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Outcomes of medical and surgical management in eyes with idiopathic elevated episcleral venous pressure

Purpose: Idiopathic elevated episcleral venous pressure (IEEVP) is a rare cause of secondary glaucoma and is a diagnosis of exclusion. The aim of this study was to describe the clinical presentation and analyze the outcomes of medical and surgical management in eyes diagnosed with idiopathic elevated episcleral venous pressure. Methods: A retrospective analysis of eyes diagnosed with IEEVP over a 5-year period between April 2012 and March 2016 was performed. The demographic details, medical history, and clinical course of the cases were obtained from the medical records. Data pertaining to the severity of glaucomatous damage, response to medical management, need for surgical intervention, and their outcomes were analyzed. Results: Fifteen eyes of 13 patients were included. Thirteen eyes (86.6%) had open angle configuration. Among the 13 eyes that had glaucoma, eight eyes (61.5%) had severe glaucoma, four eyes (30.7%) had moderate glaucoma, and one eye (7.6%) had mild glaucoma. The median follow-up was 210 days. Seven of the 15 eyes (46.6%) required a glaucoma filtration procedure, and three underwent prophylactic sclerotomies. 71.4% of these eyes had complete success. One out of the seven operated eyes required choroidal drainage post-operatively. Conclusion: IEEVP is an extremely rare condition and presents with raised intra-ocular pressure and tortuous episcleral vessels. The management of IEEVP is similar to that of primary open angle glaucoma. Uveal effusion is to be anticipated, and hence, combining trabeculectomy with prophylactic sclerotomies is advisable.

The aqueous outflow is facilitated by the difference in pressure between the anterior chamber and the episcleral veins. The normal episcleral venous pressure (EVP) is 8-10 mm of Hg. [1] According to the Goldman equation, "Intra-ocular pressure (IOP) = Aqueous flow rate (F)/Coefficient of outflow facility (C) + Episcleral venous pressure (EVP)", which implies that an increase in EVP would increase the IOP. [2] The exact relationship however is not well understood. Causes of the increase in EVP include arteriovenous anomalies and venous obstruction, although a significant proportion is idiopathic. [3] Idiopathic elevated episcleral venous pressure (IEEVP) leading to secondary glaucoma was first described by Minas and Podos in 1968. [4] The evanescent venous congestion and secondary glaucoma are probably because of poor episcleral venous drainage, the cause remaining unknown. It is a diagnosis of exclusion presenting with arterialized episcleral vessels and secondary glaucoma. [5] This is a rare cause for glaucoma with most of the literature being limited to isolated case reports, the largest case series being that of six cases. [6] We report the presentation and management outcome of a series of 13 cases of IEEVP. To the best of authors' knowledge, this is by far the largest case series on this rare entity.

Methods
A retrospective chart review was performed for all cases diagnosed with IEEVP over a period of 5 years, between March 2012 and April 2016. All patients with dilated episcleral veins and a raised IOP (≥21 mmHg), without any other cause for elevation in IOP and any other contributory factors on neuroimaging [magnetic resonance imaging (MRI) brain and orbit] causing a secondary rise in EVP, were diagnosed with IEEVP and included in the study [ Fig. 1]. Cases with orbital pathologies such as thyroid eye diseases, carotid cavernous fistula, phakomatosis, idiopathic orbital inflammation, or orbital neoplasms which could cause an elevation of the EVP were excluded. Details pertaining to the patient demographics, medical history, and clinical course were extracted from the records. Eyes with structural or functional changes characteristic of glaucomatous optic neuropathy were considered to have glaucoma based on the International Society of Geographical and Epidemiological Ophthamology (ISGEO) criteria. [7] The angle was graded by modified Shaffer's grading and classified as open and closed angles as per ISGEO criteria. [7,8]  This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.

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Anderson and Parish criteria for Humphrey visual fields, glaucoma was classified as mild, moderate, or severe. [9] For those with IOP higher than 21 mm of Hg, a normal optic nerve and normal visual field were classified as ocular hypertension. [10] The fellow eye status, need for surgical intervention, type and outcomes of surgery in terms of complications (intra-operative and post-operative), post-operative IOP control, and need for anti-glaucoma medication at final follow-up were analyzed. Data were entered and analyzed in a Microsoft Excel spreadsheet.
In eyes that underwent surgery, complete success and qualified success were defined as IOP of <20 mmHg without and with one or more topical anti-glaucoma medications, respectively, at the final follow-up. Eyes which required minor interventions such as bleb needling or choroidal drainage to manage post-operative complications were also considered to have qualified success. Failure was defined as the need for a repeat glaucoma filtration procedure or glaucoma implants for IOP control after a failed trabeculectomy in these cases.

