Phacoemulsification in the setting of corneal endotheliopathies: A review

Abstract

With the evolution of endothelial keratoplasty, surgical approaches in patient with cataracts and coexisting corneal endotheliopathies have also changed. This article aims to review the factors that determine proper procedure selection, preoperative planning, and surgical modifications during phacoemulsification in order to optimize visual outcomes and avoid surgical pitfalls. The selection of either simultaneous cataract surgery and keratoplasty or staged procedures depends on the patient’s history and clinical exam, desired refractive outcomes, the surgeon’s expertise, and individual preferences.

Introduction

More than 25 million Americans suffer from cataracts¹; and based on Medicare statistics, over three million cataract surgeries are performed annually in the United States (U.S.).² The rate of cataract surgery (i.e. number of surgeries per million population per year) continues to increase steadily due to the growing demand of an aging population combined with reduced visual impairment thresholds permitted by technological advances.³ Accordingly, ophthalmologists are increasingly opting to perform cataract surgeries on more complex patients, such as those with pre-existing ocular conditions.⁴ Pathologies which affect endothelial cell function are among the most common ocular comorbidities.⁵ Even in the age of modern day phacoemulsification, pre-existing endothelial dysfunction can be a source of frustration for both the surgeon and patient, potentially increasing the risk of intraoperative complications and impacting final postoperative visual acuity due to cornea decompensation.⁶

Although cataract surgery alone is a less time-consuming procedure and may allow for a more rapid recovery with fewer postoperative visits⁷, the risk of corneal decompensation and need for future keratoplasty needs to be carefully considered. In healthy eyes, phacoemulsification decreases endothelial cell density by 1.8% to 15%.⁸ Endothelial cell loss in an already compromised cornea can lead to further decompensation; the risk of persistent postoperative edema may be four times higher in a patient with endothelial dysfunction compared to a patient without previously identified disease.⁶ In these scenarios, the decision to proceed with concurrent endothelial keratoplasty (EK) and cataract extraction with intraocular lens (IOL) implantation (the so-called “new triple procedure”)⁹, staged procedures, or cataract surgery alone can be challenging.

Although it is difficult to predict which corneas may decompensate or result in unsatisfactory vision after phacoemulsification, several risk factors have been proposed: 1) obvious cornea edema or bullae, increased corneal thickness (>650μm), or confluent guttae by slit-lamp examination, 2) complaints of blurred vision and glare, worse in the morning that improves throughout the day, and/or 3) low central endothelial cell counts by specular microscopy (<1000 cells/mm²).^10,11 Although, the triple procedure is effective and offers the advantage of one surgery^12,13, the possibility of higher complication rates in a combined procedure should be considered.^14,15 The surgeon must take into account the clinical exam findings along with the patient’s visual needs and expectations in deciding the best approach. Ultimately, both the surgeon and patient should be mutually satisfied with the selected surgical plan; therefore, meticulous preoperative counseling and perioperative planning are essential in helping patients make informed decisions, set appropriate visual expectations, and optimize visual outcomes.

In this review, we discuss the considerations in performing phacoemulsification in patients with cataracts and coexisting corneal endotheliopathies.

Goals of surgery

In patients with coexisting cataracts and endothelial dysfunction, the surgeon aims to decrease or eliminate visual impairment while minimizing endothelial cell damage, which may be achieved with or without EK.

Phacoemulsification alone may be selected if there is mild endothelial compromise, if the patient is not sufficiently healthy to tolerate a prolonged procedure, or per patient’s preference. Conversely, if the cornea edema is severe enough to impede the view of the anterior chamber, EK may need to be performed first to safely permit cataract surgery after the cornea clears. In cases of planned staged procedures, some advocate that EK be performed first in order to optimize refractive outcomes.¹²

Etiologies of corneal endotheliopathies

Endothelial dysfunction may be caused by a variety of etiologies. It may or may not be progressive, and can affect the central visual axis or be limited to the corneal periphery without significant visual consequence.¹⁰ Recurrent epithelial breakdown and the development of stromal scarring as a result of chronic edema may cause pain, corneal neovascularization, and further visual deterioration. Endothelial dysfunction not only affects patients’ vision, but also the surgeon’s view of the anterior chamber due to increased light scatter.¹⁶

Causes of endothelial dysfunction that may coexist with cataracts include Fuchs’ endothelial corneal dystrophy (FECD), posterior polymorphous corneal dystrophy (PPCD), iridocorneal endothelial (ICE) syndrome, trauma induced endothelial dysfunction, infectious endotheliitis (disciform keratitis), and refractory glaucoma.

