Psychophysical and electrophysiological testing in ocular hypertension

Pattern Electroretinogram in Ocular Hypertension, Glaucoma Suspect and Early Manifest Glaucoma Eyes: A Systematic Review and Meta-analysis

Topic

To provide standardized confidence limits of the transient pattern electroretinogram (tPERG) P50 and N95 and steady state pattern electroretinogram (ssPERG) amplitudes in normal controls as compared to ocular hypertension (OHT), glaucoma suspect (GS), or early manifest glaucoma (EMG) eyes.

Clinical Relevance

The identification of standardized confidence limits in the context of pattern electroretinogram (PERG) might overcome the high intrinsic variability of the measure, and it might lead to a more intuitive understanding of the results as well as to an easier comparison of data from multiple tests, sites, and operators.

Methods

The study protocol was prospectively registered on the International Prospective Register of Systematic Reviews (ID: CRD42022370032). A literature search was conducted on PubMed, Web of Science, and Scopus. Studies comparing PERG raw data in normal control eyes as compared to OHT, GS, or EMG were included. The risk of bias was assessed using the National Institute for Health and Clinical Excellence quality assessment tool. The main outcome was the P50, N95, and ssPERG amplitude difference between the control and the study groups' eyes. The standardized mean difference was calculated as a measure of the effect size for the primary outcome. A subanalysis was conducted based on the type of electrodes adopted for the PERG measurements (invasive vs. noninvasive).

Results

Of the 4580 eligible papers, only 23 were included (1754 eyes). Statistically significant amplitude differences were found in the P50, N95, and ssPERG amplitudes between normal controls and OHT, GS, and EMG eyes. The highest standardized mean difference values were observed in the ssPERG amplitude in all 3 sets of comparison. The subanalysis did not reveal any statistically significant differences between invasive and noninvasive recording strategies.

Conclusions

The use of standardized values as the main outcome measures in the context of the PERG data analysis is a valid approach, normalizing several confounding factors which have affected the clinical utility of PERG both for individual patients and in clinical trials. Steady state PERG apparently better discriminates diseased eyes compared to tPERG. The adoption of skin-active electrodes is able to adequately discriminate between healthy and diseased statuses.

Financial Disclosures

Proprietary or commercial disclosure may be found after the references.

Rehabilitative strategies after filtering procedure in glaucoma

Glaucoma is one of the leading causes of non-reversible blindness worldwide, and almost 6 million people are estimated to be impaired visually in advanced stage of glaucoma. Recently, several studies on glaucoma has been focused towards new therapeutic approaches based on mechanisms independent from IOP control. Effects of new therapeutic agents, visual psychophysical training, or complementary medications targeting optic pathways today seem to be a relevant and effervescent field of research. The goal of the study is to evaluate in glaucoma patients if a rehabilitative strategy with a biofeedback training with microperimetry may be useful after surgery in recovery visual performance even when visual field defects are present in IOP is well controlled environment. Were enrolled 24 patients (28 eyes) with Primary Open Angle Glaucoma (POAG) (mean 63 range: 49–75 years) from our Glaucoma Center after filtering surgery. All patients after one months from surgical intervention underwent to a complete ophthalmologic examination: IOP measurement, gonioscopy, visual field and SD-OCT at baseline of RNFL thickness. In some cases, were included in the study both eyes because in POAG frequently clinical conditions are different in each eye, and secondarily new fixation target retinal location (TRL) was chosen based on single eye retinal sensitivity. Best corrected visual acuity was significantly increased after the training from 0.61 to 0.479 (p = 0.00058) with no change in refractive error. After the biofeedback patients presented increased value in Mean retinal sensitivity from 14.91 to 15.96 (p = 0.0078).Fixation stabilitywas improved either according to Fuji classification (increased from 75.1 to 81.3% p = 0.0073) or BCEA value, reduced from 8.7 to 6.0 square degrees (p = 0.013) we noted a marked increase in this parameter with better performances and satisfaction by the patient. RFNL thickness: no change was noted (p = 0.505) in this value as an indicator of disease’s stability. Our data indicate that MP-3 Biofeedback may be a good strategy to reduce the impairment of the Glaucoma Patient.

