Posterior chamber phakic intraocular lenses (IOLs), such as the Visian Implantable Collamer Lens (Visian ICL; STAAR Surgical Company, Nidau, Switzerland), are an established option for surgical correction of myopia.1 Phakic IOL implantation may be preferable when patients are unsuitable for photorefractive keratectomy or LASIK or have keratoconus.2 Vault is the distance between the posterior surface of the phakic IOL and anterior lens capsule. Proper phakic IOL sizing leads to adequate postoperative vault and long-term safety of the implant. Improper sizing can be associated with complications if not managed appropriately. Conventionally, sizing has been determined by preoperative parameters, such as white-to-white diameter, anterior chamber depth, or sulcus-to-sulcus diameter.3 However, inappropriate size is often only evident postoperatively, which may then require a second surgical procedure for explantation. Ideally, intraoperative confirmation of phakic IOL sizing could prevent such occurrences.
In this case series, we present our experience using intraoperative optical coherence tomography (OCT) for vault measurement to confirm appropriate phakic IOL size.
Patients and Methods
This case series involved 5 eyes in 3 consecutive patients undergoing phakic IOL implantation by one surgeon. All 3 patients presented to the Singapore National Eye Centre, Singapore, for surgical correction of myopia. For patients 1 and 2, indications for phakic IOL implantation were high refractive error (patient 1: right eye = −10.50 −2.00 × 5°, left eye = −8.75 −2.00 × 170°; patient 2: right eye = −10.00 −1.50 × 10°, left eye = −9.00 −5.00 × 175°). Patient 3 had a thin central corneal thickness of 418 µm bilaterally. Preoperatively, white-to-white, sulcus-to-sulcus, and anterior chamber depth measurements were obtained and put into the proprietary formula provided by the manufacturer to choose lens size.
All 3 patients underwent implantation with a Visian V4C phakic IOL between June and November 2014. A 3.2-mm temporal clear corneal incision and paracentesis wound were created. The anterior chamber was filled with ophthalmic viscoelastic device (Provisc; Al-con Laboratories, Randburg, South Africa), and the phakic IOL was injected into the anterior chamber. Phakic IOL position was adjusted using a lens manipulator and the footplates were tucked under the iris. Ophthalmic viscoelastic device was expressed, the anterior chamber refilled with balanced salt solution (BSS), and the pupil constricted with acetylcholine hydrochloride. RTVue OCT (Optovue, Inc., Fremont, CA) was used to obtain measurements at various points intraoperatively (Figure 1). Visante OCT (Carl Zeiss Meditec, Jena, Germany) was used to measure postoperative vault at early (postoperative days 1 to 4) and late (postoperative months 1 to 3) time points.
(A) Intraoperative surgical photographs and (B) corresponding RTVue optical coherence tomography (OCT) (Optovue, Inc., Fremont, CA) images. After placement of ophthalmic viscoelastic device (OVD) into the anterior chamber, the phakic intraocular lens (IOL) was inserted and placed in the anterior chamber (A-1, B-1). The posterior surface of the phakic IOL is labelled with the yellow star, and the anterior lens capsule is labelled with the yellow square. The intraoperative vault measured with OCT was 517 µm (labelled with straight yellow lines). After tucking the footplates behind the iris with a lens manipulator (A-2, B-2), the vault measured was 301 µm (labelled with straight yellow lines). OVD was removed from the anterior chamber, and the pupil was constricted. The phakic IOL was in place (A-3, B-3), and the vault measured was 228 µm (labelled with straight yellow lines).
Sulcus-to-sulcus measurements and phakic IOL sizes used are presented in Table 1. Intraoperative vault was measured with the phakic IOL above the iris, after positioning below the iris, and after ophthalmic viscoelastic device removal. As an example, the vault measurements for the left eye of patient 2 were 954 µm above the iris, 529 µm below the iris, and 229 µm after ophthalmic viscoelastic device removal. Final intraoperative vault was measured after viscoelastic removal and pupil constriction with acetylcholine hydrochloride in all cases except the left eye of patient 3. Intraoperative vault ranged from 228 to 1,060 µm depending on pupil constriction. Postoperative vault ranged between 230 and 670 µm (Table 1). Although intraoperative vault was similar in all cases that had pupil constriction (228 to 305 µm), the vault of the larger lenses (13.2 mm) doubled in the early postoperative period. No phakic IOLs were explanted or replaced. There were no postoperative complications. Intraocular pressure measured by Goldmann applanation tonometry postoperatively ranged from 10 to 16 mm Hg. Good uncorrected visual acuity was achieved in all cases (Table 1).