Fuchs endothelial cornea dystrophy (FECD)

FECD is the most common primary corneal endotheliopathy and the main indication for cornea transplantation in the U.S.¹⁷ Both hereditary and environmental factors play a role in its pathophysiology. Its prevalence varies from 3.8% to 11% in patients older than 40 years.^18,19 FECD is characterized by a slowly progressive, bilateral decline in endothelial cell density, polymegathism and polymorphism of the residual endothelial cells, and a thickened Descemet membrane (DM) with the formation of guttae.

Visual acuity and function may not necessarily correlate in afflicted patients. Complaints of disabling glare and decreased contrast sensitivity, particularly in ambient lighting are common. Even mild cornea guttae and edema can cause higher order aberrations, resulting in visual distortion. These symptoms can be difficult to distinguish from those caused by cataracts.¹⁶

Posterior polymorphous corneal dystrophy (PPCD)

PPCD is an autosomal dominant, non-progressive condition of DM characterized by metaplastic endothelial cells that appear and behave like epithelial cells. On clinical examination, one may note coalesced cornea vesicles, gray geographic areas, and broad band-like posterior corneal lesions with scalloped edges.²⁰ Although typically bilateral, sporadic cases may be unilateral or present asymmetrically.²¹ In addition, PPCD has been associated with abnormally steep corneal curvatures.²² Patients are usually asymptomatic, but may develop visual compromise due to stroma edema, correctopia, iridocorneal adhesions, and glaucoma.

Iridocorneal endothelial syndrome (ICE)

ICE is a rare, non-familial, progressive disorder characterized by endothelial cells that take on epithelioid-like characteristics. Patients can present with corneal edema, peripheral anterior synechiae, iris anomalies, and secondary glaucoma (Figure 1).²³ In contrast to PPCD, ICE is a unilateral disease that predominantly afflicts middle-aged women.²³ Although it is primarily thought of as an endothelial disease, it comprises of three clinical variants: Chandler syndrome, iris nevus (Cogan-Reese) syndrome, and progressive (essential) iris atrophy.²⁴ In its most common presentation, Chandler syndrome, the corneal signs predominate, and patients’ corneas can take on a characteristic hammered silver appearance on slit lamp biomicroscopy. The etiology of ICE is unclear, although the human herpes virus (HHV) has been detected in the aqueous humor and cornea tissues of affected patients.^25,26

Figure 1.

Slit lamp photo of a patient with iridocorneal endothelial syndrome, demonstrating corectopia. Gonioscopy reveals peripheral anterior synechiae.

Viral endotheliitis

Primary endotheliitis is thought to be viral in origin, and the herpes simplex virus (HSV), varicella zoster virus (VZV), cytomegalovirus (CMV), and the mumps virus have all been implicated in its pathogenesis. On clinical exam, there is often a mild iridocyclitis, keratic precipitates (KP), and cornea edema (Figure 2). Corneal endotheliitis is classified into linear, sectorial, disciform, and diffuse forms based on the distribution of the KP and overlying corneal edema.²⁷ In herpetic related corneal endotheliitis, elevated intraocular pressures (IOP) secondary to a trabeculitis may be detected. Affected patients can develop cataracts and irreversible endothelial decompensation, requiring surgical intervention.

Figure 2.

Patient with active herpes simplex virus disciform keratitis with corneal edema. Localized edema and corneal neovascularization are visible in the inferonasal quadrant.

Trauma

Past blunt or penetrating ocular injury, rupture of DM from forceps injury, or chemical injury can result in endothelial damage and/or cataract formation. Primary trauma and previous ocular surgery may also lead to epithelial ingrowth, which can form a sheet covering the endothelial cells, leading to opacification, corneal edema, and irreversible scarring.²⁸

Indications for surgery

The decision to surgically intervene in these patients is dependent on the degree of visual and functional impairment, presence of ocular discomfort, best corrected visual acuity (BCVA), and visual potential. The patient’s desire to improve their vision is usually the predominant motivation to pursue surgery.

