Significant Difference In Intraocular Pressure Research Articles

Intraocular pressure in chronic renal failure patients treated with maintenance hemodialysis.

Ocular complications are frequent in chronic renal failure patients treated with maintenance hemodialysis (HD) and in renal allograft recipients. Headache, nausea and fatigue sometimes develop in combination with a rise in intraocular pressure (IOP). We did not find statistically significant differences in IOP before and after HD. There was no correlation between changes in IOP during HD and the decrease in systolic and diastolic blood pressure or decrease in body weight. No patient had borderline or elevated IOP following HD. Due to improved dialytic techniques a significant rise in IOP during HD rarely occurs anymore.

Effect of local administration of mitomycin C on intraocular pressure

Animal studies suggest that the decrease of intraocular pressure after application of mitomycin C is particularly mediated by toxic effects on the substance of ciliary body. Moreover it has been shown that the concentration of mitomycin C after topical application in the aqueous humour is as high when performing fistulating surgery. In this prospective study we wanted to investigate whether the topical application of mitomycin C would result in a significant decrease of intraocular pressure. Forty-one eyes of 41 patients underwent pterygium surgery using a bare sclera technique. Afterwards phototherapeutic keratectomy with the excimer laser (193 nm) was performed in the area of the excision. In hospital mitomycin C eye drops (0.02%) were given twice daily for four days. The intraocular pressure of treated and untreated eyes was measured with applanation tonometry at least three times per day preoperatively, postoperatively at the fourteenth day and after 6 month. Mean intraocular pressure of the treated eyes was preoperatively 15.73 +/- 2.35 mm Hg, 14 days postoperatively 15.92 +/- 2.79 mm Hg and at the last examination 15.86 +/- 2.39 mm Hg. For untreated eyes the mean intraocular pressure was preoperatively 15.70 +/- 2.04 mm Hg, after 14 days 15.76 +/- 2.96 mm Hg and at the last examination 15.89 +/- 2.67 mm Hg. Consequently there was no statistically significant change of intraocular pressure in the eyes treated with mitomycin C. Furthermore there were no significant differences of intraocular pressure between treated and untreated eyes at any time of postoperative check-up. The short-term local application of mitomycin C did not result in a detectable change of intraocular pressure and is therefore probably an alternative to intraoperative application during filtration surgery.

Eye growth in the aphakic newborn rabbit

Purpose:To examine eye growth in unilaterally lensectomized newborn rabbits.Setting:S:t Erik Eye Hospital, Karolinska Institute, Stockholm, Sweden.Methods:Unilateral lensectomy was performed in 18 randomly selected 23-day-old rabbits. Corneal incision was performed in 2 other rabbits, and the aqueous humor was replaced with balanced salt solution in one eye. Axial length, corneal diameter, corneal thickness, intraocular pressure (IOP), and refraction were measured in all eyes preoperatively and 1, 2, and 3 months postoperatively. The wet mass of the after-cataract was measured 3 months after surgery.Results:The growth of the aphakic eye, as indicated by axial length and corneal diameter, was significantly less than that of the control eye in 14 rabbits. No significant difference in IOP or corneal thickness was found between the lensectomy and control eyes. Four animals had elevated IOP with secondary glaucoma and were excluded from the study. No difference in eye growth was found between the two eyes when no lensectomy was performed. Refraction in the unoperated eye showed a myopic shift. After lensectomy, the operated eye became hyperopic with a myopic shift 3 months after surgery. No correlation was found between eye growth and the wet mass of the after-cataract.Conclusions:Our results suggest that removal of the rabbit crystalline lens at an early age reduces eye growth.

Effects of Simulated High Altitude on Patients Who Have Had Radial Keratotomy

Previous studies documented diurnal myopic shifts in patients who have had radial keratotomy (RK). Recently, hyperopic shifts in these patients exposed to high altitude have been reported. A direct mechanical effect of reduced barometric pressure on surgically altered corneas has been theorized to cause this hyperopic shift. Another hypothesis implicates the effect of hypobaric hypoxia on the RK incisions. The authors examined the effect of a 6-hour exposure to decreased barometric pressure on 14 normal and 18 RK corneas. Cycloplegic refraction, keratometry, corneal pachymetry, and tonometry were performed on seven control subjects and nine patients who have had RK. Measurements were obtained over 8 hours at sea level on day 1 of the study. Measurements were repeated on day 2 which included a 6-hour exposure to 12,000 feet simulated altitude in a hypobaric chamber. Results were compared between subjects and control subjects to determine the effect of a 6-hour exposure to decreased barometric pressure. There was no statistically significant difference in refraction or keratometry readings between control subjects and subjects who have had RK. Central corneal thickness decreased in the afternoon in RK eyes compared with control eyes. There was no clinically significant difference in intraocular pressure between subjects who have had RK and control subjects. A measurable hyperopic shift in RK corneas exposed to high altitude requires more than 6 hours to develop. A direct effect on corneal shape due to barometric pressure alone should produce a sudden change in refractive error. This study supports the hypothesis that a slow metabolic process is responsible for the previously documented hyperopic shifts induced by altitude. However, a barometric pressure effect requiring more than 6 hours to occur cannot be ruled out with the methodology used in this study.

