• This technique is not commonly used in cattle, but given the effectiveness of this technique in companion animals, perhaps it should be considered more often!
• This technique is used to physically support a weakened cornea and provide blood supply directly to a corneal ulcer or injury.
• The conjunctival flap will adhere to any areas where corneal epithelium is missing providing increased blood supply, nutrition and immune response.

Uses

Advantages

• Provides direct supply of blood and therefore vascular based growth factors, fibroblasts and anti-proteases to the cornea.
• Provides physical support to the thin cornea.
• Allows continued visualization of the cornea and intraocular structures.

Disadvantages

• Conjunctival flap techniques all require dissection of conjunctiva from Tenon's capsule (episcleral fascia); if this is not performed, then flap elasticity may be reduced, which can increase the tendency of graft or flap failure.
• Will cause a degree of long term corneal opacity at the ulcer site.

Technical problems

• Requires careful technique.
• Experience and attention to detail will lead to consistent results - technically reasonably difficult in cattle to only dissect the conjunctival epithelial layer. It may be that practice at the abattoir, or similar, would improve the success rate and technical prowess of the bovine surgeon.
• Conjunctiva of the eyelid (palpebral) and conjunctiva covering the nictitating membrane is difficult to mobilize for a flap and should not be utilized if possible.

Alternative techniques

• Tarsorrhaphy.
• Suturing of ulcer - relatively small ulcers <5 mm.
• Nictitating membrane flap:
  • Useful for superficial corneal diseases but should not be used in deep, infected or melting ulcers.
  • Much simpler to perform.
  • Can be used to provide retention of contact lens for corneal suturing or reinforce a bulbar conjunctival pedicle flap.
• Enucleation Surgery: enucleation:
  • Simpler to perform.
  • Useful for irreparable ocular trauma or disease (including melting ulcers).
• Various conjunctival flap patterns:
  • 180° fornix based conjunctival graft.
  • 360° fornix based conjunctival graft.
  • Conjunctival bridge graft.

Time required

Preparation

• 10 min.
• Administration of local anesthetic Local anesthesia: overview and sedation Sedating cattle.
• Adequate restraint of cow in handling facilities – if crush is inadequate deep sedation to cause recumbency is required Bovine restraint techniques.

Procedure

• 45-60 min, dependent upon experience, size of lesion, amount of dissection necessary.

Decision taking

Criteria for choosing test

• Size and depth of ulcer – in equines, large and deep ulcers are more likely to require surgical intervention.
• Presence of corneal melting – this should be treated with antiproteinases and antimicrobials before a conjunctival graft is attempted as is currently the case in equine practice.
• C/S and/or cytology results may affect the decision of when to operate – a longer course of antimicrobials may be necessary if C&S demonstrates the empirical choice of antimicrobial is ineffective.
• Failure of ulcer to respond to medical treatment alone
• Function of animal – pet, meat, breeding animal:
  •  In the author’s experience most non-routine surgeries are charged according to the time required and the medications used. In the author’s UK practice, in 2017, this surgery would cost around £200 in professional fees, with consumables on top.