|Year : 1990 | Volume
| Issue : 3 | Page : 132-138
Complications of radial keratotomy : Review of the literature and implications for a developing country
Peter S Hersh1, Kennath R Kenyon2
1 Massachusetts Eye & Ear Infirmary Instruction in Ophthalmology, Harvard Medical School.
2 Massachusetts Eye & Ear Infirmary, Associate Professor of Ophthalmology Harvard Medical School, Senior Scientist, Eye Research Institute of the Retina Foundation.
Peter S Hersh
Massachusetts Eye & Ear Infirmary Instruction in Ophthalmology, Harvard Medical School.
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Hersh PS, Kenyon KR. Complications of radial keratotomy : Review of the literature and implications for a developing country. Indian J Ophthalmol 1990;38:132-8
|How to cite this URL:|
Hersh PS, Kenyon KR. Complications of radial keratotomy : Review of the literature and implications for a developing country. Indian J Ophthalmol [serial online] 1990 [cited 2020 Jun 1];38:132-8. Available from: http://www.ijo.in/text.asp?1990/38/3/132/24522
| Introduction|| |
Upon its introduction in the United States in the late 1970's, radial keratotomy was rapidly to become the world's most commonly performed refractive surgical procedure. Several large American studies have found radial keratotomy, when performed with compulsive attention to surgical detail and postoperative followup, to be a relatively safe procedure.1-12 Verification of a high degree of safety Is of particular Importance in such an invasive surgical procedure since these myopic eyes are otherwise usually normal and have good visual acuity with spectacle or contact lens correction.
In theory, a dependably safe and effective refractive surgical procedure would be of particular advantage in a developing country. In such locales, adequate contact lens fitting, followup, and lens hygiene may be difficult. Moreover frequent loss of spectacles, difficult access to vision care centers, and the cost of optical correction might prevent many people from enjoying good vision on a continuous basis.
Wherever performed, a successful radial keratotomy procedure relies on appropriate case selection, meticulous operative technique, costly and sophisticated equipment (such as diamond knives and ultrasonic pachymeters), and careful) followup. With an increased experience in radial keratotomy, moreover, a number of complications, ranging from mild and transient to severe and sightthreatening have been reported. Such complications have trauma and infection in a rural setting. Furthermore, limited availability of postoperative followup care may render such procedures more hazardous since early complications may not be promptly brought to the surgeon's attention, thereby leading to more severe consequences.
The following review will discuss the many complications of radial keratotomy which have been reported in the literature and their significance within the ophthalmologic settings of developing countries.
| Review of the literature|| |
The complications of radial keratotomy complications may be subsumed under two general categories-those arising from an adverse optical outcome and others secondary to pathological ocular changes.
The immediate and longterm refractive efficacy of radial keratotom has been a subject of a number of large studies. ,,,,,,, At three year followup, the PERK study found 58% of eyes to be within one diopter of emmetropia with 76% of eyes achieving an uncorrected visual acuity of 20/40 or better. This is similar to other studies which show from 50 to 76% of eyes with 20/40 or better postoperative uncorrected vision. ,,,, The PERK study found a similar incidence of overcorrection in all preoperative refractive groups, while higher myopes had a greater likelihood of undercorrection.  Undercorrection may result from the selection of too large an optical zone, too few incisions, or shallow incision depth.
Overcorrections may be transient, secondary to corneal edema and poor wound healing, or permanent, resulting from too small an optical zone, too many incisions, chronic stromal edema, or poor wound healing. Whether under or overcorrected, those patients who are corrected as well as 20/40 or better vary in their satisfaction with the procedure. 
The success rate of radial keratotomy, furthermore varies with the amount of preoperative myopia. Lower myopes, in general, tend to achieve a result closer to emmetropia. Of the many factors possibly influencing surgical outcome, size of the optical zone, patient age, and incision depth are most highly correlated with postoperative refractive change. 