It can be difficult in some cases to determine if the cataract or the corneal disease is the main contributor to a patient’s visual complaints. A thorough history determines the chronicity of visual decline. In the setting of recent visual loss and the presence of stable and mild endothelial disease, the cataract is likely the main culprit.²⁹ If the patient endorses diurnal variations in vision or there is significant corneal edema without lenticular clouding, the corneal disease is likely playing a more significant role. After a detailed clinical examination, the ophthalmologist decides whether to proceed with a staged procedure (cataract surgery followed by EK, or EK and then cataract surgery), a triple procedure, or cataract surgery alone. In patients with mild cornea disease, in which only phacoemulsification is planned, a three month wait is typically recommended before considering keratoplasty.¹¹ If the view to the anterior chamber is impeded due to cornea edema, then it may be necessary to perform EK first to permit adequate visualization for cataract surgery to be performed later.

Contraindications to surgery

The risks of surgery may not outweigh the benefits in patient with established poor visual potential as determined by clinical history (such as severe amblyopia, end-stage glaucoma, macular scar, optic nerve abnormalities) and visual function testing (i.e. potential acuity meter). In cases with severe media opacity due to corneal or lens pathology, an ultrasound evaluation may be necessary to rule out ocular co-morbidities that may limit visual potential.

Selection of procedure

With the advancement of posterior lamellar keratoplasty over the last thirty years, surgeons are now able to replace the diseased corneal endothelium with donor tissue through small incisions, largely supplanting the need for penetrating keratoplasty (PK) in these cases. The newest technique known as Descemet membrane endothelial keratoplasty (DMEK), uses a 10–15μm donor scaffold (Figure 3A). DMEK is being increasingly adopted by cornea surgeons due to better visual outcomes, faster visual recovery, and lower risk of immunological rejection compared to Descemet stripping automated endothelial keratoplasty (DSAEK).³⁰ However, DSAEK still remains the most popular type of EK performed and is considered the procedure of choice for eyes with more complicated anatomy, such as shallow anterior chambers, prior glaucoma or retina surgeries, severe cornea edema, and peripheral anterior synechiae. Ultrathin-DSAEK (UT-DSAEK), which uses a donor graft of less than 100μm (Figure 3B), has been shown to have superior visual outcomes compared to DSAEK. ^31,32 In turn, DMEK yielded superior visual acuity outcomes compared to UT-DSAEK in a randomized controlled trial.³³ However, studies also suggest DMEK is technically more demanding with a steeper learning curve, and is associated with higher rates of donor graft detachments (up to 62%)^34–36 and iatrogenic primary graft failures (3% to 8%)³⁷.

Figure 3.

Anterior segment ocular coherence tomography

A: Descemet membrane endothelial keratoplasty

B. Ultra-thin Descemet stripping automated endothelial keratoplasty

Although studies show that the triple procedure is safe and effective³⁸, questions still linger regarding graft dislocation rates due to the usage of viscoelastic³⁹, refractive outcomes, increased incidence of CME, stability of the IOL, and potential increase in vitreous pressure that may complicate graft insertion and unfolding. However, in a prospective case series, Terry et al. evaluated two hundred and twenty-five eyes who underwent DSAEK with cataract surgery, and saw no increase in graft dislocation or primary graft failure rates compared to a smaller cohort of DSAEK alone.⁹ In contrast, another retrospective study found a significantly higher rate of graft dislocation (6-fold) with the triple procedure, though final visual acuity and endothelial cells counts were comparable.¹⁴ In 2014, Price at al. compared DMEK triple versus DMEK alone, and found that the former did not result in increased risk of complications and was associated with rapid visual recovery.^13,40 Of note, in patients with ICE or PPMD, the central anterior chamber (AC) depth can be significantly less compared to that of normal patients due to peripheral anterior synechiae.⁴¹ In cases with restricted anterior chambers, cataract surgery should be performed first or in conjunction with EK to allow for adequate AC space to facilitate cornea graft positioning.

