Displaying all 14 publications

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  1. Samsudin A, Eames I, Brocchini S, Khaw PT
    J Glaucoma, 2016 Jan;25(1):e39-45.
    PMID: 25719236 DOI: 10.1097/IJG.0000000000000243
    PURPOSE: ExPress devices are available as P50 and P200 models, the numbers related to their luminal diameters in μm. We compared their Poiseuille's Law-based theoretical resistance values with experimental values and correlated these with their luminal dimensions derived from electron microscopy.

    METHODS: Scanning electron microscopy was performed on P50 and P200 devices. Bench-top flow studies were performed to find the resistances of the devices. Devices were also incorporated into a perfused, ex vivo porcine sclera model to test and compare their control of pressure, with and without overlying scleral flaps, and with trabeculectomies.

    RESULTS: The luminal dimensions of the P200 device were 206.4±3.3 and 204.5±0.9 μm at the subconjunctival space and anterior chamber ends, respectively. Those of the P50 device were 205.0±5.8 and 206.9±3.7 μm, respectively. There were no significant differences between the P200 and P50 devices (all P>0.05). The resistances of the P200 and P50 devices were 0.010±0.001 and 0.054±0.002 mm Hg/μL/min, respectively (P<0.05). Equilibrium pressures with overlying scleral flaps were 17.81±3.30 mm Hg for the P50, 17.31±4.24 mm Hg for the P200, and 16.28±6.67 mm Hg for trabeculectomies (P=0.850).

    CONCLUSIONS: The luminal diameters of both devices are externally similar. The effective luminal diameter of the P50 is much larger than 50 μm. Both devices have low resistance values, making them unlikely to prevent hypotony on their own. They lead to similar equilibrium pressures as the trabeculectomy procedure when inserted under the scleral flap.

    Matched MeSH terms: Glaucoma/physiopathology
  2. Samsudin A, Eames I, Brocchini S, Khaw PT
    J Glaucoma, 2016 07;25(7):e704-12.
    PMID: 26561421 DOI: 10.1097/IJG.0000000000000360
    PURPOSE: Intraocular pressure and aqueous humor flow direction determined by the scleral flap immediately after trabeculectomy are critical determinants of the surgical outcome. We used a large-scale model to objectively measure the influence of flap thickness and shape, and suture number and position on pressure difference across the flap and flow of fluid underneath it.

    METHODS: The model exploits the principle of dynamic and geometric similarity, so while dimensions were up to 30× greater than actual, the flow had similar properties. Scleral flaps were represented by transparent 0.8- and 1.6-mm-thick silicone sheets on an acrylic plate. Dyed 98% glycerin, representing the aqueous humor was pumped between the sheet and plate, and the equilibrium pressure measured with a pressure transducer. Image analysis based on the principle of dye dilution was performed using MATLAB software.

    RESULTS: The pressure drop across the flap was larger with thinner flaps, due to reduced rigidity and resistance. Doubling the surface area of flaps and reducing the number of sutures from 5 to 3 or 2 also resulted in larger pressure drops. Flow direction was affected mainly by suture number and position, it was less toward the sutures and more toward the nearest free edge of the flap. Posterior flow of aqueous humor was promoted by placing sutures along the sides while leaving the posterior edge free.

    CONCLUSION: We demonstrate a new physical model which shows how changes in scleral flap thickness and shape, and suture number and position affect pressure and flow in a trabeculectomy.

    Matched MeSH terms: Glaucoma/physiopathology
  3. Ramli N, Nurull BS, Hairi NN, Mimiwati Z
    Prev Med, 2013;57 Suppl:S47-9.
    PMID: 23352960 DOI: 10.1016/j.ypmed.2013.01.007
    In the absence of raised intraocular pressure (IOP), haemodynamic parameters have been implicated in the development of normal tension glaucoma (NTG). The purpose of this study is to compare 24-hour IOP and haemodynamic parameters in NTG patients and non-glaucoma patients.
    Matched MeSH terms: Low Tension Glaucoma/physiopathology
  4. Wong EY, Chew PT, Chee CK, Wong JS
    Am J Ophthalmol, 1997 Dec;124(6):797-804.
    PMID: 9402826
    PURPOSE: To evaluate the effectiveness and safety of diode laser contact transscleral cyclophotocoagulation in Asian patients with refractory glaucoma by lower energy settings with an innovative probe featuring a glass ball tip that focused the laser beam onto the ciliary body.

