Combined Cataract Extraction and Corneal Transplantation

Cataract Surgery, 3rd Edition

PART V – Special Techniques for Cataract Extraction

Chapter 23 – Combined Cataract Extraction and Corneal Transplantation

Roger F. Steinert, MD

Contents

	•	Decision Making
	•	Combined Cataract Removal and Lamellar Posterior Endothelial Transplantation (DSEK, DSAEK, DLEK, and DMEK)
	•	Special Techniques for Combined Full-Thickness Penetrating Keratoplasty and Cataract Extraction
	•	Technique for Cataract Removal
	•	Complications

CHAPTER HIGHLIGHTS

	≫	Evaluating the corneal endothelium preoperatively: combined procedure or not?
	≫	Combined phacoemulsification and endothelial transplantation
	≫	Special techniques for open-sky cataract extraction with penetrating keratoplasty

Successful combined cataract extraction and corneal transplantation requires appropriate preoperative assessment of suitable candidates^[1–7] and attention to several specific surgical details of the combined procedure. This chapter reviews these particular issues. Mastery of corneal transplantation techniques, cataract surgery, and intraocular lens (IOL) implantation is assumed. This chapter emphasizes only those areas in which these techniques interact during the combined procedure.

Decision making

When a patient has a potentially optically significant corneal disorder simultaneous with a potentially optically significant cataract, the surgeon must assess the relative contribution of each.^[8]

Assessment of the cataract

In the presence of an abnormal cornea, visualization of the cataract is impaired. Moderate corneal, epithelial, and stromal edema can be transiently cleared for diagnostic purposes with the application of several drops of 10% glycerin. This must be preceded with topical anesthetic drops to minimize patient discomfort. Some of the usual landmarks used to assess the optical significance of the cataract are reduced or eliminated. For example, the ability to see fundus details with a direct ophthalmoscope or the appearance of the media on red reflex does not distinguish between the contributions from the cornea and those from the lens. The status of the lens in the fellow eye is a useful clue if it can be visualized and if the patient has not had an ocular condition that might be expected to lead to unilateral cataract acceleration, such as inflammation or trauma. Pupillary dilation is mandatory to maximally visualize the lens. The surgeon must guard against extraction of a minimally brunescent but optically clear lens. The prognosis for rapid recovery of excellent vision is often best in a phakic eye. Moreover, cataract extraction performed after healing of the penetrating keratoplasty allows the surgeon the opportunity to adjust the refractive status with more accurate IOL power determination.^[4,][5] Conversely, a moderate cataract often will accelerate after uncomplicated penetrating keratoplasty.^[9,][10] Both the patient and the surgeon are frustrated when visual recovery after penetrating keratoplasty is progressively impaired by cataract progression just as the corneal optics improve. No study has been able to adequately resolve the relative stress to the corneal endothelium by cataract extraction following penetrating keratoplasty compared with a simultaneous combined procedure.

Assessment of the cornea

Corneal opacity itself can be assessed by the degree to which visualization of iris and crystalline lens detail is impaired. Surface irregularity is more deceptive. Slit-lamp biomicroscopy often will not disclose optically significant surface distortions. Corneal topography evaluation with a Placido disc, photokeratoscope, or computer-assisted topographic analysis will disclose the presence of irregularities but not their relative contribution to the visual impairment. A diagnostic hard contact lens refraction is invaluable in identifying and quantifying the extent of surface irregularity and its relationship to the total visual impairment. A frequent clinical dilemma is the decision about combining cataract extraction with corneal transplantation in a patient with dense corneal guttae in the absence of clinically evident microcystic epithelial edema or stromal edema. Many patients who exhibit severe central guttate changes in the central cornea can, nonetheless, undergo successful cataract extraction without subsequent corneal decompensation. Although dense guttae can sometimes cause a mild visual impairment, it is generally best to attempt cataract surgery alone in the absence of signs or symptoms of physiologic corneal endothelial corneal decompensation. Recovery from cataract extraction alone is much more rapid, and the patient is spared the lifelong problems associated with a corneal homograft. The patient and surgeon must have a frank discussion about the markedly increased chance of corneal decompensation postoperatively from the underlying corneal dystrophy to prevent later misunderstanding.

