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   Table of Contents      
GUEST EDITORIAL
Year : 1987  |  Volume : 35  |  Issue : 4  |  Page : 176-177

Ocular Infections


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Date of Web Publication20-Dec-2008

Correspondence Address:
M R Jain
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Source of Support: None, Conflict of Interest: None


PMID: 3506926

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How to cite this article:
Jain M R. Ocular Infections. Indian J Ophthalmol 1987;35:176-7

How to cite this URL:
Jain M R. Ocular Infections. Indian J Ophthalmol [serial online] 1987 [cited 2019 Jun 17];35:176-7. Available from: http://www.ijo.in/text.asp?1987/35/4/176/26183

Inspite of the availability of a very large number of mega spectrum antimicrobials, and steroidal and non-steroidal anti- inflammatory drugs and various modalities of drug delivery systems, ocular infections specially those involving the internal structures of the eye ball remain a challenge to ophthalmologists since they have the potentiality, to lead to, permanent and irreparable blindness

In the last three decades, vast progress has been made in the discovery of newer and potent antibiotics ranging from Venicillin, Chloromycetin, Tetracycline, Ampicillin, Framycetin, Carbenicillin, Aminoglycosides and multiple generations of Cephalosporins These antibiotics cover almost all known bacteria though some of the strains may defy or mutate to defy even the most potent antibiotic. Gentamicin which is effective against most of the gram negative organisms including most strains of Ps aeruginosa as well as against Coagulase positive Staph aureus has greatly revolutionised the treatment of ocular infections in the last decade. Newer aminoglycosides, namely, tobramycin, amikacin, sisomicin and netilmicin have the same spectrum as gentamicin but are considered to be more rapid in effect and covers even some of those strains of organisms which are resistant to gentamicin. Third generation cephalosporins are extremly effective against gram positive organisms and a combination of aminoglycosides and cephalosporins produce a synergistic effect and covers almost the whole bacterial spectrum.

A new modality involving the use of freshly prepared fortified antibiotic eye drops with adequate shelf life has added a new dimension to the management of bacterial corneal ulcers with or without pus in the anterior chamber.

It is anticipated that less and less number of bacterial corneal ulcer cases would need subconjunctival therapy as this modality is most often associated with discomfort and at times varying degree of pain and conjunctival reaction.

Keratomycosis which seems to be on the increase, is still a challenge since their management is protracted and frustrating due to lack of availability of safe and effective antifungal agents which could attain therapeutic effective levels in ocular structures and cavities Amphotericin B has a high degree of penetration but can cause systemic as well as ocular toxicity. Natamycin solution may be effective in superficial comeal ulcers but has poor ocular penetration More recently introduced imidazole group of drugs like miconazole and ketocenazole promise to be the best available drugs due to lack of toxicity, capacity to penetrate into the eye and a broad range of antifungal activity. Ketoconazole when given orally gives satisfactory results in keratomycosia.

Prognosis in viral keratitis has considerably improved after the introduction of acydovir, vidarabine, trifluridine and bromovinyl deoxyuri­dine (BUVU). In metaherpetic and herpetic inter­stitial keratitis, antiviral drugs along with the judicious use of diluted steroids give excellent results In some of the chronic non healing ulcers bandage soft lenses may given miraculous results.

The biggest constraint in the management of intraocular infection is the inadequate bioavail­ability of the drug into the eye specially into the vitreous chamber. Systemically administered drugs have poor penetration into the eyes due to blood aqueous barrier. Penetration of topically instilled drugs depend upon multiple factors like solubility characteristics of the drug, molecular size of the drug, the time duration of drug contact to the cornea and the differential barrier inherent in the corneal epithelium, substantia propria and endothelium A biphasic soluble drug in a vehicle of methyl cellulose or polyvinyl alcohol has a better ocular penetration, or the drug penetration is enhanced if the integrity of the corneal epithelium is disturbed Soft contact lenses by virtue of their high water content and large intermoleular pore size absorb water soluble drugs and due to increased contact time, release the drug initially in a high pulse and then gradually, thereby comply­ing with 'first order kinetics'. Subconjunctivally injected drugs short circuit the essential barrier set up by the corneal and conjunctival epithelium provide therapeutically effective drug levels in the aqueous for a period of 6 to 12 hours. Softcontact lens delivery system and subconjunctival therapy both conform to first order kinetic but the drug levels attained with soft lenses more so with high water content lenses, are significantly higher than subconjunctival therapy though the bioavailability duration is comparatively short.

All these modalities fail to provide adequate drug levels into the vitreous The only alternative left is to inject antimicrobials into the vitreous directly through the pars plana in phakic eyes and through the anterior hyaloid in the aphakic eyes. A single intravitreal injection in therapeutic doses provide adequate bactericidal concentration for a period of about 50 to 60 hours. Strict supervision has to be maintained in preparation of intravitreal injection in recommended therapeutic doses since drugs injected in doses larger than recom­mended may cause permanent and irreparable damage to the neuro sensory and pigmentary epithelium of the retina. Pseudophakos have added new dimensions to the etiology and man­agement of endophthalmitis since quite often the artiphake is wrongly implicated as the cause but some times it may be the real culprit leading to chemical or sterile endophthalmitis. Judiciously performed vitrectomy in addition to intravitreal therapy may give astonishingly good results in sight threatening cases of endophthalmitis.

Search is still on for an antibiotic which could be effective against all known bacteria Lot more research is needed to find out an antimycotic drug which could reduce the protracted course of keratomycosis and could effectively penetrate into the eye when administered systemically or instilled topically or could be safely injected into the eye to treat the most dreaded complications of fungal endophthalmitis




 

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