Download Posterior Chamber Phakic Intraocular Lens for Hyperopia of +4 to +

Posterior Chamber Phakic Intraocular
Lens for Hyperopia of
+4 to +11 Diopters
Jonathan M. Davidorf, MD; Roberto Zaldivar, MD; Susana Oscherow, MD
ABSTRACT
PURPOSE: To examine the efficacy, predictability, stability, and safety of posterior chamber phakic
intraocular lens (IOL) implantation in eyes with
high hyperopia.
METHODS: We analyzed the results of 24 eyes
that received a posterior chamber hydrogel-collagen plate phakic IOL (Staar Collamer Implantable
Contact Lens, ICL) for the correction of hyperopia
with the goal of emmetropia. Mean follow-up was
8.4 months (range, 1 to 18 mo).
RESULTS: The mean preoperative spherical
equivalent refraction was +6.51 ± 2.08 D (range,
+3.75 to +10.50 D). Mean postoperative spherical
equivalent refraction at last examination was -0.39
± 1.29 D (range, +1.25 to -3.88 D), with 79% (19 eyes)
within ±1.00 D and 58% (14 eyes) within ±0.50 D of
emmetropia. Postoperative uncorrected visual acuity at last examination was 20/20 or better in 8%
(two eyes) and 20/40 or better in 63% (15 eyes). A
gain of two or more lines of spectacle-corrected
visual acuity was seen in two eyes (8%) at last examination. One eye (4%) lost two or more lines of spectacle-corrected visual acuity due to progressive
neovascular glaucoma initiated by early postoperative pupillary block.
CONCLUSION: Posterior chamber phakic IOL
implantation with the Staar Collamer plate lens is
an effective method for correcting high hyperopia.
Large, patent iridotomies are important in hyperopic eyes to lower the risk of postoperative pupillary block. Improved phakic IOL power calculation
formulas will refine predictability of refractive outcome. [J Refract Surg 1998;14:306-311]
From Instituto Zaldivar, Mendoza, Argentina.
The authors have no proprietary interest in the materials presented.
Correspondence: Jonathan M. Davidorf, MD, 7230 Medical Center
Drive, Suite 201, West Hills, California 91307. Tel: (818) 883-0112; Fax:
(818) 883-2767; Email: [email protected] or Roberto Zaldivar, MD,
Instituto Zaldivar, Av. Emilio Civit 685, 5500 Mendoza, Argentina.
Tel: 54 61 293 222; Fax: 54 61 380 350.
Received: July 18, 1997
Accepted: February 26, 1998
S
urgical treatment for hyperopia currently
includes clear lens extraction with IOL implantation and corneal refractive techniques, such as
laser thermal keratoplasty (LTK), deep lamellar keratotomy, hyperopic automated lamellar keratoplasty
(ALK), photorefractive keratectomy (PRK), or laser in
situ keratomileusis (LASIK).1-7 Clear lens extraction
faces the problem of loss of accommodation, and is
therefore more suitable for presbyopic patients. Of
current corneal refractive procedures, LASIK has
shown the most promise. However, in the treatment
of high hyperopia, large amounts of cornea must be
ablated, small effective optical zones (at times less
than 3.0 mm) are created, and the predictability and
stability of the procedure begin to diminish (Davidorf
JM. Laser in situ keratomileusis after the learning
curve. Highlights of the ASCRS 1997 Annual Meeting, Ophthalmology Interactive, Boston, MA, 1997).
In addition, resultant optical aberrations often diminish the quality of postoperative vision. We currently
perform LASIK on hyperopes with spherical equivalent refractions from +1 to +5 diopters (D). Although
anterior chamber phakic IOLs have demonstrated
good results in the treatment of myopia, they are not
yet available for implantation into the small anterior
segment of hyperopic eyes.8-10
In December 1993, we began implanting the Staar
Collamer posterior chamber phakic IOL (trade
named the Implantable Contact Lens, ICL) for the
correction of high myopia. After witnessing good efficacy, safety, and stability in our initial cases, we
began, in March 1994, implanting this thin plate lens
into eyes with hyperopia of greater than +3.50 D. We
present here our initial 24 eyes.
