Ophthalmology Research: An International Journal

12(4): 35-39, 2020; Article no.OR.57832 ISSN: 2321-7227

Evidence of Post Trabeculectomy Optic Nerve Reperfusion by OCT Angiography

Jigyasa Sahu1*

1Department of Ophthalmology, Guru Nanak Centre, MAMC, New Delhi, India.

Author’s contribution

The sole author designed, analysed, interpreted and prepared the manuscript.

Article Information

DOI: 10.9734/OR/2020/v12i430154 Editor(s): (1) Dr. Ahmad M Mansour, American University of Beirut, Lebanon. Reviewers: (1) Ogugua Ndubuisi Okonkwo, Eye Foundation Hospital, Nigeria. (2) Nursen Yuksel, Kocaeli University, Turkey. Complete Peer review History: http://www.sdiarticle4.com/review-history/57832

Received 05 April 2020 Case Report Accepted 11 June 2020 Published 22 June 2020

ABSTRACT

Aim: To describe a case of which showed increase in optical coherence tomography (OCT) angiographic vessel densities after reduction suggesting reperfusion of optic nerve. Presentation of Case: A 55 year old female with primary open angle glaucoma was taken up for trabeculectomy in view of inadequate control of intraocular pressure (IOP) despite maximal medical therapy. In addition to routine glaucoma assessment by visual fields and nerve fiber layer assessment by OCT, OCT angiographic evaluation of peripapillary vessel density was done preoperatively. Three months after trabeculectomy, her intraocular pressure decreased from 35mmHg to 14mmHg. Compared with the preoperative baseline value, the vessel density increased significantly in all quadrants after three months from surgery as demonstrated by OCT angiography. Discussion: This case report suggests that decreased optic nerve head perfusion due to high IOP can be reversed by reduction of IOP. Conclusion: Vascular parameters like angiographic vessel density can show reversible changes as decreased blood flow reinstates and thus can be better prognostic indicators than structural parameters like OCT retinal nerve fiber layer (RNFL) in glaucoma patients.

Keywords: OCT Angiography; vessel density; ocular perfusion; trabeculectomy.

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*Corresponding author: E-mail: [email protected];

Sahu; OR, 12(4): 35-39, 2020; Article no.OR.57832

1. INTRODUCTION Patient underwent an uneventful trabeculectomy with a 4*4 triangular flap and releasable sutures Optical coherence tomography—angiography for the right eye. Postoperatively she was put on (OCT-A) gives a three-dimensional, non-invasive antibiotic steroid combination drops and atropine retinal and choroidal microcirculation vasculature drops. On postoperative day one, IOP was imaging. 20mm Hg. On examination, the eye was quiet with a well formed bleb (Indiana bleb grading, Data derived from OCT-A has shown that H2E2V2S0 ). The patient was stable and followed peripapillary vessel density, flow index and optic up every fortnight. After three months from disc perfusion are reduced in glaucomatous surgery, OCT-A was repeated for the operated compared with age-matched normal eyes [1-5]. eye. Both peripapillary (Fig. 1a-b pre and Some studies have also reported decreased postoperative respectively) and macular scans macular vessel density in glaucoma patients [6]. (Fig 2a-b pre and postoperative respectively) This decrease in vessel density progresses as showed improvement of vascular density in all glaucoma severity increases. However it is sectors as measured by automated software for unclear whether this vessel density which measurement of vessel density in Angioplex. decreases as a result of high intraocular pressure (IOP) insults could be reversed if the 3. DISCUSSION IOP was again controlled. We describe a case of advanced primary open angle glaucoma which The retinal microvasculature, especially radial showed reperfusion of the optic nerve in the form peripapillary capillaries, are the main source of of increase in peripapillary and macular vessel nutrition for retinal ganglion cells [7]. Under density after IOP reduction by trabeculectomy. effects of high IOP, there is a decreased blood 2. PRESENTATION OF CASE supply to these nourishing vessels of the retinal ganglion cells. Assessment of microvascular We report a case of a 55 year old female who impairment can thus be useful for monitoring presented to us for uncontrolled IOP in her right patients with glaucoma. eye. She was being managed elsewhere and was on maximally tolerated medical therapy. On It has been investigated using multiple imaging presentation her best corrected visual acuity was modalities that there is a link between ocular 6/6 in both eyes. IOP was 35 mm Hg and perfusion and glaucoma [1,2]. Optic nerve head 18mmHg with central pachymetry being 537 and blood flow of glaucoma patients after 542 in the right and left eye respectively. Slit trabeculectomy has been investigated by lamp examination was unremarkable in both [8], colour doppler eyes and the anterior chamber was deep. imaging [9], pulsatile ocular blood flow by fundus showed open angles in both eyes pulsation amplitude [10], scanning laser doppler (D-40-r-1+ in both eyes by Spaeth grading). flowmetry [10,11]. Optical coherence tomography Fundus exam showed C/D : 0.7 in the right eye angiography (OCT-A) gives a three-dimensional, and C/D: 0.5 in the left eye with bipolar thinning non-invasive retinal and choroidal microcircula- and deep cup in both eyes. Bayonetting and tion vasculature imaging [12]. nasal shift of vessels were evident. Macula, vessels and periphery were within normal limits The emerging literature in OCT-A has been able in both eyes. The patient underwent visual fields to establish that vessel densities in the examination which revealed bi-arcuate scotoma peripaillary and macular areas are lower in in the right eye and superior arcuate in left eye. glaucoma patients when compared to normal OCT nerve fiber layer assesment showed population [1,5]. However there is still a paucity decreased nerve fiber layer density in all of literature on improvement of microvasculature quadrants (red zones) in the right eye and in the in glaucoma patients if the IOP is lowered. inferior, inferotemporal and inferonasal quadrants Zeboulon et al. [13] in their study using OCT-A in the left eye. Macular ganglion cell complex demonstrated a very limited effect of surgically showed severe thinning (red zones) in the right induced IOP reduction on peripapillary and eye and was normal in the left eye. All these macular vessel density but the study had a very suggested advanced glaucomatous changes in short follow up of 1 month. One might argue that the right eye and moderate changes in the left one month is a very short time to re-develop lost eye. OCT-A 6*6 disc scan and 3*3 macula scan vascular networks. Other studies have reported was done by Angioplex (Cirrus HD-OCT 5000, that although structural parameters like OCT Zeiss Meditec. Inc.) preoperatively. retinal nerve fiber layer (RNFL) thickness do not

