Rabbit Streptococcus pneumoniae keratitis model and topical therapy.

PURPOSE: To develop a model for experimental Streptococcus pneumoniae keratitis and to evaluate the chemotherapeutic efficacy of 12 common topical antibiotics in vivo. METHODS: Five-hundred (CFUs of log-phase S. pneumoniae were injected into the central corneal stroma of 36 eyes of 18 rabbits. After 0, 4, 8, 16, 24, and 48 hours, the in vivo growth was assayed as the CFU per cornea. Epithelial removal (to promote antibiotic entry and mimic human keratitis) was evaluated. Disc or tube dilution verification of the sensitivity or resistance of three S. pneumoniae strains was performed: a penicillin sensitive ("S"), an intermediate sensitive ("I"), and a resistant ("R") strain. Keratitis was established with S. pneumoniae "S" in 65 eyes, S. pneumoniae "I" in 107 eyes, and S. pneumoniae "R" in 78 eyes. Sixteen hours later, control corneas were harvested and the epithelium removed from treatment corneas. Every half hour saline, penicillin, gentamicin, bacitracin, ciprofloxacin, ofloxacin, erythromycin, vancomycin, ceftriaxone, cefotaxime, or chloramphenicol was applied for 5 hours. One hour later CFUs/cornea were assayed. RESULTS: After 24 hours, S. pneumoniae "S" and "I" had proliferated to 9.18+/-6.65 x 10(6) CFUs and 9.26+/-6.90 x 10(6) CFUs. Epithelial removal at 16 hours was not significant. The in vitro antibiotic sensitivity was as expected. However, in vivo, penicillin, gentamicin, or cefazolin sterilized S. pneumoniae "S." S. pneumoniae "R" responded best to fortified gentamicin with or without vancomycin; all others antibiotics were significantly less effective (P < 0.001). CONCLUSIONS: A small intracorneal S. pneumoniae inoculum in rabbit corneas grew and was maintained for 24 hours (with epithelial removal) to provide a model for testing antibiotic sensitivity in vivo. Topical penicillin is best for treating keratitis from penicillin-sensitive S. pneumoniae, whereas topical gentamicin or a combination of gentamicin and vancomycin was most effective against penicillin-resistant S. pneumoniae.

Tonometer utilization, accuracy, and calibration under field conditions.

A field survey conducted in 94 ophthalmologists' offices in our immediate area assessed the accuracy of tonometers in daily use. One hundred eighty-five instruments were examined: 127 were slit lamp mounted, 48 were hand held, and 10 were noncontact devices. Nineteen percent of applanation tonometers were outside the manufacturers' specifications (1 mm Hg of the calibration) and 4.5% were more than 2 mm Hg in error. The error was constant across the scale. Hand-held applanators were less accurate than those on slit lamps (P less than .02); the latter demonstrated an association between accuracy and age (P less than .05) and heavier use (P less than .01). Annual recalibration was performed in 86% of instruments. Those practitioners who themselves performed the calibration had the most accurate instruments. Less than 15% knew how to perform the calibration check.

Comparison of topical ciprofloxacin to conventional antibiotic therapy in the treatment of experimental Pseudomonas aeruginosa keratitis.

We evaluated the efficacy of topical ciprofloxacin (3.0 mg/ml) in the treatment of experimental Pseudomonas aeruginosa keratitis in 60 rabbits. We compared ciprofloxacin treatment with double drug therapy consisting of tobramycin (13.6 mg/ml) plus polymyxin B (25,000 U/ml) or carbenicillin (6 mg/L). Two strains of P. aeruginosa were used. One was a strain well characterized for use in experimental Pseudomonas keratitis (ATCC organism 27853); the second was an organism from a patient with a Pseudomonas corneal ulcer. Rabbits were treated for 16 h, after which the corneas were excised, homogenized, and plated serially for residual colony-forming units. Both organisms responded significantly better to topical off-the-shelf ciprofloxacin than to therapy with two conventional antipseudomonal fortified antibiotic drugs (p < or = 0.0001).

Stereoacuity and depth perception decrease with increased instrument magnification: comparing a non-magnified system with lens loupes and a surgical microscope.