Results
Fifteen eyes of 13 patients were included. Two cases had bilateral involvement. The median age at presentation was 57 years (range: 29-72 years). There was no gender predilection or significant difference in laterality [ Table 1]. There was no association with any systemic diseases. Eleven (73.3%) out of 15 eyes had a best corrected visual acuity of 0.3 log MAR or better at presentation. Eight eyes (54%) had a clear lens at presentation, whereas the rest had early cataractous changes.
The mean IOP at presentation was 27.3 ± 8.5 mm of Hg (16-50 mm of Hg). Three eyes with IOP less than 21 mm of Hg at presentation were also included as their baseline IOP was not available but were already on anti-glaucoma medications and had glaucomatous cupping with the corresponding field defects.
Thirteen eyes (86.6%) had open angle configuration. Among them, nine eyes had blood in Schlemn's canal on visualization with gonioscopy. Two eyes had closed angles. Although angle closure was bilateral and clinically consistent with primary angle closure, dilated episcleral veins and elevated pressure were seen in only one of the eyes in both the cases.
Out of the 15 eyes included in the study, all 13 eyes (86.6%) with open angles had glaucoma; two eyes with closed angles had normal discs and visual fields. Among the 13 eyes, eight eyes (61.5%) had severe glaucoma, four eyes (30.7%) had moderate glaucoma, and one (7.6%) had mild glaucoma. Three eyes with advanced disc changes had vision less than counting fingers at 1 meter precluding Humphrey visual field testing. The average pachymetry was 524 ± 37.1 microns (465-598 microns). Two cases had bilateral IEEVP, one had ocular hypertension in the contra-lateral eye, and in the two eyes with closed angle configuration on gonioscopy, a laser peripheral iridotomy was performed.
Fourteen eyes were on topical anti-glaucoma medication at presentation. The mean number of agms used at presentation was 2.13. However, all 15 study eyes required topical anti-glaucoma medications during subsequent follow-up. The median follow-up was 210 days. Five eyes had follow-up of less than a month. Of the 15 study eyes, seven had undergone trabeculectomy augmented with Mitomycin-C, and three eyes had prophylactic sclerotomies with trabeculectomy to prevent choroidal effusion. All three cases had advanced glaucoma  and high pre-operative IOP. The average duration between diagnosis and surgery was 276 days. The mean pre-operative IOP was 30.0 ± 10.50 mmHg (20-52 mm of Hg), whereas the mean post-operative IOP was 15 ± 5.5 mmHg (6-24 mm of Hg).
None of the eyes had intra-operative complications. The mean follow-up for the eyes that underwent trabeculectomy was 334.5 days. Among the four eyes that underwent trabeculectomy without prophylactic sclerotomies, two had vascularized blebs which eventually responded to sub-conjunctival 5-flurouracil injections, one had a shallow anterior chamber without signs of choroidal effusion and was conservatively managed with cycloplegics, and one had an uneventful post-operative course. Among the three eyes that underwent trabeculectomy with prophylactic sclerotomies, one had an uneventful course, one had a failing bleb which was treated by bleb massage, and one had a developed shallow anterior chamber with choroidal detachment. They all had open angle glaucoma pre-operatively. This was managed with oral steroids and choroidal drainage.
The visual acuity improved by at least one line in four (57.1%) out of seven patients who underwent trabeculectomy, remained stable in two patients, and decreased by one line in one of the eyes over a follow-up of 20 months because of the development of cataract. The details have been provided in Table 2.
None of the seven eyes that underwent the glaucoma filtration procedure needed anti-glaucoma medications at final follow-up, whereas in eyes that did not undergo the glaucoma filtration procedure, the need for anti-glaucoma medications increased by an average of 0.9. Post-operatively, one case with an IOP of 24 mm of Hg was lost to follow-up within a month and could not be classified as success or failure. Thus, there was complete success in five (71.4%) out of seven eyes that underwent trabeculectomy, and one eye that required choroidal drainage was considered as qualified success.

