Corneal microsporidiosis. Report of case, including electron microscopic observations.

OBJECTIVE: To report a case of corneal stromal infection caused by a protozoon of the genus MICROSPORIDIA:, including clinical, histopathologic, and electron microscopic observations. DESIGN: Case report. METHODS: Light and electron microscopy studies were performed on keratectomy specimens from a 67-year-old immunocompetent man who had a unilateral chronic stromal keratitis that was refractory to medical treatment. Initial corneal biopsy followed by lamellar and penetrating keratoplasty were performed on the patient. All the specimens were studied histopathologically. RESULTS: Light microscopy of the corneal biopsy and the subsequent keratectomy specimens demonstrated myriad small, round to oval microsporidial organisms measuring 3.5 to 5.0 micrometer in length that stained positively with the periodic acid-Schiff, Grocott-methenamine silver, and acid-fast methods and were gram positive. Electron microscopic observations demonstrated viable blastospores that had a thin osmiophilic outer cell wall and contained 11 to 13 coils of the filament. The light and electron microscopic features, the tinctorial characteristics, and the selective corneal stromal involvement are consistent with microsporidial keratitis. CONCLUSIONS: Microsporidiosis should be considered in the differential diagnosis of a culture-negative stromal keratitis refractory to medical treatment. The diagnosis can be easily established based on the morphologic features of the protozoa in the keratectomy specimens. No effective medical treatment for the stromal disease is available. Full-thickness keratoplasty is suggested because, in our patient, lamellar keratoplasty did not preclude recurrence of the disease.

Fuchs' endothelial dystrophy: a fresh look at an aging disease.

The increasing number or corneal and intraocular surgeries performed together with longer life expectancy, elevates the risk for developing symptomatic Fuchs' endothelial dystrophy (FED). This article reviews the current understanding of FED, and, in addition, a case of early FED is presented clinically and histopathologically. Two FED corneas from one patient were examined histopathologically using an established histological protocol for light and electron microscopy. FED is an inherited autosomal dominant corneal endothelial disorder with incomplete penetrance that is up to 3 times less likely to develop in men. Treatment options are primarily palliative while surgical intervention routinely involves a penetrating keratoplasty. In this disease process the endothelium produces excessive amounts of basement membrane material of an abnormal composition resulting in the formation of a posterior collagenous layer. Extreme accumulations of this material created mushroom-like formations, guttae, projecting into the anterior chamber. The endothelial cells were extremely thinned over the guttae, to the point where the cells may provide little more than barrier function. Despite a presumably compromised endothelial pump the corneas appeared relatively free of edema clinically and histopathologically. However, some edematous pockets deep in the basal epithelial layer were present suggesting that epithelial involvement occurs at an early stage in the disease. An early diagnosis of FED will help patients and surgeons to better elect optimal surgical timing and procedures. The current trend is to intervene surgically before the patient reaches the painful end-stage. Interestingly, in the case examined, the endothelium presumably provided only a barrier function over large areas with an apparently reduced contribution from the endothelial fluid pump and yet the corneas remained relatively clear. Future research may confirm that decompensation occurs only when complete endothelial coverage is lost. If the endothelial barrier function is more important to corneal transparency than the endothelial pump function in FED, then the relative combination of these two functions in the normal cornea should also be reassessed.

Limbal conjunctival autograft in a subacute alkaline corneal burn.

Persistent epithelial defects are a common complication after severe alkaline corneal burns. Chemical damage to the limbal area destroys the stem cells that play a key role in corneal reepithelialization. Limbal conjunctival autograft transplantation has been proposed as a treatment to replace damaged limbal stem cells and promote epithelial healing. We report a case of a persistent epithelial defect after a severe alkaline corneal burn that was successfully treated 6 weeks after the injury with limbal autograft transplantation. Impression cytology provided valuable information for locating the healthy and damaged limbal tissue involved in the transplantation. Two weeks postoperatively the epithelial defect was completely healed, stromal vascularization was regressed, and visual acuity was improved.

