Dr Ian Anderson's
Eye Site

Refractive Surgery Overview

As all refractive surgical procedures are relatively new not all the possible complications are yet known. When considering an operation that must last the rest of your life some assessment of the potential very long term complications must be undertaken. Unfortunately life long results are not available but some idea of trends may be obtained by noting the length of time the procedure has been performed These notes are not an attempt to list all possible complications but rather to act as a guide for further discussions with your ophthalmologist. Because of the ongoing nature of studies any rates quoted should not be considered absolute but rather an indication of currently observed trends. All refractive surgical techniques are under continual development and evaluation for safety and efficacy. There are two distinct forms of refractive surgery Corneal surgery and Lenticular surgery and in some situations a combination of both types may be required (this has been termed Bioptic ).

CORNEAL SURGERY

Corneal surgery is based on an attempt to alter the shape of the central cornea overlying the pupil. The anterior surface of the eye accounts for 67% of the total ocular refraction so minor changes in the corneal surface cause major changes in refraction. Surgery induces a change in the central corneal shape that alters the focusing power of the cornea thus correcting the refractive error. If the cornea continues to change in the shape then the refractive outcome will continue to alter. The final result is dependant on predicting and achieving a stable new corneal shape. Healing and scarring can reduce the final visual result. If the area of the reshaped cornea is less than the dilated pupil then there may be visual problems in dim light. Note these procedures all cause irreversible changes in the cornea

Some of the currently available techniques are -

  • 1)Laser Refractive Surgery
    • a)Photorefractive Keratectomy (PRK)
    • b)Laser Assisted In Situ Keratomileusis ( LASIK)
    • c)Laser Epithelial Keratomileusis (LASEK)
  • 2) Conductive Keratoplasty (CK)
  • 3) Astigmatic Keratotomy
  • 4) Radial Keratotomy (RK)
  • 5) Intra Corneal Ring Segments (ICRS)

LENTICULAR SURGERY

It has been assumed that corneal surgery is safer than an intraocular procedure. That is cutting or reshaping of the cornea is less invasive than entering into the interior of the eye. The widespread use of Intraocular Lenses (IOLs) in cataract surgery has led to a high degree of confidence among ophthalmic surgeons that the lenses can be implanted in an otherwise healthy eye in a safe manner and with excellent predictability of the refractive outcome. The excellent outcomes and low risk-to-benefit ratio of modern cataract/IOL surgery has provided the impetus for increasing use of lensectomy/IOL implantation as an effective treatment for very high levels of myopia and for hyperopia especially in older patients. . The concept of intraocular lens implantation without lensectomy ( Phakic IOLs) is not new. Some designs date back to the 1950s but more modern phakic intraocular lenses have been placed in the anterior chamber (Baikoff style, Momose styles) and at the iris-plane (Worst-Fechner iris "claw") with excellent visual results, but some complications. The Implantable Contact Lens is inserted behind the iris in front of the natural lens and may offer the predictability and efficacy of IOL technology, yet is less invasive since the crystalline lens is left intact

Some of the currently available techniques are -

  • 1) Cataract Removal and IOL insertion
  • 2) Refractive Lens Exchange -removal of the clear lens and insertion of a correcting lens(IOL)
  • 3) Phakic Refractive Implants including the Visian Implantable Contact Lense

NOTE

Clear vision is not cheap - it has been estimated that over 20 years the cost of glasses will exceed $4,000 and of contact lens may cost more than $15,000.
To reduce visual aberrations especially at night (for an assumed pupil size of 5mm) the area of cornea reshaped needs to be 7.5 mm diameter while at the iris plane it needs to be only 4.8 mm diameter.
BCVA (best corrected visual acuity) is the best vision that can be achieved with correction and a loss of BCVA indicates that there is some loss of the best vision obtainable with correction while an increase in BCVA indicates that the corrected vision has been improved
6/6 is perfect vision indicating that spectacles will be only required occasionally
6/12 vision passes a driving test indication that many activities may be possible without spectacles.
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