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Cataract Surgery and Anterior Segment Challenges

2 CPD in Australia | 0.5 CD + 0.5G in New Zealand | 1 October 2018

By Dr. Alex Ioannidis

Patients with cataracts present to us with a wide range of ophthalmic and systemic comorbidities and the challenge is to achieve the best possible outcome. There are some particularly complex cases that we need to consider and plan accordingly in the pre, peri, and post-operative periods. This article describes the most common anterior segment challenges that we need to consider. 

LEARNING OBJECTIVES

  1. Understand the issues in complex patients with common anterior segment diseases
  2. Be able to assist in planning cataract surgery where common anterior segment diseases arise
  3. Be equipped to counsel patients appropriately before cataract surgery is performed when other ocular issues are present, and in doing so, help optimise the outcome for the patient.

 

Ocular Surface Disease and Cataracts

As we are all aware, ocular surface disease is very common in the age group of patients that present for cataract surgery. In many cases the two conditions co-exist. The main risk factors are age, female sex, post-menopausal oestrogen therapy, and corneal refractive surgery. This cohort of patients requires a careful history to ascertain the level of discomfort before cataract surgery is contemplated.1

There are also a number of challenges that need to be overcome to optimise the surgical outcome and this is not only in relation to the final refraction. These patients can present to the optometrist or the ophthalmologist dissatisfied, despite a good visual result, because the eye feels gritty and uncomfortable. In some cases the ‘surgical insult’ – the simple fact that they have had surgery – is enough to tip them over into a level of discomfort that wasn’t there before surgery. It is not unusual for patients to complain about the post-operative drops that are instilled in the eye – a likely reaction to topical preservatives such as benzalkonium chloride (BAK) that can exacerbate dry eye symptoms. It is not uncommon for such patients to present to other specialists complaining of ‘failure’ of surgery, despite an excellent refractive outcome.

It is important therefore, to spend some time counselling patients before surgery is contemplated and to prepare the ocular surface – often a short course of lubricants and steroid drops for a few weeks is all that is required.

In severe cases it may be prudent to defer cataract surgery until there is improvement in the ocular surface parameters and patients may require systemic medication like oral Doxycycline for at least three months.

One study found that cataract surgery acts adversely in all parameters of corneal osmolality and tear physiology – in fact corneal sensitivity did not improve until three months after surgery.2

In another study, the use of topical cyclosporine at 0.005 per cent concentration was seen to be beneficial and patients reported improvements in corrected and uncorrected distance acuity, corneal staining, improved tear break up time (TBUT), contrast sensitivity, and conjunctival staining in relation to multifocal intraocular lens (IOL) use.3 This latter cohort of patients presents a challenge for the cataract surgeon as patients can report smeary vision and reduced contrast sensitivity when ocular surface disease (OSD) is pre-existing.

The effect of ‘surgical insult’ on the ocular surface cannot be ignored. For instance, corneal incision size, location, and type have all been implicated in dry eye symptoms after cataract surgery. Although modern cataract surgery involves very small incisions, some corneal nerves are transected and in some patients this may be an issue that results in a gritty eye.4 Other factors to consider are the duration of surgery and exposure to the microscope light. Prolonged light exposure has been correlated with reduced TBUT with a temporary worsening of symptoms.

A major challenge is the management of patients who desire to have a premium IOL such as a multifocal IOL. These patients invariably desire to be spectacle free at near and distance but have a pre-existing condition (OSD) that complicates matters, both for the acquisition of good pre-operative data (biometry) and also in the process of visual rehabilitation (post-operative) and the quality of vision. Regardless of the technology used, patients with severe dry eye syndrome need to understand that they may get a suboptimal result and should consider a monofocal IOL as a good alternative with a pair of readers for their close work.

In any case, there is a step-wise approach to managing the dry eye patient who is having cataract surgery. This includes the use of artificial tear supplements, dietary changes, and improved systemic hydration, punctal plugs, topical steroid drops and creams, immunomodulatory agents and oral antibiotics.

There is no doubt that in most cases, the cause of dry eye after cataract surgery is multifactorial, so the approach must address all aspects for the given patient, coupled with reassurance as patients get particularly anxious when they have pervasive symptoms that weren’t there before surgery.

Herpetic Eye Disease and the Cataract Patient

Herpes simplex virus (HSV) is almost ubiquitous in the age group of patients that present for cataract surgery due to seroprevalence in the population. In particular, patients with a history of epithelial and stromal disease require specific peri-operative care. Hence, all potential candidates for cataract surgery can present in the immediate post-operative period with a presentation of HSV keratitis, most likely a reactivation of the virus.