Visual improvement as a function of time after lamellar keratoplasty for keratoconus.

Twenty-eight keratoconic patients with either contact-lens intolerance or marked corneal scarring over the visual axis underwent lamellar keratoplasty for visual rehabilitation. All 28 patients returned for follow-up at six months, 27 (98%) had follow-up at one year, and 23 (82%) at two years. The 23 patients with two-year follow-up showed progressive improvement of visual acuity over time. At six months, 11 of 23 patients (48%) had visual acuity of 20/30 or better. At one year, 17 of 23 (74%) had 20/30 or better, and at two years, 21 of 23 (91%) had 20/30 or better. The average postoperative keratometry measurement at two years was 43.5 diopters (S.D. = 2.5 diopters), which represented an average reduction of 13 diopters from preoperative keratometry. All patients who were less than 32 years old obtained visual acuity of 20/30 or better after two years and reached this level significantly (F = 6.75, P = .02) sooner than those more than 32 years old. These results compare favorably with previously reported visual results after penetrating keratoplasty.

Epikeratoplasty with nonlyophilized tissue in children with aphakia.

We studied 75 epikeratoplasty procedures using nonlyophilized tissue performed by eight ophthalmic surgeons in 70 eyes (47 patients) to correct for aphakia in children less than 8 years of age (mean age, 3.4 +/- 2.1 years). Of the 47 patients in the study, 24 were girls and 23 were boys; 23 patients had bilateral surgery. Seven of the epigrafts required removal; two were not replaced, and five underwent successful repeat epikeratoplasty. Overall, the success rate (that is, the percentage of epigrafts that remained optically and functionally clear throughout the course of this study) for the epikeratoplasty procedure was 89% (62 of 70 eyes) for initial surgery and 96% (67 of 70 eyes) for repeat surgery. The average spherical equivalent was +14.4 +/- 3.7 diopters preoperatively and +0.3 +/- 2.9 diopters one year after the operation. One year after the final surgical procedure, 42 of 56 eyes (75%) were within 3 diopters of emmetropia. In the 29 verbal patients, best-corrected visual acuity was 20/100 or better in 25 (86.2%) one year after the operation.

A comparison of penetrating keratoplasty to epikeratoplasty in the surgical management of keratoconus.

Of 40 patients intolerant to contact lenses, 47 eyes with keratoconus were surgically corrected with either epikeratoplasty (N = 31) or penetrating keratoplasty (N = 16). The percentage of eyes in both groups that had visual acuity of 20/40 or better with contact lenses at one year were equal (14 of 15 eyes [93.3%] in the penetrating keratoplasty group; 27 of 29 eyes [93.1%] in the epikeratoplasty group); however, the penetrating keratoplasty procedure resulted in a higher percentage of eyes that had visual acuity of 20/20 than the epikeratoplasty group (11 of 15 eyes [73%] compared with seven of 29 eyes [24.1%], respectively). Both procedures resulted in significant corneal flattening, with the penetrating keratoplasty group producing an average of 3 diopters more keratometric reduction than the epikeratoplasty group one year postoperatively. Although no irreversible graft failures occurred, five of 16 eyes (31%) in the penetrating keratoplasty group had graft reactions. No serious complications were noted in the eyes of the epikeratoplasty group. Both procedures were effective in the surgical management of keratoconus.

One year follow-up of epikeratoplasty for myopia.

