Anterior chamber paracentesis and pH values in patients with acute primary angle closure

Background

To assess the efficacy and safety of anterior chamber paracentesis (ACP) and the changes in pH values in eyes with acute primary angle closure (APAC).

Methods

This retrospective case-control study involved 22 patients with APAC who underwent ACP (study group) and 21 patients with APAC who did not undergo ACP (control group). Intraocular pressure (IOP) and visual acuity were measured before treatment and 15 min and 24 h after treatment in both groups. The pH of aqueous humor was measured immediately after ACP in the study group.

Results

A total of 43 eyes in 43 patients were reviewed. The IOP 15 min after ACP (23.3?±?9.6 mmHg) and 24 h after ACP (21.6?±?12.0 mmHg) were significantly lower than that before ACP (58.6?±?12.9 mmHg). The IOP 15 min after ACP was significantly lower than the IOP 15 min after conventional treatment (55.4?±?10.3 mmHg). Visual acuity recovery was achieved earlier after ACP than after conventional treatment. Hyphema after ACP was noted in one eye. The mean pH of the aqueous humor in APAC was 6.99?±?0.35. The pH of the aqueous humor significantly correlated with the duration of acute IOP elevation and the IOP before ACP.

Conclusions

ACP is an effective and safe procedure. The pH of aqueous humor is lower in eyes with APAC of longer duration and in eyes with higher IOP at presentation.     

Entwicklung eines Glaukommikrostents mit Drainage in den suprachoroidalen Raum

Background

The purpose of this study was to develop a microstent with valve function, which normalizes the intraocular pressure (IOP) and drains into the suprachoroidal space. In comparison to the subconjunctival space the suprachoroidal space is attributed with less fibroblast colonization and activity.

Methods

Different glaucoma drainage devices were idealized as tubes and the flow rates were calculated according to Hagen-Poiseuille. The dimensions of the ideal glaucoma implant were modified with respect to an aqueous humor production of 2 µl/min and the different outflow pathways. Specific components of glaucoma drainage devices at the inlet and outlet were not included.

Results

The volume flow calculation of the tested glaucoma implants showed that the dimensions of all lumina were too large to prevent postoperative hypotension. A maximum inner tube diameter of 53 µm was calculated for drainage into the suprachoroidal space based on an intra-ocular pressure (IOP) of 20 mmHg.

Conclusion

The glaucoma microstent has to guarantee an aqueous humor flow for physiological IOP. An increase of IOP has to be regulated to physiological pressure conditions by the microvalve.     

Reconstruction of a nonfunctional trabeculectomy bleb using an amniotic membrane-wrapped silicone sponge to treat refractory glaucoma

Background

This study was conducted to verify the usefulness of nonfunctional trabeculectomy bleb reconstruction using a silicone sponge wrapped with amniotic membrane. Its purpose was to allow aqueous humor to flow from the flap to the posterior orbital space.

Methods

Seven consecutive patients who had undergone two or more surgeries in one eye for refractory glaucoma followed by our operation were included in this study. Conjunctival adhesion to the sclera was detached with a limbus-based conjunctival incision, followed by reopening the former trabeculectomy flap. A 1.5?×?12 mm silicone sponge used for retinal detachment surgery was wrapped three to four times with amniotic membrane, placed longitudinally on the sclera, and fixed with 10–0 nylon sutures. The anterior end of the amniotic membrane was fixed underneath the scleral flap with sutures, and the conjunctival wound was closed. We periodically checked the intraocular pressure (IOP) and for complications. Follow-up periods ranged from 15 to 30 months (average 19.4 months). Surgical success was defined as a final IOP of ≤ 21 mmHg with or without additional treatment. We defined failure as an IOP of > 21 mmHg on the second of two consecutive visits after the first 4 weeks, or the need for additional glaucoma surgery.

Results

Surgery was successful in five of the seven eyes, although bleb needling was performed in two eyes and amniotic membrane patch covering for early aqueous leakage was needed in one eye. In four of the five successful eyes, IOP was well controlled for longer than the period between the previous and present surgeries. One of the unsuccessful eyes, with neovascular glaucoma, had high IOP with hyphema followed by phthisis of the eyeball. The other, with aqueous leakage via the conjunctival wound, required trabeculectomy in a different area. There were no other complications.

Conclusions

Reconstruction of the nonfunctional trabeculectomy bleb using a silicone sponge wrapped with amniotic membrane can be a useful strategy for treating refractory glaucoma.     

