Accuracy of Refractive Outcome Using Optical Low Coherence Reflectometry in Silicone Oil-Filled Eyes Undergoing Intraocular Lens Implantation with Silicone Oil Removal

C. K Minija; P. Mahesh Shanmugam; K. Padmaja; Nidhi Dubey; Rajesh Ramanjulu; K. C Divyansh Mishra

doi:10.4103/njo.njo_7_19

ORIGINAL ARTICLE

Year : 2019 | Volume : 27 | Issue : 2 | Page : 82-85

Accuracy of Refractive Outcome Using Optical Low Coherence Reflectometry in Silicone Oil-Filled Eyes Undergoing Intraocular Lens Implantation with Silicone Oil Removal

C. K Minija¹, P. Mahesh Shanmugam², K. Padmaja¹, Nidhi Dubey¹, Rajesh Ramanjulu², K. C Divyansh Mishra²
¹ Department of Uvea and Medical Retina Services, Sankara Eye Hospital, Bengaluru, Karnataka, India
² Depatment of Vitreoretinal Services and Ocular Oncology, Sankara Eye Hospital, Bengaluru, Karnataka, India

Date of Submission	14-Mar-2019
Date of Decision	26-Jul-2019
Date of Acceptance	11-Sep-2019
Date of Web Publication	07-Feb-2020

Correspondence Address:
Dr. C. K Minija
Uvea and Medical Retina Services, Sankara Eye Hospital, Varthur Rd., Kundalahalli Gate, Bengaluru - 560037, Bengaluru, Karnataka
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/njo.njo_7_19

Abstract

Aim: To assess the accuracy and consistency of intraocular lens (IOL) power calculation using optical low coherence reflectometry device (OLCR), LENSTAR LS-900, in silicone oil-filled eyes undergoing combined IOL implantation and silicone oil removal (SOR). Setting: Sankara Eye Hospital, Bangalore, Karnataka, India. Design: Retrospective study. Method: This study comprised 49 silicone oil-filled eyes of 47 patients who underwent combined IOL implantation with SOR. All patients were measured with OLCR before performing phacoemulsification and IOL implantation in silicone oil mode. The predicted refraction as calculated with OLCR was correlated with the postoperative spherical equivalent. Results: The mean deviation of the spherical equivalent was −0.74 diopters (D). The mean difference between predicted refraction and postoperative spherical equivalent was −0.34 D. The mean axial length of the eyes was 23.53+1.86 (range 21.49–30.03 mm). Conclusion: OLCR is a safe device that provides precise biometry and accurate IOL power calculation in silicone oil-filled eyes.

Keywords: biometry, LENSTAR, optical low coherence reflectometry, phacoemulsification, refractive outcome, silicone oil removal

How to cite this article:
Minija CK, Shanmugam PM, Padmaja K, Dubey N, Ramanjulu R, Mishra KC. Accuracy of Refractive Outcome Using Optical Low Coherence Reflectometry in Silicone Oil-Filled Eyes Undergoing Intraocular Lens Implantation with Silicone Oil Removal. Niger J Ophthalmol 2019;27:82-5

How to cite this URL:
Minija CK, Shanmugam PM, Padmaja K, Dubey N, Ramanjulu R, Mishra KC. Accuracy of Refractive Outcome Using Optical Low Coherence Reflectometry in Silicone Oil-Filled Eyes Undergoing Intraocular Lens Implantation with Silicone Oil Removal. Niger J Ophthalmol [serial online] 2019 [cited 2022 Jul 3];27:82-5. Available from: http://www.nigerianjournalofophthalmology.com/text.asp?2019/27/2/82/277891

Introduction

Pars plana vitrectomy (PPV) combined with fluid or silicone oil exchange is a method in the management of complex retinal detachment enabling visual recovery in eyes that were deemed inoperable previously.^[1] Silicone oil-filled eyes lead to cataractous formation due to high oxygen tension in vitreous cavity during surgery and exposure to oxygen stress leads to disruption of metabolic environment of clear lens.^[2],[3] With advancement in the microinvasive armamentarium for cataract surgery and PPV, many surgeons considered phacoemulsification with intraocular lens (IOL) implantation at the time of silicone oil removal (SOR) as a single procedure. Success in visual improvement in such cases depends on the precise axial length (AL) measurement and accurate IOL power calculation.