Posterior Chamber Phakic IOL for Hyperopia of +4 to +11 Diopters/Davidorf et al
PATIENTS AND METHODS
Intraocular Lens
The Staar Collamer posterior chamber phakic
IOL (Staar Surgical AG Nidau, Switzerland) is
made of a porcine collagen/HEMA copolymer (less
than 0.1% collagen) with a refractive index of 1.45 at
35° C. Its design has been described.11 Because the
phakic IOL has undergone modifications since we
began implanting the lens, several distinct lens
designs were implanted during this study. The predominant model used was the IC2020 (12 eyes). In
addition, five eyes received the IC2020-P series phakic IOL, five received the IC2020-H series phakic
IOL, and two eyes received the IC2020 DES-1 model
phakic IOL.
Patient Selection
From March 1994 to August 1996 we implanted
posterior chamber phakic IOLs into 24 eyes of 19
patients with high hyperopia (spherical equivalent
refraction more than +3.50 D). Mean preoperative
spherical equivalent refraction was +6.51 ± 2.08 D
(range, +3.75 to +10.50 D). Mean age at the time of
surgery was 36 years with a range of 26 to 45 years.
Exclusion criteria included previous intraocular
surgery, nanophthalmos, visually significant
cataract, glaucoma, proliferative diabetic retinopathy, and retinal breaks. Patients with advanced systemic disease were also excluded from the study.
Preoperative examination included uncorrected
visual acuity, spectacle-corrected visual acuity with
manifest and cycloplegic refractions, keratometry,
corneal topography, pachymetry, specular microscopy, Ascan ultrasonography, slit-lamp biomicroscopy,
applanation tonometry, and dilated funduscopy.
Visual acuity and cycloplegic refraction are the only
preoperative data reported for all eyes.
Intraoperative arcuate transverse keratotomies
for astigmatism were performed on two eyes. A second refractive procedure to correct residual refractive error after phakic IOL was performed in seven
eyes. The refractive and visual acuity data prior to
the secondary procedure are presented.
Surgical Technique
The surgical technique has been described.11 To
decrease the incidence of postoperative pupillary
block, in June 1994 we began placing peripheral
laser iridotomies at least 4 days preoperatively.
Until August 1995, patients received a single superior iridotomy; subsequently, we began placing two
superior iridotomies positioned 60° to 90° apart in
order to decrease the likelihood of iridotomy occlu-
sion by the phakic IOL haptics. Iridotomies were
250-500 µm in diameter and located superiorly (covered by the upper eyelid) in the peripheral iris.
From June 1994 until July 1996, only the Nd:YAG
laser was used (single burst, 3 to 10 mJ). Subsequently, we began using the argon-green laser prior
to applying the Nd:YAG spots in order to decrease
iris bleeding and pigment dispersion on the phakic
IOL (Argon settings: 50 µm spot size, 650 to
1000mW power, and 0.2 to 0.5 sec duration).
Lens power calculations were performed with formulas developed by Staar. The independent variables in the formula were preoperative spherical
equivalent spectacle refraction, vertex distance,
average keratometric power, corneal thickness, and
central anterior chamber depth. Early experience
demonstrated a tendency of the formula to lead to
undercorrections for hyperopic eyes. The final choice
of lens power was therefore determined following
adjustments based on target postoperative refraction, lens availability, and the surgeon’s experience.
The length of phakic IOL implanted was based on
the patient’s horizontal corneal diameter (white-towhite). The size of the phakic IOL was horizontal
corneal diameter plus 0.5 mm, rounded to the nearest 0.5-mm increment. Corneal diameter was measured preoperatively with the computerized calipers
on the videokeratoscope (EyeSys Technologies,
Houston, TX). The goal was to implant a phakic IOL
of slightly larger size than the ciliary sulcus to promote anterior IOL vaulting and secure fixation.
Although the surgical maneuvers are identical in
myopic and hyperopic eyes, the shallower anterior
chambers of the hyperopic eyes solicited extra care
during phakic IOL insertion in order to avoid contact with the corneal endothelium.
Secondary Refractive Procedures
Residual refractive errors were treated with
refractive or arcuate transverse keratotomy in three
eyes, PRK in one eye, and LASIK in three eyes,
according to previously described techniques.12,13
The secondary refractive procedures were performed no sooner than 4 weeks following phakic IOL
implantation. Two eyes underwent removal of their
initial phakic IOL (Table).
