QuizWise 18

  1. The “ring of steel” is most commonly seen in
    a. Limbal based conjunctival flap with focal antimetabolite application
    b. Fornix based conjunctival flap with broader antimetabolite application
    c. Following bleb revision
    d. a and b

2 . Which of the following is incorrect about ‘Moorfields Safer Surgery System’ for trabeculectomy?
a. Designed to improve surgical outcomes following trabeculectomy
b. Superior half of the globe is the safest site for trabeculectomy
c. Limbal conjunctival incision is preferred to a forniceal incision
d . Superior rectus suture is preferred to a corneal traction suture

3 . A good bleb is?
a. Thin walled cystic
b. Anterior, focal
c. Posterior, focal
d. Posterior, diffuse  

4 . Which of the following is not the modality of treatment for a patient with increased IOP after trabeculectomy?
a. Argon suturolysis
b. Bleb needling
c. Ocular digital massage
d. Conjunctival patch autograft

5 . Which of the following are risk factors for failure of trabeculectomy?
a. Neo vascular glaucoma
b. Prior vitreo retinal procedure
c. Previous conjunctival surgery
d. Irido corneal endothelial syndrome
e. All of the above

Answers :

  1. Answer – a
    Restricted posterior flow occurs due to a ring of scar tissue, which Dr. Khaw called the “ring of steel”. 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 favor of limbal-based flaps.
    Personal experience suggest that it is also seen patients who have undergone trabeculectomy with fornix based flap with MMC

Reference – 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

2. Answers – d
The Moorfields Safer Surgery System is designed to improve surgical outcomes following trabeculectomy. The system is ultimately designed to preserve the vision by minimizing complications while maintaining a desired intraocular pressure. The superior half of the globe is the safest site for the trabeculectomy due to the reduced incidence of inflammation, endophthalmitis, dysthesia and recurrent subconjunctival hemorrhages. A limbal conjunctival incision (fornix based conjunctival flap) is a less technically difficult method to achieve posterior aqueous and a diffuse bleb. A corneal traction suture (7/0 black silk suture on a semi-circular needle) is preferred to a superior rectus suture. This removes the possibility of a superior-rectus hematoma with the added benefits of a superior vector force and a reduced risk of failure.

Reference – Sumit Dhingra, Peng T Khaw et al. The Moorfields Safer Surgery System, Middle East Afr J Ophthalmol, 2009 Jul; 16(3): 112–5.doi: 10.4103/0974-9233.56220

3. Answers – d
A limbal conjunctival incision is a less technically difficult method to achieve posterior aqueous and a diffuse bleb. A good functional bleb is posterior and diffuse. A fornix-based incision allowed a larger area of anti metabolite treatment, without a posteriorly placed restricting scar, resulting in the formation of diffuse bleb.

Reference – Sumit Dhingra, Peng T Khaw et al. The Moorfields Safer Surgery System, Middle East Afr J Ophthalmol, 2009 Jul; 16(3): 112–5.doi: 10.4103/0974-9233.56220

Reference – 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

4. Answers – d
Management of filtration failure depends on the cause and may involve one or more of the following:
Ocular digital massage in an effort to force outflow through the surgical fistula.
Argon or diode laser suture lysis is useful if releasable sutures have not been used.
Needling of an encysted bleb may be performed under topical anaesthesia. It can be augmented with 5-fluorouracil to enhance the success rate.

Reference – Ref: Brad Bowling, Kanski’s Clinical Ophthalmology-A Systematic Approach, Eighth Edition.

5. Answers – e
Risk factors for surgical failure of trabeculectomy include neovascular glaucoma, certain secondary glaucomas like inflammatory and iridocorneal endothelial syndrome, previous conjunctival surgery. Antimetabolites are usually considered in the presence of risk factors for surgical failure. 

Reference – Ref: Brad Bowling, Kanski’s Clinical Ophthalmology-A Systematic Approach, Eighth Edition.

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