Is Chronic Kidney Disease Affecting the Postoperative Complications of Vitrectomy for Proliferative Diabetic Retinopathy?

Chronic kidney disease (CKD) is a well-known risk factor for postoperative complications in several surgical fields. However, although prevalent among diabetic candidates for vitrectomy, the effect of CKD on vitrectomy outcomes remains unclear. This study aimed at clarifying the relationship between CKD and the occurrence of vitrectomy-related complications in patients with proliferative diabetic retinopathy (PDR). The 6-month incidences of vitreous hemorrhage (VH) and neovascular glaucoma (NVG) following vitrectomy for PDR were compared among the following groups: stages 1-2 CKD (60 patients), stages 3-5 CKD (70 patients not on hemodialysis), and hemodialysis (HD; 30 patients). We also determined whether the deterioration of the estimated glomerular filtration rate (eGFR) was associated with post-vitrectomy events. The incidence of VH was significantly higher in the stages 3-5 CKD group (43%) than in the stages 1-2 CKD (10%) and HD (10%) groups. NVG was more common in the stages 3-5 CKD group (17%) than in the stages 1-2 CKD (2%) and HD (0%) groups. The reduced estimated glomerular filtration rate (eGFR) was the only significant variable associated with post-vitrectomy VH and NVG. Patients with PDR and CKD, particularly those with lower eGFR, might be at risk for post-vitrectomy VH and NVG.

The potential role of glutamate transporters in the pathogenesis of normal tension glaucoma.

Glaucoma, a progressive optic neuropathy due to retinal ganglion cell (RGC) degeneration, is one of the leading causes of irreversible blindness. Although glaucoma is often associated with elevated intraocular pressure (IOP), IOP elevation is not detected in a significant subset of glaucomas, such as normal tension glaucoma (NTG). Moreover, in some glaucoma patients, significant IOP reduction does not prevent progression of the disease. Thus, understanding IOP-independent mechanisms of RGC loss is important. Here, we show that mice deficient in the glutamate transporters GLAST or EAAC1 demonstrate spontaneous RGC and optic nerve degeneration without elevated IOP. In GLAST-deficient mice, the glutathione level in Müller glia was decreased; administration of glutamate receptor blocker prevented RGC loss. In EAAC1-deficient mice, RGCs were more vulnerable to oxidative stress. These findings suggest that glutamate transporters are necessary both to prevent excitotoxic retinal damage and to synthesize glutathione, a major cellular antioxidant and tripeptide of glutamate, cysteine, and glycine. We believe these mice are the first animal models of NTG that offer a powerful system for investigating mechanisms of neurodegeneration in NTG and developing therapies directed at IOP-independent mechanisms of RGC loss.

The efficacy of TonoLab in detecting physiological and pharmacological changes of mouse intraocular pressure--comparison with TonoPen and microneedle manometery.

PURPOSE: The efficacy of two non-invasive tonometers, TonoLab and TonoPen XL, in detecting physiological or pharmacological changes of intraocular pressure (IOP) in mouse eyes, was assessed by comparison with a microneedle method. MATERIAL AND METHODS: C57BL6 mice, bred under the 12-hr light and dark cycle over 2 weeks, were used. Under systemic anesthesia, mouse eyes were cannulated by a microneedle connected to a transducer and a water reservoir. We manipulated the intracameral pressure by changing the reservoir height, and obtained tonometer readings at each pressure (n=39) with TonoLab and TonoPen XL. The correlation between each tonometer and the manometer was analyzed. Then the diurnal variation of IOP in the light and dark phases, and the IOP-lowering effect at 2 hr after latanoprost instillation, were measured with TonoLab, TonoPen XL, and a microneedle tonometer (n=8). RESULTS: In mouse eyes, TonoPen XL could not show reliable scores, but TonoLab readings showed a strong correlation with manometer readings (y=0.87x-0.27, r2=0.917). Nocturnal elevation of IOP in mouse eyes was significantly indicated with TonoLab and a microneedle tonometer (p<0.001), but not with TonoPen XL. Latanoprost significantly reduced IOP by 2.1+/-2.8 and 2.0+/-1.0 mmHg with TonoLab and a microneedle tonometer, but not with TonoPen XL. CONCLUSION: TonoLab provides similar readings to a microneedle tonometer, and diurnal variation and drug effect were detectable in mouse eyes. TonoLab promises to be a non-invasive and useful method to evaluate physiological and pharmacological studies in mouse eyes.