It is more common, however, for patients with known HSV infection in the eye to present with an episode of HSV epithelial disease or stromal in the peri-operative period due to the relative immunosuppression induced by topical steroids and the actual insult of surgery. It is therefore advisable to cover these patients with oral anti-viral cover, either with Acyclovir or Valacyclovir (Valtrex) until the steroids are ceased. This is likely to prevent a resurgence of the virus.

Patients with recurrent kerato-uveitis should be quiet for at least six months from a previous episode of uveitis to minimise the risk of reactivation of inflammation. I often perform surgery on such patients under oral anti-viral cover and give intensive steroid drops in a slow taper. In very severe cases, oral prednisolone cover may be required starting a week before surgery. This often proves effective in preventing a post-operative HSV related uveitis.

Patients with HSV related scarring pose a challenge to the surgeon as there may be diffuse scarring that limits the view to perform a capsulorhexis, or there may be a large central or paracentral scar that induces irregular astigmatism. In such cases, it is often better to opt for a spherical correction and avoid a toric IOL as the astigmatism may prove uncorrectable, especially if the cornea has irregular scarring. Bleeding is also a risk as there may be chronic vascularisation into the stroma and, depending on the location, it may result in intracameral bleeding. Such cases may fare better if vessel cautery is performed before cataract surgery to shrink peri-limbal vessels, or if these are treated for a period with topical steroids.

Another issue to consider is cataract surgery in patients with previous herpes zoster ophthalmicus. In many of these patients there may be remnants of previous kerato-uveitis with subepithelial scarring and keratic precipitates. In most cases cataract surgery can proceed without complications, but it is often wise to wait a few months before proceeding with cataract surgery after a recent episode of uveitis. This will minimise the risk of post-operative cystoid macular oedema (CMO) and a protracted post-operative uveitis.

Some of these patients also have chronic pain in the distribution of the trigeminal nerve and the upper eyelid may be tender. It is advisable not to stop their chronic pain medication to minimise any post-operative discomfort. Additionally, extra care needs to be taken with draping in preparation for surgery as removal of the sticky drape at the end of the operation may be very painful.

Cataract Surgery and Keratoconus

Keratoconic corneas pose a particular challenge to the cataract surgeon. Firstly, you have the issue of a typically myopic eye – as these patients often have an irregular corneal topography. The level of keratoconus will also dictate if there is a degree of central or paracentral scarring, with or without thinning. These factors will affect the acquisition of accurate biometry and lens power calculations.5 Eyes with keratoconus have long axial lengths and deeper chambers, making the effective lens position different when compared to a normal eye. Hence, optical biometry in eyes with keratoconus typically overestimates the corneal power and underestimates the IOL target power, resulting in post-operative hyperopia.6

Eyes with typically central cones are more likely to get a better refractive outcome because the biometry of a more regular cornea is more accurate. Additionally, patient satisfaction is likely to be higher as these patients get fewer aberrations when the pupil dilates in mesopic and scotopic conditions.

On the other hand, in cases with very ‘saggy’ or oblique paracentral cones where the visual axis is drawn through part of the ‘tail’ of the cone, the refractive outcomes can be unpredictable both for sphere and cylinder. In some cases it may be better to use a monofocal spherical IOL and not use a toric implant as this may cause more problems by introducing more aberrations. It is now well established that toric IOLs are a good option in patients with stable mild to moderate keratoconus and are well tolerated – an important caveat being that patients have stable non-progressive disease.7,8

A particular consideration is also whether to use a toric implant if a corneal transplant is being contemplated in the future. The answer in such cases would most likely be “no” as this would result in uncorrectable astigmatism and aberrations. In cases where the cornea is stable and a transplant is not likely to happen, it is possible to use a toric implant and the result can be surprisingly good.

A further consideration in advanced cases of keratoconus is the need to rehabilitate the eye with a rigid gas permeable (RGP) lens or scleral contact lens in order to optimise the final refractive outcome after cataract surgery. A thorough evaluation should be performed after surgery as the corneal surface may have changed.9 

The advent of corneal cross-linking (CXL) has improved RGP lens tolerability in recent times. In a published study, RGP users improved their wearing times to almost double after CXL was performed at three and six months post-treatment.10 This is a very positive effect of CXL that improves overall outcomes. 

Figure. 1 A case of corneal trauma in a patient considering cataract surgery. Note the midstromal vertical scarring in the central cornea.

Figure 2. A large pterygium in a patient with cataracts. This lesion should be removed before proceeding with cataract surgery as there may be considerable induced astigmatism that is reversible.