Comparison of the ocular characteristics of anterior uveitis caused by herpes simplex virus,varicella-zoster virus,and cytomegalovirus

Purpose

To compare the clinical characteristics of anterior uveitis (AU) caused by herpes simplex virus (HSV), varicella-zoster virus (VZV), or cytomegalovirus (CMV).

Methods

The medical records were reviewed of 46 patients whose diagnoses were based on their clinical characteristics [e.g., unilateral involvement, presence of keratic precipitates (KPs), and elevation of intraocular pressure (IOP)] and on PCR detection of herpes virus DNA in the aqueous humor. The demographics, chief complaints, and clinical characteristics of the three types of herpetic AU were compared.

Results

Of the 46 patients with AU, eight had HSV-AU, 20 had VZV-AU, and 18 had CMV-AU. HSV-AU and VZV-AU shared common features, i.e., a relatively acute disease process and the presence of large KPs. Among the three groups of patients, the characteristic features of those with VZV-AU were severe intraocular inflammation, as shown by severe aqueous flare, highest viral load in the aqueous humor, and presence of segmental iris atrophy. In comparison, patients with CMV-AU had the mildest intraocular inflammation, lowest corneal endothelial cell density, and highest IOP.

Conclusions

Although the AU caused by each of the three types of herpes viruses has a number of common features, each disease also has distinct features that should facilitate an accurate diagnosis.     

Interference of Descemet's Membrane with Aqueous Humor Drainage via an ExPRESS Mini Shunt

Purpose

To describe a case in which Descemet''s membrane interfered with aqueous humor drainage through an ExPRESS mini shunt. This problem was successfully solved by Nd:YAG laser membranotomy.

Case Report

A 70-year-old male, diagnosed with corticosteroid-induced glaucoma in his right eye, presented to our hospital. Topical betamethasone treatment was discontinued, and the patient was treated with intravenous D-mannitol and acetazolamide, followed by oral acetazolamide, oral potassium L-aspartate, topical dorzolamide hydrochloride, topical carteolol hydrochloride, and topical latanoprost. However, his right intraocular pressure (IOP) remained elevated. We performed ExPRESS shunt surgery in the patient''s right eye. His postoperative IOP was initially within the normal range, but it reincreased 1 month after surgery. We found that the Descemet''s membrane was interfering with both the primary (axial) and reserve orifices at the tip of the ExPRESS mini shunt. Nd:YAG laser membranotomy was performed and the patient''s IOP again improved without any other medical treatment.

Conclusion

Descemet''s membrane interfered with aqueous humor drainage via ExPRESS mini shunt, causing an increased IOP, which was resolved by Nd:YAG laser membranotomy.Key words: Corticosteroid-induced glaucoma, Descemet''s membrane, ExPRESS mini shunt     

The effect of previous surgery and topical eye drops for primary open-angle glaucoma on cytokine expression in aqueous humor

Purpose

To evaluate cytokine expression in the aqueous humor of patients with primary open-angle glaucoma (POAG) after previous glaucomatous and/or cataract surgery, and to determine the effect of intraocular pressure (IOP)-lowering eye drops on cytokine expression.

Methods

This prospective consecutive case study included 32 eyes diagnosed with POAG (19 with previous surgery and 13 without previous surgery, treated with topical antiglaucoma medication) and 12 eyes without signs of glaucoma. The Luminex 200 multiplex bead immunoassay was used to measure 27 cytokines in aqueous humor.

Results

Eyes suffering from POAG, with previous surgery, had significantly elevated concentrations of IL-6, IL-8, CCL2, CXCL9, and HGF, and a significantly lower concentration of CCL5, compared to POAG eyes without previous surgery, treated only with topical antiglaucoma medication. When compared with cataract controls, eyes with POAG and previous surgery had significantly elevated levels of G-CSF, IL-8, IL-12, CXCL10, and HGF, and significantly decreased concentrations of IL-17, CCL5, and VEGF in aqueous humor. In a comparison between POAG eyes without previous surgery and cataract controls, the cataract control eyes had significantly higher levels of IL-6 and CCL2, as the only significant difference.

Conclusions

POAG is associated with an aqueous inflammatory response in the aqueous humor, which is significantly elevated in eyes with previous surgery. In contrast, preoperative IOP-lowering eye drops did not significantly alter the anterior chamber milieu. The results of the current study indicate that filtration surgery has a higher success rate in eyes that have not experienced previous surgery.     

