Unilateral Intraocular Pressure Research Articles

Acute ocular hypertension in the living human eye: Model description and initial cellular responses to elevated intraocular pressure

This initial methods study presents the initial immunohistochemical and transcriptomic changes in the optic nerve head and retina from three research-consented brain-dead organ donors following prolonged and transient intraocular pressure (IOP) elevation. In this initial study, research-consented brain-dead organ donors were exposed to unilateral elevation of IOP for 7.5 h (Donor 1), 30 h (Donor 2), and 1 h (Donor 3) prior to organ procurement. Optic nerve tissue and retinal tissue was obtained following organ procurement for immunohistological and transcriptomic analysis.Optic nerve sections in Donor 1 exposed to 7.5-hours of unilateral sub-ischemic IOP elevation demonstrated higher levels of protein expression of the astrocytic marker, glial fibrillary acidic protein (GFAP), within the lamina cribrosa with greatest expression inferior temporally in the treated eye compared to control. Spatial transcriptomic analysis performed on optic nerve head tissues from Donor 2 exposed to 30 h of unilateral IOP elevation demonstrated differential transcription of mRNA across laminar and scleral regions. Immunohistochemistry of retinal sections from Donor 2 exhibited higher GFAP and IBA1 expression in the treated eye compared with control, but this was not observed in Donor 3, which was exposed to only 1-hour of IOP elevation. While there were no differences in GFAP protein expression in the retina following the 1-hour IOP elevation in Donor 3, there were higher levels of transcription of GFAP in the inner nuclear layer, and CD44 in the retinal ganglion cell layer, indicative of astrocytic and Müller glial reactivity as well as an early inflammatory response, respectively.We found that transcriptomic differences can be observed across treated and control eyes following unilateral elevation of IOP in brain dead organ donors. The continued development of this model affords the unique opportunity to define the acute mechanotranscriptomic response of the optic nerve head, evaluate the injury and repair mechanisms in the retina in response to IOP elevation, and enable correlation of in vivo imaging and functional testing with ex vivo cellular responses for the first time in the living human eye.

Short-Term Effect of Micropulse Transscleral Laser Therapy on Intraocular Pressure in Untreated Fellow Eyes of Glaucoma Patients: Preliminary Results.

It has been observed that an intraocular pressure (IOP) altering intervention in one eye is followed by a consensual response in the untreated fellow eye. The underlying mechanisms remain unclear. Involvement of neuronal, cytokine, and hormonal regulation of aqueous humor dynamics, as well as improved treatment adherence or systemic absorption of topically administered medical compounds, have been suggested. Our aim was to investigate the short-term effects of unilateral micropulse transscleral laser therapy on IOP in the fellow eye. All medical records of glaucoma patients who underwent micropulse transscleral laser therapy in a tertiary referral center between May 2019 and February 2023 were collected and analyzed. We found a significant reduction in IOP in the treated eyes, indicating successful treatment. In the fellow eyes, despite not having changed any of the pharmacological IOP-reducing therapies, a significant reduction in IOP from 17.0 ± 5.1 mmHg to 13.5 ± 4.4 mmHg (p < 0.01) was observed. This reduction was, however, short-term and reached statistical significance on the first postoperative day only. Our findings support the concept of consensual inter-eye responses to unilateral IOP changes. Further research is warranted to elucidate the mechanisms underlying this phenomenon.

Ocular stress enhances contralateral transfer of lenadogene nolparvovec gene therapy through astrocyte networks

Lenadogene nolparvovec (GS010) was developed to treat a point mutation in mitochondrial ND4 that causes Leber hereditary optic neuropathy. GS010 delivers human cDNA encoding wild-type ND4 packaged into an rAAV2/2 vector that transduces retinal ganglion cells, to induce allotopic expression of hybrid mitochondrial ND4. GS010 clinical trials improved best-corrected visual acuity (BCVA) up to 5 years after treatment. Interestingly, unilateral treatment improved BCVA bilaterally. Subsequent studies revealed GS010 DNA in visual tissues contralateral to the injected eye, suggesting migration. Here we tested whether unilateral intraocular pressure (IOP) elevation could influence the transfer of viral ND4 RNA in contralateral tissues after GS010 delivery to the IOP-elevated eye and probed a potential mechanism mediating translocation in mice. We found IOP elevation enhanced viral ND4 RNA transcripts in contralateral visual tissues, including retinas. Using conditional transgenic mice, we depleted astrocytic gap junction connexin 43 (Cx43), required for distant redistribution of metabolic resources between astrocytes during stress. After unilateral IOP elevation and GS010 injection, Cx43 knockdown eradicated ND4 RNA transcript detection in contralateral retinal tissues, while transcript was still detectable in optic nerves. Overall, our study indicates long-range migration of GS010 product to contralateral visual tissues is enhanced by Cx43-linked astrocyte networks.

