|Year : 2013 | Volume
| Issue : 2 | Page : 93-96
Secondary toric intraocular lens implantation for post-operative ammetropia and astigmatism after small incision cataract surgery
Rajesh Subhash Joshi
Department of Ophthalmology, Vasantrao Naik Government Medical College, Yavatmal, Maharashtra, India
|Date of Submission||18-Nov-2012|
|Date of Acceptance||14-Feb-2013|
|Date of Web Publication||20-May-2013|
Rajesh Subhash Joshi
77, Panchtara HSG. Society, Manish Nagar, Somalwada, Nagpur - 440 015, Maharashtra
Source of Support: None, Conflict of Interest: None
We report a case of 56-year-old female who had undergone left eye small incision cataract surgery 2 months earlier with history of no visual gain uncorrected after surgery. On examination, she had a superior scleral tunnel incision with 6.5 mm optic poly methyl metha acrylate (PMMA) posterior chamber intraocular lens (IOL) in the bag. Her manifest refraction was -5.0 diopter sphere and -3.0 diopter cylinder (DC) at 180°. Her visual acuity improved from 20/200 to 20/20 after correction. The patient underwent explanation of the PMMA IOL with implantation of 23.5 D Acriol EC-T4 toric IOL through temporal clear corneal incision. Postoperatively, at 6 months, the patient had 20/20 (p) visual acuity uncorrected improving to 20/20 after correction by -0.25DC at 40°. Postoperative ammetropia and high cylindrical power can be simultaneously corrected by placement of the toric IOL.
Keywords: Explantation of intraocular lens, intraocular lens power calculation, toric intraocular lens
|How to cite this article:|
Joshi RS. Secondary toric intraocular lens implantation for post-operative ammetropia and astigmatism after small incision cataract surgery. J Clin Ophthalmol Res 2013;1:93-6
|How to cite this URL:|
Joshi RS. Secondary toric intraocular lens implantation for post-operative ammetropia and astigmatism after small incision cataract surgery. J Clin Ophthalmol Res [serial online] 2013 [cited 2020 May 29];1:93-6. Available from: http://www.jcor.in/text.asp?2013/1/2/93/112186
The aim of cataract surgery is to improve visual acuity.  Continuous development and technological advancements demand for better results by the patients and the surgeon after cataract surgery.
Inaccurate intraocular lens (IOL) power calculation, faulty IOL power implanted in the eye after cataract surgery and induced astigmatism or no consideration to the correction of the preoperative existing astigmatism give rise to suboptimum visual gain after cataract surgery. Various treatment options available in these cases are supplementation of the residual spherical and the cylindrical power in the spectacle, toric contact lenses, rigid gas permeable lenses, laser refractive surgery (PRK or Lasik),  piggyback toric IOL in the ciliary sulcus,  explantation of the IOL, and replacing it with an adequate power.  Studies have shown safety and effectivity of toric IOL in patients having cataract with astigmatism. ,
To the best of our knowledge, no previous reports regarding explantation of the polymethylmethacrylate (PMMA) IOL and the placement of the foldable toric IOL for the correction of the spherical and the cylindrical power in-patient with postoperative ammetropia have been reported.
| Case Report|| |
A 56-year-old female presented with inability to see distant object with left eye without wearing spectacle. She had undergone small incision cataract surgery with the implantation of the PMMA intraocular lens (IOL) in her left eye 8 weeks ago.
On examination, her distant visual acuity on Snellen's chart was 20/200 improving to 20/20 with -5.0 diopter (D) sphere and -3.0 diopter cylinder (DC) at 180°. Slit lamp examination of left eye revealed 7 mm length superior scleral incision 1.5 mm away from the limbus. Cornea was clear. Anterior chamber was normal depth. On pupillary dilatation non-foldable IOL with 2 dialing hole was seen in the bag. The capsulorrhexis was intact and the approximate size was 6 mm. No capsular contraction was noted. Retinal examination was normal. Intraocular pressure measured with Perkin's applanation tonometer was 14 mm of Hg. Keratometry on auto-refractometer was K1 47.75 D at 178°, K2 50.50 D at 88° with preoperative corneal astigmatism of +2.75 D at 88° (keratometry reading before performing small incision cataract surgery available from the patient's record was k1 45.25D at 180° and k2 47.50 D at 90°). Average keratometry reading of 49.13D was used for the IOL calculation. The axial length calculated on immersion mode of the A-scan (Quantel Medical, France) was 20.50 mm. A- constant recommended by the company (Care Group, India) was 118.8. The power of IOL was 23.33D. The data were feed in a toric IOL calculator. The surgically induced astigmatism (0.50 D) for second surgery was considered. As per the calculation, the IOL recommended was Acriol EC-T4 (Care Group, India) with cylindrical power 2.80 D at the corneal plane. Anticipated residual astigmatism was 0.42 D at 88° [Figure 1]. The preoperative 3, 6, and 9 o' clock markings were made with Nuijts reference corneal marker under topical anesthesia under slit lamp to avoid cyclorotation during intra-operative period. Preoperatively, a drop of 0.5% proparacaine hydrochloride was instilled every 5 min for 15 min in the eye to be operated. Subconjunctival injection of 0.5 ml 2% lignocaine, dexamethasone and gentamycin were given before start of the surgery. The patient underwent explantation of the 6.5 mm PMMA IOL through the existing superior scleral incision. The IOL was brought out into the anterior chamber and was removed as a whole [Figure 2]. During the process pupil became miosed. 1% preservative free lignocaine (0.5ml) was injected in the anterior chamber for pupillary dilatation. The surgeon shifted to the temporal side for the implantation of the toric IOL. We preferred temporal clear corneal incision in spite of open superior scleral tunnel due to possibility of wound leakage during implantation of IOL. A side port incision was taken at 6 o' clock position. A 2.8 mm