Discussion
All the 15 eyes in the present study had dilated and tortuous episcleral veins with an IOP of more than 21 mm of Hg or glaucomatous cupping. There have been two major case series on IEEVP so far, one by Rhee et al. [6] included six bilateral cases and one by Talusan et al. [11] had six unilateral cases and one bilateral case. The present study includes 11 unilateral and two bilateral cases. The median age at presentation was 57 years with a wide range between 29 and 72 years. This varied age of onset has been reported in other similar studies. [6] Although a few earlier studies reported a preponderance of the condition in the right eye, and no logical conclusion could be drawn from the observation. [11,12] However, a similar pattern was not observed in the later studies and in our series too. [6] Although familial association had been reported in one of the very early studies by Minas and Podos, none of our patients had a positive family history. [13] Two of the 15 study eyes had a closed angle, and both had unilateral disease. We included them as they fulfilled the inclusion criteria of arterialized episcleral veins with a raised IOP of 21 mm of Hg or more. Also, the difference in the IOP between the contra lateral eyes was not attributable to the asymmetry in the angle configuration. Rhee et al. [6] had reported the condition in eyes with plateau iris syndrome and  suggested that the association is likely to be genetic. Nine out of the 13 eyes with an open angle had blood in Schlemn's canal, seven eyes had in all quadrants, with one each in one and two quadrants. No significant association was found between the presence of blood in Schlemn's canal and disease severity or post-operative complications. The inconsistency of the finding of blood in Schlemn's canal has been attributed to the valve mechanism between the anterior chamber and Schlemn's canal at higher IOP.
Although all cases underwent MRI of brain and orbit and were found to be normal, six cases also underwent vascular imaging in the form of either digital subtraction angiography (DSA) or magnetic resonance angiogram (MRA). However, all the patients had detailed clinical evaluation by the occuloplastic surgeons to rule out a carotid cavernous fistula (CCF) or other known contributory factors for elevated EVP, and vascular imaging was ordered based on clinical examination. Thyroid orbitopathy and CCF are two common orbital conditions that can have raised IOP secondary to an elevated EVP. It is necessary to rule out any sort of underlying orbital pathology before labeling the patient as a case of IEEVP.
The management of IEEVP is similar to that of primary open angle glaucoma. Because IEEVP is primarily an aqueous outflow pathology, aqueous suppressants are more effective than aqueous outflow enhancers. Apraclonidine in particular has been shown to be effective for lowering IOP in cases of elevated EVP because the drug causes arterial vasoconstriction, which decreases the amount of blood flow to the eye. [14] Glaucoma filtration surgery is indicated in cases where medical management fails. Several case reports point out that trabeculectomy in these eyes can be complicated by intra-operative or post-operative uveal effusions. [15][16][17] One case report recommends performing a "tight" trabeculectomy with multiple releasable sutures to titrate the IOP gradually and prevent anterior chamber shallowing during surgery. [18] In our study, seven eyes required trabeculectomy and prophylactic sclerotomies were performed in three. Pre-placed sutures were used to prevent intra-operative shallowing of the anterior chamber in cases who underwent trabeculectomy without sclerotomy. Releasable sutures were used in all eyes that underwent trabeculectomy; however, only one required the release of the suture on post-operative day 5. Five (71.4%) out of our seven cases qualified for complete success. One of these developed post-operative choroidal effusion and needed choroidal drainage because of a persistent flat anterior chamber. The effusion was noted at an IOP of 14 mm of Hg. Similar cases of post-operative choroidal effusions at normal IOP have been reported earlier. [6] Conclusion IEEVP, although a rare condition, should be considered as one of the differential diagnoses in congested eyes with glaucomatous cupping or raised IOP. It is imperative to rule out other possible associations by meticulous clinical examination and neuroimaging. The management is essentially similar to that of primary open angle glaucoma. According to our study, trabeculectomy with or without prophylactic sclerotomies offers favorable outcomes; however, long-term prospective studies are needed to confirm these observations. It is pertinent to look for post-operative choroidal effusion, even at normal IOP post-operatively in these patients.

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Conflicts of interest
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