Artiflex versus STAAR implantable contact lenses for correction of high myopia.

PURPOSE: To compare two phakic intraocular lenses, Artiflex and STAAR(®) implantable contact lens (ICL), in high myopia.
SETTING: Isfahan Ophthalmology Clinic, Iran.
MATERIALS AND METHODS: In a randomized, prospective clinical trial study, 40 eyes of 20 patients who came to Isfahan ophthalmology clinic to correct their refractive error were examined. Artiflex was inserted in 20 eyes and ICL in the other 20 eyes. After 1 year, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), contrast sensitivity, intraocular pressure (IOP), and specular microscopy of corneal endothelium were assessed in both the groups.
RESULTS: In this study, there was no statistical difference between UCVA, BCVA, IOP, cataract incidence, contrast sensitivity, and specular microscopy, 1 year after surgery. 40% of eyes in the Artiflex group developed anterior chamber cell and flare reaction 1 year postoperatively, but no patient in the ICL group developed the same. So, there is obvious difference in the rate of anterior chamber cell and flare reaction between these two groups.
CONCLUSION: These two lenses have similar outcomes except in the incidence rate of anterior chamber cell and flare reaction that is greater in the Artiflex group. So, these two lenses are safe with predictable outcome in treating high myopia.

RCT Entities:   Population Interventions Outcomes

Introduction

Refractive errors are one of the most common ophthalmologic problems. For resolving this, there are several therapeutic methods such as corrective spectacles, contact lenses, keratorefractive surgeries, intraocular lenses (IOLs), and clear lens extraction. There are many complications after keratorefractive surgeries of high refractive errors, such as glare, halo, and contrast sensitivity loss due to higher order aberration induced by keratorefractive surgery. The over flattening of the central cornea can cause higher order aberration.[1-3]

IOLs can correct high refractive errors without any change in the shape of cornea.[45]

Several types of phakic IOLs (pIOLs) are available, such as anterior chamber phakic IOLs (ACpIOLs) and posterior chamber phakic IOLs (PCpIOLs). An example of the ACpIOL is Artiflex; the implantable contact lens (ICL) or STAAR® lens is an example of a PCpIOL. The Artiflex is made of polysiloxane and the ICL (STAAR®) is made of a hydrophilic material known as Collamer.

In this article, we compare the two types of pIOLs, Artiflex versus STAAR®, for correcting high myopia.

Materials and Methods

This was a randomized, prospective clinical trial. This study was performed on 40 eyes of 20 patients with high myopia, seeking correction of their refractive error. Patients with underlying systemic diseases such as hypertension, diabetes mellitus, malignancies or other ocular diseases were excluded from the study. The procedure, advantages, probable complications and other therapeutic alternatives were described to all the patients. This study was performed after obtaining informed consent from the patients.

All the patients were over 20 years of age and underwent complete ophthalmologic examination. The best corrected and uncorrected visual acuities were similar between two eyes. The refractive error was –6 to –14 diopters, with the astigmatism up to –2 diopters. There was no anisometropia in the patients. The anterior chamber depth was greater than 3 mm in all the patients, determined ultrasonographically from the endothelial surface of cornea to anterior surface of the iris. Randomly, an Artiflex pIOL was inserted in one eye and an ICL (STAAR®) was implanted in the other eye with 2 weeks interval. This interval was chosen to prevent binocular complication of intraocular surgery or reaction to IOL material. All of the patients underwent surgery under local anesthesia, with small temporal incision (3.2 mm). A surgical peripheral iridectomy (PI) was performed in all patients and the incision was closed with corneal stromal hydration. Postoperatively, all the patients were followed at regular intervals (day 1, week 1, week 2, month 1, month 2, month 6, and year 1) to evaluate the outcomes and complication. After 1 year, all the patients were reevaluated. Visual acuities, intraocular pressure (IOP), intraocular inflammation, cataract formation, contrast sensitivity (3, 6, 12, 18 cycles per degree), and specular microscopy for corneal endothelium were assessed.

