IC3D Classification of Corneal Dystrophies-Edition 3

PURPOSE

The International Committee for the Classification of Corneal Dystrophies (IC3D) was created in 2005 to develop a new classification system integrating current information on phenotype, histopathology, and genetic analysis. This update is the third edition of the IC3D nomenclature.

METHODS

Peer-reviewed publications from 2014 to 2023 were evaluated. The new information was used to update the anatomic classification and each of the 22 standardized templates including the level of evidence for being a corneal dystrophy [from category 1 (most evidence) to category 4 (least evidence)].

RESULTS

Epithelial recurrent erosion dystrophies now include epithelial recurrent erosion dystrophy, category 1 ( COL17A1 mutations, chromosome 10). Signs and symptoms are similar to Franceschetti corneal dystrophy, dystrophia Smolandiensis, and dystrophia Helsinglandica, category 4. Lisch epithelial corneal dystrophy, previously reported as X-linked, has been discovered to be autosomal dominant ( MCOLN1 mutations, chromosome 19). Classic lattice corneal dystrophy (LCD) results from TGFBI R124C mutation. The LCD variant group has over 80 dystrophies with non-R124C TGFBI mutations, amyloid deposition, and often similar phenotypes to classic LCD. We propose a new nomenclature for specific LCD pathogenic variants by appending the mutation using 1-letter amino acid abbreviations to LCD. Pre-Descemet corneal dystrophies include category 1, autosomal dominant, punctiform and polychromatic pre-Descemet corneal dystrophy (PPPCD) ( PRDX3 mutations, chromosome 10). Typically asymptomatic, it can be distinguished phenotypically from pre-Descemet corneal dystrophy, category 4. We include a corneal dystrophy management table.

CONCLUSIONS

The IC3D third edition provides a current summary of corneal dystrophy information. The article is available online at https://corneasociety.org/publications/ic3d .

Novel Application of Conjunctival Anterior Segment Optical Coherence Tomography Angiography to Assess Ocular Redness

PURPOSE

The aim of this study was to determine anterior segment optical coherence tomography angiography (AS-OCTA) parameters to assess ocular redness severity.

METHODS

AS-OCTA analyses of 60 eyes of 40 patients were grouped according to ocular redness stages using the 5-category validated bulbar redness scale in a cross-sectional retrospective study (groups 1-5). A subset of patients with slit-lamp photographs, total 35 eyes of 23 patients, were assessed with 10-category validated bulbar redness scale for comparison. AS-OCTA images of nasal and temporal bulbar conjunctiva were analyzed. Vessel density (VD) represented the blood flow pixels by the total pixels of image (%); vessel diameter index represented the VD by the skeletonized density; fractal dimension, measured with the box-count method, represented the vessel branching complexity. Averaged nasal and temporal parameters for each eye were correlated to validated bulbar redness scales.

RESULTS

There was no statistical difference between groups for age ( P = 0.118), sex ( P = 0.501), eye laterality (OD/OS; P = 0.111), or location (nasal/temporal; P = 0.932). In the 5-category scale, VD significantly increased from group 1 to 2 (31.5 ± 1.9% and 33.4 ± 2.2%, P = 0.023), 2 to 3 (36.0 ± 3.5%, P < 0.001), and 4 to 5 (40.2 ± 2.9 and 46.5 ± 2.8, P < 0.001). The correlations were 0.805 ( P < 0.001) and 0.893 ( P < 0.001) for the 5-category and 10-category scales, respectively. Vessel diameter index showed a significant increase from 1 to 2 (2.90 ± 0.17 and 3.00 ± 0.15; P = 0.004) and 4 to 5 (2.92 ± 0.31 and 3.33 ± 0.08; P = 0.001). The correlations were 0.550 ( P < 0.001) and 0.625 ( P < 0.001) for the respective scales. The fractal dimension showed no significant differences between subsequent groups. The correlations were 0.445 ( P < 0.001) and 0.583 ( P < 0.001), respectively.

CONCLUSIONS

Conjunctival AS-OCTA VD was the most reliable parameter to assess ocular redness.

Comment on "Cornea Classic Article: Kim JC and Tseng SCG: Transplantation of Preserved Amniotic Membrane for Surface Reconstruction in Severely Damaged Rabbit Corneas (Cornea 1995;14:473-484)"

ABSTRACT

Following identification of limbal stem cells, efforts have been devoted to restore and/or replace these essential progenitors of the corneal epithelium. Limbal stem cell deficiency, commonly a consequence of ocular chemical injury, results in clinically compromised vision consequent to corneal conjunctivalization. The insight of Kim and Tseng provided experimental proof of the concept that even in the presence of total limbal stem cell deficiency, amnion membrane overlay grafts can promote limbal recovery as a means of ocular surface reconstruction.

Acute Corneal Transplant Rejection After COVID-19 Vaccination

PURPOSE

The purpose of this report was to describe 4 cases of acute corneal transplant rejection occurring in association with coronavirus disease 2019 (COVID-19) mRNA vaccination.

METHODS

Four patients with prior keratoplasty developed presumed immunologic rejection after the mRNA-1273 vaccination for coronavirus 2 (SARS-CoV-2). Case 1 had received Descemet membrane endothelial keratoplasty 6 months ago and presented with endothelial graft rejection 3 weeks after the first vaccine dose. Case 2 had undergone penetrating keratoplasty 3 years previously and presented with acute endothelial rejection 9 days after the second vaccine dose. Case 3 had prior Descemet stripping automated endothelial keratoplasty (DSAEK) and began experiencing symptoms of endothelial graft rejection 2 weeks after the second vaccine dose. Case 4 presented with endothelial rejection of the penetrating keratoplasty graft 2 weeks after the second vaccine dose.

RESULTS

Frequent topical corticosteroids alone were initiated in all 4 cases. In case 1, the endothelial rejection line appeared fainter with improvement in visual acuity and corneal edema 5 weeks after diagnosis. Case 2 experienced complete resolution of corneal stromal edema and rejection line 6 weeks after diagnosis. Cases 3 and 4 have both experienced initial improvement with steroid treatment as well.

CONCLUSIONS

These cases suggest acute corneal endothelial rejection may occur soon after either dose of the COVID-19 mRNA vaccine. Prompt initiation of aggressive topical steroid therapy may result in complete resolution of clinical signs and symptoms. Further studies are needed to elucidate the causal mechanism of corneal graft rejection after COVID-19 vaccination.

Efficacy of a hinged pupil expansion device in small pupil cataract surgery

Purpose:

To evaluate the efficacy and safety of a hinged pupil expansion device (PED) in eyes with small pupils undergoing phacoemulsification.