Oral Scutellarin Treatment Ameliorates Retinal Thinning and Visual Deficits in Experimental Glaucoma.

Purpose: Intraocular pressure (IOP) is currently the only modifiable risk factor for glaucoma, yet glaucoma can continue to progress despite controlled IOP. Thus, development of glaucoma neurotherapeutics remains an unmet need. Scutellarin is a flavonoid that can exert neuroprotective effects in the eye and brain. Here, we investigated the neurobehavioral effects of scutellarin treatment in a chronic IOP elevation model.Methods: Ten adult C57BL/6J mice were unilaterally injected with an optically clear hydrogel into the anterior chamber to obstruct aqueous outflow and induce chronic IOP elevation. Eight other mice received unilateral intracameral injection of phosphate-buffered saline only. Another eight mice with hydrogel-induced unilateral chronic IOP elevation also received daily oral gavage of 300 mg/kg scutellarin. Tonometry, optical coherence tomography, and optokinetics were performed longitudinally for 4 weeks to monitor the IOP, retinal nerve fiber layer thickness, total retinal thickness, visual acuity, and contrast sensitivity of both eyes in all three groups.Results: Intracameral hydrogel injection resulted in unilateral chronic IOP elevation with no significant inter-eye IOP difference between scutellarin treatment and untreated groups. Upon scutellarin treatment, the hydrogel-injected eyes showed less retinal thinning and reduced visual behavioral deficits when compared to the untreated, hydrogel-injected eyes. No significant difference in retinal thickness or optokinetic measures was found in the contralateral, non-treated eyes over time or between all groups.Conclusion: Using the non-invasive measuring platform, oral scutellarin treatment appeared to preserve retinal structure and visual function upon chronic IOP elevation in mice. Scutellarin may be a novel neurotherapeutic agent for glaucoma treatment.

Diurnal Cycle of Translaminar Pressure in Nonhuman Primates Quantified With Continuous Wireless Telemetry.

PurposeRecent retrospective clinical studies and animal experiments have suggested that cerebrospinal fluid pressure (CSFP) is important in glaucoma pathogenesis. Intraocular pressure (IOP) and CSFP are the driving components of the translaminar pressure (TLP), which directly effects the optic nerve head. This study measured the diurnal cycle of TLP using continuous wireless telemetry in nonhuman primates (NHPs), a common animal model of glaucoma.MethodsWe have developed an implantable wireless telemetry system based on a small piezoelectric pressure transducer with low drift. Unilateral IOP was measured in the anterior chamber of the eye, and intracranial pressure (ICP, a surrogate measure of CSFP) was measured in the brain parenchyma in four awake, behaving NHPs for periods of 22 to 281 days. IOP and ICP telemetry transducers were calibrated with direct pressure measurements in the eye (every 2 weeks) and brain (monthly). TLP was quantified in real time as IOP-ICP, and hourly means of IOP, ICP, and TLP were analyzed.ResultsResults show that mean ICP is significantly higher by an average of 4.8 ± 0.8 mmHg during sleeping hours in NHPs (P < 0.01). IOP showed a small but significant nocturnal elevation in two of four animals despite NHPs sleeping upright (P < 0.05). TLP was significantly lower during sleep (7.1 ± 0.6 mmHg; P < 0.01) than when the animals were awake and active (11.0 ± 0.9 mmHg), driven primarily by the large increase in ICP during sleep.ConclusionsThe 56% increase in TLP during waking hours in NHPs matches the increase in TLP due to postural change from supine to upright reported previously in humans.

Selective Early Glial Reactivity in the Visual Pathway Precedes Axonal Loss, Following Short-Term Cerebrospinal Fluid Pressure Reduction.