Results

All patients were between 26 and 29 years old (mean = 27 years). Ten patients were males and the other 10 were females.

Artiflex pIOL group: In this study, the Artiflex pIOL was inserted in 20 eyes. The mean postoperative sphere equivalent was –0.75 diopters in the ICL group and –0.84 diopters in Artiflex group. The postoperative mean cylinder power was lesser than –0.25 diopters in both groups. The preoperative uncorrected visual acuities (UCVA) were counting finger (CF) at 1 m for 12 eyes, CF at 2 m for 7 eyes, and CF at 3 m for 1 eye. The preoperative best corrected visual acuities (BCVA) were 10/10 for 10 eyes, 9/10 for 8 eyes, and 7/10 for 2 eyes. One year after surgery, the UCVAs were 10/10 for 12 eyes, 9/10 for 3 eyes, 8/10 for 3 eyes, and 7/10 for 2 eyes. The BCVAs were 10/10 for 17 eyes and 9/10 for 3 eyes.

There was a statistically significant difference between preoperative and postoperative UCVA in Artiflex group (P = 0.000). There was also a statistically significant difference between preoperative and postoperative BCVA in this group (P = 0.011).

STAAR® ICL group: For other eyes of 20 patients, we inserted ICL. Preoperative UCVAs were CF at 1 m for 13 eyes, CF at 2 m for 6 eyes, and CF at 3 m for 1 eye. Preoperative BCVAs were 10/10 for 10 eyes, 9/10 for 8 eyes, and 7/10 for 2 eyes. Postoperative UCVAs were 10/10 for 11 eyes, 9/10 for 6 eyes, 8/10 for 1 eye, 7/10 for 1 eye, and 6/10 for 1 eye. Postoperative BCVAs were 10/10 for 17 eyes and 9/10 for 3 eyes [Tables 1–4].

Table 1

The preoperative uncorrected visual acuity (Log MAR) of implantable contact lens and Artiflex group

Table 4

The postoperative best corrected visual acuity of implantable contact lens and Artiflex group

There was a statistically significant difference between preoperative and postoperative UCVA in the ICL group (P = 0.000). There was also a statistically significant difference between preoperative and postoperative BCVA in this group (P = 0.011).

There was no statistically significant difference between postoperative UCVA or BCVA between Artiflex and ICL groups (P = 0.786).

In assessing the IOP that was measured by Goldman tonometry, there was no significant difference of preoperative IOP between the two groups (P = 0.76). There was statistically significant difference between preoperative and postoperative IOP in Artiflex and ICL groups (P = 0.001) [Table 5]. There was no case of glaucoma or IOP greater than 21 mm Hg, 1 year after surgery. There was no statistical difference of IOP between two groups 1 year postoperatively (P = 0.604).

Table 5

The mean pre and postoperative intraocular pressure of implantable contact lens and Artiflex group. (mm Hg)

In assessing the crystalline lens opacity, there was one case of posterior subcapsular cataract 1 year after surgery in each group. There was no significant difference in cataract formation rate after surgery between the two groups (P = 1.0).

In assessing the status of the corneal endothelium by specular microscopy, no statistically significant difference of postoperative mean endothelial cell count and coefficient of variation (CV) between two groups was found (P = 0.72 and 0.25, respectively) [Table 6]. The hexagonal endothelial cell percent was similar between the two groups 1 year postoperatively (P = 0.73).

Table 6

The postoperative mean and standard deviation of endothelial cell count of implantable contact lens and Artiflex group

With respect to the anterior chamber cell and flare, in the Artiflex group, eight eyes developed trace cell and flare in the anterior chamber 1 year after operation, but there was no case of anterior chamber cell and flare in the ICL group postoperatively. The difference was statistically significant (P = 0.03).

There was no statistically significant difference in contrast sensitivity between the two groups [Table 7].

