Dysbarism: osmosis caused by dissolved gas?

The pressure in an osmometer, filled with nitrous oxide-saturated water separated from water by a polyurethane polyether membrane 2.5 microns in thickness, rose slowly by 8 to 20 millimeters (of water) in 10 minutes before gradually returning to close to zero within 2 hours. The permeation coefficient of the membrane was approximately 1000 times greater for water than for gases. The osmotic pressure of water saturated with nitrous oxide at 1 atmosphere, derived from the freezing point of the gas solution, was 1.5 atmospheres. It is concluded that dissolved gases exert osmotic pressure. Partial-pressure gradients of dissolved gases in the tissues of animals and man should cause flows of water along osmotic gradients, which may partially account for some of the symptoms and signs of dysbarism.

Hydraulic compression of mice to 166 atmospheres.

Hydraulic uniform compression elicited tremors, uncoordinated limb movements, and tonic convulsions in liquid-breathing mice at pressures ranging from 50 to 100 atmospheres. Such abnormal muscular activity was observed neither in control animals nor in mice caudally to a spinal transection. Uniform compression of isolated preparations of mouse muscle in saline failed to contract at pressures up to 200 atmospheres.

Volume-controlled lung lavage in a woman with cystic fibrosis.

A 22-year-old woman with cystic fibrosis was treated by volume-controlled lavage of each of her lungs on two occasions. Following the first lavages, the patient's vital capacity increased by 1.03 liters and her 1-sec forced expiratory volume increased by 0.70 liters/second. Similar improvements, although less pronounced, were noted after both lungs has been lavaged a second time. It is concluded that volume-controlled lung lavage can be of benefit as an adjunct in the treatment of patients with cystic fibrosis.

Investigations of black bronchoalveolar human lavage fluid.

The removal by bronchoalveolar lavage (two occasions) of 10(11) black macrophages containing crystals of aluminum silicate, large amounts of amorphous carbon, and oxidized lipids was followed by considerable improvement in gas exchange in a patient. Sixty-eight percent of these pulmonary macrophages were viable and normal, as judged by chemotatctic and phagocytic activity. Except for cigarettes, no source for the previously mentioned ingested foreign substances was found. These observations suggest that removal by lavage of nonviable macrophages laden with foreign bodies from distal portions of the lungs of pulmonary patients may be therapeutically useful.

Delayed vitreous hemorrhage after placement of a ganciclovir implant for cytomegalovirus retinitis.

PURPOSE: To report a massive vitreous hemorrhage in a 26-year-old woman that occurred approximately 6 weeks after she received a ganciclovir implant. METHOD: Case report. RESULTS: The cytomegalovirus retinitis was inactivated after uncomplicated insertion of a ganciclovir implant. Approximately 6 weeks later, the patient was examined for sudden painless visual loss caused by a dense vitreous hemorrhage. CONCLUSION: Sustained-release ganciclovir implants may be associated with delayed vitreous hemorrhage.

Indirect ophthalmoscope perimetry in patients with retinal detachment or retinoschisis.

PURPOSE/METHODS: We evaluated visual field testing, using indirect ophthalmoscopy, in patients with retinal detachment or retinoschisis. While performing ophthalmoscopy, we projected a shadow onto the schisis or detachment by holding a scleral depressor on the observer's side of the condensing lens. A response was recorded as positive if the patient saw the shadow. RESULTS/CONCLUSION: In all 20 detachment eyes, compared to zero of 12 schisis eyes, the response was positive. Indirect ophthalmoscope perimetry can help distinguish retinoschisis from retinal detachment.

Clinical predictors of scleral rupture after blunt ocular trauma.

We conducted a two-part study to define better the clinical predictors of scleral rupture after blunt trauma. In part 1 we ascertained the prevalence of scleral rupture among a population of patients examined in an ophthalmic emergency room with severe blunt ocular trauma over a six-month period. Scleral rupture was diagnosed in ten of 283 patients (3.5%). In part 2 we compared the clinical findings in 29 patients with scleral rupture to those of 273 patients with no scleral rupture after blunt trauma. We noted that eyes with visual acuity of light perception or less, an intraocular pressure of 5 mm Hg or less, an abnormally deep or shallow anterior chamber, or a media opacity preventing a view of fundus details by indirect ophthalmoscopy, should be considered ruptured when severe intra- or periocular hemorrhage is present. This diagnostic algorithm had a sensitivity of 100.0% (98.7% to 100.0%), specificity of 98.5% (97.1% to 99.9%), and a positive predictive value of 71.4% (66.3% to 76.5%).

Clinical course and systemic correlates of retinopathy of prematurity in quintuplets.

PURPOSE/METHODS: We studied clinical correlates of retinopathy of prematurity in four surviving quintuplets with similar low birth weights and gestational age of 27 weeks. Prospective serial ophthalmoscopic examinations and retrospective chart analysis were used. RESULTS/CONCLUSIONS: Retinopathy of prematurity varied among the neonates from stage 2 with total regression to threshold progressing to retinal detachment. Severity of eye disease correlated with duration of mechanical ventilation and of parenteral nutrition, as well as frequency of hypoglycemia and of hypercapnia. Poor outcome correlated inversely with weight gain.