    METHODS: This prospective clinical study included consecutive Asian patients with dark irides and confirmed for glaucoma. Only one eye of each patient was treated. Diode laser contact transscleral cyclophotocoagulation treatment was performed with the center of the probe placed 1.5 mm behind the limbus. About 30 pulses of 810-mm laser radiation (power, 1.8 to 2.0 W; duration, 0.3 to 0.5 second) were applied around the eye. Patients were examined at fixed postoperative intervals. Intraocular pressure levels and postoperative complications were recorded. The relation between patient and disease characteristics, total laser energy delivered, and intraocular pressure effects were analyzed.

    RESULTS: Thirty-three patients were studied, with a mean follow-up period of 9.4 months. An average 56% of patients showed a 30% or greater drop in intraocular pressure. About 38% of patients achieved sustained intraocular pressure lowering to below 22 mm Hg at 18 months. Complications were few and included transient hypotony and iritis.

    CONCLUSIONS: In Asian patients with refractory glaucoma or painful glaucomatous eyes with poor visual acuity (defined for this study as worse than 20/200), low-energy-setting diode laser contact transscleral cyclophotocoagulation by means of the glass ball probe is relatively effective and safe.

    Matched MeSH terms: Glaucoma/physiopathology
  5. Agarwal P, Agarwal R
    Expert Opin Ther Targets, 2018 07;22(7):629-638.
    PMID: 29883239 DOI: 10.1080/14728222.2018.1486822
    INTRODUCTION: Disturbances of extracellular matrix (ECM) homeostasis in trabecular meshwork (TM) cause increased aqueous outflow resistance leading to elevated intraocular pressure (IOP) in glaucomatous eyes. Therefore, restoration of ECM homeostasis is a rational approach to prevent disease progression. Since renin-angiotensin system (RAS) inhibition positively alters ECM homeostasis in cardiovascular pathologies involving pressure and volume overload, it is likely that RAS inhibitors reduce IOP primarily by restoring ECM homeostasis. Areas covered: Current evidence showing the presence of RAS components in ocular tissue and its role in regulating aqueous humor dynamics is briefly summarized. The role of RAS in ECM remodeling is discussed both in terms of its effects on ECM synthesis and its breakdown. The mechanisms of ECM remodeling involving interactions of RAS with transforming growth factor-β, Wnt/β-catenin signaling, bone morphogenic proteins, connective tissue growth factor, and matrix metalloproteinases in ocular tissue are discussed. Expert opinion: Current literature strongly indicates a significant role of RAS in ECM remodeling in TM of hypertensive eyes. Hence, IOP-lowering effect of RAS inhibitors may primarily be attributed to restoration of ECM homeostasis in aqueous outflow pathways rather than its vascular effects. However, the mechanistic targets for RAS inhibitors have much wider distribution and consequences, which remain relatively unexplored in TM.
    Matched MeSH terms: Glaucoma/physiopathology
  6. Fang SY, Wan Abdul Halim WH, Mat Baki M, Din NM
    Graefes Arch Clin Exp Ophthalmol, 2018 Apr;256(4):783-790.
    PMID: 29492688 DOI: 10.1007/s00417-018-3919-7
    PURPOSE: Obstructive sleep apnea syndrome (OSAS) patients are at risk of glaucoma but the risk increases if they have higher intraocular pressure (IOP) while sleeping. We aim to evaluate the postural effect of upright and prolong supine positions on IOP in these patients.

    METHODS: This is a cross-sectional study involving 27 patients with symptoms of OSAS seen at a tertiary institutional center and 25 normal controls performed between June 2015 and June 2016. All patients and controls underwent a polysomnography (PSG) test and were diagnosed with OSAS based on the apnea-hypopnea index (AHI). Patients are those with OSAS symptoms and had AHI > 5, whereas controls are staffs from the ophthalmology clinic without clinical criteria for OSAS and had PSG result of AHI

    Matched MeSH terms: Glaucoma/physiopathology
  7. Raman P, Suliman NB, Zahari M, Kook M, Ramli N
    Eye (Lond), 2018 07;32(7):1183-1189.
    PMID: 29491486 DOI: 10.1038/s41433-018-0057-8
    OBJECTIVE: To assess the relationship between baseline intraocular pressure (IOP), blood pressure (BP) and ocular perfusion pressure (OPP), and the 5-year visual field progression in normal-tension glaucoma (NTG) patients.

