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Posterior Chamber Phakic Intraocular Lenses to
Correct High Myopia: A Comparative Study
Between Staar and Adatomed Models
José L. Menezo, MD, PhD; Cristina Peris-Martínez, MD; Angel Cisneros, MD, PhD;Rafael Martínez-Costa, MD, PhD ABSTRACT
Adatomed group (5/12; 41.66%) than in the Staar
PURPOSE: To determine the feasibility of using
group (2/12; 16.7%). Anterior subcapsular cataract
posterior chamber phakic intraocular lenses
was higher in the Adatomed group (4/12; 33.3%)
(PIOLs) to treat high myopia, comparing two dif-
than in the Staar group (3/12; 25%).
ferent models, Staar and Adatomed.
CONCLUSIONS: There was a higher incidence of
METHODS: Twenty-four eyes from 12 patients
lens decentration and anterior subcapsular
were studied prospectively. A phakic Staar IOL was
cataract in the Adatomed group than in the Staar
implanted in one eye of each patient, and the other
group. [J Refract Surg 2001;17:32-42]
eye received a phakic Adatomed IOL. Patients with
uveitis or ocular trauma prior to ocular surgery,
diabetic retinopathy, or capsular pseudoexfoliation
were excluded. The mean preoperative spherical
Europe, and appears to be more frequent in equivalent refraction was -16.00 ± 5.05 D for the
women.1 The different refractive surgical Staar group and -15.39 ± 2.83 D for the Adatomed
techniques developed to date to treat myopia group. Average follow-up was 32.4 months (range,
include both intraocular procedures and methods 19 to 46 mo) for the Adatomed group and
that change the shape of the cornea.2 Corneal surgi- 18.3 months (range, 11 to 21 mo) for the Staar group
and included evaluation of intraocular pressure,
cal options include keratomileusis3, excimer laser intraocular lens pigment deposits, lens decentra-
surgery, ie, photorefractive keratectomy (PRK)— tion, anterior subcapsular cataract, and visual
either superficial or intrastromal (laser in situ ker- atomileusis, [LASIK])—and radial keratotomy. The RESULTS: Spectacle-corrected and uncorrected
intraocular procedures comprise lens extraction visual acuity improved in all eyes in both groups.
No statistically significant differences in visual
with or without implantation of an intraocular lens acuity gain were observed with the two materials
(IOL), and IOL implantation in phakic eyes in both (Student t-test, P = .08 for the Staar group and
the anterior and posterior chamber. The posterior P = .6 for the Adatomed group), although the gain in
chamber phakic intraocular lenses (PIOLs) for high visual acuity was somewhat greater with the Staar
myopia, also known as pre-lens IOLs4, are from two PIOLs. The difference in mean intraocular pressure
before surgery and at last follow-up was 1.5 mmHg
types of material: silicone (silicone lenses are cur- for the Staar group and 2.3 mmHg for the Adatomed
rently not on the market) and a copolymer, hydrox- group (P = .36). The incidence of lens pigment
deposits was the same in both groups (41.66%), with
HEMA is a hydrogel, a polymer with a high deposits in 5 of the 12 eyes in both groups. The inci-
hydration capacity (over 20%), although it does not dence of lens decentration was higher in the
dissolve in water. Its main monomer is 2-hydrox-yethylmethacrylate, which can copolymerize withacrylic polymers in aqueous solution to yield a softand elastic polymer. Hydrogels are rigid when dehy- From the Department of Surgery, University of Valencia, School of drated and become soft and elastic only upon hydra- Medicine, Valencia, Spain (Menezo, Martinez-Costa), Department of tion. Alterations in the polymerization process may Ophthalmology, University Hospital "La Fe," Valencia, Spain (Menezo,Peris-Martínez, alter the optical properties of the material. Its Oftalmológica del Mediterráneo, Valencia, Spain (Menezo). refraction index is 1.43, with a relative density of The authors have no proprietary interest in the development or mar- 1.16. The hydrogel is less rigid than silicone and keting of this or a competing instrument, drug, or piece of equipment. Correspondence: José L. Menezo, MD, PhD, La Fe University contains 38% water.5 This increased hydrophilia Hospital, Department of Ophthalmology, Avda. Campanar, 21, 46009 makes it softer and therefore less traumatic to the Valencia, Spain. Tel: 34.96.3868767; Fax: 34.96.398732. corneal endothelium than silicone. On the other Received: December 6, 1999Accepted: November 1, 2000 hand, its greater biocompatibility allows for a more Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
prolonged permanence within the eye. The presentstudy investigates the feasibility of using posteriorchamber PIOLs to treat high myopia, and comparesthe Staar lens and the Adatomed lens.
