Protective ocular mechanisms in woodpeckers.

AIMS: Woodpeckers possess mechanisms protecting the eye from shaking/impact. Mechanisms available to woodpeckers but not humans may help explain some eye injuries in Shaken Baby syndrome (SBS). METHODS: Gross dissection and histologic examination of eyes and orbits of seven woodpeckers. RESULTS: All birds showed restricted axial globe movement due to the tight fit within the orbit and fascial connections between the orbital rim and sclera. The sclera was reinforced with cartilage and bone, the optic nerve lacked redundancy, and the vitreous lacked attachments to the posterior pole retina. CONCLUSIONS: Woodpecker eyes differ from human infants by an inability of the globe to move axially in the orbit, the sclera to deform, and the vitreous to shear the retina. These findings support current hypotheses that abusive acceleration-deceleration-induced ocular injury in human infants may be related to translation of vitreous within the globe and the globe within the orbit. The woodpecker presents a natural model resistant to mechanical forces that have some similarity to SBS.

[Therapeutic penetrating keratoplasty for microbial keratitis].

BACKGROUND: Microbial keratitis is a potentially sight threatening disease. Most cases respond well to antimicrobial therapy. However, in cases that progress despite intensive medical therapy, an urgent therapeutic penetrating keratoplasty (TPKP) is required. AIM: To evaluate the indications and results of TPKP in Israel. METHODS: A retrospective study reviewed the TPKP performed at the Goldschleger Eye Institute, Sheba Medical Center, between 1990-2003. The study included 18 cases of at least one-year follow-up. RESULTS: The indications for TPKP included severe infectious keratitis unresponsive to medical treatment in 33% of the patients and severe corneal destruction in 66% of them. The infectious keratitis was diagnosed as bacterial keratitis in 44% of the patients, unidentified pathogen in 39%, mycotic in 11% and acanthamoeba in 6% of the patients. Risk factors in the patients with microbial keratitis requiring TPKP included: previous ocular disease in 39%, previous ocular surgery in 66%, systemic disorders in 28% and ocular risk factors in 28% patients. TPKP was successful in bacterial and acanthamoeba keratitis as far as the transparency of the graft and elimination of the infection and improvement of visual acuity. However, TPKP failed in mycotic and unidentified keratitis. The risk factors for failure included: previous ocular disease or surgeries, systemic disorders or large corneal grafts. CONCLUSIONS: Therapeutic penetrating keratoplasty is an important and effective therapeutic tool for intractable bacterial and acanthamoeba keratitis. Prognostic factors for graft success include lack of ocular disease or previous surgeries, lack of systemic disorders or small corneal graft size.

Evaluation of superior rectus muscle attachment following hang-back recession in rabbit eyes.

PURPOSE: The hang-back suture technique has been advocated to decrease the risk of scleral perforation during strabismus surgery. In this study, we evaluated the muscle insertion site in rabbits 4 weeks after a hang-back recession was performed. METHODS: Twenty-five eyes of 13 rabbits underwent hang-back recessions of between 5 and 8 mm of the superior rectus muscle. Four weeks later, the attachment sites were examined. RESULTS: Four weeks following the surgery, 14 muscles (n=25, 56%) were anteriorly displaced. In the 5 mm recession group, one muscle was anteriorly displaced (n=7, 14.3%). In the 6 mm recession group, 50% of the muscles recessed were displaced anteriorly (n=8). The 7 mm hang-back recession group demonstrated forward displacement in five muscles operated (n=6, 83%) and in the 8 mm recession group, all four muscles (100%) were anteriorly displaced. The magnitude of displacement was positively correlated to the amount of the hang-back recession performed (Pearson correlation p<0.001). CONCLUSIONS: Anterior displacement of muscles using the hang-back technique in the rabbit eye is unacceptably high and occurred in 56% of the cases. A positive, statistically significant correlation exists between the amount of recession performed and the number of muscles displaced from their new insertion. Therefore, when performing large recessions using the hang-back technique displacement should be anticipated.

Sclerotomy using needle puncture and subconjunctival injection of mitomycin C.

