaps cut were statistically indistinguishable. On average, achieved hyperopic corrections were 18% greater than intended. CONCLUSION: Hyperopic LASIK was safe, predictable, and effective in the treatment of hyperopia caused by overcorrected myopic LASIK. Results were similar whether the original flap was lifted or a new one was cut.

2-Octyl cyanoacrylate medical adhesive in treatment of a corneal perforation.

PURPOSE: To describe a case of successful treatment of a corneal perforation with 2-octyl cyanoacrylate. METHODS: 2-Octyl cyanoacrylate was applied at the slit lamp with topical proparacaine anesthesia to a cornea with an inferior perforation with iris plugging the defect. RESULTS: After application of 2-octyl cyanoacrylate, the anterior chamber was noted to deepen, and visual acuity improved to 20/200. The glue remained intact for more than 6 weeks and eventually fell out. The underlying cornea healed without scarring, vascularization, or thinning. CONCLUSION: We have described a case in which 2-octyl cyanoacrylate was used to treat a corneal perforation with excellent results. Further study of this adhesive will be useful in comparing the effectiveness and safety of 2-octyl cyanoacrylate with that of previously studied adhesives.

Modeling passive mechanical interaction between aqueous humor and iris.

Certain forms of glaucoma are associated with displacement of the iris from its normal contour. We present here a mathematical model of the coupled aqueous humor-iris system that accountsfor the contribution of aqueous humor flow and passive iris deformability to the iris contour. The aqueous humor is modeled as a Newtonian fluid, and the iris is modeled as a linear elastic solid. The resulting coupled equation set is solved by the finite element method with mesh motion in response to iris displacement accomplished by tracking a pseudo-solid overlying the aqueous humor. The model is used to predict the iris contour in healthy and diseased eyes. The results compare favorably with clinical observations, supporting the hypothesis that passive iris deformation can produce the iris contours observed using ultrasound biomicroscopy.

The predictability of corneal flap thickness and tissue laser ablation in laser in situ keratomileusis.

OBJECTIVE: To evaluate the relationship between predicted flap thickness and actual flap thickness and between predicted tissue ablation and actual tissue ablation. DESIGN: Prospective, nonrandomized comparative (self-controlled) trial. PARTICIPANTS: A total of 60 patients (102 eyes) who underwent laser in situ keratomileusis (LASIK). MAIN OUTCOME MEASURES: Subtraction pachymetry was used to determine actual corneal flap thickness and corneal tissue ablation depth. Other measurements included flap diameter and keratometry readings. RESULTS: Actual flap thickness was significantly different (P < 0.0001) from predicted flap thickness. Fifteen eyes had a predicted flap thickness of 160 micrometer and a mean actual flap of 105 micrometer (standard deviation [SD], +/-24. 3 micrometer range, 48-141 micrometer). Sixty-four had a predicted flap of 180 micrometer with an actual flap mean of 125 micrometer (SD, +/-18.5 micrometer range, 82-155 micrometer). Seventeen eyes had a predicted flap of 200 micrometer, with an actual flap mean of 144 micrometer (SD, +/-19.3 micrometer range, 108-187 micrometer). In addition, we found that significantly more tissue (P < 0.0001) was ablated than predicted. Linear regression of the observed ablation on predicted ablation yielded the following relationship: actual ablation = 14.5 + 1.5 (predicted ablation). Neither flap diameter nor flap thickness were found to increase with respect to steeper corneal curvatures. CONCLUSIONS: Actual corneal flap thickness was consistently less than predicted regardless of the depth plate used; actual tissue ablation was consistently greater than predicted tissue ablation for the laser used in this study.

Hidrotic ectodermal dysplasia with corneal involvement.

BACKGROUND: Persons with ectodermal dysplasias classically have defects in hair, teeth, nails, and sweat glands. Other tissues derived from ectoderm may also be involved. Ocular involvement in ectodermal dysplasias primarily occurs in anhidrotic forms. METHODS: We describe a father and son with hidrotic ectodermal dysplasia. RESULTS: Both patients had recurrent corneal epithelial defects from birth, corneal neovascularization, and strabismus. The father had cataracts with crystalline and amorphous inclusions at an early age. Both patients also had alopecia and skin abnormalities. CONCLUSIONS: A father and son with a previously unreported hidrotic ectodermal dysplasia and unusual corneal findings are described.

Live virus survives excimer laser ablation.

OBJECTIVES: To determine whether live virus can withstand excimer laser ablation and pose a possible health hazard to medical personnel. DESIGN: Experimental study. METHODS: Fibroblasts infected with oral polio vaccine virus were ablated with an excimer laser. The plume was collected using a smoke evacuator and bubbled through viral culture media. MAIN OUTCOME MEASURES: The inlet tube from the smoke evacuator was swabbed and cultured for virus. Liquid from the bubble trap was also cultured. RESULTS: Live virus was shown in the material trapped from the laser plume. CONCLUSIONS: Oral polio vaccine virus can survive excimer laser ablation. Whether other more clinically relevant viruses, such as human immunodeficiency virus, can withstand ablation and remain infectious remains to be determined.

Collagen shield delivery of ofloxacin to the human eye.