Oxacillin-resistant Staphylococcus aureus endophthalmitis after ganciclovir intraocular implant.

PURPOSE: To describe a patient who developed oxacillin-resistant Staphylococcus aureus endophthalmitis after insertion of a ganciclovir intraocular implant. METHOD: Case report. RESULTS: A 42-year-old man with acquired immunodeficiency syndrome (AIDS) and a history of cytomegalovirus retinitis was admitted with right-sided eye pain and decreased visual acuity 10 days after receiving a second ganciclovir intraocular implant in the right eye. A therapeutic vitrectomy, right eye, was performed on the day of admission. A vitreal tap produced frank pus and white, fluffy debris. Cultures of the vitreal fluid grew oxacillin-resistant S aureus, sensitive only to vancomycin, rifampin, and trimethoprim/sulfamethoxazole. The patient was successfully treated with removal of both ganciclovir implants in the right eye and a 4-week course of vancomycin and rifampin. However, the infection left the patient blind in the infected eye. CONCLUSION: Bacterial endophthalmitis is an infrequent but serious complication of the ganciclovir intraocular implant.

Intraocular pressure increase associated with epsilon-aminocaproic acid therapy for traumatic hyphema.

We treated five patients receiving epsilon-aminocaproic acid who demonstrated sudden and accelerated clot dissolution with accompanying increases in intraocular pressure 24 to 96 hours after discontinuing treatment. All of these patients required additional ocular hypotensive medications and one patient required anterior chamber washout for persistently increased intraocular pressure. These findings suggest that certain patients with hyphema may be at risk for significant intraocular pressure increases following cessation of epsilon-aminocaproic acid therapy.

Prognostic significance of vascular dilation and tortuosity insufficient for plus disease in retinopathy of prematurity.

BACKGROUND: Plus disease, one of the most important prognostic indicators in retinopathy of prematurity (ROP), is designated as present or absent. A grading system based on comparison with standard, high-quality color photographs may be useful to more accurately describe the spectrum of vascular dilation and tortuosity preceding plus disease, but it is of practical value only if it has prognostic significance. We hypothesized that grading of "pre-plus" vascular changes can identify eyes at risk for progression to vision-threatening ROP. METHODS: Video clips of posterior pole images captured at the examination closest to 33 weeks' postconceptional age of 32 infants screened during an 18-month period were randomized. Two masked examiners viewed and graded the images in comparison with standard photographs representative of 5 distinct grades of retinal vascular dilation and tortuosity. A case-control design was used to compare the incidence of progression to stage 3 ROP, development of plus disease, and requirement of laser treatment between infants with normal posterior poles and those judged to have early dilation and tortuosity insufficient for plus disease. RESULTS: Of the 8 patients with mild vascular dilation and tortuosity insufficient for plus disease, 5 (63%) eventually required laser treatment, 4 (50%) later developed stage 3 ROP, and 5 (63%) progressed to plus disease. Of the 24 patients with normal posterior poles, none required laser treatment, 2 (8%) developed stage 3 ROP, and none progressed to plus disease. The group with mild vascular dilation and tortuosity had a significantly higher incidence of progression to laser treatment (P =.0003), stage 3 ROP (P =.027), and plus disease (P =.0003). CONCLUSIONS: Early vascular dilation and tortuosity judged insufficient for plus disease have prognostic significance in the early course of ROP. A grading system that uses standard, high-quality color photographs representing the spectrum of "pre-plus" vascular changes has potential utility in both the clinical and research settings.

Poor postnatal weight gain: a risk factor for severe retinopathy of prematurity.

PURPOSE: This study aimed to investigate the relationship between rate of postnatal weight gain and severity of retinopathy of prematurity (ROP). METHODS: All infants (n = 111) screened for ROP at a single tertiary intensive care nursery over a 2-year period with an estimated gestational age of 30 weeks or less and follow-up to at least 42 weeks' postconception were included. The authors performed a retrospective review of records and statistical analysis of risk factors for ROP using multivariate analysis. RESULTS: Infants with severe (stage 3 or greater) ROP gained an average 10.9 g/kg per day in the first 6 weeks of life, compared to a mean of 9.6 g/kg per day for those with mild or no ROP (P =.04). By multiple regression, which included birth weight, gestational age, and 9 other reported risk factors, there was an association between rate of postnatal weight gain and severity of ROP (P =.02). By stepwise regression, 4 variables were associated with ROP severity: estimated gestational age at birth (P =.002), rate of postnatal weight gain (P = .0002), volume of transfused erythrocytes (P =.0001), and culture-proven sepsis (P = .02). CONCLUSION: Poor postnatal weight gain is a risk factor for the development of severe (stage 3 or greater) ROP. Ophthalmologists should take note of those infants who gain less than 50% of their birth weight in the first 6 weeks of life.

Significance of isolated neovascular tufts ("popcorn") in retinopathy of prematurity.

