Magnitude Of Intraocular Pressure Research Articles

On refraction shift after trabeculectomy

To determine the factors affecting the shift of refraction after trabeculectomy. The study included 42 patients who were examined prior to trabeculectomy and at the following timepoints: 1 week, 1 month and 3 months after surgery. Examination included tonometry with assessment of corneal biomechanical properties, keratorefractometry with vector analysis, and biometry. The obtained data was processed for regression analysis and to find the possible correlations. All significant correlations between the measured parameters only occur on week 1. Postoperative spherical component of refraction (sphere) correlates negatively both with preoperative axial length (AL) and anterior chamber depth (ACD) (r=-0.699 and r=-0.458, p<0.05) and postoperative AL and ACD (r= -0.767 and r= -0.415, p<0.011). Dependence of sphere on AL is also expressed as a regression model. The magnitude of AL change depends on the magnitude of intraocular pressure (IOP) change (r=0.729, p<0.0001) and correlates negatively with postoperative IOP (r=-0.454, p=0.009) and baseline corneal hysteresis (CH; r= -0.482, p=0.009). Dependence of AL on IOP is also expressed as a regression model. The magnitudes of sphere and cylinder shifts correlate negatively with each other (r=-0.416, p=0.038). Keratometry reveals that the overall cylinder value correlates with the corneal cylinder, and so do the magnitudes of their shifts (r=0.589 and r=0.574, p<0.0001). Dependence of corneal hysteresis on IOP is expressed as a regression model; however, neither tonometric nor biomechanical corneal properties correlate with refraction. Sphere correlates negatively with AL and ACD. In turn, AL is related to the reduction in IOP. This dependence is likely the most important one for the refraction shift after trabeculectomy. No correlations were found for the change of astigmatism.

CLINICAL PROFILE AND DEMOGRAPHIC FEATURES OF PATIENTS WITH JUVENILE ONSET OPEN ANGLE GLAUCOMA

Introduction- Juvenile open angle glaucoma (JOAG) is a rare form of glaucoma that differs from adult-onset primary open angle glaucoma (POAG) in its age of onset and often in the magnitude of IOP(intraocular pressure) elevation. Objective-To document the demographic characteristics, clinical features and treatment outcome of patients diagnosed with JOAG. Materials And Methods- A non-comparative retrospective study of patients diagnosed with JOAG in the eye clinic of a tertiary eye care centre was done. Data was taken from clinical records and it included the basic demographic features and the clinical characteristics of the patients and the outcome of their treatment. Results- 30 patients were reviewed of which 9 (29.97%) patients were aged 20 years and below. The mean age was 26.2+/- 5.0 years. 12 (39.96 %) had a visual acuity of 6/18 in the better eye at the time of presentation. 8 (26.64%) patients defaulted within six months of presentation. The mean IOPfor the 22 patients who were followed up on treatment, was 16.35+/- 5.0 mmHg. Conclusion- In this study, most patients with JOAG presented an advance form of disease. Early detection through school eye health program and community-based screening would help in reducing the scourge arising from JOAG.

The association between corneal hysteresis and surgical outcomes from trabecular meshwork microinvasive glaucoma surgery.

To assess whether an association exists between pretreatment corneal hysteresis (CH) and the magnitude of intraocular pressure (IOP) and medication burden reduction following microinvasive glaucoma surgery (MIGS). Retrospective chart review of 84 eyes from 57 patients with CH measurements who underwent trabecular meshwork MIGS in a glaucoma practice in New York City with follow-up visits at 3-6 and 9-12 months. MIGS included canaloplasty, goniotomy, microbypass stents, or a combination thereof. The lowest and middle CH tertiles experienced significantly reduced mean IOP at 3-6-month follow-ups (p = .007, < .001), whereas the highest tertile did not (p = .06). At 9-12-month follow-ups, a significant mean IOP reduction only persisted in the middle tertile (p = .001). For medication burden reduction, only the highest CH tertile experienced significant mean reductions at both 3-6- and 9-12-month follow-ups (p = .015, .028). Notably, 7 patients in the lowest CH tertile failed MIGS and required an additional surgical or laser procedure within 24 months of MIGS, whereas only 3 patients failed in the other tertiles (likelihood ratio < .05). Multivariate analysis excluding MIGS failures demonstrated an inverse association between CH and the magnitude of post-operative IOP reduction at both 3-6- and 9-12-month follow-ups when controlling for baseline IOP and medication changes (p = .002, .026). There was an inverse association between pretreatment CH and the magnitude of IOP reduction following surgery. There is also evidence of an increased need for repeat surgery or other intervention in patients with lower CH who undergo MIGS.