One-year results after combined cataract surgery and excimer laser trabeculotomy for elevated intraocular pressure

Background

Glaucoma is one of the most common reasons for blindness. Usually an elevated resistance to aqueous outflow is the reason, while aqueous humor production is still normal. Medical reduction of intraocular pressure (IOP) is the first-line therapy in most cases. The gold standard of surgical treatment is trabeculectomy (TE). But TE has a lot of postoperative complications. Therefore we prefer the combined procedure of cataract extraction plus excimer laser trabeculotomy (phaco-ELT) for a selected group of glaucoma patients. Indications are cataract together with moderately elevated IOP without medical therapy or a moderate cataract together with elevated IOP under medical therapy.

Patients and Methods

During ELT, 10 pores were created over 90° of the anterior chamber angle; 28 eyes of 28 patients (10 men and 18 women) were reexamined 12 months ± 2 weeks after combined phaco-ELT. Four patients were excluded because of IOP-lowering surgery during the follow-up. IOP, best corrected visual acuity, slit lamp biomicroscopy as well as glaucoma medication history (antiglaucoma drugs, AGD) were recorded.

Results

The mean age was 74.33±11.81 years. The diagnosis was primary open-angle glaucoma in 9 eyes, pseudoexfoliative glaucoma in 15 eyes, ocular hypertension in 3 eyes, and 1 post-traumatic secondary glaucoma. On average, phaco-ELT could reduce the IOP by 8.79±5.28 mmHg (?34.70%, p<0.001). AGD could be reduced by 0.79±1.50 (?62.70%, p=0.017) at the same time.

Conclusion

The ELT is easy to perform at the end of cataract surgery. Duration of surgery is only prolonged by 2 to 3 minutes. We found an average IOP reduction of 8.79 mmHg (?34.70%) and an average reduction of 0.79 AGD. It is known that the effect of IOP reduction is constant over time unlike argon or selective laser trabeculoplasty. If needed later on, filtering surgery is not compromised because there is no conjunctival touch during ELT and therefore no scarring of the conjunctiva. For a selected collective of glaucoma patients this procedure could be a good way to avoid trabeculectomy.     

Difference in redox status of serum and aqueous humor in senile cataract patients as monitored via the albumin thiol-redox state

Purpose  

To clarify the redox states of the aqueous humor and serum in senile cataract patients.     

Aqueous Humor Dynamics Associated with the Phorbol Ester-Induced Decrease in Intraocular Pressure in the Rabbit

Purpose To determine the effects of injection of the protein kinase C (PKC) activator phorbol 12-myristate 13-acetate (PMA) into the anterior chamber of the eye on intraocular pressure (IOP) and aqueous humor dynamics. Methods IOP was measured for 24 h after intracameral injection of PMA (3 to 50 pmol) in unanesthetized rabbits. Aqueous humor dynamics (aqueous flow, total outflow facility, and uveoscleral outflow) were determined approximately 6 h after injection of 50 pmol of PMA in animals pretreated with indomethacin. Results Intracameral injection of 50 pmol of PMA induced a biphasic effect on IOP, consisting of a transient increase apparent at 0.5 and 1 h and a sustained decrease apparent after 2 h. This effect of PMA was dose dependent. Whereas pretreatment with indomethacin attenuated the PMA-induced increase in IOP, the sustained decrease in IOP remained apparent in the pretreated rabbits. Intracameral injection of 4α-PMA, an inactive PMA analog, had no effect on IOP. PMA also significantly increased uveoscleral outflow, but it had no effect on aqueous flow or total outflow facility. Conclusion Intracameral injection of PMA reduced IOP in the rabbits by increasing the rate of uveoscleral outflow. This IOP-lowering effect of PMA may be mediated by activation of PKC.     

晚期青光眼的房水动力学变化

目的：观察晚期青光眼高眼压对睫状体功能的损害作用及对角膜透明性的影响。方法：应用扫描荧光光度计及Ｓｃｈｉｏｔｚ电子眼压计分别测定１５只正常眼和１５只晚期原发性青光眼眼压、房水排出率和房水流畅系数,并观察角膜的透明性。结果：晚期青光眼眼房水排出率显著下降,下降程度与眼压水平及病程成正比。房水排出率降低至０．８μｌ／ｍｉｎ。角膜出现水肿混浊,房水排出率下降愈甚,角膜透明性改变愈明显。结论：持续高眼压将     

Concentration of Vascular Endothelial Growth Factor After Intracameral Bevacizumab Injection in Eyes With Neovascular Glaucoma

Purpose

To study the concentration of vascular endothelial growth factor (VEGF) in the aqueous humor before and after intracameral injection of bevacizumab in eyes with neovascular glaucoma, and to detect the duration of an anti-VEGF effect of bevacizumab in the anterior chamber.

