Intraocular pressure fluctuations during scleral buckling surgery

PURPOSE

The purposes of this study are to measure real-time intraocular pressure (IOP) during scleral buckling and to determine the effects of elevated IOPs on ocular perfusion.

PATIENTS AND METHODS

A standard 4-mm, 20-gauge infusion cannula was inserted through the pars plana, connected to a standard hemodynamic monitoring unit with an electronic pressure transducer, and calibrated. The authors measured real-time IOP in 20 eyes undergoing scleral buckling surgery for primary rhegmatogenous retinal detachments and determined the IOP required to close the central retinal artery. Pressure measurements were read from the monitor videoscreen intraoperatively and from a continuous paper tracing postoperatively.

RESULTS

The patients ranged in age from 24 to 88 years (mean, 59.7 years). The highest IOP elevations occurred during scleral depression and cryopexy, ranging up to 210 mmHg (mean, 116 mmHg). Pressures at which the central retinal artery closed ranged from 48 to 110 mmHg (mean, 79.2 mmHg). Manipulations of the globes caused IOPs greater than the central retinal artery perfusion pressures in 13 of the 20 patients. The duration of pressures in excess of the central retinal artery perfusion pressure ranged from 6 to 402 seconds (mean, 118.8 seconds). There were no intraoperative or postoperative complications from the infusion cannula.

CONCLUSIONS

Conventional scleral buckling surgery causes wide fluctuations in IOP and may impair ocular perfusion. Additional studies are needed to determine the long-term consequences of these pressure elevations.

Current patterns of intraocular gas use in North America

A 1987 survey of 365 members of the Retina and Vitreous societies revealed that use of long-acting intraocular gases was both widespread and frequent. However, despite the expanded use of intravitreal gases and the stated intention of the Food and Drug Administration to approve premarket applications for use of sulfur hexafluoride and perfluoropropane, there are still limitations in the ready availability of these substances. Therefore, we conducted another survey to determine current patterns of intraocular gas use. The results indicate that more surgeons are using long-acting gases. The data also demonstrate the selective use of pneumatic retinopexy with geographic pockets of increased retinopexy use in California and Florida. Finally, 100% of respondents now indicate that they consider the use of sulfur hexafluoride and perfluoropropane to be a standard of care.

Astemizole reduces blood-retinal barrier leakage in experimental diabetes

We examined the potential of astemizole, a histamine H1-receptor antagonist that does not cross the blood-brain barrier, to reverse blood-retinal barrier leakage to albumin in streptozotocin diabetic rats. Four groups of nondiabetic and four groups of diabetic rats received vehicle or astemizole at dosages of 5, 10, or 20 mg/kg body weight for days 22-28 of a 28-day holding period. There were no significant differences in nondiabetic plasma-vitreous albumin ratios between animals receiving vehicle or any of the three astemizole dosages. Only diabetic rats receiving vehicle showed a significant (p < 0.05) 100% increase in the plasma-vitreous albumin ratio over their nondiabetic counterparts. Diabetic rats receiving either 5, 10, or 20 mg/kg astemizole exhibited total normalization of vitreous albumin accumulation, despite persistence of diabetes. These data indicate that astemizole, an H1-receptor antagonist that does not cross the blood-retinal barrier, is effective in reversing blood-retinal barrier leakage of albumin in experimental diabetes.

A survey of intraocular silicone oil use in the United States

PURPOSE

This survey was conducted to determine the pattern of usage of intravitreal silicone oil in the United States.

METHODS

A questionnaire was sent to 542 members of the Retina and Vitreous Societies in December 1990, and again 6 weeks later in an attempt to improve the response rate.

RESULTS

Two hundred eighty-seven questionnaires (53%) were returned. Ninety-eight percent of the respondents perform vitreous surgery, and 61% of them use silicone oil. This survey determined the degree of participation in Food and Drug Administration (FDA)- and institutional review board-approved protocols and the most common indications for use of silicone oil. Ninety-six percent of the respondents indicated that the use of silicone oil represented an acceptable standard of care.

CONCLUSION

Silicone oil is widely used in the United States despite its lack of FDA approval.

Reduction of severe macular edema in eyes with poor vision after panretinal photocoagulation for proliferative diabetic retinopathy

Currently available data from multicenter randomized trials on laser treatment of diabetic macular edema refer only to eyes with pretreatment visual acuities of 20/160 or better. After observing reduction of more severe macular edema and visual improvement following panretinal photocoagulation (PRP) alone in some patients, we reviewed our experience with this problem. In 18 eyes of 14 patients with proliferative diabetic retinopathy and visual acuity of 20/200 or worse, secondary to severe macular edema were identified. At 6 months after PRP without focal macular laser treatment, macular edema was reduced in 13 eyes, 8 of which improved by greater than or equal to 2 lines of vision. Among the latter 8 eyes, the visual acuity of 4 recovered to 20/80 or better; the remaining 10 eyes, which had chronic retinal pigment epithelial atrophy or extensive macular ischemia, did not improve. Based on these observations, we suggest that peripheral PRP performed in multiple sessions over several months may have a beneficial effect on severe macular edema in some eyes with adequate macular perfusion.

Incorporating safety concerns into design and construction

The nursing facility industry has provided a high level of fire safety according to statistics from the NFPA. To keep and improve this record, fire safety in the design and construction of nursing facilities must be a priority. Since the ground work of fire safety is laid in the design phase and finalized in the construction phase, such a priority will help lower initial and operating costs, improve the function of the facility, and provide a fire safe environment for residents and staff.