PATIENTS AND METHODS
12 adults treated in the Service of Ophthalmology(La Fe University Hospital, Valencia, Spain)received one Staar lens (STAAR Surgical AG,Nidau, Switzerland) for myopia that had remainedstable for at least 2 years. Stability was defined asthe absence of variation in spherical equivalentrefraction greater than 0.50 diopters (D). Thepatients selected had previously been implantedwith an Adatomed lens in the contralateral eye;mean time from Adatomed to Staar lens implanta-tion was 19.4 months (range, 14 to 26 mo). The peri-od during which the Adatomed lenses were implant-ed was from June 1994 to June 1997. Mean averagefollow-up was 32.4 months (range, 19 to 46 mo) forAdatomed PIOLs, and 18.3 months (range, 11 to21 mo) for Staar PIOLs. All lenses (both Adatomedand Staar) were implanted by the same surgeon Figure 1. Schematic drawing of the Chiron-Adatomed posterior
(JLM), following informed patient consent in all chamber phakic lens for high myopia. The optic is 5.5 mm indiameter.
cases. Patients had clear crystalline lenses, with noevidence of cataract previous to surgery. Patientswith uveitis, ocular traumas, prior ocular surgery,diabetic retinopathy, or capsular pseudoexfoliation lenses from -3 to -20 D. The posterior chamber Staar PIOL has undergone many modifications in design.
The Staar lens is known as an implantable con- Most lectures at meetings about the Staar lens refer tact phakic IOL has the trade name, “implantable to versions V1 to V7. The models used in this study contact lens” (ICL) (Deitz M. Lens potential looks were the Staar ICM 120V2 to V4 (V2 in three eyes, promising. Ophthalmology Times 1995; November: V3 in four eyes, and V4 in five eyes).
13-19). Skorpik and colleagues described it as a fold- able collagen-Collamer lens for implantation in the (Adatomed 094M-1) comprises a boat-shaped single piece lens with plane haptics composed of polydi- Weghaupt H, Zehetmayer M. Clinical results with a methylsiloxane—a thermostable high grade silicone posterior chamber implantable foldable collagen col- elastomer with a low water content (hydrophobic).
lamer lens for correction of high myopia.
The posterior surface of the optics is concave, with a Investigative Ophthalmology and Visual Science curvature similar to that of the anterior capsule of 1996;12(suppl):321); Zaldivar6 used the same ini- the lens and with a radius of 9.9 mm. The posterior tials (ICL) to mean an “intraocular contact lens.” surface of the optic is formed in such a way that it The Staar implant is a one-piece, soft, elastic, and touches the anterior natural lens curvature (the hydrophilic collagen/HEMA copolymer (Collamer) Staar lens is made to provide a space between the IOL (Staar ICM 120V) composed of a polymer and two surfaces—the posterior chamber PIOL and porcine collagen (less than 0.1% collagen). The lens anterior surface of the natural lens—so that they do is a single piece or monoblock and measures not touch, but allow a fluid exchange between 6 mm in width; it comes in three different diameters them). The anterior curvature is also concave, with (12.0, 12.5, and 13 mm length) for different eye a radius depending on the dioptric power. The diam- sizes. It has a central convex-concave optic zone eter of the optic zone is 5.5 mm. The haptics are 4.5 to 5.5 mm in diameter (depending on the model 0.18 mm thick and are positioned in the ciliary and dioptric power), and is introduced by means of a sulcus. The lens comes in lengths between 10.5 and Staar microinjector. Available powers are for myopic 12 mm (with stepwise increments of 0.5 mm).
Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
Properties of Adatomed and Staar
Clinical Data Used to Calculate PIOL
Phakic Intraocular Lenses
Power (Van der Heijde Formula*)
Adatomed
Standard
Deviation
with F’ = F + F’ and F’ = F /(1 - t.F ), where F of the IOL, F the power of the cornea, F’ the spectacle correction (Fs) at corneal vertex, d the location of the IOL, t the vertex distance of spectacles, and n the refractive power of the that developed by van der Heijde8 are identical. Theparameters required for calculation with the latter formula are indicated in Table 2. After processingthis information, we obtained the dioptric power for The two types of PIOLs to correct high myopia the lens to implant and the possible residual The mean preoperative spherical equivalent The length of Adatomed lens implanted was refraction for the Staar group was -16.00 ± 5.05 D determined based on the patient’s horizontal (range, -11.50 to -28.00 D) and for the Adatomed corneal diameter (white-to-white). The size of the group, -15.39 ± 2.83 D (range, -10.50 to -18.25 D).
PIOL was horizontal corneal diameter plus 1 mm, A complete ophthalmological examination was rounded to the nearest 1-mm increment. Corneal performed for all patients, including anterior seg- diameter was measured preoperatively with the ment and retina examination. In seven eyes with computerized calipers on the videokeratoscope high risk peripheral retinal degenerations, argon (EyeSys). The goal was to implant a PIOL of slight- laser prophylactic photocoagulation was performed.
ly larger size than the ciliary sulcus to promote Anisometropia was observed in seven eyes (29.16%) and amblyopia in two eyes (8.3%). Anterior chamber Determination of Staar lens power was per- formed using a proprietary formula. The indepen- dent variables in the formula are preoperative spherical equivalent refraction, keratometric power, Ultrasonic; DGH Technology Inc., St. Louis, MO).
vertex distance, actual anterior chamber depth, and Central keratometry was measured over two princi- corneal thickness. The final power calculations pal meridians, employing a calibrated Haag-Streit incorporated the surgeon’s (JLM) personal constant.
keratometer (Haag-Streit, Bern, Switzerland). The Posterior chamber PIOLs were also sized by length.
power of the Adatomed IOL was determined with Horizontal limbal white-to-white measurement plus the MYOPIOL program, provided by the Adatomed 0.5 mm was used to determine the IOL length.
GmHB company. Calculations were based on four However, if a specific power in the white-to-white models of lenses and eight refractive surfaces stud- measurement plus 0.5 mm in length was not ied by Haigis to establish the algorithm, and afford available, the actual white-to-white measurement results close to emmetropia.7 The results for plus 1 mm was used to determine the length of the emmetropia produced by other algorithms such as Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
One hour before the operation, the pupil was applied every 12 hours, and 1% dexamethasone and dilated with a mydriatic cocktail (2% homatropine, 3% gentamicin every 6 hours after the first postop- 2% tropicamide, and 2.5% phenylephrine), and a erative day. The doses of these drugs were tapered after 3 days, with total cessation after approxi- The clinical parameters evaluated for comparison Adatomed PIOL Surgical Technique
A partial thickness vertical limbal incision that Intraocular Pressure (IOP)—Intraocular pres-
measured 5.5 to 6 mm was made superiorly from the sure was determined preoperatively and after 11:30 to the 12:30 o’clock meridians. A temporal surgery using a Goldman tonometer mounted on a anterior chamber paracentesis was performed in all slit lamp. The average of three measurements was eyes to introduce a spatula to facilitate lens place- ment between the iris and anterior natural crys- Intraocular Lens Pigment Deposits—Lens
talline lens capsule. The anterior chamber was filled pigment deposits were evaluated after surgery on a with 1% sodium hyaluronate to maintain adequate qualitative basis only, considering the presence or intraocular pressure for facilitating implantation of absence of pigment in a luminous area 4 mm in the lens in the sulcus. The Adatomed lenses were diameter generated by the slit lamp on the lens sur- positioned using fine forceps. Following surgery, the face in the pupillary zone (without pharmaco- lens was left-centered in the 12/6 o’clock position. A logically induced pupil dilatation).
