Thomas D. Lindquist

Treatment of Acanthamoeba keratitis.

PURPOSE To review the available treatment modalities for Acanthamoeba keratitis and to assess the most effective regimens. METHODS The efficacy of therapeutic modalities and chemotherapeutic agents used in the treatment of Acanthamoeba keratitis was reviewed. Potential synergistic or additive drug interactions were documented both in vitro and in vivo. RESULTS Early diagnosis of Acanthamoeba keratitis plays a crucial role in successful medical treatment. The cationic antiseptic agents, chlorhexidine and polyhexamethylene biguanide (PHMB) have the lowest minimal amoebicidal concentrations. Synergistic effects are seen when used with pentamidine, and additive effects are seen with propamidine or neomycin. Penetrating keratoplasty should be deferred if at all possible until a medical cure has been achieved. CONCLUSION Early diagnosis and wide epithelial debridement are important elements in the successful treatment of Acanthamoeba keratitis. Recommended therapy would include the cationic antiseptic agents, chlorhexidine or PHMB in combination with propamidine isethionate and neomycin as part of triple therapy. Surgical intervention should be avoided until a medical cure has been achieved.

Implantation of a Posterior Chamber Lens Without Capsular Support During Penetrating Keratoplasty or as a Secondary Lens Implant

We have devised a technique to fixate a posterior chamber lens in the ciliary sulcus when no posterior capsular support exists. Our short-term follow-up of 22 eyes with lenses thus fixated has shown these eyes to be quiet and to have good pupillary motility after at least 3 months. We believe this new technique is a significant advancement in corneal and anterior segment surgery.

Effects of Povidone-Iodine Chemical Preparation and Saline Irrigation on the Perilimbal Flora

PURPOSE To analyze the effects of 5% povidone-iodine preparation and saline irrigation on the species composition of perilimbal flora. METHODS Cultures were taken from the perilimbal conjunctiva in 100 eyes before preparation for ophthalmic surgery, after instillation of povidone-iodine solution, and after saline irrigation. RESULTS Bacteria were isolated in 75% of eyes before preparation, in 28% after povidone-iodine instillation, and in 24% after saline irrigation. Fifty-one culture-positive eyes became negative with povidone-iodine, while only four culture-negative eyes became culture-positive (P < 0.001). The number of eyes yielding coagulase-negative staphylococci, Staphylococcus aureus, and Propionibacterium were significantly decreased after povidone-iodine instillation. Twenty-three culture-positive eyes became negative after saline irrigation, while 19 culture-negative eyes became culture-positive (P > 0.25). CONCLUSION Povidone-iodine solution is effective in reducing bacterial recovery from the perilimbal conjunctiva, where most incisions for intraocular surgery occur. Saline irrigation after povidone-iodine preparation has no significant effect.

Surgical correction of postoperative astigmatism.

The photokeratoscope has increased the understanding of the aspheric nature of the cornea as well as a better understanding of normal corneal topography. This has significantly affected the development of newer and more predictable models of surgical astigmatic correction. Relaxing incisions effectively flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. The net change in spherical equivalent is, therefore, negligible. Poor predictability is the major limitation of relaxing incisions. Wedge resection can correct large degrees of postkeratoplasty astigmatism, Resection of 0.10 mm of tissue results in approximately 2 diopters of astigmatic correction. Prolonged postoperative rehabilitation and induced irregular astigmatism are limitations of the procedure. Transverse incisions flatten the steeper meridian an equivalent amount as they steepen the flatter meridian. Semiradial incisions result in two times the amount of flattening in the meridian of the incision compared to the meridian 90 degrees away. Combination of transverse incisions with semiradial incisions describes the trapezoidal astigmatic keratotomy. This procedure may correct from 5.5 to 11.0 diopters dependent upon the age of the patient. The use of the surgical keratometer is helpful in assessing a proper endpoint during surgical correction of astigmatism.

Visual results following vitreous loss and primary lens implantation

ABSTRACT Implantation of an intraocular lens following vitreous loss at cataract surgery is a controversial decision. To address this issue, we retrospectively identified all cases performed at the University of Minnesota in the last three years that had either a posterior or an anterior chamber lens placed following anterior vitrectomy. Twenty patients had a posterior chamber lens implant; 14 had follow‐up longer than six months. All these patients achieved 20/40 or better visual acuity, although one patient had a retinal detachment. Of the six patients with an anterior chamber lens implant, four achieved 20/40 or better acuity and two achieved 20/50 acuity with follow‐up of six months; one patient had a retinal detachment. This review demonstrates that with a meticulous anterior vitrectomy, good visual results can be achieved, although the risk of retinal detachment is higher than in uncomplicated cases.

