Toxigenic strains of Staphylococcus epidermidis and their experimental corneal pathogenicity in rabbits.

Thirty strains of Staphylococcus epidermidis, ten each from normal conjunctival sacs, corneal ulcer cases and from those who developed postoperative endophthalmitis, were examined for their dermonecrotic and haemolytic activities. Dermonecrosis was studied on rabbit skin whereas haemolysis was determined against sheep, guinea pig, rabbit and human erythrocytes. None of the cell free filtrates from strains derived from normal sacs showed any evidence of toxin production. Four strains from corneal ulcer cases and five from postoperative infections produced + to + + + dermonecrosis whereas haemolytic activity was exhibited by one strain in the former and by two in the latter. Only those strains that were highly dermonecrotoxic were haemolytic. Experimental corneal lesions in the rabbit were mild by strains from normal sacs. Those showing highest dermonecrotoxic reaction, irrespective of their source, produced identical and most severe corneal pathology when compared to those producing minimal necrosis.

Pseudomonas aeruginosa: isolation from ocular tissues. Aeruginocin typing and its relationship to corneal pathogenicity in rabbits.

Fifty strains of Pseudomonas aeruginosa isolated from human eyes were aeruginocin typed by the method of Shriniwas (1974) using ten indicator strains. These belonged to types A1 (3), B (2), F1 (1) and 14 (1). Fifteen (30%) were nontypable and 28 (56.0%) were unclassifiable presenting twenty inhibition patterns. The strains showed a wide range of antibiotic sensitivities. The highest number of insensitive strains were those obtained from corneal ulcers. Experimental keratitis produced by strains of pseudomonas was either mild, moderate or severe and was unrelated to their source. Mild keratitis was produced by types UC 7-, UC 79- and 14 isolated from pre-operative, corneal ulcer and post-operative patients. Lesions of moderate severity were produced by types 189+ & A1 whereas the severest pathology was produced by UC 23478-, B and UC 810- types. The fact that strain 23478- always produced severest pathology irrespective of whether originated from group I, II, or IV strongly suggests relationship of pathogenicity with aeruginocin type.

Role of coagulase-negative staphylococci and micrococci in ocular disease.

Forty-nine strains of coagulase-negative staphylococci and 26 strains of micrococci isolated from human eyes were classified by the Baird-Parker system of 1966. The staphylococci belonged to subgroups II, III, IV, and V with one strain each in subgroups III and IV. However, when biotyped by Baird-Parker's system of 1974, less than 50% (23/49) of strains were typable and they belonged to biotypes 1 and 2. With our proposed modified classification all strains could be classified into biotypes 1, 2, and 3. All the 26 strains of micrococci belonged to subgroup VII. Staphylococci isolated from diverse sources produced, qualitatively and quantitatively, different corneal pathology in rabbits when compared to those isolated from healthy conjunctiva. This bore no relation to the present system of subtyping based on biochemical reactions. Micrococci were incapable of producing experimental corneal lesions in the rabbit.

Preventable hazard of soft lens wear.

Recurrent pseudomonal conjunctivitis, caused by poor soft contact lens care and the use of contaminated saline, is described. This problem can easily be avoided by proper sterilization, with boiling being the method of choice.

Mast cells and pterygium.

A total of thirty pterygia were studied for mast cells using metachromatic dye (toluidine blue) together with routine histological stains. On microscopic examination, the lesion was differentiated and classified into angiomatous, fibrous and mixed varieties based on the vascular and collagenous components. The mast cell counts were undertaken in all types and were found to have significant correlation with the morphological types when compared to normal conjunctiva. 15.1 +/- 3.1, 22.7 +/- 3.8, 9.5 +/- 3.2 mast cell per mm2 were found in the angiomatous, mixed and fibrous types respectively. In the control material, the mast cell count was 12.4 +/- 2.3 per mm2. The results are discussed. It is believed that mast cells are actively involved in the genesis and progress of pterygium.

Visual acuity improvement in eyes with corneal scars fitted with contact lenses.

The vision of 190 eyes of 130 patients with corneal scars was tested with contact lenses, of which 166 eyes subsequently were fitted with contact lenses. Over 75% of all eyes with corneal scars showed a visual acuity improvement to 6/12 or better. All eyes with a nebular or macular corneal scar and an initial visual acuity of 6/60 or better improved to 6/12 or better. The visual acuity of 77% of the eyes fitted with contact lenses, compared to the visual acuity of 36% of the same eyes obtained with spectacle lenses, improved to 6/12 or better.