In 2017, the Price Vision group reversed their previous recommendation of performing simultaneous EK and cataract surgery in patients who require both, and advocated instead for staged surgeries.¹² They argued cornea edema should be treated first with EK in order to optimize refractive outcomes. Inaccurate keratometry readings and axial length (AL) measurements, varied postoperative hyperopic shift, and astigmatic changes secondary to corneal incisions may affect final refractive outcomes.¹² Cataract surgery can then be performed once the cornea clears, targeting the best possible uncorrected vision. Although, care must be taken to avoid damage to the cornea graft during phacoemulsification. In patients over 50 years, cataract surgery will likely be needed within three years of EK.⁴²

More recently, Descemet stripping only (DSO) combined with cataract surgery has been described with or without the aid of pharmacological endothelial stimulation (rho-associated kinase inhibitor) in suitable patients with FECD.^43,44 This procedure involves deliberate removal of a 4mm zone of central DM without placement of a corneal transplant. The ideal patient for DSO is still being debated, but it is usually reserved for select patients with guttae limited to the central cornea and good peripheral endothelial reserve (endothelial cell counts greater than 1,000cells/mm²).³⁶

The surgeon must weigh the pros and cons of each approach, and in discussion with the patient, decide on the most appropriate course of action on a case-to-case basis. Other important considerations such as ocular co-morbidities and factors limiting the patient’s ability to cooperate intraoperatively or to lie supine after surgery may impact the final decision.

Preoperative assessment

History

A thorough history should be taken to determine the chronicity and severity of visual impairment. As with routine cataract surgery, a list of the patient’s visual needs and activities must be documented to help make the decision for surgery and to plan for the refractive target. The surgeon should also inquire about laterality, glare, contrast sensitivity, visual distortion, and eye pain. Parameters obtained should be tailored to each individual’s presentation.

A detailed medical history should be gathered, including a list of medications. For instance, α_1A-antagonist medications prescribed for the treatment of benign prostatic hypertrophy can complicate both cataract surgery and EK due to its association with intraoperative floppy iris syndrome (IFIS), ^45–47 which may affect the choice of surgical approach.⁴⁸ In this condition, the iris can billow, plugging the wound and shallowing the anterior chamber, complicating cornea graft insertion. A suture-drag technique with DSAEK has been described to overcome these difficulties and minimize donor endothelial damage.⁴⁵ Routine use of anticoagulant or antiplatelet is not routinely stopped prior to surgery.^15,49 Certain medical conditions such as a head tremor, severe kyphosis, or other musculoskeletal issues may preclude a patient from being able to lie comfortably flat, decreasing the chance of success after EK. On questioning, patients may relate that a family member had a cornea disease or required corneal transplantation, which may shed light on their current diagnosis. Ocular history is critical in determining visual prognosis and allows the surgeon and patient to make informed surgical decisions. Other important information to gather include the presence of preoperative glaucoma (a superior conjunctiva sparing procedure is recommended), uveitis, amblyopia, history of retina disease, and past refractive surgery.

Visual function

On initial evaluation, the surgeon should recognize that the impact of cornea edema on visual acuity, even in the presence of a cataract, may be underestimated on the standard Snellen chart.¹⁰ Visual acuity should be tested under standard lighting conditions with and without correction. Glare testing, pinhole testing, and manifest refraction should also be performed. Potential acuity meter and laser interferometry are two methods to determine visual potential by projecting an image directly onto the macula and bypassing anterior segment disease (i.e. cataracts and cornea opacities).⁵⁰ A pinhole vision using an illuminated near card in a dark room can also be employed, but may overestimate potential acuity.⁵¹

Exam

A comprehensive ocular exam should be performed using standard slit-lamp biomicroscopy, which is the most effective way to visualize the status of the crystalline lens and cornea. A thin slit beam can be used to detect if the central cornea is thicker than the periphery, which is an indicator of cornea edema. DM folds or tears, endothelial haze, corneal scarring, vesicles, clusters or lines of KP, peripheral anterior synechiae, correctopia, and endothelial guttata may be detected using a variety of biomicroscopy techniques such as diffuse illumination, specular reflection, sclerotic scatter, and retro-illumination.¹⁰

Preoperative measurements

Techniques to measure corneal thickness continue to evolve. Ultrasonic pachymeters (10–20Mhz)¹⁰ is widely accepted as the method of choice in the measurement of central corneal thickness (CCT) due to convenience and reliability. The range of tissue penetration is limited between 200 to 1000μm.¹⁰ However, newer technologies such as anterior segment optical coherence tomography (AS-OCT) and Scheimpflug imaging may provide better accuracy.⁵² AS-OCT can also be used to visualize synechiae, iris abnormalities, and measure the anterior chamber depth in cases in which cornea edema precludes adequate examination.

