Implantable Collamer Lens Subluxation in a Patient with Lenticular Coloboma: A Case Report

Background

Lens coloboma is a defect in the lens caused by a congenital zonular deficiency during embryogenesis. It is characterized by peripheral lens indentation and flattening at the equator. Lens coloboma is not a true coloboma because, unlike colobomas of the iris or choroid, there is no specific focus of missing tissue [1–3]. However, the lens becomes more spherical in the defective areas, which can cause astigmatism and decreased visual acuity [4]. It is usually located inferonasally due to failure of the fetal fissure to close at the area. The associated refractive errors are usually corrected using spectacles or contact lenses. However, in severe cases, surgical correction may be required to address decreased vision. In children, intraocular lens (IOL) implantation with or without a capsular tension device may be required to prevent amblyopia [5].

Although lens colobomas are usually sporadic, some are inherited in an autosomal-recessive, autosomal-dominant, or x-linked pattern. They may be accompanied by a systemic disorder or other ocular manifestations [6,7]. Among the ocular manifestations linked to lens coloboma are optic disc colobomas or hypoplasia, retinal detachment, and a variety of cataracts [7]. Also, lens subluxation has been reported with colobomas of the lens, as they involve the zonules [8]. Regarding systemic manifestations, lens colobomas have been reported with coexisting facial dysmorphism as well as in systemic disorders including Marfan syndrome and Alport-like glomerulonephritis. There has also been 1 reported case with an isolated bicuspid valve [7]. Additionally, lens colobomas have also been reported without any systemic manifestations [5,7,8]. We report a case of unilateral lenticular coloboma without cataract in a patient with a Marfanoid body habitus who underwent implantable collamer lens (ICL, Staar Surgical AG, Nidau, Switzerland) implantation followed by a postoperative complication of ICL subluxation.

Case Report

A 27-year-old man presented to our hospital seeking refractive surgery in November 2019. The patient reported having decreased vision in his right eye over the last 2 years. The patient had not been diagnosed with Marfan syndrome but had a Marfanoid body habitus; however, no genetic testing was performed. There was no history of trauma or previous ocular surgeries, and he was not on any medications. The presenting uncorrected visual acuity (UCVA) was 20/200 (20/50 pinhole) in the right eye and 20/40 (20/30 pinhole) in the left eye. The best spectacle corrected visual acuity (BSCVA) in the right was 20/30 with a refraction of −2–5.5×15°. The left eye was corrected to 20/20 with a refraction of Plano – 3×150°. Slit lamp examination indicated a clear cornea, mild iridodonesis, and inferior lens coloboma extending from the 5 o’clock to the 7: 30 o’clock position in the right eye after pupil dilation. No other ocular coloboma was detected upon examination during a dilated fundus exam. Examination of the left eye was unremarkable (Figure 1). Topographic horizontal white-to-white (WTW) diameters were (Pentacam; Oculus Gmbh, Wetzlar, Germany) 12.6 and 12.5 in the right and left eyes, respectively. Ocular biometric horizontal WTW diameters were (IOLMaster-500; Carl Zeiss Meditec, Jena, Germany) 13.8 mm and 13.5 mm in the right and left eyes, respectively. Topographic preoperative corneal curvatures were 43.1×112 and 39.8×22 in the right eye. Topographic apex pachymetry were 473 mm and 472 mm in the right and left eyes, respectively. Topographic Internal anterior chamber depth (ACD) were 3.10 mm and 3.28 mm in the right and left eyes, respectively. Axial length (AL) (IOLMaster-500; Carl Zeiss Meditec, Jena, Germany) was 24.42 mm and 23.96 mm in the right and left eyes, respectively. His endothelial cell count was 2292 cells/mm2 and 2486 cells/mm2 in the right and left eyes, respectively.

The patient was prescribed spectacles based on the refractions above and was assessed at regular intervals for almost 3 years. Until recently, the patient was interested in interventions other than spectacles or contact lenses. A serial refraction performed over a 2.5-year follow-up confirmed a stability of his refractive error. Given the presumed 1 quadrant of weak zonules and absence of cataract, a toric ICL (VTICM5 13.2–8.0+5.5×95°) implantation was performed as a temporary measure after explaining risks and benefits, including possible subluxation, dislocation, abnormal vault, and the potential of cataractous changes. The ICL size was calculated using Staar Surgical’s software and topographic data (WTW, internal ACD), then was verified by the ICL company’s representative. The intended axis for ICL during implantation was 10° counterclockwise, which was distant from the lens coloboma.

During the first follow-up, the ICL was centered, in its intended axis, with central vaulting (distance between ICL and crystalline lens) of half corneal thickness clinically, and UCVA was 20/40. Three weeks postoperatively, the patient presented with decreased vision. Upon examination, UCVA was 20/80, the ICL subluxated inferiorly, and the previously implanted temporal footplates were resting over the lenticular defect inferiorly, indicating ICL rotation greater than 30° (Figure 2). Central vaulting was 96 µm as measured with MS-39 anterior segment ocular coherence tomography (Costruzione Strumenti Oftalmici, Italy). A high-resolution ultrasound biomicroscopy (UBM) confirmed the presence of a ciliary body cyst at 9 o’clock position. The patient was scheduled for urgent removal of the ICL. Intraoperatively, the coloboma extended from the 5 o’clock to the 8 o’clock position and partial lens densities of zonules were present in the area of lenticular defect (Figure 3). The ICL was explanted safely from the eye and the postoperative period was unremarkable.