Conversely, if endothelial decompensation is inevitable after atraumatic cataract extraction, proceeding immediately to a combined procedure is warranted. Assessment of the endothelial reserve in a patient with significant guttate change is an inexact science at best. In taking the patient's history, the surgeon must be particularly alert to symptoms of early morning blur. Edema after lid closure throughout the night is often the first sign of frank decompensation. Slit-lamp biomicroscopic visualization of endothelial stria or microcystic edema is definitive evidence of early decompensation. Subtle microcystic edema can be particularly difficult to visualize in the presence of dense central guttae. Application of fluorescein will help demonstrate early microcystic epithelial changes.

Two special tests can be employed. Specular microscopy is often used in these circumstances, but it can be misleading. First, corneal endothelial decompensation occurs over a wide range of endothelial cell densities because endothelial pump function depends not only on the number of cells, but also on the number of pump sites per cell and the integrity of the cell membrane junctions, neither of which is assessed by specular microscopy. Second, in guttate dystrophy, interpretation of specular microscopy is impeded by masking of the endothelial cells that occurs because of the guttae. Corneal guttae appear dark on specular microscopy and prevent visualization of endothelium that may be covering the back of the excrescences of the Descemet's membrane. It has not been established whether endothelial cell density in the clearer corneal periphery can predict the status of the central endothelium.

The only readily available objective measure of physiologic endothelial pump function is pachymetry, either optical or ultrasonic. Normal corneas have a bell-shaped distribution of thickness and occasionally exceed 600μm in thickness. As a general rule, pachymetry readings less than 600μm indicate an adequately functioning endothelium for most patients, although a disparity between the same areas of the patient's two corneas exceeding 20μm would raise suspicion of early edema in the thicker cornea. Pachymetry readings exceeding 650μm strongly suggest the onset of physiologic endothelial decompensation, making combined penetrating keratoplasty and cataract extraction advisable even in the absence of frank corneal edema. Table 23-1 outlines the diagnostic steps in evaluating corneal endothelial function.

Table 23-1 -- Evaluation of corneal endothelial function

Morphologic evaluation

		Specular microscopy
		Confocal microscopy (research)

Physiologic function

Corneal thickness

		Ultrasonic pachymetry
		Light pachymetry

Evaluation of the diurnal curve (research) or recovery after patching (research)

Fluorophotometry

History

		Morning blur
		Glare complaints
		Symptoms of variable contrast sensitivity impairment

Copyright © 2010 Elsevier Inc. All rights reserved. Read our Terms and Conditions of Use and our Privacy Policy.
For problems or suggestions concerning this service, please contact: online.help@elsevier.com

Combined cataract removal and lamellar posterior endothelial transplantation (DSEK, DSAEK, DLEK, and DMEK)

Lamellar transplantation of donor corneal endothelium is performed with several related techniques, most commonly descemet-stripping endothelial keratoplasty (DSEK) and descemet-stripping automated endothelial keratoplasty (DSAEK), but also including deep lamellar endothelial keratoplasty (DLEK) and descemet membrane endothelial keratoplasty (DMEK) techniques).

Indications

When the corneal endothelium is judged to have already failed, or to not be able to withstand even meticulous phacoemulsification cataract surgery, the surgeon has the option of combining cataract surgery with posterior endothelial transplantation under favorable circumstances. The key requirements are:

	1.	a clear cornea with good optical potential other than edema (e.g. no permanent scarring or irregularity)
	2.	a sufficiently low level of edema so that the surgeon can adequately visualize the lens to perform capsulorrhexis, nuclear phacoemulsification, cortical aspiration, and IOL placement into an intact capsular bag.

