Chapter 1 Surgical instrumentation

Adaptations for large animals and special species ophthalmic surgeries 11

Surgical instruments for ophthalmic surgeries 11

Instrument care, storage, and sterilization 13

Introduction

Since the 1960s magnification has had a major influence on advances in ophthalmic surgery and instrumentation. With magnification of the ophthalmic surgical field, incisions previously deemed quite satisfactory were viewed as irregular, and wound apposition as imperfect. The standard ophthalmic surgical instruments, as observed under 10–20× magnification, were too large and impaired the surgeon’s view of the surgical field. Forceps were viewed to compress and occasionally tear tissues. The standard ophthalmic needle holders grasped the smaller needles poorly, often flattening the curved needles. The working distance between the surgical field and the bottom of the operating microscope limited both the number and the size of ophthalmic instruments. As a result, a second type of ophthalmic instrument evolved – smaller instruments for microsurgery.

While surgical instrumentation for extraocular procedures partially utilizes general surgical instruments, surgical instruments for conjunctival, corneal, and intraocular surgical procedures require an investment in both standard size and microsurgical ophthalmic instruments. Both the standard and microsurgical ophthalmic instruments are small and delicate in comparison to the general surgical instruments. Long-term use and optimal surgical results with these ophthalmic instruments necessitate prudent care and use.

The investment in the standard, microsurgical or a combination of ophthalmic instrumentation varies with their predicted amount of use. The most important instruments are the corneoscleral and conjunctival scissors, and needle holders; these instruments should be the best available. If microsurgical instruments are selected, tying forceps rather than needle holders are used for the small ophthalmic sutures, and these thumb forceps should be of high quality.

Design of ophthalmic instruments

A large assortment of standard and microsurgical instruments is available to the veterinarian contemplating corneal and intraocular surgery. The basic design of these instruments includes several common construction features that facilitate their intended use. The standard ophthalmic instruments are usually about 120–140 mm long; the microsurgical instruments are about 100 mm long (20–30% smaller). These limitations are related to two factors. First, the instruments must be sufficiently large to be comfortably grasped and manipulated. Secondly, the working distance of most operating microscopes varies with the magnification but is usually between 150 and 250 mm. If the instruments are too large, inadvertent contact and the resultant contamination with the bottom of the operating microscope may occur.

The diameters of the handles of most of the ophthalmic spatulas and knives are about 6–7 mm. The width of the handles of the larger needle holders, scissors, and thumb forceps is about 10–12 mm. The shape of these instruments also directly influences their use. Instruments with 5–6 mm diameter handles often have rounded or four or six sides to permit convenient rotation or turning of the handle while grasping the instrument. Instruments that are flat or expand in only one direction, like corneoscleral scissors or the different thumb forceps, have handles that are flat or serrated for grasping with the fingers and limited to no rotation. To facilitate grasping and manipulation of these small instruments without slipping, the handles are usually serrated, knurled or six-sided to accommodate and limit placement of the fingers on these gripping areas. If these irregular surfaces are too small, the grasp of the instrument may be less than secure. If these serrated areas are too large, the large finger placement area may actually limit manipulation and even snag sutures during tying. All ophthalmic instruments are constructed from high-quality stainless steel or now more often from titanium, with dull surfaces to minimize light reflections.

Thumb forceps and scissors for corneal and intraocular procedures are usually hinged with different mechanisms to facilitate their opening. The three most common hinges include the X-hinge, the vertical pin hinge, and the bar hinge (Fig. 1.1). The common X-hinge for scissor blades or needle holder tips is usually joined by small screws or pins, and often the handles converge to become spring mechanisms that maintain the instrument in an open position. With vertical pin hinges, as in iris scissors, the hinge pin is deformed as the scissor blade is closed to act as a spring device to open the blades upon release. The bar hinge is typical of most thumb forceps, and consists of the junction of the base of both handles; tension of these handles closes the forceps blades and release results in the forceps tips opening. All of these hinges are very delicate and, if extended too far, can easily bend or break.

Fig. 1.1 The different hinge mechanisms used for ophthalmic instruments: (A) X-type; (B) vertical pin; (C) bar hinge.

Most of the standard and microsurgical ophthalmic instruments are designed for a single purpose. Hence, the standard corneal or intraocular surgical instrument pack includes several instruments. Occasionally, these instruments are designed to perform two or more functions. One example is the tying thumb forceps. Its tip usually includes teeth (1 × 2) which permit grasping of the cornea and/or conjunctiva. Just proximal to its tip is a flat tying platform to grasp sutures during tying and construction of knots. These multiple purpose forceps are usually heavily used during corneal and intraocular surgical procedures and can easily become malaligned.

During microsurgery, the tips of the ophthalmic instruments are often the only parts of these instruments that are visible. In addition, many microsurgical instruments possess angled tips to facilitate their use at higher magnifications, and minimize obstruction of the surgical field.