    DESIGN: Prospective, longitudinal study.

    METHODS: Sixty-five NTG patients who were followed up for 5 years are included in this study. All the enrolled patients underwent baseline 24-h IOP and BP monitoring via 2-hourly measurements in their habitual position and were followed up for over 5 years with reliable VF tests. Modified Anderson criteria were used to assess VF progression. Univariable and multivariable analyses using Cox's proportional hazards model were used to identify the systemic and clinical risk factors that predict progression. Kaplan-Meier survival analyses were used to compare the time elapsed to confirmed VF progression in the presence or absence of each potential risk factor.

    RESULTS: At 5-year follow-up, 35.4% of the enrolled patients demonstrated visual field progression. There were statistically significant differences in the mean diastolic blood pressure (p  43.7 mmHg (log rank = 0.018).

    CONCLUSION: Diastolic parameters of BP and OPP were significantly lower in the NTG patients who progressed after 5 years. Low nocturnal DOPP is an independent predictor of glaucomatous visual field progression in NTG patients.

    Matched MeSH terms: Low Tension Glaucoma/physiopathology*
  8. Ting SL, Lim LT, Ooi CY, Rahman MM
    Asia Pac J Ophthalmol (Phila), 2019;8(3):229-232.
    PMID: 31165604 DOI: 10.22608/APO.2018433
    PURPOSE: To compare the measurement of intraocular pressure (IOP) of Icare rebound tonometer and Perkins applanation tonometer (PAT) during community eye screening and to assess the agreement between these 2 instruments.

    DESIGN: A cross-sectional, non-interventional study.

    METHODS: The IOP measurements by handheld Icare rebound tonometer (Finland) were first performed by a primary care physician. Then the IOP was measured using Perkins Mk3 applanation tonometer (Haag-Streit, UK) by an ophthalmologist who was masked to previous readings from the Icare rebound tonometer. The mean IOP measured by each tonometer was compared. Pearson correlation coefficient was used to explore the correlation between the IOP measurements of the 2 instruments. The level of agreement between them was assessed using the Bland and Altman method.

    RESULTS: A total of 420 left eyes were examined. The mean age of subjects was 38.6 ± 18.2 years. Approximately 67% of subjects were female. The mean IOP was 16.3 ± 4.0 mm Hg using Icare and 13.4 ± 2.3 mm Hg using PAT. Pearson correlation coefficient showed a moderate positive correlation between the 2 methods (r = +0.524, P < 0.001). Linear regression analysis revealed a slope of 0.28 with R² of 0.255. The mean difference between the 2 methods was 2.90 ± 3.5 mm Hg and the sample t-test revealed a statistically significant mean difference from 0 (P < 0.001). The 95% limits of agreement between the 2 methods were between -9.73 and 3.93 mm Hg.

    CONCLUSIONS: The handheld Icare rebound tonometer is a reasonably acceptable screening tool in community practices. However, Icare overestimated IOP with a mean of 2.90 mm Hg higher than the PAT. Thus, using Goldmann applanation tonometer as a confirmatory measurement tool of IOP is suggested.

    Matched MeSH terms: Glaucoma/physiopathology
  9. Chan EW, Chiang PP, Wong TY, Saw SM, Loon SC, Aung T, et al.
    Invest Ophthalmol Vis Sci, 2013 Feb;54(2):1169-75.
    PMID: 23341009 DOI: 10.1167/iovs.12-10258
    We determined the impact of glaucoma severity and laterality on vision-specific functioning (VF) in an Asian population.
    Matched MeSH terms: Glaucoma/physiopathology*
  10. Raman P, Suliman NB, Zahari M, Mohamad NF, Kook MS, Ramli N
    J Glaucoma, 2019 11;28(11):952-957.
    PMID: 31688446 DOI: 10.1097/IJG.0000000000001359
    PRECIS: This 5-year follow-up study on normal-tension glaucoma (NTG) patients demonstrated that those with baseline central visual field (VF) defect progress at a more increased rate compared with those with peripheral field defect.