Long-Term Follow-Up of Normal Tension Glaucoma Patients With TBK1 Gene Mutations in One Large Pedigree

To characterize features of glaucoma associated with a TANK binding kinase 1 (TBK1) gene duplication, which is among the most common molecularly defined causes of normal tension glaucoma (NTG). Retrospective observational case series. We conducted a retrospective case series, by reviewing medical records of 7 members of a pedigree with NTG caused by TBK1 gene duplications. Clinical features of these patients at diagnosis, throughout management, and at latest follow-up were identified, including age, intraocular pressure (IOP), central corneal thickness (CCT), optic nerve head appearance, and mean deviation (MD) assessed with Humphrey visual field (HVF) testing protocols. At initial diagnosis, the mean age was 35 ± 7 years, IOP was 16 ± 2.1mm Hg, cup-to-disc (C/D) ratio was 0.9 ± 0.08, and MD assessed via HVF 30-2 and/or 24-2 testing protocols was-9.0 ± 8.9 (range:-1.8 to-27) dB in the 14 study eyes. At initial diagnosis, 4 of 14 eyes (28%) had no visual field defect, 4 (28%) had early visual field defects, and 6 (43%) had severe visual field defects. Patients had a mean follow-up of 21.5 ± 9.0 years and experienced an average reduction of IOP by 28%. Four of 12 eyes (33%) had stable visual fields throughout follow-up, while 8 eyes (67%) had slow-to-moderate progression. The 30-2 and/or 24-2 HVF tests had an average change in MD of-0.53 ± 0.26 dB/year. No eyes had rapid progression with an MD >1.0 dB/year. At final follow-up, the mean IOP was 11.5 ± 2.9, and C/D ratio was 0.94 ± 0.4. At final follow-up, 3 of 14 eyes (21%) had early visual field defects, 4 (29%) had moderate visual field defects, and 7 (50%) had severe visual field defects. Six of 14 eyes (43%) met criteria for legal blindness. We provide the first report of the clinical features and long-term clinical course in a family of NTG patients with TBK1 gene duplications. TBK1-associated glaucoma exhibits classic features of NTG. Patients present with severe disease at a relatively early age and most (67%) have slow-to-moderate progression of their visual field defects. The rate of visual field change appears correlated with the magnitude of IOP, suggesting that it may be advantageous to set extremely low IOP targets for some patients with TBK1-associated glaucoma.

Pattern Scanning Laser (PASCAL) for Peripheral Iridoplasty in Eyes With Plateau Iris Syndrome: A Novel Application.

The purpose of this study was to evaluate safety and efficacy of pattern scanning laser (PASCAL) for peripheral iridoplasty in eyes with plateau iris syndrome. This study was a retrospective review of cases that underwent PASCAL laser peripheral iridoplasty. Eyes with plateau iris syndrome confirmed on gonioscopy and ultrasound biomicroscopy were included in the study. Primary and secondary outcome measures were angle widening on gonioscopy and magnitude of intraocular pressure (IOP) reduction, respectively. Twelve eyes of 8 patients that completed 1-year follow-up were analyzed. Angle widening was noted in 46% of treated quadrants by at least 1 grade (Shaffer classification) at 1-month follow-up. A statistically significant IOP reduction was noted at 1 year from 20.6±4.8 to 17.8±3.8 mm Hg (P=0.01). At 1 month, 8 of 12 eyes (66.6%) achieved gonioscopic success (widening of the angle by at least 1 grade in 2 of 4 quadrants). At 1 year, 6 of 12 eyes (50%) achieved tonometric success (20% reduction or 3 mm Hg IOP reduction from the baseline without addition of new antiglaucoma medications). No adverse effects associated with PASCAL laser peripheral iridoplasty were observed. PASCAL laser iridoplasty can be a safe and effective alternative to argon laser peripheral iridoplasty in the management of eyes with plateau iris syndrome. Our findings need to be further validated on larger sample size and in different ethnicities.