PURPOSE: To determine the ocular penetration of ofloxacin into the anterior chamber of the human eye when delivered by a presoaked collagen shield. SETTING: University of Colorado School of Medicine, Denver, Colorado. METHODS: This prospective randomized clinical study comprised 31 patients having cataract surgery. Patients were divided into 2 groups: the first received 3 preoperative drops of commercially available topical ofloxacin 0.3% given 10 minutes apart; the second had a collagen shield soaked in the same medication applied to the eye before surgery. Aqueous humor was extracted immediately before surgery for analysis. RESULTS: Mean aqueous concentration was 287 ng/mL +/- 69 (SEM) (range 40 to 1141 ng/mL) in the drops group and 957 +/- 189 ng/mL (range 214 to 2437 ng/mL) in the shield group. The difference was statistically significant (P < .005). The minimum inhibitory concentration (MIC) for selected ocular pathogens is between 500 and 4000 ng/mL. CONCLUSIONS: A collagen shield presoaked in commercially available topical ofloxacin and applied before surgery appears safe. The MICs for many common ocular pathogens were reached or exceeded. Further study is recommended to determine whether this method of infection prophylaxis is an acceptable substitute for subconjunctival injections of antibiotics.

Do intact viral particles survive excimer laser ablation?

OBJECTIVE: To determine if intact and potentially infectious viral particles can withstand excimer laser ablation and possibly pose a health hazard to medical personnel. METHODS: Excimer laser ablation of fibroblasts infected with attenuated varicella-zoster virus was performed. The laser plume was collected for polymerase chain reaction analysis and viral culture. RESULTS: While viral DNA was detected in the material trapped from the laser plume, live virus could not be demonstrated to have survived ablation. CONCLUSIONS: Attenuated varicella-zoster virus does not seem to survive excimer laser ablation. However, we recommend the use of safety precautions such as wearing a mask during the procedure. Further research is necessary to determine if other viruses could possibly remain infectious despite exposure to excimer laser radiation.

Infectious posterior scleritis caused by Pseudallescheria boydii. Clinicopathologic findings.

PURPOSE: The purpose of the study is to describe an unusual case of infectious posterior scleritis after excision of a pterygium. METHODS: The case history of a patient in whom anterior and posterior scleritis developed after excision of a pterygium is reviewed. Histopathologic findings are presented. RESULTS: Pathologic examination results of a scleral biopsy site and the eye showed extensive involvement of the posterior sclera with fungi that on culture grew Pseudallescheria boydii. The development of posterior scleral thickening and intrascleral abscesses gave the clinical impression of autoimmune posterior scleritis or possible tumor. Ultrasonography and computed tomography scan of the eye and orbit proved particularly helpful in following progression of scleral involvement. CONCLUSIONS: Pseudallescheria boydii is capable of causing an infectious posterior scleritis, which can mimic autoimmune posterior scleritis. The use of systemic immunosuppressive agents contributed to this unusual clinical presentation. Progression of posterior scleritis in the face of apparent adequate immunosuppressive therapy always should suggest the possibility of tumor or infection.

Corneal endothelial deposits in patients with cytomegalovirus retinitis.

PURPOSE: We studied six patients with human immunodeficiency virus (HIV) who had cytomegalovirus retinitis and abnormal endothelial deposits in at least one eye, to characterize their corneal endothelial deposits. METHODS: The corneas of the six patients were examined by slit-lamp biomicroscopy and specular microscopy with morphometric analysis. The eyes of one patient with endothelial changes were obtained post mortem for histopathologic and ultrastructural examination. RESULTS: There were multiple diffuse, fine refractile, stellate-shaped deposits on the corneal endothelium in all affected eyes. The deposits were best seen with retroillumination. Two of six patients examined with specular microscopy showed severe abnormalities, which included marked areas of polymegathism and decreased endothelial cell counts. Examination of one eye obtained post mortem disclosed chains of dendritic macrophages and fibrin adherent to the apical surface of the corneal endothelium. There was no evidence of direct infection of the corneal endothelium by cytomegalovirus. CONCLUSIONS: Deposits on the corneal endothelium in patients with cytomegalovirus retinitis most likely result from an anterior uveitis. A preponderance of macrophages observed by histopathologic examination may be related to the inability of the immunodeficient patient to mount a normal T-cell response.

Calcific band keratopathy associated with the use of topical steroid-phosphate preparations.

OBJECTIVE: To report a possible adverse effect of topical steroid-phosphate preparations and to identify factors that may contribute to the development of this effect. DESIGN: The medical records of five patients who developed calcium deposition in the cornea were reviewed and analyzed for possible contributing factors. PATIENTS: Five cases of calcium deposition in the cornea associated with the use of topical steroid-phosphate preparations are described. Scrapings from the cornea and/or specimens obtained at keratoplasty were available in all cases. These cases had the following characteristics in common: use of steroid-phosphate preparations (n = 5); multiple topical drops (n = 5); penetrating keratoplasty (n = 3); presence of epithelial defects (n = 4); history of herpetic stromal keratitis (n = 3) [corrected]; and history of iritis (n = 3). A hypothesis explaining calcium deposition in association with steroid-phosphate preparations is presented. CONCLUSIONS: We recommend withdrawal of steroid-phosphate preparations in patients who develop band keratopathy.