Repair of Descemet's membrane detachment with the assistance of intraoperative ultrasound biomicroscopy.

PURPOSE: To evaluate the ability of ultrasound biomicroscopy to monitor the repair of large Descemet's membrane detachments. METHODS: Intraoperative ultrasound biomicroscopy was performed in two patients who had undergone previous unsuccessful surgical repair of large Descemet's membrane detachments. RESULTS: Ultrasound biomicroscopy visualized and located Descemet's membrane detachment and verified proper suture placement and membrane repositioning. CONCLUSIONS: Ultrasound biomicroscopy is a useful tool to guide surgical repair of Descemet's membrane detachments, particularly when hazy media prevent satisfactory visualization.

Wound healing following intrastromal photorefractive keratectomy with the Nd:YLF picosecond laser in the cat.

BACKGROUND: We studied the histopathology of the stromal wound healing response in the cat cornea following intrastromal photorefractive keratectomy (IPRK) with the Nd:YLF picosecond laser. METHODS: Intrastromal PRK was performed in the anterior stroma of cat corneas with the Nd:YLF picosecond laser. The cats were sacrificed at predetermined intervals ranging from immediately to 6 months postoperatively. Effects of the laser treatment on the epithelium, Bowman's layer, stroma, and the endothelium were evaluated using light and scanning electron microscopy. No anti-inflammatory agents were used. RESULTS: Intrastromal PRK resulted in no perceptible damage to the corneal epithelium or Bowman's layer either acutely or at 6 months. The corneal stroma showed multiple cavitations immediately after intrastromal PRK, which collapsed over several hours, followed by thinning of the cornea over 2 weeks. At 1 month, the stromal collagen was abnormal with surrounding hypercellularity. The endothelium showed no injury, acutely or at 6 months. No thermal effects on stromal collagen were observed at 6 months, and disruption of the lamellar pattern was not apparent after the cavitation bubbles were reabsorbed. CONCLUSION: Intrastromal PRK can effectively remove stromal tissue without acute damage to the adjacent lamellae, epithelium, or endothelium. There is a transient cellular wound healing response associated with a transient stromal collagen abnormality at 2 weeks to 1 month, which was not apparent 2 months after the procedure.

Ultrasound biomicroscopy of intrastromal photorefractive keratectomy with the Nd:YLF picosecond laser.

PURPOSE: To evaluate corneal morphology in vivo following intrastromal photorefractive keratectomy (IPRK) with the Nd:YLF picosecond laser, using the ultrasound biomicroscope. MATERIALS AND METHODS: Myopic intrastromal PRK was performed in the anterior stroma of cat corneas with the neodymium:yttrium lithium fluoride (Nd:YLF) picosecond laser. Periodic examination of the treated corneas up to 6 months postoperative was performed with high resolution ultrasound biomicroscopy. Corneal thickness, depth of the laser patterns from the corneal surface, alignment of the laser treatment, extent of stromal opacification until resolution, and contour of the corneal surface were measured with the ultrasound biomicroscope throughout follow up. RESULTS: The treated corneas were thickened on ultrasonic biomicroscopy measurement immediately after intrastromal PRK and revealed a densely echogenic shadow parallel to the corneal surface at the treatment site. There was increased stromal echogenicity denoting mild edema. The echoes decreased over time and appeared thinner at 2 months compared to the preoperative and immediate postoperative measurements. At 6-month follow up, the treated corneas were echolucent on ultrasonic biomicroscopy. CONCLUSION: The ultrasound biomicroscope might become a helpful tool in assessing accuracy of treatment parameters of intrastromal PRK as well as in monitoring the response of the cornea to treatment.

Mass spectrometry analysis of the by-products of intrastromal photorefractive keratectomy.

BACKGROUND AND OBJECTIVE: To determine the nature and chemical composition of the cavitation bubbles generated by intrastromal photorefractive keratectomy (IPRK) with the Neodymium: Yttrium Lithium Fluoride (Nd:YLF) picosecond laser. MATERIALS AND METHODS: IPRK was performed on the corneas of three fresh human cadaver eyes with the Nd:YLF picosecond laser. High energy levels of 200 mJ/pulse to 300 mJ/pulse were used to produce the maximum amount of gas within the corneal stroma. The cavitation bubbles produced in the stroma were aspirated using a gas-tight syringe connected to a valve, and the specimens were analyzed with a mass spectrometer. RESULTS: The experiment was performed on three different occasions using one cadaver eye in each experiment. The analysis consistently revealed a mixture of carbon dioxide, carbon monoxide, water vapor, oxygen, and nitrogen. Atmospheric control samples also revealed oxygen and nitrogen. No other components were detected. CONCLUSION: The gaseous by-products of IPRK with the picosecond laser result from the simple breakdown of stromal tissue and contain no toxic or unexpected components. We found that these gaseous products are capable of rapid elimination by absorption or diffusion out of the intact cornea.

