Refractive changes caused by hypoxia after laser in situ keratomileusis surgery.

OBJECTIVE: To determine whether hypoxia induces refractive changes in subjects who have had laser in situ keratomileusis (LASIK) refractive surgery. DESIGN: Prospective paired eye clinical trial. PARTICIPANTS: There were 20 LASIK subjects (40 eyes) and 20 myopic non-LASIK controls (40 eyes). INTERVENTION: Each subject had one eye exposed to ocular surface hypoxia (humidified nitrogen) by use of an airtight goggle system at sea level for 2 hours. The other eye was simultaneously exposed to humidified, compressed air (21% oxygen) with the same airtight goggle system. MAIN OUTCOME MEASURES: Keratometry, cycloplegic refraction, and pachymetry were compared before and after exposure by use of repeated measures analysis of variance. RESULTS: A significant myopic shift (P: < 0.01) occurred in LASIK corneas exposed to hypoxia compared with myopic control subjects. A significant increase in corneal thickening occurred symmetrically in both LASIK and control subjects exposed to hypoxia. There was a trend toward corneal steepening (keratometry) in LASIK subjects, but this was not statistically significant. CONCLUSIONS: These results suggest that ocular surface hypoxia induces a myopic shift in LASIK subjects.

Visual field defect associated with laser in situ keratomileusis.

PURPOSE: To report a case of visual field defect associated with laser in situ keratomileusis. METHODS: Case report. A 28-year-old woman with high myopia (-10D) and a family history of normal tension glaucoma underwent bilateral laser in situ keratomileusis keratorefractive surgery. Preoperatively, both eyes had normal intraocular pressure and visual field. RESULTS: At the first postoperative visit 1 day after apparently uncomplicated laser in situ keratomileusis, the patient reported a scotoma in the right eye. At 3-month follow-up, visual fields revealed the patient had developed a near-superior altitudinal visual field defect in the right eye. The defect did not progress over 1 year of follow-up examinations. CONCLUSION: Increased intraocular pressure associated with the microkeratome vacuum ring used during laser in situ keratomileusis may have precipitated optic nerve head ischemia and visual field defect.

Monocanalicular intubation for dacryostenosis in oculo-auriculo-vertebral dysplasia (hemifacial microsomia) with congenital corneal anesthesia.

PURPOSE: To present a case of oculo-auriculo-vertebral dysplasia associated with corneal anesthesia and ipsilateral dacryostenosis that was successfully treated with monocanalicular lacrimal intubation. METHODS: Case report. RESULTS: Previous neurotrophic corneal ulcers in a child with hemifacial microsomia had become secondarily infected from a stagnant tear lake, resulting in significant corneal scarring and visual loss. A single monocanalicular stent maintained nasolacrimal patency without causing further corneal trauma, despite constant medial gaze because of wide lateral tarsorrhaphy and contralateral occlusion therapy for amblyopia. CONCLUSIONS: Monocanalicular stents may aid the treatment of dacryostenosis in the face of compromised corneal sensation.

Infectious crystalline keratopathy caused by Candida guilliermondii.

PURPOSE: To describe the manifestations of infectious crystalline keratopathy caused by Candida guilliermondii in a corneal transplant performed for pseudophakic bullous keratopathy. METHOD: Case report. RESULTS: Candida guilliermondii was identified as the causative organism of an indolent infectious crystalline keratopathy. Incisional lamellar biopsy provided diagnostic culture and histopathologic results. Histopathology showed aggregates of yeast elements between corneal stromal lamellae, without inflammation. The infection progressed despite a 6-week course of topical amphotericin B and an additional 6-week course of topical and oral fluconazole. Repeat penetrating keratoplasty resulted in clear graft, with no recurrent infection. CONCLUSIONS: Fungal keratopathy should be included in the differential diagnosis of infectious crystalline keratopathy. Numerous Candida species have been isolated in addition to the most common causative bacterial organism, Streptococcus viridans. Candida guilliermondii is yet one more causative agent of infectious crystalline keratopathy. Candida guilliermondii, a rare human pathogen, was resistant to medical therapy in this case.