Recent generations of specular microscopy (SM) are non-contact and provide important information about the density of endothelial cells (cells/mm2) and the morphology of the cell population. SM can be used to diagnose endothelial diseases through computer-assisted analysis of the size, shape, and density of cells per square millimeter. Corneal guttae may appear as darkened areas.⁵² In PPMD, characteristic discrete islands of abnormal endothelial cells, grouped vesicles, and broad bands representing abnormal DM can be seen.⁵³ In ICE patients, SM shows a typical dark-light reverse pattern (ICE cells appear dark with a light central spot)^53,54, but cannot accurately predict clinical prognosis.⁵⁵ Of note, specular microscopy is not particularly useful in monitoring patients with cornea edema nor determining endothelial functional reserve, especially in the presence of diffuse guttae.¹⁰ Corneal pachymetry has been proposed as a more useful marker of endothelial function. Older studies have recommended a preoperative pachymetry cutoff of 640μm to determine if the patient will benefit from a triple procedure or eventually require cornea transplantation after cataract surgery.⁵⁶ In a 2013 study comparing two phacotechniques (torsional vs. longitudinal) in patients with FECD, Doors et al. determined that a preoperative CCT of more than 620 µm was associated with an increased risk of postoperative corneal decompensation requiring DSAEK six months after cataract surgery.⁵⁷ Additionally, for each 10µm increase in preoperative CCT, the odds of developing corneal decompensation increased 1.7 times.⁵⁷

However, as previously discussed, EK techniques have become increasingly refined, and the visual threshold to pursue sequential or concomitant corneal transplantation in combination with cataract surgery has been significantly lowered. Additionally, it is now recognized that the CCT of normal eyes can vary widely, with a small percentage measuring above 640μm.⁵⁸

Scheimpflug-based devices can be used to determine corneal densitometry (a measurement of light scatter), which in turn, can be used to predict endothelial cell behavior after cataract surgery. Ishikawa et al. published a series in which a positive correlation was detected between densitometry readings and postoperative corneal thicknesses.⁵⁹

Accurate biometry and corneal topography measurements is a major challenge in patients with coexisting cornea disease and cataracts. Due to poor vision, patients may find it difficult to focus on the target during optical biometry, which can result in errors in AL measurements. This may be minimized using immersion ultrasonography. Scheimpflug-based devices may be best in measuring cornea power in the presence of cornea edema and endothelial abnormalities, but Placido disk-based devices and slit-scanning systems may also be utilized. However, corneal irregularities in the form of bullae or epithelial edema may still result in inaccurate readings. Due to these inaccuracies, some advocate using the contralateral eye if the cornea is unaffected for keratometry readings or to perform EK first to better predict IOL power once the cornea edema resolves.¹²

Special considerations

IOL selection

If cornea decompensation is unavoidable, adjustment to the IOL power calculation should be done in anticipation of a hyperopic shift after DSAEK and DMEK (less so) caused by flattening of the corneal curvature and the effect of the donor lenticular shape on the posterior host cornea.⁶⁰ Typically, the average automated keratometry does not change after EK.⁶¹ DSAEK induces a mean hyperopic shift between +0.78D to 1.05D⁶². For UT-DSAEK, Busin reported a hyperopic shift of +0.78± 0.59D.⁶³ Graft size and thickness (ratio of central graft thickness to mean peripheral graft thickness)⁶⁴ have been shown to impact final refractive outcomes after DSAEK. There is a positive correlation between the graft diameter and the amount of hyperopic shift; thus, in grafts greater than 8.5mm, a more myopic target should be considered.⁶⁵ Whereas in DMEK, an almost negligible hyperopic shift of +0.24±1.01D was reported at postoperative year one.⁴⁰ For DSO combined with cataract surgery, Davies et al. reported a hyperopic shift of +0.38D, similar to DMEK, one month after cornea clearance.⁴⁴ The authors recommended a target of −0.5D when calculating the IOL power.⁴⁴ It is generally recommended to target −0.75D to −1.25D for a DSAEK triple and −0.5D to −0.75D for a DMEK triple.^30,38