Neurofibromatosis Type 1: Ocular Electrophysiological and Perimetric Anomalies

INTRODUCTION

Neurofibromatosis type 1 (NF1) is a multisystemic disease caused by the mutation of Nf1 gene located on chromosome 17q11.2. The mutation determines the loss of function of the protein neurofibromin with consequent uncontrolled cellular proliferation. Patients are characterized by a wide range of dermatological, neurological, and ophthalmological symptoms.

PURPOSE

The aim of the study was to evaluate, through pattern visual evoked potentials (p-VEPs) and frequency doubling technology (FDT) Matrix perimetry, the objective and psychophysical functionality of the optic pathways in a group of NF1 patient.

METHODS

The study group consisted of 26 patients affected by NF1 and 17 healthy controls. Each patient underwent a complete ophthalmological examination, p-VEPs with the evaluation of amplitude and latency of the P100 wave, and FDT perimetry, with the evaluation of central sensitivity (CS), mean deviation (MD), pattern standard deviation (PSD) and glaucoma hemifield test (GHT).

RESULTS

NF1 patients showed a statistically significant alteration in the transmission of visual impulse. P-VEPs results highlighted a reduced amplitude and an increased latency of the P100 wave, suggesting an involvement of the visual pathway. Visual field analysis showed a significant reduction in all the observed parameters as well (CS, MD, PSD, and GHT).

CONCLUSION

The present study showed, in NF1 patients, a qualitative and quantitative alteration in the conduction of stimuli through the visual pathways. The observed alterations are present, although, only at a subclinical level. None of the patients included in the study showed any manifest visual deficit nor had any concomitant pathology that might have affected the outcome of the study. In conclusion, electrophysiological exams and computer perimetry may take part, alongside a wider array of exams, in the differential diagnosis and later monitoring of NF1.

Neuroprotection in glaucoma-electrophysiology

Hypertensive glaucoma is defined as a group of diseases with progressive loss of the neuroretinal margin of the optic disc that causes characteristic degenerative optic neuropathy. The present study provided an updated summary of the physiology and pathology of neurotransmission in the visual path, with the focus on glaucoma. The results of positron emission tomography, functional magnetic resonance imaging and mainly electrophysiological methods demonstrated pathogenesis of nerve cell damage in the visual pathway. Based on these conclusions, neuroprotection in glaucoma was proposed. This consists mainly of the reduction of the intraocular pressure. It is followed by a decrease of glutamate in the synaptic cleft and blockade of its binding to the NMDA receptors. The supply of energy substrates to altered nerve cells is also indispensable. Therapy should be systemic due to impairment of the complete visual path.

Bilateral asymmetry improved accuracy when assessing glaucomatous vision-related quality of life impairment

Bilateral asymmetry has been used in optical coherence tomography tests to find early damage to the optic nerve. However, limited studies have quantitatively evaluated bilateral asymmetry in electrophysiological disorders in patients with glaucoma. The aim of the study was to evaluate bilateral asymmetry in pattern visual evoked potentials (PVEPs) and conventional clinical markers as well as its potential use in detecting glaucomatous impairment. After investigating 60 glaucomatous patients (120 eyes) and 65 age and sex-matched normal control subjects (130 eyes) using uni- and multivariable analysis, we found that vision-related quality of life (VRQOL) impairment was significantly associated with larger bilateral asymmetry index (BAI) of clinical markers. Rasch-calibrated National Eye Institute Visual Function Questionnaire-25 scores were significantly associated with the BAI in PVEPs latency in 15 minutes check size (β = -0.478, 95% confidence interval [CI], -0.708 to -0.248, P < .001) and the BAI in visual field mean deviation (β = -0.249, 95% CI, -0.454 to -0.044, P = .018) according to multivariable analysis. Bilateral asymmetry in objective and subjective functional measurements was quantitatively associated with glaucomatous VRQOL impairment. This finding may help bridge the gap in understanding between patients and clinicians, and increase awareness of how glaucomatous neuropathic progression may interfere with patients' daily life.