    PURPOSE: The purpose of this study was to investigate the clinical characteristics, including 24-hour ocular perfusion pressure and risk of progression in patients with baseline central VF defect, as compared with those with peripheral VF defect in NTG.

    DESIGN: This was a prospective, longitudinal study.

    METHODS: A total of 65 NTG patients who completed 5 years of follow-up were included in this study. All the enrolled patients underwent baseline 24-hour intraocular pressure and blood pressure monitoring via 2-hourly measurements in their habitual position and had ≥5 reliable VF tests during the 5-year follow-up. Patients were assigned to two groups on the basis of VF defect locations at baseline, the central 10 degrees, and the peripheral 10- to 24-degree area. Modified Anderson criteria were used to assess global VF progression over 5 years. Kaplan-Meier analyses were used to compare the elapsed time of confirmed VF progression in the two groups. Hazard ratios for the association between clinical risk factors and VF progression were obtained by using Cox proportional hazards models.

    RESULTS: There were no significant differences between the patients with baseline central and peripheral VF defects in terms of demography, clinical, ocular and systemic hemodynamic factors. Eyes with baseline defects involving the central fields progressed faster (difference: βcentral=-0.78 dB/y, 95% confidence interval=-0.22 to -1.33, P=0.007) and have 3.56 times higher hazard of progressing (95% confidence interval=1.17-10.82, P=0.025) than those with only peripheral defects.

    CONCLUSION: NTG patients with baseline central VF involvement are at increased risk of progression compared with those with peripheral VF defect.

    Matched MeSH terms: Low Tension Glaucoma/physiopathology
  11. Md Din N, Tomkins-Netzer O, Talat L, Taylor SR, Isa H, Bar A, et al.
    J Glaucoma, 2016 07;25(7):598-604.
    PMID: 26900824 DOI: 10.1097/IJG.0000000000000379
    PURPOSE: To determine risk factors for intraocular pressure (IOP) elevation and glaucoma in children with nonjuvenile idiopathic arthritis-related uveitis and any IOP-related changes in the retinal nerve fiber layer (RNFL) thickness.

    PATIENTS AND METHODS: Clinical data were collected from children attending a tertiary referral uveitis clinic between May 2010 and October 2012. We assigned 206 eyes of 103 children into 32 normal eyes, 108 normotensive uveitics (NU), 41 hypertensive uveitics (HU: raised IOP without glaucomatous disc), and 25 glaucomatous uveitics (GU: raised IOP with glaucomatous disc). Risk factors for raised IOP, glaucoma and steroid response (SR) were evaluated and RNFL thickness across groups was compared with determine changes related to raised IOP.

    RESULTS: IOP elevation occurred in 40 patients (38.8%) or 66/174 eyes with uveitis (37.9%); and SR occurred in 35.1% of all corticosteroid-treated eyes. Chronic uveitis was a significant risk factor for raised IOP [odds ratio (OR)=9.28, P=0.001], glaucoma, and SR (OR=8.4, P<0.001). Higher peak IOP was also a risk factor for glaucoma (OR=1.4, P=0.003). About 70% of SR eyes were high responders (IOP increase >15 mm Hg from baseline), associated with younger age and corticosteroid injections. Although no significant RNFL thinning was detected between HU and NU eyes, significant thinning was detected in the inferior quadrant of GU (121.3±28.9 μm) compared with NU eyes (142.1±32.0 μm, P=0.043).

    CONCLUSIONS: Children with chronic uveitis are at higher risk of raised IOP and glaucoma. Thinning of the inferior RNFL quadrant may suggest glaucomatous changes in uveitic children with raised IOP.

    Study site: Moorfields Eye Hospital, London
    Matched MeSH terms: Glaucoma/physiopathology*
  12. Din NM, Talat L, Isa H, Tomkins-Netzer O, Barton K, Lightman S
    Graefes Arch Clin Exp Ophthalmol, 2016 Dec;254(12):2439-2448.
    PMID: 27495303
    PURPOSE: To determine whether the second eyes (SE) of patients with bilateral uveitic glaucoma undergoing filtration surgery have more glaucomatous progression in terms of visual acuity, visual field (VF) and optic nerve changes compared to the first eyes (FE).