Figure 3. This 47 year old man was hit with a stone in the right eye as a teenager. An anterior subcapsular cataract subsequently developed.

Figure 4a. An 86 year old man with a traumatic cataract. He sustained a penetrating eye injury as a schoolboy with a fountain pen. Note the large inferonasal iris defect. Cataract surgery restored his vision.

Figure 4b. This is the same patient. Gonioscopic view reveals the detail of the  inferonasal iris defect. The ciliary processes are visible behind the iris and in front of the intraocular lens (postop image).

 

Cataract Surgery and Pseudoexfoliation

Pseudoexfoliation (PXE) is an age related fibrillopathy that creates a significant set of problems for the cataract surgeon.11 As we know, the material is deposited throughout the anterior segment and coats all of its structures, including corneal endothelium, iris, lens capsule, zonule, and ciliary body. We also find that the pseudoexfoliative material has proteolytic properties, resulting in localised digestion of zonular apparatus leading to lens instability (phacodonesis). A subtle sign is iridodonesis, which represents the earliest sign of localised zonulopathy. This sign can be elicited with a drop of pilocarpine 2 per cent to relax the zonule.11 

One major challenge is the effect of pseudoexfoliative material on the iris dilator muscle, probably through a localised vasculopathy and hypoxia; hence in many cases the surgeon is presented with a small pupil that needs to be mechanically dilated. The anterior capsule may also have heavy pseudoexfoliative material deposition and this can lead to tear-outs or radial tears at the time of capsulorrhexis or capsular bag ruptures during lens fragment manipulation. PXE patients can also present with eye pressure problems which can be significant and need to be managed appropriately before cataract surgery is contemplated. After surgery, post-operative pressure spikes are common, particularly in the context of pre-existing glaucoma.12

It is thus evident that PXE increases the risk of a complication and this needs to be carefully conveyed to the patient-candidate that presents for surgery. In cases of severe PXE it is not unreasonable to prepare the patient for a two stage procedure, in liaison with a vitreoretinal surgeon, in case the lens drops into the vitreous due to a capsular tear. I find from experience, that patients respond better when there is clarity in the surgical plan and, when there is added surgical risk, they know that all bases have been covered. Managing expectations in this way reduces stress for all parties and minimises the level of disappointment if a complication does occur.

In the immediate post-operative period, it is imperative that the eye pressure is checked on day one as these patients often present with a pressure spike that can be quite significant. It is not unusual to see pressures of 40 or 50mmHg. This responds well to a quick anterior chamber paracentesis followed by a short course of oral Acetazolamide (Diamox) for a few days.

When considering refractive outcomes these patients generally do well. In cases of zonular instability, it is often a requirement to insert a capsular tension ring in the bag and thus achieve better centration of the IOL by distributing all forces equally with the circumference of the zonular apparatus. A question arises if one should use a toric implant in this patient group. The decision remains with the surgeon who will assess the degree of instability and decide what is best for the given patient. In severe cases, it is better to opt for a monofocal IOL as some decentration is likely to happen as the disease progresses.

One consideration that needs a mention is late IOL decentration. This unfortunately is a finding that arises several years down the line in severe cases of PXE and can be a particular challenge. Despite high levels of decentration, some patients retain 6/6 or 6/9 vision and have no complaint. In such cases it is best to exercise caution as the patient is happy and unaware of a problem and no further surgery is required.

It is however a different issue if the IOL/bag complex is very unstable with a drop in vision. In some cases, the whole IOL complex can prolapse into the anterior chamber. In such severe cases it is better to proceed with an explantation. The decision to proceed with an anterior approach (corneal) or a posterior approach (via pars plana with posterior vitrectomy) depends on the level of decentration as in many cases, when the patient is lying on their back the IOL/bag complex drops so far behind into the vitreous that only the expert hand of a vitreoretinal surgeon is able to float it up and retrieve it. Invariably, no matter which approach is taken, the patient is rendered aphakic and a lens needs to be introduced into the anterior chamber (ACIOL). One word of caution is to always measure the endothelial cell counts when contemplating a secondary procedure, as PXE patients often have an endotheliopathy that can result in late endothelial failure and a painful bullous keratopathy. Hence PXE brings forth the biggest challenges for the cataract surgeon and careful surgical planning is required to cover all bases and eventualities.

