Influence On Intraocular Pressure Research Articles

Effect of Pars Plana Vitrectomy on Central Corneal Thickness and Its Influence onIntraocular Pressure

Purpose: To determine the effect of Pars Plana Vitrectomy on the central corneal thickness(CCT)and its influence on intraocular pressure(IOP). Study Design: Interventional case series. Place and Duration of Study: This research was conducted at Ibrahim Eye Hospital, Karachi, Pakistan, from October 2022 to March 2023. Methods: Forty-one patients of either sexpresenting with posterior segment disease and planned for Pars Plana vitrectomy (PPV) were selected after written informed consent. Pre and post-operative comparison of CCT and IOP was done using paired t-test. Follow-up of readings was done by repeated measures ANOVA test. BCVA measurements were based on the Snellen chart and were converted to the logarithm of the minimum angle of resolution (logMAR) scale for statistical analysis. Results: CCT and IOP of the affected eyes were increased considerably in the first post-operative week (CCT=591 ± 1.5,IOP=28 ± 1.5)and decreased significantly in the 3rd month(CCT=527 ± 1.34, IOP=13 ± 2.5). The change was insignificant at 6thmonth follow-up. BCVA was improved in first week (626 ± 1.34) and remained same throughout the follow-up period. Maximum change in CCT (ΔCCT)was found in age <15 years and in aphakic eyes (119 ± 0.09). Conclusion: Pars Plana vitrectomy causes significant change in CCTwhich can influenceIOP. This change should be kept in mind to prevent false diagnosis of glaucoma in the early post-operative period of PPV. Young patients and Aphakic eyes are more prone to the corneal changes.

Ex vivo biophysical characterization of a hydrogel-based artificial vitreous substitute.

PurposeTo characterize the biophysical properties of an artificial vitreous body substitute (VBS), which consists of a biocompatible, cross-linked, hyaluronic acid (HA)-based hydrogel, by analysing the VBS’s influence on intraocular pressure (IOP) and retinal integrity in distinct ex vivo eye models in order to evaluate the its potential for in vivo biocompatibility testing.MethodsPig eyes were obtained immediately postmortem, and VBS was injected after core-vitrectomy. IOP was followed for 24 h (n = 5). VBS influence on retinal integrity was investigated using isolated bovine retinas superfused with an oxygen saturated nutrient solution. An electroretinogram (ERG) was recorded on explanted bovine retinae using silver/silver chloride electrodes; after application of VBS for 2 min, a washout period of 70 min was employed. The percentage of a-and b-wave reduction at the end of the washout phase was compared to baseline values (n = 5). Data were calculated throughout as the mean and the standard deviation. qRT-PCR (Bax/Bcl–2-ratio, GFAP- and PGP9.5-levels) or western blot analysis was used to test for toxicity of Princess Volume after 24 h (and β-3 tubulin with GAPDH as a control gene). Significance was estimated by Student´s t-test; p ≤0.05 was considered to be statistically significant.ResultsThe IOP increased non-significantly by 10% after 24 h. Short-term biocompatibility testing using isolated superfused bovine retinas showed neither significant reductions of the b-wave nor the a-wave amplitudes (b-wave reduction 14.2%, p>0.05; a-wave reduction 23.9%, p>0.05). qRT-PCR and western blot analysis did not reveal significant toxicity after 24 h.ConclusionsThe manufactured HA-based hydrogel showed highly favourable biophysical characteristics in the explored ex vivo models, justifying in vivo studies enabling the assessment of biocompatibility.

Influence of eye biometrics and corneal micro-structure on noncontact tonometry.

PurposeTonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements.MethodsFifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG) distribution that is characterised with a scale parameter and two shape parameters.ResultsIn macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R2 = 0.25, p<0.001). The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R2 = 0.19, p<0.001 and R2 = 0.17, p<0.001, respectively). For the studied group, a weak, although significant correlation was found between age and IOP (R2 = 0.053, p = 0.04). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R2 = 0.39, p<0.001) to study the role of the corneal structure on IOP.ConclusionsWe show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro-structure and hence, to further calibrate the IOP measurements.