Methods:

In this prospective, multicenter, interventional case series of 57 eyes with suboptimal pharmacologic pupil dilation (<5 mm diameter), a hinged PED (I-Ring, Beaver-Visitec International, Waltham, MA) was applied to facilitate surgical visualization during cataract surgery. The pupil diameters (PD) were measured at different stages of the procedure and at the 1-month follow-up visit. Rate of successful intraoperative PED deployment, pupil size, and shape were assessed.

Results:

The mean patient age was 70.5 ± 12.1 years. The I-Ring PED was successfully applied in all eyes. The mean PD at various stages were 4.1 ± 1.1 mm (dilation with eye drops only preoperatively), 4.3 ± 1.1 mm (dilation after intracameral epinephrine and ophthalmic viscoelastic device), 6.80 ± 0.00 mm (with PED applied), and 5.7 ± 1.1 mm (end of surgery). A statistically significant difference (P < 0.001) was observed between the mean PD with intracameral medications and with PED application. Postoperative circular pupil was observed in 54 of 57 eyes (94.7%) and the mean eccentricity index (n = 57 eyes) was 0.11 ± 0.22. No significant adverse events were observed.

Conclusion:

The I-Ring PED safely and effectively provided and maintained adequate pupil expansion and surgical visualization in eyes with small pupils undergoing cataract surgery. Postoperatively 95% of eyes attained circular pupils. This hinged PED is an additional instrumentation option for the safe and effective expansion of inadequately sized pupils during cataract surgery.

Novel Parameters to Assess the Severity of Corneal Neovascularization Using Anterior Segment Optical Coherence Tomography Angiography

PURPOSE

Assessment of anterior segment-optical coherence tomography angiography (AS-OCTA) to determine severity of corneal neovascularization (CoNV).

DESIGN

Retrospective, cross-sectional, single-center study.

METHODS

Patients of various CoNV etiologies were selected and classified into mild, moderate, and severe. Their AS-OCTA images were measured for CoNV anterior limit, CoNV posterior limit, CoNV thickness, CoNV depth%, CoNV vessel density, CoNV area, and CoNV volume. Further, AS-OCTA parameters were correlated to clinical parameters, such as classification, a numerical severity scale, vascular clock hours, and best-corrected visual acuity (BCVA).

RESULTS

A total of 19 mild, 10 moderate, and 6 severe CoNV eyes were included with no significant age-gender differences. CoNV depth% and volume increased from mild to moderate (9.3 ± 1.1% to 17.7 ± 3.3%, P = .030, and 0.2 ± 0.1 mm³ to 1.0 ± 0.3 mm³, P = .025, respectively) and from moderate to severe CoNV (44.6 ± 5.3%, P < .001, and 2.0 ± 0.3 mm³, P = .014, respectively). CoNV area and posterior limit increased from mild to moderate (1.7 ± 0.3 mm² to 4.6 ± 0.7 mm², P = .001, and 217.7 ± 16.8 μm to 349.1 ± 54.9 μm, P = .048, respectively), not from moderate to severe (P = .999 and P = .403, respectively). CoNV thickness increased from moderate to severe (218.2 ± 46.6 μm to 340.2 ± 8.7 μm, P = .020), but not from mild to moderate. CoNV area and volume showed good correlations to CoNV staging (r = 0.703 and r = 0.771, respectively; P < .001) and severity scale (r = 0.794 and r = 0.712, respectively; P < .001). CoNV area showed good correlation to clock hours (r = 0.749, P < .001). CoNV depth and volume showed good correlation to BCVA (r = 0.744 and r = 0.722, respectively; P < .001). CoNV anterior limit and vessel density showed no significant correlations (P ≥ .05).

CONCLUSIONS

Severe CoNV shows greater CoNV posterior limit, thickness, depth%, area, and volume on AS-OCTA compared to mild. CoNV volume and depth strongly correlate to BCVA. AS-OCTA provides novel, quantitative, and noninvasive parameters for assessing CoNV severity.

Modeling Diabetic Corneal Neuropathy in a 3D In Vitro Cornea System

Diabetes mellitus is a disease caused by innate or acquired insulin deficiency, resulting in altered glucose metabolism and high blood glucose levels. Chronic hyperglycemia is linked to development of several ocular pathologies affecting the anterior segment, including diabetic corneal neuropathy and keratopathy, neovascular glaucoma, edema, and cataracts leading to significant visual defects. Due to increasing disease prevalence, related medical care costs, and visual impairment resulting from diabetes, a need has arisen to devise alternative systems to study molecular mechanisms involved in disease onset and progression. In our current study, we applied a novel 3D in vitro model of the human cornea comprising of epithelial, stromal, and neuronal components cultured in silk scaffolds to study the pathological effects of hyperglycemia on development of diabetic corneal neuropathy. Specifically, exposure to sustained levels of high glucose, ranging from 35 mM to 45 mM, were applied to determine concentration-dependent effects on nerve morphology, length and density of axons, and expression of metabolic enzymes involved in glucose metabolism. By comparing these metrics to in vivo studies, we have developed a functional 3D in vitro model for diabetic corneal neuropathy as a means to investigate corneal pathophysiology resulting from prolonged exposure to hyperglycemia.

Colocalization of Galectin-3 With CD147 Is Associated With Increased Gelatinolytic Activity in Ulcerating Human Corneas

Purpose

Galectin-3 is a carbohydrate-binding protein known to promote expression of matrix metalloproteinases, a hallmark of ulceration, through interaction with the extracellular matrix metalloproteinase inducer CD147. The aim of this study was to investigate the distribution of galectin-3 in corneas of patients with ulcerative keratitis and to determine its relationship to CD147 and the presence of gelatinolytic activity.

Methods

This was an observational case series involving donor tissue from 13 patients with active corneal ulceration and 6 control corneas. Fixed-frozen sections of the corneas were processed to localize galectin-3 and CD147 by immunofluorescence microscopy. Gelatinolytic activity was detected by in situ zymography.

Results

Tissue from patients with active corneal ulceration showed a greater galectin-3 immunoreactivity in basal epithelia and stroma compared with controls. Immunofluorescence grading scores revealed increased colocalization of galectin-3 and CD147 in corneal ulcers at the epithelial–stromal junction and within fibroblasts. Quantitative analysis using the Manders' colocalization coefficient demonstrated significant overlap in corneas from patients with ulcerative keratitis (M1 = 0.29; M2 = 0.22) as opposed to control corneas (M1 = 0.01, P < 0.01; M2 = 0.02, P < 0.05). In these experiments, there was a significant positive correlation between the degree of galectin-3 and CD147 colocalization and the presence of gelatinolytic activity.

