Twenty-four hours intraocular pressure in keratoconic eyes assessed by applanation tonometry and Tono-Pen AVIA

AIM: To assess intraocular pressure (IOP) during the daily curve of intraocular pressure (DCPo) in keratoconic eyes and compare Goldmann applanation tonometer (GAT), without and with astigmatism correction (nGAT and cGAT) and Tono-Pen AVIA (TPA) assessment methods. METHODS: Thirty-nine keratoconic eyes of 24 patients were assessed. DCPo was evaluated with five IOP measurements; four were performed with a GAT (nGAT and cGAT), and a Tono-Pen AVIA (TPA) at various times throughout the day. RESULTS: Mean IOP DCPo values (mm Hg) were: nGAT, 9.9±2.6; cGAT, 11.3±2.6; TPA 12.3±3.1. Mean IOP DCPo differences (mm Hg) and Spearman's correlation coefficients were as follows: cGATc-nGAT, 1.32±1.31, rs=0.879 (P<0.01); cGAT-TPA, -1.02±2.08, rs=0.723 (P<0.01); and nGAT-TPA, -2.35±2.23, rs=0.730 (P<0.01). Bland-Altman analysis for agreement between cGAT-TPA and nGAT-TPA mean IOP DCPo measurements revealed a mean difference of 1.02 (95%CI, 0.35-1.70) and 2.35 (95%CI, 1.62-3.07) mm Hg, respectively. Regression analysis yielded the following equation: TPA IOP=5.49+0.775×cGAT-0.015×ACD-0.299×corneal astig matism, which allowed us to infer TPA IOP values from other parameters. CONCLUSION: In keratoconic eyes, IOP peaks of DCPo measurements are identified at 6 a.m., independent of the tonometer. The mean DCPo values are: TPA>cGAT>nGAT. IOP TPA measures are predictive of cGAT values, adjusted according to anterior chamber depth and corneal astigmatism.

Observation seasonal variation of intraocular pressure in young healthy volunteers

AIM: To investigate fluctuation of intraocular pressure (IOP) and seasonal variation of 24-hour IOP during one year in healthy participants METHODS: Totally 13 young healthy volunteers participated in this study. IOP was measured with Canon TX-20 at about 8:00-9:00 a.m. from Monday to Friday every week for a whole year. They also underwent 24-hour IOP examination every three months. Blood pressure, heart rate, temperature, humidity, atmosphere pressure, sunshine duration and other environment parameters were recorded. RESULTS: The yearly fluctuation curve showed IOP in the summer months were lower than other seasons. In the multivariable generalized estimating equation analysis, IOP had a negative correlation with both temperature and sunshine duration (P<0.05). There also was a seasonal effect on 24-hour IOP. However, all intraclass correlation coefficients values of minimum, maximum and average of the 24-hour IOP and each individual IOP were less than 0.30. CONCLUSION: IOP is trend to be higher in cold days than warm days. IOP have negative association with both environmental temperature and duration of sunshine. On a season-to-season basis, 24-hour IOP is not highly reproducible in healthy volunteers.

The Relationship Between Plasma Tetrahydrocannabinol Levels and Intraocular Pressure in Healthy Adult Subjects

BackgroundΔ9-tetrahydrocannabinol (THC) has been shown to decreased intraocular pressure (IOP). This project aims to define the relationship between plasma THC levels and IOP in healthy adult subjects.MethodsEleven healthy subjects received a single dose of inhaled cannabis that was self-administered in negative pressure rooms. Measurements of IOP and plasma THC levels were taken at baseline and every 30 min for 1 h and afterwards every hour for 4 h. IOP reduction and percent change in IOP over time were calculated. Linear regression models were used to measure the relationship between IOP and plasma THC levels. Two line linear regression models with F-tests were used to detect change points in the regression. Then, Pearson correlations were computed based on the change point.ResultsTwenty-two eyes met inclusion criteria. The average peak percentage decrease in IOP was 16% at 60 min. Percent IOP reduction as well as total IOP reduction demonstrated a negative correlation with THC plasma levels showing r-values of −0.81 and −0.70, respectively. F-tests revealed a change point in the regression for plasma levels >20 ng/ml. For levels >20 ng/ml, the correlation coefficients changed significantly with r-values of 0.21 and 0.29 (p < 0.01).ConclusionPlasma THC levels are significantly correlated with IOP reduction up to plasma levels of 20 ng/ml. Plasma levels >20 ng/ml were not correlated with further decrease in IOP. More research is needed to determine the efficacy of THC in reducing IOP for eyes with ocular hypertension and glaucoma.

