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Acanthamoeba keratitis: Risk factors and outcome
Craig and Blades are unsuitable. The limitations of contact lens correction after keratoplasty are discussed.
Clinical Assessment of Ocular Response to a Multipurpose Contact Lens Care Solution. Bergmanson JPB, Barbeito R: Ophthalmic Physiol Opt 1995;15:535-544. The authors investigated the possible adverse ocular effects of complex-formulation multipurpose contact lens solutions. In addition to an investigation of the extent of tear film destabilizing surfactant effects, other ocular variables were examined as indicators of toxicity resulting from absorption across the ocular surface. Seventy-three normal subjects (around 50% contact lens wearers) were examined on two occasions, 15 minutes postdelivery of 100 ~1 of B&L m Renu or 0.9% saline to the ocular surface. Measurements were conducted to ascertain invasive and noninvasive tear film breakup time; intraocular pressure, pupil size, accommodation, vertical palpebral aperture size, pupil reactivity, and conjunctival vascular response. The data were analyzed by the use of both traditional parametric techniques and equivalence analysis. Fluorescein breakup time data were found to be more variable than the data associated with the corresponding noninvasive technique, allowing less reliable conclusions to be drawn. No significant differences in the ocular variables examined, were found between the two treatments. This would suggest that this multipurpose contact lens solution does not mediate any detectable deleterious tear film stability effects or toxicity-mediated autonomic effects within 15 to 45 minutes postocular exposure. Although this investigation detected no short-term effect of a contact lens care solution, further investigation may be warranted to fully discount the possibility of accumulative toxic effects associated with the ocular application of such agents.
Acanthumoeba Keratitis: Risk Factors and Outcome. Illingworth CD, Cook SD, Karabatsas CH, Easty DL: Br J Ophthalnol 1995;79:1078-1082. The authors present a review of the etiology, diagnosis, treatment, and outcome of 23 cases of Acunthamoeba keratitis presenting between 1985 and 1995 to a United Kingdom eye hospital Twenty-three patients (mean age, 31 years) presented over this period. Of the suffers 88%, had no previous history of ocular problems, and all were contact lens wearers. Sixty-seven percent were disposable soft lens wearers, and 91% of the patients presented in the 1990s. Forty-eight percent of the patients presented between January 1994 and February 1995 alone. Of the sufferers, 50% used a chlorine-based disinfectant system (18% used no
disinfectant, and others reported poor lens hygiene). Diagnosis was based on clinical appearance and laboratory findings. In 77% of cases, an incorrect initial diagnosis of a viral keratitis was made. Over the lo-year period, a decrease in diagnostic delay has been achieved. A total of 39% of the patient’s required penetrating keratoplasty to be performed. These were all cases with a lengthy period between presentation and treatment initiation. Seventy-eight percent of the sufferers had a final corrected acuity of 6/6 after medical/surgical intervention. Although Acanthamoeba keratitis, possibly associated with contact lens wear, would appear to be on the increase, advances in medical and surgical intervention and decreased diagnostic delay may provide successful treatment in the majority of cases. Both contact lens wear (especially disposable lens wear) and chlorine-based disinfectant systems are proposed as possible predisposing factors in Acunthumoeba keratitis. In the light of these findings, great care should be taken on the presentation of atypical keratitis in association with contact lens wear.
Successful Immunization Against Acunthamoeba Keratitis in a Pig Model. Alizadeh H, He Y, McCulley JP, et al.: Cornell 1995;14:180-186. Although free-living Acantharnoeba protozoa are common in the environment, and contact lens wear is a major risk factor of infection, the incidence of Acanthamoeba keraticis is relatively rare. This would suggest some form of widespread immune response-mediated protection in the general population. This may still leave a small group of nonimmune individuals at risk of infection. An animal model (pig) has been developed for the investigation of this infection. The pig is susceptible to Acunthamoeba keratitis in a way similar to that of the human. It is understood that 100% of normal pigs develop severe keratitis when infected via a parasite-laden contact lens. Using this model, the authors investigated the effects of prior ocular infection with Acanthamoeba trophozites or injections of parasite antigens either (a) intramuscularly; (b) subconjunctivally; or (c) intramuscularly and subconjunctivally, in an attempt to induce sustained immunity. Intramuscular inoculation alone and prior ocular infection alone gave no protection against pathologic response to future exposure. Subconjunctival exposure alone afforded protection in 5C% of cases. Combined subconjunctival and intramuscular inoculation afforded protection in 100% of cases tested. The results would suggest that it is possible to induce total protection against Acanthamoeba keratitis in an animal model that is similar to the human condition. Further work elucidating the immune response to Acanthamoeba antigens may extend our ability to prevent, detect, and treat this sight-threatening infection with greater accuracy and efficiency.
