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Thursday / October 18.
HomemiophthalmologyCataract Surgery and IOLs: What the Doctor Ordered?

Cataract Surgery and IOLs: What the Doctor Ordered?

Among many disciplines in eye care where co-management is a necessity, perhaps the most challenging is in the area of cataract/refractive surgery care.

Optometrists are leaders in this field as inevitably, patients interested in cataract surgery will have a number of vital questions needing evidenced–based answers. Thus, all primary eye care providers should have a working knowledge of the procedures, techniques, and intraocular lenses currently available.

Why is it that a subjective refraction can be performed by two independent optometrists, but a patient may prefer one over the other?

The ‘devil is in the detail’ as they say – a subjective refraction is a ‘no brainer’ but refining this to your patient’s needs takes skill and practice.

Cataract surgery is much the same. New technologies and the refinement of surgical techniques have brought us into an era where all patients can be afforded the opportunity to achieve excellent, uncorrected acuity following cataract surgery. A one-size-fits-all approach is no longer appropriate.

The current wide variety of multifocal IOLs expand the potential range of vision, moreover they are also able to correct astigmatism

For this reason, it is essential to establish a strong relationship with your referring ophthalmologist. Most importantly, choose to work with surgeons who will respect you as an equal partner in the patient management and decision making process. Co-managed care involves all parties knowing about your patient’s lifestyle demands and understanding their expectations. Ensuring you’re able to communicate this vital information will avert many issues that could potentially arise after even uneventful surgery.

As all of us know, successful outcomes following cataract surgery generate great satisfaction. While the majority of patients should enjoy excellent outcomes, the path to success is not always straightforward.

Patients who present for cataract surgery may also have other active or chronic ocular conditions requiring attention. It is therefore useful to partner with a number of surgeons who are well versed in different sub-specialty areas. For example; a patient with even stable non-proliferative diabetic retinopathy is best in the hands of a retinal sub-specialist who can pre-empt and avert potential complications such as refractory dry eye, slow wound healing, and rebound inflammation including cystoid macular oedema (CME).1

Patients with glaucoma may be appropriate candidates for simultaneous stenting procedures under a glaucoma specialist. Patients with corneal ectasias may need an opinion by a corneal sub-specialist at some point. Patients who are referred for cataract surgery must therefore understand that this is a process rather than simply a procedure. They should be encouraged to embrace the fact that there are various aspects of their eye health requiring attention in order to ensure a successful outcome. This can be a difficult concept to realise for the everyday person who is still grappling with the fact that their sight is deteriorating.

OPTIMISING VISUAL POTENTIAL: REFRACTIVE HEALTH ASSESSMENT

A thorough evaluation of ocular and general systemic health is key in the initial assessment of any refractive surgery candidate. There should be no exception when considering whether a patient is ‘ready’ to have cataract surgery (Table 1).

Some obvious cases that we can all recall are those patients with a pterygium encroaching onto the limbus; refractory dry eye; or acute on chronic lid margin disease. Our best judgement tells us that these conditions need to be treated in the first instance, before considering any ocular surgery. However, many of us may not be aware that there are also certain groups of individuals who require cautious perioperative attention.

These include patients with active collagen vascular disease (in particular lupus, rheumatoid or any inflammatory arthritis and Sjögren’s syndrome), patients with thyroid disease, as well as those currently receiving chemotherapy.2 While these systemic conditions are not absolute contraindications to surgery, even routine surgery can be complicated if they’re not addressed. This is best done by the patient liaising with their primary health provider, often their GP. In many instances it is best to postpone surgery until the condition has been adequately treated and compromising medications ceased.

Patients may find your attention to detail in this respect frustrating. My response to this would be to assure them that we need to optimise their vision following cataract surgery to ensure the excellent vision they desire. A healthy ocular surface provides a robust ocular surface on which to perform surgery, hastens the healing process, and opens up a world of possibility for intraocular lens (IOL) choice.

Patients are now regarding cataract surgery as more of a refractive procedure, and they expect their optometrist to help them achieve an excellent visual outcome

DEALING WITH ASTIGMATISM: TO CORRECT OR NOT TO CORRECT?

There is a quiz I like to play with my registrars called ‘corneal surgeon or toric IOL?’ and I have included an excerpt in this article (Figure 1). Essentially, it addresses when to counsel patients that the type of astigmatism inherent in their cornea will need correction at the time of cataract surgery. This option is reserved for regular corneal astigmatism, as demonstrated on corneal topography and, as a general rule, is suitable for astigmatic patients that need correction for 0.50D or above.