PURPOSE: To evaluate the effect of instrument magnification used in eye surgery on stereoacuity and depth perception. METHODS: Twenty-one subjects (10 clinical ophthalmologists familiar with loupes and operating microscopes and 11 non-ophthalmologists) with normal near vision and stereoacuity were tested with the Randot Stereotest viewed unmagnified, with a 4x loupes (450 mm focal length), and with a 16x operating microscope. RESULTS: Total scores: 8 errors in 210 test steps with the unmagnified observations, 25/210 with loupes, and 30/210 with the microscope. The statistical differences in these scores were "statistically highly significant" for all three tests (p = 0.002); and "significant" for the unmagnified versus loupe (p = 0.007) and unmagnified versus microscope (p = 0.002). Test viewing through the microscope, the greatest errors occurred (total errors = 1840 seconds of arc), less with the loupes (total 1150") and least without magnification (total 220"). Errors and scores for 10 experienced ophthalmologists were no different (p > or = 0.55, p = 1.00) from the 11 non-ophthalmologist subjects. CONCLUSIONS: Stereoacuity and depth perception decrease when viewing a test target with loupes or with a microscope, with the effect worsening as magnification increases. Familiarity with the magnifying equipment did not improve stereoacuity.

Lidocaine-prilocaine cream for local-anesthesia chalazion incision in children.

BACKGROUND: Chalazia are not uncommon in children. If conservative therapy for them fails, incision and drainage are necessary and usually require a general anesthetic, which increases costs and risks. PATIENTS AND METHODS: Five children (3 to 8 years old) had a eutectic mixture of lidocaine and prilocaine applied to the skin of the eyelid for 1 hour. Then local anesthetic was injected into the same site. RESULTS: The local anesthetic injection was painless, permitting successful incision and drainage in all cases. CONCLUSION: Lidocaine-prilocaine cream permits local anesthetic injection into the eyelids, facilitating office-based management of chalazia in children.

Mechanized keratomicropigmentation: corneal tattooing with the blepharopigmentor.

BACKGROUND AND OBJECTIVE: A mechanized micropigmentor with a triple prong tip was used to tattoo two corneas for cosmetically unacceptable blemishes. PATIENTS AND METHODS: Two adult patients with cosmetically disfiguring corneal blemishes in sightless eyes requested cosmetic improvement. With a mechanized micropigmentor, appropriate pigment was directly inoculated through the epithelium. RESULTS: After 2 and 3 years of follow-up, respectively, there have been no complications and there has been minimal fading. CONCLUSION: This mechanical device facilitates many more penetrations to introduce pigment, with a more uniform depth than can be achieved by freehand methods.

Hook and loop fastener on loose prisms assists in measuring ocular deviation.

It is difficult to hold a pair of loose prisms in one hand. Doing so can lead to inaccuracy, which worsens with large-angle exotropia or vertical deviations. The authors applied a self-adhesive hooked Velcro (Velcro Sticky Back Tape, Velcro USA Inc., Manchester, NH) strip to the base and the top of loose prisms. They applied the complementary looped Velcro to a wooden bar. As a result, a pair of prisms could be suspended horizontally and/or vertically while being held in one hand. Forty consecutive patients undergoing strabismus surgery without adjustable sutures were retrospectively studied to evaluate the accuracy of this method. Clinical use confirmed its ease and convenience. Of 19 patients with exotropia and 15 patients with esotropia (mean ages 41.9 and 15.7 years, respectively; mean deviations 44.7 and 49.8 D, respectively), 4 patients with abducens paralysis, and 2 patients with trochlear palsies, 1 surgery achieved less than 10 D of residual deviation in all but 2 (5.9%). This simple, inexpensive system can assist with the clinical evaluation of ocular deviation.

Salvaged viscoelastic reduces irrigation frequency during cataract surgery.

A more viscous solution may decrease the need for frequent irrigations to maintain a clear cornea during cataract surgery. Fifty-four consecutive cataract patients were prospectively randomized to receive a drop of viscoelastic or saline on the cornea at the start of surgery. The surgical scrub nurse was instructed to irrigate only when the cornea appeared hazy or at the surgeon's request. The number of irrigations, ultrasound time and energy, and surgery times were compared using the Student's t test. Only one ampoule of viscoelastic was used for each case. When the patients who received viscoelastic were compared with the patients who received saline, the mean numbers of irrigations were 2 and 18, whereas the mean numbers of irrigations per minute were 0.17 and 1.21, highly significant (P < .0001) differences. The duration of surgery, ultrasound time, and ultrasound energy were less with viscoelastic, but were not statistically significant. Viscoelastic on the cornea reduces the frequency of irrigation without increasing cost.