ICLC, Vol. 23, March/April
1996
79
Clinical Assessment of Ocular Response to a Multipurpose Contact Lens Care Solution. Bergmanson JPB, Barbeito R: Ophthalmic Physiol Opt 1995;15:535-544. The authors investigated the possible adverse ocular effects of complex-formulation multipurpose contact lens solutions. In addition to an investigation of the extent of tear film destabilizing surfactant effects, other ocular variables were examined as indicators of toxicity resulting from absorption across the ocular surface. Seventy-three normal subjects (around 50% contact lens wearers) were examined on two occasions, 15 minutes postdelivery of 100 ~1 of B&L m Renu or 0.9% saline to the ocular surface. Measurements were conducted to ascertain invasive and noninvasive tear film breakup time; intraocular pressure, pupil size, accommodation, vertical palpebral aperture size, pupil reactivity, and conjunctival vascular response. The data were analyzed by the use of both traditional parametric techniques and equivalence analysis. Fluorescein breakup time data were found to be more variable than the data associated with the corresponding noninvasive technique, allowing less reliable conclusions to be drawn. No significant differences in the ocular variables examined, were found between the two treatments. This would suggest that this multipurpose contact lens solution does not mediate any detectable deleterious tear film stability effects or toxicity-mediated autonomic effects within 15 to 45 minutes postocular exposure. Although this investigation detected no short-term effect of a contact lens care solution, further investigation may be warranted to fully discount the possibility of accumulative toxic effects associated with the ocular application of such agents.
Acanthumoeba Keratitis: Risk Factors and Outcome. Illingworth CD, Cook SD, Karabatsas CH, Easty DL: Br J Ophthalnol 1995;79:1078-1082. The authors present a review of the etiology, diagnosis, treatment, and outcome of 23 cases of Acunthamoeba keratitis presenting between 1985 and 1995 to a United Kingdom eye hospital Twenty-three patients (mean age, 31 years) presented over this period. Of the suffers 88%, had no previous history of ocular problems, and all were contact lens wearers. Sixty-seven percent were disposable soft lens wearers, and 91% of the patients presented in the 1990s. Forty-eight percent of the patients presented between January 1994 and February 1995 alone. Of the sufferers, 50% used a chlorine-based disinfectant system (18% used no
disinfectant, and others reported poor lens hygiene). Diagnosis was based on clinical appearance and laboratory findings. In 77% of cases, an incorrect initial diagnosis of a viral keratitis was made. Over the lo-year period, a decrease in diagnostic delay has been achieved. A total of 39% of the patient’s required penetrating keratoplasty to be performed. These were all cases with a lengthy period between presentation and treatment initiation. Seventy-eight percent of the sufferers had a final corrected acuity of 6/6 after medical/surgical intervention. Although Acanthamoeba keratitis, possibly associated with contact lens wear, would appear to be on the increase, advances in medical and surgical intervention and decreased diagnostic delay may provide successful treatment in the majority of cases. Both contact lens wear (especially disposable lens wear) and chlorine-based disinfectant systems are proposed as possible predisposing factors in Acunthumoeba keratitis. In the light of these findings, great care should be taken on the presentation of atypical keratitis in association with contact lens wear.
Successful Immunization Against Acunthamoeba Keratitis in a Pig Model. Alizadeh H, He Y, McCulley JP, et al.: Cornell 1995;14:180-186. Although free-living Acantharnoeba protozoa are common in the environment, and contact lens wear is a major risk factor of infection, the incidence of Acanthamoeba keraticis is relatively rare. This would suggest some form of widespread immune response-mediated protection in the general population. This may still leave a small group of nonimmune individuals at risk of infection. An animal model (pig) has been developed for the investigation of this infection. The pig is susceptible to Acunthamoeba keratitis in a way similar to that of the human. It is understood that 100% of normal pigs develop severe keratitis when infected via a parasite-laden contact lens. Using this model, the authors investigated the effects of prior ocular infection with Acanthamoeba trophozites or injections of parasite antigens either (a) intramuscularly; (b) subconjunctivally; or (c) intramuscularly and subconjunctivally, in an attempt to induce sustained immunity. Intramuscular inoculation alone and prior ocular infection alone gave no protection against pathologic response to future exposure. Subconjunctival exposure alone afforded protection in 5C% of cases. Combined subconjunctival and intramuscular inoculation afforded protection in 100% of cases tested. The results would suggest that it is possible to induce total protection against Acanthamoeba keratitis in an animal model that is similar to the human condition. Further work elucidating the immune response to Acanthamoeba antigens may extend our ability to prevent, detect, and treat this sight-threatening infection with greater accuracy and efficiency.
ICLC, Vol. 23, March/April
1996
79