Agreement between Central Corneal Thickness Measured Using Pentacam, Ultrasound Pachymetry, Specular Microscopy and Optic Biometer Lenstar LS 900 and the Influence of Intraocular Pressure

Purpose: To compare central corneal thickness (CCT) values obtained by Lenstar (LE), Pentacam (PC), specular microscopy (SM) and ultrasound pachymetry (UP) in healthy corneas and study their influence on intraocular pressure (IOP) readings determined by Goldmann applanation tonometry (GAT). Methods: CCT was measured in 76 healthy subjects by LE, PC, SM and UP. We established Lin's concordance correlation coefficient (ρ-C) between different techniques. The influence of CCT on GAT was established through univariate linear regression models, IOP being the dependent variable. Results: The highest ρ-C was found between LE and SM at 0.94 (95% CI: 0.91-0.96) and between LE and UP at 0.95 (95% CI: 0.94-0.97). IOP readings showed less variability when CCT was determined using LE (7.7%, B = 0.16; 95% CI: 0.004-0.28). Conclusions: Although CCT values obtained with UP, PC, SM and LE show good correlation, these methods are not completely interchangeable. The amount of IOP variation differs when CCT is determined using LE or SM.

Selective Laser Trabeculoplasty Following Failed Combined Phacoemulsification Cataract Extraction and Ab Interno Trabeculectomy

To assess the effect of selective laser trabeculoplasty (SLT) following failed phacoemulsification cataract extraction combined with ab interno trabeculectomy (AIT) using the Trabectome (phaco-trabectome). Randomized, interventional case series. Retrospectively, the medical records of patients who underwent SLT between March 2010 and July 2012 by 1 surgeon at a single center after a failed phaco-AIT were evaluated. Inclusion criteria were age ≥18 years with no upper limit and prior failed phaco-AIT attributable to glaucoma progression. Exclusion criterion was performance of any additional glaucoma procedure with influence on intraocular pressure (IOP) during follow-up and a follow-up after surgery of <3 months. Success was defined by reduction of IOP of >3 mm Hg and 20% and number of antiglaucoma medications equal to or less than baseline. Main outcome measures were IOP, antiglaucoma medications, time to failure, and Kaplan-Meier survival curve. Fourteen eyes of 13 subjects were included. Mean follow-up after SLT was 12.9 ± 8.7 months. Total laser energy was 59.5 ± 8.7 mJ. Baseline IOP was 17.9 ± 3.3 mm Hg and number of antiglaucoma medications at baseline was 2.0 ± 1.0. All SLT procedures failed. Median time to failure after SLT was 3.6 ± 0.8 (range 2.1-5.1) months. Number of antiglaucoma medications did not change. In eyes in which the IOP was no longer controlled following phaco-trabectome, SLT had a limited duration of significant IOP-lowering effect. Other alternatives, such as incisional filtration surgery, should be considered following failed phaco-trabectome.

Influence of topical Iotemax on intraocular pressure following excimer laser corneal refractive surgery

Background Excimer laser corneal refractive surgery is widely used because it reduces the dependency of refractive error eye to glasses.However,the adverse effects of anti-inflammatory drugs is a problem after operation.Lotemax eyedrops is a kind of steroidal anti-inflammatory drug,with a good effect on the operative eye.But its influence on intraocular pressure(IOP) after long-term topical administration is less studied.Objective This study was to investigate the influence of lotemax eyedrops on IOP after long-term topical administration in myopic eyes received excimer laser corneal refractive surgery.Methods An one-month retrospective case serial study was adopted.The case history data of 1552 eyes from 1552 Patients who received excimer laser corneal refractive surgery were collected in Tangshan Eye Hospital from 2011 January to 2012 January,including 321 eyes with laser in situ keratomileusis(LASIK),608 eyes with sub-Bowman keratomileusis (SBK) and 623 eyes with femtosecond laser for flap excimer laser in situ keratomileusis(FS-LASIK).Lotemax eyedrops was topically administered after operation 4 times per day initial and then decreased 1 time weekly for 1 month.IOP was measured in before,1 week,2 weeks,3 weeks,4 weeks after operation with non-contact tonometer.The increasing range of IOP was divided into ＜5 mmHg,5-15 mmHg and ＞ 15 mmHg after operation.Optical head parameters were measured by Heidelberg retina tomography when IOP increasing after operation.Results Within 1 month,elevated IOP was found in 47 of 1552 eyes after administration of lotemax eyedrops,including 3.12％ (10/321) in the LASIK group,3.29％ (20/608) in the SBK group and 2.73％ (17/623) in the FS-LASIK group,without significant difference among them(x2 =1.95,P＞0.05).The IOP elevated 1 week after operation and remained normal after that till drug withdrawal in all eyes.There were no significant differences in the disk area (1.65 ±0.44) mm2 vs.(1.66 ±0.44) mm2,disk volume (0.40 ±0.09)mm3 vs.(0.39±0.08) mm3 and mean nerve fiber layer thickness (0.28 ± 0.08) mm vs.(0.29 ± 0.07) mm in IOP elevation duration compared with 1 month after IOP recovery(t =0.34,0.81,0.48,P＞0.05).Conclusions Topical administration of 0.5％ lotemax eyedrops after excimer laser corneal refractive surgery leads to reversible high IOP.It is very important to monitor the IOP during use of the drug. Key words: Lotemax eyedrops; Excimer laser corneal refractive surgery/ laser in situ keratomileusis, Sub-Bowman keratomileusis, Femtosecond laser for flap excimer laser in situ keratomileusis; Intraocular pressure

