Iris-fixated phakic IOLs have been safely implanted in patients with myopia since 1986.1 The original biconcave iris-claw lens, developed in conjunction with Jan G.F. Worst, MD, of Holland, was updated in 1991 to feature a convex-concave shape. In 1998, the name of the lens changed to the Artisan (Ophtec BV, Groningen, Netherlands; Figure 1). In the following years, hyperopiaand astigmatism-correcting models became available. In 2003, a foldable model of the myopic Artisan, the Artiflex phakic IOL (Ophtec BV; Figure 2), was released in Europe. This lens may offer an advantage over the Artisan because it can be inserted through a smaller incision, with a decrease in surgically induced astigmatism and faster visual recovery.2
Iris-fixated phakic IOLs have provided stable and predictable visual results.3-7 Summarizing the long-term safety, loss of more than 2 lines of BCVA was detected in only 0% to 2.6% of eyes.3-7 Vision-threatening complications are rare with the modern Artisan and Artiflex lenses. Overall, the risk of complications is greater in phakic hyperopes than in phakic myopes, due to the shallower nature of the anterior chamber and smaller angle space. Postimplantation complications of iris-fixated phakic IOLs include pupil ovalization, IOL decentration, low-grade postoperative uveitis, endothelial cell loss, pupillary-block glaucoma, cataract, and retinal detachment; however, all are rare.3,8-10
To minimize these complications, an accurate and extensive preoperative examination of the patient is of utmost importance. The following sections review some important safety information with regard to implanting iris-fixated phakic IOLs.
PUPIL SIZE
The pupil plays an important role in lens centration, which is necessary for optimal optical lens function. The Artiflex has an optic diameter of 6 mm, whereas the Artisan is available with an optic diameter of either 6 mm (for IOL powers up to -15.50 D) or 5 mm (for IOL powers from -16.00 to -24.00 D). If the pupil size in mesopic lighting conditions exceeds the optical zone diameter of the phakic IOL, glare and higher-order aberrations could be markedly increased, resulting in decreased visual performance and patient satisfaction. This highlights the importance of performing preoperative pupil measurements in different lighting conditions.
Postoperatively, pupil size is reduced under scotopic conditions or medical mydriasis. Dick et al8 showed a mean postoperative scotopic pupil diameter decrease of 1.1 mm in myopic eyes, suggesting that the iris-fixated phakic IOL mechanically restricts pupil size changes under low-light conditions and could reduce the incidence of postoperative photic phenomena. Therefore, we believe that patients can still be eligible for phakic IOL implantation with a scotopic pupil size 1 mm larger than the optic of the lens.
ENDOTHELIAL CELL LOSS
The long-term effect of iris-fixated phakic IOLs on the
corneal endothelium remains a point of discussion. The
endothelial cell density (ECD) is known to decrease over
time, with a physiological rate of 0.6% per year after the
age of 18 years.11 Several short-term and a few recent
long-term studies have evaluated corneal ECD loss after
Artisan phakic IOL implantation, showing an average
ECD loss of 0.7% to 11.7% over 3 years.3,10,12 An anterior
chamber depth (ACD; measured from the epithelium) of
at least 3 mm is suggested as an adequate safety measurement
for implantation of the Artisan.3,10 Other safety
criteria that have been suggested to maintain a safe distance
to the endothelium include a 1.5 mm distance
from the edge of the phakic IOL to the endothelium13
and 2 mm from the center of the phakic IOL to the
endothelium,14 both of which can be measured using
anterior segment imaging (Figure 3).
In a recent study at our institution,15 we found that a shorter distance from the edge of the phakic IOL to the endothelium was associated with higher ECD loss. For example, for an edge distance of 1.37 mm, a linear mixedmodel analysis predicted an ECD loss of 0.98% per year. However, an edge distance of 1.15 mm resulted in a yearly ECD loss of 1.8%, and an edge distance of 1.59 mm resulted in a yearly loss of only 0.15%. Because the natural lens enlarges with age, the edge distance will decrease over time. To ensure a lifelong safe distance from the phakic IOL to the corneal endothelium, the distance between the edge of the lens and the endothelium should be monitored yearly using anterior segment imaging.
LENS RISE AND DECENTRATION
Two recent studies suggest that pigment dispersion on
the phakic IOL and subsequent inflammatory reactions
after iris-fixated phakic IOL implantation may be caused
by abnormal pressure on the iris.16,17 In this situation, the
iris is sandwiched between the crystalline lens and the
phakic IOL. To minimize chafing of iris tissue (ie, between
the phakic IOL and the natural lens) and cataract formation,
there should be enough space between the posterior
surface of the phakic IOL and the anterior surface of
the natural lens. An important preoperative distance
concerning these complications is the lens rise, which is
the distance from the anterior surface of the crystalline
lens to the horizontal line between the two angle recesses
(Figure 4). Baikoff et al17 suggest that the preoperative
lens rise should be less than 600 μm to avoid pigment
dispersion. This distance can be easily measured using an
anterior segment imaging device.
Lens decentration, which may develop spontaneously, is often due to an inadequate amount of iris tissue enclavation. However, decentration can also occur after blunt trauma, which may result in loosening of the haptic or haptics. The need for refixation depends on the amount of decentration, the patient's vision, glare complaints, and—most important—the risk of endothelial damage. We described a case series of 368 eyes in which nine eyes (2.4%) presented with late-onset sliding of the haptics through the iris tissue (Figure 5).18 Decentration was discovered at a mean follow-up of 4.8 years (range, 3–7 years). Mean downward decentration was 0.28 ±0.15 mm. The distance from the edge of the phakic IOL to the corneal endothelium was measured using anterior segment optical coherence tomography (OCT), with mean edge distances measured on the nasal, temporal, superior, and inferior sides of 1.71 ±0.30 mm, 1.86 ±0.31 mm, 1.86 ±0.31 mm, and 1.58 ± 0.34 mm, respectively. Mean enclavated iris tissue on the nasal and temporal sides was smaller after decentration when compared with that directly after surgery (P =.033 and P =.017, respectively). Shifting of the haptics did not result in decreased UCVA or BCVA, and there were no glare complaints. Refixation was not indicated in any of the patients; however, careful follow-up will be required to detect early ECD losses.
CONCLUSION
Iris-fixated phakic IOLs safely and effectively correct
myopia, hyperopia, and astigmatism when strict inclusion
criteria for implantation are applied. In addition to
yearly ECD counts, it is important to perform anterior
segment imaging to evaluate the distance from the phakic
IOL to the endothelium and crystalline lens to make
sure these lenses will be safe in the long term.
Muriel Doors, MD, is a resident in the Department of Ophthalmology, Maastricht University Medical Center, Netherlands. Dr. Doors states that she has no financial interest in the products or companies mentioned. She may be reached at tel: +31 43 3877346; fax: +31 43 3875343; e-mail: muriel.doors@mumc.nl.
Rudy M.M.A. Nuijts, MD, PhD, is an Associate Professor of Ophthalmology in the Department of Ophthalmology at Academic Hospital, Maastricht, Netherlands. He is a member of the CRST Europe Editorial Board. Dr. Nuijts states that he has no financial interest in the products or companies mentioned. He may be reached at e-mail: rudy.nuijts@mumc.nl.