peripheral iridectomy was performed at the Lens Decentration—Lens decentration was
12:00 o’clock meridian to decrease the likelihood of defined when the slit-lamp visualization showed the iridotomy occlusion by the PIOL haptics. The limbal optic lens edge in the pupillary zone, without prior incision was then closed with five or six buried, pharmacological mydriasis. In the postoperative period, the optic was left-centered, with the hapticsin the 12/6 o’clock position—a fact that was verified Staar PIOL Implantation Procedure
under mydriasis immediately after surgery.
A clear corneal single plane, beveled 3.0-mm inci- Anterior Subcapsular Cataract—A single observ-
sion and superior paracentesis were performed. One er identified by ophthalmologic evidence anterior percent sodium hyaluronate was injected into the subcapsular opacification with a slit-lamp biomicro- anterior chamber. Under direct visualization with scope (Zeiss SLO-10) after adequate dilation. Mean the operating microscope, the PIOL was positioned average follow-up was 32.4 months (range, in the lens insertion cartridge. A 1.0-mm Merocel 19 to 46 mo) for Adatomed PIOLs, and 18.3 months microsurgical sponge was cut and placed behind the (range, 11 to 21 mo) for Staar PIOLs. Anterior sub- cartridge within the lens injector to protect the capsular opacification appearance was described, PIOL from the injector arm. The PIOL was then introduced into the anterior chamber with an injec- Visual Acuity—Distance visual acuity was deter-
tor cartridge designed by STAAR Surgical. The mined using Snellen-type optotypes of capital let- PIOL has two dimples on the anterior surface that ters of increasing size and located at a distance of serve as positioning holes. One hole is located next 5 meters from the patient. Near visual acuity was to the distal footplate, and the second is located next not evaluated in this study. Both spectacle-corrected to the proximal footplate. The peripheral plates of and uncorrected distance visual acuity were the PIOL were placed under the iris using a spatula determined before, and 6, 12, and 18 months after (P978B Deitz Tucker). Care was taken to avoid any surgery in both groups and expressed on a decimal central touch of the PIOL to the natural crystalline lens and any downward pressure. The IOL was cen-tered and the pupil was constricted with acetyl- Statistical Analysis
choline. Remaining viscoelastic was then removed Quantitative variables are expressed as the mean from the anterior chamber. The clear corneal and corresponding standard deviation (SD), and qualitative variables as relative percentages with Immediately after surgery, 20 mg of gentamicin respect to the total number of eyes. The statistical with 2 mg of betamethasone were applied to the analysis of the results was performed by paired subconjunctiva. The patients were given 80 mg of Student t-test for the comparison of means between prednisone orally on the day of surgery, and 40 mg groups. Statistical significance was considered on the second day. Topically, 10% homatropine was Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
The mean patient age was 32 ± 3.84 years (range, 28 to 41 yr). There were 10 females (83.3%) and twomales (16.6%). Mean follow-up was 32.4 months(range, 19 to 46 mo) for Adatomed PIOLs, and18.3 months (range, 11 to 21 mo) for Staar PIOLs.
The mean preoperative spherical equivalent refraction for the Staar group was -16.00 ± 5.05 D(range, -11.50 to -28.00 D) and for the Adatomedgroup, -15.39 ± 2.83 D (range, -10.50 to -18.25 D).
The mean amplitude of the anterior chamber was 3.52 ± 0.31 mm in the Staar group and 3.45 ±0.25 mm in the Adatomed group; the differencebetween the two PIOLs was not statistically signifi-cant (P = .61). The mean axial length of the eyeballswas 29.12 ± 1.97 mm in the Staar group and 28.94± 1.36 mm in the Adatomed group (P = .8).
Below are the clinical parameters evaluated to Figure 2. Pigment dispersion on the Staar lens 11 months after
establish comparisons between the two groups.
surgery, accompanied by anterior capsular fibrosis on the lens.