To examine the early glial reactivity and neuron damage in response to short-term cerebrospinal fluid pressure (CSFp) reduction, as compared with intraocular pressure (IOP) elevation. The experiment included 54 male Sprague-Dawley rats with elevated translaminar cribrosa pressure difference (TLPD), defined as IOP minus CSFp. These rats underwent either continuous CSF drainage for 6 hours (n = 18), or unilateral IOP elevation to 40 mm Hg for 6 hours (n = 18). For control, 18 normal rats were anesthetized for 6 hours. Orthograde axonal transport was examined by intravitreal injection of 3% rhodamine-β-isothiocyanate. We also used transmission electron microscopy to display the ultrastructural features of retinal ganglion cell axons in the optic nerve head. Early glial reactivity in the retina, lateral geniculate nucleus (LGN), and superior colliculus (SC) was detected by immunostaining and Western blot for the glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS). We also observed the glial reactivity in the inferior colliculus and hippocampus to rule out possible influences of CSF dynamics and composition. Anterograde staining with 3% rhodamine-β-isothiocyanate revealed decreased fluorescence intensity of the SC and LGN projected from both lower CSFp and higher IOP eyes. Transmission electron microscopy showed loss of axons from the optic nerve head in the high-IOP group, but not in the low-CSFp group. Compared with the anesthesia control group, GFAP expression was significantly increased in the retina, LGN, and SC, whereas GS expression was only increased in the retina following CSFp reduction. However, their expressions were not significantly elevated in the inferior colliculus and hippocampus. In the high-IOP group, expressions of GFAP and GS were significantly increased in the retina, LGN, and SC. Visual system neurons may be much more sensitive than other nervous tissues. Following short-term CSFp reduction, early glial reactivity may precede axonal loss. Changes of translaminar cribrosa pressure difference in both experimental low-CSFp and high-IOP groups induce selective early glial reactivity. The neuron damage from abnormally low CSFp may be pathogenetically similar to high IOP.

Changes in Axial Length and Refractive Error After Noninvasive Normalization of Intraocular Pressure From Elevated Levels

To explore the changes in axial length and refractive error after noninvasive normalization of intraocular pressure (IOP) from elevated levels. A prospective observational study. We enrolled 51 consecutive patients with abnormally elevated unilateral IOP (≥10 mm Hg compared with that of the fellow eye, in which the IOP was ≤21 mm Hg). In all patients, the keratometric value and axial length were obtained with the aid of an IOLMaster before and after IOP normalization (defined as attainment of an IOP difference of ≤3 mm Hg compared with the fellow eye, with or without topical application of ocular hypotensive therapy). We focused principally on IOP, axial length, the keratometric value, and the predicted refractive difference (the predicted refractive error after IOP normalization upon placement of an IOL with a power for emmetropia correction determined prior to IOP normalization). The axial length was significantly reduced from 23.5 to 23.3 mm after IOP normalization, from 45.9 mm Hg to 14.3 mm Hg (P < .001). The change in IOP correlated with that of the axial length (r = 0.826, P < .001), but not with the change in the keratometric value (P = .618). The change in axial length per 10 mm Hg IOP decrease was -0.06 mm (P < .001). The IOP change was correlated with the predicted refractive difference (r = 0.693, P < .001); the predicted refractive difference per 10 mm Hg IOP decrease was +0.15 diopter (P < .001). The axial length decreased and the predicted refractive difference increased (hyperopia) as IOP decreased. Therefore, a possible risk of postoperative hyperopic shift should be considered when biometric examination for IOL power calculation is performed in a patient with an abnormally elevated IOP.

Functional and structural evaluation of lamotrigine treatment in rat models of acute and chronic ocular hypertension

