Patrick C. Ho

The Problem of Bacillus Species Infection with Special Emphasis on the Virulence of Bacillus cereus

Although Bacillus cereus is an uncommon ocular pathogen, infection with it usually results in loss of the eye. Although previous reports have emphasized endogenous infection, our recent experience indicates the importance of B cereus infection following trauma. Management is hampered by ineffectiveness of current empirical antibiotic regimens. This microorganism is resistant to both the penicillins and the cephalosporins. Although B cereus is susceptible to gentamicin, our studies indicate that gentamicin by itself is inadequate to eradicate the infection. B cereus, however, is susceptible to clindamycin and combined therapy with gentamicin and clindamycin appears to offer the best approach. Early diagnosis is the key to successful treatment. We believe the clinical circumstances likely to lead to B cereus infection, as well as the manifestations of the disease itself, are sufficiently distinctive to alert the ophthalmologist to the possibility of this infection. Prompt recognition of the infection should allow institution of appropriate therapy before permanent structural changes occur.

An analysis of the incidence and risk factors of developing severe keratopathy in eyes after megavoltage external beam irradiation

OBJECTIVE To investigate the incidence and risk factors of developing severe keratopathy in eyes exposed to megavoltage external beam irradiation. DESIGN Retrospective noncomparative case series. PARTICIPANTS The authors evaluated 88 eyes of 88 consecutive patients who had received irradiation of an entire orbit during radiation therapy for nasopharyngeal carcinoma. Mean follow-up was 40 months (range, 24-106 months). INTERVENTION Slit-lamp biomicroscopic findings of the cornea after irradiation were categorized into four grades in accordance with a standard protocol. Grade 3 or above changes were defined as severe radiation keratopathy. MAIN OUTCOME MEASURES The incidence of severe radiation keratopathy was evaluated along with patients age, radiation dose, lacrimal shielding, and tumor involvement of the trigeminal nerve. RESULTS Severe radiation keratopathy developed in 32 patients. Mean latency was 15 months (range, 4-36 months). Its incidence increased from 0% after doses less than 59 Gy to 100% after doses greater than 70 Gy. Between 59 Gy and 69 Gy, the adverse factor was omission of lacrimal shield during radiation therapy (P < 0.01). CONCLUSION Radiation dose to the cornea is the most important factor in determining the outcome of radiation keratopathy. When the threshold dose is reached, visual prognosis is grave despite protection of the lacrimal gland. Clinical trials on newer strategies to treat ocular surfaces exposed to heavy irradiation are necessary.

Nd: YAG laser photodisruptors.

Commercial laser photocoagulators consist of: (1) a high power, short-pulse laser source, usually a Q-switched or mode-locked Nd:Y AG laser producing invisible nearinfrared radiation at 1064 nm; (2) an aiming/focusing laser system, using a continuous-wave He-Ne laser producing visible, red light at 632.8 nm; (3) a condensing lens that focuses the infrared treatment beam into a small focal spot at the working distance of the photodisruptor slit lamp; (4) an attachment system that connects the laser sources to the slit-lamp microscope to aim and focus the He-Ne laser (and thus the Nd:Y AG treatment beam) on target tissues. Basic principles, design, safety, and applications of photodisruptors are described elsewhere. I,2 In general, commercial photodisruptors may be differentiated on the basis of their: (1) pulse lengths, (2) aiming/focusing systems, and (3) attachment systems. 1 (1) Q-switched lasers produce single pulses or bursts of 1 to 9 pulses, each pulse of which is between 2 and 14 ns (l ns = 10-9 sec), depending on the commercial photodisruptor (Table 1). Mode-locked lasers produce a pulsetrain of seven to nine spikes over roughly a 30 ns interval. Each spike is 30 psec in duration (l ps = 10-12 sec). (2) With a single-beam focusing system, the operator moves the slit lamp forward and backward to minimize the size of a single red spot on the target tissue. With a doublebeam focusing system, the operator moves the slit lamp forward and backward until the two red spots fuse into

Severe Proliferative Vitreoretinopathy and Retinal Detachment: II. Surgical Results with Scleral Buckling

Prior to the era of vitrectomy, scleral buckling was used to treat 521 eyes with total retinal detachment and proliferative vitreoretinopathy (PVR) of various degrees of severity. The retina was reattached for at least six months in 46.9% of eyes; the anatomic success rate decreased with increasing severity of PVR. Within each grade of PVR, the reattachment rate was higher for eyes with smaller breaks than for eyes with larger breaks, and the prognosis was not worse when smaller breaks were found than when no breaks were found. The cumulative success rate rose with increasing number of reoperations. None of the anatomically successful cases had a final visual acuity of no light perception; 82.9% of them achieved a visual acuity of counting fingers or better. The prognosis for visual improvement after successful scleral buckling was unrelated to the preoperative severity of PVR. Severe intraoperative complications occurred in 5.0% of the eyes, all of which resulted in failure.