Cataract Surgery and Glaucoma

Cataracts and glaucoma often co-exist and these patients require careful planning as management of one condition can affect the management of the other. Firstly, it is important to state early on, that cataract surgery does not cure glaucoma. In fact, most studies have shown that the effect of cataract surgery on intraocular pressure (IOP) is modest at best and not long-lasting. Most studies show between 2–4mmHg pressure reduction for a period of one to two years at best.13 Hence, it is imperative that patients with co-existing cataracts and glaucoma have understood that they need to return to their glaucoma drops soon after surgery. In cases where there is a serendipitous drop in IOP, the message is to continue monitoring as the IOP will rise sometime in the future and can lead to further damage of what may be an already compromised optic nerve. The effect of cataract surgery on progressive angle closure can be dramatic. We now know that the angle anatomy changes dramatically (opens) and in cases of IOP elevation, there can be a substantial drop in IOP – where in some cases it can be as high as 10mmHg. Once again however, despite a fall in pressure after cataract surgery, it is prudent to monitor the IOP as it may invariably rise later on and without warning.

A particular consideration has to be given to the sub-group of patients that have progressive glaucoma and cataracts. The challenge is to establish whether these patients should have their cataracts done first or have their disease and IOP stabilised. In cases of progressive visual field loss, it is imperative to intervene on that front first and lower the pressure by whatever means. This is because glaucomatous field loss is irreversible – the cataract can always be addressed later. This may mean having to do a trabeculectomy with a plan to defer cataract surgery for a later date. Another thing to bear in mind is that filtration surgery often leads to cataract formation. In one study cataract formation was seen in 33 per cent of patients after trabeculectomy.14

A particular challenge is addressing a cataract in a patient with a functional trabeculectomy. We know from experience that trabeculectomies don’t fare well after cataract surgery as the surgical insult of cataract surgery can lead to late trabeculectomy failure through scarring.15 It is therefore preferable to delay the cataract operation for a few months after a trabeculectomy and consider injecting an antimetabolite in the upper fornix such as mitomycin C or 5-Fluorouracil to preserve trabeculectomy function. These patients will require careful post-operative follow-up with high frequency steroid drops over a longer period of time. In many cases it is advisable to maintain pseudophakic patients on a single drop of steroid indefinitely to preserve trabeculectomy function.

Cataract Surgery and the Keratoplasty Patient

Cataract surgery post corneal transplantation can be challenging. The most obvious question for the surgeon is the level of visibility of the anterior segment and the anterior capsule to perform the procedure. In cases of severe corneal scarring, one must contemplate a triple procedure or a combined cataract and penetrating grafts (PK) to resolve both issues. If visibility is good then the cataract surgery can be performed, although the view may be limited. There is a risk of inducing graft failure through the added effect of surgical trauma to what may be a compromised endothelium.

Despite modern techniques and instrumentation, there is a risk of endothelial cell loss after cataract surgery and this is more of an issue in patients with corneal transplants. It has been shown that patients with penetrating grafts have the greatest degree of cell loss, followed by patients that have received a lamellar graft at 12 months follow-up.16

There is also the option of performing an endokeratoplasty such as a Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) to replace the failing endothelium and maintain corneal clarity in the graft post cataract surgery.

The level of visual rehabilitation will be dictated by the degree of correctable aberration in the cornea, which may or may not be regular – hence in most cases a monofocal, non-toric implant suffices. In advanced cases where patients have had repeated grafts, there may be iris abnormalities such as peripheral adhesions and/or iris defects. These may be addressed with iridoplasty procedures (pupilloplasty) to minimise post-operative glare once the patient has been rendered pseudophakic.

Cataract Surgery and Pterygium

Pterygia can complicate matters when it comes to cataract surgery. Firstly, it raises the issue of a patient requiring more than one operation to visually rehabilitate the eye, which means added costs and the logistics of two visits to the operating theatre. The first question that arises is, does the pterygium have an impact on the vision, or in other words does the lesion affect the parameters to conclude a good refractive outcome for the patient. It is therefore important to measure the pterygium, assess its invasion into the cornea and perform topography of the cornea. There is good evidence that pterygia affect vision by inducing surface aberrations and astigmatism.17

In most cases of invasive pterygia, we find that there is a flattening effect along the horizontal meridian on topography – hence the effect on the final refractive outcome can be significant. Furthermore, very invasive pterygia can have an impact on the ability to perform accurate biometry and IOL calculations. There is therefore a good argument to remove an invasive pterygium first, allow the eye to settle and then proceed to remove the cataract at a later date. There is good evidence in the literature that pterygia can induce up to two diopters of cylinder and this effect can be reversed by their removal.18

Ideally, it is best to wait three to four months and repeat the corneal topography as it is often the case that the corneal map is totally different at that stage.

