A retrospective analysis of the first Yemeni experience on Artisan phakic intraocular lens for the treatment of moderate and high myopia.

OBJECTIVES: To evaluate the outcome and safety of the iris-fixated Artisan phakic intraocular lens (PIOL) for the correction of moderate and high myopia.
MATERIALS AND METHODS: A retrospective non-controlled clinical study of the data of patients who underwent Artisan PIOLs between March 2006 and July 2008 was evaluated. Pre-operative examination included age, gender, refraction, uncorrected (UCVA) and best spectacle corrected (BSCVA) visual acuity, predictability and safety were analyzed. Post-operative time course ranged from 12 to 36 months.
RESULTS: An Artisan myopia lens was implanted in 62 eyes of 39 patients. The mean pre-operative spherical equivalent (SE) was -13.17 ± 5.62 D. The pre-operative myopia ranged from -4.5 to -24 D. Mean patient age was 25.44 ± 5.22 years. At last follow-up visit, residual SE was within ±1.00 D in 36 eyes (58.1%) and ±2.00 D in 56 eyes (90.3%). In the last visit UCVA was equal to or better than pre-operative BSCVA in 57 (91.9%) of the eyes. One eye (1.6%) lost one Snellen line, three eyes (4.8%) lost two or more Snellen lines and one eye lost vision (1.6%). Post-operative complications included anterior chamber reaction in one eye, rise in intraocular pressure in two eyes and retinal detachment in one eye.
CONCLUSION: When laser keratorefractive surgery is not an option, implantation of Artisan PIOL to correct moderate to high myopia results in a stable and good refractive result with few complications that must be kept in mind.

Introduction

Contact lenses and spectacles are the most common ways of correcting myopia; however, they have their own limitations. Laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are the most widely performed laser keratorefractive surgery procedures for the correction of myopia.[12] The results of laser keratorefractive surgeries are not good for myopia more than 10.0 D especially with glare and halo due to smaller optical zone.[3] the risk of keratectasia due to thinning of cornea[4] and the decrease in the best spectacle corrected visual acuity (BSCVA).[5]

At our refractive surgery unit, the rejection rate for LASIK stands at 25.4%[6] and for LASIK and PRK stands at 21%,[7] the most common reasons for rejection are suboptimal corneal thickness, high myopia, keratoconus and forme fruste keratoconus (keratoconus suspect).

Clear lens extraction (CLE) is also used to correct high myopia but it abolishes accommodation in young people and theoretically increases the chance of retinal detachment.[8]

Alternatives to the above procedures for the correction of moderate to high myopia include implantation of a phakic intraocular lens (PIOL).[9] PIOLs were introduced in the 1950s to correct refractive errors by Strampelli and Barraquer[10] and they are gaining widespread acceptance as the standard surgical procedure for moderate to high myopia. The advantages of this procedure are better quality of vision, potential reversibility of this procedure, preservation of accommodation and stability of refractive outcome.[1011]

They are grouped into three major subtypes : Iris-fixated, angle supported and posterior chamber PIOLs.[10] Angle supported has been abandoned in favor of the other PIOLs because they are associated with high rates of iris and iridocorneal angle complication and corneal endothelial loss.[11] Iris-fixated or iris-claw Artisan phakic IOLs (Ophtec BV, Groningen, The Netherlands) is the mostly used and provide satisfactory results in refractive surgery for correction of myopia, hyperopia and astigmatism.[12-14]

This retrospective non-controlled clinical study was performed to evaluate the clinical outcome and refractive results of iris-fixated Artisan PIOLs implanted in the management of patients with moderate to high myopia. To our knowledge, there is no Yemeni data published on iris-supported Artisan PIOLs (PubMed Search).

Materials and Methods

All eyes that were implanted with Artisan phakic IOL (Ophtec BV, Groningen, The Netherlands) at our refractive surgery unit in Yemen Magrabi Hospital in Sana’a between March 2006 and July 2008 were retrospectively analyzed.

These procedures were offered to patients seeking refractive surgery and were unsuitable for laser keratorefractive surgery due to suboptimal corneal thickness, suspicious corneal topography or high refractive error. Patient's age chosen was above 18 years with stable refractive error for at least 1 year, anterior chamber depth (ACD) more than 2.8 mm from the endothelium and intraocular pressure (IOP) less than 21 mmHg. This procedure was not offered for patients with glaucoma, uveitis, macular and retinal dystrophies or diseases. A signed written informed consent was taken from all patients before the procedure.