Increase in choroidal blood flow in rabbits with endothelin-1 induced transient complete obstruction of retinal vessels.

In a previous paper, we reported that retinal blood flow (RBF) ceased immediately after injection of 1 nmol endothelin-1 (ET-1) and no recovery of RBF was detected for at least 50 min. In this study, we confirmed the same duration of RBF cessation and measured choroidal blood flow (CBF) for 180 min. We measured CBF in a rabbit model of transient complete obstruction of retinal vessels induced by intravitreal injection of a high dose of ET-1, using the hydrogen clearance method. We also investigated the effects of intravitreal injection of ET-1 on intraocular pressure (IOP), blood pressure, pulse rate and blood gases. CBF was significantly greater in the ET-1-injected eyes than in the control eyes 40-130 min after injection of ET-1 (P < 0.05). The maximal CBF ratio in the ET-1-injected eyes was 128 +/- 7.4% at 40 min. CBF decreased to the pre-injection level at 140 min after the injection of ET-1. There was no significant change in blood pressure, pulse rate and blood gases throughout this experiment, and there was no significant difference in IOP between ET-1-injected eyes and control eyes. It seems likely that the increase in CBF resulted from some local mechanisms of control that compensated for the decrease in RBF induced by intravitreal injection of ET-1. This model may be useful for investigation of the regulatory system of intraocular circulation, including endothelin receptors.

Intraocular pressure after filtering operation or combined filter-cataract operation

The prevalence of glaucoma is 2% and of cataract 25% in patients at the age of 65 to 75 years. To this moment the discussion is open about the optimal therapy when there is simultaneous cataract and glaucoma. We evaluated and compared the intraocular pressure and the visual acuity in patients with filtering-surgery and combined surgery (= filtering surgery plus simultaneous cataract surgery). In a retrospective study 56 eyes of 45 patients operated by filtering surgery and 46 eyes of 40 patients operated by combined surgery were examined. Patients with combined surgery showed significant higher frequency of fibrin in the anterior chamber compared to patients with filtering-surgery. After 12 months there was no significant difference in intraocular pressure between both groups. The IOP of the last examination was 16 +/- 4 mm Hg in eyes with combined surgery and 14 +/- 4 mm Hg in eyes with filtering surgery. Eyes with combined surgery showed an increase of visual acuity from 0.2 +/- 0.2 to 0.4 +/- 0.3, eyes with filtering surgery a decrease of visual acuity from 0.7 +/- 0.3 to 0.6 +/- 0.3. Combined surgery is perioperatively associated with a higher frequency of complications, but showed 12 months postoperatively equal values of regulated intraocular pressure.

Verhalten des intraokularen Druckes unter Anästhesie mit Isofluran im Vergleich zu Propofol/Alfentanil

To investigate the influence of isoflurane anaesthesia versus total intravenous anaesthesia with propofol/alfentanil on intraocular pressure (IOP). 40 patients undergoing ophthalmic surgery were randomly allocated to two study groups. In group 1 (n = 20), anaesthesia was induced with thiopentone 4 mg/kg and alfentanil 15 micrograms/kg. Maintenance of anaesthesia was achieved with isoflurane 0.5-0.8 Vol.% and 70% nitrous oxide in oxygen. Patients in group 2 (n = 20) received propofol 1.5 mg/kg, which was followed by a continuous infusion of 6 mg/kg/h. In addition, alfentanil 15 micrograms/kg was administered, followed by a continuous infusion of 15 micrograms/kg/h. In both groups, endotracheal intubation was facilitated by succinylcholine 1 mg/kg, and further muscle relaxation was achieved with vecuronium 0.07 mg/kg. Measurements of IOP using an applanation tonometer were taken in each patient at 10 different time points. In both groups, there was a significant decrease in IOP after induction of anaesthesia. No significant differences in IOP occurred between groups, with patients in group 2 showing a trend towards lower IOP values. We conclude from our results that both anaesthetic techniques can be administered if increases in IOP have to be avoided.