The purpose of the study is to assess the consistency and efficiency of IOL power calculation using optical low coherence reflectometry device (OLCR) in silicone oil-filled eyes.

Methods

This was a retrospective study conducted in tertiary eye care center, comprising 49 silicone oil-filled eyes of 47 patients who underwent combined SOR with IOL implantation from September 2015 to August 2017. This study obtained ethical approval from ethical committee. Exclusion criteria included eyes with silicone oil exchange, eyes remaining aphakic, and pre- or postoperative clinical data unavailable.

Study data were divided into phakic and aphakic groups based on preoperative lens status. All pre-, intra-, and postoperative clinical data were obtained from the medical records, which include preoperative age and gender of the patient, diagnosis, preceding medical and surgical history, AL, IOL power, preoperative refraction and best-corrected visual acuity (BCVA), intraoperative IOL implantation site, date of silicone oil infusion and silicone oil viscosity, postoperative BCVA, and refraction, to assess the residual refractive error. BCVA was measured using Snellen charts and then converted into logarithm of the minimum angle of resolution (log MAR) for statistical analysis. Preoperatively, AL, IOL power, and predicted refraction were measured in all the study patients with OLCR using LENSTAR LS-900. SRK-T formula was used to calculate IOL power before SOR and IOL implantation.

The observed postoperative refraction was compared with the predicted refraction to determine the accuracy and the consistency of IOL power calculation.

Statistical analysis

Descriptive statistics were calculated initially. The mean, standard deviation, and minimum and maximum statistics were derived for continuous parameters and proportion statistics were calculated for categorical data parameters. Mann-Whitney U test was used to compare the medians between groups. Wilcoxon signed-rank test was used to compare the preoperative versus postoperative non-normally distributed data. Kruskal–Wallis test was used to compare the mean difference between ciliary sulcus, in-the-bag, and scleral fixated IOL position groups. A two-sided p-value less than 0.05 was considered to be statistically significant. All analyses were carried out by using the SPSS 17.0 version (SPSS, Chicago, IL, USA) software for Windows.

Results

Forty-nine silicone oil-filled eyes of 47 patients, which include 41 (87.2%) male and 6 (12.7%) female, were included in the study. The calculated mean age was found to be 46.73 years (8–78 years). The mean AL of the eyes was 23.53+1.86 (range 21.49–30.03 mm).

Of the 49 eyes, 29 had diabetic retinal detachment (tractional or rhegmatogenous or combined), 10 had myopic rhegmatogenous retinal detachment, 5 had traumatic retinal detachment, 3 had retinal detachment associated with retinochoroidal coloboma, 2 had acute retinal necrosis, 3 had Coats’ disease, familial exudative vitreoretinopathy and Eales’ disease.

The mean BCVA before SOR was log MAR 1.3 (reference range 0.6–2.0) and postoperative refraction outcome was log MAR 0.8 (reference range 0.2–2.0). Statistical observation reveals significant correlation between BCVA before and after SOR (P = 0.002). Significance was observed in the correlation for aphakic eyes (P = 0.001), but such statistical significance was not found in phakic eyes (P = 0.125).