Open drops in ophthalmology offices: expiration and contamination.

OBJECTIVE: To determine the relationship between eye drop use and contamination rate in ophthalmology offices. DESIGN: Following permission request, open bottles were examined and the nozzle tip and one drop of content was cultured on solid media. OUTCOME MEASURES: Drug category, volume, weight compared to full, clean legible label, expiration date; 2 or more bacterial colonies along the inoculation site. RESULTS: In 18 offices, of 1,485 open bottles (mean 12.2, range 4 to 23 per lane) on average 19.8% (range 0% to 88%) were expired (16.2 of 82.5 bottles per office). The frequency of occurrence (%) and expiration (%E) were 40.3% cycloplegics (19.4%E); 16.4% glaucoma (33.7%E); 10.8% anesthetics (8.8%E); and 4% steroids (8.8%E; or 42.2%E including one outlier). Most likely expired were glaucoma (P < 0.001); small 2-3 ml (P < 0.02), nearly empty (P < 0.05), or dirty (P < 0.001) bottles. Only one (5 ml cyclopentolate, not expired) grew a Micrococcus (0.07%). CONCLUSIONS: Drops in ophthalmology offices may be expired but are not contaminated.

The photic sneeze reflex and ocular anesthesia.

BACKGROUND AND PURPOSE: Intravenous sedation to minimize discomfort from local anesthetic injection has many potential complications including severe involuntary sneezing (i.s.). This prospective study evaluates the occurrence of i.s. and a history of photic sneezing (p.s.). METHODS AND MATERIALS: All patients receiving local anesthesia (retrobulbar or periocular injections) after intravenous thiopentone for eye surgery during eight months were asked about p.s. and observed for i.s. RESULTS: The 557 patients (40% males) had a mean age of 69.9 years and 14% recalled p.s. (29.5% males). I.s. developed in 5.2% of the 557. Only 7.6% of those with p.s. developed i.s. After periocular injections 23.8% developed as compared to 4.5% after retrobulbar injections. (P < 0.001). There was no relationship between p.s. and i.s. (p = 0.43). CONCLUSION: I.s. is not linked to p.s., with males and females at equal risk for either. I.s. is more common after periocular injections.

The effect of vehicle on corneal penetration of triturated ketoconazole and itraconazole.

BACKGROUND AND OBJECTIVES: Triturated (crushed and suspended) ketoconazole has been recommended for the treatment of fungal keratitis when commercial antifungal eyedrops are unobtainable. The authors evaluated the in vivo corneal stromal concentration with different vehicles in the eyes of adult rabbits. MATERIALS AND METHODS: Ketoconazole and itraconazole tablets were triturated to 20 mg/ml in four vehicles: polyvinyl alcohol (PVA), boric acid, olive oil, and balanced salt solution (BSS). Six eyes (deepithelialized for better penetration) received one drop every 15 minutes for 2 hours. A yeast overlay bioassay of extracts determined the stromal concentration. RESULTS: Itraconazole in BSS, olive oil, PVA, and boric acid produced inhibition zones of 17.3, 15.6, 15.4, and 13.2 mm, respectively. Ketoconazole produced inhibition zones of 35.9, 39.4, 41.8, and 44.7 mm, respectively. From a standard curve, the concentrations of ketoconazole in tissue were 512, 773, 1221, and 1492 micrograms/g, respectively. CONCLUSION: The vehicle that is used to triturate antifungals affects the tissue concentration. This may have an impact on fungal keratitis therapy.

Simple adaptor using a Zeiss observer tube on a Nikon slit lamp.

A simple adaptor was manufactured to allow fitting of a Zeiss beam splitter and observer tube onto a Nikon slit lamp YAG laser. No noticeable optical or mechanical problems have been experienced with this cost-saving device.

Indirect micro-ophthalmoscopy: intraoperative binocular indirect ophthalmoscopy with the operating microscope.