Ophthalmic surgical instruments

Ophthalmic surgical instruments are often developed for specific tasks and functions. As a result, a considerable choice of standard and microsurgical ophthalmic instruments is available. A certain number of these instruments are essential and recommended for different small and large animal ophthalmic surgeries. For convenience, instruments for the different ophthalmic surgical procedures are listed later in the chapter. They include:

• Table 1.2 – instruments for orbital surgeries

• Table 1.3 – instruments for eyelid surgeries

• Table 1.4 – instruments for conjunctival and corneal surgeries

• Table 1.5 – instruments for intraocular and cataract surgeries

• Box 1.1 – instruments for vitreoretinal surgeries.

Table 1.2 General surgical instruments for orbital surgeries

Instrument	Purpose
Allis tissue forceps	Hold and position tissues
Bard–Parker™ handle and blades	Incise the eyelids
Bishop–Harmon forceps, toothed	Grasp the conjunctiva and nictitans
Cannula: 19 g	Irrigation of the external eye
Enucleation scissors, large, curved	Incise the optic nerve
Eyelid speculum, wire	Retract the lids and maintain the palpebral fissure
Wet field or disposable cautery	Hemostasis
Jameson muscle hook	Manipulate the extraocular muscles
Metzenbaum scissors, medium	Incise and separate the orbital tissues
Mosquito forceps (2 curved, 2 straight)	Grasp tissues and for hemostasis
Needle holder, medium	Grasp and manipulate needle
Saline cup, small	Hold saline for moistening of tissues
Silicone bulb for irrigation	Irrigate the external eye
Tenotomy scissors, curved	Incise the conjunctiva and nictitans
Towel clamps (4 large, 4 small)	Maintain the surgical drapes

Table 1.3 Surgical instruments for eyelid surgeries

Instrument	Purpose
Towel forceps (4 large, 4 small)	Secure the drapes to the patient
Wire eyelid speculum (Barraquer)	Retract the lids and expose the conjunctiva/nictitans
Small curved Mayo scissors (Mayo/Metzenbaum)	Perform lateral canthotomy
Stainless steel cup	Hold saline/lactated Ringer’s solution for ocular irrigation
Silicone bulb and cannula	Periodically moisten the eye
Entropion/chalazion forceps	With an oval-to-round ring and solid base plate. Designed to clamp and stabilize the lid
Cilia forceps	With smooth tips designed to epilate the cilia
Bishop–Harmon forceps	Both serrated and 1 × 2 teeth tips. Good general tissue forceps
Lid plate	Plastic or stainless steel. Holds the lids taut and protects the cornea from surgical manipulations
Beaver™ scalpel handle	Use Beaver No. 6400 or 6700 microsurgical blade to incise eyelid skin/conjunctiva
Standard needle holder (Castroviejo/Barraquer)	Standard size recommended to accommodate the larger needles and suture sizes. Some prefer holders with a lock device
Tenotomy scissors (Steven’s) curved/straight	Two different sizes recommended. Blunt tips preferred

Table 1.4 Surgical instruments for conjunctival and corneal surgeries

Instrument	Purpose
Instruments for both surgeries
Towel clamps (8)	Secure surgical drapes
Small curved Mayo scissors (Mayo/Metzenbaum)	Lateral canthotomy
Stainless steel cup	Hold saline/lactated Ringer’s solution
Silicone bulb and cannula	Periodically moisten the eye
Wire lid speculum (adult/pediatric: Barraquer)	Retract eyelid/expose cornea
Small needle holder	Suture lateral canthotomy
Tissue forceps: tooth/smooth (Adson)	Grasp conjunctiva/cornea
Beaver™ scalpel handle (Nos 6400 and 6500 microsurgical blades)	Incise cornea
Tenotomy (Steven’s) scissors	Cut conjunctiva/sutures
Castroviejo needle holder	Use with 5-0 to 10-0 sutures
For corneal surgeries
Corneal section scissors (right/left pair)	Cut cornea/limbus/sclera
Martinez or Gill dissector	Bluntly separate corneal stromal layers
Calipers	Operative measurements
Cyclodialysis spatula	Manipulate iris, lens, vitreous
Disposable ophthalmic cautery	Hemostasis/cut iris
Corneal trephines (5–9 mm)	For keratoplasty
Microsurgery needle holder	For keratoplasty

Table 1.5 Surgical instruments for intraocular surgery in animals

Instrument	Purpose
Towel clamps (4 large, 4 small)	Secure surgical drapes
Small curved Mayo scissors	Lateral canthotomy
Saline cup	Hold saline/lactated Ringer’s solution
Silicone bulb and cannula (cannula: 19 g/25 g)	Periodically moisten the eye
Eyelid speculum (adult/pediatric)	Retract eyelid/expose cornea
Small needle holder	Suture lateral canthotomy
Tissue forceps: toothed/smooth (Adson)	Grasp conjunctiva/cornea
Tying forceps with teeth	Grasp cornea/sutures
Beaver scalpel handles (Nos 6400, 6500, and 6700 microsurgical blades and keratome)	Incise cornea/limbus/sclera
Tenotomy scissors (Steven’s)	Cut conjunctiva
Utility scissors (Steven’s tenotomy)	Cut sutures
Corneoscleral scissors (right/left pair)	Incise cornea/limbus/sclera
Iris scissors	Incise iris
Extracapsular lens forceps	Grasp anterior lens capsule
Capsulectomy forceps (Utrata) (capsulorhexis)	Tear/remove anterior lens capsule
Lens loop	Slide lens from eye
Cyclodialysis spatula	Separate tissues
Muscle hook (Jameson)	Rotate globe/cataract surgery
Needle holder (standard/microsurgery)	Suturing
Other
Calipers	Operative measurements
Disposable cautery (sterile)	Hemostasis/cut iris
Intraocular forceps	Grasp/remove lens capsule/fragments
Intraocular scissors	Cut anterior lens capsule
Vannas capsulotomy scissors	Cut anterior lens capsule
Intraocular lens forceps/hook	Position or dial intraocular lens

General

• Good quality operating microscope.