Prognostic factors and postoperative course following single-plate Molteno implantation.

We evaluated potential preoperative and early postoperative prognostic indicators for chronic intraocular pressure control in 38 consecutive glaucoma patients undergoing single-plate Molteno implantation. Six months following surgery 22 patients had an intraocular pressure < or = 18 mm Hg and were considered successes. Twelve patients had an intraocular pressure > 18 mm Hg and were considered failures. Factors such as age, race, sex, type of glaucoma, phakic status, eye treated, intraocular pressure, bleb elevation, or number of glaucoma medicines were not significantly related to postoperative intraocular pressure control (p > 0.05). Postoperatively a significant difference in intraocular pressure was not observed between success and failure groups until three (13.8 +/- 5.4 versus 20.8 +/- 6.4 mm Hg, p = 0.010) and six (11.2 +/- 3.3 mm Hg versus 21.2 +/- 1.2 mm Hg, p < 0.001) months. Approximately 50% of patients who had an intraocular pressure > 20 mm Hg and 75% of those who measured < 20 mm Hg at any given examination in the early postoperative period were controlled six months postoperatively. Patients controlled at six months maintained control for as long as 43 months postoperatively. This study indicates that in the early postoperative period after a single-plate Molteno implant some patients have an ocular hypertensive phase but may ultimately be controlled, whereas most patients with an intraocular pressure within the normal range maintain control long-term.

Tonometry of normal eyes in raptors

Summary An applanation tonometer was used to estimate intraocular pressure in normal eyes of several species of raptors. No bird had active injury or illness, though some were nonreleasable to the Wild because of previous injury. Mean (± sd) intraocular pressure was 20.6 (± 3.4) mm of Hg in red-tailed hawks (Buteo jamaicensis, n = 10), 20.8 (± 2.3) mm of Hg in Swainson's hawks (Buteo swainsoni, n = 6), 21.5 (± 3.0) mm of Hg in golden eagles (Aquila chrysaetos, n = 7), 20.6 (± 2.0) mm of Hg in bald eagles (Haliaeetus leucocephalus, n = 3), and 10.8 (± 3.6) mm of Hg in great horned owls (Bubo virginianus, n = 6). There was no significant difference in intraocular pressure between hawks and eagles. Mean pressure in great horned owls was significantly (P &lt; 0.01) lower than pressure in hawks or eagles. Reliable intraocular pressure readings could not be obtained in barn owls (Tyto alba).

Late Intraocular Pressure and Complications after Extracapsular Cataract Extraction Using Two Different Viscoelastic Agents: Healon® vs Methylcellulose 2%

OBJECTIVE: Evaluation of late intraocular pressure and late complications after planned extracapsular cataract extraction (ECCE) with posterior chamber lens implantation (PCL) using two different viscoelastic agents. STUDY DESIGN: A prospective open non-randomized study of the intraocular pressure (IOP) and late complications 3, 12 and 36 months after surgery. SETTING: Department of Ophthalmology, Gentofte Hospital, University of Copenhagen, Denmark. PATIENTS: 189 consecutive in-patients (eyes) were operated on using either Healon® or Methylcellulose 2% as viscoelastic agent during surgery. MAIN OUTCOME MEASURES: Late intraocular pressure, late postoperative complications. RESULTS: Compared to the preoperative IOP both the Healon® and the Methylcellulose group showed a significant decrease in IOP after 36 months, P > 0.05. No significant difference in IOP was found between the two groups at corresponding time intervals, P > 0.05. Late complications including persistent iritis, consistently raised IOP, posterior capsular opacity, requirement for Nd:YAG laser capsulotomy, cystoid macular oedema and aphakic retinal detachment were equal in the two groups, P > 0.05. CONCLUSIONS: By extending the observation period up to 36 months, the study provides evidence that eyes operated on with Healon® or Methylcellulose have equal postoperative complication rate. The reduction in IOP seen 12 months postoperatively continues at least up to 36 months. Late complications occurred equally in the two groups.

