Conjunctival epitheliopathy induced by topical exposure to bacterial peptidoglycan, muramyl dipeptide.

Noninfectious exudative conjunctivitis can be experimentally produced in rabbits by application of the apoptogenic bacterial cell wall peptidoglycan, muramyl dipeptide (MDP) to the ocular surface. The purpose of this study was to investigate the acute conjunctival cytopathology induced by unilateral ocular surface exposure to MDP. Hematoxylin and eosin staining assessed bilateral tear cytopathology and conjunctival histopathology. The caspases levels in conjunctival tissue and tears were measured in standard assays utilizing p-nitroanaline tagged caspase-specific substrates. Immunofluorescent antibody identified intracellular caspase-3, nuclear factor-κß (NF-κß), and oxidative DNA damage (8-OHdG; 8-oxo-2'-deoxyguanosine) in tear and conjunctiva cells. DNA extracted from conjunctival tissues and pooled tear fluids were visualized by ethydium bromide agarose gel electrophoresis. Onset of ipsilateral conjunctivitis was due to an epitheliopathy characterized by loss of conjunctival epithelial cell adherence, exuviation of conjunctival epithelial cells, and neutrophil infiltration. Caspase-3 levels were significantly higher in exuviated cells in ipsilateral than contralateral tear (p's ≤ 0.001) collected at 3-5 h post MDP. Significantly higher caspase-2, -3, -6, -8 and -9 (p's ≤ 0.03) levels were detected in ipsilateral than contralateral conjunctival tissue at 5 h. Polymeric DNA was detected in ipsilateral but not contralateral conjunctival tissue and tears. Caspase-3, NF-κß, and 8-OHdG positive neutrophils were detected in bilateral conjunctiva and tear. The caspase-3/NF-κß epithelial cells and polymeric DNA in conjunctival tissue and shedding of caspase positive cells and polymeric DNA into ipsilateral tears support MDP induction of acute programmed cell death in vivo. The results suggest that ipsilateral exudative conjunctivitis is due to acute caspase-mediated conjunctival epitheliopathy induced by topical exposure to the bacterial peptidoglycan MDP.

Refractive and topographic fluctuations due to intracorneal ring segments motility.

PURPOSE: To describe a patient with refractive and topographic fluctuations 5 years after intracorneal ring segments (ICRS) implantation for the management of corneal ectasia after LASIK. METHODS: Case report. RESULTS: A 48-year-old woman presented complaining of intermittent decreased vision over 1 year that improved with eye rubbing. Slit-lamp and optical coherence tomography (OCT) examinations revealed overriding ring segments that could be restored to normal position after minor corneal massage. Topographic and refractive findings were significantly influenced by the ICRS positioning and caused decreased visual function when overriding. To avoid ICRS override, surgical dissection of the corneal tunnel along with ring segment repositioning was performed. A suture was placed through the ring's positioning hole to stabilize the ICRS at its optimal position and to avoid recurrence of this phenomenon. CONCLUSIONS: Patients undergoing femtosecond laser-assisted ICRS implantation may experience ring segment migration and override of the segments that could lead to decreased visual function. Proper surgical repositioning and ring segment fixation may address this complication and offer satisfactory visual and refractive outcomes along with avoidance of ICRS migration and override.

Bilateral acute pyogenic conjunctivitis with iritis induced by unilateral topical application of bacterial peptidoglycan muramyl dipeptide in adult rabbits.

The factors responsible for the conjunctivitis and iritis associated with acute ocular infection and post enteric inflammatory disease are not fully known. The pro-inflammatory activity of unilateral topical application of muramyl dipeptide (MDP; the smallest bio-active Gram-positive and Gram-negative bacterial cell wall component) was investigated in adult rabbits. The resultant bilateral conjunctivitis/iritis and pyogenic responses were characterized. Bilateral symptoms were graded by slit lamp examinations; tear fluid, Schirmer tests (tear production), blood and aqueous humor (AH) samples were obtained from MDP-treated and untreated rabbits. MDP concentration, gamma-glutamyltranspeptidase activity (GGT; key enzyme in glutathione recapture, xenobiotic detoxification, eicosanoid synthesis and neutrophil function), protein concentration, and tear cell density, cytology, and immunofluorescent antibody reactivity to GGT and calreticulin (CRT; MDP-binding protein) were determined. MDP was cleared from ipsilateral tears and serum by 6 h, but was undetected in mock-treated contralateral tears. Bilateral signs of acute transient pyogenic conjunctivitis, characterized by tearing, lid edema, conjunctival hyperemia, chemosis and leukocytic infiltrate with iritis (erythema and aqueous flare) were detected. Milder symptoms occurred in the mock-treated contralateral eyes. Bilateral symptoms, tear production, tear protein, GGT activity, and mucopurulent discharge (containing up to 2.5-5.0 × 10(6) cells/mL) were elevated 4-8 h post MDP and resolved to near pre-treatment levels by 24 h. Tear GGT activity and protein levels were higher in MDP-treated and mock-treated contralateral eyes than in eyes of untreated adult rabbits (p's < 0.001). Elevated tear GGT activity was associated with histopathology and increased vascular and epithelial permeability to serum protein, GGT-positive epithelia cells, macrophages and heterophils. Repeat MDP applications induced recurrent induction and resolution patterns of bilateral conjunctivitis/iritis and tear GGT activity, but ipsilateral GGT responses were lower. The results suggest unilateral topical MDP application to adult rabbit eyes induces a bilateral acute pyogenic conjunctivitis/iritis (PCI) characterized by increased vascular and epithelial permeability similar to acute bacterial conjunctivitis in man. The detection of CRT/GGT positive heterophils in tears suggests efferocytosis (phagocytosis of dead/dying cells). Tear GGT activity may be a useful means to quantify MDP-induced toxicity and extraocular inflammation.