A hand-held indirect lens and an operating microscope can provide a view of the fundus similar to that provided by the usual binocular indirect ophthalmoscope headpiece. The only modification required is that the working distance must be increased to allow the microscope to be focused on the aerial image created by the hand-held lens. This technique provides a cost-effective means of retinal examination in preparation for intraocular lens implantation. Also, the view of the fundus it provides when complications such as choroidal hemorrhage or lens nucleus dislocation occur, facilitates appropriate management. It also can be used during posterior segment procedures such as foreign body removal, posterior vitrectomy, and retinal detachment repair. The advantages of this method include the possibility of using the microscope's zoom capability to provide greater magnification, and beam splitters for video or still-camera documentation of the findings during examination under anesthesia.

Modifying a Polaroid camera for close-up documentation.

A standard plus-three-diopter trial lens held in front of the objective lens of an inexpensive Polaroid camera produces close-up photographs of acceptable quality. This simple technique can be used to inexpensively document indications for plastic surgery and provide medicolegal documentation. The 23-millimeter-diameter trial lens provided acceptable resolution, but reduced depth of field; it must be well-centered to avoid vignetting.

Improving the sensitivity of the OKP visual field screening test with a blue stimulus on a dark background.

The standard oculokinetic perimetry test (OKP) was modified to present a light blue stimulus on a dark background (MOKP) to determine whether the sensitivity and specificity for detecting glaucomatous visual field loss could be improved. Thirty-five adult glaucoma patients (70 eyes) self-administered both tests and the results were correlated with the loss of retinal sensitivity on the Octopus IV program 38. The MOKP detected 18% more true scotomatous loci (more than 15 dB loss of attenuation) than the standard OKP (p < 0.0001). The gain was due to 37% fewer false negatives (p < 0.0001), but with a doubling of the false positives rate (p < 0.049). With a disease prevalence of approximately 2%, the MOKP and OKP would respectively miss 15% or 30%, and include 14 or 9 normals for each diseased individual. This relatively simple modification may further improve the OKP for detecting glaucoma.

Delayed subretinal fluid absorption after pneumatic retinopexy.

Eight of 38 eyes consecutively treated with pneumatic retinopexy were found to have delayed subretinal fluid absorption (DSRFA). In six of eight eyes, a shallow pocket of loculated fluid developed with small subretinal pigment precipitates, possibly a unique feature associated with pneumatic retinopexy. Although loculated DSRFA may not affect the anatomic success, poor visual outcome can result if the macula is involved (4 eyes). Loculated submacular DSRFA may cause bothersome postoperative symptoms, because its resolution may be prolonged for months. Factors found significantly associated with DSRFA were subretinal precipitates and heavy cryotherapy. Demarcation lines, dependent subretinal fluid by the macula, long duration of detachment, and phakic status were factors more frequently found in eyes with than without DSRFA, although the correlations lacked statistical significance. A detailed description of loculated DSRFA after pneumatic retinopexy not found in the literature is presented.

Adjustment of single continuous suture to control astigmatism after penetrating keratoplasty.

The presence of high amounts of regular and irregular astigmatism after penetrating keratoplasty has been a major challenge for corneal surgeons. We have devised a technique of suture adjustment which redistributes the tension in a single continuous 10-0 nylon suture according to keratometric findings and overcomes some of the limitations of other published methods for reducing penetrating keratoplasty astigmatism. Suture adjustment is performed at the slit-lamp microscope using topical anesthesia, from as early as the first postoperative day. The effects are controllable, reversible, stable, and can achieve relaxation or tightening of any meridian. Of 330 consecutive eyes undergoing penetrating keratoplasty, 205 required and underwent one or more suture adjustments. The mean keratometric astigmatism after suture adjustment was 2.87 D (SD = 1.87), compared to a preceding consecutive series of 136 eyes without suture adjustment with 4.80 D (SD = 3.13) mean astigmatism (P less than 0.0001). This effect persisted even when the suture had to be removed (P less than 0.0001). Infection did not occur. Only five eyes (2.4%) experienced a broken suture, which was readily spliced. We recommend adjustment of a single continuous suture, when moderate to severe astigmatism is present after a penetrating keratoplasty.