Table 7

The postoperative contrast sensitivity of implantable contact lens and Artiflex group. (mm Hg) and Artiflex group

Discussion

The aim of this study was to compare the outcomes and complications of two pIOLs in patients with high myopia. In several studies, pIOL has been reported as a safe, effective, stable, and predictable method for correcting refractive errors such as high myopia and hyperopia.[6-8]

This method has also been used for correcting high myopic astigmatism.[9]

In our study, the Artiflex pIOL was inserted in one eye and the ICL in the other eye of 20 patients randomly, to exclude the effects of sex, age, and person as confounding effects. As mentioned previously, no significant difference in visual acuity improvement was detected between the two groups. In a study conducted in the USA, two pIOLs (Visian ICL versus Verisyse) were compared. In that study, only the binocular UCVA was better in Visian ICL group; there was no difference in monocular UCVA between the two groups. A better refractive outcome was reported in the Visian ICL group.[10]

As mentioned previously, a postoperative IOP rise was noted in both groups 1 year after surgery; but there was no case of glaucoma or IOP greater than 21 mm Hg. This may be due to performance of a routine surgical peripheral iridectomy during the surgery. The high vaulting of ICL can cause pupillary block and close angle glaucoma. The Artiflex can also cause angle closure glaucoma induced by pupillary block. Iris pigment release can also cause increased IOP. In a study that assessed the effect of ICL on anterior chamber angle and pigmentation, it was noted that the ICL caused narrowing of anterior chamber angle from 30° to 20° in 20% of patients. Pigment in the anterior chamber increased following iridotomy. Pigment release may also be attributed to iris rubbing over the ICL. However, this increased pigmentation is transient and improved over 12 months. In this study, the elevated IOP may be due to application of topical steroid 1 week and 1 month postoperatively, which reaches the normal level gradually during 12 months after surgery. So, the ICL insertion seems to be a safe method, but can cause pigmentary change in trabecular meshwork.[11]

Incidence of cataract formation does not differ between these two groups. In each group, only one case developed posterior subcapsular cataract. The ICL with small size has small vault, so the probability of cataract formation does increase. In one study, PCpIOLs induced anterior subcapsular cataract.[12]

The causes of the cataract formation are unknown, but may be due to altered aqueous humor dynamics or restricted perfusion.[13]

A major concern about pIOLs is endothelial cell damage.[1415] Our study showed no significant difference of endothelial cell density and CV of endothelial cell between two eyes 1 year after surgery. A longer follow-up is necessary. In one study where the effect of iris-fixated pIOL on endothelium was evaluated, the endothelial cell loss was shown during the 5 years after surgery, especially in the first 2 years. However, decrease in CV and increase in hexagonal cells was detected gradually during 5 years after surgery. This may indicate increased stability and remodeling of endothelial cells.[16]

ICL can cause rapid endothelial cell loss initially. However, the hexagonal cell percentage and CV are stable during 5 years after surgery.[17]

Long-term follow-ups reveal that there is no ongoing chronic cell loss in endothelium layer 4 years after ICL insertion.

In our study, there was a higher incidence of anterior chamber cell and flare in the Artiflex group, which may be attributed to iris rubbing between IOL and crystalline lens.[18]

Anterior uveitis after pIOL insertion has been reported in several studies.[1920] This complication may be recurrent in the Artiflex group.[21] The patients with anterior chamber cell and flare have no pain, conjunctival hyperemia, keratic precipitate or other signs of uveitis. So, we cannot consider this evident as anterior uveitis. Recurrent uveitis can lead to occlusion of iridectomy.[22]

There is no significant difference of contrast sensitivities between two groups postoperatively. It seems that pIOL cause less decrease in contrast sensitivity due to less spherical aberration in contrast to corneal laser ablation.

In summary, these two pIOLs have similar visual outcomes and short-term complication rates with the exception of greater anterior chamber cell and flare in the Artiflex group.

Our study reveals that both these pIOLs are effective and safe, and their implantation is a predictable method for refractive surgery in high myopia.

Table 2

The preoperative best corrected visual acuity (Log MAR) of implantable contact lens and Artiflex group

Table 3

The postoperative uncorrected visual acuity of implantable contact lens and Artiflex group