What is RK? Problems with RK PERK Study and discontinuation of RK Challenges in Treatment Surgical Options
Radial Keratototmy in a nutshell
Indication: To treat mild to moderate myopia or nearsightedness.
Variations: 1. HK or hexagonal keratotomy to treat hyperopia.
2. Ak or Astigmatic Keratotomy to cure astigmatism.
Procedure: 1. Use nomogram to determine the number and length of incisions.
2. Measure the corneal thickness at each location on the cornea.
3. Incise upto 90 % of depth of the thickness of cornea with a diamond blade.
Mechanism of action: The weakened site of the incision bulges forward. This bulging implies the cornea at that point of cut became more steep. That correspondingly flattens the central cornea. The explanation for this is as follows. Pressure is equal to force divided by the surface area. The force generated by the intraocular fluid remains the same, whereas after RK the surface area increases due to focal bulging. Therefore the force on the central cornea decreases leading to flattening, a decrease in corneal power and hence a reduction in nearsightedness.
Complications: 1. Perforation of the cornea.
2. Epithelium in growth into incisions
Introduced by: Professor Fyederov in Russia
You may be suffering from the following:
- Diurnal fluctuation
- Annual fluctuation
- Glare
- Haloes
- Fatigue
- Return to glasses
- Fluctuation in vision
- Astigmatism
- Decreased contrast senstivty
- Dry eyes
- Inability to see good inspite of glasses
- Intolerance to contact lenses
The PERK Study
The U.S. National Eye Institute did a ten-year study called the Prospective Evaluation of Radial Keratotomy (PERK) to evaluate the short-term and long-term effectiveness of the RK techniques. Researchers concluded that although RK did improve myopia, its effectiveness varied from patient to patient.
It also demonstrated that there was an annual drift towards corneal flattening, which caused the eye to become gradually more farsighted. The results of this study showed that a post-RK eye was permanently unstable, and this led to RK falling out of favor in the U.S.
Why RK Was Discontinued in the U.S.
Fluctuating vision as demonstrated by PERK study and the advent of precise excimer lasers sounded the deathshell of RK in the US.
Challenges in Operating on Post-RK Eyes
- There are too many incisions.
- Hesitation cuts.
- The incisions are in the pupillary zone.
- The central cornea is very flat
- There is astigmatism or irregular astigmatism
- The peripheral curvature is different
- The optical zone is small (the central area important in vision)
- Fluctuation between morning and evening require testing at different times of the day.
- Further annual hyperopic drift has to be taken into account.
- Ophthalmic diagnostic instruments may not be able to display accurate readings of the cornea
- IOL or Intraocular Lens, power calculations may also require modifications because of each post-RK cornea being different
Your vision has deteriorated so much that you need glasses for reading and/or distance or not seeing good with either or developing cataracts. The wonderful surgeon who improved your vision with RK is now retired.So what do you do now? Don’t worry. Dr. Khanna has helped many patients improve their sight after Radial Keratotomy (RK).
Restorative Surgical Methods after RK
Fixing fluctuations:
- Suturing.
- Lasso technique.
- FDA approved corneal cross linking.
Improve vision:
Despite the challenges listed above, there are various techniques that can be used to improve vision after Radial Keratotomy. An experienced corneal surgeon like Dr. Khanna can analyze the exact problem and devise a tailor-made treatment plan. Since Dr. Khanna is trained and certified in multiple technologies, he can combine them to improve your unique vision.
Improving distance vision after Radial Keratotomy (RK) with Lasers
Dr. Khanna can use idesign laser vision correction for Improving Vision After Radial Keratotomy (RK). It can be used to enlarge the optic zone and fix astigmatism and myopia or hyperopia. idesign laser can be employed as a stand alone procedure if you are in your forties. idesign superlasik can be also used after PIE (presbyopia implant in eye) procedure has been performed.
Lasik is nowdays avoided after RK surgery. The flap may cause the cornea to split in pizza like segments.
PIE to help Improve All Vision including presbyopia after Radial Keratotomy (RK)
Rajesh Khanna, M.D., is also skilled in PIE procedure (formerly called Refractive Lens Exchange surgery). This involves opening the natural lens and to vacuum out its contents. A bio inert acrylic lens like symfony or silicon lens like Crystalens or Trulign is than placed in this natural space. If you want to see far and near in each eye, than PIE procedure may be the better option.
Cataract surgery after Radial Keratotomy
If you have cataracts, special calculations and highly skilled surgery would be required. Accurate measurements of the length of the eye are made using the latest generation of optical biometers like IOL master 700 or Lenstar. Corneal curvature needs to be verified on various devices like Atlas 900 topography, keratometry units. These have to be placed in special formulas to generate the power of the artificial implant to nbe inserted. In special situations the power may need to be recalculated on the operating table using ORange.
At the time of surgery special precautions have to be taken while making incisions to enter the eye. They have to be placed carefully between the preexisting RK cuts. Care has to be taken not to intersect the new openings with previous cuts lest the old wounds open up. If they do they can be sutured. If no gaps can be found such as in 32 cut RK, than Dr. Khanna has resorted to making scleral wounds to enter the eye.
Only certain kinds of IOLs can be implanted in post RK eyes.
