Mastering the Techniques of Lens Based Refractive Surgery (Phakic IOLs) Ashok Garg, Jorge L Alio, Dimitrii Dementiev, Antonio A Marinho
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Lens Based Refractive Surgery: When and Why1

Ashok Garg
(India)
 
INTRODUCTION
Lens based refractive surgery is certainly a growing segment of refractive surgery for last few years. It has gained world wide acceptance and popularity. Refractive surgery is usually classified in two categories.
  1. Corneal based refractive surgery in which refractive surgery is done by lasers by corneal reshaping. PRK, Lasik and Lasek are standard procedures in this group.
  2. Lens based refractive surgery in which refractive surgery is done either by altering the natural lens or by placing an intraocular lens inside the eye in front of patient's natural lens.
Refractive lens surgery techniques are essentially the same as for cataract surgery. It is a rewarding procedure both for the patient and the ophthalmologist. It allows the surgeon to efficiently and effectively correct otherwise untreatable refractive errors such as extreme myopia and hyperopia. Refractive lens surgery (RLS) uses the same successful and familiar techniques developed for cataract surgery to treat refractive errors. RLS is a process not a procedure.
 
HISTORY OF REFRACTIVE LENSES
  1. Drs Strampelli and Barraquer in 1950s introduced a biconcave angle supported lens. However, these lenses were discarded due to serious angle and endothelium related complications.
  2. Dr Dveli in 1980s restarted phakic myopia lenses with 4 soft angle supported loops but these lenses also had drawbacks.2
  3. Dr Georges Baikoff from France in 1980s introduced an angle supported myopia lens with Kelman type haptics.
  4. Dr Jan worst and Fechner in 1986 introduced phakic myopia lens of iris claw design. This lens is a peripheral iris fixated anterior chamber lens which has gained popularity. It is now available as verisyse phakic IOL commercially.
  5. Professor Fyodorov from Russia in 1986 introduced the concept of soft phakic lens in the space between the iris and the anterior surface of the crystalline lens and is now available as an implantable contact lens (ICL) commercially.
Professor Charles D Kelman was a great visionary who early saw the refractive potential of cataract surgery. He understood that reliable and refined refractive outcomes would have a start with a small incision. This is the vision that led him to develop phaco. Refractive lens exchange would not have been possible without phaco.
There is close ties between the history of phakic IOLs and that IOLs in general since the days of Dr Ridley who first designed the IOL for the correction of aphakia, the potential of the IOL for the correction of ametropia was readily apparent. Today there is marked improvement in design and material of phakic IOLs which have enhanced the safety and efficacy of lens based refractive surgery with better clinical outcome.
Today phakic refractive lenses are available in three styles.
  1. Anterior chamber angle fixated IOLs
  2. Iris supported phakic IOL
  3. Plate lens that fits between the Iris and the crystalline lens.
 
INDICATIONS FOR REFRACTIVE LENS SURGERY
  • Patients not suitable for Lasik/Lasek due to high powers or thin corneas (Extreme Myopia or Hyperopia)
  • To correct ametropia in the Presbyopic age
  • Endothelial count more than 2000 cells/cmm
  • Stable refraction for one year
  • Age above 18 years
  • AC depth more than 3 mm.
 
CONTRAINDICATIONS FOR RLS
  • Corneal dystrophy/Endothelial cell count <2000 cells/cmm
  • Anterior chamber depth less than 3 mm
  • Pathological myopia
  • Presence of anterior/posterior synechiae
  • History of uveitis
  • Persistant glaucoma
  • Evidence of nuclear sclerosis
  • Family history of retinal detachment
  • Diabetes mellitus.
However in above contraindications some are relative on the discretion of the surgeon and the patient requirement.
 
ASSESSMENT FOR REFRACTIVE LENS SURGERY
 
Preoperative
Complete and careful preoperative ophthalmic check-up is necessary for better postoperative visual outcome. Following examinations are mandatory. These include–
  1. Objective and subjective refraction.
  2. Complete anterior and posterior segment examination-slit lamp, direct and indirect ophthalmoscopy are vital to rule-out any pathological conditions).
  3. Anterior chamber depth (ACD) analysis.
  4. Specular microscopy for endothelium status.
  5. K-readings and topography by orbscan.
  6. Intraocular pressure (IOP) status.
Ophthalmologists prefer topical anesthesia for lens based refractive surgery as peribulbar and retrobulbar anesthesia carry the potential risk of globe perforation in high myopic eyes. Parabulbar and general anesthesia are other alternatives.
 
Postoperative Assessment
Postoperative assessment is crucial in every operated case of RLS for the successful refractive outcome.3
Generally patients are assessed at first postoperative day (Day +1), first week, 15 days, one month, 3 months and one yearly check-ups. On each visit patient should be examined for –
  • Visual acuity status
  • IOP measurement
  • Slit lamp examination for IOL position and enclavation.
  • UCVA, BCVA and Residual refractive error.
  • Postoperative astigmatism.
  • Contrast sensitivity.
  • Specular microscopy.
  • Corneal status.
 
ADVANTAGES OF LENS BASED REFRACTIVE SURGERY OVER LASER CORRECTIVE PROCEDURES
  • A higher range of refractive errors can be corrected specially extreme myopia and hyperopia which are not treatable with laser surgery
  • Lens based refractive surgery is a potentially reversible procedure
  • RLS is totally safe procedure as no structural changes are induced hence safe in patients with high refractive errors and their corneas
  • Contrast sensitivity is marked better with RLS as compare to laser refractive procedures in eyes with higher refractive errors. There is marked improvement in BCVA with these lenses because of the magnification factor
  • RLS is a highly skilled procedure so prevents misuse of the procedure
  • RLS is quite effective in presbyopia with newly developed accommodating implants, multifocal implants and blended vision implants.
Lens based refractive surgery is a safe procedure. There is tremendous improvement in design and material of refractive lenses which have enhanced the safety and efficacy of the procedure with better visual outcome. With the advent of liquid injectable IOLs, improved surgical techniques and better diagnostic technologies, lens based refractive surgery should be available in the armamentarium of every refractive surgeon to correct entire range of refractive errors to provide safe and stable refractive vision to the patients. RLS is quite revolutionary to provide refractive correction and maintains accommodation. With further ongoing research works and modifications in refractive lens surgery techniques, I am sure it shall be procedure of choice for catarefractive surgery in near future.