Technique

Standard phacoemulsification cataract surgery is performed with the following special considerations:

	1.	The incision sizes and locations need to be compatible with both the surgeon's phacoemulsification technique and the lamellar endothelial transplant technique. For example, if the surgeon uses a 5mm scleral incision for DSEK and typically locates that incision superiorly, but strongly prefers a temporal location for phacoemulsification, usually with a clear cornea incision, then the best choice might be a temporal scleral tunnel for the combined surgery.
	2.	Use of a capsular dye such as trypan blue will facilitate visualization of the capsule through the hazy cornea. However, because the abnormal endothelium will uptake the dye as well, the surgeon should use a bolus of a highly cohesive ophthalmic viscosurgical device (OVD) (typically Healon 5 (AMO)) to fill the anterior chamber. The dye is then injected under the OVD and swept across the lens capsule, avoiding excess dye that would move anteriorly toward the backside of the cornea.

Special techniques for combined full-thickness penetrating keratoplasty and cataract extraction

Preoperative preparation

Obtaining a soft eye is critical to the success of an “open-sky” procedure. In addition to the administration of the usual dilating and antibiotic regimen employed for cataract surgery, softening of the globe and orbit begins with application of gentle pressure over the closed eyelids after administration of the peribulbar or retrobulbar block. An instrument such as the Honan balloon at 30mm Hg should be applied for at least 20 min before beginning the procedure. Intravenous mannitol is administered over 1–2 min at the time of preparing and draping the patient. The dose should be adjusted according to the patient's body weight and medical status, taking particular care to avoid the patient with potential congestive heart failure. A typical dose for most adults is 50mL of 25% mannitol. When administered at this time interval, the maximal hyperosmotic effect will occur at the time of opening the eye, in about 10–15 min. If the mannitol is administered earlier, the maximal pressure-lowering effect is sometimes lost.

Technique for cataract removal

Some surgeons employ a phacoemulsification technique through a scleral tunnel limbal wound before the transplantation.^[11] This has the advantage of the control inherent in a closed-chamber technique. It does require a separate wound and incurs the cost of the phacoemulsification tubing and tip. In many cases warranting a combined procedure, the corneal pathologic condition will impair the clear visualization necessary for phacoemulsification. In particular, visualization of the posterior capsule can be difficult.

Although open-sky extracapsular cataract extraction can be used routinely in conjunction with penetrating keratoplasty, the surgeon must be constantly aware of the risk of an open-sky procedure without protection against an expulsive suprachoroidal hemorrhage. Management of this potential complication is discussed later in the section on complications. An open-sky extracapsular extraction begins with the anterior capsulotomy. Manual retraction of the iris with an iris hook is often necessary because of an associated pathologic condition preventing wide dilation. A can-opener capsulotomy is usually satisfactory, as is a scissors capsulotomy. However, continuous curvilinear capsulorrhexis is ideal in terms of retaining a defined anterior capsular edge, facilitating cortical aspiration, and reliably implanting the IOL within the capsular bag. Obtaining an adequately sized anterior capsulotomy is critical to delivering the entire nucleus. In general, a diameter of 7mm or larger is needed. Control of a capsulorrhexis tear at this diameter can be difficult. Because of the open-sky wound, some degree of positive pressure is inevitable. The posterior pressure on the nucleus tends to cause the capsulorrhexis to extend toward the equator. In addition to the critical decompression of the eye preoperatively (described earlier), positive pressure can be counteracted by using a spatula in the nondominant hand to apply posterior pressure on the center of the nucleus while the capsulorrhexis is being performed (Figure 23-1). If the tear begins to extend beyond 8mm and cannot be recovered, it is best to discontinue the tearing maneuver and convert to a scissors capsulotomy to prevent further extension of the tear out to the equator and beyond.



Figure 23-1 A, In the setting of penetrating keratoplasty, vitreous pressure is particularly likely to cause a circular tear capsulotomy to extend toward the equator and potentially around to the posterior capsule. B, In addition to preoperative maneuvers to soften the globe and to dehydrate the vitreous fluid, positive pressure intraoperatively can be counteracted by applying downward pressure on the nucleus itself while completing the circular tear anterior capsulotomy.