Pre-operative ocular examination included uncorrected visual acuity (UCVA), BSCVA before and after surgery, slitlamp examination (Haag Streit, Bern, Switzerland), Goldmann applanation tonometry (Haag Streit, Bern, Switzerland), corneal topography (Topography Modeling System -2 Topography system, Tomey Co.), pachymetry (Nidek UP-1000 Ultrasonic pachymeter, Gamagori, Japan) and ACD measurement (Nidek Co, Gamagori, Japan),

The pre-operative refraction was performed with and without cycloplegia (cyclopentolate hydrochloride 1.0%, Alcon-Cusi, Spain). Dilated fundus examination was done by the refractive surgeon and suspicious retinal cases were referred to the vitreoretinal unit.

The Artisan myopia lenses used in our patients were convex-concave (models 206 and 204) iris fixated IOLs, designed by Jan Worst and manufactured by Ophtec BV, Groningen, The Netherlands. All eyes were implanted with these models except one eye was implanted with toric Artisan and three eyes with Artiflex (foldable form of Artisan). The overall length of the lens is 8.5 mm. The optic is manufactured in diameters of 5 and 6 mm. The 6 mm lens is available from –3 to –15.5 diopter (D) in half D steps and the 5 mm lens from –3 to –23.0 D in half D steps. Both lens designs are exactly the same and differ only in optical diameter and effective optical zone size. The height of either lens does not exceed 0.95 mm.

The power of the lens was calculated with the Van der Heijde formula and was based on the refractive power of the cornea (mean corneal curvature, K) and the patients’ spherical equivalent (SE) refractive error (spectacle correction at 12.0 mm vertex).

One drop of 2% pilocarpine was instilled in the morning and 30 min prior to surgery. The surgery was performed under general anesthesia in all patients. Two side port incisions were made at 2 o’clock and 11 o’clock positions for the superior approach and at 1 o’clock and 5 o’clock positions for the temporal approach.

Intraocular acetylcholine chloride was injected (Miostat, Alcon, USA). The anterior chamber was filled with sodium hyaluronate solution (Oculocrom, Croma pharma Gmbh, Austria). A clear corneal limbal incision of 5 to 6 mm was made at 12 o’clock or 3 o’clock and in the cases of Artiflex a 3.2 mm limbal incision was made.

The Artisan myopia lens was introduced toward the 6 o’clock or 9 o’clock position, the lens was rotated using Sinskey hook, it was then held with a Shepard forceps (Katena Co., USA) at the outer part of the optic and the enclavation needle (Ophtec BV, Groningen, The Netherlands) passed through the paracenteces and iris tissue was enclavated. A peripheral iridectomy (PI) was performed with Vannas scissors (Katena Co., USA). After removing the viscoelastic from the anterior chamber the wound was closed with 10/0 nylon (Aurolab Co., India). Subconjunctival dexamethasone and gentamicin was given at the end of the procedure and the eye was padded. If the surgery was required to be done for both eyes, the surgery was done on the same session or on different sessions according to the patient request.

Post-operatively, prednisolone acetate eye drops 1% (Predforte, Allergan, Irvine, USA) four times daily tapering over four weeks and ciprofloxacin 0.3% (Ciloxan, Alcon, USA) eye drops four times daily for four weeks were used.

Follow-up examinations were performed in 1 day, 3 days, 1 week, 4 weeks, 3 months, 6 months and 12 months and annually thereafter. Patients with complications were examined more frequently.

Statistically significant differences between the means of the data samples were determined by Pearson correlation. We calculated the percentages for the data by utilizing the Excel 2007 program. Visual acuity (VA) data was converted to logMAR equivalents for statistical analyses and logMAR statistics were converted back into Snellen equivalents for the presentation of results.

The study was approved by the Research and Ethics committee of Yemen Magrabi Hospital, and the procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional or regional), and with the Helsinki Declaration of 1975, as revised in 2000. The risk of the surgery was fully explained to the patients in accordance with the Helsinki Declaration, and written informed consent was obtained.