Intraocular Pressure
12.5 mm with a horizontal corneal diameter of Mean preoperative IOP was 17.5 ± 3.08 mmHg in 11.5 mm and the haptics in the right 12/6 o’clock the Staar group and 18.54 ± 1.07 mmHg in the position, a fact that does not explain the Adatomed group (P = .6, paired Student t-test).
Intraocular pressure was determined at day 1, 30, 90, and 180, and at 1, 2, and 3 years after surgery, Adatomed PIOL (25%, 3/12 eyes) versus the Staar depending on follow-up. Mean follow-up was PIOL (8.3%, 1/12 eyes). As indicated in the patients 32.4 months (range, 19 to 46 mo) for the Adatomed and methods section, the length of Adatomed lens group and 18.3 months (range, 11 to 21 mo) for the implanted was based on the patient’s horizontal Staar group. The difference between the preopera- corneal diameter (white-to-white). The size of the tive mean IOP and the mean IOP after surgery was Adatomed lens was chosen to be horizontal corneal 1.5 mmHg in the Staar group and 2.3 mmHg in the diameter plus 1 mm, rounded to the nearest 1-mm Adatomed group (P = .36, paired Student t-test).
increment. Staar lenses were also sized by length.
The horizontal limbal white-to-white measurement Lens Pigment Deposits
plus 0.5 mm was used to determine the PIOL The incidence of lens pigment deposits was the length. However, if a specific power in the white-to- same in both groups (41.66%), with deposits in 5 of white measurement plus 0.5 mm in length was not the 12 eyes in both groups (Fig 2). Pigmentation on available, the actual white-to-white plus 1 mm mea- the anterior capsule had two peculiar distributions: surement was used to determine the length of the coronary, like Vossius ring following blunt trauma (Fig 3A), and diffuse, similar to pigment dispersion We saw decentration more frequently in the Adatomed group (41.66%, 5/12 eyes) than in theStaar group (16.66%, 2/12 eyes). This suggests the Lens Decentration
implanted lens lengths were too short. However, in Lens decentration was more frequent in the the five eyes with Adatomed PIOL decentration, Adatomed group (41.66%, 5/12 eyes) than in the mean horizontal corneal diameter was 11.12 mm Staar group (16.66%, 2/12 eyes) (Fig 4). In no eye did and mean implanted lens length was 11.69 mm.
PIOL decentration become clinically manifest in the Even so, the two Staar lenses with decentration had form of monocular diplopia. But, in the eye shown in a mean horizontal diameter 12.34 mm and mean Figure 4, lens decentration produced high intensity implanted PIOL lens length was 12.65 mm. The nocturnal glare, halos, and optical aberrations that relationship between corneal diameters and the patient could not tolerate, necessitating removal implanted lens length was adequate for both lens of the Adatomed lens. Implanted PIOL length was types and does not explain the lens decentration.
Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
Figure 3. A) Coronary pigment dispersion over the Adatomed lens. B) Image shows pigment dispersion over the anterior face of the lens, of
no clinical significance.
Figure 4. Adatomed lens. A) Image shows a 2-mm decentration associated with highly diffuse anterior subcapsular opacification. B) The same
eye without pupillary dilation.
Figure 5. Peripheral opacification of the anterior capsule of the lens,
concentric to the optic zone of the Adatomed lens, 16 months after
surgery.
Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
Figure 6. Slit-lamp micrographs of a Staar lens 20 months after surgery. This intraocular lens type can be easily identified by the characteris-
tic positioning holes in the haptic portion of the lens (arrows). Pharmacologically induced pupil dilation. A) Central middle dense speckled
anterior subcapsular cataract, and B) the same anterior subcapsular cataract in retroillumination.
Figure 7. Histopathologic section of the anterior capsular natural
Figure 8. Mean uncorrected distance visual acuity in 12 eyes with
lens shows a hyalinized laminate structure covered by a smooth epithelium with thickened hyaline areas. Note pigment deposits.
Hematoxylin and eosin stain, 50X.