Normal tension vs high tension glaucoma: an - overview

The study provides an up-to-date overview of pathogenesis, functional and structural changes in normal tension glaucoma (NTG) and its differences from high tension glaucomas (HTG). The authors point to less known facts which make both diagnostic groups different. First of all, there are electrophysiological findings that verify pathology in the complete visual pathway in HTG in contrast to NTG where the retinal ganglion cell response is relatively normal but the abnormalities are in the visual pathway. This corresponds to the findings of functional magnetic resonance imaging of the brain with a significant decrease in activity in HTG compared to NTG. We found a higher decrease in activity in HTG following application of the colour paradigm compared to NTG where we did not see a similar difference. We also investigated the central corneal thickness (CCT) in both diagnostic groups. We did not find a statistically significant difference. However, we found the effect of CCT on progression of the changes in visual fields in HTG. In relation to suspicion of abnormally low cerebrospinal pressure and a possible cerebrovascular fluid flow disturbance in NTG, we examined the optic nerve thickness (OND) and optic nerve sheath diameter (OSD) at a distance of 4, 8, 16 and 20mm from the posterior pole of the eye. In the comparison with the healthy population, we did not find any abnormalities except for the width of the optic chiasma that was markedly lower in NTG. In relation to a possible impairment of cerebral perfusion we determined the degrees of cerebral atrophy using magnetic resonance imaging by measuring the bicaudate ratio (BCR) and white matter lesions using the Fazekas scale. We did not find a difference between HTG and NTG in BCR. We found statistically significant changes in BCR which correlated with the changes in visual fields. The higher values of the pattern defect were associated with increased brain atrophy (BCR). We did not detect similar relations in the Fazekas scale. We found a significant difference in this parameter among NTG, HTG and a control group. We found the most advanced changes in the patients with HTG. Conclusion: In HTG, impairment of retinal ganglion cells and subsequently also their axons, including visual cortex occurs because of a high intraocular pressure. In NTG, the retinal ganglion cells are relatively normal like the visual cortex, but alteration occurs in their axons. The cause is not a high intraocular pressure but most probably ischemia.

Normotensive glaucoma

This article provides an updated overview of the structural and functional changes in normotensive glaucoma and its variations from hypertensive glaucoma. The authors point out the less familiar facts in which both diagnostic groups differ.

Pattern Electroretinography and Visual Evoked Potentials Provide Clinical Evidence of CNS Modulation of High- and Low-Contrast VEP Latency in Glaucoma

Purpose

Both pattern electroretinography (PERG) and visual evoked potentials (VEP) can be performed using low- (15%; Lc) and high- (85%; Hc) contrast gratings that may preferentially stimulate the magno- and parvocellular pathways. We observed that among glaucomatous patients showing only one VEP latency deficit per eye, there appeared to be a very strong tendency for an Hc delay in one eye and an Lc delay in the other.

Methods

Diopsys NOVA-LX system was used to measure VEP Hc and Lc latency among a clinical glaucoma population to find all individuals with either a single Hc or Lc latency abnormality in each eye (group 1), or with greater than 0 and less than 4 Hc or Lc VEP latency abnormalities in the two eyes (group 2) to determine whether a significant inverse correlation existed for these values in either group. Hc and Lc PERG data were also evaluated to assess associated retinal ganglion cell responses.