Conclusions

Our results indicate that concomitant stimulation and colocalization of galectin-3 with CD147 are associated with increased gelatinolytic activity in the actively ulcerating human cornea and suggest a mechanism by which galectin-3 may contribute to the degradation of extracellular matrix proteins during ulceration.

Chemical Burns of the Eye: The Role of Retinal Injury and New Therapeutic Possibilities

PURPOSE

To propose a new treatment paradigm for chemical burns to the eye - in the acute and chronic phases.

METHODS

Recent laboratory and clinical data on the biology and treatment of chemical burns are analyzed.

RESULTS

Corneal blindness from chemical burns can now be successfully treated with a keratoprosthesis, on immediate and intermediate bases. Long term outcomes, however, are hampered by early retinal damage causing glaucoma. New data suggest that rapid diffusion of inflammatory cytokines posteriorly (TNF-α, etc) can severely damage the ganglion cells. Prompt anti-TNF-α treatment is markedly neuroprotective. Long term profound reduction of the intraocular pressure is also vital.

CONCLUSION

A new regimen, in addition to standard treatment, for severe chemical burns is proposed. This involves tumor necrosis factor alpha (TNF-α) inhibition promptly after the accident (primarily for retinal neuroprotection), prophylactic maximal lowering of the intraocular pressure (starting immediately), and keratoprosthesis implantation in a later quiet state.

Limbal autograft transplantation for chemical and thermal burns

The technique of limbal autograft transplantation is presented which has been used in 25 cases of uniocular chemical and thermal burns. With up to 4 years follow-up, these cases have consistently demonstrated: (1) improved visual acuity; (2) rapid surface healing; (3) stable epithelial adhesion without recurrent erosion or persistent epithelial defect; (4) consistent regression of corneal neovascularization; (5) restoration of a smooth and optically improved ocular surface; and (6) probably increased success for subsequent keratoplasty.

Distribution of collagenase and cell types in sterile ulceration of human corneal grafts

Extensive clinical and experimental evidence has suggested a role for corneal epithelium, keratocytes, and acute inflammatory cells in sterile corneal ulceration, although the precise role of these cell types in stromal matrix degradation has not been elucidated. We studied two corneal buttons and two whole corneas from 4 patients with corneal grafts and sterile stromal ulceration. Each cornea was divided into several sections and examined morphologically, while adjacent sections were placed in tissue culture and assayed for collagenase activity against type I collagen. In each case, collagenase activity was present in tissue from ulcerating and nonulcerating areas and, in most regions assayed, exceeded collagenase activity in normal control peripheral donor corneas. Collagenase levels were not always greatest in areas of most advanced ulceration. Although polymorphonuclear leukocytes were extensively present histologically in two cases, one case had a mixed inflammatory cell population at the site of ulceration, and another had only keratocytes (fibroblasts) present in the entire cornea. We conclude that regional differences in collagen degradation are due not only to the presence of collagenase, but also to cellular and humoral activators and inhibitors that determine collagenolytic activity.

Time course of human conjunctival mast cell degranulation in response to compound 48/80

Compound 48/80, a non-immunogenic mast cell degranulatory agent, is known to produce the signs and symptoms of ocular allergy. Maximal mast cell degranulation of human conjunctiva occurred within the first hour after stimulation by a single topical dose of compound 48/80 (20 microliters, 7.5 mg/ml). The average percentage of fully degranulated mast cells in treated specimens (n = 9) was 31% (range 5-60%) versus 6% (range 0-20%) in control specimens (n = 5). Exact correlates of representative granulated, partially degranulated, and fully degranulated mast cells were determined by light and transmission electron microscopy.

Keratopathy of the rabbit cornea following complete eyelid closure

The corneal response to a complete tarsorrhaphy was studied in 46 rabbits for time periods up to 21 days. During the first 7 days of complete eyelid closure corneal thickness increased up to 18.4%, glycogen decreased 32.2%, and lactate rose 27.2%. A steep increase in corneal thickness to 89.8% appeared after 14 days, followed by decreasing values at 21 days, which was concomitant with the formation of extensive vascularized pannus. These results confirm previous findings that the partial pressure of O2 under closed eye conditions is substantially below physiologic requirements, affects endothelial pump capability, and results in major corneal swelling. When silicone contact lenses were fitted immediately before eyelid closure, corneal swelling 2 days after lid closure did not differ from that in eyes without lenses.

Eccentric lamellar keratolimbal grafts harvested with a manually guided microkeratome. Technical report

BACKGROUND

To perform lamellar keratolimbal allograft transplantation in a one-step procedure with a single graft, we investigated the feasibility of harvesting eccentric lamellar keratolimbal grafts from conventionally processed corneoscleral buttons using a manually guided microkeratome in conjunction with an artificial anterior chamber system.

METHODS

We used the Moria LSK-One microkeratome and the automated lamellar therapeutic keratoplasty (ALTK) system (Antony, France). Ten human donor eyes were used to obtain single-piece lamellar keratolimbal grafts. Specimens were processed for light and electron microscopy.

RESULTS

Eccentric keratolimbal grafts could be obtained from all human donor buttons. Grafts include a crescent-shaped limbal and a large corneal portion. No visible damage to the limbal region was discernible.

CONCLUSION

Our data show that the LSK-One microkeratome in conjunction with the ALTK system allows harvesting eccentric keratolimbal grafts from donor corneoscleral buttons.

Clinical profile and early surgical complications in the Cornea Donor Study

PURPOSE

The Cornea Donor Study was designed to investigate the safety and efficacy of older donor corneal tissue compared with younger donor tissue in recipient eyes at moderate risk to the graft from progressive endothelial failure. Baseline patient data, including indications for transplant, intraoperative complication rates, and early postoperative complication rates are described herein.

METHODS

This study was a multicenter prospective, double-masked, controlled clinical trial.

RESULTS

Fuchs dystrophy was the most common indication for corneal transplantation (61%). Intraoperative complications occurred in 33 (3%) patients. A persistent epithelial defect was the most commonly reported postoperative complication, occurring in 92 patients (8%).

CONCLUSION

Intraoperative and postoperative complication rates were low. There was no apparent association between donor or recipient age and either intraoperative or early postoperative complication rates.

Laser in situ keratomileusis outcomes following radial keratotomy, astigmatic keratotomy, photorefractive keratectomy, and penetrating keratoplasty

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) to enhance refractive status following other corneal surgical procedures.

SETTING

Clinical office-based practice.

METHODS

Seventy-one eyes of 57 patients had LASIK for refractive errors following radial keratotomy (n = 22), astigmatic keratotomy (n = 13), photorefractive keratectomy (n = 18), and penetrating keratoplasty (n = 18). A Moria LSK-1 microkeratome was used with a Visx S2 or Wavelight Allegretto excimer laser. Data were acquired by retrospective chart review of all appropriately qualified patients.

