Posterior chamber phakic intraocular lenses (IOLs) are generally considered to be a reasonably safe and effective treatment modality for higher grades of ametropia (especially myopia).1,2 Long-term follow-up of these patients generally demonstrates satisfactory outcomes.3–7 Additionally, the visual quality (aberrometry, contrast sensitivity) has been reported to be equivalent or even superior to laser in situ keratomileusis (LASIK) in high degrees of ametropia.8,9 Currently, the Visian ICL (STAAR Surgical, Nidau, Switzerland) is approved for use by the U.S. Food and Drug Administration for correction of myopia and astigmatism. A modification of the original design includes the use of a central eyelet (hole) that purportedly allows aqueous humor circulation, acts to eliminate the risk of pupillary block, and attempts to avert the need for peripheral iridectomies.10–14 However, comparative studies did not find a significant difference between the two models in terms of final visual acuity gain, intraocular pressure (IOP) spikes, endothelial cell loss, or cataract formation.10–14 Phakic IOLs are also a therapeutic option for young children with high myopia.15 They have shown application in a variety of conditions, such as after radial keratotomy,16 a notoriously difficult condition to treat.
An alternative implantable phakic posterior chamber IOL is the IPCL (Care Group, Baroda, India). This lens is made of reinforced hybrid acrylic material with medium water content. It has a plate haptic design with an anterior vault and a power ranging from +15.00 to −30.00 D with a cylinder up to 8.00 D. To the best of our knowledge, there are no reports evaluating the outcomes of this lens. We report our preliminary analysis of intermediate term follow-up (3 years) for this new phakic implantable posterior chamber lens as therapy for moderate to high myopia in an Indian cohort of patients.
Patients and Methods
Study Design/Patient Enrollment
This was a prospective, 3-year, non-randomized clinical trial including 30 eyes (16 consecutive patients) that underwent implantation of the IPCL for the correction of myopia (with or without astigmatism) and completed 3 years of postoperative follow-up.
The inclusion criteria were as follows: patients between 20 and 45 years of age with myopia or myopic astigmatism and manifest refractive spherical equivalent (MRSE) between −5.00 and −25.00 D sphere with a maximum of 4.00 D cylinder; stable refraction for at least 6 months; anterior chamber depth of greater than 2.8 mm; and endothelial cell density (ECD) of greater than 2,000 cells/mm2. Patients with a history of prior ocular surgery or ocular comorbidities (keratoconus, corneal disorders, cataract, glaucoma, or uveitis) and patients who were pregnant or lactating during the study period were excluded. The study was approved by the Ethics Committee of Iladevi Cataract & IOL Research Centre. Written, informed consent was obtained from all patients prior to the start of the study. A study coordinator was assigned for the study, and follow-up visits were performed free of charge to ensure follow-up compliance.
IPCL Lens Specifications
This lens is made of reinforced hybrid acrylic material with medium water content to ensure stability and vaulting. It is a plate haptic design with an anterior vault. The IPCL has a total opening area of 2,400 μm made up of six holes on the optic and optic-haptic vault (Figure 1) to reduce light scattering and allow equalizing of the pressure between the posterior and anterior chamber across the lens. The power ranges from +15.00 to −30.00 D with 8.00 D cylinder and customization is possible. Overall length varies from 11 to 14 mm in 0.25-mm steps, central thickness varies from 150 to 80 μm, and optic diameter varies from 5.75 to 6.20 mm depending on the diopters and overall length. It is available in spherical, toric, and presbyopic versions.
Appearance of the new posterior chamber phakic intraocular lens postoperatively.
All patients underwent a thorough anterior and posterior segment evaluation preoperatively and at all postoperative visits. Visual acuity was measured using the Early Treatment Diabetic Retinopathy Study vision chart and recorded in logMAR units. For standardization purposes, the CDVA was measured in all eyes using their spectacle lens prescription and not contact lenses. IOP was measured using Goldmann applanation tonometry, Ocular biometry was measured using partial coherence interferometry (IOLMaster 500; Carl Zeiss, Jena, Germany). Corneal tomography was performed using Scheimpflug imaging (Pentacam; Oculus Optikgeräte, Wetzlar, Germany) and corneal endothelial morphology was assessed using specular microscopy (OM-500; Tomey, Nagoya, Japan).