An Ultrasound Biomicroscopy Study of Filtering Blebs after Deep Sclerectomy with a New Acrylic Implant

To identify the clinical and anatomic characteristics of filtering blebs after nonpenetrating deep sclerectomy (NPDS) using ultrasound biomicroscopy, and to evaluate its influence on intraocular pressure (IOP) control. We conducted a prospective interventional case series in 18 eyes of 18 patients who had undergone nonpenetrating deep sclerectomy with Esnoper® implant. A complete ophthalmic examination and ultrasound biomicroscopy (UBM) exploration were performed at 1, 3, and 6 months postoperatively. Intraocular pressure significantly decreased from a mean of 23.5 mmHg (SD 3.5) preoperatively to a mean of 13.1 mmHg (SD 7.6), 13.2 mmHg (SD 4.3), and 13.3 mmHg (SD 3) at 1, 3, and 6 months postoperatively, respectively. At 6 months, lower IOP levels significantly correlated with hyporeflective blebs (r=-0.82, p=0.000), with the presence of hyporeflective suprachoroidal space (r=-0.67, p=0.003) and with the presence of hyporeflective area around the scleral lake (r=-0.55, p=0.02). The presence of these 3 filtration signs together correlated with lower IOP levels compared with the presence of only 1 or 2 (p=0.000, p=0.004, p=0.0005) at 1, 3, and 6 months postoperatively, respectively. A thinner trabeculo-descemetic membrane (TDM) was significantly correlated with lower postoperative IOP value at the first postoperative month (r=0.45, p=0.05). Intraocular pressure mean values and UBM characteristics were not significantly different between eyes with single NPDS and eyes following combined NPDS-phacoemulsification. At 6 months, eyes without goniopuncture had lower IOP values (p=0.02), higher bleb (p=0.015), and thinner TDM (p=0.01) than those needing goniopuncture. Ultrasound biomicroscopy is a useful method to evaluate outflow mechanisms after NPDS and their correlation with postoperative IOP control.

Intraocular pressure changes in patients undergoing cataract extraction and lens implantation: laryngeal mask airway versus endotracheal tube

ABSTRACTObjectives: To investigate the influence on intraocular pressure (IOP) of airway management with a laryngeal mask airway (LMA) or tracheal tube (ETT), and secondly to compare the devices with regard to their impact on IOP.Design: Prospective, randomized observational study over a four-month period (August—November 2002)Setting: University-affiliated tertiary level hospital in Pretoria, South AfricaSubjects: Forty ASA I and II adult patients undergoing unilateral cataract extraction and lens implantation under general anaesthesiaOutcome measures: Changes in intraocular pressure after placement of airway deviceMethods: Following a standard anaesthestic induction with propofol and atracurium, airway management was randomized to LMA or ETT.IOP was measured pre-induction, 3 min post induction but before airway manipulation, 20 sec post LMA or ETT insertion and finally 2 min post airway instrumentation.Results: There was a small increase in mean IOP in the LMA group, which was statistically insignifican...

Young’s Modulus in Normal Corneas and the Effect on Applanation Tonometry

To determine the statistically normal range of corneal Young's modulus in young healthy eyes in vivo, and to establish if this variation has a clinically significant influence on intraocular pressure (IOP) measurement using applanation tonometry. Central corneal curvature, central corneal thickness (CCT), and applanation IOP (Goldmann tonometer) were measured using standard clinical techniques in one eye of 100 normal human subjects (22.0 +/- 2.9 years) in vivo. The Orssengo-Pye algorithm was used to calculate the corneal Young's modulus of these experimental subjects, and to produce a theoretical model of potential errors in Goldmann applanation tonometry estimates of IOP due to variations of Young's modulus and CCT. Corneal Young's modulus was 0.29 +/- 0.06 MPa [95% confidence interval (CI) 0.17 to 0.40 MPa]. According to the Orssengo-Pye model, the relationship between Young's modulus and the error in applanation IOP is linear; the slope was 23 mm Hg per MPa. An increase from the minimum to the maximum value of the calculated limits of agreement (95% CI) of Young's modulus caused a variation in applanation IOP of 5.35 mm Hg. The anticipated error at the extremes of the limits of agreement (95% CI) of CCT was similar at 4.67 mm Hg. Physiological variations in corneal Young's modulus may cause clinically significant errors in Goldmann applanation tonometry estimates of IOP.