Fundus Contact Lenses for Closed Pars Plana Vitrectomy

Closed vitrectomy through the pars plana requires a corneal contact lens and operating microscope to visualize the surgical field in the deep vitreous. To maintain a clear view of the posterior vitreous, the contact lens must neutralize the refractive power of the cornea, permit view of the area with vitreoretinal pathology, allow corneal contact on rotation of the globe, and provide mechanisms to minimize the accumulation of blood or air bubbles between the contact lens and the cornea. A number of surgical contact lenses have been developed for pars plana vitrectomy over the past decade. I4 In general, they may be differentiated on the basis of their: (1) optical design, (2) anchoring mechanism on the cornea, and (3) irrigating device. ( 1) Corneal contact lenses for vitrectomy are usually made of plastic, glass, or quartz. While lenses exceeding 10 mm in diameter do not move freely over the corneal surface to permit observation of the peripheral fundus,5 smaller lenses are more prone to displacement by instruments.3 The posterior curvature is necessarily concave to neutralize the refractive power of the cornea, with a longer radius of curvature than that of the cornea to minimize the tendency for air bubbles or blood

Inhibition of Pathologic Retinal Neovascularization by a Small Peptide Derived from Human Apolipoprotein(a)

PURPOSE To evaluate the effect of KV11, a novel 11-mer peptide from human apolipoprotein(a), against retinal neovascularization and to study its penetration and the possible toxicity to the retina. METHODS Wound-healing, a modified Boyden chamber, and MTS assays were used to evaluate the effect of KV11 on the migration and proliferation of bovine retinal capillary endothelial cells (BRCECs) induced by vascular endothelial growth factor (VEGF) in vitro. The antiangiogenic effect of KV11 was also studied with a mouse model of oxygen-induced retinopathy. Then, FITC-labeled KV11 was injected into the vitreous of normal rabbits, the retinal penetration was determined by confocal laser-scanning microscope, and further confirmed by UPLC/MS analysis of KV11 in tissue extracts. Electrophysiological tests and histologic examinations were used to study the possible toxicity of KV11 against rabbit neuroretina after intravitreal administration. RESULTS KV11 inhibited VEGF-induced BRCEC migration but not proliferation and reduced the pathologic neovascularization in a mouse model, without affecting normal retinal vasculature. FITC-labeled KV11 appeared in the retina within 30 minutes after injection and diffused to all layers 3 hours later. The transfer of KV11 from the vitreous to the retina was confirmed by UPLC/MS data. Electrophysiologic tests and histologic examinations revealed no evident functional or morphologic abnormalities in rabbit neuroretina after KV11 injection. CONCLUSIONS It is concluded that the novel peptide KV11 is an effective inhibitor of retinal pathologic angiogenesis with a sufficient retinal penetration and a favorable safety profile and may provide a promising alternative for ocular antiangiogenic therapy.

Neovascular Glaucoma Developing after Uncomplicated Cataract Surgery for Heavily Irradiated Eyes

PURPOSE The purpose of the study was to evaluate the effect of cataract surgery and postoperative panretinal photocoagulation (PRP) on the development of neovascular glaucoma (NVG) in heavily irradiated eyes. PATIENTS AND METHODS The authors performed a retrospective study on the incidence of NVG in 90 eyes that had received megavoltage external beam irradiation at a retinal dose of 56 to 80 Gy and that had at least 48 months of follow-up. These eyes were categorized into different groups depending on whether cataract surgery or PRP was performed. Rates and proportions of NVG occurring in these groups were compared and analyzed with one-tailed Fishers exact test. RESULTS The incidence of NVG was significantly higher in patients who underwent cataract surgery without postoperative PRP (P < 0.01). Neovascular glaucoma did not develop in any patient who underwent cataract surgery and PRP. CONCLUSIONS Cataract surgery may accelerate the development of NVG in heavily irradiated eyes. Photoablation of ischemic retina is recommended before cataract surgery or soon thereafter if cataract density precludes laser treatment.

Proliferative Diabetic Retinopathy in Patients with Defects of Platelet Function

A 71-year-old woman had von Willebrands disease, an inheritable abnormality of platelet activity, and developed diabetic retinal neovascularization. A 59-year-old man had a myeoloproliferative disorder with thrombocythemia but may have had retinal changes before the development of his platelet dysfunction. The occurrence of diabetic proliferative retinopathy in patients with reduced platelet activity suggests that platelet induced microcirculatory abnormalities may not be required for neovascularization.

Low-vision aids for patients with suboptimal vision after closed vitrectomy for diabetic vitreous hemorrhage.

The use of low-vision aids to improve postoperative vision after successful closed vitrectomy for vitreous hemorrhage was evaluated in 30 diabetic patients. The distance vision improved with telescopic systems in 28 of 30 patients, whereas the near vision improved with microscopic systems in all cases. Patient acceptance of these low-vision aids was 50% for telescopic systems and 83% for microscopic systems.