Finite element modeling, validation, and parametric investigations of a retinal reattachment stent.

A new retinal reattachment surgical procedure is based on a stent that is deployed to press the retina back in place. An eye-stent finite element model studied the strain induced by the stent on retina. Finite element model simulations were performed for several stent geometric configurations (number of loops, wire diameter, and intraocular pressure). The finite element model was validated against experiment. Parametric studies demonstrated that stents could be successfully designed so that the maximum strain would be below permanent damage strain threshold of 2%.

Endoresection of the iris and ciliary body in epithelial downgrowth.

We present a case of epithelial downgrowth with intractable glaucoma after multiple intraocular surgeries. The eye was successfully managed with a pars plana approach. The iris and epithelial tissue over the ciliary body were removed with intraocular scissors and a vitrector combined with unipolar diathermy and endophotocoagulation. The use of moderate hypotensive anesthesia may have helped prevent intraoperative hemorrhage. During more than 3 years of follow-up, intraocular pressure ranged from 13 to 19 mm Hg, visual acuity was 20/80 with aphakic correction with a rigid gas-permeable lens, and there was no recurrence of epithelial downgrowth.

The adjunctive use of perfluoroperhydrophenanthrene (Vitreon) in diabetic vitrectomy.

OBJECTIVE: To evaluate the utility and efficacy of perfluoroperhydrophenanthrene in the management of retinal detachments secondary to severe proliferative diabetic retinopathy. PATIENTS AND METHODS: Forty consecutive patients with proliferative diabetic retinopathy and retinal detachments were entered into the study at nine participating clinical centers. Perfluoroperhydrophenanthrene (Vitreon) was used as an adjunct to pars plana vitrectomy and membranectomy. RESULTS: Preoperative diagnoses included combined traction and rhegmatogenous retinal detachments in 23 eyes (57.5%), traction retinal detachments in 13 eyes (32.5%), and recurrent rhegmatogenous retinal detachments in 4 eyes (10). Vitreous hemorrhage was present in 17 eyes (42.5%). Preoperative visual acuity ranged from light perception or hand motion in 28 eyes (70%) to 5/200 or greater in 12 eyes (30%). Vitreon was primarily used to flatten the retina following relaxing retinotomy in 12 eyes (30%), to displace subretinal fluid in a posterior-to-anterior direction without performing a drainage retinotomy in 15 eyes (37.5%), and to manage intraoperative complications such as iatrogenic tears in 8 (20%) and retinal dialysis in 5 eyes (12.5%). The retina flattened intraoperatively in all cases, facilitating administration of laser photocoagulation. Patients were followed for a minimum of six months (mean 13.2 months). At last follow up, the macula remained attached in 37 eyes (92.5%), including 31 (77.5%) in which the retina was totally attached. The retina remained detached in 3 eyes (7.5%). Visual acuity improved postoperatively in 20 patients (50%), was unchanged in 13 patients (32.5%), and worsened in 7 patients (17.5%). CONCLUSIONS: Perfluoroperhydrophenanthrene is a useful and effective intraoperative tool for the management of complex retinal detachments secondary to severe proliferative diabetic retinopathy.

Ocular syphilis and neurosyphilis in a patient with human immunodeficiency virus infection.

A patient who presented with severely decreased bilateral vision was found to have syphilis and neurosyphilis that responded well to a 14-day course of penicillin and prednisone. The patient tested positive for HIV, which can alter the natural course of syphilis, often making the diagnosis and treatment difficult. Conventional therapy for syphilis may not be effective in patients with HIV. Any patient with syphilis who is in a high-risk group should be tested for HIV; conversely, any patient with HIV should be tested for syphilis if signs or suspicions exist.

Effect of the secretin family of peptides on gastric emptying and small intestinal transit in rats.

We have compared the effects of the secretin family of peptides and their synthetic fragments on gastric emptying (GE) and small intestinal transit (SIT) using an unanesthetized rat model which simultaneously measures the GE and SIT of both solids and liquids. The meal consisting of 5% polyethylene glycol w/v, 5% Indian ink v/v and 20 non-digestible plastic beads was given intragastrically 10 minutes after the intraperitoneal injection of 0.5 ml of saline or peptides (2 and 5 micrograms/kg). Plasma secretin and the immunospecificity of secretin fragments were determined. In control rats, the t1/2 for the GE of both solids and liquids were 56 +/- 3.8 and 19 +/- 2.3 minutes, respectively. Liquids emptied faster than the solids and liquids travelled ahead of the solids in the intestine. Secretin (5 micrograms/kg) inhibited GE of both solids and liquids by 33-37%. Secretin delayed the SIT of the meal by approximately 35%. Fragments of secretin and of VIP had no effect on GE and SIT of both solids and liquids. The whole molecule of secretin was required to inhibit GE and to delay SIT of solids and liquids. Glucagon, PHI and growth hormone releasing factor (GHRF1-44) inhibited GE and SIT of both solids and liquids. For all peptides tested, the inhibition of SIT was proportional to the inhibition of GE suggesting that the prolongation of SIT was secondary to delayed GE. These observations indicate that the peptides of the secretin family inhibit GE and prolong SIT. Thus, the structural requirement required for the secretin family of peptides to effect their motor actions on the stomach is similar to that required for pancreatic enzyme secretion.