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• Streptococcus mitis isolated from a human with infectious crystalline keratitis was injected intrastromally into corneas of adult New Zealand white rabbits that were treated with tetracycline hydrochloride, methylprednisolone acetate, or a combination of tetracycline and methylprednisolone. Animals were followed up for up to 44 days; untreated corneas and those treated with tetracycline developed no disease or "fluffy" stromal infiltrates with overlying epithelial defects representing an abscess. Corneas treated with the combination of tetracycline and corticosteroid usually developed crystalline stromal opacities that on histopathologic examination were shown to be intrastromal aggregates of cocci. Transmission electron microscopy of crystalline lesions within 10 days of infection revealed typical cocci intermixed with a fibrillar material having periodicity characteristic of fibrinogen or fibrin, and immunoperoxidase staining for fibrinogen was positive. By 1 month, electron microscopy revealed aggregates of degenerated bacteria that were surrounded by cellular processes of activated keratocytes. Our studies demonstrate a model for crystalline keratitis in which organisms are seen to reside within the stroma for up to 44 days without an inflammatory response. Periocular corticosteroids appear to be necessary to create this model. It is possible that the organisms are isolated from the host response by fibrin or by keratocytes.

• A computerized videokeratoscopy system was used to evaluate changes in corneal topography after muscle surgery in 36 eyes of 18 rabbits. Topographic analysis revealed a significant flattening of the cornea in the superior and supero-temporal octants after superior rectus recession (mean±SE, -1.78±0.16 diopters) compared with control eyes undergoing a sham procedure (-0.17±0.18 D; P<.05). Excision of all rectus muscles caused a generalized corneal flattening (-1.42±0.13 D; P<.001). A computerized, finite element model of the globe, including the rectus muscles, demonstrated corneal deformation as a result of extraocular muscle tension; recession of an extraocular muscle in this model caused corneal flattening in the quadrant of the recessed muscle. These data suggest that corneal topography is affected by extraocular muscle tension, corroborating clinical reports of refractive change after strabismus surgery.

• A computerized videokeratography system was used to evaluate diurnal changes in corneal curvature of both untreated and surgically treated eyes of 11 patients who had undergone unilateral radial keratotomy. The mean postoperative interval was 34.5 months. Both corneas operated on and those not operated on steepened on average from morning to evening. For untreated eyes, this diurnal steepening was statistically significant at a distance of 0.5 mm from the corneal apex (mean±SE, 0.36±0.07 diopter) and in the inferotemporal quadrant (0.28±0.08 D); in eyes that had undergone radial keratotomy, steepening was significant at from 1.0 to 3.0 mm from the corneal apex (0.39±0.07 D) and temporal, inferotemporal, inferior, inferonasal, nasal, and superonasal to the corneal apex (0.42±0.08 D). The greatest steepening in the eyes treated with radial keratotomy compared with the untreated eyes occurred at 1.5 to 2.5 mm peripheral to the corneal apex in the inferonasal and nasal octants. Diurnal changes in intraocular pressure, corneal thickness, number of incisions, clear-zone size, postoperative period, and patient sex were not predictive of the magnitude of morning-to-evening change. Furthermore, diurnal changes in corneal curvature of untreated eyes were not predictive of diurnal changes in the fellow eyes after radial keratotomy.

• Computer-assisted photokeratoscopy was used to evaluate the topographic characteristics of corneas preoperatively and postoperatively in seven patients who underwent surgery for correction of postkeratoplasty astigmatism. The steep hemimeridians were typically separated by an angle other than 180° (mean, 162.5°) and the flat hemimeridians were often not orthogonal to the steep hemimeridians. Asymmetry of power (1.5 or more diopters) between these two major hemimeridians was also observed in three patients. Relaxing incisions were placed in the two steep hemimeridians and compression sutures were placed in the flat hemimeridians. The mean percent of reduction of astigmatism (vector-corrected) was 81.1%. The amount of keratometric astigmatism, and the degree of asymmetry of the hemimeridians were not correlated with the percent of reduction of astigmatism after placement of the relaxing and compression sutures. Computer-assisted topographic analysis may prove useful in planning transverse keratotomies centered on the steep hemimeridians and in placement of compression sutures in flat hemimeridians.

• Topical steroids potentiate Pseudomonas keratitis in the absence of concomitant antibiotic therapy. The effects of other anti-inflammatory agents on microbial keratitis are unknown, but if these agents do not intensify the infection, they may be useful in the initial management of microbial keratitis by limiting ulceration and thus the size of the resultant corneal scar. In rabbit models of untreated Pseudomonas keratitis and pneumococcal keratitis, topical 1% prednisolone phosphate, 0.03% flurbiprofen sodium, and vehicle were applied hourly. In cases of Pseudomonas keratitis, prednisolone worsened the clinical disease, and flurbiprofen further worsened the disease. When combined with effective antibiotic therapy, neither anti-inflammatory agent worsened the disease. In pneumococcal keratitis, neither anti-inflammatory agent worsened the disease. Topical anti-inflammatory agents should be used with caution in cases of microbial keratitis at least until effective antibiotic therapy has been instituted.

The authors report a case of Listeria monocytogenes endophthalmitis in a patient who had undergone cardiac revascularization surgery and was receiving systemic corticosteroids. The organism was isolated both in the aqueous humor and in blood culture. The infection was successfully treated with intravenous crystalline penicillin, but the patient developed a bullous keratopathy and secondary glaucoma, resulting in poor visual acuity (counting fingers at 0.5 m). The visual acuity recovered to 20/30 after a penetrating keratoplasty and the glaucoma was controlled with a Molteno implant and a trabeculectomy combined with administration of mitomycin. Listeria monocytogenes endogenous endophthalmitis should be suspected in any immunosuppressed patient with severe anterior uveitis, especially when a brown hypopyon, high intraocular pressure and corneal edema are present.