Visual acuity and refractive error after radial keratotomy, moreover, have been shown to exhibit both diurnal and long; term variation. ,,,,, Varying vision over the course of the day is a common subjective complaint of radial keratotomy patients and is an important determinant in patient dissatisfaction. One year postoperatively, 44% of patients in the PERK study varied their j refractive error by 0.50 diopters or more from morning to evening.  Such visual fluctuation may be attributed, to the slow pace of corneal wound healing with conee-' quent instability of the patient's refraction as well as increased corneal edema after sleep with progressive dehydration and corneal steepening as the day progresses. Rapid changes in refractive error have even been shown to occur with variations in intraocular pressure. 
Over the long term, a progressive hyperopic shift has been found in one study.  Approximately 10% of patients, however, show a regression of the radial keratotomy effect. 
In addition to spherical refractive errors, radial keratotomy can induce both regular and irregular astigmatism. ,, The PERK study found 10% of eyes to manifest an increase in astigmatism of greater than 1 diopter postoperatively.  Whether spherical or astigmatic, all such induced refractive errors, especially in those patients receiving unilateral radial keratotomy surgery, may result in troublesome anisometropia postoperatively.
A number of other optically-related complications of radial keratotomy have been described. These include glare as a result of corneal scarring and irregularity, diminished night vision, and loss of contrast sensitivity., ,, The PERK study found that 17% of patients complained of relatively severe postoperative glare. [15 ] Many of these patients, however, had similar glare complaints preoperatively and this did not seem to severely diminish the overall satisfaction with the procedure in the majority of patients. Monocular and binocular diplopia and asthenopic symptoms secondary to scarring, irregular astigmatism, anisometropia and aniseikonia are less frequent patient complaints.
Non-optical complications vary in severity from clinically insignificant corneal changes to severe sight threatening sequelae. Such complications may occur at the time of surgery, in the immediate postoperative period, or as late sequelae.
Operative technique is clearly of paramount importance in successful, reproducible results in radial keratotomy. Impingement of corneal scars upon the optical zone occurred in over 10% of eyes in one study [Figure - 4].  Misplacement of incisions is another obvious but frequent consequences of poor operative technique resulting in glare and diminished visual acuity [Figure - 2]. Intraoperative microperforations have been found to occur in from approximately 2% to 35% of patients. , Incidence of perforation has decreased with the development of improved operative techniques including intraoperative ultrasonic pachymetry, the use of a diamond rather than metal knife, and refined surgical technique. Most micro perforations are self sealing. Occasionally, however, the anterior chamber will be lost, necessitating placement of a corneal suture and the termination of the procedure before completion [Figure - 3]. Although usually inconsequential, in rare cases, a number of severe consequences may result from such perforations. Loss of the anterior chamber may predispose to synechia formation. Presumed epithelial ingrowth has teen reported [Figure - 4].  Endothelial cell loss averaging 1.6-14.3% is found both in eyes without intraoperative perforation as well as in eyes which have suffered perforation. , Higher cell loses, however, are found in those eyes in which a perforation had occurred. Rarely, clinically significant corneal edema may arise after radial keratotomy.
Postoperatively, patients frequently complain of transient pain and foreign body sensation. Frequently, there is mild inflammation of the anterior segment. Postoperative ocular surface changes include stellate iron lines secondary to surface irregularity,  map-dot-fingerprintlike changes of the epithelial basement membrane,  recurrent erosions, and the formation of epithelial cysts. Such complications vary in clinical significance and are more prevalent with poor operative technique, the use of dull metal blades, redeepening procedures, and in patients with a compromised ocular surface preoperatively. Treatment may variously include lubrication, patching, and the use of bandage soft contact lenses. Postoperatively, the incisions may excessively scar and may vascularize, especially when contact lenses are used or when the limbus has been violated.  Even complications such as cataract formation has been reported following radial keratoto5 y, especially after microperforation [Figure - 5].  Steroid use may be implicated in cataract formation in some cases.