Results

A strong inverse correlation (P = 0.0000003) was observed between the Hc and Lc VEP latency values among the 64 eyes in group 1. Group 2 provided a comparable result (n = 143; 286 eyes; P = 0.0005). PERG (n = 81; 162 eyes) also showed strong bilateral symmetry for magnitude values (P < 0.0001 for both Lc and Hc in groups 1 and 2).

Conclusions

Bilateral retention of both low-resolution/high-speed and high-resolution/low-speed function may persist with both eyes open despite symmetrically pathologic retinal ganglion cell PERG waveform asynchrony for Hc and Lc stimuli in the paired eyes.

Translational Relevance

Clinical electrophysiology strongly suggests binocular compensation for dynamic dysfunction operates under central nervous system (CNS) control in glaucoma.

Modulatory effects of 1,25-dihydroxyvitamin D3 on eye disorders: A critical review

Many studies have shown that the presence of 1,25-dihydroxyvitamin D3 in the eye is able to modulate inflammatory responses. In fact, it has been demonstrated that topical administration of vitamin D3 inhibits Langerhans cells migration from the central cornea, corneal neovascularization, and production of cytokines (i.e., interleukin-1-6-8) in experimental animals. Moreover, both in vitro and in vivo studies have demonstrated that vitamin D is a potent inhibitor of retinal neovascularization. It has been shown that calcitriol, the biologically active form of vitamin D, inhibits angiogenesis both in cultured endothelial cells and in retinas from guinea pigs with retinoblastoma or oxygen-induced ischemic retinopathy. In addition, it seems that this compound is able to prevent the progression from early to neovascular age-related macular degeneration (AMD) and, at the same time, to down-regulate the characteristic inflammatory cascade at the retinal pigment epithelium-choroid interface due to its anti-inflammatory and immunomodulatory capabilities. Furthermore, 1,25-dihydroxyvitamin D3 and its analogue, 2-methylene-19-nor-1,25-dihydroxyvitamin D3, are able to modulate intraocular pressure (IOP) through gene expression. Several studies have suggested a role in glaucoma and diabetic retinopathy therapies for vitamin D3. In conclusion, this review summarizes our current knowledge on the potential use of vitamin D3 in the protection and treatment of ocular diseases in ophthalmology.

Nd: Yag laser iridotomy in Shaffer-Etienne grade 1 and 2: angle widening in our case studies

AIM

To obtain widening of a potentially occludable angle, in according to Kanski's indications, through preventive Nd:Yag laser iridotomy. The observational study was performed by using gonioscopy for the selection and follow-up of 1165 treated eyes and exploiting Shaffer-Etienne gonioscopic classification as a quality/quantity test of the angle recession.

METHODS

Between September 2000 and July 2012, 586 patients were selected at the Outpatients' Ophthalmological Clinic of the Policlinico Umberto I of Rome in order to undergo Nd: Yag laser iridotomy. A Goldmann type contact lens, Q-switched mode, 2-3 defocus, and 7-9 mJ intensity with 2-3 impulse discharges were used for surgery.

RESULTS

From as early as the first week, a whole 360° angle widening were evident in the patients, thus showing the success of Nd:Yag laser iridotomy in solving relative pupil block. The angle remained narrow by 270° in 14 eyes only, despite repetitions of further treatment with laser iridotomy in a different part of the iris, twice in 10 eyes and three times in 4 eyes.

CONCLUSION

Nd:Yag laser iridotomy revealed itself as being a safe and effective treatment in widening those critical Shaffer-Etienne grade 1 and 2 potentially occludable angles.

Photopic negative response in diagnosis of glaucoma: an experimental study in glaucomatous rabbit model

AIM

To determine whether the photopic negative response (PhNR) elicited by transient white flash on white background is characterizing for glaucoma model in rabbits.

METHODS

Glaucoma was induced in twelve rabbits by subconjunctival injection of 0.05 mL of betamethasone in right eyes (each 1 mL contain betamethasone dipropionate 5 mg and betamethasone sodium phosphate 2 mg).The intraocular pressure (IOP), electroretinogram (ERG) and visual evoked potential (VEP) were measured successively prior and on the 3, 7d, two weeks and four weeks postglaucoma induction. After four weeks, the animals were sacrificed and the globes were histopathologically examined.