Myopic intrastromal photorefractive keratectomy with the neodymium-yttrium lithium fluoride picosecond laser in the cat cornea.

OBJECTIVE: To evaluate the refractive effects of myopic intrastromal photorefractive keratectomy (IPRK) with the neodymium-yttrium lithium fluoride (Nd-YLF) picosecond laser. METHODS: A 1053-nm Nd-YLF picosecond laser was used to produce myopic IPRK in cat corneas at threshold energy densities. Preoperative corneal topography and ultrasonic pachymetry were performed followed by IPRK in one eye each of 21 cats. No anti-inflammatory medications were administered. Postoperative corneal topography, ultrasonic pachymetry, and slit-lamp examination were performed at scheduled intervals. RESULTS: An average topographic flattening of 11.4 diopters and pachymetric thinning of 50 microns at the center of the treatment zone were observed by 6 weeks following treatment. The average diameter of the zone of flattening was 5.1 mm at 6 weeks and 6.0 mm at 12 weeks postoperatively. At 6 months postoperatively, the average central corneal power was unchanged, while the average central thickness had returned to the preoperative value. A mild subepithelial haze was detected at 1 month following IPRK, which was barely perceptible at the second through sixth months. Regression of the topographic effects of PRK was not observed. CONCLUSION: Intrastromal PRK with the Nd-YLF picosecond laser produces central flattening of the cat cornea with barely perceptible stromal haze and no regression of topographic effect after 6 months in the absence of treatment with anti-inflammatory agents.

High-resolution ultrasound biomicroscopy of the anterior segment in patients with dense corneal scars.

Preoperative evaluation and surgical planning for penetrating keratoplasty in patients with dense corneal scars is often difficult because of poor visualization of the anterior segment. We performed ultrasound biomicroscopy (50-megahertz frequency, 50-micron resolution) on five eyes of five patients with dense corneal opacities of different etiologies to evaluate the anatomic relationships of the iris, lens, angle, and ciliary body. Corneal thickness, the presence or absence of iridocorneal adhesions, peripheral anterior synechiae, and cyclitic membranes, intraocular lens position, and relationships among intraocular structures could be evaluated in vivo. Ultrasound biomicroscopy is the optimal method of obtaining reliable, high-resolution images delineating anatomic relationships and pathology in the anterior segment. This information aids in surgical planning for penetrating keratoplasty and anterior segment reconstruction.

Influence of haptic materials on the adherence of staphylococci to intraocular lenses.

A recent case-control study indicated that the insertion of an intraocular lens with polypropylene (Prolene) haptic materials was a significant risk factor for postoperative endophthalmitis (odds ratio = 4.5, P < .01). In the present study, we used quantitative techniques to evaluate adherence of Staphylococcus epidermidis to two intraocular lens types--lenses with polypropylene haptic materials and all-polymethyl methacrylate optic and three-piece all-polymethyl methacrylate lenses--using a quantitative culture method, a radioisotope technique, and scanning electron microscopy. All three methods demonstrated approximately twice as many bacteria adherent to lenses with polypropylene haptic materials as to all-polymethyl methacrylate lenses. Scanning electron microscopy showed preferential bacterial adherence to the polypropylene haptic materials. These data provide a pathogenic mechanism to explain our epidemiologic findings of an increased risk of postoperative endophthalmitis associated with implantation of intraocular lenses with polypropylene haptic materials.

Blepharitis.

Blepharitis is an acute or chronic inflammatory process involving the eyelids that is frequently associated with conjunctivitis. In its many clinical forms, blepharitis is one of the most common diseases seen by ophthalmologists; yet it remains a diagnostic and therapeutic challenge. This article reviews the clinical presentation, classification, diagnosis, etiology and pathogenesis, and treatment of blepharitis.

Serious complications of topical mitomycin-C after pterygium surgery.

