Severe infectious keratitis is a major cause of ocular morbidity in temperate and tropical regions. Predisposing factors for central corneal ulceration in these areas include ocular surface disease, contact lens wear (even without corneal epithelium disruption), previous trauma, cocaine abuse, and the use of traditional eye medicines. Ulcerative keratitis also develops in 4.7% of patients with prolonged bullous keratopathy. Steroid drops and bandage soft contact lenses are also risk factor for microbial ulcers in bullous keratopathy. Prophylactic antibiotic use does not seem to prevent ulcer development. Conditions associated with systemic immune suppression should also be considered among the disease that constitutes higher risk factor for patients with infectious keratitis.

Microbial keratitis is a serious complication of contact lens wear. In certain communities in the USA, contact lens wear was found to be the most significant risk factor for developing ulcerative keratitis. Contact lens and also contact lens cases are major sources for corneal infections in contact lenses wearers. A study of 178 asymptomatic wearers found microbial contamination in 53% of the cases. Contact lenses cases hygiene is as important as lens hygiene, frequent and regular changes of the cases may prove to be a necessary measure to prevent contamination.

Among the various types of contact lenses, extended wear soft contact lenses seem to carry the greatest risks for causing corneal problems. Overnight-extended wear is the most important risk factor for developing ulcerative keratitis even with disposable contact lenses and good hygienic measures. Previous reports found that the relative risk of developing ulcerative keratitis for overnight wear is 21 for soft lenses, 3.6 for daily wear soft lens when compared with gas permeable hard lenses. 49% to 74% of contact lenses related ulcerative keratitis could be prevented by not wearing the lenses over night. Corneal hypoxia caused by overnight wear with the accumulation of deposits and contamination of the lens lead to higher risk of complications and corneal infection.

Daily disposable contact lenses have many advantages over extended wear contact lenses e.g. minimal handling and less need for hygienic compliance. It had been hoped that this theoretical advantages might eliminate the incidence of ulcerative keratitis with this type of contact lenses, but higher rate of complications may also occur with extended wear of daily disposable contact lens. The main complications associated with extended wear of disposable contact lens are, however, sterile corneal infiltrates. It seems that frequent and regular disposing of lenses does not completely eliminate complications.

Large central corneal ulceration is more often associated with positive culture and anterior chamber activity than peripheral ulcers. There has been some controversy regarding the need for complete work-up in suspected microbial keratitis. 3 different strategies for management have previously been proposed:

• Complete laboratory work-up for all cases.
• Complete laboratory work-up only for unusual or severe corneal ulcers.
• Work up, only, if treatment with the common antibiotics fails.

Most authorities consider that complete work-up should be carried out in all suspicious microbial keratitis. Corneal scrapings should be taken from all lesions not including the visual axis. The scrapings should be cultured on blood agar, chocolate agar, Sabouraud, and Thioglycate medium. Corneal specimens should also be stained with gram and Giemsa stains as a routine. Optional culture media and special stains for specific infections can also be carried out in suspected cases. Corneal biopsy may also be needed in chronically progressive lesions.

Confocal in vivo slit scanning video-microscope is a new confocal microscope which offer a non-invasive and non-contact imaging of the corneal layers with good lateral and axial resolution and also good contrast even in the presence of corneal opacities, without the need for histological staining. The technique has been shown to give results that are consistent with histopathological and biochemical techniques. This technique is, however not as sensitive as biomicroscopy in some conditions.

There are several topical fluoroquinolone eye drops available now on the market. The main preparations are:

• Ciprofloxacin.
• Norfloxacin.
• Ofloxacin.
• Sparfloxacin.

The three preparations have similar antibiotic spectrum of activity but ciprofloxacin seems to be more potent than the other two. The greater potency of ciprofloxacin seems to offset the superior corneal penetration ability of Ofloxacin. The combination of fluoroquinolone e.g. ciprofloxacin, norfloxacin, or ofloxacin is superior to any of the fluoroquinolone alone.

Fluoroquinolone preparations should be used with caution in patients with a history of convulsions, epilepsy, or liver or kidney failure. Frequent application of ciprofloxacin or norfloxacin drops, especially in patients with dry eyes or eyes with corneal ulcers may cause a white precipitate on the ulcerated corneal surface which may lead to the formation of a firmly adherent plaque which might delay corneal healing.

Ciprofloxacin or ofloxacin is effective as single agent in the treatment of ulcerative keratitis. They seem to be as effective as, or better than fortified topical antibiotics drops (e.g. Cefazolin and Gentamicin). Mono-therapy with ciprofloxacin has the advantage of being easier to prepare more cost effective, and also being less toxic to the cornea.

Topical ciprofloxacin may also be effective in cases with non-tuberculous mycobacterium keratitis that does not respond to amikacin treatment.