Discussion

In early 2022 the EVO/EVO+ VISIAN ICL and toric ICL (STAAR Surgical Co., Monrovia, CA, USA) were both approved by the FDA [9]. However, in our region, these ICLs have been used for quite some time to treat high refractive error and astigmatism. Although rare, postoperative complications have been reported, including cataract formation, pigment dispersion, intraocular inflammation, toxic anterior segment syndrome, traumatic subluxation, and toric ICL rotation [10]. Most of the reported cases of lenticular coloboma were bilateral and had cataract changes, making cataract removal and IOL implantation the clear management option. However, in our case, there was no cataract in the right eye and the patient wanted a solution other than spectacles or contact lenses to address the anisometropia. Laser vision correction (LVC) in our patient with Marphan-like syndrome was not an option due to high refractive error, relatively thin cornea, theoretical increased risk of post-LASIK ectasia, poor wound healing, and poor refractive predictability [11]. Artisan toric phakic IOL or Verisyse toric phakic IOL would have been a better choice, but were not available in Saudi Arabia. The safety and effectiveness of the ICL has not been established in patients with weak zonules, including pseudoexfoliation and coloboma [9]. Therefore, after a thorough discussion about the risks and benefits of ICL implantation in an eye with weak zonules, the patient agreed to proceed with it.

Refractive surgeons who routinely use different automated instruments to measure WTW distance for ICL usually consider existing differences between them in their routine clinical practice. Studies comparing 4 instruments, including IOL Master 500 and Pentacam, have shown that the measurements are not interchangeable [12]. In the current case, there was a wide variation between Pentacam and IOL master measurements; therefore, we used the Pentacam measurement.

On the first postoperative day, his vision was corrected to his full potential and the ICL was stable. Unfortunately, the patient presented at his second follow-up with a drop in vision and a subluxated and rotated ICL. There was no history of trauma before this follow-up visit, as most previously published cases of ICL dislocation are secondary to blunt injury [13]. Only 1 case of late ICL subluxation was reported in the literature [13]; the authors speculated the reason behind the inferior subluxation of the ICL in their case was related to either zonular rupture from intensive eye rubbing or the presence of a zonular defect before surgery [14]. They elected for ICL explantation [14].

With the development of advanced medical technique, UBM is an important investigation tool that can effectively exclude the presence of iris and/or ciliary body cysts in myopic eyes. These cysts are usually located inferotemporally in the anterior segment, most commonly in the iridociliary sulcus and/or pars plicata [15]. In our case, the CB cyst was detected at 9 o’clock, which likely caused interaction with the haptic and pushed it inferiorly closer to the location of the lens coloboma. An additional reason for presumed ICL instability is that when ICL is implanted horizontally, it will have the extreme parts of the haptics close to 2 and 4 o’clock (nasally) and 8 to 10 o’clock (temporally). Therefore, it is very likely that an interaction between the weak zonules area and the ICL haptics may exist.

In the current case, the clinical presentation warranted urgent removal of the ICL. There were multiple issues raised in this case, and a toric ICL was implanted to correct the high astigmatism, which is common with lenticular coloboma. Furthermore, subluxation was accompanied with rotation of the ICL, which further aggravated the visual disturbance. Explantation was necessary in this case, as the ICL could cause further damage to the surrounding zonules, which are presumably weak in such cases. Additionally, we were concerned that the ICL might fall into the vitreous cavity if explantation was delayed. This complication was reported previously in 1 case with a different model of phakic intraocular lens in a highly myopic patient [16]. The presumed cause was zonular weakness and damage [16].

In patients who undergo spherical ICL implantation and with poor stability, a change in the axis of the ICL may provide lens stability [17]. However, this was not an option in our case, as the intended axis was required for correcting the cylindrical component of the refractive error [18]. Additionally, the low ICL vault observed with subluxation in our case was another reason for explantation, as it is associated with inducing cataractous changes due to ICL-lens capsule contact [17,19].

Conclusions

We concluded that lens coloboma without cataract are not absolute contraindications for ICL surgery. It is important to perform a careful UBM scan in these cases preoperatively to exclude the co-existence of iris and/or ciliary body cysts, which may cause the ICL haptics to adopt very different positions than intended. For cases with small lens coloboma (less than 1 quadrant of zonular weakness/deficiency) that is located away from the horizontal haptics orientation, it is important to consider ultrasonic ICL haptics monitoring postoperatively. For cases with large lens coloboma (more than or equal one quadrant of zonular weakness/deficiency), the stability of the ICL cannot be guaranteed to prevent subluxation or dislocation. In addition, for cases with a Marfanoid body habitus, maximal pupil dilation preoperatively is important to accurately assess the extent of lens coloboma.