OBJECTIVE: To explore the possibilty of creating a temporary sclerotomy using a 26-gauge needle and sustaining its patency by injectiong 0.1 mL of 0.1 mg/mL of mitomycin C (MMC). ANIMALS AND METHODS: Twenty-four New Zealand white rabbits were randomized into 3 groups. In the test group, puncture was performed using 26-gauge needle penetrating the anterior chamber at the limbus, and 0.1 mg/mL MMC were injected subconjunctivally. In the control group, a puncture was performed in the same fashion and in the MMC group, MMC only was injected subconjunctivally. Intraocular pressure (IOP) was measured prior to surgery and at days 1, 3, 7, 10, 14, 21, and 28. RESULTS: The mean intraocular pressure in eyes that underwent puncture with application of MMC was significantly lower than the IOP in the eye at all measurements up to and including day 21. In the puncture group, pressure was significantly lower than in the fellow eye only at day 3. No significant pressure reduction was observed at any measurement interval in eyes treated with MMC only. CONCLUSION: This simple technique of subconjunctival puncture of the limbus combined with application of MMC was effective in lowering IOP in rabbits. This may serve to attain a temporary filter in patients who need strict short-term pressure control.

The reculture technique: individualizing the treatment of Acanthamoeba keratitis.

PURPOSE: To assess the efficacy of three drugs in different concentrations against different strains of Acanthamoeba using the reculture technique. METHODS: Cysts and trophozoites were immersed in five separate solutions. The solutions administered included 0.1% and 0.02% polyhexamethylene biguanide (PHMB), 0.1% and 0.02% chlorhexidine, and propamidine isethionate (Brolene). Readings took place after 1, 5, and 24 hours. The cysts and trophozoites were then recultured for an additional period of 48 hours. An effective drug was defined as a medication that inhibited any growth of trophozoites using the reculture technique. RESULTS: Chlorhexidine at concentrations of 0.1% and 0.02% was the only effective drug against all five strains of Acanthamoeba examined, and no trophozoites were detected on plates immersed with this agent. Only 0.1% chlorhexidine was effective in destroying all cysts in the five strains examined. CONCLUSION: We found that 0.02% chlorhexidine was efficient in irradicating all trophozoites and 0.1% chlorhexidine was effective in eradicating all cysts in the samples we examined. Therefore, it may be possible that 0.02% chlorhexidine is a good initial treatment in amoebic keratitis. Sensitivity testing, then, may be performed using the reculture technique and specification of therapy can be made accordingly.

Strabismus surgery using the adjustable suture technique.

BACKGROUND AND OBJECTIVE: To determine the results of adjustable suture technique used in horizontal muscle surgery. MATERIALS AND METHODS: Seventy-eight charts of patients who underwent strabismus surgery between the years 1993 and 1995 were examined retrospectively. The study included 35 cases of esotropia (ET), and 43 cases of exotropia (XT). The results of strabismus surgery were measured and compared 1 day after adjustment; the final results between 6 and 24 months after the surgical procedure. RESULTS: Adjustment was required in 39% of all patients. The highest rate of adjustment was required in patients who underwent monocular surgery for XT (51%), and the lowest rate of adjustment was undertaken in patients who underwent monocular surgery for ET (16%). Mean changes in the angle of deviation between 1 day after surgery to the last follow up was 2.2 prism diopters (delta) (+/-11.2 delta) for cases of esotropia, and 4.6 delta (+/-8.7 delta) for exotropia. The most significant drift was found in patients with XT who underwent binocular surgery 6.8 delta (+/-0.9 delta) and the smallest drift was found in patients with ET who underwent binocular surgery 5.2 delta (+/-5.6 delta). CONCLUSION: Esotropic and exotropic patients have a tendency to drift towards their original deviation postoperatively. It is possible, therefore, that mild overcorrection in the early postoperative period will result in better long-term results.

Intraocular pressure increments after cataract extraction in glaucomatous eyes with functioning filtering blebs.

BACKGROUND AND OBJECTIVE: The effects of cataract extraction on intraocular pressure (IOP) were studied in glaucoma patients who had previously undergone trabeculectomy. PATIENTS AND METHODS: The files of 22 patients with 25 glaucomatous eyes with functioning filtering blebs who underwent cataract extraction were retrospectively reviewed. All patients had undergone pretrabeculectomy examination and had at least 18 months of follow-up after cataract surgery. Visual acuity, IOP, status of the filtering bleb, and the number of medications applied were recorded. RESULTS: The mean increase in IOP was 3.63 mm Hg, 3.84 mm Hg, 5.4 mm Hg, and 2.8 mm Hg at 3, 6, 12, and 18 months after cataract extraction, respectively. This elevation was statistically significant 3 months postoperatively (P < .001) and remained relatively constant thereafter. The postoperative IOP was still significantly lower than the pretrabeculectomy IOP (P < .001). CONCLUSIONS: Cataract extraction through corneal incisions in patients with functioning filtering blebs is followed by an increase in IOP. Cataract surgery in these patients does not neutralize the pressure-lowering effect achieved by the trabeculectomy, but it tends to elevate the post-trabeculectomy baseline pressure.