The key is to be diligent enough to focus on the corneal topography and determine if it is:

  1. An acceptable scan – dry eye, wearing of RGP, or even soft contact lenses in last (24 hours) can alter this reading,3 and
  2. Whether it is regular – even subtle differences between the two eyes may suggest subclinical ectasia that may complicate visual outcome

Where corneal topography may not be readily available, patients who present with myopic astigmatism in excess of 2.50D in their subjective refraction, or a change in cylinder refraction, should have corneal topography as part of their pre cataract work-up.

In most patients with regular astigmatism, a toric IOL will best suit their needs and many ophthalmologists will employ surgical programs pre-operatively and techniques intra-operatively to allow precise calculation of the power and axis that the IOL needs to be placed at, as well as an estimate of the residual astigmatism post operatively (Figure 2).

KERATO-ECTASIA AND TORIC IOLS

The placement of toric IOLs can be challenging in the setting of corneal ectasia. This is where you need a close working relationship with your corneal surgeon in the lead up to considering whether cataract surgery is appropriate for the patients.

In recent times, younger patients in particular, have had the benefit of technological advances including collagen cross-linking (CXL), which has revolutionised the treatment of keratoconus. A 2010 study indicated that 97 per cent of patients who undergo CXL during the early stages of the ectatic process showed no evidence of further disease progression.5

Furthermore, patients who present with early ectatic signs on the posterior corneal surface may be possible candidates for combined CXL and lamellar or surface excimer ablation procedure. This increases collagen lamellar and strand crosslinking, enhancing corneal rigidity.5,6 In due course, when these patients require cataract surgery, it is likely that while their corneas will not be akin to a normal cornea, they may well be able to proceed with toric IOLs with just as much success as their counterparts who have regular astigmatism.

However, many older patients with corneal ectasia will not have had the opportunity for treatments such as CXL and their ectasia, as well as cataract, will continue to advance. Considering a toric IOL in these patients can be controversial; some would consider a monofocal IOL to be the more appropriate choice and residual astigmatism can be corrected with glasses or contact lenses. Others may advocate that a toric IOL may be reasonable depending on the severity of the ectasia, however the post-operative refraction is still unpredictable. Most surgeons however, would steer these patients away from any multifocal IOL.7

UNDERSTANDING PATIENTS’ REFRACTIVE DESIRES

It is imperative to have a good understanding of the patient’s visual goals and expectations. Early presbyopic low myopes, who hope to eliminate spectacle use altogether, and patients with unrealistic expectations, require extensive education about the potential outcomes. Presbyopic or pre-presbyopic patients need counselling with regards to the eye’s anatomy and the concept of accommodative loss with age. As such, it is best to illustrate what they can expect when performing near visual tasks when fully corrected for distance acuity.8 Such patients can opt for a monovision outcome with surgery designed to under correct the non-dominant eye or alternatively consider a multifocal intraocular lens.

Figure 2a & b. Marketing the placement of the toric intraocular lens pre-operatively

REFRACTIVE SURGERY AND IOLS

In many centres, most cataract surgeons use aspheric IOLs in cataract surgery. This design has been incorporated into a majority of the toric, multifocal, and accommodating IOLs on the market. Studies have shown that by countering the positive spherical aberration of the cornea, aspheric IOLs deliver improved visual outcomes.9 For eyes with increased positive spherical aberration after myopic LASIK, the better IOL choice is one with negative spherical aberration. For eyes that have undergone hyperopic LASIK, an IOL with positive spherical aberration or an aberration-free lens is the most appropriate choice.10

Firstly there is no bad karma in suggesting a multifocal IOL in a patient with whom you have had a discussion regarding their visual demands being greatest at near and intermediate distances

WHICH PATIENTS ARE BEST SUITED TO MULTIFOCAL IOL?

Multifocal IOLs undoubtedly offer patients the greatest range of vision but they require some visual compromise and neuroadaptation. The current wide variety of multifocal IOLs expand the potential range of vision, moreover they are also able to correct astigmatism.

However, the choice of a multifocal IOL raises some important questions: Does advocating a multifocal IOL for your patient mean that they will never set foot in an optometric practice again for glasses or contact lenses? Will the visual needs of the patient change in years to come and will they regret being selected for this premium IOL? Are they going to be 100 per cent happy with your advice? Allow me to dispel some of the myths.