Efficacy of TonoLab in detecting physiological and pharmacological changes in rat intraocular pressure: comparison of TonoPen and microneedle manometry.

PURPOSE: To assess the efficacy of two noninvasive tonometers, TonoLab and TonoPen-XL, in detecting physiological or pharmacological changes of intraocular pressure (IOP) in rat eyes, by comparing them with the microneedle method. METHODS: Sprague Dawley rats, bred under a 12-h light-and-dark cycle, were used. Under systemic anesthesia, eyes were cannulated by a microneedle connected to a transducer and a water reservoir. Variable intracameral pressure was attained by changing the reservoir height, and the resulting tonometer readings were compared. Then, the daytime and nighttime IOP, and the effect at 2 h after latanoprost instillation, were measured with the three devices. RESULTS: TonoLab and TonoPen-XL readings (y) were strongly correlated with microneedle tonometer readings (x) (y=0.96x-4.3, r2=0.985, and y=0.48x+3.9, r2=0.985, respectively), but TonoPen-XL readings were only half those of the microneedle tonometer. Nocturnal elevation of IOP was significant both with TonoLab and with the microneedle tonometer (P<0.001), but not with TonoPen-XL. Latanoprost significantly elevated IOP by 3.0+/-2.1 with TonoLab and by 1.1+/-1.1 mmHg with the microneedle tonometer (P<0.05), but not with TonoPen-XL. CONCLUSION: TonoLab provides readings similar to those of a microneedle tonometer, and diurnal variations and drug effects were detectable. TonoLab promises to be a noninvasive and useful method for physiological and pharmacological studies in rat eyes.

The IOP-lowering effects and mechanism of action of tafluprost in prostanoid receptor-deficient mice.

AIM: To clarify the intraocular pressure (IOP)-lowering profile of tafluprost, a newly synthesised prostaglandin F(2alpha) analogue, in mice. METHODS: C57BL/6J, and EP1, EP2, EP3 and postaglandin F (FP) receptor-deficient wild-type (WT), EP1KO, EP2KO, EP3KO and FPKO, respectively mice were bred and acclimatised under a 12-h (6:00-18:00) light-dark cycle. To evaluate effects of tafluprost (0.002%) on IOP at night, a single 3 microl drop of tafluprost solution was applied topically at 18:00 once into one eye in each mouse. IOP was measured 3 h after the application with a microneedle method. To clarify whether endogenous prostaglandin is concerned with the tafluprost-induced IOP reduction, we applied 0.1% diclofenac Na, a cyclo-oxygenase inhibitor or PBS 30 min before the application of tafluprost in WT and EP3KO mice and measured IOP 3 h after the tafluprost application. We also determined whether animals responded predictably to 0.1% bunazosin HCl, a drug known to increase uveoscleral outflow. RESULTS: 3 h after the application of 0.0015% tafluprost, mean (SEM) IOP reductions were 25.8 (2.1)% 26.3 (0.8)% 24.2 (1.4)% 16.5 (1.7)% and -0.9 (1.5)% in WT, EP1KO, EP2KO, EP3KO and FPKO mice, respectively. IOP reductions in EP3KO and FPKO mice were significantly smaller than in WT mice. Pretreatment with diclofenac Na significantly attenuated the IOP lowering effect of tafluprost in WT mice but not in EP3KO mice. Bunazosin HCl lowered IOP significantly in all genotypes by the same amount. CONCLUSION: We conclude that tafluprost lowers IOP through the prostanoid FP receptor. A part of ocular hypotensive effect of tafluprost is attributed to FP receptor-mediated prostaglandin production acting through the prostanoid EP3 receptor.

The effects of prostaglandin analogues on prostanoid EP1, EP2, and EP3 receptor-deficient mice.

