|Year : 2013 | Volume
| Issue : 2 | Page : 28-30
Silicone oil induced high astigmatism in a pseudophakic vitrectomized eye
Mostafa Hamed Nabih, Ahmed Abd Allah Mohalhal
Department of Ophthalmology, Faculty of Medicine, Cairo University, Egypt
|Date of Web Publication||24-Jun-2014|
Ahmed Abd Allah Mohalhal
Department of Ophthalmology, Faculty of Medicine, Cairo University
Source of Support: None, Conflict of Interest: None
A 66-year-old male lawyer with dropped whole nucleus during phacoemulsification procedure. He was hepatitis C virus positive, international normalized ratio 1.5, prothrombin concentration 60%, and coagulation time 15.5 s. Positive predictive value was done, nucleus was removed with sleeveless phaco needle through pars plana, an AcrySof three piece intraocular lens (IOL) was implanted in the ciliary sulcus. Postoperative sustained vitreous haze required silicone oil injection. One day postoperatively, vision was counting fingers again, opened posterior capsule, clear fundus details. Refraction revealed: −8 × 120 astigmatic error correcting the patient to 0.2 vision (decimal fraction) with uniocular diplopia; as the patient claimed. Corneal topography revealed minimal corneal astigmatic error. By revising patient's clinical data, the IOL was perfectly in the sulcus supported by a remarkably thick anterior capsule. The capsulorhexis opening has changed into an oval one with a long axis almost the same as that of negative cylinder, 2 months later silicone oil was removed. The unaided vision of this eye returned to 0.9 to be corrected to 1.0 with +0.75 cylinder at 20.
Keywords: Astigmatism, pseudophakia, silicone oil
|How to cite this article:|
Nabih MH, Mohalhal AA. Silicone oil induced high astigmatism in a pseudophakic vitrectomized eye. Egypt Retina J 2013;1:28-30
| Introduction|| |
The use of silicone oil as a long acting retinal tamponade has improved the chances of keeping the retina attached and improved the management of complicated cases. Unfortunately, the intraocular silicone has a variety of complications. 
Silicone oil has a refractive index (1.4035), which is slightly higher than that of vitreous (1.33).  Hence, it causes refractive changes, these changes are determined by the shape of the anterior surface of the silicone bubble, and positioning of the patient. A negative lens effect occurs in the phakic eyes due to the concavity produced by the posterior lens surface. Consequently, the eye becomes more hyperopic. Aphakic eyes experience a myopic shift due to the convexity of the anterior bubble surface. 
In the supine position, the oil separates from retina producing a positive posterior surface contributing to myopia, more effect occurs in aphakic eyes. 
Conventional sclerotomies are always accompanied by temporary postoperative astigmatism secondary to suture closure, tunnel incisions rarely give rise to astigmatism and lead only to a slight postoperative inflammatory reaction. 
Visually disabling astigmatism present after surgery is almost certainly a rare, wound-related complication of positive predictive value (PPV), but remains a previously unappreciated possibility in eyes undergoing repeated procedures through the same sclerotomies. 
| Case Report|| |
A 66-year-old male lawyer with dropped whole nucleus during phacoemulsification procedure. He was hepatitis C virus positive, international normalized ratio 1.5, prothrombin concentration 60%, coagulation time 15.5 s. PPV was done, nucleus was removed with sleeveless phaco needle through pars plana, an AcrySof three piece intraocular lens (IOL) was implanted in the ciliary sulcus.
Postoperative examination on day one revealed vision of counting fingers (CF), opened posterior capsule and vitreous hemorrhage, with a follow-up of 1 month there was no improvement, US revealed suspected retinal detachment, hence a decision to perform PPV, and silicone oil was injected due to sustained oozing of blood from sclerotomy sites at the end of the procedure.
To our astonishment, 1 day postoperatively, vision was CF again, despite open, clearly visible fundus details. Auto refractometer did not give a reading.
Manual refraction revealed: −8 × 120 astigmatic error correcting the patient to 0.2 vision (decimal fraction) with uniocular diplopia; as the patient reported. It was speculated if this astigmatism is due to the PPV sclerotomies or scarring due to diathermy versus the astigmatism produced by the phaco procedure as corneal wound burn, wound healing,  or IOL tilt, so corneal topography was performed revealing a minimal corneal astigmatic error [Figure 1].
|Figure 1: Corneal topography revealed minimal corneal astigmatism with steep: 43.1 D at 24°; fl at: 43.95 D at 114°; astigmatism: 0.85 D|
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By revising patient's clinical data, the IOL was perfectly in the sulcus supported by a remarkably thick anterior capsule. The capsulorhexis opening has changed into an oval one with a long axis almost the same as that of the negative cylinder [Figure 2] and [Figure 3]a].
|Figure 2: Postoperative anterior segment photograph. Thickened edge of opened posterior capsule (black arrow)|
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|Figure 3: (a and b) Diagram showing the suggested mechanism of astigmatism induction|
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The interfacial tension between the oil and aqueous always forces the surface of the oil globe to assume smooth curves. Hence, an assumption was made that the anterior surface of the silicone oil bulging through the oval shaped thickened edges of the anterior capsule has produced a strong positive cylindrical lens effect requiring this −8.0 diopter lens to neutralize [Figure 3]b]. Based on this assumption, the patient was reassured that this temporary optical that is going to be automatically solved with oil removal.
Two months later, silicone oil was removed through 20 guage radial sclerotomies. The unaided vision of this eye returned to 0.9 to be corrected to 1.0 with +0.75 cylinder at 20.
| Conclusion|| |
Surgeons should be alert that the shape of anterior surface of silicone oil can induce concave or convex lens effect in phakic or aphakic patients respectively, and also it can induce a cylindrical lens effect if the anterior surface of silicone oil is shaped by an oval opening of the posterior capsule producing a s cylindrical lens effect that may be strong enough to produce visual disability. Anyhow, this effect is reversible with silicone oil removal.
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[Figure 1], [Figure 2], [Figure 3]