Firstly there is no bad karma in suggesting a multifocal IOL in a patient with whom you have had a discussion regarding their visual demands being greatest at near and intermediate distances. However, patients need to understand that there is a compromise in using premium IOLs – while they will enhance their spectacle independence, they are not 100 per cent effective. The key being educate, don’t advocate.

Figure 3. Femtosecond laser assisted cataract surgery; central capsurlorhexis placement.

But the question remains, who is best suited? Because multifocals split the light rays into two foci as they pass through the lens, the patient’s visual axis, and in this regard ocular anatomy, needs to be free of any pathology that might reduce vision. Patients with previous corneal surgery such as LASIK, don’t do well with multifocals. Other comorbidities to perhaps preclude patients include glaucoma, macular degeneration, diabetic retinopathy, and epiretinal membrane.11

With the advent of newer technology, the current multifocal IOLs on the market have less of the haloes, glare and dysphotopsias that were commonplace with these lenses in the past. However, patients do need to be fully educated about these during the adaptation period.

Hyperopic patients seem to have the highest acceptance rate for multifocal IOLs, but they also do extremely well with monovision. Depth of focus, which is a function of a smaller pupillary diameter, seems to work best with hyperopic patients, and some are able to read and see in the distance with a standard monofocal IOL. Blended vision or modified monovision also works well with a residual refractive error of -1.25D to -1.50D in the non-dominant eye. If your patient has been successful in the past with monovision with contact lenses or LASIK, they’ll almost always do well with this strategy using IOLs.12

DISPELLING THE MYTHS

When Should You Suggest Femtosecond Laser Cataract Surgery? 

Even ophthalmologists are divided on this question, with some advocating routine use of laser and others waiting for more compelling safety and data outcomes to be revealed in the literature before adopting this technology.

As with any laser procedure, results are more predictable than with manual techniques. The femto laser makes a perfect corneal incision and more importantly, anterior capsulorohexis which is often the most challenging part of the surgery regarding post-op IOL performance. When the capsulorohexis is perfectly sized and centered, toric and multifocal IOLs have the best chance of exact centration and least chance of tilt providing optimal visual outcome.13 

Other patients who are more likely to benefit from use of femto technology are those with a dense brunescent nuclear sclerosis, low endothelial cell count, or hypermature white cataract.

As femto laser is a non-covered benefit, patients have a higher out-of-pocket fee when this element of the surgery is used. Patients have to weigh the purported benefits against the added costs; some certainly do gravitate toward the newest techniques and the latest technology.

There are a few exceptions and some caution should be exercised in considering surgery in patients with traumatic cataracts where zonular dehiscence can be unpredictable and cause further surgical complications. Additionally, patients with a history of anterior basement membrane disease, or previous LASIK are not ideal candidates in all cases as this can predispose to flap complications.14

There is no doubt that time will tell if this technology makes a positive enough influence on surgical outcomes compared to standard phacoemulsification. Until then, it is a technology to be aware of and is being used more and more in our community. One should certainly consider it in the counselling of a patient prior to cataract surgery.

Should I Consider Same Day Bilateral Cataract Surgery? 

It is not routine practice in ophthalmology to perform immediate sequential bilateral cataract surgery.

However, the rapid visual recovery and low complication rates associated under topical anesthesia have led to increased interest in this approach in some centers, particularly in the international arena. The major advantages being, lower risk of anesthesia, financial savings for the patient, reduction in travel, and ease of follow-up care.

The risks appear to outweigh the benefits. Foremost is the risk of potentially blinding complications in both eyes, such as endophthalmitis or toxic anterior segment syndrome (TASS), which can be devastating. Another potential disadvantage of immediate sequential bilateral surgery is the inability to adjust intraocular lens choice pending the refractive outcome of one eye post-surgery.15

It is not routine practice in ophthalmology to perform immediate sequential bilateral cataract surgery

CO-MANAGEMENT PEARLS

There was a time when the optometrists’ primary responsibility in cataract surgery was to ensure good medical eye care during the postoperative period. Patients are now regarding cataract surgery as more of a refractive procedure, and they expect their optometrist to help them achieve an excellent visual outcome.

Thus, the care we now provide needs to extend from a solid understanding of the patient’s visual expectations to a vigilant attentiveness to potential complications. As a result, co-managing providers must remain attuned to the nuances of specialty intraocular lenses, risks and benefits of some over others, and consider that some patients may need pre-op co-management prior to being ready for surgical intervention.