It is advisable to avoid hydrophilic acrylic IOLs in association with EK due to reports of IOL opacification, hypothesized to be caused by exposure to intracameral gas or air (Figure 4),.^66,67 However, opacification of hydrophobic lenses after uneventful phacoemulsification have also been reported; though both cases spontaneously resolved after a few weeks.⁶⁸ When approaching cataract surgery in patients with endotheliopathies, extensive iris atrophy, and peripheral anterior synechiae, avoid iris fixated and anterior chamber intraocular lenses (ACIOLs).⁶⁹

Figure 4.

An opacified hydrophilic acrylic IOL following pars plana vitrectomy and intravitreal gas injection.

The use of toric IOLs in patients that undergo combined EK and cataract surgery can be successful.⁴⁰ However, presbyopia correcting and multifocal IOLs are generally discouraged in patients with endothelial dysfunction, given that these patients already have aberrated corneas and the efficacy of these lenses is dependent on achieving emmetropia.

Femtosecond laser-assisted cataract surgery

The purported advantages of femtosecond laser assisted cataract surgery (FLACS) include lower effective phacoemulsification time and ultrasound energy compared to conventional phacoemulsification, resulting in a reduction in endothelial cell loss.⁷⁰ With the improvement of surgical techniques, whether these advantages translate to lower rates of corneal decompensation in eyes with pre-existing endothelial dysfunction postoperatively remain unproven.^71,72 In 2013, Abell et al. found that pretreatment with the femtosecond laser resulted in significant reductions in effective phacoemulsification time and corneal endothelial cell loss in a prospective, case-control study at postoperative week three, but differences were not detected by month six.⁷⁰ In a subsequent multicenter case-control study, Manning et al. showed FLACS did not result in better visual or refractive outcomes compared to conventional phacoemulsification in normal eyes, and was associated with a higher rate of corneal edema postoperatively.⁷³ In 2008, Zhu et al. performed a retrospective case series looking at two hundred and seven eyes, comparing FLACS to conventional phacoemulsification, and found no difference in the rates of corneal decompensation in eyes with mild to moderate FECD.⁷¹ However, two other studies did demonstrate an advantage of FLACS over standard phacoemulsification in FECD patients in regards to endothelial cell loss, especially in the presence of moderate to hard cataract densities.^72,74

Surgical devices and techniques

Ophthalmic viscoelastic devices

For cataract surgery alone, the use of in-the-bag phaco-chop and soft-shell techniques in patients with endothelial dysfunction have been shown to be advantageous. Arshinoff was the first to introduce the soft-shell technique using both higher-viscosity cohesive and lower-viscosity dispersive ophthalmic devices (OVD) as a bilayer cushion against endothelial damage.⁷⁵ In a cohort of FECD patients that underwent phacoemulsification, the postoperative CCT was found to be significantly less at six months in cases that utilized the soft-shell technique (compared to sodium hyaluronate 1% alone).⁷⁶ In a modification of this technique, another study found that in patients with grade three or higher cataracts and FECD, the use of 2.5% sodium hyaluronate, a viscoadaptive OVD, was comparable to the soft-shell technique in regards to postoperative CCT and corneal endothelial density.⁷⁷

In the triple procedure, only a cohesive OVD should be used, and all OVD must be evacuated prior to graft insertion to decrease the risk of graft detachment and interface haze.³⁹

Endoilluminators and other devices

In the presence of significant cornea haze, anterior chamber illumination with the use of a 25-gauge or 27-gauge fiber-optic illuminator can be used either transsclerally or intracamerally to improve visualization.^78,79 This technique may help facilitate descemetorhexis, capsulorhexis, cataract removal, and IOL placement into the capsular bag.

In cases with extensive synechiae or an irregular pupil as can be seen in patients with PPCD, ICE, and eyes with previous inflammation, nylon pupil hooks or a pupil expansion ring can be employed to allow for adequate visualization of the lens.