RESULTS

The IOP increased significantly after one week (P=0.0001), then it gradually returned to the control level. In ERG examination, the means of a and b wave amplitude and latency were not affected significantly. PhNR amplitude decreased significantly within one week (P=0.0001), but its latency was not affected significantly (P=0.132). The means of VEP latency and amplitude were significantly affected after two weeks and four weeks of glaucoma induction (P=0.0001 and 0.02, respectively). The histopathologic examination of the globes showed reduced number of cells in the retinal ganglion cell layer with multiple vacuoles in the retinal nerve fibre layer.There was significant positive correlation between ganglion cell layer cells and PhNR amplitude (r=0.8, P=0.002).

CONCLUSION

The rise in IOP resulted in irreversible changes or incomplete recovery of VEP and PhNR amplitude. Both PhNR and VEP represented good additional tools in early diagnosis of glaucoma.

New trends in visual rehabilitation with MP-1 microperimeter biofeedback: optic neural dysfunction

The aim of this study was to evaluate the efficacy of visual rehabilitation with MP-1 microperimeter biofeedback in advanced optic neural dysfunction due to glaucoma, and to precisely characterize fixation stability and location in affected patients. Ten patients (18 eyes) with advanced glaucoma were submitted to a rehabilitation protocol that consisted of: a 25-item questionnaire (National Eye Institute Visual Functioning Que stionnaire); measurement of visual acuity; a reading speed test; microperimetry with fixation study, retinal sensitivity and the bivariate contour ellipse area (BCEA). The rehabilitation program consisted of 10 training sessions of 10 minutes per eye performed over a period of one week and was repeated at four months, eight months, and one year. Statistical analysis was performed using the Student's t-test and Spearman correlation; p values less than 0.05 were considered statistically significant. In 13 eyes fixation changed from unstable to relatively unstable while its location changed from predominantly eccentric to predominantly central. In five eyes, fixation changed from relatively unstable to stable with a change of location from poor central fixation to predominantly New trends in visual rehabilitation with MP-1 microperimeter biofeedback: optic neural dysfunction central fixation. Mean retinal sensitivity changed from 7.43±8.28 dB to 8.33±9.04 dB (p<0.05); the mean best corrected visual acuity was 0.98±0.66 logMAR at the baseline assessment, and 0.75±0.6 logMAR at the end of rehabilitation (p>0.05); reading speed improved from a mean value of 31.4±4.3 words/minute to 55.6±3.2 words/minute at the end of the training (p<0.05). The BCEA changed from 0.94±0.39 deg2 to 0.86±0.46 deg2 (p=0.76). Rehabilitation with MP-1 biofeedback in patients with advanced glaucoma is a useful means of improving these patients' fixation stability, reading speed and quality of life.

Cystic fibrosis and new trends by ophthalmological evaluation: a pilot study

Background. Cystic fibrosis (CF) is characterized by hypoxia that affects several organic tissues. Retinal ganglion cells may suffer from the hypoxic status, and this may lead to alterations of retinal nerve fiber. Methods. Twenty-two eyes in CF patients were analyzed. A complete ocular evaluation and visual field exams of the 30 central degrees were performed using the frequency doubling technology (FDT). Forced expiratory volume in one second (FEV1%), forced vital capacity (FVC%), oxyhaemoglobin saturation (SpO₂%), and hematocrit (Ht%) have been calculated. FDT analyzed parameters were mean deviation (MD) and pattern standard deviation (PSD). Pearson's correlation was chosen as statistical analysis. Results. Data showed statistically significant relationship between MD and Ht% (r value −0.18; P = 0.04), MD and FEV1% (r value −0.68; P = 0.001), and MD and FVC% (r value −0.45; P = 0.005). Moreover, there were correlations between PSD and Ht% (r value 0.29; P = 0.03), PSD and SpO₂% (r value −0.31; P = 0.01), PSD and FEV1% (r value 0.71; P = 0.0005), and PSD and FVC% (r value 0.63; P = 0.003). Conclusions. The oxygen supply alterations might determine hypoxia of the ganglion cells causing a decrease of receptive optic nerve fiber activity. This method could be also useful to evaluate indirectly pulmonary activity of the CF disease.