Histamine H1 receptors mediate increased blood-retinal barrier permeability in experimental diabetes

To test the hypothesis that histamine receptors mediate increased blood-retinal barrier permeability in experimental diabetes, 51 rats were made diabetic by streptozocin injection (65 mg/kg; jugular vein) and were held for four weeks. The seven animal groups were as follows: untreated controls; untreated diabetic rats; diabetic rats receiving diphenhydramine hydrochloride (Benadryl); diabetic rats receiving cimetidine hydrochloride (Tagamet); diabetic rats receiving diphenhydramine and cimetidine; diabetic rats receiving purified pork insulin (Iletin II); and diabetic rats receiving insulin and diphenhydramine. All treatments were given during the last week. Blood-retinal barrier permeability was assessed through measurement of the vitreous content of fluorescein isothiocyanate conjugated to bovine serum albumin (FITCBSA) after 20 minutes of FITCBSA circulation. Vitreous FITCBSA content of the diabetic group was 64% greater than control content. Diabetic rats treated with either diphenhydramine or diphenhydramine and insulin had respective decreases of 43% and 40% in vitreous FITCBSA content. The vitreous content of the diabetic group receiving insulin was lowered 37% below untreated diabetic values, while the vitreous FITCBSA content of the diabetic group receiving both insulin and diphenhydramine was reduced 63%. These data indicate that retinal histamine H1-receptor activation may be partially responsible for initial blood-retinal barrier leakage of macromolecules into the vitreous and that this abnormal leakage can be prevented both by diphenhydramine and by insulin. Histamine H1 receptors may play an important role in mediating increased blood-retinal barrier permeability in experimental diabetes.

Retinal histamine synthesis is increased in experimental diabetes

We examined retinal de novo histamine synthesis mediated by retinal histidine decarboxylase in normal and streptozotocin-diabetic male, Sprague Dawley rats that were diabetic for 21 days. We also examined effects of insulin and alpha-hydrazinohistidine (alpha HH) treatments on retinal histamine synthesis in this diabetic model. alpha HH is a specific inhibitor of histidine decarboxylase. Results indicate that the retina contains an active histidine decarboxylase enzyme system, and that in streptozotocin diabetes retinal histamine synthesis is increased 197%. Both insulin and alpha HH independently reverse and normalize retinal histamine synthesis. These data thus indicate that the retinal inducible histamine pool is increased in experimental diabetes, and that insulin is an important modulator of retinal histamine metabolism. This newly described retinal metabolic alteration may be one factor responsible for increased retinal vascular permeability in diabetic retinopathy.

Antihistamines reverse blood-ocular barrier breakdown in experimental diabetes

Retinal and other tissue histamine synthesis is increased in experimental diabetes; histamine infusion causes blood-ocular barrier breakdown in nondiabetic rats. We have examined the hypothesis that antihistamines prevent blood-ocular barrier breakdown in streptozotocin diabetes using male Sprague-Dawley rats held 28 days. During the last 7 days they were divided into these treatment groups: control (C), untreated diabetic (D), diabetic rats receiving diphenhydramine-HCl (B), diabetic rats receiving ranitidine (R) and diabetic rats receiving diphenhydramine and ranitidine (BR). Vitreous albumin content was measured 6 hr following fluorescein isothiocyanate bovine serum albumin (FITCBSA) injection. Data show that D had a 98.3% increase in vitreous body FITCBSA over C (p less than 0.05) while B and R showed respective decreases of 34.9% and 51.4% compared to D, R being significantly lower than D (p less than 0.05). BR showed a decrease of 71% (p less than 0.05) compared to D, and R and BR groups were not significantly different from C (p less than 0.05). Leakage into the vitreous was from the retina, not the ciliary body. These data indicate that 1) experimental diabetes results in elevated blood-ocular barrier permeability, which can be reversed by diphenhydramine-HCl and ranitidine; and 2) histamine H1- and H2-receptor activation and interaction by altered endogenous histamine metabolism may mediate blood-ocular barrier breakdown, implicating a pathogenic role of histamine in diabetic retinopathy.

Mucinous adenocarcinoma of the eyelid. A case report

A 52-year-old man had a rapidly growing cystic-appearing lesion on his lower eyelid. Excisional biopsy disclosed a mucinous sweat gland adenocarcinoma and the mucinous material (presumably sialomucin) accounted for the transillumination property of the tumor. These carcinomas should be considered in the differential diagnosis of cystic eyelid lesions.

Congenital optic nerve colobomas: CT demonstration

Patients with ocular coloboma and its variants may exhibit notching of the iris, peripapillary staphylomas, crater-like excavation of the optic disc, funnel-shaped widening of the retrobulbar optic nerve, cup-shaped filling defects in the perioptic subarchnoid space, and concurrent anomalies of the face, skull, and brain. Combined ophthalmological and radiological evaluation identifies these lesions successfully and differentiates them from other ocular pathology.

Congenital pulmonary lymphangiectasis. A case complicated by chylothorax

A case is reported of an infant with features of Noonan Syndrome and congenital pulmonary lymphangiectasis. Soon after birth, persistent respiratory distress developed, and, at 4 months of ge, a chylothorax was noted. Medium chain triglyceride therapy by the enteral route was tried, but parenteral alimentation and chest-tube drainage were required. Diagnosis of pulmonary lymphangiectasis was confirmed by biopsy.

Photic maculopathy secondary to short-circuiting of a high-tension electric current

A 21-year-old man was exposed accidentally to the flash of a high-tension short circuit. He subsequently developed a yellow-gray foveolar lesion with mild central visual loss. Fluorescein angiography demonstrated the area of retinal pigment epithelial disruption and was used to follow its evolution over eight months. The energy level at the retina was estimated at 0.87 Joules/cm2, insufficient to create a thermal burn. Therefore, although the patient suffered thermal facial burns, the foveolar lesion represents a photochemical injury to the retinal pigment epithelium and, hence, is similar to solar retinopathy, eclipse blindness, and arc-welder's retinopathy.