Lens Sizing and Power Calculation
IPCL power calculation was performed by the manufacturer using a modified vertex formula, targeting emmetropia for all eyes. The size of the IPCL was chosen by the manufacturer on the basis of the horizontal white-to-white diameter measured on the slit lamp by digital manual calipers and the IOLMaster and the anterior chamber depth measured by the IOLMaster.
Preoperatively, Nd:YAG peripheral laser iridotomy was performed at least 1 week prior to the surgery in all eyes. All surgeries were performed under topical anesthesia by a single surgeon (VV) using a standardized technique. Pupillary dilatation was achieved using a combination of tropicamide (0.8%) and phenylephrine (5%) eye drops, administered twice at 15-minute intervals, 1 hour prior to surgery. Two clear corneal 1-mm paracenteses were made, and the anterior chamber was formed with hydroxypropylmethyl cellulose. The IPCL was implanted through a 2.8-mm temporal, clear corneal incision with the use of an injector cartridge. Once the IPCL was placed in the posterior chamber, a thorough bimanual irrigation/aspiration was performed to remove the hydroxypropylmethyl cellulose from the anterior chamber.
All eyes were administered topical prednisolone acetate (1%) eye drops four times a day following surgery and were tapered weekly over a period of 4 weeks. Moxifloxacin (0.5%) eye drops were given three times a day starting on the day of surgery and until 2 weeks postoperatively. Timolol maleate (0.5%) eye drops were given twice a day, starting on the day of surgery and continued for 1 week postoperatively.
Study Outcomes and Patient Follow-Up
Patients were followed up at 1 day, 1 week, 1, 3, and 6 months, and 1, 2, and 3 years postoperatively. Main outcome measures were clarity of the lens assessed using the lens opacity analysis (Lens Opacity Classification System III [LOCS III]), ECD, IOP, UDVA, CDVA, MRSE, complications, and vault assessment. Objective vault was measured by anterior segment optical coherence tomography (Visante; Carl Zeiss Meditec) using calipers, as the distance between the posterior surface of the IPCL and anterior surface of crystalline lens.
Descriptive statistics were used to document patient profile and numbers in absolute and relative frequencies. The repeated measures analysis of variance (ANOVA) test was used to determine the significance of the change in UDVA and CDVA postoperatively and the significance of postoperative change in mean refractive spherical equivalent and endothelial cell count. Paired t tests were used to determine changes between different time points and whenever appropriate. Statistical significance was set at a P value of less than .05.
A total of 33 eyes (16 patients; 15 bilateral and 1 unilateral IPCL implantation) were recruited in the study. However, 2 patients (one with unilateral IPCL and one with bilateral IPCL) did not complete 3 years of follow-up and therefore were excluded from analysis. A total of 30 eyes were included for analysis. Preoperative demographic data are listed in Table 1. All eyes had uneventful surgery and there were no intraoperative complications encountered. Mean follow-up duration was 36.2 ± 1.2 months. A toric IPCL was implanted in 3 of 30 eyes (10%) due to preexisting astigmatism of more than 1.50 D.
Preoperative Patient Profile (N = 30 Eyes)
Visual Acuity Outcomes
There was a significant improvement in UDVA compared to preoperatively at all follow-up points (ANOVA, P = .013). Figure 2shows the percentage of eyes having a preoperative CDVA and postoperative UDVA of 20/20 or better, 20/30 or better, and 20/40 or better, respectively at each follow-up; 46% patients in this cohort achieved a UDVA of 20/20 or better at final follow-up.Figure 3 is a scatter diagram showing the distribution of CDVA in each eye individually, whereas Figure 4 is a scatter diagram of the UDVA for each eye. This cohort included eyes with high myopia, some of them with limited visual potential. Compared to preoperative CDVA of 20/40 or better in 61% eyes, 66% of eyes maintained UDVA of 20/40 or better at the final follow-up of 3 years.