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Sahu; OR, 12(4): 35-39, 2020; Article no.OR.57832

change even with IOP reduction, a change in pre-existing vascular channels or by formation of OCT-A is apparent [14,15]. Our case did not see new vascular channels. Currently the any lamina cribrosa depth reduction as opposed differentiation between the two is not possible as to a study which reported it post trabeculectomy OCT-A detects only movement of blood cells and [15]. The quantitative assessment in our case at not the actual density and distribution of blood the image procurement level itself ensured that vessels. The possibility of formation of new no details were lost in image transfers for vascular channels in peripaillary area although analysis. Our case saw an increase in very less, cannot be denied completely. Further peripapillary as well as macular vessel densities structural studies on ocular vascular models are at three month after surgery. This suggests a required to confirm this hypothesis. need for following such patients for a longer time. Alnawaiseh et al. [16] demonstrated the In glaucoma patients, after surgical intervention, improvement of the vasculature in the form of it is mostly only the IOP which remains a follow flow density enhancement of the macular and up parameter. Other investigative modalities are optic nerve head after with either visual fields that usually do not pick up intent implantation. minor changes and OCT RNFL which does not demonstrate any further structural change in Reversibility of decreased blood flow of the optic advanced glaucoma (also known as floor effect). nerve head in glaucoma patients has been In such a setting it becomes very important to documented in our patient post trabeculectomy have another quantitative factor whose with the help of OCT-A. Elevation of IOP is well change can be monitored as an index of known to affect retinal perfusion. We hypothesise improvement. Hence there is a growing need to that as the mechanical effect of high IOP wanes incorporate OCT-A as a part of diagnostic off after surgically or medically controlling IOP, and prognostic algorithms for glaucoma ocular blood flow re-establishes itself either in patients.

Fig. 1a-b. Pre (a) and post-operative(b) angioplex OCT angiography images of 6*6 mm scan centered around the disc showing increase of vessel density in all sectors postoperatively [superior: 19.9(a), 20.3(b) ; inferior: 19.2(a), 19.9(b) ; nasal: 17.1(a), 18.1(b) ; temporal: 19.9(a), 20.2(b)] Inferior panels of the image show the depth of lamina cribrosa pre and post-operatively.

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Sahu; OR, 12(4): 35-39, 2020; Article no.OR.57832

Fig. 2a-b. Pre (a) and post-operative (b) Angioplex OCT Angiography images of 3*3 mm scan centered around fovea showing increase of vessel density in all sectors postoperatively [superior: 20(a), 22.7(b) ; inferior: 19.3(a), 22.5(b) ; nasal: 19.6(a), 22.8(b) ; temporal: 18.2(a), 22.3(b)]

So far the studies pertaining to this topic have ETHICAL APPROVAL used an external computation software like imageJ for calculation of vessel densities [17]. In As per international standard written ethical our patient, use of incorporated Angioplex permission has been collected and preserved by software provided us with precalculated values of the author(s). vessel density thus removing any errors due to image quality disruption during transfers. This COMPETING INTERESTS case gives a basis for further studies on whether reversibility of retinal and optic nerve head blood Author has declared that no competing interests flow can be used as a prognosticating index for exist. treatment of glaucoma either in the form of conventional trabeculectomy or minimally REFERENCES invasive glaucoma surgeries. 1. Liu L, Jia Y, Takusagawa HL, et al. Optical 4. CONCLUSION coherence tomography angiography of the peripapillary retina in glaucoma”. JAMA The fundamental understanding of OCT-A in Ophthalmol 2015;133:1045–52. glaucoma remains mysterious and difficult. 2. Leveque P-M, Z_eboulon P, Brasnu E, et Nevertheless OCT-A has definitely emerged as a al. Optic disc vascularization in glaucoma: reliable, objective technique with an acceptable value of spectral-domain optical coherence repeatability and reproducibility. If its role in tomography angiography. J Ophthalmol. prognosticating patients after surgical or medical 2016;2016:1–9. intervention is further consolidated by research, it 3. Chen CL, Bojikian KD, Gupta D, et al. can prove to be a boon for glaucoma Optic nerve head perfusion in normal eyes professionals. and eyes with glaucoma using optical KEY MESSAGES coherence tomography-based microangio- graphy. Quant Imaging Med Surg 2016; Increase in optic nerve head blood flow after IOP 6:125–33. reduction can be taken as a parameter of 4. Akagi T, Iida Y, Nakanishi H, et al. improvement in glaucoma cases. OCT-A Microvascular density in glaucomatous provides an excellent tool to quantify vessel eyes with hemifield visual field defects: an density in glaucoma cases. optical coherence tomography angio- graphy study. Am J Ophthalmol 2016; CONSENT 168:237–49. As per international standard informed and 5. Bojikian KD, Chen CL, Wen JC, et al. Optic written participant consent has been collected disc perfusion in primary open angle and and preserved by the authors. normal tension glaucoma eyes using

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Peer-review history: The peer review history for this paper can be accessed here: http://www.sdiarticle4.com/review-history/57832

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