CaseWise 18

Ring of Steel After Glaucoma Surgery

Dr. Chennamsetty Alekhya, Dr. Vinay Nangia, Dr. Sarang Lambat
Suraj Eye Institute, Nagpur, India

INTRODUCTION

The ‘Ring of Steel’ is a fibrosis around the conjunctiva which has been exposed to Mitomycin-C during trabeculectomy surgery. It localises and limits the extent of the pale bleb. The posterior incision of limbus based surgery often results in a posterior restricting scar which pushes aqueous towards the limbus forms thin walled, cystic bleb. They have increased risk of bleb leak and endophthalmitis.1

The ‘Ring of Steel’ is a fibrosis around the conjunctiva which has been exposed to Mitomycin-C during trabeculectomy surgery. It localises and limits the extent of the pale bleb. The posterior incision of limbus based surgery often results in a posterior restricting scar which pushes aqueous towards the limbus forms thin walled, cystic bleb. They have increased risk of bleb leak and endophthalmitis.1

CASE REPORT 1

A female, 48 years of age, reported to us for routine eye evaluation. She had a visual acuity of 6/6 in both eyes. Anterior segment examination was normal in both eyes. Intra Ocular Pressure (IOP) was 32 mmHg in the right eye and 28 mmHg in left eye. Gonioscopy showed open angles in both eyes. Central corneal thickness was 530 micrometre in both eyes. Fundus examination showed 0.8:1 vertical cup disc ratio (VCDR) in right eye and 0.6:1 VCDR in left eye. Spectral domain Optical Coherence Tomography (SDOCT) showed global Retinal Nerve Fibre Layer (RNFL) thinning in right eye and RNFL thinning in supero temporal and infero temporal quadrants in left eye. She was diagnosed as primary open angle glaucoma in both eyes. She was advised brimonidine 0.2%+timolol 0.5% combination eye drops for left eye. She underwent trabeculectomy with mitomycin C in right eye. IOP after one week was 12mmHg in right eye. After 1 month, IOP was 14mmHg in right eye. After 3 months, IOP was 24 mmHg in right eye. Anterior segment examination showed thin, cystic bleb with ring of steel formation around the bleb (Fig.1). She was advised levobunolol 0.5% eye drops for right eye.

CASE REPORT 2

A male, 55 years of age, reported to us with chief complaints of diminution of vision in left eye since 1 year. He had a visual acuity of 6/9 in both eyes. He was operated for cataract, 4 years back in both eyes.  Anterior segment examination showed pseudophakia in both eyes. Intra Ocular Pressure (IOP) was 28 mmHg in the right eye and 30 mmHg in left eye. Gonioscopy showed open angles in both eyes. Central corneal thickness was 490 micrometre in both eyes. Fundus examination showed 0.85 vertical cup disc ratio (VCDR) and RNFL defects superotemporally and inferotemporally in both eyes. SDOCT showed RNFL thinning in supero- temporal and infero temporal quadrants and also globally in both eyes. He was advised trabeculectomy with mitomycin C in both eyes. He underwent trabeculectomy with mitomycin C, first in left eye. IOP after one week was 16mmHg with functional bleb in left eye. After 1 month, IOP was 18mmHg in left eye. After 4 months, ring of steel formation around the bleb (Fig.2) was noted with an IOP of 26 mmHg in left eye. He was put on anti glaucoma therapy and bleb needling was advised.

DISCUSSION

In the past, we relied on limbus based flaps and local application of anti-metabolite due to concern about post operative leaks. Dr. Khaw’s clinical observation of all cystic blebs 2, had two things in common. The first was restricted posterior flow due to a ring of scar tissue, which he called the ring of steel. The second was a source of anterior limbal drainage of aqueous. The restricted flow from the posterior incision and an aqueous drainage at the limbus encourages the formation of an anterior, focal cystic bleb, a finding that was in favour of limbal-based flaps. A fornix-based incision, in contrast allowed a larger area of anti metabolite treatment, without a posteriorly placed restricting scar, resulting in the formation of diffuse bleb.2 Additionally, incompletely cut sides of a large scleral flap leads to posteriorly directed, diffuse flow of aqueous resulting in formation of a more diffuse, non cystic bleb.2 Thus, the ring of steel can be prevented by fornix based flap, broader application of anti metabolites and an incomplete side cuts of scleral flap, not reaching up to the limbus.2 Long term control of IOP, after trabeculectomy with mitomycin C can be achieved by prevention of ring of steel formation.

REFERENCES

1.Khaw PT, Jones E, Mireskandari K, et al. Modulating wound healing after glaucoma surgery. Curr Opin Ophthalmol.2001 April. 2004;doi. 10.1097/00055735-200104000-00011

2. Enhanced Trabeculectomy – The Moorfields  Safer Surgery SystemBettin P, Khaw PT (eds): Glaucoma Surgery. Dev Ophthalmol. Basel, Karger, 2012, vol 50, pp 1–28. doi: 10.1159/000458483

3. Kurado et al. Fornix- based versus limbal-based conjunctival flaps in Trabeculectomy with mitomycin C in high risk patients, Clin Ophthalmol May2014 doi: 10.2147/OPTH.S61342

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