Standard chart showing uncorrected distance visual acuity (UDVA) at different time points postoperatively compared to preoperative Ccrrected distance visual acuity (CDVA).
Scatter diagram showing distribution of corrected distance visual acuity (CDVA) at each follow-up point.
Scatter diagram showing the distribution of uncorrected distance visual acuity (UDVA) at each follow-up point.
The mean CDVA improved and was maintained until 3 years (ANOVA, P = .042 at 3 years). Figure 3 shows the distribution of CDVA of all eyes preoperatively and postoperatively. No eye lost visual acuity, 51% eyes showed no change, 41% eyes showed a gain of one line, and 8% of eyes showed a gain of two lines (Figure 5).
Change in corrected distance visual acuity (CDVA) postoperatively.
The safety indices (mean postoperative CDVA/mean preoperative CDVA) were 0.78, 0.72, 0.64, 0.67, and 0.64 at 1 and 6 months and 1, 2, and 3 years, respectively. The efficacy indices (mean postoperative UDVA/mean preoperative CDVA) were 0.94, 0.89, 0.86, 1.00, and 1.02 at 1 and 6 months and 1, 2, and 3 years, respectively.
MRSE was −16.50 ± 5.62 D preoperatively and reduced significantly to −0.31 ± 0.54 D at 1 month, −0.32 ± 0.40 D at 6 months, −0.40 ± 0.50 D at 1 year, −0.78 ± 0.95 D at 2 years, and −0.89 ± 1.27 D at 3 years postoperatively (Figure 6). The difference in MRSE between 1 month and 3 years showed a trend toward but did not approach statistical significance (P = .06). Figure 7 shows the refractive predictability at each follow-up time point. At 1 and 6 months and 1, 2, and 3 years postoperatively, 83%, 80%, 57%, 49%, and 45% of eyes were within ±0.50 D of the predicted refractive correction, respectively. Similarly, 92%, 100%, 100%, 72%, and 69% of eyes were within ±1.00 D of predicted refractive correction at 1 and 6 months and 1, 2, and 3 years, respectively.
Change in mean spherical equivalent (MRSE) over the 3-year follow-up period.
Predictability of refraction, percentage of eyes within ±0.50 and ±1.00 diopters (D) of predicted refraction.
Endothelial Cell Morphology
The mean preoperative ECD was 3,035.71 ± 70.24 cells/mm2, which reduced to 2,785.75 ± 97.12, 2,683 ± 108.59, and 2,654.56 ± 99.87 cells/mm2 at 1, 2, and 3 years postoperatively. The reduction in the mean ECD from preoperatively to 3 years postoperatively was not statistically significant (P = .11). At 3 years, the mean percentage loss in ECD was 9.73% ± 6.72%.
Vault measured by anterior segment optical coherence tomography was 626.66 ± 188.98 μm (range: 300 to 10,000 μm), 659 ± 145.63 μm (range: 350 to 950 μm), 591.42 ± 218.35 μm (range: 200 to 850 μm), 548.57 ± 227.92 μm (range: 120 to 800 μm), and 540.22 ± 210.76 μm (range: 90 to 710 μm) at 1 and 6 months and 1, 2, and 3 years postoperatively, respectively. There was a statistically significant reduction in the vault from 1 month to 3 years (P = .04) (Figure 8). One eye (3.3%) with high myopia (−27.00 D sphere, axial length = 32 mm) showed a significant reduction in vault from 360 μm at 1 month to 90 μm at 3 years.
Changes in the new posterior chamber phakic intraocular lens vault over time.
No eye developed pupil block glaucoma, pigment dispersion, retinal detachment, or any other vision-threatening complications.