RESULTS

The mean preoperative manifest refractive spherical equivalent (MRSE) was -3.93 diopters (D) +/- 2.83 (SD) in myopic eyes and +1.43 +/- 1.79 D in hyperopic eyes. The mean time from the initial corneal surgical procedure to LASIK was 65.0 months. The mean post-LASIK follow-up was 9.40 months (range 1 to 42 months). Postoperatively, the mean MRSE was -0.85 +/- 1.42 D in myopic eyes (P<.0001) and -0.16 +/- 1.09 D in hyperopic eyes (P<.0001). Enhancement by LASIK was required in 14% of eyes.

CONCLUSION

In eyes that have had a variety of previous corneal surgeries, LASIK offers a safe and predictable method for enhancing refractive results.

The Effect of Two Novel Lubricant Eye Drops on Tear Film Lipid Layer Thickness in Subjects With Dry Eye Symptoms

PURPOSE

Because the lipid layer of the tear film is recognized as a critical component in dry eye disease, this study was designed to determine if a single eye drop of either Soothe or Systane produces a significant increase in lipid layer thickness (LLT) for subjects reporting symptoms indicative of dry eyes.

METHODS

A double-blind, internally paired study was performed. A custom-built lipid layer interferometer, enabling characterization of lipid layer interference patterns, was used to quantify baseline LLT (OU) of eligible subjects. Inclusion criteria included: 1) presence of dry eye symptoms and 2) baseline LLT < or =75 nm. Subjects (n = 40) received a single eye drop of Soothe in one eye and a single eye drop of Systane in the contralateral eye. After the instillation of each test drop, LLT was reanalyzed for all subjects.

RESULTS

The mean +/- standard error baseline LLT pre-eye drop instillation was 60.0 +/- 1.8 nm for eyes treated with Soothe and 61.5 +/- 1.8 nm for eyes treated with Systane. These means were not significantly different (p > 0.5). The mean LLT for eyes treated with Soothe increased to 124.4 +/- 4.9 nm (p < 0.0001). The mean LLT for eyes treated with Systane increased to 71.3 +/- 2.6 nm (p < 0.0001). The LLT increase from Soothe was significantly greater than that from Systane (p < 0.0001).

CONCLUSIONS

In subjects with symptoms indicative of dry eye states and LLT < or =75 nm, one eye drop of Soothe more than doubled LLT, a 107% mean increase, whereas Systane increased LLT by 16%.

Ocular manifestations of keratitis– ichthyosis–deafness (KID) syndrome

OBJECTIVE

Keratitis-ichthyosis-deafness (KID) syndrome is a rare congenital ectodermal dysplasia characterized by the association of hyperkeratotic skin lesions, moderate to profound sensorineural hearing loss and vascularizing keratitis. Mutations in the GJB2 gene coding for connexin 26, a component of gap junctions in epithelial cells, have been observed in several KID patients. Variable ocular manifestations of the disease in 3 patients with molecular genetically confirmed KID syndrome are reported.

DESIGN

Retrospective case series.

METHODS

Clinical examination and molecular genetic analysis for mutations in the GJB2 gene were performed in 3 patients with KID syndrome ages 5, 13, and 41 years.

RESULTS

Visual acuity ranged from normal to severe visual loss. The ocular signs included loss of eyebrows and lashes, thickened and keratinized lids, trichiasis, recurrent corneal epithelial defects, superficial and deep corneal stromal vascularization with scarring, keratoconjunctivitis sicca, and, in one patient, presumed limbal insufficiency. Whereas ocular surface integrity could be maintained with artificial tears in one patient, and an epithelial defect healed under conservative treatment in the second patient, multiple surgical procedures including superficial keratectomies, limbal allograft transplantation with systemic immunosuppression, amniotic membrane transplantation, lateral tarsorrhaphies, and lamellar keratoplasty could not preserve useful vision in the third patient.

CONCLUSIONS

KID syndrome may affect the ocular adnexae and surface with variable severity independent of the age of the patient. Lid abnormalities, corneal surface instability, limbal stem cell deficiency with resulting corneal complications, and dry eye are the main ocular manifestations.

Corneal epithelial adhesion abnormalities associated with LASIK

PURPOSE

To assess the clinical characteristics, incidence, and pathologic correlation of corneal epithelial adhesion abnormalities encountered during LASIK.

DESIGN

Prospective noncomparative interventional case series.

PARTICIPANTS

Five hundred consecutive eyes of 268 patients undergoing primary LASIK procedures by one surgeon utilizing the Moria LSK One microkeratome and VISX Star S-2 excimer laser.

METHODS

Corneal epithelial adhesion was assessed immediately preoperatively using a cellulose surgical sponge (adhesion test), and the incidence, extent, and location of epithelial defects occurring during the microkeratome incision of the corneal flap were recorded. Epithelial specimens from 7 corneas requiring debridement of dysadhesive epithelium were examined by transmission electron microscopy.

MAIN OUTCOME MEASURES

The characteristics of the study population (age, gender, contact lens use, relevant ocular surface or systemic disease, refractive error, keratometry, pachymetry) and the microkeratome-related variables (head selection and vacuum level) were compared with the results of the preoperative epithelial adhesion test, the development of intraoperative epithelial effects (size and location), and the postoperative outcome.

RESULTS

Epithelial defects were sustained by 51 corneas (10.2%), and among these, 31 (6.2%) were microdefects and 20 (4.0%) were macrodefects. The adhesion test was positive (indicative of compromised adhesion of epithelium to stroma) in 20 (64.5%) corneas with microdefects, but false negatives (epithelial defect despite negative adhesion test) occurred in 11 cases (35.4%). The adhesion test was positive in 16 (80%) of corneas having macrodefects, with 4 (20%) false negatives. Thus, the overall positive predictive value of the adhesion test was 59%, and the percentage of positive prediction was 92% (Bayes' theorem). Among all other outcome measures assessed, only corneal flap thickness seemed a potential risk factor, as 40 (78.4%) epithelial defects were associated with the creation of a 180- micro m-thick flap, whereas 10 (19.6%) were associated with a 160- micro m-thick flap and only 1 (2%) occurred with a 130- micro m flap. These trends were not, however, statistically significant (P = 0.15, Fisher exact test). Transmission electron microscopy of all epithelial debridement specimens disclosed consistent abnormality of the basement membrane adhesion complex, as thickened and multilaminated basement membrane remained adherent to the intact epithelial sheet.