Results

The study population includes 62 eyes of 39 patients with follow-up for at least 12 months but some were followed for up to 36 months. Age ranged from 18 to 36 years with a mean age of 25.44 ± 5.23 years [Table 1]. It included 14 males (35.9%) and 25 females (64.1%) and 23 patients (59.0%) had the surgery to both eyes. Majority of eyes had the superior wound approach (53.2%). Corneal topography details are shown in Table 2.

Table 1

Patients characteristics of the Artisan study in Yemen (2006-2008)

Table 2

Surgical characteristics of the Artisan study in Yemen (2006-2008)

Mean SE refraction was –13.17 ± 5.62 D. Pre-operative myopia ranged from –4.50 to –24.00 D. The ACD ranged from 2.80 to 3.93 mm and the mean ACD was 3.09 ± 0.34 mm. The axial length (AL) ranged from 22.61 to 32.50 mm and the mean AL was 28.03 ± 2.18 mm. The mean Artisan power implanted was –13.80 ± 4.79 D (range: –4.50 to –22.50 D). The mean pre-operative astigmatism was 1.38 ± 1.11 D (range 0.25 to 5.00 D). By 12 months, the mean post-operative astigmatism was 0.86 ± 0.72 D (P = 0.93). Table 3 shows the pre-operative characteristics for treated eyes.

Table 3

Pre-operative details of the Artisan study in Yemen (2006-2008)

At 12 months, the UCVA was 20/20 or better in 2 eyes (3.2%), 20/30 or better in 27 eyes (43.55%) and 20/40 or better in 34 eyes (54.84%). 34 eyes (54.8%) had UCVA of 20/40 or better. Twenty eight eyes (45.2%) had refraction within ±0.50 D, 36 eyes (58.1%) within ±1.00 D, 56 eyes (90.3%) within ±2.00 D [Figure 1].

Figure 1

Post-operative spherical equivalent refractive outcome

In terms of safety, BSCVA remained the same or improved in 57 eyes (91.9%). In one eye (1.6%) there was loss of one Snellen line [Figure 2]. The mean BSCVA improved from 20/70 pre-operatively to 20/30 post-operatively (P < 0.0005 r = 0.62). The Snellen equivalent medians for pre-operative BSCVA, post-operative UCVA and post-operative BSCVA were 20/50, 20/40 and 20/30 respectively.

Figure 2

Change in post-operative spectacle corrected visual acuity

The predictability was better in the lower-level of myopia. Of the 27 eyes with myopia between –5 to –10 D, 21 (77.8%) had post-operative refraction within ±1.00 D. In eyes with myopia ranging between –10.5 and –20 D, 23 out of 30 eyes (76.7%) had post-operative refraction within ±1.00 D and in those with myopia between –20.5 and –24 D, 4 out of 5 eyes (80.0%) were within ±1.00 D.

Post-operative complications encountered in the study group were; one eye developed anterior uveitis; one eye developed hyphema; and two eyes developed increase in IOP and were given anti-glaucoma medications [Table 2]. No eye developed dislocation or decentration of the Artisan lens, readjustment of centration, resuturing due to shallow anterior chamber or opening of the PI surgically or by YAG laser. One eye developed spontaneous rhegmatogenous retinal detachment (RRD) and was treated by our vitreoretinal surgeon but unfortunately developed cataract, which was treated with phacoemulsification and removal of the artisan lens but the eye developed severe uveitis and cylctitic membrane and ended with phthisis bulbi with vision of no perception of light [Table 2 and Figure 2]. Two patients reported night glare/halo.

Discussion

Moderate and high myopia are treated either by laser in situ keratomileusis (LASIK) or PIOL. LASIK results for myopia of more than –10.0 D are poor because of the risk of ectasia and poor visual quality.[1516]

This study replicates the efficacy and safety of Artisan PIOL implantation for the surgical management of moderate to high myopia.[12-1417-21]

In our study, the main outcome measure used to assess the effectiveness and safety of the artisan PIOL was uncorrected post-operative visual acuity (UCVA) and the maintenance or improvement in BSCVA compared to pre-operative BSCVA [Figure 2]. BSCVA remained the same or improved in 57 eyes (91.9%). The mean BSCVA improved from 20/70 pre-operatively to 20/30 post-operatively (P < 0.0005; r = 0.62). This improvement could be due to increase in optical quality of lenses and also magnification of lenses due to position of Artisan lenses relative to glasses.