Ocular Effects of Scopolamine Dermal Patch in Open-Angle Glaucoma

The purpose of this study was to determine the effect of transdermal scopolamine patches on intraocular pressure, pupil size, anterior chamber volume, and accommodation in patients with open-angle glaucoma. Forty patients with chronic open-angle glaucoma participated in a double-masked randomized, placebo-controlled study. Of these 40 glaucoma patients, 20 were on treatment regimens that included pilocarpine (Pilo Group) and 20 were on treatment regimens that excluded pilocarpine or any other cholinergic drug (Non-Pilo Group). For both groups, there was a significant increase in pupil size, anterior chamber volume, and near point on the scopolamine day compared to the placebo day. The pupil size, as measured by pupillography, was increased 17% for the Pilo group and increased 12% for the Non-Pilo group. The volume of the anterior chamber, as measured by photograrmmetry, was increased 8% for the Pilo group and increased 11% for the Non-Pilo group. The near point receded 12% for the Pilo group and receded 19% for the Non-Pilo group. We were unable to detect any statistically significant differences in intraocular pressure for either group. Minimal side effects were reported from both groups. We conclude that it is safe for patients with open-angle glaucoma to use transdermal scopolamine patches.

Simultaneous Bilateral Cataract Extraction: ECCE versus ICCE

OBJECTIVE: To evaluate the differences in visual rehabilitation between intracapsular (ICCE) and extracapsular (ECCE) cataract surgery as well as the significance for visual performance of the position of an intraocular lens in the eye. STUDY DESIGN: Prospective study of simultaneously performed cataract extraction in both eyes, with evaluation at 3 days, 6 weeks, 3 and 6 months after surgery. PATIENTS: Ten adult patients severely visually handicapped from equally advanced cataract in both eyes had simultaneous cataract surgery performed under general anaesthesia with an ECCE with a posterior chamber lens (PCL) in one eye and an ICCE with an anterior chamber lens (ACL) in the other eye. MAIN OUTCOME MEASURES: Refraction and visual acuity (VA) were obtained unbiased by a trained nurse with an autorefractor and with the same instrument a value for contrast (CS) and glare (GS) sensitivity were obtained, expressed as the numerical drop in Snellen lines from the best visual acuity obtained at the same time. RESULTS: After 6 months all patients seemed to have benefited almost equally in both eyes (mean VA/ECCE 0.72 ± 0.15); and mean VA (ICCE 0.80 ± 0.16). No subjective differences in visual performance was noticed between the eyes except in one of the ECCE patients, who experienced the beginnings of opacification in the posterior capsule. There were no significant differences in either CS (ECCE: 2.7 ± 1.8 and ICCE: 3.4 ± 1.3; P = 0.37) or GS (ECCE): 4.4 ± 1.6 and ICCE: 5.2 ± 1.9; P = 0.21) after 6 months. There was no significant difference in intraocular pressure, and no corneal or retinal complication occurred in either group. CONCLUSION: When ICCE and ECCE have been compared, it has always been by retrospective study of different patients operated on by different surgeons, using different microsurgical techniques and with different observation periods. This study is a unique attempt to evaluate the two surgical techniques in a prospective manner. During an observation period of 6 months no differences occurred in visual rehabilitation between ECCE/PCL and ICCE/ACL, when these procedures were performed at the same time in a small number of patients having simultaneous bilateral cataract surgery.

Collagel—a new viscoelastic substance for ophthalmic surgery

A clinical trial comparing the viscoelastic properties of Collagel® (human collagen) and Healon® (sodium hyaluronate) was performed. Collagel was well tolerated and produced no untoward reaction in the eye. Flare cell measurement was performed during the seven day postoperative period. The initial peak and decline of flare and cell determination showed a similar course in groups treated with Collagel or Healon. A transient increase in intraocular pressure was seen. Endothelial cell loss following surgery was similar in the Collage) and Healon groups. There were no significant differences in intraocular pressure, corneal thickness, endothelial cell density, or visual acuity during the postoperative period. These results suggest that this new viscoelastic substance is comparable to Healon in respect to the parameters described.

Postural studies in pulsatile ocular blood flow: II. Chronic open angle glaucoma.

The pulsatile ocular blood flow (POBF) has been recorded in 15 patients with chronic open angle glaucoma. Measurements were performed during regular treatment with timolol 0.25% eyedrops, two weeks after withdrawal of this treatment, and then a further two weeks after its reinstitution. Readings were taken with subjects in both the erect and supine positions by means of a pneumotonometric probe to measure intraocular pressure (IOP), linked to a Langham ocular blood flow system. Assumption of the supine posture was associated with a significant increase in IOP in all phases of the study. Treatment with timolol lowered the mean IOP in comparison with the untreated phase (-4.4 (SEM 0.6) mmHg, p less than 0.001) but had no effect on the postural change. A significant reduction in POBF was recorded on assumption of the supine posture (-66 (SEM 18) microliters/min, p less than 0.001), representing a mean decrement of 19%. However, there were no significant differences in POBF between treated and untreated phases of the study. Comparison of the values obtained in patients with glaucoma (COAG) after withdrawal of treatment with those in subjects with ocular hypertension revealed that there was no significant difference in intraocular pressure between the two groups. However, both POBF (-68 (SEM 29) microliters/min) and the pulse amplitude of the intraocular pressure (ocular pulse: -0.45 (SEM) 0.14 mmHg) were significantly lower in the COAG patients. Pulsatile ocular blood flow is significantly lower in patients with chronic open angle glaucoma. Furthermore, the POBF and the postural response of these patients is not improved by the use of topical timolol therapy.