Methods of cataract removal

Total phacoemulsification energy usage has been associated with endothelial cell loss.⁸⁰ Thus, surgeons have increasingly developed more sophisticated cataract removal techniques to protect the endothelium. In denser cataracts, advanced methods to mechanically fracture the lens such as the phaco-chop technique compared to more traditional methods (divide and conquer and stop-and chop) appears beneficial in regards to ultrasound time, balanced salt solution usage, cumulative dissipated energy (CDE), and endothelial cell loss.^81,82

However, Park et al. reported that phaco-chop and stop-and-chop resulted in similar rates of endothelial cell loss after phacoemulsification.⁸³ Microinterventional endocapsular nucleus disassembly using a self-expanding nitinol microfilament has been described, but its clinical benefit in regards to patients with endothelial dysfunction is yet to be determined.⁸⁴

In conventional longitudinal ultrasound mode, the phacoemulsification needle moves forward and backward. This longitudinal movement creates a repulsion effect that can push the lens fragment away with each stroke, resulting in decreased efficiency.⁸⁵ Studies demonstrate that the use of an oscillatory handpiece improves CDE and ultrasound time compared to conventional phacoemulsification, and consequently may result in less endothelial cell damage.⁸⁵

Phacoemulsification alone

With an incidence of approximately 0.5%, Descemet membrane detachments (DMD) during phacoemulsification are rare but potentially visually devastating if extensive (Figure 5).⁸⁶ Underlying endothelial disease and shallow anterior chambers have been implicated as predisposing factors for DMD.^87,88 The soft-shell technique described above may be useful in protecting the endothelium during phacoemulsification. However, care must be taken to avoid unintentional injection of OVD between DM and the corneal stroma. Other surgical risk factors include cornea incisions that are too tight or anterior, premature irrigation before the tip of the handpiece clears the inner lip of the wound, and the use of blunt or dull instruments.^87,88

Figure 5.

An extensive Descemet membrane (DM) detachment after phacoemulsification in a patient with Fuchs endothelial corneal dystrophy.

A: A high-resolution ultrasound biomicroscopy showing a severe bullous DM detachment.

B. Slit lamp biomicroscopy showing sectoral corneal edema corresponding to the area of DM detachment.

Modifications after endothelial keratoplasty

If EK has already been performed, care must be taken to avoid dislodging the graft. Price et al. recommended that if a temporal approach is taken during phacoemulsification, that the graft be displaced slightly nasally and care be taken to not oversize the graft diameter.¹²

Modifications for a triple procedure

When performing a triple procedure, cataract surgery should be performed first to avoid damage to the donor tissue. If the pupil is not adequately sized during cataract surgery, nylon iris hooks or a pupil expansion ring can be used to help expand the pupil. Mydriatics should not be added to the irrigating solution. If there is significant epithelial edema, one can use glycerin or debride the epithelium to improve the view. The paracenteses should be short and vertical to avoid overlap with the corneal graft, allowing easier graft manipulation. For better visualization, the side port wound can be marked with gentian violet. If the view is particularly cloudy, ophthalmic dyes such as trypan blue may provide better visualization of the lens capsule and help facilitate DM stripping. Dispersive OVD should not be used, so as to decrease the risk of retained viscoelastic layer between the host and donor that can lead to non-adherence. In fact, some advocate avoiding OVD all together during descemetorhexis and using air in the anterior chamber for visualization, particularly in DMEK.¹² It is critical that a round and continuous capsulorhexis is completed, and preferably between 4.5 to 5.0mm in diameter to ensure stability of the newly placed IOL. Additionally, a miotic such as carbachol 0.01% can be injected to bring the pupil down to prevent the lens from touching the graft. There is a variety of DSAEK graft injectors available, and the surgeon should enlarge the wound to the smallest size possible to minimize the amount of surgically induced astigmatism. Common inserter devices for DMEK can fit easily through a 2.4 to 2.8mm incision.

Conclusion

The approach of phacoemulsification in patients with endothelial dysfunction can be challenging. Thorough preoperative counseling and surgical planning is paramount in helping patients make informed decisions and to ensure optimal postoperative outcomes. If the surgeon feels that cornea decompensation is unavoidable after cataract surgery, a triple procedure can be considered. However, performing endothelial keratoplasty first may allow for more predictable refractive outcomes. DMEK, the most recent iteration of endothelial keratoplasty, has yielded excellent visual results and has been proven to be safe with a low rate of complications. Adjustments in cataract surgical techniques may be necessary in patients with endothelial dysfunction.