Journal of Refractive Surgery

The articles prior to January 2013 are part of the back file collection and are not available with a current paid subscription. To access the article, you may purchase it or purchase the complete back file collection here

Further Studies of Four Incision Radial Keratotomy

Alan V Spigelman, MD; Patricia A Williams, COT; Richard L Lindstrom, MD

Abstract

ABSTRACT: This investigation evaluated the results of radial keratotomy on 52 eyes in 30 patients; 32 eyes had follow-up of greater than one year. The spherical equivalent refraction for 91% of these patients was within 1 diopter of emmetropia. We have followed five eyes between one and two to three years after surgery, observing a continued effect of the surgery with a mean gain in the hyperopic direction o1 +0.72 diopters. Initial overcorrections must be avoided in radial keratotomy. [Refractive and Corneal Surgery. 1989; 5:292-295].

Abstract

ABSTRACT: This investigation evaluated the results of radial keratotomy on 52 eyes in 30 patients; 32 eyes had follow-up of greater than one year. The spherical equivalent refraction for 91% of these patients was within 1 diopter of emmetropia. We have followed five eyes between one and two to three years after surgery, observing a continued effect of the surgery with a mean gain in the hyperopic direction o1 +0.72 diopters. Initial overcorrections must be avoided in radial keratotomy. [Refractive and Corneal Surgery. 1989; 5:292-295].

Radial keratotomy has undergone close scrutiny and constant evolution over the last 10 years in the United States. One of the main modifications has been to decrease the number of incisions. Cadaver eye studies have demonstrated that 70% of the central corneal flattening achieved with eight incisions could be achieved by the first four incisions.1·2 Other authors have reported clinical results of four incision radial keratotomy.3

We present a retrospective study of eyes that had four incision radial keratotomy at the University of Minnesota over the past 3 years. This investigation is a continued study of patients presented in a prior article.4

MATERIALS AND METHODS

We studied 52 eyes of 30 patients that received a four incision radial keratotomy. No eye had prior surgery and all eyes had at least 1 month of follow-up.

Each patient underwent a thorough eye examination including measurement of best corrected Snellen visual acuity, applanation intraocular pressure, central keratometry, ultrasonic pachometry, slit-lamp biomicroscopy, and fundus examination. The ultrasonic pachometer (Kremer Corneometer I) was set to a speed of sound in the cornea of 1640 meters per second. After an explanation of the surgery and its possible complications, the patient signed an informed consent form. The preoperative examination and technique of the operative procedure were carried out as described in the PERK study.5

The amount of surgery was determined on the basis of two nomograms. Table 1 illustrates the effect of the number of incisions and optical zone diameter on the change in refraction that can be expected. This is based on cadaver eye studies. Table 2 shows the effect of the blade length. Because age affects the final outcome, we adjusted our surgical expectations by 0.1 diopter (D)per year of greater effect for those patients over age 30 and 0.1 D per year of less effect for those patients under age 30.

The patients were prepped and draped in a sterile fashion in the minor operating room. Proparacaine 0.5% was applied topically to the eye three times prior to surgery. The optical axis was marked by first having the patient fixate on the filament of the microscope. An epithelial mark was then made at the left inferior aspect of the filament reflection while sighting with the right eye.6 Ultrasonic pachometry was then carried out centrally and at the 3, 6, 9, and 12 o'clock positions around the optical zone mark. The calculation for blade depth was then made and the KOI diamond knife set. A coin-shaped gauge block was used to verify blade length. The keratotomy incisions were carried out as described in the PERK protocol from the edge of the optical zone to the limbus.5 At the conclusion of the procedure, the incisions were irrigated. The patients were begun on topical antibiotics. Topical steroids were begun on the first postoperative day if the patient was undercorrected and utilized for a total of 3 months.

Seven eyes were significantly undercorrected following the initial four incision radial keratotomy. Four eyes had an additional four incisions. Two eyes had an additional two incisions and one eye had deepening of the original four incisions. All patients who had reoperations were eliminated from contributing data at any later point to this study. Therefore, all data discussed and tabulated refer to eyes that have had a single four incision radial keratotomy operation.