Juvenile xanthogranuloma of the iris in an adult.

Juvenile xanthogranuloma is a self-limited skin disorder of young children that uncommonly affects the eye. Juvenile xanthogranuloma has been described in adults, but reported intraocular involvement is extremely rare. We report a case of juvenile xanthogranuloma diagnosed in a 25-year-old man who was seen with nontraumatic hyphema and iridocyclitis. Diagnosis was made from a biopsy specimen obtained from a suspicious skin lesion. Topical and systemic steroids, radiation therapy, and finally immunosupression were required to eliminate the iris tumor clinically and resolve the patient's recurrent symptoms.

The etiology of refractive changes at high altitude after radial keratotomy. Hypoxia versus hypobaria.

OBJECTIVE: Refractive changes at high altitude that occur after radial keratotomy (RK) may be caused by hypoxia or hypobaria. DESIGN: A prospective study was performed to evaluate the effects of hypoxia on RK and non-RK corneas. PARTICIPANTS: There were 20 RK and 20 control eyes. INTERVENTION: These eyes were subjected to ocular surface hypoxia using an air-tight goggle system at sea level for 2 hours. MAIN OUTCOME MEASURES: Keratometry, cycloplegic refraction, and pachymetry were evaluated using repeated measures analysis of variance. RESULTS: A significant hyperopic shift (P < 0.0001) and corneal flattening (P < 0.0013) occurred in all subjects with RK compared with those of control subjects. Corneal thickening occurred symmetrically in both groups. CONCLUSIONS: These results suggest that refractive changes in subjects with RK occur at high altitude as a direct result of corneal hypoxia.

Refractive changes during 72-hour exposure to high altitude after refractive surgery.

PURPOSE: The authors prospectively analyzed refractive and pachymetric parameters during exposure to high altitude after radial keratotomy (RK) and photorefractive keratectomy (PRK). METHODS: The authors measured manifest and cycloplegic refraction, keratometry, computed video keratography, and central and peripheral pachymetry in six subjects who have undergone RK (11 eyes), six who have undergone PRK (12 eyes), and nine with myopia (17 eyes) at sea level and on three consecutive days at 14,100 feet. All measurements were repeated 1 week after subjects returned to sea level. RESULTS: Subjects who have undergone RK demonstrated a significant and progressive increase in spherical equivalence (+0.30 +/- 0.50 diopters on day 1 and +1.52 +/- 1.01 diopters on day 3; P < 0.001) and a decrease in keratometry values during exposure to altitude when compared with control subjects with myopia. Healthy subjects and those who have had PRK demonstrated no significant change in refractive error. Pachymetry measurements demonstrated significant peripheral corneal thickening in all three groups (RK, P < 0.004; PRK, P < 0.007; control subjects, P = 0.0006) by day 3 at high altitude. Refraction, keratometry, and pachymetry returned to baseline (P = 1.000) after return to sea level. CONCLUSIONS: Seventy-two-hour exposure to high altitude in subjects who have had RK induces a significant, progressive, and reversible hyperopic shift in refraction with corresponding video keratographic and keratometric changes. The authors hypothesize that the high-altitude hypoxic environment causes increased corneal hydration in the area of the RK incisions, which may lead to central corneal flattening and a hyperopic shift in refractive error. Subjects who have had PRK and those with myopia are not susceptible to this refractive shift. The authors' RK data suggest that the time since surgery and the amount of surgery are related to the degree of hyperopic shift during altitude exposure.

Effects of simulated high altitude on patients who have had radial keratotomy.