Caffeine Has No Clinically Significant Effect on Aqueous Humor Flow in the Normal Human Eye

The effect of orally administered caffeine (400 mg) on aqueous humor flow was studied in 20 normal human subjects. The rate of aqueous flow was measured by fluorophotometry. There was no statistically significant difference in aqueous flow measured hourly from 1 to 4 hours after the administration of caffeine. There also was no statistically significant difference in intraocular pressure (IOP) measured 4 hours after caffeine ingestion. The sample size was large enough to have detected a 15% change in flow, had it occurred.

The Effect of Caffeine on Intraocuular Pressure in Glaucoma Patents

The authors investigated the effect of drinking regular coffee on intraocular pressure (IOP) using a single-masked randomized crossover study comparing coffee and herbal tea in 13 glaucoma patients. Intraocular pressure and blood pressure were monitored before ingestion of coffee or tea and at 30, 60, and 90 minutes after ingestion. The mean (± standard error of measurement) change in IOP 30, 60, and 90 minutes after ingestion for the coffee drinkers was 0.96 ± 0.4, 1.38 ± 0.53, and 1.04 ± 0.37 mmHg, respectively. The mean change in IOP for the tea drinkers 30, 60, and 90 minutes after ingestion was 0.85 ± 0.41, 0.23 ± 0.36, and −0.42 ± 0.44 mmHg, respectively. There was a statistically significant difference in the change in IOP at 90 minutes when comparing coffee to tea (P = 0.003) and no significant difference for 30 and 60 minutes. Although there was a statistically significant difference in IOP at 90 minutes between coffee and tea drinkers, the change was not clinically significant.

Increased uveoscleral outflow as a possible mechanism of ocular hypotension caused by prostaglandin F 2α-1-isopropylester in the cynomolgus monkey

The effects of topical application of a single dose of prostaglandin F 2α, administered as the isopropylester, on the intraocular pressure (IOP), aqueous humor flow (AHF), conventional, and uveoscleral outflow were studied in cynomolgus monkeys under pentobarbital anesthesia. 1 μg PGF 2α decreased the IOP by 2·9±0·6 mmHg (3 hr after the application) as compared with the vehicle-treated control eye. The mean AHF during the whole experiment was slightly higher in the experimental than in the control eye, 1·34±0·11 μl min −1 compared with 1·16±0·09 μl min −1. The uveoscleral outflow was significantly increased in the PGF 2α-treated eye, 0·98±0·12 μl min −1 compared with 0·61±0·10 μl min −1 for the control eye. The conventional outflow was lower in the experimental eye throughout the experiment. Topical application of 10 μg pilocarpine at the time when the fall in IOP was expected prevented the drop in the IOP. Simultaneously the increase in the uveoscleral outflow was abolished. After systemic pretreatment with atropine, 1 mg (kg body weight) −1 i.v., there was no significant difference in IOP, AHF, conventional or uveoscleral outflow between the PGF 2α-treated, and the control eye. The results of the present investigation suggest that PGF 2α decreases the intraocular pressure by increasing the uveoscleral outflow. The mechanism behind the increase in the uveoscleral outflow remains to be established. Relaxation of the ciliary muscle as well as enlarged in tramuscular spaces and loss of extracellular material may contribute to the effect.

A DOUBLE‐BLIND STUDY OF THE INFLUENCE OF TRANEXAMIC ACID ON THE CENTRAL CORNEAL THICKNESS AFTER CATARACT EXTRACTION

A double-blind study of the influence of systemic tranexamic acid on the central corneal thickness after cataract extraction was performed in 17 pairs of patients. Apart from the cataract, no were present. A sequential statistics was used to show that the increase in central corneal thickness after operation was significantly less in the tranexamic acid treated group than in the placebo group. There was no significant difference in intraocular pressure between the tranexamic acid and the placebo treated group. The possible influence of tranexamic acid on the thickness controlling mechanism of the cornea is discussed, and studies concerning the fibrinolytic system, the complement system and the aqueous humour amino acid treated patients are mentioned.