    METHODS: This retrospective study analysed data of 60 eyes from 30 patients with bilateral uveitic glaucoma who had undergone glaucoma surgery in both eyes on separate occasions. Humphrey VF progression was assessed using the Progressor software.

    RESULTS: The pre-operative IOP between the FE (43.1 ± 7.7 mmHg) and SE (40 ± 8.7 mmHg) was not statistically significant (p = 0.15). IOP reduction was greater in the FE (64 %) than SE (59.7 %) post-operatively, but the mean IOP at the final visit in the FE (12.3 ± 3.9 mmHg) and SE (14.5 ± 7 mmHg) was not statistically different (p = 0.2). There was no significant change in mean logMAR readings pre and post-operatively (0.45 ± 0.6 vs 0.37 ± 0.6, p = 0.4) or between the FE and SE. The number of SE with CDR > 0.7 increased by 23 % compared to the FE. From 23 available VFs, five SE (21.7 %) progressed at a median of five locations (range 1-11 points) with a mean local slope reduction of 1.74 ± 0.45 dB/year (range -2.39 to -1.26), whereas only one FE progressed. However, there was no significant difference between mean global rate of progression between the FE (-0.9 ± 1.6 dB/year) and SE (-0.76 ± 2.1 dB/year, p = 0.17) in the Humphrey VF.

    CONCLUSION: In eyes with bilateral uveitic glaucoma requiring glaucoma surgery, the SEs had more progressed points on VF and glaucomatous disc progression compared to FEs at the final visit.

    Matched MeSH terms: Glaucoma/physiopathology
  13. Raman P, Khy Ching Y, Sivagurunathan PD, Ramli N, Mohd Khalid KH
    J Glaucoma, 2019 08;28(8):685-690.
    PMID: 31033782 DOI: 10.1097/IJG.0000000000001269
    PRECIS: This prospective cross-sectional study found that patients with cognitive impairment (CI) are more likely to produce unreliable visual field (VF) tests, especially with higher false-negative (FN) responses and consequent overestimation of mean deviation (MD).

    AIM: Aging-associated CI can impair the ability of individuals to perform a VF test and compromise the reliability of the results. We evaluated the association between neurocognitive impairment and VF reliability indices in glaucoma patients.

    METHODS: This prospective, cross-sectional study was conducted in the Ophthalmology Department, Hospital Kuala Pilah, Malaysia, and included 113 eyes of 60 glaucoma patients with no prior diagnosis of dementia. Patients were monitored with the Humphrey Visual Field Analyzer using a 30-2 SITA, standard protocol, and CI was assessed using the clock drawing test (CDT). The relationships between the CDT score, MD, pattern standard deviation, Visual Field Index (VFI), fixation loss (FL), false-positive values, and FN values were analyzed using the ordinal regression model.

    RESULTS: Glaucoma patients older than 65 years had a higher prevalence of CI. There was a statistically significant correlation between CDT scores and glaucoma severity, FL, FN, and VFI values (rs=-0.20, P=0.03; rs=-0.20, P=0.04; rs=-0.28, P=0.003; rs=0.21, P=0.03, respectively). In a multivariate model adjusted for age and glaucoma severity, patients with lower FN were significantly less likely to have CI (odds ratio, 0.91; 95% confidence interval, 0.89-0.93) and patients with higher MD were more likely to have CI (odds ratio, 1.10; 95% confidence interval, 1.05-1.16); false positive, FL, pattern standard deviation, and VFI showed no significant correlation.

    CONCLUSION: Cognitive decline is associated with reduced VF reliability, especially with higher FN rate and overestimated MD. Screening and monitoring of CI may be important in the assessment of VF progression in glaucoma patients.

    Matched MeSH terms: Glaucoma/physiopathology
  14. Agarwal R, Agarwal P
    Expert Opin Ther Targets, 2014 May;18(5):527-39.
    PMID: 24579961 DOI: 10.1517/14728222.2014.888416
    The homeostatic role of adenosine in regulating intraocular pressure (IOP) is now widely recognized, and hence, the drugs targeting adenosine receptors have become the focus of investigation. In this review, we summarize the adenosine receptor signaling pathways, which could be potential therapeutic targets for the management of glaucoma.
    Matched MeSH terms: Glaucoma/physiopathology
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