The nucleus can be removed through several maneuvers. If the anterior capsular tear is continuous, hydrodissection can be safely employed. Hydrodissection is helpful in loosening the nucleus. If a fluid stream is directed under the anterior capsule, cortical cleaving hydrodissection may occur, greatly facilitating the later cortical cleanup (see Chapter 16). In the absence of hydrodissection, the nucleus can usually be loosened readily by rocking it with an impaled sharp instrument such as a 23-gauge hypodermic needle or the end of a fine dialysis spatula (Figure 23-2). When one edge of the nuclear equator can be visualized, a microsurgical loop is passed under the nucleus, and the nucleus is delivered though the center of the anterior capsulotomy. If the nucleus tends to fall back, very gentle placement of a small volume of viscoelastic agent behind the lens nucleus can lift it forward. Care must be taken not to create pressure posteriorly that would extend a capsular tear. Another alternative for delivering the lens nucleus is to place a cryoprobe on the central nucleus after removing as much loose anterior cortex as possible. If good adhesion is obtained, the nucleus is delivered in a “lollipop” maneuver.



Figure 23-2 A, First step in delivering the nucleus is to rock the nucleus with an instrument such as a cyclodialysis spatula until one pole of the equator presents. Positive vitreous pressure usually facilitates this step; if the eye is particularly soft, gentle pressure on the sclera to create positive vitreous pressure can be helpful. B, Nucleus is tilted once the equatorial pole becomes exposed. C, A microsurgical lens loop can then be safely passed behind the nucleus and the nucleus delivered in its entirety.

Residual epinucleus and cortex are then aspirated. A conventional automated irrigation–aspiration unit can be used. In the open-sky situation, however, aspiration of air with resultant variation in pump function is inevitable. The large volumes of infusion fluid typical of automated units can be problematic in an open-sky setting. Furthermore, avoidance of aspiration of anterior capsular flaps and tearing of zonules can be difficult, particularly when there is any posterior pressure.

For these reasons, it is helpful to become comfortable with a manual irrigation–aspiration system such as the Simcoe or McIntyre systems. The so-called reverse Simcoe unit combines the advantages of each concept. An aspirating 3mL syringe is attached to the unit directly. Because the irrigation–aspiration tip is flat and gently curved, it is particularly well suited to aspirating cortex in the presence of positive pressure with apposition of the anterior and posterior capsules (Figure 23-3).



Figure 23-3 A, After nucleus delivery, the vitreous pressure flattens the capsular bag with apposition of the anterior and posterior capsules. B, Cortical clean-up can be performed with a variety of instruments. One device that is particularly well suited to the open-sky situation is the relatively flat and thin “reverse Simcoe” irrigation-aspiration needle. The tip can be gently slid between the anterior and posterior capsules, and then slight downward pressure separates the anterior and posterior capsules, allowing the equatorial cortex to be engaged and stripped safely.

Great care must be taken to avoid aspiration of the anterior capsule and tearing of zonules in the open-sky situation. All cortex must be cleaned to minimize postoperative inflammation that will be injurious to corneal transplantation.

After full removal of cortex, and polishing of the posterior capsule if needed, a posterior chamber IOL is placed. When placement within the capsular bag is ensured in an intact capsulorrhexis, my personal preference is a one-piece all-polymethylmethacrylate posterior chamber IOL with a haptic diameter of 12mm. When sulcus fixation is possible or probable, a 13–14mm haptic diameter is preferred to better ensure stability in the sulcus. A patient with a normal pupil can accept a 6mm-diameter optic; if there is any pupillary abnormality, a 6.5 or 7mm-diameter optic without any positioning holes is used.

The selection of an IOL power is problematic.^{[4,][5,][12,][13]} Axial length can be measured preoperatively, but penetrating keratoplasty will affect the keratometric contribution to the total optics. Some surgeons employ the patient's preoperative keratometry values to calculate IOL power. My personal preference is to use my “typical” value for corneal curvature after keratoplasty, which averages 45 diopters (D) for all patients. Each surgeon must determine his or her postoperative “personalized” keratometric value after corneal grafting. If a consistent surgical technique is employed, a keratoplasty surgeon will usually obtain repeatable results. Only occasionally will the postoperative power be sufficiently inaccurate that the anisometropia becomes symptomatic.