Many cases of microbial keratitis following radial keratotomy have been reported and may necessitate penetrating keratoplasty [Figure - 6].  These often occur in the incision  and are associated with complicating factors such as atopic dermatitis,  contact lens wear  and persistent epithelial defects. [26 ] Sterile corneal ulceration has also been reported in association with postoperative persistent epithelial defects.  Many of these eyes lose vision and require further surgical procedures such as penetrating keratoplasty. Bacterial endophthalmitis is a devastating consequence of-infection secondary to perforations during radial keratotomy. , Laboratory investigation, furthermore, has suggested that radial keratotomy may even precipitate recurrent herpes simplex epithelial lesions.
The slow rate and limited efficacy of wound healing in a radial corneal incision may make the cornea may be more susceptible to traumatic rupture, particularly if a miroperforation has occurred. 
Probably the most important overall statistic regarding the safety of radial keratotomy are those patients who suffer a decrease in their best corrected visual acuity postoperatively. At one year after surgery, the PERK study found 0.7% of eyes which could not be corrected to baseline visual acuity.  At three years, 1.4% of eyes had lost 2-3 lines of best corrected acuity.  In the PERK study of repeated radial keratotomy,33% of patients lost one line of corrected visual acuity.
In addition to these procedure-specific complications of radial keratotomy, general complications of ophthalmic surgery may occur.  These include optic atrophy secondary to retrobulbar anesthesia and retinal detachment secondary to adjunctive phospholine iodide therapy.  Corticosteroid-induced glaucoma has also been described.  Postoperative glaucoma may also arise secondary to peripheral anterior synechiae resulting from intraocular inflammation or loss of the anterior chamber secondary to a perforation. Ironically, radial keratotomy, a cosmetic procedure in many cases, may rarely be complicated by ptosis. 34
| Discussion and recommendations|| |
The foregoing review describes the results obtained and complications encountered when radial keratotomy is performed in the circumstances widely available in developed countries. Thus, with careful and appropriate case selection, adequate training and experience of the surgeon, appropriate instrumentation, and responsible follow-up, it can be stated that radial keratotomy is indeed a relatively safe and reasonably effective procedure for reducing myopia. What, however, are the consequences of performing this surgical procedure under less optimal circumstances, as might pertain in a developing country? The answer in intuitively the obvious: Major vision threatening complications and even irreversible blindness.
For India, in particular, Dr. Kalevar has reported at the 1986 AIOS Meeting, three radial keratotomy patients with severe stromal scarring or ulceration, flat anterior chambers, iridocorneal adhesions, glaucoma, and cataract. Each required complex surgical interventions including penetrating keratoplasty and anterior segment reconstruction with visual acuity decreased to light perception in four of five eyes. We have personally examined one of these patients, a nine-year-old girl who underwent bilateral simultaneous radial keratotomy resulting in light perception vision in both eyes due to corneal perforation and ulceration, stromal scarring, and cataract necessitating penetrating keratoplasty. This surgery had been allegedly performed utilizing an ordinary metal scalpel blade and without the use of an operating microscope. More recently, at the 1988 AIOS Meeting, Dr. K. Mehta described 23 cases of cataract occurring after radial keratotomy, presumably the result of perforation and/or steroid treatment. These cases alone suffice to underscore the potentially disastrous consequences of radial keratotomy performed on inappropriate cases, with poor technique and instrumentation, and suboptimal postoperative management.
Apart from these grim consequences, it is not the intention of the authors to imply that radial keratotomy should not be performed in developing countries. Rather, we wish to set down positive recommendations in an appropriate precautionary context as follows:
1. Surgical: Only fully qualified ophthalmic surgeons trained in microsurgical technique in general and having specifically been instructed in radial keratotomy should be allowed to perform radial keratotomy. Such training may be acquired through an instruction course, preferably with hands-on laboratory experience, or by observation of experienced keratorefractive surgeons skilled in the nuances of the procedure.
2. Appropriate Instrumentation : Radial keratotomy should be performed in a setting appropriated for intraocular surgery including sterile conditions, anesthetic capability, and adjunctive instrumentation as would be appropriate for all other major intraocular surgery. Specifically, the operating microscope should always be utilized, ultrasonic pachymetry is preferred (although careful and accurate optical pachymetry may suffice), and precision blades, preferably of gem material (diamond or sapphire) with guards to limit incision depth, are mandatory. Other specialized instrumentation includes a coin type blade guage and devices to fixate the globe when performing incisions.