Continued use of the drug has lead to the emergence of increasing resistance to the drug, among gram positive and gram negative bacteria including Staphylococci aureus, Streptococci, Pseudomonas and Neisseria gonorrhoea. It is estimated that about 30.7% of the pathogens causing bacterial keratitis are developing resistance to the drug. Care should be taken when using fluoroquinolone as a mono-therapy in bacterial keratitis because of these emerging resistances among many pathogenic bacteria. Resistant cases may be treated with cefazolin in gram positive infection, or gentamycin in gram negative infections.

Sparfloxacin is a new member of the fluoroquinolone family of antibiotics. The drug is particularly active against microbial infections against which the fluoroquinolone drugs in general have low activity (e.g. streptococci, mycoplasma, and chlamydia).

Cat scratch disease is a systemic disease characterised by lymphadenopathy, fever, and malaise. The disease is probably caused by Bartonella henselae infection (a gram-negative bacillus). Transmission from cats to patients often occurs via fleabites. The disease can also be transmitted by bites from an infected animal (often a cat or a dog).

Patients often develop an erythematous papule or pastule followed by a systemic rash within days or weeks. The typical ocular features are painful regional lymphadenopathy and follicular conjunctivitis. The disease may also be associated with Serous retinal detachment of the macula, neuroretinitis, a retinal white spot syndrome, intermediate uveitis and retinal vasculitis, unifocal choroiditis, inflammatory mass of the optic nerve head producing acute loss of vision and focal choroiditis. An unusual, well-defined retinal opacification with features of both multiple retinal arteriolar occlusions and a low-grade retinitis has also been described.

Rochalimaea henselae infection should be considered in intraocular anterior and posterior inflammation with optic nerve swellings even in the absence of a history of cat scratch or lymphadenopathy. Oral ciprofloxacin, Rifampicin or Doxycycline and steroids can achieve improvement in the inflammation and in the visual acuity. Diagnosis of this disease can be confirmed by specific enzyme-linked immuno-assay (ELISA) serologic tests, as well as lymph nodes, conjunctival or skin biopsy.

Avellino corneal dystrophy is a relatively new type of stromal corneal dystrophy, which was originally described in patients originating from the Italian province of Avellino. Avellino dystrophy is characterised by anterior stromal deposits and deep fusiform stromal deposits. The corneal deposits have been shown to be amyloid material. There is a substantial phenotype variation in patients with this dystrophy. Granular, lattices type Avellino and dystrophies have been independently linked to the same region on chromosome 5q. Histological evidence also suggests that these dystrophies are caused by mutation within the same gene. The three diseases may be phenotypic variations caused by mutation in the same gene.

The need for treatment depends on disease activity. Super-added bacterial or toxic conjunctivitis should be excluded and treated. Systemic immunosuppression treatment is regarded to be the treatment of choice of the disease. Broad-spectrum medication (e.g. steroids) may be more effective in the treatment of this disease than specific immunosuppressant drugs (e.g. cyclosporin). High doses topical steroids alone is often ineffective in controlling the conjunctival inflammation. Cylclophosphamide and short term high dose steroid is often effective in treating severe ocular pemphigoid but may not completely prevent ocular scarring.

Dapsone is the most effective initial agent for active disease, it is also a safer treatment in the elderly than steroids. Dapsone commonly induces significant haemolytic anaemia (more commonly in patients deficient in the enzyme glucose 6-phosphatase dehydrogenase). Patients are also at higher risk of agranulocytosis. Dapsone-induced neutropenia may not be dose dependent and routine white blood cells monitoring (specially 8 to 10 weeks after treatment) in needed. A taste disturbance and tingling sensation in the mouth and lips has been reported as a side effect of Dapsone.

Intravenous immunoglobulin treatment may also be effective in arresting progress in cicatricial ocular pemphigoid in resistant cases. The treatment consists of cycles, which can be repeated every 2 to 6 weeks. Each cycle involve administration of 2 to 3 g/Kg body weights of the immunoglobulin over a 3 days. Other drugs that has been used include Sulphapyridine and Interferon Alfa-2

In patients with cicatricial obliteration of the conjunctival fornices, surgical lysis of the adhesion followed by intraoperative application of 0.4 mg Mitomycin C / ml in saline for 3-5 minutes seems to be useful in preventing fornices shrinkage. Sub-conjunctival injections of Mitomycin C might be effective in preventing progression of the disease.

Conjunctival surgery and opening the conjunctiva should be avoided in the acute stages of the disease when possible. Ocular pemphigoid and Sjogren’s syndrome have always been difficult to treat because of the immediate recurrence of the adhesions. Mucous membrane grafts can successfully protect the corneal surface without provoking the conjunctiva inflammation in most cases, but in the long-term complications eventually develop in a large number of patients. Mucous membrane grafts should not be performed in severe keratoconjunctivitis sicca, very advanced ocular cicatricial pemphigoid or active conjunctiva inflammation without proper immunosuppressive treatment.

Penetrating keratoplasty in patients with advanced cicatricial conjunctivitis disease can be performed for tectonic reasons. Visual restoration is often limited even after intensive medical treatment. The major causes of failure of the penetrating keratoplasty are epithelial defects, stromal ulceration, perforation, and infections.