CONCLUSIONS

: Corneal epithelial dysadhesion and defects occurring in the course of LASIK surgery may be associated with an intrinsic compromise of the basement membrane adhesion complex, as evidenced clinically by the adhesion test and demonstrated pathologically by duplicated basement membrane.

[New automated microkeratome for trepanation of lamellar keratoplasty]

BACKGROUND/PURPOSE

Lamellar keratoplasty is an established therapy of corneal pathologies without endothelial involvement and the lack of endothelial rejection is one of the major advantages compared to penetrating keratoplasty. The major disadvantages of manually prepared lamellar corneal grafts are the limited mechanical and optical quality but the automated lamellar therapeutic keratoplasty system ALTK (MORIA) is intended to overcome these disadvantages. The purpose of this preliminary work is to investigate histologically and in clinical cases, if the ALTK system can achieve this aim.

PATIENTS AND METHODS

Corneas from two human donors were cut with a 300 microns trephine. After fixation, the stromal bed and the excised cup of one specimen were stained with PAS and examined by light microscopy and the other specimen was analyzed by scanning electron microscopy. In addition, follow-up data of two patients who received such a lamellar graft are reported for the first 9 and 7 months postoperation, respectively.

RESULTS

The lamellar cut of homogeneous depth revealed only minor stromal trauma. Both clinical cases demonstrated only minimal interface haze during follow-up. Despite a remarkably clear cornea, visual acuity improved only slowly because the precise lamellar cut tended to partially reproduce any preexisting irregular astigmatism.

CONCLUSIONS

The ALTK system simplifies and standardizes the trephination of lamellar corneal grafts but a longer follow up is necessary with respect to visual development and preservation of a clear graft.

Imaging of posterior chamber phakic intraocular lens by optical coherence tomography

We demonstrate the applicability of optical coherence tomography to visualize the distance between the intraocular lens (IOL) and the lens capsule (lens vault) after implantation of the Staar Collamer posterior phakic IOL, also known as the implantable contact lens (ICL). Maintaining a substantial lens vault may be important to avoid cataract formation, but the lens vault was found to change over time; changes in accommodation and pupil size have also been noted. Optical coherence tomography allows precise assessment of the anatomic relationship between the ICL and the crystalline lens in a noncontact, noninvasive manner, permitting dynamic monitoring of changes in accommodation and pupil size.

Amniotic membrane inlay and overlay grafting for corneal epithelial defects and stromal ulcers

OBJECTIVES

To determine the effect of amniotic membrane transplantation (AMT) on persistent corneal epithelial defects (PEDs) and to compare the efficacy between inlay and overlay techniques.

METHODS

Thirty patients (30 eyes) underwent AMT for PED. The use of AMT was restricted to patients in whom all previous measures, including bandage contact lens and tarsorrhaphy, had failed. The amniotic membrane was placed on the surface of the cornea in overlay (group A) or inlay (group B) fashion.

RESULTS

The PED healed after the first AMT in 21 eyes (70%) within an average of 25.5 days after surgery and recurred in 6 eyes (29%). Among the 22 eyes treated with an overlay AMT (group A), the PED healed after the first AMT in 14 eyes (64%) within an average of 24.5 days and recurred in 4 eyes (29%). Among the 8 eyes treated with an inlay AMT (group B), the PED healed within an average of 27.4 days after AMT, which did not statistically significantly differ from group A (P = .72). The PED healed after the first AMT in 7 eyes (88%) and recurred in 2 (29%) of 7 eyes.

CONCLUSIONS

The AMT can be helpful in the treatment of PED in which all other conventional management has failed. However, the success rate in our study was not as high as that previously reported, and our results showed a high incidence of recurrences of epithelial defects. We did not find any difference between overlay and inlay techniques in terms of healing time and recurrence rate.

Central corneal thickness measurement with a retinal optical coherence tomography device versus standard ultrasonic pachymetry

PURPOSE

To demonstrate the capability of a standard, commercially available optical coherence tomography device (originally designed to measure retinal thickness) to image the human cornea in vivo and to measure central corneal thickness (CCT) in normal and edematous corneas. The intrapatient precision and interpatient variability of this novel application was compared to standard ultrasonic pachymetry. Also, the correlation of both methods was investigated.

METHODS

CCT measurements using optical coherence tomography (OCT) and ultrasonic pachymetry (PACH) were obtained in 36 normal eyes and 16 eyes with corneal edema.

RESULTS

Direct in vivo imaging of the cornea and measurements of CCT by OCT could be performed in all eyes. In normal subjects, CCT(OCT) was 530+/-32 microm and CCT(PACH) was 581+/-34 microm. The two methods showed a highly significant correlation with a standardized regression coefficient of 0.988. The difference between both methods was constant over the range of CCT (mean difference, 49.4+/-5.9 microm). The mean intrapatient SD of CCT measurements was 4.90 microm and 4.96 microm for OCT and PACH, respectively. In patients with corneal edema, mean CCT(OCT) was 601+/-59 microm, and mean CCT(PACH) was 667+/-68 microm. The difference between the two techniques increased slightly with increasing corneal edema (mean difference, 66.9+/-10.9 microm).

CONCLUSION

Imaging of the human cornea can be performed by a standard retinal OCT device, and OCT measurement of CCT shows excellent correlation to values obtained by PACH, giving similar readings separated by a constant difference. In corneal edema, the difference between the two methods is additionally increased, but continues to demonstrate excellent consistency.

Corneal manifestations of X-linked ichthyosis in two brothers

PURPOSE

To report the unusual manifestation of X-linked ichthyosis in two brothers.

METHODS

Leukocyte separation and sterylsulfatase assay are performed to show the deficiency of sterylsulfatase.

RESULTS

Two brothers presented in our clinic with cutaneous alterations consistent with X-linked ichthyosis. Ocular examination disclosed fine, flour-like, punctate, evenly, and diffusely distributed opacities of the posterior corneal stroma, close to Descemet membrane in both patients. In one patient, superficial, small, granular opacities were detected. They were gray in color and seemed to involve the epithelium and the subepithelial and anterior stromal layers. In both patients, the deficiency of sterylsulfatase could be shown and confirmed the diagnosis.

CONCLUSIONS

Flour-like opacities in the posterior stroma have been shown to be a common manifestation of X-linked ichthyosis. Though the underlying biochemical defect in X-linked ichthyosis has been discovered, the question of how these opacities develop is still a subject of debate. Subepithelial stromal keratopathies or epithelial irregularities are uncommon and are rarely described in the literature. The superficial corneal changes seen in one of our patients are unusual and are not similar to those reported by other authors.