Table

TABLE 1Nomogram for Effect of Four Incision Radial KeratotomyTABLE 2Approximate Reduction of Myopia Obtained With Eight Incisions and 3.0 mm Diameter Optical Zone in a 30-Year-Old Patient*

TABLE 1

Nomogram for Effect of Four Incision Radial Keratotomy

TABLE 2

Approximate Reduction of Myopia Obtained With Eight Incisions and 3.0 mm Diameter Optical Zone in a 30-Year-Old Patient*

RESULTS

Preoperatively the spherical equivalent manifest refractions ranged from -1.50 to -4.75 D with one eye having -8.37 D (age 61) (Table 3). The uncorrected visual acuity varied from 20/100 to count fingers preoperatively (Table 4). All manifest refractions were carried out by the same investigator (PAW).

Table

TABLE 3Preoperative Spherical Equivalent RefractionTABLE 4Preoperative Uncorrected Visual Acuity

TABLE 3

Preoperative Spherical Equivalent Refraction

TABLE 4

Preoperative Uncorrected Visual Acuity

One month following surgery 90% of the eyes were within 1 D of emmetropia and 94% had 20/40 or better uncorrected visual acuity. Four eyes were overcorrected by greater than 1 D. Three months after surgery, 82% of the eyes were within 1 D of emmetropia and 85% had 20/40 or better uncorrected visual acuity. Only one eye at this time was overcorrected by greater than 1 D. At the 6 month follow-up visit, 92% of the eyes were within 1 D of emmetropia, 88% had 20/40 or better uncorrected visual acuity, and none were overcorrected. At the last patient visit, which ranged from 1 to 3 years following surgery, 91% of the eyes were within 1 D of emmetropia, 88% had 20/40 or better uncorrected vision, and two were overcorrected by greater than 1 diopter (Tables 5 & 6).

Patients were requested to return for follow-up examinations at 1, 3, 6, 9, 12, 24 and 36 months following surgery. Not all of our patients returned at scheduled intervals for examinations because they lived outside of Minneapolis. These patients were seen by their local ophthalmologist. No data have been utilized in this article that were not collected at the University of Minnesota because we wanted the same investigator to do all of the examinations.

Table

TABLE 5Refraction Following Four Incision Radial Keratotomy in 52 EyesTABLE 6Uncorrected Visual Acuity Following Four Incision Radial Keratotomy in 52 Eyes

TABLE 5

Refraction Following Four Incision Radial Keratotomy in 52 Eyes

TABLE 6

Uncorrected Visual Acuity Following Four Incision Radial Keratotomy in 52 Eyes

Five eyes had follow-up of 2 to 3 years. These eyes have had a change in their refractions in a hyperopic direction. On the average, these eyes have changed by +0.72 D as compared to their refractions at the 1 year visit (Table 7).

Complications included three microperforations, seven patients with subjective glare initially after surgery that disappeared within 6 to 12 months, eight eyes with induced cylinder of 0.50 to 1.00 D, nine patients with fluctuating vision which seemed to resolve with time, and four eyes with loss of best corrected visual acuity from 20/15 to 20/20. Eight eyes went from best corrected visual acuities of 20/20 to 20/15. No eyes lost two or more Snellen lines of best corrected visual acuity. No patients had epithelial erosions. Seven eyes had sufficient residual myopia to need reoperation.

The eye that was -8.37 preoperatively at age 61 was -6.25 D at 3 months. An additional four incisions were carried out. The resultant spherical equivalent refraction at 1 year was +1.00 D.

DISCUSSION

Cadaver eye models have demonstrated that four incisions may be sufficient to correct mild to moderate myopia.1·2 Many advantages can be ascribed to using four incisions including less surgery, fewer scars, and the ability to stage the surgery. Theoretically, decreasing the number of incisions will decrease the risk of perforation and therefore infection.7 The decreased number of incisions may also reduce endothelial cell loss,8 though this evidence remains tenuous.

Our data show that four incisions will correct a very high percentage of patients with myopia between -1.50 and -5.00 D and achieve 20/40 or better uncorrected visual acuity in the majority. Of these patients, the vast majority will see 20/25 or better uncorrected. We also had no overcorrections at 3 months follow-up greater than +1.00 D.

Table

TABLE 7Change of Refraction in Hyperopic Direction in Five Eyes After OU Incision Radial Keratotomy

TABLE 7

Change of Refraction in Hyperopic Direction in Five Eyes After OU Incision Radial Keratotomy

It is now apparent that patients may continue to have a change in the hyperopic direction 2 years following radial keratotomy. This phenomenon has been described by Dietz,9·10 Arrowsmith,u and Sawelson.12 Waring has also observed this in the PERK study and devoted an editorial to this "surprise."13 We too have noted this trend of a change in the hyperopic direction. We have only five eyes with 2 to 3 year follow-up, but they have on average gained 0.72 D of effect in the hyperopic direction. This continued effect of surgery is certainly disturbing. To date, no author has documented the cause for this phenomenon. We believe that cutting deeper will predispose to this late complication. Our reasoning is that as more corneal stromal lamellae are disrupted, more fibroblastic response is possible thus initiating more change in the corneal architecture. This remains pure speculation. This phenomena will have to be monitored carefully in the years to come.