• Viewing system for the posterior segment: Machemer irrigating lens, other sew-on ring sets, or non-contact BIOM system. A more expensive wide-angle system is available. Both systems can be used in dogs. These systems use indirect ophthalmoscope principles (which invert the ocular fundus appearance) and may require an inverter for use.

• Vitrectomy system with light-illuminating sources, electrocautery, and air infusion. Newer units may also have ultrasonic fragmentation and silicone oil pumps. The vitrectomy unit is usually a guillotine-type cutter on the side of a 20 g blunt tube.

Instruments

• Microvitreoretinal (MVR) blades (20 g)

• High-viscosity infusion tubes (4 mm cannula)

• Scleral plugs and plug holder

• Light pipes

• Electrocautery sets

• Vitreous scissors and forceps

• Silicone-tipped 20 g needles

• Charles (fluted) needle and handle

• Laser endocoagulation system

• PFCLs (perfluorocarbons)

• Silicone oil (1000–5000 cSt)

These instruments are presented in further detail.

Eyelid specula

Eyelid specula are used to retract the eyelids and enhance exposure of the conjunctiva, cornea, and globe. The ideal eyelid speculum should be strong enough to retract the eyelids to the maximal amount possible, but sufficiently lightweight to prevent direct pressure on the cornea and globe. The most versatile eyelid speculum for small animals is the wire type. For most breeds of dogs and cats, the Barraquer wire speculum is preferred with 14 mm blades and an overall length of 40 mm (Fig. 1.2). The pediatric size Barraquer speculum may be useful in young and smaller animals; its blades are 11 mm and overall length is 34 mm.

Fig. 1.2 The pediatric and adult size wire eyelid specula by Barraquer. These inexpensive lid specula are the most versatile and durable for small animals.

In large dogs and large animals a heavier eyelid speculum may be necessary. Eyelid specula, such as the Guyton–Park (14 mm blades and overall length of 85 mm), Castroviejo (15 or 16 mm blades and overall length of 75–82 mm), and Williams (10 mm blades and overall length of 90 mm) can provide maximum exposure of the palpebral fissure (Fig. 1.3). Sometimes for the lid speculum to conform to the eyelid and palpebral curvatures of the horse and cow, the arms of the specula are bent slightly. With all eyelid specula, the blades should extend beneath the eyelid margins for several millimeters to adequately retract the eyelids and reduce the possibility of dislodgement. In some species, like the avian species, the palpebral fissures and eyelids are very small, and a single 4-0 to 6-0 silk suture is placed in each eyelid to keep the lids open.

Fig. 1.3 The Williams eyelid speculum is reserved for large breeds of dogs and large animals to retract the eyelids.

Tissue forceps

The different types of ocular tissue have resulted in the development of a large selection of tissue forceps with specialized tips. These tissue forceps vary by tips, shaft, handles, springs, and bar hinge (Fig. 1.4). The handles of these forceps are usually flat with serrations or knurling on the handles to facilitate their grasp. Microsurgical forceps usually have angled tips, and are about two-thirds the total length of standard ophthalmic instruments. The arms of these forceps are hinged at the base, and this hinge provides sufficient tension to maintain the tips about 5–10 mm apart. Upon digital compression, the tissue forceps tips should completely and perfectly contact each other. The tips of many forceps are angulated to prevent blockage of the surgeon’s view during surgery.

Fig. 1.4 Components of ophthalmic forceps include: tips, shaft, handles, springs and bar/X-hinge.

The major difference of the ophthalmic tissue forceps is their tips, which have highly specialized indications (Table 1.1). In selecting these tissue forceps, one should handle them individually and use those forceps that ‘feel’ the most comfortable.

Table 1.1 Tips of tissue forceps used for corneal and intraocular surgery

Tip design	Designated tissue(s) or use	Appearance
Von Graefe	Conjunctiva/nictitans
1 × 2 teeth	Cornea/conjunctiva
Splay
Dog-toothed
Colibri style tip angulation	Cornea/conjunctiva
Serrations	Cornea/conjunctiva
Tying platforms	Tying small sutures
Lens capsule
Extracapsular	Grasp/tear anterior lens capsule
Intracapsular	Grasp/hold anterior lens capsule
Utrata	Anterior capsulorhexis
Intraocular	Grasp/remove lens capsule and fragments
Combination 1 × 2 teeth tying platform	Cornea/conjunctiva and tying sutures