Approaching Cataract Versus Refractive Lens Exchange Patients

Patients seeking refractive lens exchange (RLE) have different needs than cataract patients do. Therefore, it is important that the surgeon understand these differences and aim to provide personalized care for each patient. The approaches to managing these two groups of patients present different emphases and challenges; clinical considerations for the RLE patient are different from those for cataract patients, even though cataract surgery is generally regarded as a refractive procedure today. In this article, I discuss the key considerations and differences in approaching cataract and RLE patients.

VISUAL COMPROMISE AND EXPECTATIONS
Cataract patients. Patients in this group may have a visual disability in terms of pre-existing refractive error and, because of their age, are also presbyopic. Additionally, these patients have a visual impairment caused by their cataract. They expect improved vision after surgery, but not necessarily full visual recovery. Most cataract patients expect to wear a form of prescription glasses after surgery.

RLE patients. On the other hand, RLE patients have no visual impairment unless they are amblyopic in one eye; however their refractive error causes them to seek a surgical solution. RLE patients expect a return to full visual potential—and more demanding patients expect even better vision after surgery—without any optical aid for all distances.

PSYCHOLOGY OF PATIENT MANAGEMENT
The key to successful management of the RLE patient is to recognize differences in motivation for surgery and expectations and determine how they affect the clinical and personal dynamics of decision-making in this group. Some patients may not fall strictly into either the cataract or RLE group, and your approach must be adapted accordingly.

Cataract patients. These patients are older, presbyopic, and, therefore, accustomed to wearing glasses. They know they have an age-related disease. Their primary motivation for seeking surgery is to restore quality of life. Freedom from wearing glasses, if achieved, is a bonus.

RLE patients. These patients are younger and are forced to wear an optical aid to correct their refractive error. Patients over the age of 40 years may have an additional aid or use monovision for near. These patients have full visual potential but for lifestyle or occupational reasons wish to become less dependent on their optical aids. Generally, they are seeking a life-changing or life-enhancing experience. They are more critical and more demanding than cataract patients; however, they are also appreciative of the surgical outcome if their expectations are met. Removing the crystalline lens produces loss of accommodation, and the provision of multifocal vision is a crucial part of managing RLE patients. Preoperative counseling and postoperative support for RLE patients require a lot of chair time from the surgeon and his team. There is no substitute for this.

Options for the management of accommodative loss in young RLE patients who did not need separate reading glasses before surgery include monovision and multifocal or accommodating IOLs. Each option should be discussed, in detail, with the patient prior to surgery. Unfortunately, there is not yet a perfect solution for accommodative loss, and careful explanation of the benefits, limitations, and adverse effects of each option is mandatory. Patients must be notified of the possible loss of stereopsis with monovision; limited range of pseudoaccommodation with current accommodating IOLs; and the photopic phenomena, loss of light transmission, and loss of contrast sensitivity associated with multifocal implants.

There is an increasing trend toward mixing and matching IOLs (usually multifocal implants) to achieve the maximal binocular outcome. Personally, I think this fudges the limited performance of current IOLs, and I prefer to remain in my comfort zone because there is currently no perfect IOL on the market. This allows us to under-promise, where hopefully the outcome is over-delivery with a higher rate of patient satisfaction.

BIOMETRY
In cataract patients, the UK Royal College of Ophthalmologists' (RCO)¹ benchmark for good biometry is 50% within ±0.50 D, 90% within ±1.00 D, and 100% within ±2.00 D of the target refraction. Use of the IOLMaster (Carl Zeiss Meditec, Jena, Germany) with SRK/T, Haigis, and Hoffer Q formulas has become the standard in IOL power calculation; results often surpass the RCO guidelines. However, this level of accuracy in IOL power calculation is unacceptable for RLE patients. We recommend using both immersion ultrasound biometry and optical biometry with the IOLMaster in all RLE patients. We also suggest reference to the Holladay 2 formula, especially for myopic eyes with long axial length. Consistency in biometry techniques and optimization of A-constants are essential.

ASTIGMATISM
Avoiding surgically induced astigmatism and managing pre-existing astigmatism are mandatory when dealing with RLE patients. Bimanual or coaxial microincision cataract surgery (MICS) incision techniques with on the steep corneal axis and the use of IOL injectors will generally avoid significant surgically-induced astigmatism. In RLE patients, however, it is essential to reduce pre-existing astigmatism below 1.00 D for both multifocal and accommodating IOLs. Optimum performance for near vision is achieved with 0.50 to 0.75 D of with-the-rule residual astigmatism.

Significant residual astigmatism degrades image quality and produces ghosting. We advise that the surgical plan, including how the surgeon intends to deal with pre-existing astigmatism, be determined and discussed with the patient preoperatively. An additional procedure including corneal incisions, corneal laser surgery, toric IOLs, or a combination may be necessary. It is important that only regular corneal astigmatism evaluated by a corneal mapping system be treated. We use the Pentacam (Oculus OptikgerŠte GmbH, Wetzlar, Germany; Figure 1) because it also allows us to detect eyes with corneal ectasia, which are then excluded for RLE. Any form of corneal ectasia is a contraindication for RLE (Figure 2).