Hypobaric hypoxia: effects on intraocular pressure and corneal thickness

Objective. The purpose of this study focused on understanding the mechanisms underlying ocular hydrodynamics and the changes which occur in the eyes of subjects exposed to hypobaric hypoxia (HH) to permit the achievement of more detailed knowledge in glaucomatous disease. Methods. Twenty male subjects, aged 32 ± 5 years, attending the Italian Air Force, were enrolled for this study. The research derived from hypobaric chamber, using helmet and mask supplied to jet pilotes connected to oxygen cylinder and equipped with a preset automatic mixer. Results. The baseline values of intraocular pressure (IOP), recorded at T1, showed a mean of 16 ± 2.23 mmHg, while climbing up to 18,000 feet the mean value was 13.7 ± 4.17 mmHg, recorded at T2. The last assessment was performed returning to sea level (T4) where the mean IOP value was 12.8 ± 2.57 mmHg, with a significant change (P < 0.05) compared to T1. Pachymetry values related to corneal thickness in conditions of hypobarism revealed a statistically significant increase (P < 0.05). Conclusions. The data collected in this research seem to confirm the increasing outflow of aqueous humor (AH) in the trabecular meshwork (TM) under conditions of HH.

Multifocal and pattern-reversal visual evoked potentials vs. automated perimetry frequency-doubling technology matrix in optic neuritis

Background:

To compare the usefulness of the traditional pattern-reversal Visual Evoked Potentials (VEP) with multifocal VEP (mfVEP) and Frequency-Doubling Technology (FDT) perimetry in the evaluation of the ocular abnormalities induced by acute or subacute optic neuritis (ON).

Materials and Methods:

The test results of 24 ON patients were compared with those obtained in 40 normal control subjects. MfVEP recordings were obtained by using an Optoelectronic Stimulator that extracts topographic VEP using a pseudorandom m-sequence stimulus. Receiver operator characteristic (ROC) curves were calculated to determine the sensitivity and specificity of abnormal values.

Results:

The frequency of the abnormal ocular findings differed in the ON patients according to the used technique. Reduced visual sensitivity was demonstrated in 12 eyes (54.5%) using FDT perimetry; 17 eyes (77.2%) showed decreased amplitude and/or an increase in the implicit time of the P1 wave in mfVEP and 20 eyes (90.9%) showed an abnormal decrease in the amplitude and/or an increase in the latency of the P100 peak at VEP examination. The areas under the ROC curves ranged from 0.743 to 0.935, with VEP having the largest areas. The VEP and mfVEP amplitudes and latencies yielded the greatest sensitivity and specificity.

Conclusions:

The mfVEP and the FDT perimetry can be used for the evaluation and monitoring of visual impairment in patients with ON. The most sensitive and practical diagnostic tool in patients with ON is, however, the traditional VEP. The mfVEP can be utilized in those cases with doubtful or negative VEP results.