BACKGROUND: Previous studies documented diurnal myopic shifts in patients who have had radial keratotomy (RK). Recently, hyperopic shifts in these patients exposed to high altitude have been reported. A direct mechanical effect of reduced barometric pressure on surgically altered corneas has been theorized to cause this hyperopic shift. Another hypothesis implicates the effect of hypobaric hypoxia on the RK incisions. The authors examined the effect of a 6-hour exposure to decreased barometric pressure on 14 normal and 18 RK corneas. METHODS: Cycloplegic refraction, keratometry, corneal pachymetry, and tonometry were performed on seven control subjects and nine patients who have had RK. Measurements were obtained over 8 hours at sea level on day 1 of the study. Measurements were repeated on day 2 which included a 6-hour exposure to 12,000 feet simulated altitude in a hypobaric chamber. Results were compared between subjects and control subjects to determine the effect of a 6-hour exposure to decreased barometric pressure. RESULTS: There was no statistically significant difference in refraction or keratometry readings between control subjects and subjects who have had RK. Central corneal thickness decreased in the afternoon in RK eyes compared with control eyes. There was no clinically significant difference in intraocular pressure between subjects who have had RK and control subjects. CONCLUSIONS: A measurable hyperopic shift in RK corneas exposed to high altitude requires more than 6 hours to develop. A direct effect on corneal shape due to barometric pressure alone should produce a sudden change in refractive error. This study supports the hypothesis that a slow metabolic process is responsible for the previously documented hyperopic shifts induced by altitude. However, a barometric pressure effect requiring more than 6 hours to occur cannot be ruled out with the methodology used in this study.

Comparison of three corneal trephines for use in therapeutic penetrating keratoplasties for large corneal perforations.

Corneas with large perforations complicate penetrating keratoplasty due to the increased risk of anterior chamber collapse they pose. We hypothesize that suction trephines should produce more uniform corneal openings than non-suction trephines. Penetrating keratoplasties using Franceschetti-type freeblades, and Hanna and Hessberg-Barron suction trephines were performed on human eye bank eyes with large corneal perforations. The trephined corneas' histologic appearance was graded according to depth, sharpness, and perpendicularity of cut. Suction trephines were easier to use, resulted in less anterior chamber collapse, caused less corneal distortion, and created a sharper, deeper and more perpendicular incision. The Hessberg-Barron and Hanna trephines performed better than the freeblades in this study.

Refractive corneal surgery with the Draeger rotary microkeratome in human cadaver eyes.

BACKGROUND: Instrumentation for performing a uniform lamellar keratoplasty has been undergoing various stages of refinement. Reliable reproduction and uniform thickness and diameter of lamellar resections is required before lamellar refractive keratoplasty can be considered safe and effective. METHODS: The authors used the Draeger rotary microkeratome with mechanical blade advance for lamellar dissections in 61 human cadaver eyes prepared by injecting Swinger-Kornmehl (SK) solution into the anterior chamber to a pressure of 35 to 40 mm Hg and by soaking for 30 minutes in SK solution. Spacer sizes of 0.25 to 0.40 units were utilized using an anterior lamellar disc diameter estimate between 8.0 and 8.5 mm and a stromal lamellar disc diameter estimate between 5.5 and 6.5 mm. Preoperative pachometry, anterior and stromal lamellar disc thicknesses, and anterior and stromal lamellar disc diameters were measured. RESULTS: The Draeger unit created anterior lamellar thickness between 100 and 268 microns. Stromal lamellar disc thicknesses were consistently between 90 and 161 microns. The continuous, unidirectional, rotary blade and the uniform mechanical advance of the instrument produced a generally uniform bed as evaluated by scanning electron microscopy, although undulations were still present. CONCLUSION: The Draeger microkeratome produced regular lamellar dissections; however, predictability of the thickness of the lenticules varied 10% to 20%, and of the diameter, 1.5% to 15%. Predictability improved with experience. This variability may reduce predictability of refractive outcome.

Combined treatment of Acanthamoeba keratitis with propamidine, neomycin, and polyhexamethylene biguanide.

