Corneal Surgery in the Cat: Diseases, considerations and techniques

Abstract

Practical relevance: The ability to recognize, diagnose and treat corneal disease is essential for maintaining vision and comfort in feline patients. Being able to correctly identify appropriate techniques for surgical cases is of particular importance for success when performing corneal surgery.

Clinical challenges: Many different corneal diseases present with similar clinical signs, and it can be hard to determine the appropriate treatment for individual patients. It is essential for the clinician to understand the indications for corneal surgery, instrumentation needed and microsurgical principles prior to attempting these procedures. The prognosis following surgery and potential complications should be discussed with the client.

Audience: This review article aims to assist in decision-making and to provide detailed guidance for primary care clinicians considering referral of cats for corneal surgery. The review outlines common feline corneal diseases and associated surgical therapies performed by veterinary ophthalmologists, highlighting appropriate instrumentation and case selection. Some surgeries are explained in depth for ophthalmologists and residents in training.

Equipment: Although some procedures may be performed with common surgical equipment and supplies, most require specialized ophthalmic instrumentation and expertise, which entails significant microsurgical training and practice, as well as financial investment. Most of the procedures require an operating microscope for the best surgical outcomes; however, surgical loupes may be sufficient in some cases. Evidence base: This review article compiles information from many published references on feline corneal diseases and surgeries, complemented by the experience of the authors.

Keywords: Keratoplasty; corneal transplant; corneal ulcer; keratectomy; keratitis.

Figure 1

(a) Descemetocele in a 14-year-old male neutered domestic shorthair cat that presented with severe feline herpesvirus keratitis. (b) Postoperative conjunctival pedicle graft at 4 weeks. Note the graft is becoming incorporated within the cornea and the sutures are dissolving. The cornea surrounding the graft is clear

Figure 2

(a) Four-year-old Persian cat with corneal sequestrum and corneal vascularization; (b) 1 week postoperatively following a penetrating keratoplasty for sequestrum removal; (c) 2 weeks postoperatively; (d) 2 months postoperatively; and (e) 1 year postoperatively. Courtesy of Ellison Bentley, University of Wisconsin-Madison

Figure 3

Two-year-old male neutered Siamese cross that presented with an acute onset of corneal edema and distortion (curvature) of the corneal surface. This cat was diagnosed with feline acute corneal hydrops and a third eyelid flap was performed with a good outcome

Figure 4

Two-year-old spayed female domestic shorthair cat that presented with a cactus thorn penetrating the cornea, iris and lens. The pupil was dyscoric (abnormally shaped) and a cataract was forming at the penetration site in the lens. The injury had been present for at least 3 days. The thorn was removed carefully, and the wound was closed primarily. In cases of ocular trauma, such as this, the cat may develop an ocular sarcoma, and so the patient should be monitored closely for ocular changes

Figure 5

(a) Vacuum pillow; (b,c) vacuum pillow with patient’s head properly positioned in dorsal recumbency. Note the use of a guarded endotracheal tube, which is important when positioning patients in this manner

Figure 6

Top center: stainless steel surgical sponge bowl with 4 x 4 gauze. Top row of instruments, left to right: wire (Barraquer) eyelid speculum, 0.12 mm Colibri-style forceps, straight tying forceps, curved tying forceps, left corneal section scissors, right corneal section scissors, non-locking curved microneedle holders (spring-handled), Beaver blade handle with number 64 Beaver blade directly above, 0.3 mm Bishop-Harmon forceps. Bottom row of instruments, left to right: Stevens tenotomy scissors, 0.3 mm Colibri forceps, 0.3 mm fixation forceps, Westcott tenotomy scissors, Vannas scissors, Martinez corneal dissector, Westcott stitch scissors

Figure 7

Superficial lamellar keratectomy being performed. The surgeon had already outlined the area to be removed and here used 0.12 mm Colibri forceps (right) to grasp and elevate the edge of the cornea being removed. The number 64 Beaver blade (left) was used to dissect the corneal lamellae