At twelve months, 34 eyes (54.8%) achieved UCVA of 20/40 or better, which is better than an Iranian study (52%) (22) but less compared to 73.4% in Landesz et al. study;[17] 75% in the Indian study;[20] 79.6% in Benedetti et al. study.[18]

Other outcome measures used in this study included post-operative refraction within ±1.00 D, ±2.00 D and post-operative astigmatism. In our series, 36 eyes (58.1%) had post-operative refraction within ±1.00 D and this was comparable to some studies and worse than other published series. A refractive outcome within ±1.00 D was variably reported to be achieved in 60% (18), 68% (17), 68% (22), 82% (15), 90% (20), 93% (19). Post-operative refraction within ± 2.00 D was 90.3% which is similar to other studies of 92%.[22] The predictability was better in the lower-level of myopia, where 77.8% of the low myopes had post-operative refraction within ±1.00 D.

Mean pre-operative astigmatism was 1.38 ± 1.11 D and by twelve months, the astigmatism had reduced to 0.86 ± 0.72 D (P = 0.93). This was comparable to other studies, where pre-operative astigmatism of 1.12 ± 0.8 D had reduced to 0.82 ± 0.62 D.[23]

In this study, BSCVA remained the same or improved in 91.9%. One eye (1.6%) had loss of one Snellen line of VA and three eyes (4.8%) lost two or more Snellen lines. In comparison, the US food and drug administration (FDA) study showed that 5% of eyes lost one line and 95% had either no loss or gained one line or more.[19] In the Indian study, 11.6% lost one Snellen line and none had loss of two or more Snellen lines.[20] The mean BSCVA improved from 20/70 pre-operatively to 20/30 post-operatively (P < 0.0005 r = 0.62).

Several studies with Artisan iris-fixated lens implantation reported endothelial damage and cell loss over the years,[24] while in other studies no endothelial cell loss[21] or low endothelial cell loss was encountered.[20] We do not have specular microscope in Yemen and endothelial cell count was not studied.

Intra-operatively six eyes encountered hyphema, three eyes iris prolapse but no eye had traumatic cataract. All eyes that had surgical PI during surgery but post-operatively two eyes had IOP rise. In the two eyes the IOP was controlled medically and they were off medication within one month. Retained viscoelastics after implantation of PIOL or steroid responsiveness, could be a possible cause of IOP rise.[25] Intraocular pressure rise varied in various studies reaching up to 10% (20). Post-operative iritis was noted in one eye. Inflammatory reaction in various studies ranged from 0% (17), 3.3% (20) and as high as 45%.[21]

Glare or halos, which affect night vision and driving, is an important consideration in PIOL implantation. In our series, two patients experienced this complication, but did not bother them. Probably because Yemeni eyes have smaller pupil size compared to Caucasians, can be an explanation of why our patients did not complain of glare or halos. Other studies reported glare/haloes of 8%.[18]

An important sight threatening complication associated with PIOLs is retinal detachment. We did encounter one retinal detachment and unfortunately after retinal detachment surgery developed cataract followed by severe uveitis and phthisis bulbi. Six eyes (9.7%) had prophylactic laser for retinal holes, retinal flaps or lattice degeneration. The laser was done 1-2 weeks prior to lens implantation, to ensure good adhesion. However, the efficacy of this procedure as a routine in all patients to prevent post-operative retinal detachment is not documented.[26] Retinal detachment after myopia can be related to the disease itself or to the PIOL but it has not been proven.[2728]

Other complications of Artisan PIOL are rare. Cataract development,[29] PIOL dislocation,[20] corneal decopmensation,[30] change in configuration of pupil,[31] vitreous hemorrhage,[32] choroidal neovascularization,[33] endophthalmitis[34] were not seen in our group of patients.

The main limitation of this study is the retrospective data and all the data were collected from a single center. Other limitations are absence of evaluation of endothelial cell count pre-operatively and post-operatively because of the unavailability of specular microscope in Yemen.

Conclusion

The results of this study support the efficacy and safety of Artisan PIOL as a refractive surgical procedure for correction of moderate to high myopia. Both UCVA and BSCVA improved over the follow-up period with a few complications. Only one unfortunate patient lost his vision in one eye due to retinal detachment, which did not respond well to retinal detachment surgery.

This surgical technique has good results in moderate to high myopic patients that cannot be corrected by other methods but longer follow-up is necessary to monitor for other complications, namely cataract.