Flash electroretinography and pattern visual evoked potential changes in ocular hypertension patients

Purpose. To evaluate the changes of flash electroretinography (fERG) and pattern visual evoked potentials (pVEP) in ocular hypertension (OHT) patients. Methods. Twenty-five OHT patients and 30 healthy volunteers were enrolled for this cross-sectional study. Opthalmologic examinations, visual field tests, pVEP and fERG were performed. The main outcome measures were the differences between pVEP and fERG parameters. Results. The mean age of OHT patients and volunteers were 57 ± 12.25 years (range 30-65 years), and 53.25 ± 12.0 years (range 30-65 years), respectively. The mean amplitude of the pVEP was statistically lower in the OHT group (P < 0.05). Latency of the two groups was different; however, the difference was not statistically significant (P > 0.05). In fERG of OHT group, there was a significant decrease in the amplitude of the oscillatory potentials (Ops), and a significant delay in latency of rod and cone waves (all P < 0.05). There was no significant change in the flicker fERG waves between the two groups (P > 0.05). Conclusions. Although we found a decrease in Ops amplitude and a prolonged latency in flicker fERG, only the decrease in Ops amplitude was statistically significant between the two groups. The amplitude of Ops wave and amplitude of pVEP may reflect early glaucomatous damage in OHT patients.

Fixed topical combinations in glaucomatous patients and ocular discomfort

OBJECTIVE

The purpose of this study was to verify the ocular comfort of a fixed topical combination of brinzolamide 1% plus timolol 0.5% suspension vs. dorzolamide 2% plus timolol 0.5% solution, both preserved with benzalkonium chloride (BAK), in patients with primary open-angle glaucoma (POAG) through subjective and objective methods. BAK is the most commonly used preservative in topical glaucoma medications.

METHODS

62 subjects were examined and included in the analysis. Each patient was asked to complete a questionnaire on symptoms (Ocular Surface Disease Index) and then underwent a series of examinations. The Ocular Protection Index evaluated the risk of damage to the ocular surface, and was expressed as the ratio between fluorescein breakup time and blinking interval. These and other analyses were repeated 30 days after instillation of the new eye drop treatment.

RESULTS

The results demonstrated that patients enrolled with the preserved fixed combination of dorzolamide or brinzolamide represented a subgroup of patients in which the discomfort symptoms were supposedly justified by the presence of BAK used chronically in antihypertensive drops. Ocular discomfort scores were significantly higher with dorzolamide/timolol than brinzolamide/timolol (p < 0.0001).

CONCLUSIONS

This work shows the better tolerability of brinzolamide 1% plus timolol 0.5% suspension, compared with dorzolamide 2% plus timolol 0.5% solution. Fortunately, some of the adverse reactions induced by preserved eye drop glaucoma medication are reversible after removing the preservatives. Both the potential for added benefit and patient compliance should be considered when selecting ocular hypotensive therapy.

Palmitoylethanolamide effects on intraocular pressure after Nd:YAG laser iridotomy: an experimental clinical study

PURPOSE

The purpose of this article was to evaluate whether the anti-inflammatory agent palmitoylethanolamide (PEA) can counteract the increase of intraocular pressure (IOP) that may occur after neodymium-doped: yttrium aluminum garnet (Nd:YAG) laser iridotomy.

METHODS

Fifteen patients underwent bilateral laser iridotomy (Visulas YAG III Laser; Zeiss) for the prevention of primary closed-angle glaucoma. The IOP was measured at the beginning of the study (t-1), after 15 days of pretreatment with placebo or PEA (t0), and at 15, 30, and 120 min after the iridotomy (t1, t2, t3). The pretreatment consisted of 2 tablets of placebo or PEA per day for 15 days.

RESULTS

The t-test did not show a significant difference between the preoperative mean values of IOP t-1 and t0 in both the pretreatments. Analysis of variance/Tukey's test pointed out a significant increase of the postoperative IOP values in placebo pretreated patients (P≤0.05), but not in those who were pretreated with PEA. The trend analysis confirmed the significant positive trend in placebo pretreatment. The parallelism test between the 2 regressions showed a significant difference for the slopes (P=0.022) and not for the intercepts (P=0.520).

CONCLUSIONS

PEA can counteract the increase of IOP that occurs after iridotomy. It is likely that PEA controls the inflammatory process after iridotomy.