Complications

Positive pressure and vitreous loss

Positive pressure in the form of a bulging posterior capsule, but with maintenance of a normal red reflex, can be due to a variety of causes. The most common cause is transmitted lid and drape pressure through the lid speculum. To maximize the ability to resist such pressure on the open globe, a Schott or Smirmaul lid speculum provides excellent exposure while controlling pressure transmission to the eye. Wire lid specula are the most likely to transmit pressure to the globe. Whatever lid speculum is used in the presence of positive pressure, the surgeon must immediately check the lid speculum. Countersupport is provided if lifting or repositioning a lid speculum relieves the positive pressure.

If the positive pressure is extreme and threatens rupture of the posterior capsule or zonules, or both, the surgeon can attempt vitreous aspiration. With the open eye, however, a simple needle stab through the pars plana will generate even more positive pressure and ensure vitreous loss. Only an extremely delicate cutdown through the sclera with a sharp knife, such as a diamond knife, can minimize this risk. In many cases, the rapid progression of the positive pressure will not give the surgeon adequate time for this type of dissection.

The surgeon must always be alert for evidence of suprachoroidal hemorrhage or effusion. This much more threatening complication is discussed further on. Without signs of this additional complication, vitreous loss must be definitively addressed with vitrectomy. Automated mechanical vitrectomy with a guillotine-type cutter is preferred to minimize traction on the vitreous base. If a mechanical vitrectomy is not possible, an open-sky vitrectomy with cellulose sponge and scissors can be performed, taking care to minimize vitreous traction. At the completion of the vitrectomy, the anterior chamber must be carefully inspected, including wiping the pupillary aperture and iris face with a cellulose sponge to ensure removal of all vitreous. Residual vitreous in the anterior chamber will tend to become incarcerated in the keratoplasty wound, distorting the pupil, at a minimum, and often leading to further complications, such as cystoid macular edema.

Suprachoroidal hemorrhage and effusion

With the corneal button removed, the eye is vulnerable to devastating suprachoroidal effusion and hemorrhage. The surgeon must always be alert to this possible complication and be prepared to deal with it immediately. Signs of suprachoroidal hemorrhage and effusion in an open-sky setting include positive pressure on an intact posterior capsule, rupture of the posterior capsule and zonules with vitreous loss, alteration in the red reflex, or a combination of these factors. If the patient is aphakic before the placement of the IOL, the retina may be directly visualized in detail through the operating microscope. An advancing smooth “roll” of elevated retina or normal color may represent effusion; if the advancing elevation is dark, suprachoroidal hemorrhage is likely. A slow hemorrhage is likely to lead to the expulsion of the intraocular contents if immediate action is not taken.

As soon as the suprachoroidal mass is recognized, the surgeon should immediately place a gloved index finger over the corneal opening. It is an excellent idea to have a clear lens available to maintain the globe when a suprachoroidal event is recognized. One such lens is the Cobo temporary keratoprosthesis, available from Ocular Instruments (Figure 23-4). This tapered lens can fit a wide range of trephine openings. This will stabilize the globe while the surgeon proceeds to a cutdown into the suprachoroidal space to remove the pressure.



Figure 23-4 Cobo temporary keratoprosthesis (Ocular Instruments, Inc.) is highly valuable in controlling suprachoroidal effusion or hemorrhage in the vulnerable open-sky setting. (Courtesy Ocular Instruments, Inc., Bellevue, Wash.)

One of the causes of suprachoroidal hemorrhage during penetrating keratoplasty is a lightly anesthetized patient under general anesthesia straining against the endotracheal tube. Because penetrating keratoplasty is relatively painless, little general anesthesia is needed, and many anesthesiologists progressively reduce the amount of general anesthetic during the procedure to avoid hypotension. To avoid this complication, the anesthesiologist should be specifically instructed by the surgeon to use a paralytic agent.

