By William B. Trattler, M.D., Neel R. Desai, M.D., Carlos Buznego, M.D., and Gabriela Perez, B.S.

Cataract surgery has been touted as one of the most common operations in the United States with over 3 million procedures performed per year. Perhaps more impressively, this invasive procedure is also one of the most successful. With success rates estimated at ~99% and rapid technological advances over the past decade, both surgeons and
patients alike have become increasingly demanding of refractive perfection post cataract removal.

by Dr. Dale Pilkinton, M.D.

All cataract patients have some artifact or light-scattering phenomenon after IOL implantation, regardless of implant style, size, or material.  Surgeons see this in many forms, characterized as either TCS (temporal crescent syndrome), dysphotopsia, edge glare, or other monikers.  

In our clinic, we have seen this for over 20 years.  It does not discriminate between lens manufacturers.  The patient describes the phenomenon at the one-day post-op visit, is told it is “normal” and will go away, or that  “you will get used to it”.  After 3 months or so, most patients do accept it, although it is generally still there.

Indeed, in my own early experience, I asked my technician (who is still with me) to document any artifact with pictures or drawings in our post-op charts and after several weeks discovered it occurred in almost all patients.  I asked her to stop since it was such a common occurrence in order to save time

Lens manufacturers struggle with this issue for several reasons.  The industry standard for incision size is 3.0mm in order to minimize post-op astigmatism.  Since 1991, when the first two manufacturers had FDA-approved foldable IOLs (AMO and STAAR), there has been a constant “race” to get to the “smallest possible wound.

Manufacturers have used several methods to enable their injector/lens combinations to get through smaller and smaller wounds, but, generally, have done this by making the lenses smaller and thinner. 

The ALCON Acrysof IOL platform uses a hydrophobic acrylic material with a refractive index of 1.55, the thinnest in the industry.  This lens gets most of the attention for artifact, but this may also be due to its 56% US Market share. The properties of the lens, particularly its thinness, enable it to go through its smaller injector (2.4mm).  However, because the material is so rigid, the 6.0mm optic must have three (3) different-sized cartridges as the power-scale is ascended and the IOL becomes thicker.

All other manufacturers face similar issues, but generally, the larger or thicker the optic, the larger the incision.  Astigmatism control is more important to the surgeon than potential artifact that “goes away”.

Oval optics have been around since 1989 and the introduction of 5.0mm optics and the 5.0mm x 6.0mm Clayman lens.  These PMMA optics were introduced to minimize loss of market share to the budding foldable lens industry.  As surgeons discovered they could minimize astigmatism by using the smaller foldable lens incision of 4.0mm with a 6.0mm optic, the shift to foldables crowded out these smaller PMMA lenses.

Before PMMA lost favor, there was a similar race to eliminate artifact.  IOLAB and Intermedics, the two leaders for most of the 1980’s, had started with 5.0mm optics early, and escalated from the original 5.0mm to 7.0mm and were discussing 7.5mm lenses with 14.5mm-wide loops.  At this point, the principal lens controversy was over sulcus or bag placement and sulcus proponents saw no need to limit optic size since it covered a multitude of “sins” (centration, tilt, and artifact among them).

In the 90’s as foldables grew, the retina surgeons gained power as they begandealing with more and more post-op IOL patients.  Concerns about material and overall length arose, but the biggest issue was optic size.  Retina surgeons would prefer to work on patients with the largest possible optic.  Alcon now has a large Acrysof( 6.5mm) for “special” patients, although it requires a larger incision.

The most popular sub-6.0mm IOLs currently in use are the B&L Crystalens (5.0mm) and the Softec Series from Lenstec (5.75mm).  Neither company reports debilitating artifact with either lens, although there are some reports in the literature on the Crystalens.

Minimizing or eliminating artifact in our cataract patients would be a major step in improving one-day VAs.  The ideal product would need to:

Maintain a smaller incision size (sub-3.0) and, ultimately, be capable of going through a 2.4mm wound or smaller.

Not be susceptible to tilt or decentration.

Have the widest possible temporal “window”.

Utilize existing cartridges and injectors.

Have the least-burdensome regulatory pathway.

An Oval Softec HD would allow for a 5.75mm x 6.25mm optic with a 12.5mm overall length, and would cover the needs of expressed above.  If proven, it would minimize artifact, give the retinal surgeon a larger window,  and improve early VAs.

Convincing a referred patient to move ahead with second-eye surgery was not an easy task. 

Today, 20/20 is not always an acceptable outcome for premium lens patients. Even with all the advances in IOLs and surgical technologies, visual anomalies can still occur, and an IOL’s optic design may or may not be a factor.1 Among these phenomena, dysphotopsia is one patients often complain about; however, rarely is it reported in patients’ charts. 

ARC-SHAPED SHADOW 

Negative dysphotopsia, described as an arc-shaped shadow, usually in the temporal field of vision, is a rare condition that can present after in-the-bag posterior chamber IOL implantation.2 Positive dysphotopsia, in the form of halos, glare, and streaks, is more commonly noticed by patients. Those phenomena tend to occur especially in scotopic conditions, whereas patients are more likely to report that negative dysphotopsia persists all the time. 

The literature on negative dysphotopsia is growing, but we do not yet have the means to distinguish patients who will be symptomatic from those who will be dysphotopsia-free after surgery.3 Patients who are sensitive to light seem to be more affected when light enters the eye temporally (40º to 90º), and it is the subsequent shadow symptoms they complain most about.1 Full resolution without surgical intervention occurs for some patients; if the condition persists, IOL exchange or secondary lens implantation can be performed to alleviate the symptoms.3,4 

Anecdotally, I have found that when dysphotopsia occurs in one eye, the contralateral eye is at higher risk for the same condition. I have also noticed that patients with chronic negative dysphotopsia often delay second eye surgery for fear of experiencing the same complication. I now have a good surgical strategy for treating these patients that includes implanting the Softec HD Oval IOL (Lenstec). 