Methods

In this prospective interventional case series, 1.25 mg of bevacizumab was injected into the anterior chamber of five eyes in five neovascular glaucoma patients. Aqueous humor samples were obtained just before intracameral injection of bevacizumab and two weeks after injection. The concentrations of VEGF in the aqueous humor were measured using ELISA. To investigate corneal endothelial damage after intrecameral bevacizumab injection, specular microscopy was performed before injection and two weeks after injection. Slit lamp photo and iris fluorescent angiography was performed to determine the regression of iris neovascularization.

Results

After injection, substantial regression of neovascularization or fluorescein leakage was seen in all treated eyes. The VEGF concentrations in the aqueous humor in eyes with NVG were 1181.8±1248.3 pg/mL before intracameral injection of bevacizumab. Two weeks after injection, the VEGF concentrations decreased to 33.2±12.2 pg/mL (p=0.04, Wilcoxon signed rank test). There were no significant changes in IOP or corneal endothelial cells.

Conclusions

Intracameral bevacizumab injection can remarkably reduce iris neovascularization in neovascular glaucoma patients. VEGF levels were significantly decreased two weeks after injection and corneal toxicity was not observed during short term follow-up.     

Fluorophotometry in patients with human immunodeficiency virus with and without cytomegalovirus retinitis

OBJECTIVE: To study the aqueous humor dynamics in subjects with human immunodeficiency virus (HIV) with and without cytomegalovirus (CMV) retinitis. DESIGN: Prospective cross-sectional study. PARTICIPANTS: Fourteen HIV-positive subjects (27 eyes, 19 with CMV retinitis and 8 without CMV retinitis), and a control group of 9 HIV-negative subjects (17 eyes). TESTING: Fluorophotometry. MAIN OUTCOME MEASURES: Aqueous flow rates as measured by fluorophotometry and intraocular pressure (IOP). RESULTS: Analysis of variance of the mean corrected aqueous flow rate revealed that both HIV-positive groups had significantly lower aqueous flow rates than did the control group (P < 0.03). No difference in mean aqueous flow rates was found between the HIV-positive eyes with or without CMV retinitis. Comparison of mean IOP revealed that HIV-positive eyes with CMV retinitis had significantly lower IOP than did the HIV-positive eyes without CMV retinitis (P = 0.03) and HIV-negative subjects (P = 0.002). There was no correlation between aqueous flow rate and IOP in HIV-positive subjects (P > 0.5). CONCLUSION: The lack of correlation between the aqueous flow rate and IOP suggests that there may be some disassociation between these parameters in HIV-positive patients. Further studies are needed to better understand the mechanism of aqueous formation and in the management of disorders affecting IOP in this population.     

Modulation of ocular hydrodynamics and iris function by bremazocine, a kappa opioid receptor agonist

This study was designed to determine the activity of bremazocine (BRE), a relatively selective kappa opioid receptor agonist, on intraocular pressure (IOP), aqueous humor formation and pupil diameter (PD) in conscious, normal, dark-adapted New Zealand white (NZW) rabbits. IOP was measured in normal and unilaterally sympathectomized rabbits using a calibrated pneumatonometer and the aqueous flow rate was determined by the use of a Fluorotron Master. A masked-design study was conducted in which the rabbits' eyes were treated with BRE topically and unilaterally; the fellow eyes received vehicle. IOP and PD measurements were taken at 0.5 hr and 0 time before BRE and 0.5, 1, 2, 3, 4 and 5 hr post-treatment. Fluorophotometry recordings were taken at 1 hr before and 0.5, 1.5, 2.5 and 3.5 hr after topical application of the drug or vehicle. The effect of the relatively selective kappa opioid receptor antagonist, nor-binaltorphimine (nor-BNI), on bremazocine-induced changes in IOP, PD and aqueous flow was also determined. BRE (10 and 100 micrograms 25 microliters-1 vehicle) produced dose-related, bilateral reductions in IOP, PD and aqueous humor flow. A large increase in IOP (14 mmHg) was observed when BRE (100 micrograms) was applied to sympathectomized eyes. This ocular hypertensive effect was antagonized when the sympathectomized eyes were pretreated with naloxone (200 micrograms), a non-selective opioid receptor antagonist. BRE (10 and 100 micrograms) decreased the aqueous humor flow rate bilaterally by approximately 48 and 60%, respectively, at 0.5 hr after administration to the ipsilateral eye. Nor-BNI (100 micrograms) antagonized the effect of BRE (10 micrograms) on IOP and aqueous flow rates more effectively than on PD. These data indicate that bremazocine causes reductions in IOP by suppressing aqueous flow, but the ocular hypotensive effects are dependent on the presence of intact sympathetic nerves. Antagonism of BRE's effects on aqueous humor dynamics by nor-BNI suggests that the mechanism of IOP and aqueous flow reduction may involve, in part, an action on kappa receptors. Further experiments are necessary to fully define the opioid receptor populations in the ciliary body.     