None of the patients required cataract surgery during the follow-up duration of 3 years. One eye (3.33%) developed anterior subcapsular cataract at 2 years of follow-up. However, CDVA was maintained until 3 years of follow-up with a change in refractive correction (−0.75 −1.00 @ 100°) and has not required cataract surgery to the last follow-up visit. This eye had a preoperative manifest refraction of −27.00 D, with an axial length of 32 mm. This was also the eye in which the vault reduced considerably over the follow-up period (360 μm at 1 month to 90 μm at 3 years). The other eye of the same patient had a similar degree of preoperative myopia, but maintained a good vault throughout and had not developed cataract at the last follow-up visit. None of the other patients developed cataract during the study period.
The mean preoperative IOP was 14.25 ± 1.42 mm Hg. The mean postoperative IOP was not significantly different from preoperatively at any of the follow-up visits: 15.48 ± 4.46, 15.2 ± 1.98, 16.0 ± 0.89, 16.10 ± 1.10, and 15.99 ± 2.26 mm Hg at 1 and 6 months and 1, 2, and 3 years, respectively. The difference between preoperative and postoperative IOP at 3 years was not significant (P = .27). Two eyes of the same patient (6.6%) required topical IOP-lowering medication (timolol maleate 0.5%) until 3 months of follow-up, but after that IOP was controlled without any medication. No eye developed increased IOP requiring treatment until the last follow-up.
We report good results in this prospective, observational case series on the outcomes of the IPCL as an alternative for refractive correction of high myopia at a follow-up duration of 3 years. There was a clinically and statistically significant improvement in the visual acuity and refraction until 3 years of follow-up.
We observed UDVA of 20/20 or better in 45%, 20/30 or better in 49%, and 20/40 or better in 66% of eyes. The U.S. Food and Drug Administration study2 of the Visian ICL reported an overall UDVA of 20/20 or better in 40.8% of eyes and 20/40 or better in 81% of eyes at 3 years of follow-up. However, these figures were 48.9% and 86.3% of eyes in the high myopic group (> −7.00 D of myopia), which further dropped in patients with greater than −10.00 D of myopia. Similarly, in another long-term study on the Visian ICL, Igarashi et al.3 reported UDVA of 20/20 or better in 73% at 4 years of follow-up. On the other hand, Alfonso et al.4 reported UDVA of 20/40 or better in 68% of eyes, which matches our results. However, in both of the above-mentioned studies3,4 the patients included had MRSE ranging from −1.50 to −20.0 D, and results were not subanalyzed based on the degree of myopia. It is important to note that preoperative CDVA was 20/40 or better in only 61% of eyes in our study. This could be due to the fact that our study included “high myopic” eyes, with preoperative MRSE ranging from −7.50 to −27.00 D. No eye lost even a single line of Snellen visual acuity during the 3-year follow-up; in fact, 49% of eyes gained one line or more in corrected Snellen visual acuity. This correlates with previously reported studies.2–5 Further, it is interesting to note that, in the current study, all eyes that gained one or more lines of UDVA had a preexisting myopia of at least −10.00 D.
As expected, there was a significant reduction in the MRSE, which was maintained until the last follow-up visit. However, there was a slight regression effect seen after 2 years, with 69% of eyes falling within 1.00 D of predicted refraction at 3 years. There are multiple reasons for myopic regression after IPCL implantation. Few reports have shown continuing axial elongation of as much as 1 mm, with eyes having an axial length of 27.5 mm or greater at a higher risk of axial elongation.17,18 Additionally, some degree of nuclear sclerosis in high myopic eyes has also been stated as one of the mechanisms for myopic regression.
Only 1 eye (3.3%) in our series developed asymptomatic anterior subcapsular cataract at 2 years but continued to maintain good visual acuity until last follow-up. No eye required cataract surgery until the last follow-up. Various studies have reported the incidence of cataract from 0.5% to 14.5% up to 10 years of follow-up.3–10,19–22 There are concerns about the development of lens opacity because of the close proximity of the phakic IOL to the crystalline lens. Additionally, disturbance in the aqueous flow is also believed to be a mechanism for anterior subcapsular cataract. The Visian ICL introduced a central hole in the optic (Centraflow, V4C model) to prevent pupil block, eliminate the need for preoperative or intraoperative peripheral iridotomy, and improve aqueous circulation and thus possibly reduce cataract formation. However, to date, studies have not shown a difference in the rate of cataract formation with or without the central hole.11,12 The IPCL model studied had six peripheral holes instead of a central hole, with the objective of maintaining adequate aqueous circulation. However, a modified design of the IPCL with a central hole has recently been introduced. It would be interesting to study the performance of this model in the future.