Cataract Surgery and Trauma

Trauma to the anterior segment can result in an isolated cataract or can lead to a number of sequelae that need to be addressed concurrently with cataract surgery, or as a series of reconstructive procedures to fully rehabilitate the eye.

In most cases of severe trauma there may be associated findings such as zonular dialysis, posterior capsular tears and co-existing trauma to the cornea and iris. There may be issues with visualisation of the anterior segment due to the presence of blood or corneal oedema or both.

Traumatic cataracts are seen as a consequence of blunt injuries, and as ‘coup vs countrecoup’ injuries, and lens damage is seen in up to 30 per cent of perforating injuries of the anterior segment.19 In cases of blunt trauma there may be trabecular meshwork injury, which may manifest with glaucoma in combination with the cataract. In most cases, the pressure is controlled medically and cataract surgery can follow. It is important for the surgeon to assess the anterior segment carefully and perform gonioscopy to establish if there is angle recession, as pressure problems may arise after surgery.

In some cases of severe blunt angle trauma, a cyclodialysis can be present and held shut by small synechiae in the angle, which split with the fluidics induced by surgery. This can lead to a post-operative presentation of hypotony that needs to be managed either medically or surgically.20

In cases of severe trauma to the anterior segment, the first priority is to salvage the eye by performing a primary repair. In such cases it is best to preserve as much of the anterior segment structure as possible and to consider anterior segment reconstruction at a later date when things have settled and surgery can be performed in a closed environment and under more controlled conditions. In cases of severe trauma there may be other injuries sustained by the patient that are a priority to sustain life and need to be prioritised. 

Iris defects post-trauma are common and can present as tears of dialysis of the iris root. These can be sutured if small, but in severe cases where the iris has been lost there is the option to insert artificial iris segments in the sulcus or the bag when performing cataract surgery, or in isolation to reconstruct the iris diaphragm.

In some cases of blunt trauma, the eye develops a fixed dilated pupil (Urretz-Zavalia Syndrome) and the patient complains of glare as a combination of an enlarged entrance pupil and the cataract. A good option here is to remove the cataract and perform iris cerclage to reduce the entrance diameter of the iris diaphragm. This reduces any symptoms of glare from excessive light entering the eye.

In cases of trauma, where there is vitreous in the anterior chamber, it is important to perform a thorough examination of the posterior segment to rule out any traumatic retinal pathology. In some cases a peripheral retinal tear can be found that needs to be addressed with retinopexy or, if a small detachment is found, vitrectomy or buckle procedure.

Small amounts of vitreous in the anterior chamber are not uncommon after blunt injury as a consequence of a localised zonular dehiscence. Small amounts can be addressed with the vitrector at the time of cataract surgery. At the end of the procedure it is imperative that all ports are sutured to prevent a vitreous wick effect where small vitreous strands find their way to the ports, resulting in peaking of the pupil and the added risk of endophthalmitis.

Finally, in cases of severe trauma there has to be a realistic approach to attempting cataract surgery in patients who have little or no visual potential. Visual loss can be a consequence of a totally disorganised anterior segment, glaucoma, retinal injury, posterior globe rupture or a combination of all the above. There is also a concern that severely traumatised eyes can induce a sympathetic ophthalmitis in the good remaining eye; hence it is important to have the right perspective and know when to stop with further surgery.


   

Dr. Alex Ioannidis is a cataract and anterior segment specialist. He is Fellowship trained both in cornea and glaucoma. Dr. Ioannidis is able to offer his patients refractive cataract surgery and one of his many interests is cataract surgery in complex patients with other diseases of the anterior segment.

He works as a VMO at the Royal Melbourne Hospital and consults privately at Vision Eye Institute in Melbourne.


References
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7. Alio JL. Pena-Garcia P, Abdulla Guliyeva F , et al: MICS with Toric Intraocular Lenses in Keratoconus:outcomes and predictability analysis of post-operative refraction. Br J Ophthalmol 2014; 98: 365-370
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12. Pohjalainen T,  Vesti E, Uusitalo RJ, et al. Intraocular pressure after phacoemulsification and intraocular lens implantation in non-glaucomatous eyes with and without exfoliation. J Cataract Refract Surg 2001; 27:426-431.
13. Friedman DS, Jampel HD, Lubomski LH, et al. Surgical strategies for co-existing glaucoma and cataract: an  evidence -based update. Ophthalmology 2002;109: 1902-1913
14. Tham CC, Kwong YY, Baig N, et al. Phacoemulsification versus trabeculectomy in medically uncontrolled chronic angle-closure glaucoma without cataract. Ophthalmology 2013; 120:62-67
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' The effect of ‘surgical insult’ on the ocular surface cannot be ignored '