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Coneal topography stability following 2.2 mm clear corneal phaco- emulsificaiton . Mohamed Hesham Aly , MD, FRCS Ed. ( Magrabi eye Hopital ) Bassel Atallah , OD ( Magrabi eye Hopital ).
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Mohamed HeshamAly, MD, FRCS Ed.
(Magrabi eye Hopital)
(Magrabi eye Hopital)
Neither the author nor the co- author has any financial interest in the items and products mentioned in this study.
Refractive surgery may be required post phaco-emulsification to correct residual astigmatism or miscalculated IOL power. The timing for the procedure should be decided after the corneal stability post phacoemulsification. A study was made to decide the time needed for the corneal topography to stabilize to be able to proceed for Excimer laser corrections.
Residual error corrections post phaco surgery, using Excimer laser correction, can be considered 2 months postoperatively. At this time most of the corneal topography changes should be stabilized.
A total of 26 patients (26 eyes) between the ages of 36 and 85 years (mean age: 60.52years) were followed up for 6 months. A 2.2-mm clear temporal (180 degree) corneal tunnel phacoemulsification/ IOL implantation was performed on the 26 eyes. Selection criteria included good general health, absence of corneal pathology during slit-lamp microscopy examination, no previous corneal or scleral surgery, absence of severe retinal pathology that could affect the infrared ray reflection from the macula during ocular wavefront aberration measurement, and no complications during or after surgery. An explanation of the study was given to all patients and informed consent obtained.
Clinical examinations were conducted preoperatively and at 1 day, 1 weeks, 1 month, 3 months, and 6 monthsafter surgery. Clinical examination included best spectacle-corrected visual acuity (BSCVA) and uncorrectedvisual acuity (UCVA), manifest and cycloplegic refractions, intraocular pressure, and anterior and posteriorsegment evaluation. The corneal astigmatism and high order aberrations were measured using the NIDEKOPD-Scan aberrometer/topographer (NIDEK Co Ltd, Gamagori, Japan), which uses skiascopy-based ocularaberrometry using 1440 infrared points and placid disk corneal topography.7 The OPD-Station software(NIDEK Co Ltd) was used to isolate corneal aberration out to the sixth order.
Endocapsular phacoemulsification of the nucleus with Phacochop technique and cortical aspiration were performed using an Infinite(Alcon Laboratories). The anterior chamber and the capsular bag were refilled with Duovisc. A foldable IOL was inserted into the capsular bag using an injector cartridge system.
The residual viscoelastic material was removed using bimanual irrigation/aspiration hand pieces. Balanced salt solution was injected through the paracentesis to maintain the anterior chamber. At the end of surgery, the wounds was checked and found to be watertight. All surgeries were completed without sutures. Postoperatively,all patients were treated with topical 0.1% Tobradex (Alcon Laboratories) and 0.1% Vigamos eye drops(Alcon Laboratories) every 2 hours for one week, then reduced gradually over one month period.
Average pre-operative astigmatism was -0.935385 Dioptre. One day post-operatively, the average astigmatic error was -1.685384615 Dioptre. One week, one month, 2 months, 3 months, and 6 months post-operative astigmatic errors were -1.444615385, -1.335833333, -1.104615385, -1.033076923, and -1.02349804 respectively.
The average RMS pre-operatively was 0.538461538. The average RMS 1 day, 1 week, 1 month, 2 months, 3 months, and 6 months post-operatively were respectively:
The optical quality of the pseudophakic eye is determined by the combination of corneal and internal aberrations generated by the IOL and those induced by surgery. Spherical aberration is determined by the corneal asphericity.
In this study, corneal astigmatism and high order aberrations stability were evaluated over 6 months as measure of change in the cornea after cataract surgery. The need of the residual astigmatic and spherical aberration post-operatively corrections depends on the stabilization of these errors. Any premature correction may lead to augmentation or irregularities of these errors.