Ex vivo phosphorus magnetic resonance spectroscopy on eye bank corneas and corneal metabolic health

BACKGROUND

Since a potential exists for untoward effects on the cornea from the high magnetic fields and radio-frequency energies, and the further manipulation required for phosphorus-31 magnetic resonance spectroscopy (31P-MRS), we determined the effects of this technology on tissues using paired human corneas (n = 4) meeting criteria acceptable for transplantation.

METHODS

Slit-lamp biomicroscopy, pachometry, specular microscopy, and redux fluorophotometry were performed on all corneas. One cornea of each pair was examined (< 30 min) by 31P-MRS. Following 31P-MRS, slit-lamp biomicroscopy, pachometry, and redox fluorophotometry were again performed.

RESULTS

Data tabulated included the 31P energy modulus (1.37 +/- 0.28), the ATP/Pi (2.92 +/- 0.59) and SP/Pi (0.76 +/- 0.04) ratios, and the intracorneal pH (7.24 +/- 0.09).

CONCLUSION

Since there were no significant differences in slit-lamp biomicroscopy, endothelial density and morphometry, cell counts, and pachometric and redox fluorophotometric measurements between corneas of each pair before and after 31P-MRS analysis, it was concluded that there was no detectable metabolic damage secondary to such analysis. This study suggests that MRS analysis of human eye-bank tissues does not damage the cornea metabolically and may provide a practical evaluation of the health of the cornea at the biochemical level.

Non-invasive assessment of the donor corneal endothelium using ocular redox fluorometry

AIMS

To investigate the usefulness of ocular redox fluorometry for evaluating donor corneal endothelial viability.

METHODS

Corneas from 42 recipients of penetrating keratoplasty and four donor corneas were examined by ocular redox fluorometry. Autofluorescence from reduced pyridine nucleotides (PN) and oxidised flavoproteins (Fp) of the human corneal endothelium were measured non-invasively, and the PN/Fp ratio was used as a tissue metabolic indicator. Specular microscopy and electron microscopy were also performed.

RESULTS

Both the quality of specular microscopic image and the PN/Fp ratio were significantly correlated with the degree of corneal endothelial damage determined by histological examination. Corneas with poor specular microscopic image showed significantly decreased PN/Fp ratio compared with corneas with good or fair specular images (p = 0.041 and 0.027, respectively). The PN/Fp ratio increased in corneas with mildly damaged endothelium but decreased in corneas with severely damaged endothelium determined by histological examination. Evaluation of corneal endothelium by combination of specular microscopy and ocular redox fluorometry showed excellent association with that of histopathological examination (p < 0.0001).

CONCLUSION

Ocular redox fluorometry is useful for assessing donor corneal endothelial viability. Combination of ocular redox fluorometry and specular microscopy may increase the ability of donor cornea selection.

Scanning electron microscopy of the early host inflammatory response in experimental Pseudomonas keratitis and contact lens wear

Because contact lens wear causes changes in tear film and corneal metabolism and can render the cornea susceptible to bacterial invasion, we examined the role of contact lens wear in Pseudomonas aeruginosa (P. aeruginosa) keratitis and its relation to the early defense mechanism, specifically whether the acute polymorphonuclear leukocyte (PMN) response is altered by contact lens wear. Thirty-three rabbit eyes were examined in an experimental model for P. aeruginosa keratitis. The development of bacterial invasion and PMN migration into the wound was studied during various time intervals in either the presence or absence of a soft hydrogel contact lens (SCL). Scanning electron microscopy revealed massive PMN accumulation in the P. aeruginosa-inoculated corneas without SCL and some, but distinctively fewer, PMNs in the bacteria-inoculated eyes with SCL. These observations demonstrate that P. aeruginosa inoculation evokes massive PMN reaction and suggests that SCL wear actually delays this early host inflammatory response. Thus, SCL wear seems to act as a barrier for the PMNs that presumably derive from the tear film.

Penetrating keratoplasty and anterior segment reconstruction for severe ocular trauma

The principles for management of acute ocular trauma are also applicable to the subsequent reconstruction of the anterior segment. As with the primary repair of ocular trauma, meticulous anatomical restoration during reconstructive surgery minimizes secondary complications and enhances the visual prognosis. Anterior segment reconstruction may then involve procedures such as stripping of corneal pannus, removal of lens and vitreous remnants, iris and angle reconstruction, intraocular lens implantation, and penetrating keratoplasty. A total of 39 consecutive cases of severe ocular trauma, which had undergone penetrating keratoplasty and anterior segment reconstruction, were evaluated for visual outcome, graft survival, and secondary complications. Post-operatively, 49% of eyes achieved > 20/100 as compared with 10% before surgery, and 72% improved by at least two Snellen lines. In all, 31 (80%) initial keratoplasties remained clear, as did all 4 subsequently regrafted corneas, for an overall keratoplasty success rate of 90%. Elevated intraocular pressure occurred postoperatively in 18 eyes (46%), and among these, 10 of 13 eyes (77%) had preoperative glaucoma, whereas 8 of 26 (31%) did not (P < 0.015). Peripheral anterior synechiae could be anatomically corrected at surgery in 80% of cases (24 of 30 eyes). Thus, despite major trauma and a high prevalence of glaucoma, both the visual and the anatomical improvements were highly satisfactory and without severe complications.

Increased interleukin-1 activity in the injured vitamin A-deficient cornea

Injury to a vitamin A-deficient cornea leads to severe acute inflammation often culminating in ulceration. We report on possible regulatory mechanisms involved in the pathogenesis of corneal inflammation in vitamin A deficiency. Thymocyte comitogenic assay and interleukin (IL)-6 induction in corneal fibroblasts have shown that thermally injured and mechanically abraded vitamin A-deficient rat corneas produce much higher levels of an IL-1-like factor as compared with uninjured or injured, normal control corneas. This was confirmed by antibody capture enzyme immunoassay, which detected high levels of IL-1 alpha and IL-1 beta in injured vitamin A-deficient corneas. To our knowledge this is the first report describing the induction of IL-1 in the vitamin A-deficient cornea by thermal and mechanical injuries. When mechanically injured corneas were screened for chemotactic activity, they were found to contain significantly higher levels of a chemoattractant as compared with similarly injured, normal control corneas. Chemotactic activity [expressed as a percentage of a known chemotactic tripeptide, formyl-methionyl-leucyl-phenylalanine (fMLP), found in medium harvested from vitamin A-deficient corneas] averaged 58.8 +/- 8.9% (SEM) as compared with 12.6 +/- 5.4% in medium conditioned by normal corneas. Checkerboard analysis confirmed that the activity in vitamin A-deficient cornea conditioned medium was chemotactic and not chemokinetic. These results demonstrate a correlation between IL-1 levels and severity of inflammation in the injured vitamin A-deficient rat cornea.