Follow-up
Routine postoperative examinations were scheduled at 1 day, 1 month, 3 to 6 months, 12 months, 18
to 24 months, then every year after surgery. The
mean follow-up was 8.4 ± 3.6 months following phakic IOL implantation (range, 1 to 18 mo). The followup rate was 100% at 1 day and 1 month (24 eyes),
Posterior Chamber Phakic IOL for Hyperopia of +4 to +11 Diopters/Davidorf et al
Table
Perioperative Complications in 24 Eyes with a Posterior Chamber
Phakic IOL for Hyperopia
Complication
Pupillary block
Number of Eyes
3
IOL extraction
2
IOL decentration less than 1 mm
IOL decentration more than 1 mm
1
2
Comments
Two resolved with laser iridotomy; one developed progressive glaucoma (same
eye); no eyes since two preoperative iridotomies
One had phacoemulsification at time of IOL removal (same eye); one had no
further surgery
No recentration required
Recentration performed in one eye; one eye underwent IOL exchange
79% at 6 months (19 of 24 eyes that had surgery at
least 6 months prior to completion of the study), 80%
at 12 months (12 of 15 eligible eyes), and 67% at 18
months (two of three eligible eyes).
All follow-up examinations detailed subjective
complaints. Uncorrected visual acuity and spectacle-corrected visual acuity by manifest refraction
were elicited at each examination and are reported
for all eyes. Automated keratometry, applanation
tonometry, and slit-lamp microscopy were performed at each examination, and the significant
findings are reported. Phakic IOL vaulting, pigment
dispersion, and crystalline lens clarity were particularly documented. Pigment deposition on the phakic
IOL surface is reported for all eyes. Gonioscopy and
dilated funduscopy were performed as needed. Postoperative specular microscopy was performed on 11
eyes. Because of unreliable preoperative and postoperative measurements, the specular microscopy results
are not presented.
Data Analysis
Data forms were used to help standardize data
collection and analysis. Refractive outcome and
postoperative visual acuity were analyzed as measures of the efficacy of the procedure. Baseline
refractions (spherical equivalent refraction and
cylinder) and visual acuities (uncorrected visual
acuity and spectacle-corrected visual acuity) were
compared to the refractions and visual acuities at
the last examination. In examining refractive and
uncorrected visual acuity outcomes, the last refraction and uncorrected visual acuity prior to a secondary
refractive procedure were used.
Complications were analyzed as a measure of the
safety of the procedure. All potentially visually
threatening events were recorded (Table). A loss of
spectacle-corrected visual acuity of more than two
lines was considered significant. The frequencies of
phakic IOL-related subjective complaints persistent
after 1 month were documented.
Figure 1: Stability of spherical equivalent refraction. The spherical
equivalent refractions of the eyes with at least 12 months of followup, preoperatively and at 1, 6, and 12 months postoperatively. Only
eyes that did not undergo a second procedure during the 12 month
period are shown. Error bars indicate one standard deviation.
Refractive outcomes at 1, 6, and 12 months were
analyzed. Refractive outcomes of eyes with more
than 12 months follow-up were evaluated as a measure of stability of the refractive outcome. Eyes with
secondary refractive procedures during their first 12
postoperative months were excluded from this stability analysis.
RESULTS
Baseline Refraction Groups
Mean preoperative spherical equivalent refraction was +6.51 ± 2.08 D (range, +3.75 to +10.50 D)
and mean preoperative refractive astigmatism was
1.41 ± 1.01 D (range, 0 to 3.25 D).
Refractive Outcome
Mean postoperative spherical equivalent refraction at last examination was -0.39 ± 1.29 D (range,
+1.25 to -3.88 D) and mean refractive astigmatism
was 1.56 ± 1.47 D (range, 0 to 4.00 D). Postoperative
spherical equivalent refraction at last examination
was within ±1.00 D in 79% (19 eyes) and within
±0.50 D in 58% (14 eyes). Spherical equivalent
Posterior Chamber Phakic IOL for Hyperopia of +4 to +11 Diopters/Davidorf et al
Figure 2: Spectacle-corrected visual acuity (BSCVA) preoperatively
and uncorrected visual acuity (UCVA) postoperatively are presented
as percent of 24 eyes. The + notation indicates “or better,” eg, 20/20+
indicates 20/20 or better.
refraction stability is demonstrated in Figure 1. Of
the 12 eyes with at least 12 months follow-up, three
eyes (25%) demonstrated a change in spherical
equivalent refraction of greater than ±1.00 D at any
examination interval. Two eyes experienced a
myopic shift and one eye experienced a hyperopic
shift.