PURPOSE: To determine the role of prostanoid EP receptors in the intraocular pressure (IOP)-lowering effect of prostaglandin analogues in EP receptor-deficient mice. METHODS: Animals were bred and acclimatized in a 12-hour light-dark cycle. The diurnal IOP variation was measured by a microneedle method in EP1, EP2, and EP3 receptor-deficient mice (EP1KO, EP2KO and EP3KO) and in their wild-type (WT) background strain. IOP was measured in each mouse at night 3 hours after application of latanoprost, travoprost (0.004%), bimatoprost (0.03%), or unoprostone (0.12%). In WT and EP3KO mice, the effects of preapplication of diclofenac Na on drug-induced IOP reduction were examined. RESULTS: Baseline IOPs were the same for all strains. Higher baseline IOPs were observed at night. Maximum IOP reduction occurred in WT mice 3 hours after latanoprost application during the day and night. Three hours after instillation at night, each of the four drugs lowered IOP significantly in WT, EP1KO, and EP2KO mice, whereas EP3KO a significantly lesser effect was induced by latanoprost, travoprost, and bimatoprost. Preapplication of diclofenac Na significantly attenuated drug-induced IOP reduction in WT but not in EP3KO mice. CONCLUSIONS: Deficiency of EP receptors had no effect on physiological IOP. EP1 and EP2 receptors are not involved in prostaglandin analogue-induced IOP reduction, whereas EP3 receptors may play a role.

Establishment of an experimental ferret ocular hypertension model for the analysis of central visual pathway damage.

Glaucoma optic neuropathy (GON) is a condition where pathogenic intraocular pressure (IOP) results in axonal damage following retinal ganglion cell (RGC) death, and further results in secondary damage of the lateral geniculate nucleus (LGN). Therapeutic targets for glaucoma thus focus on both the LGN and RGC. However, the temporal and spatial patterns of degeneration and the mechanism of LGN damage have not been fully elucidated. Suitable and convenient ocular hypertension (OH) animal models with binocular vision comparable to that of monkeys are strongly needed. The ferret is relatively small mammal with binocular vision like humans - here we report on its suitability for investigating LGN. We developed a new method to elevate IOP by injection of cultured conjunctival cells into the anterior chamber to obstruct aqueous outflow. Histologically, cultured conjunctival cells successfully proliferated to occlude the angle, and IOP was elevated for 13 weeks after injection. Macroscopically, the size of the eye gradually expanded. Subsequent enlargement of optic nerve head cupping and atrophic damage of LGN projected from the OH eye were clearly observed by anterograde staining with cholera toxin B. We believe the ferret may be a promising OH model to investigate secondary degeneration of central nervous system including LGN.

Effects of topical phenylephrine and tafluprost on optic nerve head circulation in monkeys with unilateral experimental glaucoma.

PURPOSE: To compare the effects of a topical alpha agonist (vasoconstrictor) and a prostaglandin receptor (FP) agonist (vasodilator) on circulation in the optic nerve head (ONH) in experimental glaucomatous and normal eyes of monkeys. METHODS: Tissue blood velocity in the ONH (NB(ONH)) was determined using the laser speckle method in both eyes of eight normal cynomolgus monkeys under systemic anesthesia for 180 minutes after bilateral instillation of 5% phenylephrine. The effect of 0.0015% tafluprost, a potent FP agonist, was also studied after single and once-daily 7-day instillations. Measurements were repeated in both eyes of the eight monkeys after establishment of unilateral laser-induced glaucoma. RESULTS: NB(ONH) decreased significantly in both eyes of normal monkeys 30 to 120 minutes after phenylephrine instillation by a maximum of 9% to 11% (P < 0.05) without significant change in intraocular pressure (IOP). A similar decrease in NB(ONH) was found in non-laser-treated eyes in glaucomatous monkeys despite the absence of significant changes in contralateral experimental glaucomatous eyes. NB(ONH) increased by 16% (P < 0.05) 60 minutes after a single instillation and also after 7-day repeated instillations of tafluprost in both eyes of normal monkeys. A similar increase in NB(ONH) occurred in both eyes after the establishment of unilateral glaucoma but was completely abolished by 5 mg/kg indomethacin injected intravenously 15 minutes after tafluprost instillation. Tafluprost significantly reduced IOP only in experimental glaucomatous eyes by 34%. CONCLUSIONS: The ONH vasculature in glaucomatous and normal eyes reacts differently to an exogenous alpha agonist, whereas it reacts similarly to an FP agonist.