New insights into blindness; mechanical fatigue of optic nerve head in glaucomatous optic neuropathy

A common cause of blindness worldwide is glaucoma. It is characterized by visual field loss which is caused by optic nerve damage leading to glaucomatous optic neuropathy (GON). Modelling of GON development may be helpful for designing strategies to decelerate the rate of GON progression and prevent GON development at early stages. Attempts to complete the modelling of GON development continue. In this paper, it was speculated that the modelling could be more completed through a biomechanical point of view. GON may result from the mechanical fatigue effects of radial tensile stress (TS), caused by intra-ocular pressure (IOP), on the optic nerve head (ONH). The mechanical fatigue rate is influenced by patient’s age, the maximum and minimum magnitude of IOP, the amplitude of IOP and TS fluctuations, the ONH geometry, scleral thickness and biomechanical properties of the sclera, particularly the peripapillary part, and the axial length of the globe. Based on this model, more efficient strategies can be developed to augment the ONH and decelerate the progression of glaucomatous optic nerve damage, and even screen high-risk individuals at early stages.

Role of Laser Iridoplasty in the Management of Angle Closure Mechanisms other than Pupillary Block.

ABSTRACTPurpose: To investigate the treatment outcomes of argon laser peripheral iridoplasty (ALPI) in angle closure mechanisms other than pupillary block.Methods: We conducted a comprehensive chart review to evaluate consecutive patients who underwent ALPI due to unsuccessful laser iridotomy (whenever the angles remained occludable) between July 2009 and April-2012. An occludable angle was defined as the posterior trabecular meshwork not visible for ≤180° without indentation on dark room gonioscopy. Eyes with previous incisional surgery or more than 90° of peripheral anterior synechiae were excluded. Main data collected were age, presence of glaucoma, pre- and postlaser intraocular pressure (IOP), angle-status, and underlying angle closure mechanism. Main outcomes were post ALPI angle widening on gonioscopy and magnitude of IOP reduction.Results: A total of 41 eyes (27 patients) with persistent occlu-dable angles were initially included in the analysis, comprising approximately 14% of the 196 patients (321 eyes) that had under gone laser iridotomy during the predefined period. Among these cases, most common angle closure mechanisms were plateauiris (56%) and lens-induced component (34%). Patients with plateau iris were mostly women and younger than those with lens-induced component (p ≤ 0.03). A total of 35 eyes (23 patients) underwent ALPI (63% had glaucoma). Mean IOP was significantly reduced from 18. 2 ± 4.7 to 14.6 ± 3.8 (p < 0.01), with no significant difference between patients with plateau iris and lens-induced components (p = 0.22). Over 91% of these eyes showed nonoccludable angles following ALPI (follow-up of 11.8 ± 3.3 months).Conclusion: In this series of middle-aged patients with occlu-dable angles, despite a patent iridotomy, ALPI was a useful procedure independent of the underlying mechanism, leading to angle widening and moderate IOP reduction in most cases.How to cite this article: Prado VG, Dorairaj S, Biteli LG, Sousa AKS, Moreno PAM, Lopes FS, Prata TS. Role of Laser Iridoplasty in the Management of Angle Closure Mechanisms other than Pupillary Block. J Curr Glaucoma Pract 2014;8(2):82-84.

Relationship between the Magnitude of Intraocular Pressure during an Episode of Acute Elevation and Retinal Damage Four Weeks later in Rats