Eighteen surgeons performed 166 consecutive epikeratoplasty procedures to correct myopia in 103 patients. Of this total, 147 (89%) were first surgeries and 19 (11%) were repeat surgeries. First surgery patients were divided into three subpopulations based on preoperative spherical equivalents (low -5.00 diopters [D] to -9.49 D, medium -9.50 D to -14.00 D, and high greater than -14.00 D). The percentage of eyes with 20/40 or better best corrected visual acuity before surgery was 93% for the low group, 89% for the medium group, and 57% for the high group. The percentage of eyes with 20/40 or better uncorrected visual acuity at 12 months after surgery was 58% for the low group, 42% for the medium group, and 17% for the high group. The average and median spherical equivalent after one year was -1.40 D (2.45 SD) and -1.00 D, respectively; 41% of the eyes were within one diopter of emmetropia, 65% within two diopters, and 76% within three diopters. Clinically significant regression was only noted in low and medium myope groups under 25 years of age. Repeat surgery outcomes were equivalent to those in first surgery patients who had a single procedure.

Stability of refraction during two years after myopic epikeratoplasty.

A series of 54 consecutive myopic epikeratoplasty procedures was performed by three surgeons between November 1986 and August 1987. To evaluate the stability of the myopic epikeratoplasty procedure, this study was limited to the 33 eyes that had data 24 months after surgery. One year after surgery, 68% (19/28 eyes) had 20/40 or better uncorrected visual acuity and after two years, 57% (17/30 eyes) had 20/40 or better uncorrected visual acuity. Significant loss of surgical effect (increasing myopia) did not occur during the first six postoperative months (r = 0.09, P = NS). This was due to the large amount of variability in spherical equivalent refraction during this interval. However significant regression was detected between 6 and 12 months after surgery (r = 0.27, F = 4.74, P = 0.03). Even though there was further reduction in variability from 12 to 24 months, significant regression was not found (r = 0.07, P = NS). This suggests stabilization of refraction by approximately 12 months for this population.

Epikeratophakia without annular keratectomy.

Nineteen patients (20 eyes) underwent epikeratophakia for correction of high myopia. In contrast to the conventional surgical method utilizing an annular keratectomy, no keratectomy was performed in these patients. The surgical procedure is discussed. Preliminary results (up to six months) indicate that the omission of an annular keratectomy has no effect on graft clarity or viability. The weighted-average percent correction over six months postoperatively was 102%.

Epikeratophakia on pediatric traumatized corneas.

Four children ranging from 4 to 6 years of age with unilateral aphakia and corneal scarring secondary to penetrating injuries were treated with epikeratophakia. One child had undergone a rotational penetrating keratoplasty to displace the corneal scar from the visual axis prior to the epikeratophakia procedure. In all of the cases, nonlyophilized donor tissue was utilized. The procedure was successful in all four cases. The average best corrected postoperative visual acuity was 20/45. These results confirm prior studies suggesting that epikeratophakia can be performed successfully on partially opaque and scarred corneas in pediatric aphakic eyes.

Epikeratophakia following rotational autokeratoplasty in a child.

A 3-year-old child with posttraumatic aphakia and a corneal scar was treated with a rotational penetrating ipsilateral autokeratoplasty followed by epikeratophakia 2 months later. His final best corrected visual acuity was 20/30, with 1.37D of corneal astigmatism. There were no significant operative or postoperative complications.

A lipid peroxidative mechanism for posterior subcapsular cataract formation in the rabbit: a possible model for cataract formation in tapetoretinal diseases.

Posterior subcapsular cataracts developed in rabbits following injection of docosahexenoic acid. Autoxidation of docosahexenoic acid in rabbit vitreous was demonstrated by the formation of malondialdehyde and vitreous fluorescence. The onset of posterior subcapsular cataract formation was temporally correlated with declining levels of vitreous malondialdehyde.

Singlet oxygen as a possible factor in human senile nuclear cataract development.

The effects of photodynamically generated singlet oxygen on lens crystallins were investigated. This highly reactive oxidant can produce in crystallins in vitro the oxidative modifications characteristic of proteins from aging and cataractous lens. Additionally species capable of producing singlet oxygen in the presence of near UV radiation are shown to be present in human lenses. These findings are discussed with respect to a possible role of singlet oxygen in the etiology of human senile nuclear cataracts.