Anterior Subcapsular Cataract
ished visual acuity, depending on proximity to the Anterior subcapsular cataract was likewise more optical axis. In our series, no opacified lens had a frequent in the Adatomed group (33.33%, 4/12 eyes) visible space between the posterior surface of the than in the Staar group (25%, 3/12 eyes; two eyes PIOL and the natural lens, for either lens type. One with the V3 model and one eye with the V2 model).
patient, who developed anterior subcapsular On the other hand, anterior subcapsuar cataract in cataract and visual acuity of 0.1 in her right eye, the Adatomed group developed more rapidly com- required removal of the Adatomed PIOL and extrac- pared to the Staar group. The average cataract tion of the cataract. On histopathologic examina- tion, the anterior capsular natural lens showed a 20 months (range, 19 to 21 mo) whereas in the hyalinized laminate structure covered by a flat and Adatomed group it was 11 months (range, 9 to smooth epithelium with thickened hyaline areas 16 mo). We did not find differeces between the two groups in relation to the clinical appearance of theanterior subcapsular cataract. Cataract types found Visual Acuity Gain
were: peripheral concentric to the optical zone Spectacle-corrected and uncorrected visual acuity (Fig 5), central gray-white opacities in the pupillary improved in all eyes in both groups. Mean zone (Fig 6), and diffuse-dense. All of them dimin- uncorrected distance visual acuity before surgery in Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
eye in the Staar group. Three eyes (25%) in theAdatomed group versus seven eyes (58.3%) in theStaar group gained one line of spectacle-correcteddistance visual acuity; two eyes (16.6%) in the Staargroup and three eyes (25%) in the Adatomed groupgained two lines; three eyes (25%) in the Staargroup and no eyes in the Adatomed group gainedthree lines; one eye (8.3%) in the Staar group and noeyes in the Adatomed group gained four lines; andthree eyes (25%) in the Staar group and one eye(8.3%) in the Adatomed group gained five or morelines of spectacle-corrected distance visual acuity.
Subjectively, practically all patients complained of nocturnal halos to a greater or lesser degree—no Figure 9. Mean spectacle-corrected distance visual acuity in
12 eyes with the Staar and the Adatomed PIOLs.
differences were noted between one eye and theother (ie, no subjective differences between lenstypes).
the Staar group was 0.03 (1.52 logMAR ± 0.55;count fingers at 2 feet) and in the Adatomed group, Residual Spherical Equivalent Refraction
0.03 (1.50 logMAR ± 0.62). Following surgery, uncor- Prior to surgery, the mean spherical equivalent rected distance visual acuity improved in both manifest refraction in the Staar group was -16.00 ± groups and was slightly better in the Staar group 5.05 D (range, -11.50 to -28.00 D) and in the (Fig 8). The stabilization of uncorrected distance Adatomed group, -15.39 ± 2.83 D (range, -10.50 to visual acuity 6 months postoperatively in both -18.25 D). Six months after surgery, mean spherical groups is shown in Figure 8. At 18 months after equivalent manifest refraction in the Staar group surgery, uncorrected distance visual acuity in the was -1.12 ± 0.93 D and -1.41 ± 1.03 D in the Staar group was 0.5 (0.3 logMAR ± 0.17) and in the Adatomed group; 1 year after surgery in the Staar Adatomed group, 0.45 (0.35 logMAR ± 0.29).