3. Patient Selection: The occupational and living environment of potential radial keratotomy patients needs to be addressed. Many patients still require correction, whether spectacle or contact lens after surgery. Furthermore, since radial keratotomy incisions likely remain inherently weak, patients susceptible to trauma, such as labourers and agricultural workers, are theoretically poor surgical candidates. Moreover, locales with a high incidence of microbial keratitis may be adverse settings for a procedure which, by its nature, compromises corneal surface integrity
Raidal keratotomy should only be performed on adult patients with stable myopia of a moderate degree, usually less than six or eight diopters. Radial keratotomy, therefore, is specifically contraindicated in children, patients with progressive pathologic or extremely high myopia (greater than eight diopters), and in patients with significant corneal disease, specifically keratoconus. Both patients and ophthalmologists should recognize that radial keratotomy will not prevent the progression of myopia, thus, providing an additional contraindication to its application in children.
4. Operative Technique: In addition to the considerations of appropriate instrumentation and operative setting described above, it is recommended that bilateral simultaneous surgery be avoided, and that a postoperative recovery of several weeks or months elapse to allow for a stable anatomical and visual result in the first operated eye prior to consideration of additional refractive surgery in the other eye. Intraoperative complication 'must be appropriately managed, and in particular, the not uncommon occurrence of perforation with loss of the anterior chamber must be adequately sutured if the chamber does not reform spontaneously.
5. Follow-up and Postoperative Complications: Close and responsible postoperative follow-up, especially during the initial days to weeks when infectious complications may occur, is mandatory, as is the utilization of prophylactic topical antibiotics beginning at the time of surgery. The obvious potential of steroid-related complications, ranging from the potentiation of microbial infection to the well-known long-term sequelae of cataract and glaucoma, mandate their avoidance except in settings where patient reliability and access to close follow-up care are assured.
Finally, the facilities and expertise to deal with complications are essential concomitants of an adequate radial program. The nature of radial keratotomy makes reparative corneal surgical procedures such as penetrating keratoplasty especially difficult. Poor healing and intraoperative splitting of the radial incisions makes suturing of a donor button more difficult as well as compromising wound closure. Many of the more severe complications of radial keratotomy likely result from perforation during the initial procedure, resulting in a flat anterior chamber. Such wound leakage and anterior chamber shallowing encourages formation of synechia, increase in intraocular inflammation, and the possibility of infection, making corrective reconstructive surgery difficult. Vascularization of the incisions, moreover, increases the risk of subsequent transplant rejection.
In conclusion, throughout much of the western world, radial keratotomy is becoming an accepted procedure for the reduction of myopia with reasonable safety and efficacy when performed under optimal circumstances on appropriate patients. In this setting, the complications, while potentially dangerous, are fortunately few. To attain these same results in developing countries, we recommend strict adherence to the rather straight-forward recommendations specified above. We believe that the standards for performing ophthalmic surgery are universal and, although requiring adaptation to local circumstances in developing countries, they should not be compromised with respect to patient safety. Finally, from our particular perspective as corneal surgeons, the iatrogenic corneal complications resulting from elective surgical procedures incur unacceptable costs and morbidities even in developed countries where such costs are affordable and keratoplasty usually successful. In a developing country, moreover, where limitations of the economy, of access to health care, and of successful keratoplasty make corneal blindness irreversible, iatrogenic corneal blindness is especially devastating and unconscionable.
Although a relatively safe and simple procedure, the surgeon must be aware of the possible complications inherent in radial keratotomy. The ability to avoid, recognize, and treat these complications is necessary to care adequately for the refractive surgical patient. The economic costs involved, facilities available, patient lifestyle, access to followup care, and surgical training
should all be factored into the decision to perform radial keratotomy. As physicians our most important guiding principle in performing radial keratotomy should remain our Hippocratic Oath: Primum Nihil Nocere-- Above all, to do no harm.
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[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6]