Voltage gated sodium channels (Nav), are proposed mediators of neuronal damage in ischemic and excitotoxicity disease models. We evaluated the neuroprotective effects of lamotrigine, a Nav blocker, in the acute and chronic rat ocular hypertension models. Additionally, expression of the main Nav subtypes in the optic nerve (ON) was assessed to test whether their upregulation plays a role in the pathogenesis of ocular hypertension induced optic neuropathy. Unilateral intraocular pressure (IOP) elevation was induced for 60 min (80 mmHg) and 14–21 days (670–859 mmHg*day) in the acute and chronic models, respectively. Lamotrigine was administered at dosages of 10 mg/kg twice daily and 12.5 mg/kg once daily in the acute (n = 9) and chronic (n = 11) trials, respectively. Treatment began 2 days prior to IOP elevation until sacrifice. Outer and inner retinal function was evaluated with dark- and light-adapted flash electroretinography and pattern electroretinography, respectively, 6 and 14 days post acute IOP elevation and 13, 28 and 48 days post chronic IOP elevation. Retinal ganglion cell and axon densities and inflammatory reaction were evaluated through Fluorogold, Bielschowsky's silver impregnation and ED1 labeling respectively. Immunohistochemistry for Nav1.1, 1.2 and 1.6 was performed in ONs of untreated rats 7 and 15 days post IOP elevation in the acute model and after 7, 28 and 50 days in the chronic model. In the acute model, no differences were found in the a-wave amplitudes between lamotrigine-treated and vehicle-treated rats. B-wave amplitudes decreased by 40–66% in both treatment groups 6 days post IOP elevation, with no significant difference between groups (p = 0.38). However, a partial recovery of b-wave amplitudes was found in lamotrigine-treated rats between day 6 and day 14 post procedure (p < 0.05). No differences were found in any other parameter tested in this model. Similarly, lamotrigine treatment did not result in any beneficial effect in structural parameters of the chronic model. Functional evaluation of this model was inconclusive due to super-normal values in the hypertensive eyes. Up-regulation of Nav1.1 and 1.2 expression was found in both models, beginning by day 7; an increase of the former continued in a time-dependent manner in the chronic model. Nav1.6 labeling was inconclusive. In conclusion we found lamotrigine treatment to be mostly ineffective in both acute and chronic ocular hypertension models.

Cell Proliferation and Interleukin-6–Type Cytokine Signaling Are Implicated by Gene Expression Responses in Early Optic Nerve Head Injury in Rat Glaucoma

In glaucoma, the optic nerve head (ONH) is the principal site of initial axonal injury, and elevated intraocular pressure (IOP) is the predominant risk factor. However, the initial responses of the ONH to elevated IOP are unknown. Here the authors use a rat glaucoma model to characterize ONH gene expression changes associated with early optic nerve injury. Unilateral IOP elevation was produced in rats by episcleral vein injection of hypertonic saline. ONH mRNA was extracted, and retrobulbar optic nerve cross-sections were graded for axonal degeneration. Gene expression was determined by microarray and quantitative PCR (QPCR) analysis. Significantly altered gene expression was determined by multiclass analysis and ANOVA. DAVID gene ontology determined the functional categories of significantly affected genes. The Early Injury group consisted of ONH from eyes with <15% axon degeneration. By array analysis, 877 genes were significantly regulated in this group. The most significant upregulated gene categories were cell cycle, cytoskeleton, and immune system process, whereas the downregulated categories included glucose and lipid metabolism. QPCR confirmed the upregulation of cell cycle-associated genes and leukemia inhibitory factor (Lif) and revealed alterations in expression of other IL-6-type cytokines and Jak-Stat signaling pathway components, including increased expression of IL-6 (1553%). In contrast, astrocytic glial fibrillary acidic protein (Gfap) message levels were unaltered, and other astrocytic markers were significantly downregulated. Microglial activation and vascular-associated gene responses were identified. Cell proliferation and IL-6-type cytokine gene expression, rather than astrocyte hypertrophy, characterize early pressure-induced ONH injury.

Global Gene Expression Changes in Rat Retinal Ganglion Cells in Experimental Glaucoma