BACKGROUND: The use of topical mitomycin (mitomycin-C) as a medical adjunct to pterygium and glaucoma surgery is increasing. METHODS: The authors report on a series of 10 patients who experienced serious, vision-threatening complications associated with the use of this drug after pterygium surgery. RESULTS: Complications included severe secondary glaucoma (4 patients), corneal edema (3 patients), corneal perforation (1 patient), corectopia (2 patients), iritis (8 patients), sudden onset mature cataract (2 patients), scleral calcification (1 patient) and incapacitating photophobia and pain (8 patients). Two patients required penetrating keratoplasties and a third required three lamellar keratoplasties. Another patient underwent four additional surgeries including a conjunctival Z-plasty, scleral patch grafting, and conjunctival autografting before his intractable pain and photophobia resolved 15 months after the original surgery. Because of these complications, 6 patients required a total of 20 return visits to the operating room after their original pterygium surgery. In 5 eyes, visual acuity remained at 20/200 or less. Three of the six patients with the most severe complications had concomitant chronic external diseases (rosacea [3 patients], ichthyosis [1 patient], keratitis sicca [1 patient]). CONCLUSION: The authors urge extreme caution in the use of mitomycin. If mitomycin is used, the lowest possible concentration should be applied for the shortest time period in an effort to avoid these complications. A prospective multicenter study of the ophthalmic use of this medication is needed.

The collagen shield as a collagenase inhibitor and clinical indicator of collagenase activity on the ocular surface.

Collagen shields applied to the corneas of patients with bacterial keratitis degrade rapidly, often within a few hours. Once treatment brings the infection under control, subsequently applied collagen shields degrade more slowly. In vitro models were established to evaluate the significance of these observations. Twenty-four and 72-hour collagen shields were incubated with collagenase from Clostridium histolyticum. The in vitro rate of digestion of the shields was directly proportional to the concentration of collagenase, with the rate of digestion of the 24-hour shields being greater than that of the 72-hour shields. Therefore, the rate of collagen shield degradation may be a clinically useful index of collagenase activity on the ocular surface. Ultrastructural studies of collagen shields from patients with acute bacterial keratitis revealed irregular degradation of shield matrix with no evidence of adherence of microorganisms or inflammatory cells. Co-incubation of deepithelialized rabbit corneas and collagen shields resulted in inhibition of the digestion of the rabbit corneas when the weight:weight ratio of collagen shield:rabbit cornea was increased to greater than or equal to 2:1. Collagen shields may inhibit corneal collagen degradation in infectious ulceration and melting disorders by effectively competing for collagenase on the ocular surface.

A case-control study of risk factors for postoperative endophthalmitis.

The authors conducted a case-control study to identify risk factors for postoperative endophthalmitis. Fifty-four cases of patients who developed endophthalmitis after intraocular surgery at the New York Eye and Ear Infirmary during the period from January 1988 through October 1990 were identified. A control group of 228 patients was randomly selected from the 24,105 patients who underwent intraocular surgery during this same period. Logistic regression analysis identified significant independent risks associated with intraoperative communication with the vitreous cavity (risk ratio 13.7, P less than 0.001) and use of an intraocular lens with haptics made of polypropylene (risk ratio 4.5, P = 0.007). The study predicts that there would be approximately 700 fewer cases of postoperative endophthalmitis annually in the United States (approximately a 50% decrease in incidence) if intraocular lenses with haptics made of polymethyl-methacrylate, rather than polypropylene, were used exclusively.

Prophylaxis of endophthalmitis with topical povidone-iodine.

The authors conducted an open-label nonrandomized parallel trial to examine whether the preoperative application of povidone-iodine to the ocular surface reduces the incidence of endophthalmitis after intraocular surgery. During an 11-month period, topical 5% povidone-iodine was used to prepare the conjunctiva in 1 set of 5 operating rooms, while silver protein solution was used in another set of 5 rooms. In all cases, surgeons continued to use their customary prophylactic antibiotics. A significantly lower incidence of culture-positive endophthalmitis (P less than 0.03) was observed in the operating rooms using povidone-iodine (2 of 3489 or 0.06%) compared with those using silver protein solution (11 of 4594 or 0.24%). Use of topical povidone-iodine in over 3000 cases was not associated with any adverse reactions. In a majority of the observed cases of endophthalmitis, some form of intraoperative communication with the vitreous cavity existed.

Effect of gas-permeable contact lenses on the endothelium of corneal transplants.

The effects of gas-permeable contact lens wear on the density and morphologic characteristics of corneal endothelial cells were prospectively studied by wide-field specular microscopy in 18 eyes that had undergone keratoplasty at least 14 months previously. Daily-wear rigid gas-permeable lenses were fitted to allow as much movement and tear exchange as possible. There was no evidence of morphologic instability of the endothelial cells during the course of the study, with a mean duration of lens wear of 9.8 months. Although there is concern over adverse effects associated with polymethylmethacrylate contact lens wear, this study suggests that the endothelium of a corneal transplant tolerates rigid gas-permeable lens wear without adverse effect during a limited period of follow-up.