CASE PRESENTATION 

In March 2012, a 69-year-old woman underwent uncomplicated cataract surgery in her left eye at another center. The day after surgery, UCVA was 20/25; however, the patient described what she referred to as a “bubble” or a “blinder” in her temporal field of vision. At 1 week, UCVA remained 20/25, and complaints of the shadow continued. The UCVA was stable at the next follow-up, but the patient still complained of the shadow, so she was referred to a retina specialist for evaluation. The retinal exam was unremarkable, and visual field tests yielded nothing of substance. 

She was referred to me in May 2012, and I diagnosed her with negative dysphotopsia. We discussed her options, including reverse optic capture, IOL exchange, and secondary lens implantation. Unsatisfied with the lack of a proven treatment, the patient sought a second opinion outside our office. That physician confirmed the diagnosis and discussed similar treatment options but, in the end, recommended observation rather than additional lens surgery. 

The patient returned to our office in March 2013 with complaints of glare and halos in her fellow eye, and she reluctantly scheduled cataract surgery. At every visit, she stressed that she could not tolerate having the same type of shadowing in both eyes. I therefore suggested implanting the Softec HD Oval, which has a wide, oval optical zone (5.75 X 6.50 mm) and a large overall length (12.5 mm). These factors together reduce the risk of negative dysphotopsia. The size of the optic makes this lens essentially pupil-independent, meaning it is less sensitive to decentration and more forgiving as capsular centration occurs postoperatively. 


TAKE-HOME MESSAGE

Patients who are sensitive to light seem to be more affected by negative dysphotopsia when light enters the eye temporally. 

IOL exchange or secondary lens implantation can be performed to alleviate the symptoms of negative dysphotopsia. 

An IOL with a large optic may avoid the symptoms of negative dysphotopsia. 

The patient continued to be nervous about surgery in her fellow eye, asking me for promises that the same phenomenon would not occur again. Eventually she underwent uncomplicated surgery in April 2013. On postoperative day 1, she had a UCVA of 20/20 and no complaints of negative dysphotopsia. To date, she has remained symptom-free in her right eye. The dysphotopsia persists in her left eye, but she reports that she can cope with it. 

CONCLUSION 

When the Softec HD Oval is implanted in the capsular bag, its large overall length causes it to be positioned farther back than shorter IOLs. This design factor, together with the oval shape of the lens optic, have the potential to enhance visual outcomes. The optic of the Softec HD Oval is wide enough to avoid light scatter and gives patients clear, crisp vision. n 

Jeremy Kieval, MD, is in private practice at Lexington Eye Associates, Lexington, Massachusetts. Dr. Kieval states that he has no financial interest in the products or companies mentioned. He may be reached at tel: +1 781 862 1620. 

1. Trattler WB, Whitsett JC, Simone PA. Negative dysphotopsia after intraocular lens implantation irrespective of design and material. J Cataract Refract Surg. 2005;31:841-845. 

2. Davison JA. Positive and negative dysphotopsia in patients with acrylic intraocular lenses. J Cataract Refract Surg2000;26:1346-1355. 

3. Masket S, Fram NR. Pseudophakic negative dysphotopsia: Surgical management and new theory of etiology. J Cataract Refract Surg. 2011;37:1199-1207. 

4. Vamosi P, Csakany B, Nemeth J. Intraocular lens exchange in patients with negative dysphotopsia symptoms. J Cataract Refract Surg. 2010;38:418-424. 

The literature on negative dysphotopsia is growing, but currently there is no way to distinguish patients who will be symptomatic from those who will be dysphotopsia-free after surgery.

- Cynthia Matossian, MD, Matossian Eye Associates

A 'mini-monovision' approach with bilaterally implanted Softec HD IOLs demonstrated positive results.

Compiled by Callan Navitsky, Associate Editor; and Steve Daily, News Editor
IOLs available in 0.25 D increments with a labeled manufacturing tolerance increased the percentage of
patients within ±0.25 D of the targeted refraction to a statistically significant and clinically meaningful
degree compared with unlabeled IOLs available in 0.50 D increments, according to a study in the
Journal of Cataract & Refractive Surgery.1

In total, 118 eyes underwent cataract surgery and implantation of an IOL available in 0.25 D increments
and labeled with a manufacturing tolerance of ±0.11 D (n=67) or an IOL available in 0.50 D increments
without a labeled manufacturing tolerance (n=51).

Based on the SRK-T formula, the mean error of prediction after optimization was -0.03 ±0.35 D
(standard deviation) in the labeled group and -0.05 ±0.46 D in the unlabeled group (P=.64). The mean
absolute error of prediction was statistically significantly smaller in the labeled group (0.26 ±0.23 D)
than in the unlabeled group (0.37 ±0.28 D; P=.04). The mean and absolute errors were not statistically
significantly different with the Holladay 1 or Hoffer Q formula. Sixty-three percent of patients in the
labeled group and 43% in the unlabeled group (P=.03) were within ±0.25 D of the prediction error;
84% and 69%, respectively, were within ±0.50 D (P=.06).

1. Zudans JV, Desai NR, Trattler WB. Comparison of prediction error: labeled versus unlabeled intraocular
lens manufacturing tolerance. J Cataract Refract Surg. 2012;38(3):394-402.