Intraocular pressure (IOP) is an important risk factor in glaucoma. Gene expression changes were studied in glaucomatous rat retinal ganglion cells (RGCs) to elucidate altered transcriptional pathways. RGCs were back-labeled with Fluorogold. Unilateral IOP elevation was produced by injection of hypertonic saline into the episcleral veins. Laser capture microdissection (LCM) was used to capture an equal number of RGCs from normal and glaucomatous retinal sections. RNA was extracted and amplified, labeled, and hybridized to rat genome microarrays, and data analysis was performed. After selected microarray data were confirmed by RT-qPCR and immunohistochemistry, biological pathway analyses were performed. Significant changes were found in the expression of 905 genes, with 330 genes increasing and 575 genes decreasing in glaucomatous RGCs. Multiple cellular pathways were involved. Ingenuity pathway analysis demonstrated significant changes in cardiac beta-adrenergic signaling, interferon signaling, glutamate receptor signaling, cAMP-mediated signaling, chemokine signaling, 14-3-3-mediated signaling, and G-protein-coupled receptor signaling. Gene set enrichment analysis showed that the genes involved in apoptotic pathways were enriched in glaucomatous RGCs. The prosurvival gene Stat3 was upregulated in response to elevated IOP, and immunohistochemistry confirmed that Stat3 and phosphorylated-Stat3 levels were increased in RGCs in experimental glaucoma. In addition, the expression of several prosurvival genes normally expressed in RGCs was decreased. There are extensive changes in gene expression in glaucomatous RGCs involving multiple molecular pathways, including prosurvival and prodeath genes. The alteration in the balance between prosurvival and prodeath may contribute to RGC death in glaucoma.

Global changes in optic nerve head gene expression after exposure to elevated intraocular pressure in a rat glaucoma model.

In glaucoma, the optic nerve head (ONH) is the likely site of initial injury and elevated intraocular pressure (IOP) is the best-known risk factor. This study determines global gene expression changes in the pressure-injured ONH. Unilateral sustained IOP elevation (glaucoma, n = 46) or optic nerve transection (n = 10) was produced in rats. ONHs were removed, and the retrobulbar optic nerves were graded for degeneration. Gene expression in the glaucomatous ONH with extensive injury was compared with that in the fellow ONH (n = 6/group), by using cDNA microarrays. Data from 12 arrays were normalized, significant differences in gene expression determined, and significantly affected gene classes identified. For the remaining ONH, grouped by experimental condition and degree of injury, quantitative reverse transcriptase-PCR (qPCR) and ANOVA were used to compare selected message levels. Microarray analysis identified more than 2000 significantly regulated genes. For 225 of these genes, the changes were greater than twofold. The most significantly affected gene classes were cell proliferation, immune response, lysosome, cytoskeleton, extracellular matrix, and ribosome. A 2.7-fold increase in ONH cellularity confirmed glaucoma model cell proliferation. By qPCR, increases in levels of periostin, collagen VI, and transforming growth factor beta1 were linearly correlated to the degree of IOP-induced injury. For cyclinD1, fibulin 2, tenascin C, TIMP1, and aquaporin-4, correlations were significantly nonlinear, displaying maximum change with focal injury. In the ONH, pressure-induced injury results in cell proliferation and dramatically altered gene expression. For specific genes, expression levels were most altered by focal injury, suggesting that further array studies may identify initial, and potentially injurious, altered processes.

Measurement of amino acid levels in the vitreous humor of rats after chronic intraocular pressure elevation or optic nerve transection.

To investigate whether the levels of free amino acids and protein in the vitreous of rat eyes are altered with chronic intraocular pressure (IOP) elevation or after optic nerve transection. The concentrations of 20 amino acids in the vitreous humor were measured by high-performance liquid chromatography in both eyes of 41 rats with unilateral IOP elevation induced by translimbal photocoagulation. Eyes were studied 1 day and 1, 2, 4, and 9 weeks after initial IOP elevation. The same amino acids were measured in 41 rats 1 day and 2, 4, and 9 weeks after unilateral transection of the orbital optic nerve. The intravitreal protein level was assayed in additional 22 rats with IOP elevation and 12 rats after nerve transection. Two masked observers evaluated the amount of optic nerve damage with a semiquantitative, light-microscopic technique. In rats with experimental glaucoma, amino acid concentrations were unchanged 1 day after treatment. At 1 week, 4 of 20 amino acids (aspartate, proline, alanine, and lysine) were higher than in control eyes ( < or = 0.01), but this difference was nonsignificant after Bonferroni correction for multiple simultaneous amino acid comparisons (none achieved < 0.0025). No amino acid was significantly different from control in the nerve transection groups (all > 0.05). Vitreous protein level was significantly higher in glaucomatous eyes than their paired controls at 1 day ( < 0.0001) and 1 week ( < 0.002). One day and 1 week after optic nerve transection, vitreal proteins were significantly elevated compared with control eyes from untreated animals ( < 0.0020 and < 0.0022, respectively), though not compared with their fellow eyes ( = 0.25 and 0.10). Chronic experimental glaucoma and transection of the optic nerve increase the amount of protein in the rat vitreous above control levels. In the vitreous of rats with experimental glaucoma, a number of free amino acids were transiently elevated to a modest degree, but no significant difference in vitreous glutamate concentration was detected ( > 0.01).