Clinical results of phacoemulsification with the use of Healon5 or Viscoat

Purpose To compare the ophthalmic viscosurgical devices Healon®5 (viscoadaptive) and Viscoat® (dispersive) regarding their overall clinical performance during phacoemulsification and posterior chamber intraocular lens (IOL) implantation as well as their influence on intraocular pressure (IOP). Setting Department of Ophthalmology, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany. Methods In this prospective randomized patient- and observer-masked clinical study, the performance of Healon5 (sodium hyaluronate 2.3%) and Viscoat (sodium hyaluronate 3.0%–chondroitin sulfate 4.0%) was assessed by 3 surgeons during cataract surgery in 90 patients. Surgeons used a 5-point scale for the subjective assessment of the ease of injection, maintenance capacity during continuous curvilinear capsulorhexis, remaining capacity during phacoemulsification, facilitation of IOL implantation, removal from the eye, transparency, and overall performance throughout surgery. Intraocular pressure was measured preoperatively and 24 hours and 7 days postoperatively. Best corrected visual acuity was assessed preoperatively and 7 days postoperatively. Results Overall intraoperative product performance was assessed as good or very good in 34 of 44 patients (77%) in the Healon5 group and in 16 of 46 patients (35%) in the Viscoat group ( P < .001). Retention in the anterior chamber was graded good or very good in 36 patients (82%) in the Healon5 group and in 23 (50%) in the Viscoat group ( P = .001). There were no statistically significant between-group differences in mean IOP preoperatively and 24 hours postoperatively. Conclusions Surgeons graded Healon5 better than Viscoat in overall surgical performance and retention in the anterior chamber during phacoemulsification. These data support that Healon5 adapts to each step during surgery.

Effect of healon5 and 4 other viscoelastic substances on intraocular pressure and endothelium after cataract surgery

Purpose To compare the ophthalmic viscoelastic device (OVD) Healon®5 (sodium hyaluronate 2.3%) with 4 other commonly used OVDs during phacoemulsification and intraocular lens implantation in terms of influence on intraocular pressure (IOP) postoperatively and endothelial cells preoperatively and postoperatively. Setting Department of Ophthalmology, Ruprecht-Karls-University Heidelberg, Germany. Methods This clinical randomized prospective study, in which patients and observer were masked, comprised 81 eyes. Seventy-four eyes (mean patient age 71.2 years ± 7.8 [SD]) completed all preoperative and 5 postoperative examinations. The OVDs used were OcuCoat® and Celoftal® (hydroxypropyl methylcellulose 2.0%), Viscoat® (sodium hyaluronate 3.0%–chondroitin sulfate 4.0%), Healon GV® (sodium hyaluronate 1.4%), and Healon5 (sodium hyaluronate 2.3%). Intraocular pressure was measured by standard Goldmann applanation tonometry preoperatively and 4 to 6 and 24 hours and 7, 30, and 90 days postoperatively. Endothelial cell counts were done preoperatively and 90 days postoperatively using a Pro/Koester WFSCM contact endothelial microscope. Exclusion criteria were IOP greater than 21 mm Hg at the preoperative examination, age younger than 40 years, significant corneal pathology, and a history or presence of uveitis or pseudoexfoliation syndrome. Results All groups had increased IOP 4 hours postoperatively. The Healon5 group had the highest mean pressure (24.9 mm Hg) followed by the Viscoat group (23.6 mm Hg). The mean IOP in the other OVD groups was less than 22.1 mm Hg. These differences were not significant. Twenty-four hours postoperatively and at all subsequent examinations, mean IOP was below 20 mm Hg. The Healon5 group had the lowest mean endothelial cell loss (6.2%), significantly lower than in the other groups ( P < .02). Conclusion With all 5 OVDs, endothelial cell loss was found, with the lowest in the Healon5 group, and IOP was increased 4 to 6 hours postoperatively. After 24 hours, no significant increases in IOP were noted.

Central corneal thickness determined with optical coherence tomography in various types of glaucoma

AIMSTo evaluate central corneal thickness determined by optical coherence tomography (OCT) in various types of glaucoma, and its influence on intraocular pressure (IOP) measurement.METHODSCentral corneal thickness (CCT) was determined by...

The influence of drugs that change blood pressure on intraocular pressure in the anaesthetized rat.

The influence on intraocular pressure (IOP) of various drugs that influence arterial blood pressure was studied in the anaesthetized rat. Both IOP and arterial blood pressure were recorded continuously.