Reoperations were carried out in seven eyes. The amount of surgery chosen for reoperation was empiric and based on the residual myopia. A small effect from the prior operation or a high amount of residual myopia dictated a redeepening procedure with possible extension of the incision to an optical zone of 2.5 mm. The ability to reoperate does point out the flexibility of the initial four incision operation. Also, in light the finding of progressive refractive change, overcorrections should be avoided.

This retrospective study has shown that four incision radial keratotomy can be effective and without vision-threatening complications in the low and moderate myopia groups. Careful counseling of patients as to possible complications and side effects are mandatory. Four incision radial keratotomy allows the surgeon flexibility as to "staging" the operation. Initial overcorrections were not encountered over 1 D; this may be important because some eyes will demonstrate a continued effect of the surgery over years. Continued follow-up of these patients will be done to ensure that radial keratotomy can be made as successful as possible.

REFERENCES

1. Lavery GW, Lindstrom RL. Trapezoidal astigmatic keratotomy in human cadaver eyes. Journal of Refractive Surgery. 1985;1:18-24.

2. SaIz JJ, Lee JS, Jester JV, Steel D, Villasenor RA, Nesburn AB, et al. Radial keratotomy in fresh human cadaver eyes. Ophthalmology. 1981; 88:742-746.

3. SaIz JJ, Villasenor RA, Elander R, Reader AL, Soinger C, Buch-Zinder M. Four incision radial keratotomy for low to moderate myopia. Ophthalmology. 1986; 93:727-738.

4. Spigelman AV, Williams PA, Nichols BD, Lindstrom RL. Four incision radial keratotomy. J Cataract Refract Surg. 1988; 14:125-128.

5. Waring GO III, Lynn MJ, Gelender H, Laibson PR, Lindstrom RL, Myers WD, et al. Results of the prospective evaluation of radial keratotomy (PERK) study one year after surgery. QpAthalmology. 1985; 92:177-196.

6. Steinberg EG, Waring GO III. Comparison of two methods of marking the visual axis on the cornea during radial keratotomy. Am J Ophthalmol. 1983; 96:605-608.

7. Wilhelmus KR, Hamburg S. Bacterial keratitis following radial keratotomy. Cornea. 1983; 2:143-146.

8. Dunn SA. Smith RE, Jester JV, et al. Non-progressive endothelial cell loss following radial keratotomy in primate eyes. Invest Ophthalmol Vis Sci. 1984; 25(suppl):168.

9. Deitz MR, Sanders DR. Progressive hyperopia with long-term follow-up of radial keratotomy. ArcA Ophthalmol. 1985; 103:782-784.

10. Deitz MR, Sanders DR, Raanan MG. Progressive hyperopia in radial keratotomy. Long-term follow-up of diamond knife and metal blade series. Ophthalmology. 1986; 93:1284-1289.

11. Arrowsmith PN, Marks RG. Four-year update on predictability of radial keratotomy. Journal of Refractive Surgery. 1988; 4:37-45.

12. Sawelson H, Marks RG. Five-year results of radial keratotomy. Refractive and Corneal Surgery. 1989; 5:8-20.

13. Waring GO III. Another surprise from radial keratotomy. Refractive and Corneal Surgery. 1989; 5:18-19.

TABLE 1

Nomogram for Effect of Four Incision Radial Keratotomy

TABLE 2

Approximate Reduction of Myopia Obtained With Eight Incisions and 3.0 mm Diameter Optical Zone in a 30-Year-Old Patient*

TABLE 3

Preoperative Spherical Equivalent Refraction

TABLE 4

Preoperative Uncorrected Visual Acuity

TABLE 5

Refraction Following Four Incision Radial Keratotomy in 52 Eyes

TABLE 6

Uncorrected Visual Acuity Following Four Incision Radial Keratotomy in 52 Eyes

TABLE 7

Change of Refraction in Hyperopic Direction in Five Eyes After OU Incision Radial Keratotomy

10.3928/1081-597X-19890901-05

Sign up to receive

Journal E-contents