Dr. Divya Singh, S19171, Dr. Radhika Tandon, Dr. Vanathi M, Dr. Shikha Yadav
Abstract:
Aim:
To quantitatively assess the parameters of anterior chamber and angle dimensions by anterior segment optical coherence tomography after Implantable collamer lens implantation.
Design:
Prospective case series.
Methods:
In 32 eyes of 16 patients with high myopia scheduled for ICL implant AS-OCT iridocorneal angle measurements were performed before and 3 months after the surgery. The anterior chamber angle (ACA) angle opening distance (AOD) at 500 and 750 micron from scleral spur trabecular-iris space area (TISA) at 500 and 750 micron and scleral spur angle (SSA) were compared.
Results:
Preoperative ACA was 34.684 ± 2.344 and at 3 months it was 31.944 ± 2.529 degrees showing a narrowing of 7.9 ± 2.69 %. In the pre-operative period AOD500 AOD750 TISA500 TISA750 and SSA were 0.349 ± 0.061 0.521 ± 0.159 0.098 ± 0.023 0.202 ± 0.044 mm and 34.278 ± 4.617 degrees which correspondingly fell to 0.321 ± 0.061 0.476 ± 0.132 0.085 ± 0.021 0.174 ± 0.053 mm and 32.403 ± 4.664 degrees at 3 months with significant difference (p < 0.001)
Conclusions:
Considerable angle narrowing was detected 3 months after ICL V4c implantation. Therefore factors predictive of angle dimensions could help in identifying suitable candidates for ICL implantation.
Keywords: ICL V4c, Angle, AS-OCT
Key Message: AS-OCT could be an important tool in evaluating the angle parameters after implantable collamer lens implantation.
Introduction:
Implantable Collamer Lenses (ICLs; Staar Surgical, Monrovia, CA) are soft, foldable, sulcus-placed posterior chamber phakic intraocular lenses that can be implanted through a small (3.0 mm) self-sealing limbal incision. ICL implantation is technically undemanding, relatively safe , and is increasingly popular as an alternative to laser refractive surgery, refractive lens exchange, and other phakic intraocular lenses in the surgical correction of higher levels of myopia.1-7 This procedure is an excellent option for eyes that are not suitable for laser refractive correction such as those with high refractive errors such as myopia,1-7 hyperopia,8-10 or astigmatism,11-14 thin corneas, ectactic conditions such as keratoconus15 with results comparable to other laser procedures or even better.16-18 Faster visual recovery, high efficacy and stability of visual quality, preservation of accommodation, and reversibility are several advantages that have been attributed to PIOL implantation.19
Materials and methods:
Study design:
This was a prospective case series study which was done in the Department of Ophthalmology, Dr. Rajendra Prasad Center for Ophthalmic Sciences, AIIMS, New Delhi, in accordance with the tenets of Declaration of Helsinki and ethical clearance from Institutional Ethics Committee, AIIMS was obtained. We included 32 eyes of 16 patients with high myopia who were scheduled for ICL V4c implantation, between the age of 20 to 40 years with a stable refractive error for previous two years who were not amenable to laser refractive surgeries. All patients with hyperopia, anterior chamber depth less than 2.8 mm, previous history of ocular inflammation or glaucoma, and concurrent corneal disease were excluded from the study. All surgeries were performed by a single surgeon by following a standard protocol.
Data collection:
The preoperative details included uncorrected visual acuity and best corrected visual acuity, slit lamp examination, intraocular pressure, endothelial cell count, AS-OCT for iridocorneal angle dimensions. Postoperative parameters included uncorrected and best corrected visual acuity, tonometry, lens vaulting, iridocorneal angle measurements using AS-OCT which included Anterior chamber angle (ACA), Angle opening distance (AOD 500 & AOD 750), Trabecular iris space area (TISA 500 & TISA 750), and Scleral spur angle (SSA).
Surgical technique:
All surgeries were done under topical anaesthesia using 0.5 % proparacaine hydrochloride. Pupillary dilatation was achieved with a combination eyedrop containing 1% tropicamide and 2.5% phenylephrine. With a temporal approach, two 1 mm paracenteses ports were made using angled keratome or 15 side port knife at 12 and 6 o’clock positions. Hypromellose 2% (Viscomet PF, Unimed technologies) viscoelastic was then injected into the anterior chamber taking care not to overfill the chamber. A temporal 3.2 mm clear corneal incision was made using keratome. The ICL was loaded into the cartridge and injected into the anterior chamber. The paracenteses was used to position the footplates under the iris using the special manipulating instruments like Vukich’s manipulator. It was also ensured that all haptics were posterior to the iris. In case of TICL (Toric ICL) proper alignment was ensured. At the end of surgery, viscoelastic was cleared from the AC. A standard postoperative regime consisting of topical prednisolone acetate 1% 4 times a day for 5 days tapering over 2 weeks and topical moxifloxacin 0.5% 4 times a day for 2 weeks was started. Postoperatively, the patient was examined at day 1 to check for proper ICL positioning and vaulting on slit lamp, and IOP was checked. The patient was followed up regularly at 1 week, 1 month, 3 months and 6 months after the surgery. At each visit, uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA) , IOP, central corneal thickness (CCT) , ICL vault and angle parameters such as ACA, AOD 500, AOD 750, TISA 500, TISA 750 , SSA were measured using ASOCT.
The data was analyzed using SPSS version 20 (Statistical Package for Social Sciences) with paired t-test for intragroup comparison and Mann Whitney U value test for intergroup comparisons. A p value less than 0.05 was considered significant.
Results:
Thirty two eyes of sixteen patients were included in this study out of which 10 (62.5%) were females and 6 (37.5%) were males. Mean age of presentation was 28.7 ± 3.2 years. Six patients (54.55%) had right eye involvement and other five (45.45%) had the involvement of the left eye. There was an equivocal involvement of the right and left eyes (50 % each). The mean size of the ICL V4c implanted was 13.2 +/- 0.34 mm, with a mean spherical power of -10.43 +/- 3.12 dioptres and a mean cylindrical power of 2.21 +/- 0.21 dioptres. The mean value of anterior chamber angle was 34.68 +/- 2.34 degrees preoperatively which decreased significantly to 31.94 +/- 2.52 at 3 months post-op period (p < 0.001). The mean preoperative values of AOD 500 and AOD 750 were 0.35 +/- 0.06 mm and 0.52 +/- 0.15 mm respectively both of which decreased significantly at 3 months post-op period (p < 0.001). The mean preoperative values of TISA 500 and TISA 750 were 0.09 +/- 0.02 mm2 and 0.2 +/- 0.04 mm2 respectively both of which decreased significantly at 3 months post-op period (p < 0.001). The mean value of scleral angle was 34.28 +/- 4.62 degrees preoperatively which decreased significantly to 32.4 +/- 4.66 at 3 months post-op period (p < 0.001). However, no significant difference was noted in any of these parameters between 1 month and 3 months post-op period.
Discussion:
Considerable angle narrowing was detected 1 month after ICL V4c implantation. Therefore factors predictive of angle dimensions could help in identifying suitable candidates for ICL implantation.
References:
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Acknowledgement: None
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