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Pseudophakic anisometropia may cause significant patient dissatisfaction with marked visual problems. Correction methods include contact lenses, intraocular lens (IOL) exchange, piggybacking a supplementary IOL, and corneal refractive surgery.
The following case describes the successful management of pseudophakic anisometropia using an ICL in a patient with high myopia and pseudoexfoliation.
An 80 year old woman was referred to us for correction of pseudophakic anisometropia. She had bilateral pseudoexfoliation and was highly myopic, her original refraction being −14.00 DS right eye, −13.50/+1.75×20 left eye.
In 1989 she underwent left cataract extraction with posterior chamber IOL, keeping her highly myopic (−13.00/−2.00×105 left eye).
She subsequently developed cataract in her right eye so underwent uncomplicated right phacoemulsification with posterior chamber lens implantation, leaving her +1.00/−1.00×45 in her right eye.
Because of her marked anisometropia she experienced visual difficulties unresolved with spectacles or contact lenses, so she requested permanent correction of this.
Refraction, keratometry, corneal thickness (using pachymetry), axial length (using ultrasound), anterior chamber depth, and horizontal white to white diameter (using Orbscan), were measured and sent to Staar Surgical who calculated the ICL power.
A −19.0 Dioptre Staar Collamer ICL was inserted via an injector into the left sulcus, anterior to her posterior chamber IOL, through a corneal tunnel. Two iridotomies were made. Antibiotic and steroid drops were used postoperatively.
Postoperative refraction was right eye +1.00/−1.00×45 6/12, left eye +3.00/−1.00×105 6/12+2. Her symptoms resolved and she was extremely pleased.
Insertion of a Staar Collamer ICL seems to be an effective alternative method for correcting anisometropia in pseudophakic patients.
All surgical options have their risks and complications.
Supplementary anterior chamber lenses risk corneal endothelial cell loss,4–6 pupil abnormalities, and they need larger incision sizes. Posterior chamber IOLs can be used in “piggyback,”7 but may risk interface opacities.
IOL exchange can be difficult, especially if performed some years after the original surgery where the capsular bag has shrunk around the IOL,1 increasing the risk of capsular damage with subsequent vitreous loss, and zonule damage, especially important in patients with pseudoexfoliation whose zonules are already weak.
A main complication using ICLs is pupillary block glaucoma.8–10 It can be avoided by performing adequate iridectomies peroperatively. Other side effects include glare, halos and lens decentration (minimised if accurate white to white diameter is measured in order to get an accurate fit).1
Advantages include ICL power calculation being based on actual refraction so repeat biometry is not required. There is no ICL/IOL touch because of vaulting of the ICL and so perhaps less risk of interface opacities.1,7 The operation is minimally invasive with a small incision, as ICLs are thinner than other IOLs (60 μm) and more flexible. The small incision size (3 mm) reduces further astigmatism.
ICL power and diameter calculations made by Staar are devised for phakic eyes. No alterations were made for our pseudophakic patient. This may lead to error, though the six patients of Hsuan et al1 had no major errors.
Our patient was slightly hyperopic, probably because of the different ciliary sulcus anatomy in pseudophakic patients, accentuated further by pseudoexfoliation.
It is better to prevent postoperative refractive surprises, but if they do occur, insertion of an ICL can be used to correct pseudophakic anisometropia, especially in patients with pseudoexfoliation.
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