clear corneal temporal incision was fashioned at 180°. Anterior chamber was filled with 1.4% sodium hyaluronate (Cohevisc, Appasamy Ocular Devices, India). Intraoperatively, location of the corneal incision and axis of IOL placement was marked using Mendez ring and Nuijts toric axis marker. IOL was folded in the cartridge and injected in the capsular bag with the axis of the IOL aligned around 10° short of the final axis of alignment (88°). Viscoelastic removal was done along with final rotation of the IOL, and the axis aligned [Figure 3]. Side ports and clear corneal incisions were hydrated. Postoperatively, the patient was reviewed on 1, 3, 15 days, 6 weeks, and 6 months. Postoperative day-1, the cornea was clear with well-formed anterior chamber and well-centered aligned IOL. Refraction 6 weeks postoperative was -0.25 DC at 40°, vision improving to 20/20 on Snellen's visual acuity chart. Intraocular pressure by Perkin's hand held tonometer was normal. No rotation of the IOL was noted. The patient was examined at 6 months follow-up and has best-corrected visual acuity (BCVA) of 20/20 and no rotation of IOL.
| Discussion|| |
Modern cataract surgery has become a refractive procedure. Recent studies suggest that astigmatism may affect vision even more than the spherical component in the refractive error.  It is conventionally accepted that 0.50 D of astigmatism is roughly equivalent to 0.25 D of spherical error and changes high-contrast visual acuity by approximately 1 log MAR line. 
Residual astigmatism after cataract surgery can be corrected by different techniques: classic limbal relaxing incisions, easy to perform but with limited precision, laser refractive surgery (PRK or Lasik), additionally allowing for correction of spherical equivalent, piggyback toric IOL in the ciliary sulcus.  Short-term study by Falzon et al. on correction of residual pseudophakic error by Sulco-flex IOL has shown promising results.  However, long term follow up of these lenses in terms of the safety is lacking. Effectivity and the stability of the toric IOL have been proved in various studies. ,
In our patient, pre-existing astigmatism and an induced spherical component lead to the no visual gain uncorrected. We decided to explant the IOL and replacing it with an appropriate power IOL and at the same time correcting the cylindrical power with implantation of the toric IOL. Limbal relaxing incisions could have helped to reduce the astigmatism. However, corneal wound healing variations particularly at epithelial level are associated with poor refractive results predictability. New generations of toric IOLs have a good stability in the capsular bag with less risks of secondary rotation. Well positioned in the right axis, toric IOLs have potentially better accuracy and predictability than relaxing corneal surgery to correct pre-existing congenital astigmatism. 
This patient had a spherical component of the refractive error also (-5.0D). We calculated the power of IOL from the available patients record (K1 45.25D at 180° and K2 47.50 at 90°, axial length 21.59 mm and A constant 118.0). The IOL power was 22.35 D by SRK-2 formula, similar to what we calculated (23.33 D, A constant = 118.8). The discharge card was having a sticker of 27.0D as the implanted IOL. Patient did not have a print copy of the A-scan report. Ammetropia in this case could be either due to operating room nurse giving wrong power IOL or wrong keratometry reading feed in the A-scan. Operating and assistant surgeon failed to recognize the wrong power of the IOL during implantation.
We could have thought of piggyback or sulco-flex lens to correct both the components of the refractive error simultaneously. But we did not have an adequate experience about these lenses and the ideal position of the artificial lens is in the capsular bag. Therefore, we performed explantation of the IOL.
Explantation of the IOL from the bag does require a skill. Chances of corneal endothelial damage, zonular dehiscence, and posterior capsular rupture are always prevalent. Use of high viscosity viscoelastic does help to prevent these problems as the anterior chamber is formed throughout the procedure. This patient was presented to us early. There was no difficulty in opening the existing scleral wound. Swiping the iris repositor underneath the superior scleral lip helped to open the scleral wound. We did not face difficulty in rotation and the removal of IOL from the bag. Cutting the IOL into pieces is the ideal way to remove it from the anterior chamber. However, implanted IOL was made up of rigid material. We preferred scleral wound for the explantation of IOL as 6.5 mm optic IOL could have required large corneal wound.
This patient achieved best corrected visual acuity of 20/20 with final correction of -0.25DC 40° at 6 months. There were no postoperative complications and no rotation of the IOL was noted.
In conclusion, toric IOL could be a good option for patients having postoperative ammetropia along with high cylindrical power. We recommend proper IOL power calculation and due consideration to the keratometry readings before proceeding for the cataract surgery. Surgeon and the assistant should check the IOL power written on the case sheet and the power of the IOL during the implantation procedure.
| Acknowledgement|| |
I acknowledge Care Group, India for providing free IOL to this poor and needy patient.
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[Figure 1], [Figure 2], [Figure 3]