Experimental Glaucoma Model in the Rat Induced by Laser Trabecular Photocoagulation After an Intracameral Injection of India Ink

A simple and reproducible rodent glaucoma model is required to elucidate the pathophysiology of damage to the optic nerve. We developed chronically elevated intraocular pressure (IOP) unilaterally in rats by injecting india ink into the anterior chamber of one eye using a 30-gauge needle. One week later, trapped carbon particles in the chamber angle formed a black band along the corneal limbus in the injected eyes. We performed direct laser photocoagulation without a gonio lens, and selectively burned the trabecular meshwork. Intraocular pressure was measured every week and laser photocoagulation was repeated until mean IOP in the experimental eyes rose above 25 mmHg. Unilateral IOP elevation was attained in all rats within 4 weeks. Twelve weeks after ink injection, we sacrificed the rats and excised the eyes for histologic analysis. The anterior chamber angle showed peripheral anterior synechia caused by laser photocoagulation, and carbon particles were engulfed by macrophages that infiltrated the ciliary cleft. In the optic nerve head, a remarkable decrease in the nerve fiber layer and cavernous degeneration were observed, suggesting glaucomatous optic nerve damage. This experimental rodent model should facilitate the study of the complex mechanisms involved in glaucoma.

Combination of systemic acetazolamide and topical dorzolamide in reducing intraocular pressure and aqueous humor formation

The study aimed to determine whether topical dorzolamide and systemic acetazolamide have an additive effect on intraocular pressure (IOP) and aqueous humor formation (AHF). This was a prospective, open-label, two-protocol clinical study. Sixteen patients with ocular hypertension or with primary open-angle glaucoma were studied. Baseline AHF was measured by computerized fluorophotometry and IOP by pneumatonometry without antiglaucoma therapy. In the first protocol, dorzolamide was randomized to one eye (N = 10) and IOP and AHF measurements were repeated. One week later, having used dorzolamide in one eye three times daily, patients had measurements performed before and after the single administration of oral acetazolamide 250 mg. In the second protocol, having used acetazolamide 250 mg four times daily for 4 to 7 days (N = 6), patients had measurements performed before and after a single drop of dorzolamide was instilled randomly into one eye. The patient continued acetazolamide and unilateral dorzolamide for 4 to 7 more days and returned for IOP and AHF measurements. Intraocular pressure and AHF were measured in treated and contralateral control eyes. In the first protocol, IOP (mmHg +/- standard deviation) was significantly (P = 0.02) lower in the dorzolamide (16.3 +/- 2.6) than in the contralateral control (19.9 +/- 2.9) eyes. Aqueous humor formation (microliter/minute +/- standard deviation) also was lower (P = 0.02) in dorzolamide eyes (1.79 +/- 0.4 vs. 2.33 +/- 0.5). After oral acetazolamide 250 mg, IOP was unchanged in dorzolamide eyes (17.6 +/- 2.0 preacetazolamide vs. 17.9 +/- 2.0 postacetazolamide), whereas it was reduced (P = 0.003) in control eyes (20.5 +/- 2.2 preacetazolamide vs. 16.9 +/- 2.3 postacetazolamide). Aqueous humor formation was reduced in control eyes (2.31 +/- 0.8 preacetazolamide vs. 1.73 +/- 0.6 postacetazolamide; P = 0.005) but not in dorzolamide-treated eyes (1.56 +/- 0.45 preacetazolamide vs. 1.77 +/- 0.39 postacetazolamide). In the second protocol, acetazolamide 250 mg four times daily symmetrically reduced IOP and AHF in both eyes. After single-drop dorzolamide in one eye, IOP and AHF did not change significantly. After 4 to 7 days of acetazolamide and unilateral dorzolamide, IOP and AHF remained reduced to a similar level in dorzolamide and control eyes not receiving topical therapy. Topical dorzolamide and oral acetazolamide, in the concentrations and doses used in this study, are not additive. Either drug alone results in maximum reduction in IOP and AHF. Concomitant glaucoma therapy of a topical and systemic carbonic anhydrase inhibitor is not warranted.