Bilateral Angle-Closure Glaucoma Associated with Uveal Effusion: Presenting Sign of HIV Infection

A 40-year-old homosexual man presented with acute myopia and bilateral angle-closure glaucoma. Recognition of an anterior chamber configuration of a modestly shallowed central chamber with marked peripheral shallowing clinically suggested uveal effusion. B-scan echography provided definitive, confirmatory evidence of diffuse choroidal thickening with ciliochoroidal effusion. Treatment with aqueous suppressants, cycloplegics, and topical steroids resulted in complete resolution of the angle closure and reversal of induced myopia. The patient, who was systemically well without signs of AIDS or AIDS-related complex, was later tested and found to be serologically-positive for the human immunodeficiency virus.

A Cadaveric Eye Model for Practicing Anterior and Posterior Segment Surgeries

OBJECTIVE To develop a simple and effective model for practicing anterior and posterior segment surgeries. DESIGN A Lander wide-field keratoprosthesis was used as an artificial cornea in human cadaver eyes. RESULTS The keratoprosthesis provided a tight seal which maintained the anterior chamber. Continuous curvilinear capsulorrhexis, hydrodissection, and phacoemulsification of the cadaveric lens followed by insertion of a foldable intraocular lens into the capsular bag were performed through a standard three-planed scleral tunnel incision. Pars plana vitrectomy, using the standard three-port approach, was performed. Panretinal photocoagulation was performed using a slit-lamp laser delivery system and a Rodenstock lens. CONCLUSIONS This eye model very closely simulates the tactile behavior of a living eye and may be useful as a realistic practice and teaching platform for a wide variety of anterior and posterior segment surgical procedures, including laser photocoagulation.

Treatment of Phacolytic Glaucoma with Extracapsular Cataract Extraction

The treatment of choice for phacolytic glaucoma has been intracapsular cataract extraction (ICCE). The current study was undertaken to determine the efficacy of extracapsular cataract extraction (ECCE) as a definitive treatment for phacolytic glaucoma. Five cases of phacolytic glaucoma that occurred between 1984 and 1986 were studied after a retrospective chart review; ECCE (with placement of a posterior chamber intraocular lens [PC IOL]) was performed without complication and was curative in all five eyes. All patients (100%) maintained intraocular pressures (IOPs) of less than 20 mmHg, without medical therapy. The best-corrected visual acuity for all cases was 20/50 or better (80%, greater than or equal to 20/40) with 5 months to 3 years follow-up. These results suggest that ECCE is an effective alternative for the treatment of phacolytic glaucoma and allows surgeons the freedom to choose the procedure with which they are most comfortable. Additionally, implantation of a PC IOL is a safe and efficacious procedure in restoring visual function in these patients.

Scleral ectasia secondary to Acanthamoeba keratitis.

An unrecognized case of Acanthamoeba keratitis became quiescent after prolonged scleritis, resulting in a central corneal scar with extensive scleral ectasia. Twenty-one months after the onset of the sclerokeratitis, a penetrating keratoplasty was performed. Acanthamoeba cysts were found in the host corneal button. The corneal transplant has remained thin and clear for 2 1/2 years following surgery. Acanthamoeba keratitis extending to the limbus may become self-limited due to immunologic mechanisms available at the limbus, which do not appear to be active within the cornea itself. However, the prolonged inflammatory reaction manifesting as scleritis may result in extensive scleral ectasia.

Acanthamoeba-Contaminated Hydrogel Contact Lenses

Acanthamoeba keratitis has frequently been associated with contact lens use. In this study, contaminated hydrogel contact lenses of patients were subjected to disinfection by thermal hydrogen peroxide and chemical (quaternary ammonium) systems. New hydrogel contact lenses contaminated by incubation on Acanthamoeba polyphaga plates were similarly subjected to the disinfection systems described above. Thermal disinfection was universally effective in eradicating acanthamoeba, whereas hydrogen peroxide and quaternary ammonium disinfection were ineffective. Scanning electron microscope photomicrographs suggest that acanthamoeba may adhere to surfaces of hydrogel contact lenses. These findings have significant implications for soft contact lens users.