Role of external bacterial flora in the pathogenesis of acute postoperative endophthalmitis.

The source of infecting bacteria is often unknown in postoperative endophthalmitis. Using techniques of molecular epidemiology, the authors demonstrate that an organism isolated from the vitreous was genetically indistinguishable from an isolate recovered from the patient's eyelid, conjunctiva, or nose in 14 (82%) of 17 cases of endophthalmitis. In two cases of Staphylococcus epidermidis endophthalmitis, after cataract surgery was performed by the same surgeon on the same day, genetic analysis demonstrated that the infecting organisms from the two patients' vitreous were distinct, and, furthermore, that in each case the external isolates were indistinguishable from the vitreous isolate. The results implicate the patients' external tissues as the source of the infecting organism in those cases of acute postoperative endophthalmitis studied. Therefore, attention should be directed toward the external tissues and their microbial flora in the prophylaxis and prevention of postoperative bacterial endophthalmitis.

A case-control study of risk factors for intraoperative suprachoroidal expulsive hemorrhage.

The authors performed a case-control study of risk factors for suprachoroidal expulsive hemorrhage (SEH); the study involved 68 SEH cases at their institution from 1981 to 1986. The authors examined 113 variables in the study group and a procedure-matched control group of 217 patients randomly selected from the 35,459 patients who underwent intraocular surgery during this period, and subjected them to bivariate and conditional logistic regression analysis. The incidence of SEH was 0.19% overall, 0.16% for lens-related procedures, 0.15% for glaucoma surgery, 0.41% for retinal and vitreous procedures, and 0.56% for keratoplasty. Statistically significant risk factors for SEH in age-adjusted bivariate analyses included: glaucoma (P less than 0.0001), increased axial length (P less than 0.0001), elevated intraocular pressure (IOP) (P less than 0.0001), generalized atherosclerosis (P = 0.007), and elevated intraoperative pulse (P = 0.0001). Conditional logistic regression analysis with frequency matching on age identified significant independent risks associated with a history of glaucoma, elevated IOP, increased axial length, and intraoperative tachycardia. One of the models predicts a 752-fold increased theoretical relative risk of SEH for a patient with axial length greater than or equal to 25.8 mm, a history of glaucoma, preoperative IOP greater than 18 mmHg, and intraoperative pulse greater than or equal to 85 beats per minute. The visual outcome after SEH was best in cases of extracapsular cataract extraction (ECCE), compared with other procedures. Results suggest that attention to multiple preoperative and intraoperative ocular and systemic variables may allow identification and prophylaxis of patients at risk for SEH.

Computerized preparation of a scientific poster.

We prepared an attractive and effective poster using a Macintosh computer and Laserwriter and Imagewriter II printers. The advantages of preparing the poster in this fashion were increased control of the final product, decreased cost, and a sense of artistic satisfaction. Although we employed only the above mentioned computer, the desktop publishing techniques described can be used with other systems.

Penetrating keratoplasty for pseudophakic bullous keratopathy. Management of the intraocular lens.

Management of the intraocular lens (IOL) at the time of penetrating keratoplasty (PK) for pseudophakic bullous keratopathy has been based on lens-related factors and coexisting anterior segment abnormalities. The authors reviewed the results of PK for 102 cases of pseudophakic bullous keratopathy (43 anterior chamber, 50 iris-supported, and 9 posterior chamber) with respect to: (1) the type of IOL, (2) coexisting abnormalities, and (3) management of the IOL at surgery. Graft failure after 2 years of follow-up was: (1) retained iris-supported IOLs, 9%; (2) retained anterior chamber IOLs, 60%; (3) retained posterior chamber intraocular lenses (PC IOL), 0%; (4) removed IOLs, 9%; and (5) exchanged IOLs, 20%. After 5 years of follow-up, 13 of 13 PKs with retained closed-loop anterior chamber IOLs had failed. Visual results were best in eyes with retained iris-supported, rigid anterior chamber or PC IOLs and when the IOL was removed without replacement. The authors recommend that closed-loop anterior chamber lenses and unstable lenses of any type be removed or exchanged and that well-fixated PC IOLs and iris-clip IOLs be retained at the time of PK for pseudophakic bullous keratopathy.