Visual Acuity
Preoperative uncorrected visual acuity was less
than 20/200 in 74% of eyes. No eyes had preoperative uncorrected visual acuity of better than 20/50.
Preoperative spectacle-corrected visual acuity was
20/40 or better in 83% (20 eyes) and 20/20 or better
in 21% (five eyes). Postoperative uncorrected visual
acuity at last examination was 20/40 or better in
63% (15 eyes) and 20/20 or better in 8% (two eyes,
Fig 2).
Figure 3 compares preoperative versus postoperative spectacle-corrected visual acuity (last available refraction). A gain of two or more lines of spectacle-corrected visual acuity was seen in 8% (two
eyes). One eye of one patient experienced a loss of
two or more lines of spectacle-corrected visual acuity due to secondary angle closure glaucoma (spectacle-corrected visual acuity was 20/30 preoperatively and 20/60 postoperatively at last examination).
Complications
Perioperative and postoperative complications
are detailed in the Table. The most common complication was early postoperative pupillary block,
which occurred in three eyes. Two of these eyes had
a single laser iridotomy placed preoperatively, and
the other eye did not have a preoperative laser iridotomy. In two of these three eyes, the pupillary
block was relieved with placement of two peripheral
laser iridotomies. In the third eye, progressive glau-
Figure 3: Change in spectacle-corrected visual acuity at last examination as percent of 24 eyes with loss or gain in Snellen lines of
visual acuity.
comatous optic nerve cupping developed despite
repeated laser iridotomies, two trabeculectomies,
and removal of the phakic IOL combined with phacoemulsification of the clear crystalline lens and
posterior chamber IOL implantation in the capsular
bag. Secondary angle closure developed due to neovascularization of the angle. At last examination, 18
months following phakic IOL implantation, spectacle-corrected visual acuity was 20/60 (three lines
worse than preoperative spectacle-corrected visual
acuity), and intraocular pressure was controlled (16
mmHg) on multiple medications.
Three eyes had their original phakic IOL
removed: the eye with neovascular angle closure
glaucoma, one eye with phakic IOL decentration,
and one eye with anterior chamber crowding (shallowing of the central anterior chamber on slit-lamp
examination and an inability to visualize the trabecular meshwork on gonioscopy). Of these, one had
a new, properly sized, posterior chamber phakic IOL
placed and has done well subsequently; the one with
angle closure glaucoma was just discussed. The
third eye had no lens implanted because the original
phakic IOL effected such severe overcrowding of the
anterior chamber. The spectacle-corrected visual
acuity returned to its preoperative level within 2
days after phakic IOL explantation.
There were no cases of corticosteroid-induced
intraocular pressure elevation, broken phakic IOL,
cataracts, sustained corneal edema, macular edema,
or retinal detachment. The mean amount of pigment
deposition on the phakic IOL surface appeared stable (mean less than 2+ at all examinations), and
there were no cases of pigment dispersion glaucoma.
Subjective complaints persistent after 1 month
included glare (two eyes), pain (two eyes), and
Posterior Chamber Phakic IOL for Hyperopia of +4 to +11 Diopters/Davidorf et al
decreased visual acuity (one eye). Complaints of
glare were seen in the two eyes with more than 1
mm of phakic IOL decentration; symptoms were
relieved upon phakic IOL recantation or exchange.
Complaints of pain and decreased vision occurred in
the eye with progressive glaucoma. The eye of the
other patient with complaints of pain had a mild
superficial epithelial keratopathy attributed to mild
dry eyes.
DISCUSSION
Myopic eyes that have relatively large anterior
segments are well suited for phakic IOL
surgery.16,19-21 Anterior chamber phakic IOLs may be
implanted without causing significant damage to
the corneal endothelium and well-positioned posterior chamber IOLs do not appear to induce
cataracts.11,18 In contrast, hyperopic eyes often have
relatively small anterior segments, which may make
phakic IOL surgery more difficult.16,19-22 The spectrum of hyperopia includes nanophthalmos, and
intraocular surgery in nanophthalmic eyes is associated with an increased risk of angle closure glaucoma, uveal effusion, and nonrhegmatogenous retinal
detachments.22,23 To date, anterior chamber phakic
IOLs have been unsuitable for use in hyperopic eyes.