We developed an intensive treatment regimen of topical neomycin, propamidine, and polyhexamethylene biguanide that was tapered to a maintenance level over a 14- to 28-day period as toxicity developed. Since July 1991, we used this treatment on six eyes of five patients in whom Acanthamoeba keratitis was diagnosed clinically. All patients had positive cultures for microorganisms from their corneas or contact lens cases or had pathognomonic findings of pseudodendritic subepithelial infiltrates and radial keratone-uritis. After therapy, all patients improved within two to four weeks, with regression or resolution of neuritis and infiltrates, healing of epithelial defects, and lessening of pain. By three to four months, visual acuity had returned to 20/20 in all eyes. We believe the addition of polyhexamethylene biguanide to our treatment regimen in Acanthamoeba keratitis dramatically aided and hastened the clinical improvement in five consecutive patients and may, with early diagnosis, increase the number of medical cures.

Peters' anomaly: a review of 26 penetrating keratoplasties in infants.

We reviewed the specimen records log of the McGee Eye Institute Histopathology Service from January 1979 to December 1990 for penetrating keratoplasty specimens submitted with a clinical diagnosis of Peters' anomaly. The records of the 19 cases thereby identified were reviewed for clinical outcome and visual rehabilitation, and the histopathology of all specimens was reviewed and correlated with the clinical diagnosis. Two specimens from the same patient were eliminated as histopathologically inconsistent with Peters' anomaly; one patient's data were not used because the patient was an adult when first grafted. Six eyes were grafted two or more times, for a total of 26 grafts on 16 eyes in 10 patients. Mean age at the time of first transplant was 18 weeks (range, 3 weeks to 40 months). Mean follow up was 30 months (range, 7 months to 6 1/2 years). Five eyes had preoperative glaucoma which persisted postoperatively. Ten eyes developed glaucoma postoperatively. Of the 15 eyes with glaucoma, 14 were uncontrolled medically and 12 underwent cyclodestructive or Molteno filtering procedures, or both, to control pressure. Graft rejection developed in 9 of the 10 eyes that required a cyclodestructive procedure, with partial or complete graft failure occurring shortly after the procedure. Glaucoma did not develop in one eye; in one other eye, it was medically controlled. These 2 eyes maintained clear grafts. Of the 6 eyes that were regrafted, only 1 obtained ambulatory vision. Of the 26 eyes receiving grafts, the grafts failed completely in 17 and partially in 5; 4 have remained clear. Five patients maintain ambulatory vision.

Infectious endophthalmitis following sutureless cataract surgery.

Within the last 6 months, three cases of infectious endophthalmitis following sutureless cataract surgery have been referred to us. Two of these cases followed uncomplicated sutureless phacoemulsification with intraocular lens implantation. One case was complicated by a postoperative hyphema with additional surgery for clot removal 2 days following the initial procedure.

Does neuroretinitis rule out multiple sclerosis?

Neuroretinitis, a form of optic neuritis, is characterized by papillitis and a stellate macular exudate, or "macular star." The star implies the presence of a disc vasculopathy and secondary leakage of lipoproteinaceous material into the macula. Demyelinating optic neuritis would not be expected to produce a secondary macular exudate. We reviewed the literature on the risk of multiple sclerosis developing in a patient after an attack of optic neuritis, and rarely found a comment on the presence of a macular star. We then reviewed two series of 40 patients who had neuroretinitis and added ten patients of our own. Signs of multiple sclerosis had not developed in the 13 patients contacted retrospectively, nor in the patients followed up prospectively. We also noted that in our patients, neuroretinitis may be accompanied by other neurologic manifestations; neuroretinitis may be bilateral and may be staggered; papillitis may present without a macular star, only to have typical exudates develop up to two weeks later; and the macular exudate may take up to 12 months to resolve. We suggest that patients who demonstrate acute papillitis with a normal macula be reevaluated within two weeks for the development of a macular star. Its presence militates strongly against the subsequent development of multiple sclerosis.

Foreign-body giant cell reaction to liquid silicone.

Although intravitreal injections of liquid silicone have long been used in complicated retinal detachments and long-term complications such as keratopathy, glaucoma, and cataract are well-known, the effect of liquid silicone on the retina, iris, and angle structures is not as well defined. Histopathologic study of one human eye that was enucleated 20 months after liquid silicone injection showed an intraocular foreign-body giant cell reaction.