BACKGROUND: The significance of isolated neovascular tufts ("popcorn") occurring in association with stage 2 retinopathy of prematurity (ROP) has not been studied. METHODS: We retrospectively reviewed the clinical courses and outcomes of all patients with zone II, stage 2 ROP with popcorn examined over the past 3 years at one institution. Eyes with zone I disease, plus disease, or stage 3 at the initial appearance of popcorn were excluded. The study group was compared with a control group of patients of similar birth weight and gestational age with zone II, stage 2 ROP without popcorn. RESULTS: Popcorn first appeared at a mean age of 36.4 (+/- 2.2) weeks after conception in 26 patients. Of these, 17 patients (65%) progressed to stage 3, 10 (38%) had plus disease, 6 (23%) reached threshold, and 9 (35%) required laser treatment. Of 19 control patients, 4 (21%) progressed to stage 3, 1 (5%) had plus disease, 1 (5%) reached threshold, and 1 (5%) required laser treatment. The popcorn group had a significantly higher incidence of progression to stage 3 (p < 0.005), plus disease (p < 0.025), and laser treatment (p < 0.025). All eyes of both groups had complete regression of disease. CONCLUSIONS: The presence of popcorn significantly increases the risk that an eye with zone II, stage 2 ROP will progress to stage 3, develop plus disease, and require laser treatment. Patients with popcorn and coexistent mild vascular dilation or tortuosity insufficient for plus disease are at particularly high risk for disease progression.

Management of suspected ocular laceration or rupture.

The records of 95 consecutive patients with suspected ocular laceration or rupture managed by a single surgeon were reviewed. A total of 86 patients were found to have a laceration or rupture, of whom 79 were followed up, for an average of 6.4 months. In 32 eyes (40%) the final visual acuity was 20/40 or better, and in another 32 the final acuity was less than 5/200. Eyes with lacerations had a better visual outcome than those with rupture due to blunt trauma. Of the 26 eyes operated on for suspected blunt rupture 6 (23%) were found not to have a rupture. Ruptured eyes were more likely than nonruptured eyes to have abnormal anterior chamber depth, vision less than hand motion and hyphema.

Observer sensitivity to retinal vessel diameter and tortuosity in retinopathy of prematurity: a model system.

BACKGROUND: Abnormally increased diameter and tortuosity of retinal blood vessels in the posterior pole, or "plus disease," is recognized as a powerful predictor of poor outcome in eyes with retinopathy of prematurity (ROP). Although the diagnosis of plus disease depends upon the examiner's ability to examine retinal blood vessels, the ability of the human observer to identify changes in retinal blood vessel diameter and tortuosity accurately has not been studied. METHODS: Using computer-aided analysis of fundus photographs from eyes with a wide range of ROP severity, we generated tracings of posterior pole blood vessels which varied by quintiles of mean vessel diameter and tortuosity. Subjects (23 naive and 12 expert observers) ranked groups of tracings in order of increasing mean vessel diameter and tortuosity. These ranking tests were performed on tracings derived from the same fundus and tracings derived from distinct fundi. In a similar fashion, subjects also compared one designated standard fundus tracing with 25 distinct fundus tracings. RESULTS: Vessel diameter was assessed correctly more often than vessel tortuosity, both among similar (> 99% vs 92% of the time, respectively, P < 0.001), or among distinct (88% vs 78% of the time, respectively, P < 0.001) fundus images. The mean vessel diameter and tortuosity of 25 distinct fundus images were correctly ranked versus a standard image in 89% of attempts. Assessments of increments in vessel diameter and tortuosity were independent. Naive and expert subjects performed indistinguishably on all tests. CONCLUSIONS: Intelligent human observers have considerable ability to discern clinically relevant increments in blood vessel diameter and tortuosity. This ability may facilitate standardization in the diagnosis of plus disease in ROP.

Postoperative complications following vitrectomy for proliferative diabetic retinopathy with sew-on and noncontact wide-angle viewing lenses.

BACKGROUND AND OBJECTIVE: To compare the occurrence of vitreous hemorrhages and retinal detachments following vitrectomy surgery with sew-on lenses to a noncontact wide-angle lens system. PATIENTS AND METHODS: Retrospective review of 180 patients who underwent primary vitrectomy for proliferative diabetic retinopathy. The occurrence of persistent and recurrent vitreous hemorrhages as well as postoperative retinal detachments in the two groups was determined. RESULTS: There was no statistically significant difference in the occurrence of persistent vitreous hemorrhages between the sew-on (55%) and the wide-angle (42%) lens systems (P = 0.099). Likewise, recurrent vitreous hemorrhages were similar in both the sew-on (15%) and the wide-angle (17%) lens systems (P = 0.838). However, postoperative detachments were more frequent in the sew-on group (9%) than in the wide-angle (1%) group (P = 0.046). CONCLUSION: In patients with proliferative diabetic retinopathy, using a wide-angle noncontact lens system significantly reduced the incidence of postoperative retinal detachments, but not persistent or recurrent vitreous hemorrhages.