Clinical Characteristics of 5 Eyes of 3 Patients
Intraoperative OCT has been applied to a variety of anterior and posterior segment surgeries, including lamellar corneal transplants, cataract surgery, and epiretinal membrane peeling procedures.4,5 Intraoperative OCT has been shown to allow the surgeon greater appreciation of tissue configuration and architecture, and can guide decision-making in the operating room.4,5 In cataract surgery, intraoperative OCT allows evaluation and confirmation of IOL position within the capsular bag.4,6 Intraoperative OCT measurements during cataract surgery have also been demonstrated to be accurate predictors of postoperative IOL position, which could allow more accurate IOL power calculations and improve refractive outcomes after cataract surgery.7,8 In undertaking this study, we demonstrated the utility of intraoperative OCT in phakic IOL implantation. To the best of our knowledge, we present the first report of the use of intraoperative OCT in phakic IOL sizing.
Improper phakic IOL sizing can cause complications such as cataract, glaucoma, and pigment dispersion.1 Excessively low vault (< 150 µm) can induce cataract9 by either direct contact with the crystalline lens or disrupting aqueous flow and lens nutrition.10 Approximately 2% of eyes will require phakic IOL removal and cataract surgery after phakic IOL implantation.11 Conversely, excessively high vault can induce angle-closure, pupillary block, or pigmentary glaucoma, which can be sight-threatening if not managed appropriately.12 The rate of raised intraocular pressure postoperatively is 0% to 2%,1 which may require medical treatment, laser treatment, filtration surgery, or phakic IOL explantation. There have also been reports of Urrets-Zavalia syndrome after phakic IOL implantation.13
Preoperative parameters such as white-to-white diameter and anterior chamber depth have been found to correlate with postoperative vault14 and have therefore been used with nomograms for phakic IOL sizing.3 However, white-to-white diameter may be inaccurate for vault prediction because the phakic IOL footplates are actually located in the sulcus.15 Therefore, sulcus-to-sulcus diameter, measured by preoperative ultrasound biomicroscopy, is now more frequently used because it has been found to correlate better with postoperative vault than white-to-white diameter.3,15 However, some patients may still have excessively low (< 150 µm) or high (> 1,000 µm) vault3,9,15 that may require a second surgery for exchange. This is likely because horizontal compression alone is insufficient to explain vaulting. Regression analysis shows that only 36.9% of postoperative vault can be explained by horizontal compression factors.15 Other factors such as vertical compression from the iris are also likely to affect vaulting. Currently, no preoperative formula takes into account all of these factors for phakic IOL sizing.
Our intraoperative vault measurements ranged from 228 to 1,060 µm (Table 1). All intraoperative measurements were within (or close to) the ideal range of 150 to 1,000 µm, and subsequently all postoperative measurements were satisfactory. With the exception of the left eye of patient 3, all cases showed an increase in postoperative vault from intraoperative measurements, which was probably due to intraoperative pupil constriction. The increase in postoperative vault depended on the size of the lens implanted. Larger studies need to be performed, but our pilot data does suggest that intraoperative OCT can pick up excessively high or low vaulting at the time of surgery.
The ideal time to perform intraoperative vault measurement has not been established. In our study, with the exception of the left eye of patient 3, all intraoperative vault measurements were performed after pupil constriction. However, given that acetylcholine hydrochloride constricts various irides to different degrees, perhaps a more consistent time for intraoperative vault measurement would be after ophthalmic viscoelastic device removal and refilling the anterior chamber with BSS but before pupil constriction. Further studies investigating this are warranted.
For logistic reasons, different OCT equipment was used for intraoperative and postoperative measurements in this study. The intraoperative OCT in this series is a standard commercial device that has been mounted on a microscope. The RTVue OCT was used intraoperatively because the orientation of the scanner can be adjusted to scan supine patients, which is not possible with the Visante OCT. For postoperative measurements, the Visante OCT was used because it is more readily available for patients in our institution. Nevertheless, we have previously published a study comparing measurements with the RTVue and Visante OCT systems, and these have been shown to be comparable.16 Hence, this allows for valid comparison between intraoperative and postoperative measurements in this study.
In our experience, intraoperative OCT is simple to perform and is a useful adjunct in phakic IOL implantation. It allows for real-time, in vivo vault measurement, which can confirm appropriate implant sizing and influence intraoperative decision-making. If intraoperative vault measurements are too high or low, the decision can be made intraoperatively to explant the phakic IOL without requiring a second operation. This may obviate the need for a second surgery later on and adds to the safety of phakic IOL implantation. The use of intraoperative OCT in posterior chamber phakic IOL implantation appears promising, but further studies are necessary to examine the relationship between intraoperative and postoperative vault measurements.