Negative correlation between aqueous vascular endothelial growth factor levels and axial length

Purpose  

The aim of this study was to evaluate the relationship between the concentrations of vascular endothelial growth factor (VEGF) in the aqueous humor and axial length.     

Effects of atrial natriuretic factor (ANF) on intraocular pressure and aqueous humor flow in the cynomolgus monkey.

Atrial natriuretic factor (ANF: human sequence) was examined for its effects on basal and terbutaline-stimulated aqueous humor flow, intraocular pressure (IOP) and uveoscleral outflow in cynomolgus monkeys under pentobarbital anesthesia. A dilution method with radioactively labeled albumin was used for the determination of aqueous humor flow. ANF was given by i.v. infusion or intracamerally. Intracameral administration of terbutaline increased the aqueous humor flow significantly; 1.10 +/- 0.05 microliter min-1 in the control eye and 1.69 +/- 0.06 microliter min-1 in the treated eye. I.v. infusion of ANF, 97 fmol kg-1 min-1, increased the aqueous humor flow by about 44% from basal values in the control eye. There was a small but not statistically significant increase on the terbutaline-treated side. The IOP was not changed by ANF at this dose. An ANF dose of 97 pmol kg-1 min-1 increased the aqueous humor flow by 51% in the control eye and by 19% in the terbutaline-treated eye. A further rise of about 8% in aqueous humor flow was registered on the control side when the infused ANF-dose was doubled. Doubling the dose also resulted in a decrease of the IOP by 1.3 +/- 0.3 mmHg on the control side and 2.2 +/- 0.4 mmHg on the terbutaline-stimulated side. Intracameral administration of ANF (81-162 pmol ml-1 perfusion fluid) increased the aqueous humor flow transiently by approximately 50% with a maximum after about 2 hr. The uveoscleral outflow tended to increase and IOP tended to decrease in the ANF-treated eye compared with the control. However, these effects were not statistically significant. These results suggest that ANF may be involved in the control of aqueous humor formation.     

Effects of systemic desmopressin on aqueous humor dynamics in rabbits

Intravenous desmopressin, a synthetic antidiuretic hormone, resulted in a dose-dependent increase in intraocular pressure (IOP) in rabbits. IOP was increased 3.6 +/- 0.8 mm Hg 6 hr following injection of desmopressin 200 mUnits/kg with the increase lasting over 10 hr. IOP returned to baseline 24 hr after the injection. Systemic blood pressure, plasma osmolarity and arterial blood gases were not altered by desmopressin. The increased IOP was not associated with alterations in measured outflow facility or episcleral venous pressure. Five hours after desmopressin injection, calculated aqueous humor flow was increased approximately 57%. Aqueous humor ascorbate measurements for calculation of flow to diffusion ratios and anterior chamber fluorophotometry also were consistent with an increased rate of aqueous humor formation as the mechanism for the IOP elevation. Desmopressin administration did not increase aqueous humor protein or aqueous humor cyclic AMP concentration. Systemic pretreatment with indomethacin only partially blocked the IOP increase. Systemic pretreatment with demeclocycline completely blocked the desmopressin-induced increase in IOP.     

Coincidence of Varicella-Zoster Virus Anterior Uveitis in a Patient with Chandler's Syndrome

Purpose

We report a patient who, based on the clinical manifestations, was originally diagnosed as having Chandler''s syndrome and later developed varicella-zoster virus (VZV) DNA-positive anterior uveitis.

Methods

The patient with Chandler''s syndrome who manifested anterior uveitis underwent a complete ophthalmologic examination. Polymerase chain reaction (PCR) was used to amplify the viral DNA in the aqueous humor to determine the cause of the intraocular inflammation.