group it was -0.82 ± 0.97 D and -1.02 ± 1.11 D in the Although the gain was slightly greater for the Staar Adatomed group; and 2 years after surgery in the PIOLs than with the Adatomed PIOLs, the differ- Staar group it was -0.73 ± 0.98 D and -0.85 ± 1.31 D ence was not statistically significant (P = .16, paired in the Adatomed group. The refractive differences Student t-test). At 18 months after surgery, uncor- were statistically significant for all follow-up exam- rected distance visual acuity was у0.5 (20/40) in inations before and after surgery (P = .002, paired nine eyes (75%) and 1.0 (20/20) in no eye of the Student t-test). However, there were no statistically Staar group; in comparison, in the Adatomed group, significant differences among values after surgery uncorrected distance visual acuity was у0.5 (20/40) with either type of lens (P = .02), which demon- in eight eyes (66.66%) and 1.0 (20/20) in no eye after strates refractive stability. In refractive terms, the results exhibited a tendency toward undercorrec- The mean spectacle-corrected distance visual tion. Overcorrection was not observed in any eye; six acuity before surgery in the Staar group was 0.49 eyes (25%) exhibited emmetropia, eight eyes (0.31 logMAR ± 0.19) and in the Adatomed group, (33.3%) were within ±0.50 D of emmetropia, and ten 0.45 (0.34 logMAR ± 0.20) (P = .64). At 18 months after surgery, spectacle-corrected distance visualacuity improved in both groups and was slightly bet- DISCUSSION
ter in the Staar group (0.78; 0.11 logMAR ± 0.09) One advantage of corneal refractive surgery is no than in the Adatomed group (0.66; 0.18 logMAR ± need for opening the eye.10 In contrast, its disad- 0.12) (P = .84). The paired Student t-test showed vantages include limited predictability, lack of that the visual acuity gain for the Staar lenses was reversibility, and the potential of cicatrization in the not statistically significant (P = .06). Figure 9 shows that spectacle-corrected distance visual acuity The extraction of the natural lens with or without stabilized in both groups 6 months after surgery.
implantation of an IOL is a controversial procedure After 18 months of follow-up, two eyes (16.6%) in the in refractive surgery, as it may increase the risk of Adatomed group failed to show any gain in retinal detachment, and the technique is invasive spectacle-corrected distance visual acuity, versus no and leads to an early loss of accommodation in Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
relatively young patients.11 On the other hand, it is these materials in application to posterior chamber able to provide stable correction of refractive lenses for the correction of high myopia. However, a defects, with high predictability12,13, and without number of authors have compared these two bioma- effects upon clarity of the central cornea.
terials in capsular sac lenses for cataract surgery, The correction of high myopia by implanting a with conflicting results. Thus, although some PIOL in phakic eyes is highly predictable, the PIOL authors report a greater biocompatibility when is removable, and does not alter accommodation.10 using HEMA over silicone26, other studies describe Our experience, over 4 years after implantation of posterior chamber PIOLs to correct high myopia, is In our experience, the two materials afforded a that they afford acceptable predictability and stabil- gain in both spectacle-corrected and uncorrected ity with regard to refractive outcome. Phakic distance visual acuity. This gain in visual acuity was intraocular lenses in high myopia patients have slightly greater for Staar lenses than for Adatomed been implanted in the anterior and posterior cham- PIOLs, although the gain in visual acuity was not bers. The complications observed as a result of statistically significant for either PIOL. The implantation of the first models of the Worst- improvement in visual acuity has been confirmed by Fechner iris claw lenses in phakic eyes made it nec- other authors27,28 who relate it to the disappearance essary to explant many of them.14 At present, of the minification effect of spectacles. One of the Artisan-style lenses of new design are being complications posed by the implantation of the pos- implanted to treat high myopia15-17, with good visu- terior chamber PIOL is the possibility of inducing al acuity results, but with a potential endothelial anterior subcapsular cataract as a result of either cell loss of as much as 10% after 3 years.17-19 We direct trauma or a later metabolic effect. In our have used both types, the initial Worst-Fechner lens series, anterior subcapsular cataract appears to (biconcave optic model) and the current model have been somewhat less frequent with the Staar Artisan (concave-convex design) of the iris-claw lenses (22.2%) than with the Adatomed lenses (33.3%). In any case, we obtained higher indices of The modern era of PIOLs for high myopia began anterior subcapsular cataract than other authors, in 1977 when Pearce20 designed a lens for implanta- such as Fechner (17.7% of cases with Adatomed tion in the posterior chamber. This was derived from lenses)25, Asseto10, and Castanera de Molina.28 This the idea of Ridley in 1949 of implanting lenses in the is probably attributable to the longer mean follow- posterior chamber—with evident advantages over up in our series. In this context, longer follow-up the anterior chamber.21,22 The idea of implanting a would be required to establish more precisely the IOL in the posterior chamber to correct high myopia lens opacification capacity of Staar PIOLs. The two in phakic eyes was developed in Russia, where in models have substantial differences in design, par- 1986, Fyodorov designed and began to implant sili- ticularly the vault. The purpose of the Staar lens is cone phakic lenses23,24—a procedure that avoided to vault the lens, with no contact with the posterior the endothelial decompensation problems posed by iris and the crystalline lens, to avoid the possibility phakic lenses implanted in the anterior chamber.