The calculated mean predicted refraction was −0.40 D (0.28 diopters (D)), whereas mean observed postoperative refraction (spherical equivalent) was −0.75D (1.09 D), and the mean difference between these refractions was −0.34D (range −4.5 to +2.75 D) [Table 1]. In aphakics, the mean (SD) difference between predicted and postoperative spherical equivalent was −0.91D (1.67 D), whereas in phakics it was −0.18 D (0.84 D) when calculated using OLCR. OLCR accuracy being more accurate within the phakic subgroup (P = 0.08) is the sole distinction between the aphakic and phakic groups. During SOR, 38 eyes (77.6%) were found phakic and all had undergone in-the-bag IOL implantation, whereas the remaining 11 eyes (22.4%) were aphakic [Figure 1] with secondary IOL implantation. Among the 11 aphakic eyes, 3 had in-the-bag fixation, 4 had ciliary sulcus fixation, and 4 had scleral fixation of IOL [Figure 2].

Table 1 Accuracy of refractive outcomes

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Figure 1 Showing comparison of the accuracy of predicted refraction in both phakic and aphakic subgroups. The dashed line (1:1 line) indicates a point where observed refraction = predicted refraction. A significant difference was observed in refractive outcome between both groups (P = 0.03).

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Figure 2 Showing comparison of the accuracy of predicted refraction between in-the-bag, sulcus fixated, and SFIOL subgroups. The dashed line is a point where observed refraction = predicted refraction. Difference in refractive outcome was not significant in these three groups (P = 0.88).

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The postoperative refractive outcomes were quite accurate when measured with OLCR: of the 49 eyes, 36 (73.5%) had predicted refraction within 1.0 D and 13 (26.5%) had more than 1.0 D (>1.0–4.50 D). Out of 13 eyes, >2.0 D difference was seen in 5 eyes that had preexisting etiology of aphakia, traumatic RD in 4 eyes, and dense cataract with ARN-associated RD in 1 eye. Poor cooperation and dense cataract were the causes for residual postoperative refractive error in these cases.

Thousand cSt of silicone oil viscosity was used in all eyes except one eye (ARN with multiple RD surgeries) where 5000 cSt was used. Emulsification of oil was noted in four cases and the refractive outcome was not compromised in those cases.

Discussion

IOL power calculation is very challenging in silicone oil-filled eyes due to optical and sound attenuation properties of silicone oil. Various techniques have been proposed to calculate true AL and IOL power in silicone oil-filled eyes.^[4],[5],[6] First commercially available noncontact biometry was IOL master; it uses partially coherence interferometry to measure AL and there is no assessment of corneal, lens, or retinal thickness.^[7] Newer noncontact biometer LENSTAR LS-900 using the principle of OLCR, powered with a superluminescent diode (SLD), is used to calculate precise AL in normal as well as uncommon cases like eyes with high myopia, staphyloma, and silicone oil.^[8],[9] It measures distance from the corneal apex to the retinal pigment epithelium, thereby giving accurate AL measurement.

This study indicates that the postoperative refraction was accurate when LENSTAR was used to calculate AL in silicone oil-filled eyes. The literature search acknowledge that a few studies were done to assess the precise biometry of LENSTAR device^[8],[9],[10] in cataractous eyes. However, studies related to the effect of silicone oil on predicting refractive outcome was not known. Previous study by Suk et al.^[11] reported the mean deviation from predicted refraction with IOL master was −0.97 D more myopic; another study by Tayyab et al.^[3] reported postoperative refraction in IOL master was 0.70±0.32 D, whereas conventional A scan group was 1.55±0.98 D. In our study, mean difference in the postoperative refraction from predicted was −0.34 D less myopic.

Emulsification is a known complication of silicone oil. Less viscous silicone oils emulsify faster than the high viscous. In our study, low-viscosity silicone oil was used in most of the cases and SOR was performed within 4 months, for whom postoperative outcome was good. Emulsification occurred in four cases where follow-up was irregular and postoperative refraction were not good. There are possibilities of some amount of emulsified silicone oil to decrease the optical signal in visual axis, thereby affecting the accuracy of postoperative refractive outcome.^[12],[13]Patients with dense cataracts, poor fixation, and inability to cooperate were the causes of measurement failure. In our study, four cases had measurement failure due to dense cataracts. Buckhurst et al.^[8] demonstrated 9–10% failure rate in cataractous eyes with both IOL master and LENSTAR devices and attributed AL acquisition failures to dense media opacities. Various conditions such as scleral buckling, macular thickening, and posterior staphyloma may limit the accuracy of predicted refraction due to inaccurate AL measurement.^[14] Studies have reported that measurement with LENSTAR in such conditions is more reliable than the conventional ultrasound. Our study included cases with scleral buckling and the results were almost similar to the predicted readings.