- Huang D, Schallhorn SC, Sugar A, et al. Phakic intraocular lens implantation for the correction of myopia: a report by the American Academy of Ophthalmology. Ophthalmology. 2009;116:2244–2258. doi:10.1016/j.ophtha.2009.08.018 [CrossRef]
- Alfonso JF, Fernandez-Vega L, Lisa C, Fernandes P, Gonzalez-Meijome JM, Montes-Mico R. Collagen copolymer toric posterior chamber phakic intraocular lens in eyes with keratoconus. J Cataract Refract Surg. 2010;36:906–916. doi:10.1016/j.jcrs.2009.11.032 [CrossRef]
- Kojima T, Yokoyama S, Ito M, et al. Optimization of an implantable collamer lens sizing method using high-frequency ultrasound biomicroscopy. Am J Ophthalmol. 2012;153:632–637. doi:10.1016/j.ajo.2011.06.031 [CrossRef]
- Ehlers JP, Dupps WJ, Kaiser PK, et al. The Prospective Intraoperative and Perioperative Ophthalmic ImagiNg with Optical CoherEncE TomogRaphy (PIONEER) Study: 2-year results. Am J Ophthalmol. 2014;158:999–1007. doi:10.1016/j.ajo.2014.07.034 [CrossRef]
- Ehlers JP, Goshe J, Dupps WJ, et al. Determination of feasibility and utility of microscope-integrated optical coherence tomography during ophthalmic surgery: the DISCOVER Study RESCAN Results. JAMA Ophthalmol. 2015;133:1124–1132. doi:10.1001/jamaophthalmol.2015.2376 [CrossRef]
- Lytvynchuk LM, Glittenberg CG, Falkner-Radler CI, et al. Evaluation of intraocular lens position during phacoemulsification using intraoperative spectral-domain optical coherence tomography. J Cataract Refract Surg. 2016;42:694–702. doi:10.1016/j.jcrs.2016.01.044 [CrossRef]
- Hirnschall N, Amir-Asgari S, Maedel S, Findl O. Predicting the postoperative intraocular lens position using continuous intraoperative optical coherence tomography measurements. Invest Ophthalmol Vis Sci. 2013;54:5196–5203. doi:10.1167/iovs.13-11991 [CrossRef]
- Hirnschall N, Norrby S, Weber M, Maedel S, Amir-Asgari S, Findl O. Using continuous intraoperative optical coherence tomography measurements of the aphakic eye for intraocular lens power calculation. Br J Ophthalmol. 2015;99:7–10. doi:10.1136/bjophthalmol-2013-304731 [CrossRef]
- Gonvers M, Bornet C, Othenin-Girard P. Implantable contact lens for moderate to high myopia: relationship of vaulting to cataract formation. J Cataract Refract Surg. 2003;29:918–924. doi:10.1016/S0886-3350(03)00065-8 [CrossRef]
- Khalifa YM, Moshirfar M, Mifflin MD, Kamae K, Mamalis N, Werner L. Cataract development associated with collagen copolymer posterior chamber phakic intraocular lenses: clinico-pathological correlation. J Cataract Refract Surg. 2010;36:1768–1774. doi:10.1016/j.jcrs.2010.04.039 [CrossRef]
- Sanders DR. Anterior subcapsular opacities and cataracts 5 years after surgery in the visian implantable collamer lens FDA trial. J Refract Surg. 2008;24:566–570.
- Alfonso JF, Fernandez-Vega L, Lisa C, Fernandes P, Gonzalez-Meijome J, Montes-Mico R. Long-term evaluation of the central vault after phakic Collamer(R) lens (ICL) implantation using OCT. Graefes Arch Clin Exp Ophthalmol. 2012;250:1807–1812. doi:10.1007/s00417-012-1957-0 [CrossRef]
- Yuzbasioglu E, Helvacioglu F, Sencan S. Fixed, dilated pupil after phakic intraocular lens implantation. J Cataract Refract Surg. 2006;32:174–176. doi:10.1016/j.jcrs.2005.11.016 [CrossRef]
- Alfonso JF, Fernandez-Vega L, Lisa C, Fernandes P, Jorge J, Montes Mico R. Central vault after phakic intraocular lens implantation: correlation with anterior chamber depth, white-to-white distance, spherical equivalent, and patient age. J Cataract Refract Surg. 2012;38:46–53. doi:10.1016/j.jcrs.2011.07.035 [CrossRef]
- Lee DH, Choi SH, Chung ES, Chung TY. Correlation between preoperative biometry and posterior chamber phakic Visian Implantable Collamer Lens vaulting. Ophthalmology. 2012;119:272–277. doi:10.1016/j.ophtha.2011.07.047 [CrossRef]
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Clinical Characteristics of 5 Eyes of 3 Patients
|Characteristic||Patient 1||Patient 2||Patient 3|
|Horizontal sulcus-to-sulcus diameter (mm)||11.95||12.02||12.00||11.90||11.90|
|Horizontal intraocular lens diameter (mm)||13.20||12.60||12.60||13.20||13.20|
|Intraoperative vault (µm)||256||228||229||305||1,060|
|Early postoperative vault (µm)||530||230||270||630||670|
|Late postoperative vault (µm)||510||270||350||630||590|
|UDVA at 1 to 3 months postoperatively||20/20||20/20||20/25||20/20||20/20|