Surgical procedures that can be performed in practice depend on several factors including the experience of the practitioner and availability of facilities/equipment. Apart from the simplest procedures, corneal surgery requires magnification, good illumination and microsurgical instrumentation.

 Magnification: Adequate magnification can be provided with a good pair of surgical loupes. Some can be obtained with an attached light source providing direct illumination of the surgical field. Magnification of 2.5–4× might be selected. The working distance and depth of field are important. If the magnification is low and working distance long they may offer little advantage over direct observation. It is important to be able to try on and test out loupes before purchase. Loupes may be mounted on glasses or headbands. When selecting them consider the comfort of wearing them for longer procedures.

 Good illumination: This can be provided by a good operating lamp or via a fibreoptic light mounted on a surgical loupe.

 Instrumentation: Good surgical instruments are important for corneal surgery. A kit may include instruments suitable for handling the eyelids such as eyelid specula, forceps, scissors and needle-holders that are suitable for handling the fine eyelid skin. These will be finer than the general skin instruments but not so fine as those used for handling the cornea itself. Expensive corneal surgical instruments will be ruined if they are used to handle eyelid skin. Instruments for handling conjunctiva are also required. Forceps might include St Martin's suturing forceps or Bishop-Harman forceps. Scissors suitable include blunt-tipped tenotomy scissors. For handling corneal tissue corneal forceps should be used to allow atraumatic tissue handling. A suitable pair is 0.12 Castroviejo corneal forceps or Colibri forceps. Obviously personal preference and costs play a role in decisions on which surgical instruments to purchase.

The Surgical Management of Ulcers

Corneal ulcers require surgical intervention to encourage them to heal and in some instances to save the eye. Chronic superficial corneal ulcers (indolent ulcers, superficial corneal erosions, spontaneous chronic corneal epithelial defects) are a specific form of ulcer that only involve the epithelium. There is typically a protracted history of superficial ulceration that does not heal. The surrounding epithelium shows evidence of not adhering to the underlying stroma; fluorescein underruns it and it is easily peeled off. Treatment for the condition can be readily performed under a topical anaesthetic in the vast majority of dogs. Debridement of all non-adherent epithelium is the first step. This can be achieved using cotton-tipped applicators to rub sideways from the edge of the ulcer. The cotton-tipped applicator should be regularly changed so that it continues to provide the friction required to strip off the loose epithelium. Once all the loose material is removed a grid keratotomy is typically performed. This involves using a 25-gauge needle to make superficial scratches into the anterior stroma in a grid-shaped pattern across the ulcer and extending on to the surrounding cornea. A grid keratotomy is only indicated for this form of ulcer so achieving the correct diagnosis is important.

Deeper ulcers can also be surgical candidates. Those ulcers that leave a deep defect in the stroma, or even extend to the depth of Descemet's membrane may be managed with a conjunctival pedicle graft. Placing a simple conjunctival pedicle graft is a more advanced surgical procedure but with the correct instrumentation and training it is within the reach of practitioners. If the cornea has already perforated, grafting can be performed but is probably best left to a veterinary ophthalmologist. The advantage of conjunctival pedicle grafts is that they bring support and also a blood supply to the weakened cornea. Once the graft has healed into place it may be trimmed to reduce the extent of the resulting corneal opacity. Samples from the ulcer should be taken for cytology allowing rapid identification of the presence of bacteria aiding selection of an appropriate antibiotic. A swab for culture and sensitivity should also be taken. A finger-shaped strip of conjunctiva can be fashioned to suture into the defect. During dissection of the pedicle the conjunctiva is dissected from the underlying Tenon's capsule. Care is taken that the graft is kept thin and it is fashioned to be slightly wider than the defect it has to fill. The pedicle can be an advancement style or rotation flap. The ulcer bed is prepared to receive the graft by removal of any liquefied corneal material and any epithelium that has grown down into the graft crater. The pedicle is sutured into the defect. Sutures are placed deep into the cornea without penetrating into the anterior chamber. Suture material such as 8-0 USP (0.4 metric) Coated Vicryl is suitable.

Surgery for Wounds and Foreign Bodies

Corneal wounds and foreign bodies can potentially be treated in general practice. Foreign bodies that penetrate through the cornea and impinge on intraocular structures and full-thickness lacerations with iris prolapse should ideally be assessed and managed by a veterinary ophthalmologist. Foreign bodies protruding from the corneal surface can be carefully eased out of the cornea. Sometimes it is helpful to use a hypodermic needle to prise them from the cornea. Care should be taken not to push them deeper into the cornea when trying to grasp them for removal. Corneal lacerations not involving iris prolapse can be repaired using fine suture material such as 8-0 USP (0.4 metric) Coated Vicryl. Accurate apposition of the edges is important and sutures should penetrate deep into the cornea without entering the anterior chamber.

Superficial Keratectomies

A superficial keratectomy is used to remove corneal lesions such as corneal sequestra in cats. Removal of the lesion should be performed with the benefit of good magnification. An incision around one edge of the lesion is made into the superficial layers of the corneal stroma. A No. 69 beaver blade is useful for this purpose. A lamellar dissection is made under the lesion. The cornea can readily be separated along a lamellar plane. Usually an analogy is made with this technique and of peeling an onion. Separating along a lamellar plane can be performed bluntly using an instrument such as a Martinez lamellar separator, which is a blunt spatula-like instrument. Once the lesion has been undermined, the superficial flap created can be excised with corneal scissors or a blade. The resulting defect can be treated like an ulcer. For sequestra that require a deep dissection for removal, a conjunctival pedicle graft can be used to cover the defect. Use of conjunctival grafts may reduce the recurrence rate.