Results

Slit-lamp biomicroscopy showed focal iris atrophy and peripheral anterior synechiae (PAS); specular microscopy of the corneal endothelium disclosed the hammered-silver appearance. Based on these clinical findings, we diagnosed this patient as having Chandler''s syndrome. During the follow-up period, however, the inflammatory cells suddenly appeared in the anterior chamber with formation of keratic precipitates and an increased intraocular pressure (IOP). VZV DNA was displayed in the aqueous humor by PCR. Based upon the diagnosis of VZV anterior uveitis, corticosteroids and acyclovir were given topically and systemically. The inflammation subsided with these medications; however, trabeculectomy was finally needed to control the IOP due to PAS progression.

Conclusion

The coincidence of VZV anterior uveitis with Chandler''s syndrome may constitute an implication for the possible viral etiology of iridocorneal endothelial syndrome.Key words: Chandler''s syndrome, Iridocorneal endothelial syndrome, Varicella-zoster virus, Anterior uveitis     

Effects of vasoactive intestinal polypeptide (VIP) on intraocular pressure, facility of outflow and formation of aqueous humor in the monkey

Stimulation of the facial nerve causes a non-cholinergic vasodilation in the uvea and a rise in the intraocular pressure in rabbits, cats and monkeys. Vasoactive intestinal polypeptide (VIP) has been suggested as the neurotransmitter mediating these effects. In the present investigation, the effects of VIP on aqueous humor dynamics were studied in cynomolgus monkeys. After intracameral injection of 1 microgram VIP, the outflow facility was higher in the experimental eye than in the control; 0.42 +/- 0.46 compared with 0.33 +/- 0.03 microliter cm H20-1 min-1, difference 0.09 +/- 0.04 microliter cm H2O-1 min-1. Intravenous infusion of VIP, 160 ng min-1, increased aqueous humor flow from 1.12 +/- 0.07 to 1.65 +/- 0.09 microliter min-1. Almost the same effect, a 50% increase in aqueous humor flow, was found after intracameral administration of 90 micrograms VIP. This dose of VIP caused a significant increase in intraocular pressure (IOP) in the experimental eye. The maximal difference in IOP between the experimental eye and the control eye was 7.5 +/- 0.4 cm H2O. A lower dose of VIP, 30 micrograms intracamerally, increased aqueous humor flow by about 20%, but had no consistent effect on IOP. The effect of VIP on aqueous humor flow was not affected by pretreatment with indomethacin. The results suggest that most of the rise in IOP caused by intracameral VIP administration is due to a rise in the pressure in the veins into which the aqueous humor is drained. Enhanced formation of aqueous humor plays a smaller role. The effects of VIP on aqueous humor formation and outflow facility suggest that the facial nerve may be involved in nervous control of aqueous humor dynamics, as VIP is most probably released in the eye by stimulation of the facial nerve.     

The aqueous humor dynamics and the biphasic response in intraocular pressure induced by guanethidine and adrenaline in the glaucomatous eye

Continuous administration of guanethidine (3%) and adrenaline (0.5%) in one eyedrop (GA) induced a biphasic response of intraocular pressure (IOP). In ten patients with primary open angle and seven glaucoma suspects treated with (GA) twice daily during a 7 month period, tonography, and tonometry were performed and the pupil diameter measured 3 and 8 h post-GA. The combined data of both groups in the hypertensive phase, showed an IOP increase of 2.8 mm Hg (P<0.05), an unchanged coefficient of the outflow, dilated pupil (1.73 mm) (P<0.005) and a 36% increase of aqueous humor production (P<0.02). The specific biphasic course of IOP during treatment with GA seems to be caused by fluctuations in aqueous humor production. The increase in aqueous rate during the hypertensive phase could be related to secondary (rebound) vasodilation in the ciliary body and/or to a transient disruption of the blood-aqueous barrier induced by release of prostaglandins.     

A study of the relation between intraocular pressure and aqueous humor flow in the pigment dispersion syndrome

Forty subjects with pigment dispersion syndrome with and without intraocular pressure (IOP) elevation were compared with 40 age-matched controls. Intraocular pressure, resistance to outflow, and the rate of flow of aqueous humor were compared. Eyes with higher IOP and higher resistance to outflow were found to have a normal rate of aqueous flow. The results are interpreted as demonstrating that moderate and chronic elevation of IOP in the adult human eye does not induce a chronic compensatory reduction of aqueous humor flow.