It may be useful to keep the following pearls in mind when co-managing these patients:

  • Spend some time discussing the IOL options with your patient. They will appreciate a basic understanding of what lenses or procedures they are suitable candidates for
  • Remember to treat all poor ocular surface or lid margin disease aggressively prior to consideration of cataract surgery
  • Remind patients who have undergone previous refractive laser procedures that their process may slightly differ; they will need further pre-operative assessment and consultation to ensure an optimal outcome
  • Advise patients who regularly wear contact lenses that they should cease wear prior to seeing their ophthalmologist for a cataract work-up, at least 24 hours before work-up for those wearing soft contact lenses, and up to 72 hours ahead of the work-up for those wearing RGP lenses, as this will affect biometry readings
  • Pass on necessary medical history to the referring ophthalmologist as it may alter the procedure performed; for example: anticoagulant use; Flomax for benign prostatic hypertrophy; previous ocular trauma; or previous refractive laser procedures
  • Communicate the post-operative comanaged care plan that you are keen to put in place with your patient and referring surgeon. Patients are often reassured to hear this from you first and prior to seeing their surgeon.

Dr. Christolyn Raj is a Melbourne trained cataract and refractive surgeon with sub-specialty training in the latest laser refractive cataract surgery and presbyopia correcting lenses including multifocal IOLs. Her extensive clinical work and research in diabetic and other retinal vascular disease results in her overseeing the surgical care of the majority of patients who present with cataract and co-morbid disease. She practices at Vision Eye Institute Camberwell and Coburg and Sunbury Eye Surgeons in Melbourne.

References:

  1. AAO Cataract in the Adult Eye Preferred Practice Pattern Guidelines , AAO 2016.
  2. Fox M, Quinn C. In the Pursuit of Emmetropia. Review of Optometry , October 2014(15) 24-26.
  3. Novis C. Astigmatism and toric intraocular lenses. Curr Opin Ophthalmol. 2000 Feb;11(1):47.
  4. Horn JD. Status of toric intraocular lenses. Curr Opin Ophthamol. 2007 Feb;18(1):58-61.
  5. Caporossi A, Mazzotta C, Baiocchi S, Caporossi T. Long- term results of riboflavin ultraviolet A corneal collagen cross- linking for keratoconus in Italy: The Seina eye cross study. Am J Ophthalmol. 2010 Apr;149(4):585-93.
  6. Spoerl E, Huhle M, Seiler T. Introduction of cross-links in corneal tissue. Exp Eye Res. 1998 Jan;66(1):97-103.
  7. Alpins N, Stamatelatos G. Customized photoastigmatic refractive keratectomy using combined topographic and refractive data for myopia and astigmatism in eyes with forme-fruste and mild keratoconus. J Cataract Refract Surg.2007; 33(4):591-602.
  8. Khor WB, Afshari NA. The role of presbyopia-correcting intraocular lenses after laser in situ keratomileusis. Curr Opin Ophthalmol. 2013;24(1):35-40.
  9. Tang M, Wang L, Koch DD, Li Y, Huang D. Intraocular lens power calculation after previous myopic laser vision correction based on corneal power measured by Fourierdomain optical coherence tomography. J Cataract Refract Surg. 2012;38(4):589-594.
  10. 10 . McCarthy M, Gavanski GM, Paton KE, Holland SP. Intraocular lens power calculations after myopic laser refractive surgery: a comparison of methods in 173 eyes. Ophthalmology. 2011;118(5):940-944.
  11. Takakura A, Iyer P, Adams JR, Pepin SM. Functional assessment of accommodating intraocular lenses versus monofocal intraocular lenses in cataract surgery: metaanalysis. J Cataract Refract Surg. 2010 Mar;36(3):380-8.
  12. Zhang F, Sugar A, Jacobsen G, Collins M. Visual function and patient satisfaction: Comparison between bilateral diffractive multifocal intraocular lenses and monovision pseudo-phakia. J Cataract Refract Surg. 2011 Mar;37(3):446-53.
  13. Den Beste, B. Where do you stand on Refractive surgery controversies? Review of Optometry, October 2014(15) 31-32. \
  14. Chang J. Femtosecond Laser complications and their management. Cataract and Refractive Surgery Today (CRST) Europe , June 2010. 15. AAO Cataract in the Adult Eye Preferred Practice Pattern Guidelines , AAO 2016