This is a retrospective, noncomparative study limiting the results. The device is unable to measure accurately in severely compromised eyes, such as those with dense opacities along the visual axis and poor patient cooperation.

Conclusion

LENSTAR is a safe device that provides precise biometry and IOL power calculation in silicone oil-filled eyes. It is a more reliable method in silicone oil-filled eyes undergoing phacoemulsification with IOL implantation to predict accurate postoperative refractive error.

Acknowledgement

I am thankful to the “Mr. Krishnaiah”, the biostatistician for the final analysis and compilation of results.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	Cibis PA, Becker B, Okun E, Canaan S. The use of liquid silicone in retinal detachment surgery. Arch Ophthalmol 1962;68:590-9.
2.	Holekamp NM, Shui YB, Beebe DC. Vitrectomy surgery increases oxygen exposure to the lens: a possible mechanism for nuclear cataract formation. Am J Ophthalmol. 2005;139(2):302-10.
3.	Tayyab H, Haider Muhammad Ali, Jahangir T. Intraocular lens power calculation in silicone oil filled eye: IOL master versus A-mode acoustic biometry. Pak J Ophthalmol 2017;33(1):4-8.
4.	Hoffer KJ. Ultrasound velocities for axial eye length measurement. J Cataract Refract Surg 1994;2(5):554-62.
5.	Murray DC, Potamitis T, Good P, Kirkby GR, Benson MT. Biometry of the silicone oil-filled eye. Eye 1999;13:319-24.
6.	Grinbaum A, Treister G, Moisseiev J. Predicted and actual refraction after intraocular lens implantation in eyes with silicone oil. J Cataract Refract Surg 1996;22(6):726-9.
7.	Santodomigo-Rubido J, Mallen EAH, Gilmartin B, Wolffsohn JS. A new non-contact optical device for ocular biometry. Br J Ophthalmol 2002;86:458-62.
8.	Holzer MP, Mamusa M, Auffarth GU. Accuracy of a new partial coherence interferometry analyzer for biometric measurements. Br J Ophthalmol 2009;93(6):807-10.
9.	Buckhurst PJ, Wolffsohn JS, Shah S, Naroo SA, Davies LN, Berrow EJ. A new optical low coherence reflectometry device for ocular biometry in cataract patients. Br J Ophthalmol 2009;93(7):949‑53.
10.	Epitropoulos A. Axial length measurement acquisition rates of two optical biometers in cataractous eyes. Clin Ophthalmol 2014;8:1369-76.
11.	Suk KK, Smiddy WE, Shi W. Refractive outcomes after silicone oil removal and intraocular lens implantation. Retina 2013;33:634-41.
12.	Williams RL, Day M, Garvey MJ, English R, Wong D. Increasing the extensional viscosity of silicone oil reduces the tendency for emulsification. Retina 2010;30(2):300-4.
13.	Patwardhan SD, Azad R, Sharma Y, Chanana B, Tyagi J. Intraoperative retinoscopy for intraocular lens power estimation in cases of combined phacoemulsification and silicone oil removal. J Cataract Refract Surg 2009;35:1190-2.
14.	Kim SJ, Martin DF, Hubbard GB III, Srivastava SK, Yan J, Bergstrom CS et al. Incidence of postvitrectomy macular edema using optical coherence tomography. Ophthalmology 2009;116(8):1531-7.