PurposeTo determine relationship between the magnitude of intraocular pressure (IOP) during a fixed-duration episode of acute elevation and the loss of retinal function and structure 4 weeks later in rats.MethodsUnilateral elevation of IOP (105 minutes) was achieved manometrically in adult Brown Norway rats (9 groups; n = 4 to 8 each, 10–100 mm Hg and sham control). Full-field ERGs were recorded simultaneously from treated and control eyes 4 weeks after IOP elevation. Scotopic ERG stimuli were white flashes (−6.04 to 2.72 log cd.s.m−2). Photopic ERGs were recorded (1.22 to 2.72 log cd.s.m−2) after 15 min of light adaptation (150 cd/m2). Relative amplitude (treated/control, %) of ERG components versus IOP was described with a cummulative normal function. Retinal ganglion cell (RGC) layer density was determined post mortem by histology.ResultsAll ERG components failed to recover completely normal amplitudes by 4 weeks after the insult if IOP was 70 mmHg or greater during the episode. There was no ERG recovery at all if IOP was 100 mmHg. Outer retinal (photoreceptor) function demonstrated the least sensitivity to prior acute IOP elevation. ERG components reflecting inner retinal function were correlated with post mortem RGC layer density.ConclusionsRetinal function recovers after IOP normalization, such that it requires a level of acute IOP elevation approximately 10 mmHg higher to cause a pattern of permanent dysfunction similar to that observed during the acute event. There is a ‘threshold’ for permanent retinal functional loss in the rat at an IOP between 60 and 70 mmHg if sustained for 105 minutes or more.

Using the electroretinogram to understand how intraocular pressure elevation affects the rat retina.

Intraocular pressure (IOP) elevation is a key risk factor for glaucoma. Our understanding of the effect that IOP elevation has on the eye has been greatly enhanced by the application of the electroretinogram (ERG). In this paper, we describe how the ERG in the rodent eye is affected by changes in IOP magnitude, duration, and number of spikes. We consider how the variables of blood pressure and age can modify the effect of IOP elevation on the ERG. Finally, we contrast the effects that acute and chronic IOP elevation can have on the rodent ERG.

Intraocular pressure magnitude and variability as predictors of rates of structural change in non-human primate experimental glaucoma

The purpose of this study is to determine the effects of intraocular pressure (IOP) mean, maximum and variability on the rate of structural change in experimental glaucoma. Data were taken retrospectively from 59 non-human primates involved in ongoing studies of experimental glaucoma. IOP was measured by tonometry every 1–3 weeks, and these readings split into non-overlapping fixed-length windows. First, different characterizations of IOP variability were tested to find the one that was least correlated with the mean IOP within the same window. Next, the rates of change of the Mean Position of the Disc (MPD) from confocal scanning laser tomography, and Retinal Nerve Fiber Layer Thickness (RNFLT) from spectral domain ocular coherence tomography, were calculated over each window. Mixed effects models were formed to predict these rates based on the characterizations of IOP. Normalized root mean squared residual (RMSR) from the trend of IOP during windows of five IOP measurements provided a characterization of variability showing lowest correlation with mean IOP (r < 0.001). In univariate analyses, rate of change of MPD and RNFLT were predicted by mean IOP (p < 0.001 for both) and maximum IOP (p < 0.001 for both). IOP variability did not significantly predict change in MPD (p = 0.129) or RNFLT (p = 0.438). In bivariate models, maximum IOP was the most significant predictor of change. We conclude that normalized RMSR allows the effects of IOP variability to be assessed independently of mean IOP. Maximum IOP provided the best predictability of structural change, either causally or because it captures the contributions of both mean and variability.

Effect on Diurnal Intraocular Pressure Variation of Eliminating the α-2 Adrenergic Receptor Subtypes in the Mouse