No eye developed glaucoma, significant pigment dispersion, or any other complications until the last follow-up. All eyes did undergo prophylactic Nd:YAG peripheral laser iridotomy prior to surgery to prevent pupil block. Both eyes of one patient developed a transient increase in IOP that required timolol maleate (0.5%) monotherapy for a duration of 3 months.
Endothelial cell loss has been a concern with phakic IOLs. In our study, there was a reduction in ECD postoperatively, but the reduction in mean ECD from preoperatively to 3 years postoperatively was not statistically significant. At 3 years, the percentage ECD loss was 9.73% ± 6.72%. The reported percentage of long-term endothelial cell loss varied from 4% to 10% at 3 years,2,4,6,13,20–22 which is comparable to what we found. In a long-term study (8 years), the mean percentage of endothelial cell loss was reported to be 6.2%.3
As far as the IPCL vault is concerned, we found a trend toward slight reduction in the vault with time. Igarashi et al.3 reported a reduction in the mean vault of 0.5 mm at 4 years and 0.8 mm at 8 years. The exact reasons for this are not yet known. The main concern with a reducing vault remains cataract formation. However, with the introduction of the hole in the central optic, it is believed that even with a low vault the aqueous circulation will not be impeded and therefore cataract formation may reduce. As yet, there is no literature proving this hypothesis.
The obvious limitations of our preliminary analysis are the small number of patients, the non-comparative nature of our study, and the lack of a long-term follow-up. Long-term follow-up and comparative studies with currently approved versions of these implantable posterior chamber phakic lenses should validate these preliminary observations.
The IPCL appears at preliminary analysis to have good outcomes at 3 years of follow-up for correction of high myopia. The procedure of implantation is more or less similar to currently available lens models and can be performed without significant complications.
- Sander DR, Vukich JA, Doney K, Gaston MImplantable Contact Lens in Treatment of Myopia (ITM) Study Group. U.S. Food and Drug Administration clinical trial of the implantable collamer lens (ICL) for moderate to high myopia. Ophthalmology. 2003;110:255–266. doi:10.1016/S0161-6420(02)01771-2 [CrossRef]
- Sanders DR, Doney K, Poco MImplantable Contact Lens in Treatment of Myopia (ITM) Study Group. U.S. Food and Drug Administration clinical trial of the implantable collamer lens (ICL) for moderate to high myopia: three-year follow-up. Ophthalmology. 2004;111:1683–1692. doi:10.1016/j.ophtha.2004.03.026 [CrossRef]
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Preoperative Patient Profile (N = 30 Eyes)
|Age (y)||23.25 ± 2.29 (range: 20 to 27)|
|Manifest sphere (D)||−16.52 ± 5.62 (range: −7.50 to −27.00)|
|Manifest cylinder (D)||−0.98±0.81 (range: −0.50 to −2.75)|
|UDVA (logMAR)||1.3 ± 0.10 (range: 1.5 to 0.9)|
|CDVA (logMAR)||0.37 ± 1.97 (range: 0.2 to 0.7)|
|Axial length (mm)||28.70 ± 2.31 (range: 25.3 to 32.3)|
|Anterior chamber depth (mm)||3.28 ± 0.33 (range: 2.81 to 3.69)|
|Central corneal thickness (μm)||530.16 ± 37.44|
|Horizontal white-to-white distance (mm)||11.61 ± 0.55 (range: 10.5 to 12.0)|
|Intraocular pressure (mm Hg)||14.25 ± 1.42 (range: 12 to 16)|
|Endothelial cell density (cells/mm2)||3,035.71 ± 70.24 (range: 2,952 to 3,104)|
|Endothelial coefficient of variance||38 ± 6.68 (range: 27 to 45)|