Increased gelatinolytic and caseinolytic activity in the thermally injured, nutritionally compromised rat cornea: detection of a 27-kDa lymphoreticular cell-associated caseinase

This study assesses the impact of various forms of injury on matrix degrading enzymes in nutritionally compromised rat corneas. In vitamin A-deficient (nutritionally compromised) and normal control corneas, in vivo or ex vivo mild mechanical abrasion did not appreciably alter the activity of either the 65-kDa or the 92-kDa gelatinases. In contrast, after thermal injury, while no appreciable change was detected in activity associated with the 65-kDa gelatinase in either vitamin A-deficient or normal control corneas, 92-kDa gelatinolytic activity was consistently higher in corneas from both groups, although activity associated with nutritionally compromised corneas was much higher. In these corneas, thermal injury also induced the expression of two high molecular weight (approximately 130-kDa and 225-kDa) gelatinases and a 27-kDa caseinase. While gelatinases were totally inactivated by inhibitors of metalloproteinases such as 1,10-phenanthroline and Galardin MPI, the 27-kDa caseinase showed considerable susceptibility to a mixture of serine protease inhibitors (aprotinin, dichloro-isocoumarin and pA-PMSF [(4-amidino-phenyl)-methane-sulphonyl fluoride]. Furthermore, unactivated-lymphoreticular cells from either nutritionally compromised or normal control animals contained a 24- and 27-kDa caseinase, however most of the activity was due to the 24-kDa caseinase. In contrast, glycogen-activated lymphoreticular cells contained a preponderance of the 27-kDa caseinase. Activated-lymphoreticular cells also expressed 92-kDa, 130-kDa and 225-kDa gelatinases. The presence of low molecular weight caseinases in lymphoreticular cells implicates them as the source of these enzymes.(ABSTRACT TRUNCATED AT 250 WORDS)

A randomized trial of intraocular lens fixation techniques with penetrating keratoplasty

PURPOSE

Pseudophakic corneal edema is the principal indication for penetrating keratoplasty in the United States. Currently, three techniques of intraocular lens (IOL) fixation during penetrating keratoplasty for this condition are commonly used--flexible anterior chamber IOL (AC IOL) implantation, iris suture fixation of a posterior chamber IOL (PC IOL), and transscleral suture fixation of a PC IOL. This study represents the first prospective, randomized comparison of these three techniques.

METHODS

One hundred seventy-six consecutive patients with pseudophakic corneal edema who underwent penetrating keratoplasty with IOL exchange were randomized to one of the three implantation techniques. Standardized evaluations were performed at baseline and at 6, 12, and 18 months postoperatively. Life-table analysis provided cumulative risk estimates for specific complications.

RESULTS

Randomization produced comparable groups at baseline. The cumulative risk of macular edema was significantly less for the iris fixation cohort than for either the AC IOL or scleral fixation group. A complications index was constructed based on the major adverse outcomes of glaucoma escalation, cystoid macular edema, IOL dislocation, and graft failure. A significantly lower risk of complication was found for iris compared with scleral fixation of PC IOLs.

CONCLUSION

The authors conclude that transscleral fixation of the PC IOL at the time of penetrating keratoplasty for pseudophakic corneal edema is associated with a greater risk of adverse outcome than iris fixation of a PC IOL.

Effect of vitamin A deficiency on the adhesion of rat corneal epithelium and the basement membrane complex

PURPOSE

To understand the underlying mechanisms responsible for the easy removal and sloughing of corneal epithelium in vitamin A deficiency.

METHODS

An animal model of vitamin A deficiency, the vitamin A-deficient rat (A-rat), transmission electron microscopy, computer-assisted morphometric analysis and indirect immunofluorescence were used to study the adhesion of rat corneal epithelium to its basement membrane with emphasis on structure and molecular composition of the anchoring structures such as the hemidesmosome and bullous pemphigoid antigen.

RESULTS

Transmission electron microscopy resolved numerous microseparations of the basal epithelial cell membrane from the basement membrane with intervening segmental basement membrane duplications and electron dense deposits. Morphometric analysis disclosed a statistically significant reduction in the frequency and size of hemidesmosomes. Four weeks after supplementing the diet with retinyl acetate (700 micrograms/week), significant reversal of these same structural abnormalities could be detected. Immunofluorescence staining for bullous pemphigoid antigen, a component of the adhesion complex, showed intense staining of the basal epithelial cytoplasm but weak and discontinuous staining of the basement membrane. Weak staining for laminin was also evident in A- corneas. In contrast, normal corneas displayed no cytoplasmic staining for bullous pemphigoid antigen and intense staining of the basement membrane for bullous pemphigoid antigen and laminin.

CONCLUSIONS

The authors propose that structural abnormalities of the epithelial basement membrane complex are responsible for the observed loose epithelial adhesion and sloughing, as well as other known abnormalities of healing in the vitamin A-deficient rat cornea.

In vitro propagation of human ocular surface epithelial cells for transplantation

PURPOSE

To examine the possibility that ocular surface epithelial cells might be grown in culture for use as grafts.

METHODS

The proliferative capacity of epithelial cells cultured from the conjunctiva, limbus, and central cornea of normal human eyes was compared. Single cells disaggregated from approximately 1 mm2 biopsy specimens were serially cocultured with lethally irradiated mouse 3T3 fibroblasts. To study the cells' ability to reform a stratified epithelium, confluent limbal cultures were released as an intact cell sheet with the enzyme Dispase and transplanted to a dermal connective tissue bed in nude mice. Attachment and differentiation properties of the reconstituted epithelium were examined immunohistochemically.

RESULTS

Central corneal epithelial cells could not be propagated; they senesced in first or second passage. In contrast, limbal epithelial cells exhibited a substantial (i.e., mean of 23 population doublings) and conjunctival cells a moderate (i.e., mean of 11 population doublings) proliferative capacity. Within 4 days of transplantation to the nude mouse dermis, cultured limbal epithelial cells formed an epithelium 5-6 cell layers thick. The epithelium adhered firmly to the graft bed, and deposition of the basement membrane and anchoring fibril protein collagens IV and VII and laminin was detectable immunohistochemically. The transplanted epithelium displayed limbuslike compartmental expression of keratins K3, K13, and K19, and of the enzyme enolase.

CONCLUSIONS

These results support the concept that corneal epithelial stem cells are located in the limbus and indicate that cultured autologous limbal cells may function as grafts to permanently restore the corneal epithelium after severe ocular surface injury.

Cleavage and activation of corneal matrix metalloproteases by Pseudomonas aeruginosa proteases

PURPOSE

To examine the effect of Pseudomonas aeruginosa on the expression of corneal matrix metalloproteases and the effect of its proteases on activation of corneal matrix metalloproteases in vitro.