To investigate the effect on circadian variation of intraocular pressure (IOP) of eliminating the alpha2A-, alpha2B-, or the alpha2C-adrenergic receptor subtypes in the mouse. A microneedle method was used to measure IOP in knockout mice lacking the alpha2A-, alpha2B-, or the alpha2C-receptor (alpha2A-R(-/-), alpha2B-R(-/-), alpha2C-R(-/-)), in wild-type mice of the alpha2B knockout strain (alpha2B-R(+/+)), and in the background strain mice, C57BL/6. All mice were maintained in a 12-hour light-dark cycle commencing at 0600 hours. IOP was measured at 0900 and 2100 hours in the five groups: C57BL/6 (n = 8), alpha2A-R(-/-) (n = 10), alpha2B-R(-/-) (n = 8), alpha2B-R(+/+) (n = 8), and alpha2C-R(-/-) (n = 10). In parallel experiments, eyes from the alpha2A-R(-/-), alpha2B-R(-/-), alpha2C-R(-/-), and C57BL/6 mice were embedded in epoxy resin, and semithin sections were stained with toluidine blue. IOP at 0900 hours in B6, alpha2A-R(-/-), alpha2B-R(-/-), alpha2B-R(+/+), and alpha2C-R(-/-) mice was 17.1 +/- 1.8, 17.7 +/- 1.4, 17.1 +/- 2.1, 17.6 +/- 1.3, and 17.3 +/- 0.9 mm Hg, respectively (mean +/- SD). IOP at 2100 hours in the same eyes was 19.6 +/- 1.9, 19.2 +/- 2.2, 20.5 +/- 1.5, 19.7 +/- 0.8, and 21.3 +/- 2.7 mm Hg, respectively. There was no significant difference among these genotypes in IOP measured at either time point (P > 0.05, ANOVA). Within each genotype, IOP at 2100 hours was significantly higher than IOP at 0900 hours (C57BL/6, alpha2B-R(-/-), alpha2B-R(+/+), and alpha2C-R(-/-): P < 0.01; alpha2A-R(-/-): P < 0.05, paired t-test). Differences in the diurnal IOP change among the different genotypes were insignificant (P > 0.05, ANOVA). Histopathologic assessment found minimal differences in the structural organization of the anterior segment among the alpha2A-R(-/-), alpha2B-R(-/-),alpha2C-R(-/-), or C57BL/6 mice. These results indicate that IOP magnitude and circadian variation are minimally altered by the absence of the alpha2A-, alpha2B-, or alpha2C-receptor subtypes in transgenic mice.

The Effect of Paclitaxel Powder on Glaucoma Filtration Surgery in Rabbits

The authors determine if the intraoperative placement of paclitaxel powder in the subconjunctival space improves the outcome of glaucoma filtration surgery in rabbits. A posterior lip sclerectomy was performed in the right eye of 24 New Zealand white rabbits. Before the conjunctiva was fully sutured, 8 mg of mannitol powder alone, or 8 mg of mannitol powder containing either 10 micrograms or 250 micrograms of paclitaxel, was placed in the subconjunctival space of six eyes each in masked fashion. An additional six animals were treated with episcleral application of a sponge soaked in a solution of 0.5 mg/ml of mitomycin C (MMC) for 5 minutes before the sclerectomy was performed. Intraocular pressure and bleb size were measured until the operation had failed or until the 7 weeks of observation had concluded. Both paclitaxel powder and MMC solution improved the outcome of filtration surgery in this model as measured by magnitude of intraocular pressure (IOP) lowering and duration of surgical success. No toxic effect of either drug was observed, although endophthalmitis was observed in eight animals followed for more than 3 weeks. The introduction of paclitaxel into the subconjunctival space at the conclusion of filtration surgery has an effect comparable to intraoperative MMC.

Magnitude of decrease in intraocular pressure depends upon intensity of exercise.

The present study was planned to investigate the relationship between the magnitude of intraocular pressure (IOP) reduction after short-duration exercise and the intensity, duration and quantity of exercise in healthy subjects. Twenty-five healthy, sedentary male of the same age group, performed exercises at the levels of 80%, 60%, and 40% maximum heart rate (HRmax) for 15 minutes, 80% HRmax for 7.5 minutes, 60% HRmax for 10 minutes, and 40% HRmax for 30 minutes. IOP was measured with the Goldmann applanation tonometer. The IOP reduction at 5 minutes after 15 minutes of exercising at 80% HRmax, 60% HRmax, and 40% HRmax were 4.7 +/- 0.9, 3.5 +/- 0.7, and 0.9 +/- 0.4 mmHg, respectively. At five minutes, after exercising 7.5 minutes at 80% HRmax, 10 minutes at 60% HRmax, and 30 minutes at 40% HRmax, IOP reduced by 4.5 +/- 0.7, 3.3 +/- 0.9, and 2.9 +/- 1.1 mmHg, respectively. This study concludes that intensity of exercise seems responsible for the magnitude of the initial IOP decrease after short-term exercise. Furthermore, it seems that other factors such as duration of exercise or quantity of exercise, blood pressures, body mass index are not related to the amount of the initial fall in IOP.