Ex-Press® Surgery Versus Trabeculectomy for Primary Open Angle Glaucoma with Low Preoperative Intraocular Pressure

Purpose: To compare surgical outcomes between Ex-PRESS® surgery (EXP) and trabeculectomy (Trab) for primary open angle glaucoma (POAG) with low preoperative intraocular pressure (IOP).Patients and Methods: This was a retrospective non-randomized study. We included POAG patients with preoperative IOP ≤16 mmHg who were taking tolerance glaucoma medications. We compared the surgical outcomes, postoperative IOP, number of glaucoma medications, reduction rate of corneal endothelial cell density (ECD), visual acuity, and postoperative complications between POAG patients who underwent EXP (34 eyes) or Trab (38 eyes) and could be followed for >2 years.Results: Both surgeries significantly decreased the IOP (p<0.001): at 2 years, EXP provided decreases from 13.4 ± 2.3 to 10.2 ± 3.1 mmHg, Trab provided decreases from 13.5 ± 2.0 to 8.9 ± 3.2 mmHg. No significant differences were observed in the postoperative IOP (p=0.076), number of postoperative medications (p=0.263), success rate (p=0.900), reduction rate of ECD (p=0.410), or difference in visual acuity (p=0.174). The reduction rate of IOP was significantly high in the Trab group (p=0.047).Conclusions: Both surgeries significantly decreased IOP and were useful surgical methods for low-IOP glaucoma. Our results suggest that trabeculectomy can decrease IOP more than Ex-PRESS surgery but might have more complications.

Relationships between Intraocular Pressure, Effective Filtration Area and Morphological Changes in the Trabecular Meshwork of Steroid-Induced Ocular Hypertensive Mouse Eyes

We investigated whether an inverse relationship exists between intraocular pressure (IOP) and effective filtration area (EFA) in the trabecular meshwork (TM) in a steroid-induced ocular hypertensive (SIOH) mouse model and the morphological changes associated with the reduction of EFA. C57BL/6 mice (n = 15 per group) received either 0.1% dexamethasone (DEX) or saline eye drops twice daily for five weeks. IOP was measured weekly. Fluorescent tracers were injected into the anterior chamber to label EFA at the endpoint. Injected eyes were fixed and processed for confocal microscopy. EFA in the TM was analyzed. Light and electron microscopy were performed in high- and low-tracer regions of six eyes per group. The mean IOP was ~4 mm Hg higher in DEX-treated than saline-treated control eyes (p < 0.001) at the endpoint. EFA was reduced in DEX-treated eyes compared to controls (p < 0.01) and negatively correlated with IOP (R2 = 0.38, p = 0.002). Reduced thickness of juxtacanalicular tissue (JCT) and increased abnormal extracellular matrix in the JCT were found to be associated with reduced EFA. Our data confirm the inverse relationship between EFA and IOP, suggesting that morphological changes in the JCT contribute to the reduction of EFA, thus elevating IOP in SIOH mouse eyes.

Endothelial Tyrosine Kinase Tie1 Is Required for Normal Schlemm’s Canal Development

Background: Schlemm’s canal (SC) is a large vessel residing in the iridocorneal angle and is required to regulate aqueous humor outflow. Normal SC structure and function is indispensable for maintaining normal intraocular pressure, and elevated intraocular pressure is a risk factor for development of glaucoma. Recent reports have identified a key role of the angiopoietin-Tie2 pathway for SC development and function; however, the role of the orphan receptor Tie1 has not been clarified. Methods: We used Tie1 knock out mice to study the function of Tie1 in SC development and function. Real-time quantitative polymerase chain reaction and Western blot analyses were used to verify Tie1 deletion. High-resolution microscopy of mouse SC whole mount and cross sections were used to study SC morphology. Measurement of intraocular pressure in live mice was used to study the impact of Tie1 on SC function. Results: Tie1 is highly expressed in both human and mouse SC. Tie1 knock out mice display hypomorphic SC and elevated intraocular pressure as a result of attenuated SC development. Conclusions: Tie1 is indispensable for SC development and function, supporting it as a novel target for future SC-targeted glaucoma therapies and a candidate gene for glaucoma in humans.

The Effect of Anabasis articulata Stems Extract on Lowering Intraocular Pressure in the Glaucoma Rat Model(Conference Paper )#

High intraocular pressure (IOP) is a recognized risk factor for glaucoma and optic nerve injury, and it is one of the primary causes of vision loss globally. Anabasis articulata (AA) is a desert plant found in Iraq. The extract of AA is used to cure diabetes, fever, eczema, and kidney infections. The aim of the study is to evaluate the antioxidant effect of methanol extract of AA on intraocular pressure in the glaucoma rat model. Forty-two rats were allocated into seven groups, each with six animals:: group 1 (normal), group 2 (control), in which animals were induced to have elevated IOP by betamethasone suspension injection, groups 3,4 and 5 for evaluating the effect of 50,100 and 150 mg/kg/day of the tested extract, respectively, and the remaining two groups (group 6 and 7) for evaluating oral acetazolamide and topical timolol 0.5% respectively. Betamethasone was used for the induction. Measure the IOP every 2 days for 2 weeks. The daily dose of AA extract (50 mg/kg/day) for 6 days significantly reduces intraocular pressure (p ? 0.05), from (34.23± 0.58) to (32.83± 1.38) mmHg when compared with the control group. In group 4, IOP decreased significantly from (35.5±1.37) to (31.35±0.40) mmHg (p ? 0.05) after 1 week of treatment. In group 5, the significant (p? 0.001) IOP reduction from (35.66±0.39) to (31.88±0.74) mmHg started on day 6 and continued until the end of the experiment, reaching (24.53±0.53) mmHg (p? 0.001). The antioxidant and anti-angiogenic properties of AA make it a promising adjuvant treatment for glaucoma.