of late complications such as pigmentary dispersion Fechner also implanted the Adatomed lens, using syndrome and complicated cataract. The concern the term “posterior chamber myopia lens implanta- about whether the PIOL touches the natural lens is tion in phakic eyes” to describe the procedure.25 one that has received much attention. Deitz6 states The present study investigated the feasibility of that ultrasonography shows that the Staar PIOL using posterior chamber PIOLs to treat high vaults over the crystalline lens without touching it myopia, comparing two different models, the Staar (Deitz M. Lens potential looks promising.
and Adatomed. The exact models used in this study Ophthalmology Times 1995; November: 13-19).
were the Staar ICM 120V2, V3, and V4 (V2 in three However, Assetto10 reported that because of the con- eyes, V3 in four eyes, and V4 in five eyes). Model V3 tact between the posterior chamber PIOL with the was a nonvaulted flat design that produced most of crystalline lens and posterior iris, although not the cataracts (two of three cases of cataract were demonstrated in their study, the possibility of pig- with the V3 type). The V3 model is no longer in use, mentary loss and cataract formation must be but more vaulted models are currently being considered. Our study does not demonstrate by implanted. The Adatomed lens is no longer in clini- ultrasound biomicroscopy IOL-iris and IOL- cal use, having been withdrawn in 1998 because of crystalline lens touch, but clinical data determine high cataract incidence. We have found no refer- these problems occur with both types of posterior ences in the literature to comparative studies of chamber PIOLs. Slit-lamp biomicroscopy disclosed Journal of Refractive Surgery Volume 17 January/February 2001
Posterior Chamber Phakic Intraocular Lenses for High Myopia/Menezo et al
that no opacified eye had a visible space between the cerning long-term predictability with the Staar posterior surface of the posterior chamber PIOL and lenses. On the other hand, the parameters evaluat- the natural lens, with either lens type. In our series, ed may possibly lack the sensitivity required to decentration was more frequent in eyes receiving detect differences in viability between the two lens Adatomed lenses (41.66%) than those with Staar materials. Further comparative studies of new lenses (16.66%). Few studies have specifically Staar designs and new lens types (Adatomed- addressed posterior chamber PIOL decentration.
silicone lenses are not currently marketed and spe- Cisneros11 reported decentration in about 4% of all cific models of the Staar lens with no vault (V3) are implanted Adatomed lenses. This suggests that the not in use due to potential cataractogenesis) are implanted lens lengths were too short. However, in thus needed, based on different parameters, to the five Adatomed PIOL eyes with decentration, establish the relative utility of the materials. In our mean horizontal corneal diameter was 11.12 mm experience, the Adatomed lenses afforded a slightly and mean implanted lens length was 11.69 mm.
greater (although not statistically significant) Even so, the decentration for the two Staar lenses improvement in visual acuity gain over the Staar had a mean horizontal diameter of 12.34 mm and lenses, although the latter appeared to produce mean implanted PIOL length was 12.65 mm. The slightly fewer complications—with the exception of relationship between corneal diameter and implant- increased postoperative IOP and the presence of ed lens length was adequate for both lens types and lens pigment deposits, where the results were found did not explain the lens decentration. This increased to be similar for both types of lenses.
incidence is probably due to the longer follow-up Due to the paucity of peer-reviewed articles about period. Patients with lens decentration in both the position of the posterior chamber PIOL and its groups suffered optic complications such as relation to the adjacent structures in the posterior nocturnal halos and glare. As we suggest in the chamber, there still exists much controversy about results section, we have not found a relationship its long-term safety, mainly in regard to the among lens decentration, lens diameter, and white- intimate contact between the PIOL and the natural The intimate contact between the posterior cham- ber PIOL and the iris increases the possibility of REFERENCES
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