METHODS

Rat corneas and human corneal fibroblasts were co-cultivated with two different strains (RPS & 599A) of P. aeruginosa and one strain of Staphylococcus aureus, and the conditioned media were analyzed for proteolytic activity by gelatin and casein zymography. Human corneal fibroblast-conditioned medium was incubated with that from either strain of P. aeruginosa and was analyzed in a similar manner.

RESULTS

Normal rat corneas in organ culture produce a 65 kDa gelatinase (inactive matrix metalloprotease-2), whereas thermally injured rat corneas additionally produce gelatinases with molecular masses of 92 kDa (inactive matrix metalloproteases-9) and > 200 kDa. Matrix metalloprotease-2 is also detected in human corneal fibroblast-conditioned medium. Although these matrix metalloproteases are no longer detectable when rat corneas or human corneal fibroblasts are co-cultured with two strains of P. aeruginosa for 48 hr, a 58 kDa gelatinase fragment appears in earlier stages of co-culture. In contrast, S. aureus does not affect matrix metalloprotease-2. The 58 kDa fragment is also evident by incubating human corneal fibroblast-conditioned medium with that from either strain of P. aeruginosa. Conditioned medium from the RPS strain, which produces both elastase and alkaline protease, is more effective in cleaving matrix metalloprotease-2 than that from the 599A strain, which expresses mainly alkaline protease.

CONCLUSION

The secreted inactive corneal matrix metalloprotease-2 is activated through limited proteolysis by pseudomonal proteases.

Anterior corneal disease of epidermolysis bullosa simplex

We report the histopathological findings of the anterior cornea from a patient with skin biopsy-proven epidermolysis bullosa simplex. As seen with light microscopy, the cornea had a fibrocellular pannus deep to a thickened epithelial basement membrane. Transmission electron microscopy of the anterior cornea demonstrated a nonhomogeneous basal epithelial layer with abnormal attachment complexes to an irregular, multilaminar basement membrane. The findings of transmission electron microscopy of the bulbar conjunctiva were normal.

Effect of Pseudomonas aeruginosa concentration in experimental contact lens-related microbial keratitis

Pseudomonas aeruginosa adherence in vitro to perfilcon A (ionic, 71% H2O) extended wear soft contact lenses--both new and after 7 days of continuous wear on closed rabbit eyes--was found to be related directly to the bacterial concentration in the contaminating solution. Thirty rabbits wore perfilcon A lenses for 7 days with complete lid closure to mimic contact lens overwear. After 7 days, conjunctival cultures showed no growth of pathogens, but all corneas had developed epithelial cell exfoliation and/or epithelial defects and stromal edema. The lenses were then incubated in various concentrations (10(7), 10(6), 10(5), 10(4), and 10(2) colony-forming units per milliliter or saline control; n = 5/group) of P. aeruginosa suspensions and replaced on their respective corneas with tarsorrhaphies for an additional 48 h. By day 9, corneal thickness had increased significantly, and P. aeruginosa keratitis had developed in 13 of 25 bacterially exposed eyes but not in 5 control eyes. Although with decreasing P. aeruginosa concentration the prevalence of ulcerative microbial keratitis also decreased, the initial concentration of bacteria or the initial extent of soft contact lens-induced corneal damage had no influence on the ultimate clinical severity of the disease.

Distribution of autofluorescence in the rabbit corneal epithelium

Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) was measured in order to detect the difference in redox states in rabbit corneal epithelium. The enucleated rabbit eye was mounted in an eye bank eye container with McCarey-Kaufman medium, and the autofluorescence was measured using ocular redox fluorometry as a function of depth. The PN signal distributed evenly whereas the Fp signal was greater in the posterior epithelial region than in the anterior region (p < 0.05). The PN/Fp ratio, a sensitive indicator of tissue redox state, was less in the posterior region. After the application of 1 mM of potassium cyanide in the medium, the ratio increased significantly in each layer (p < 0.001), and the difference between anterior and posterior region diminished. These results indicate that ocular redox fluorometry has the potential to resolve the redox states of the various layers of the corneal epithelium. The posterior region of the epithelium is more active in mitochondrial respiration than the anterior region.

In vitro adhesion of Pseudomonas aeruginosa and Staphylococcus aureus to surface passivated poly(methyl methacrylate) intraocular lenses

Bacterial attachment to intraocular lenses (IOLs) can be a cause of infectious endophthalmitis following cataract surgery. In this study, Pseudomonas aeruginosa and Staphylococcus aureus adhered in vitro to untreated poly(methyl methacrylate) (PMMA) and to surface passivated PMMA lenses. The IOLs were placed in bacterial suspensions (1 x 10(7) cfu/ml) in vitro. Significantly fewer S. aureus attached (P < .05) to the normal PMMA IOLs (4,535 +/- [SD] 3,052 bacteria/mm2) and to passivated PMMA IOLs (8,720 +/- 10,040 bacteria/mm2) than did P. aeruginosa (normal PMMA: 67,808 +/- 45,070 bacteria/mm2, passivated PMMA: 85,795 +/- 70,647 bacteria/mm2). The differences in bacterial attachment to surface passivated IOLs and to untreated PMMA lenses were not significant.

Proteolytic activation of corneal matrix metalloproteinase by Pseudomonas aeruginosa elastase

Purified Pseudomonas aeruginosa elastase cleaved a 65 kDa gelatinase [inactive proenzyme form of matrix metalloproteinase (MMP-2)] from human corneal fibroblasts into a biologically active fragment with an approximate molecular mass of 58 kDa. However, purified pseudomonal alkaline protease did not cleave MMP-2 appreciably. Since activated MMP-2 is known to degrade native type IV, V and VII collagens, all components of the corneal basement membrane or stroma, our results suggest a new role for pseudomonal elastase in the pathogenesis of corneal infection, inflammation and ulceration.

[Metabolic analysis of the diseased human corneal endothelium]

Redox states of the corneal endothelium in 42 recipient corneas obtained at the penetrating keratoplasty were measured non-invasively using ocular redox fluorometry. Autofluorescence from reduced pyridine nucleotides (PN) and oxidized flavoproteins (Fp) were measured, and the PN/Fp ratio was used as an indicator of the redox state. Endothelial damage was graded as normal, mildly damaged, moderately damaged, and severely damaged, based on the histopathological findings. Mildly damaged endothelium showed a significantly higher PN/Fp ratio than the that in normal endothelium whereas the ratio was significantly lower in the severely damaged endothelium. These changes in the redox state may represent compensation and decompensation processes of the endothelial metabolism. Ocular redox fluorometry was shown to be useful for the evaluation of the metabolic state in the human corneal endothelium.