Effects of prostanoid EP agonists on mouse intraocular pressure.

PURPOSE: To investigate the ocular hypotensive effect and change of outflow facilities by prostaglandin E2 (PGE2) and selective agonists of PGE2 receptor subtypes (EP1, -2, -3, -4) using C57BL/6 (wild-type [WT]) mice or FP, EP1, -2, and -3 receptor-deficient mice. METHODS: IOP was measured with a microneedle, and IOP reduction was evaluated by the difference in IOP between the treated eye and the contralateral control eye. The time course and dose dependency of IOP reduction with PGE2 and the four selective EP receptor agonists were assessed. Aqueous humor outflow facility was measured by a two-level constant-pressure perfusion RESULTS: PGE2, ONO-AE1-259-01 (EP2 agonist), and ONO-AE1-329 (EP4 agonist) significantly reduced IOP in a dose-dependent manner, whereas ONO-DI-004 (EP1 agonist) and ONO-AE-248 (EP3 agonist) had no effect. Peak IOP reduction at 2 hours with 0.1% ONO-AE1-259-01 (EP2 agonist) and ONO-AE1-329 (EP4 agonist) were 21.1% +/- 4.8% and 17.5% +/- 2.9%, respectively (P < 0.01). IOP reduction with ONO-AE1-259-01 (EP2 agonist) was completely eliminated in EP2 knockout mice, but IOP reduction in other knockout mice was similar to that observed in WT mice. The effects of ONO-AE1-259-01 (EP2 agonist) and ONO-AE1-329 (EP4 agonist) on the outflow facility were similar to those of their carrier. CONCLUSIONS: EP2 and EP4 receptors mediated IOP reduction in mice, whereas the contribution of EP1 and EP3 receptors was insignificant. The EP2 and EP4 receptor-mediated mechanisms of IOP reduction were different from those mediated by the FP receptor.

Elevated intraocular pressure, optic nerve atrophy, and impaired retinal development in ODAG transgenic mice.

PURPOSE: In an earlier study, a cDNA was cloned that showed abundant expression in the eye at postnatal day (P)2 but was downregulated at P10; it was named ODAG (ocular development-associated gene). Its biological function was examined by generating and analyzing transgenic mice overexpressing ODAG (ODAG Tg) in the eye and by identifying ODAG-binding proteins. METHODS: Transgenic mice were generated by using the mouse Crx promoter. EGFP was designed to be coexpressed with transgenic ODAG, to identify transgene-expressing cells. Overexpression of ODAG was confirmed by Northern and Western blot analysis. IOP was measured with a microneedle technique. The eyes were macroscopically examined and histologically analyzed. EGFP expression was detected by confocal microscope. Proteins associated with ODAG were isolated by pull-down assay in conjugation with mass spectrometry. RESULTS: Macroscopically, ODAG Tg exhibited gradual protrusion of the eyeballs. The mean IOP of ODAG Tg was significantly higher than that of wild-type (WT) littermates. Histologic analysis exhibited optic nerve atrophy and impaired retinal development in the ODAG Tg eye. EGFP was expressed highly in the presumptive outer nuclear layer and weakly in the presumptive inner nuclear layer in the ODAG Tg retina. Rab6-GTPase-activating protein (Rab6-GAP) and its substrate, Rab6, were identified as ODAG-binding proteins. CONCLUSIONS: Deregulated expression of ODAG in the eye induces elevated intraocular pressure and optic nerve atrophy and impairs retinal development, possibly by interfering with the Rab6/Rab6-GAP-mediated signaling pathway. These results provide new insights into the mechanisms regulating ocular development, and ODAG Tg would be a novel animal model for human diseases caused by ocular hypertension.