Chapter 1 Surgical instrumentation
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.
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.
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 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:
|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|
|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|
|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|
|Cyclodialysis spatula||Manipulate iris, lens, vitreous|
|Disposable ophthalmic cautery||Hemostasis/cut iris|
|Corneal trephines (5–9 mm)||For keratoplasty|
|Microsurgery needle holder||For keratoplasty|
|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|
|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|
• 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.
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.
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.
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.
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.
|Tip design||Designated tissue(s) or use||Appearance|
|1 × 2 teeth||Cornea/conjunctiva|
|Colibri style tip angulation||Cornea/conjunctiva|
|Tying platforms||Tying small sutures|
|Extracapsular||Grasp/tear anterior lens capsule|
|Intracapsular||Grasp/hold anterior lens capsule|
|Intraocular||Grasp/remove lens capsule and fragments|
|Combination 1 × 2 teeth tying platform||Cornea/conjunctiva and tying sutures|