By allowing a relative deepening of the anterior
chamber, clear lensectomy with IOL implantation
may be a good alternative to anterior chamber phakic IOL surgery for the treatment of high hyperopia,
and it has demonstrated good efficacy and safety.6,7,10 Limitations of clear lensectomy with IOL
implantation include problems of IOL power calculations, the potential need for implanting more than
one IOL (piggyback IOLs), and loss of accommodation.6,7,10,20-22
Posterior chamber phakic IOLs offer potential
advantages over clear lensectomy by preserving
accommodation. In addition, posterior chamber phakic IOLs offer a potential advantage over anterior
chamber models because, by virtue of their location
behind the iris, there should be less risk of phakic
IOL-corneal endothelium contact and subsequent
corneal edema.
Efficacy and Predictability
The posterior chamber phakic IOL dramatically
decreased the hyperopia in our study population.
Seventy-nine percent (19 eyes) achieved a postoperative spherical equivalent refraction within ±1.00 D
and 58% (14 eyes) within ±0.50 D of emmetropia at
the last examination. This compares favorably to the
predictability of our initial 124 eyes with high
myopia that received a posterior chamber phakic
Figure 4: Pigment on the phakic IOL surface, graded from 0 to 4+.
Mean values are shown at different postoperative examinations.
IOL: 69% (86 eyes) achieved a postoperative spherical equivalent refraction within ±1.00 D and 44%
(55 eyes) were within ±0.50 D of emmetropia.11 Limitations in predictability of posterior chamber phakic IOL surgery relate, in part, to choosing IOL powers based on spectacle corrections. The development
of more accurate lens power calculation formulas
should help improve the predictability of the procedure.
A good measure of efficacy in refractive procedures is a comparison of preoperative spectacle-corrected visual acuity to postoperative uncorrected
visual acuity. Figure 2 shows that 63% (15 eyes) had
20/40 or better postoperative uncorrected visual
acuity compared to 83% (20 eyes) with the same
level of spectacle-corrected visual acuity preoperatively.
The marked gain in spectacle-corrected visual
acuity that has been reported in high myopes following phakic IOL surgery8,9,11,14 was not observed
in our hyperopic population, with 8% (two eyes)
demonstrating a gain in spectacle-corrected visual
acuity at last examination (Fig 3). In our myopic
series, 36% (45 of 124 eyes) gained two or more lines
of spectacle-corrected visual acuity, largely due to an
elimination of the spectacle induced minification
experienced by these patients preoperatively.15,16
Safety
The 12.5% incidence of postoperative pupillary
block (three eyes) is more than double the 4.8% incidence of pupillary block observed in our previous
myopic series.11 We attribute this to postoperative
anterior segment crowding that can occur when
smaller hyperopic eyes receive a phakic IOL. We
have seen no cases of pupillary block since we began
placing two peripheral laser iridotomies 60° apart
Posterior Chamber Phakic IOL for Hyperopia of +4 to +11 Diopters/Davidorf et al
preoperatively. The progressive glaucoma (beginning with pupillary block and angle closure) that
developed in one eye emphasizes the importance of
taking measures to avert this complication and
identifying predisposed and affected eyes early. This
was the only eye in our series that experienced a
loss of two or more lines of spectacle-corrected visual acuity. One eye had the phakic IOL removed
because excessive vaulting of the IOL produced
anterior chamber crowding and caused concern for
angle closure. Phakic IOL removal was performed
without incident and spectacle-corrected visual acuity returned to its preoperative level.
The pigment deposition on the phakic IOL surface
was probably surgically related because the amount
of pigment was not progressive (Fig 4). There were no
cases of pigment dispersion glaucoma. We think that
increasing the time between laser iridotomy and phakic IOL implantation as well as implementation of
the non-rotational insertion technique help produce
less pigment deposition. We no longer dial-in the corners of the haptics; rather, each corner is individually positioned beneath the iris with an intraocular
hook, which minimizes surgical trauma.
Stability
Regression of the initial refractive result has
occurred after corneal refractive procedures in eyes
with high myopia or high hyperopia.12,13 In contrast,
excellent refractive stability has been demonstrated
in eyes with high myopia following phakic IOL
surgery with anterior chamber IOLs, silicone posterior chamber phakic IOLs, or silicone-collagen
copolymer phakic IOLs.8-11,19 We observed good stability of the spherical equivalent refraction to 12
months in this small series (Fig 1). Longer follow-up
in a larger number of eyes will help to better
address long-term stability.
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