SURGERY AND VISUAL RECOVERY
Phaco surgery and any preplanned astigmatic procedure should be meticulous in cataract as well as RLE patients, but before RLE time must be spent explaining the speed of visual recovery after RLE. Today's cataract patients expect immediate visual recovery following surgery. RLE patients expect similar rapid visual outcomes despite their sometimes complex refractive errors. It is important to mention that developing intermediate vision may be delayed because of the period of cortical adaptation with some multifocal IOLs. With accommodating lenses, near vision improves with time; however, both distance and near visual recovery may be delayed when atropine is used with the Eyeonics Crystalens HD IOL (Bausch & Lomb, Rochester, New York).

CASE REVIEW
In early 2007, a 43-year-old man requested corneal laser surgery to correct his hyperopic astigmatism. He had just begun to use his first pair of reading glasses over contact lenses. Refraction in the right and left eyes was 7.75 -4.00 X 10° (Figure 1) and 8.50 -3.75 X 170°, respectively. There was 1.00 D of sphere add in both eyes for near vision. The anterior chamber depth was less than 3 mm, and his crystalline lenses were clear. He wanted to be free of both distance and near optical aids. Because his refraction was not ideal for laser vision correction, he had two options: (1) RLE with a multifocal or accommodating IOL, followed by LASIK and the possibility of a later enhancement with astigmatic keratotomies; or (2) RLE with a toric monofocal IOL, with some monovision or prescription glasses for near vision and the possibility of a sulcus-fixated piggyback multifocal IOL later. The decision was to wait.

In April 2008, the patient had RLE in his left eye with a toric multifocal M-Flex T IOL (Rayner Intraocular Lenses, Ltd., Sussex, United Kingdom). Two weeks postoperatively, he had what we considered an excellent refractive result: 6/6 distance UCVA and N6 near UCVA. His refraction was 0.25 -0.75 X 85°. However, the patient was unhappy with his quality of vision, and he did not proceed with the second eye (surgery was planned for 4 weeks after the first RLE). After several consultations and hours of chair time with the surgeon, the reason for his dissatisfaction became apparent: loss of contrast sensitivity when he compared pseudophakic multifocal vision with phakic contact lens vision.

In another case, a 49-year-old woman had similar refractive errors and bilateral cataracts. The same model toric multifocal M-Flex T IOL was used, and there was no issue after the first eye surgery. She proceeded to second eye as planned, and she has never complained of poor quality of vision with these IOLs. These examples highlight two challenges of managing the two groups of patients: discussion on loss of transmission of light with multifocal IOLs and the interval for the second eye surgery.

The toric multifocal M-Flex T IOL has the toricity on the anterior surface of the lens optic and the multifocal design with a square edge profile on the posterior surface. The male patient has since undergone Nd:YAG capsulotomy (within 3 months of surgery) because of minimal posterior capsular changes (Figure 3) and also had a canalicular plug to assist with tear retention and improve corneal lubrication. He has now adapted to the vision in both eyes and agreed to proceed with RLE with the same model IOL in the second eye.

CLINICAL RESCUE PACKAGE
Surgeons who wish to perform RLE should have a back-up service for patients, providing support from the clinical team and office staff; abundant chair time with the surgeon; testimonials from happy patients within the practice; enhancements, including incisional corneal surgery, corneal laser surgery, or an add-on/piggyback IOL; IOL exchange; access to an Nd:YAG laser facility; and canalicular plugs for ocular surface problems.

CONCLUSION
Cataract patients are usually among the most grateful patients after phaco surgery because they see the benefits of the procedure immediately. RLE patients can be equally grateful, and they are often more appreciative of the efforts of the clinical team, despite their higher expectations.

RLE is not good cataract surgery with either a multifocal or an accommodating IOL; RLE requires exquisite attention to detail, greater preoperative diagnostics, more chair time with the patient, and the back-up support described above as the clinical rescue package. Approaching cataract and RLE patients requires strict adherence to well-established protocols for a successful and rewarding clinical practice.

Tayo Akingbehin, MD, FRCS, FRCOphth, is a Consultant Ophthalmologist and Refractive Surgeon, and Medical Director of iSight Clinics, United Kingdom. Dr. Akingbehin states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +44 1704 563279; fax: +44 1704 550057; e-mail: tayo@iSIGHTClinics.com.

1. Royal College of Ophthalmologists. Cataract Surgery Guidelines. Available at: www.rcophth.ac.uk/docs/publications/CataractSurgeryGuidelinesMarch2005Updated.pdf. Accessed December 30, 2008.