Intraocular lens implantation after vitreous loss

If vitreous loss has occurred, and the ability of the residual posterior capsule to support a posterior chamber IOL is in doubt, the surgeon faces three choices for IOL implantation: an anterior chamber IOL, an iris-sutured posterior chamber IOL, or a scleral suture-fixed posterior chamber IOL.

The literature does not show a clear-cut difference in outcomes among these three alternatives. If a posterior chamber IOL is desired, dissection of scleral flaps for scleral fixation is extremely difficult once the corneal button is absent. The surgeon can iris-fixate a posterior chamber IOL with midperipheral sutures (commonly referred to as “McCannel suture fixation”) or, with a technique first described by Lane, use a scleral cutting technique that does not require dissecting scleral flaps. The latter can be performed using a posterior chamber IOL with a suturing hole in the haptic. A loop of permanent suture such as 10-0 or 9-0 polypropylene is passed through the positioning hole, and then each arm of the double-arm suture is passed through the sclera approximately 1mm apart through the ciliary sulcus region. The suture is tied and cut. The knot is then rotated beneath the sclera. Conjunctiva is closed over the smooth loop of polypropylene. The smooth loop of external suture material will not erode through the conjunctiva. This technique is illustrated for a closed-chamber procedure in Figure 41-1.

References

[1]. Lindstrom R.L., Harris W.S., Doughman D.J.: Combined penetrating keratoplasty, extracapsular cataract extraction, and posterior chamber intraocular lens implantation. J Am Intraocul Implant Soc 1981; 7:130-132.

[2]. Hunkeler J.D., Hyde L.L.: The triple procedure: combined penetrating keratoplasty, extracapsular cataract extraction, and posterior chamber intraocular lens implantation: an expanded experience. J Am Intraocul Implant Soc 1983; 9:20-24.

[3]. Kramer S.G.: Penetrating keratoplasty combined with extracapsular cataract extraction. Am J Ophthalmol 1985; 100:129-133.

[4]. Binder P.S.: The triple procedure: refractive results. 1985 Update. Ophthalmology 1986; 93:1482-1488.

[5]. Crawford G.J., Stulting R.D., Waring G.O., et al: The triple procedure: analysis of outcome, refraction, and intraocular lens calculation. Ophthalmology 1986; 93:817-824.

[6]. Busin M., Arffa R.C., McDonald M.B., et al: Combined penetrating keratoplasty, extracapsular cataract extraction, and posterior chamber intraocular lens implantation. Ophthalmic Surg 1987; 18:272-275.

[7]. Meyer R.F., Musch D.C.: Assessment of success and complications of triple procedure surgery. Am J Ophthalmol 1987; 104:233-240.

[8]. Fine M.: Therapeutic keratoplasty and Fuchs' dystrophy. Am J Ophthalmol 1964; 57:371-378.

[9]. Payant J.A., Gordon L.W., VanderZwaag R., et al: Cataract formation following corneal transplantation in eyes with Fuchs' endothelial dystrophy. Cornea 1990; 9:286-289.

[10]. Martin T.P., Reed J.W., Legault C., et al: Cataract formation and cataract extraction and penetrating keratoplasty. Ophthalmology 1984; 101:113-119.

[11]. Malbran E.S., Malbran E., Buonsanti J., et al: Closed-system phacoemulsification and posterior chamber implant combined with penetrating keratoplasty. Ophthalmic Surg 1993; 24:403-406.

[12]. Binder P.S.: Intraocular lens implantation after penetrating keratoplasty. Refractive Corneal Surg 1989; 5:224-230.

[13]. Flowers C.W., McLeod S.D., McDonnell P.J., et al: Evaluation of intraocular lens power calculation formulas in the triple procedure. J Cataract Refract Surg 1996; 22:116-122.

Page

Contents

If you find an error or have any questions, please email us at admin@doctorlib.org. Thank you!