Topical mitomycin-C for subepithelial fibrosis after refractive corneal surgery

OBJECTIVE

To determine the effectiveness of mitomycin-C (MMC), 0.02%, in preventing recurrence of corneal subepithelial fibrosis after debridement and/or keratectomy in patients who have undergone refractive corneal surgery.

DESIGN

Noncomparative case series.

PARTICIPANTS

Eight eyes of five patients with corneal subepithelial fibrosis who had previously undergone radial keratotomy (n = 4) or photorefractive keratectomy (n = 4).

INTERVENTION

All eyes underwent epithelial debridement followed by a single intraoperative application of MMC (0.02%) for 2 minutes followed by saline irrigation. The eyes were then patched, or a bandage contact lens placed until epithelial healing was complete.

MAIN OUTCOME MEASURES

Corneal clarity and best-corrected visual acuity (BCVA).

RESULTS

In all cases, the cornea remained clear with no recurrence throughout the follow-up period (6-25 mos., mean, 13.8 mos). No adverse reactions were reported. BCVA improved in all cases.

CONCLUSIONS

Subepithelial fibrosis can be a visually disabling condition after refractive corneal surgery. Topical application of MMC (0.02%) may be a successful method of preventing recurrence of subepithelial fibrosis after debridement.

Evaluating and reporting astigmatism for individual and aggregate data

PURPOSE

To demonstrate the proper method for evaluating and reporting astigmatism for individual and aggregate data.

SETTING

University of Texas Medical School and Cullen Eye Institute, Baylor College of Medicine, Houston, Texas, USA.

METHODS

The surgically induced refractive change (SIRC) was determined for three data sets of patients who have had keratorefractive (photorefractive keratectomy) or cataract surgery. To make changes in refraction comparable, vertex distances for the refractions and keratometric index of refraction were considered. Doubledangle plots and single-angle plots were then used to display the data. Polar values (cylinder and axis) were converted to a Cartesian (x and y) coordinate system to determine the mean value of the induced astigmatism for each data set.

RESULTS

Doubled-angle plots clearly demonstrated the trends of induced astigmatism for each data set, and the mean value for induced astigmatism agreed exactly with the intuitive appearance of the plot.

CONCLUSIONS

Converting astigmatism data to a Cartesian coordinate system allowed the correct computation of descriptive statistics such as mean values, standard deviations, and correlation coefficients. Using doubled-angle plots to display the data provides the investigator with the best method of recognizing trends in the data.

Intraocular Lens Power Calculation in Eyes After Corneal Refractive Surgery

PURPOSE

The purpose of this review article is to discuss the major reasons for postoperative hyperopia after cataract surgery following radial keratotomy (RK) and photorefractive keratectomy (PRK) and to illustrate potential methods for improvement of intraocular lens (IOL) power prediction after keratorefractive surgery based on exemplary model calculations.

METHODS

We previously performed model calculations in eyes after PRK for myopia (-1.50 to -8.00 D, mean -5.40 +/- 1.90 D) using keratometry readings as measured by the Zeiss keratometer and the TMS-1 topography unit and as calculated using the "clinical history method" (spherical equivalent refraction change) and change in anterior surface keratometry readings.

RESULTS

We found that after PRK, mean measured keratometry readings were significantly greater than respective calculated values considering the preoperative to postoperative change of anterior corneal surface (P < .001), which itself was significantly greater than calculated keratometry readings considering the preoperative to postoperative change of spherical equivalent refraction (P < .001). IOL power underestimation correlated significantly with the difference between preoperative and postoperative spherical equivalent refraction (P = .001).

CONCLUSIONS

For correct assessment of keratometric readings to be entered into more than one modern third-generation IOL power calculation formula (but not a regression formula), the clinical history method should be applied whenever refraction and keratometric diopters before the keratorefractive procedure are available to the cataract surgeon. If preoperative keratometric diopters and refraction are not known, average central power on the postoperative videokeratograph may be used after RK, but refined calculation of keratometric diopters from radius of anterior and posterior corneal surface should be used after PRK and/or LASIK.

Refractive complications of cataract surgery after radial keratotomy

Four patients underwent cataract extraction with posterior chamber lens implantation several years after radial keratotomy. All four patients experienced an initial hyperopic shift caused by an early postoperative corneal flattening of greater than or equal to 1 diopter. This flattening partially regressed, leaving the patients with a mean of 0.42 diopter of persistent corneal flattening. We found the Binkhorst and the Holladay intraocular lens calculation formulas to be more accurate than the SRK II for these patients. Corneal curvature measured with the keratometer was less accurate for intraocular lens calculations than was a value derived by subtracting the refractive change induced by the radial keratotomy from the patients' keratometric measurements obtained before radial keratotomy.

Advances in the analysis of corneal topography

Recent advances in topographic analysis have provided powerful tools for detecting subtle, but clinically significant, alterations of corneal contour. This article compares keratometry, keratoscopy, and computer-assisted topographic analysis and provides specific examples of the sensitivity of computer-assisted systems in revealing topographic alterations that were not previously discernable. Quantitative descriptors of corneal topography such as the surface asymmetry index, the surface regularity index, and simulated keratometry value augment the information provided by color-coded topographic maps.

Complications of radial and transverse keratotomy

Radial keratotomy for myopia and transverse keratotomy for astigmatism are the most commonly performed refractive surgical procedures. A decade of experience with modern techniques has produced considerable literature on the complications of keratotomy. Vision-threatening complications (bacterial keratitis, traumatic rupture of the globe through weakened keratotomy scars, endophthalmitis, cataract formation from surgical trauma to the lens) are quite rare, occurring in less than 1% of eyes in published series. The most common side effects affect most patients in the first few months after surgery: pain for 24 to 48 hours, transient glare and light sensitivity, and fluctuating visual acuity. The most common persistent complications are overcorrection and undercorrection. Persistent irregular astigmatism occurs in almost all cases in the region of the incision scars, but it is rarely severe enough to reduce spectacle acuity. Most individuals have mild glare, but this is rarely disabling. Diurnal variation of refraction in visual acuity occurs commonly, but the magnitude of the fluctuation is seldom enough to require multiple pairs of spectacles. Longterm refractive stability occurs in approximately half of eyes by six months, but approximately one in four eyes will experience continued change over six months to four years. Complications, such as scarring from intersecting keratotomy incisions, irregular astigmatism resulting from multiple reoperations, and overcorrections with the attendant early onset of symptomatic presbyopia are becoming much less frequent.

Contrast sensitivity and glare disability after radial keratotomy and photorefractive keratectomy

OBJECTIVES

To study the effects of radial keratotomy (RK) and photorefractive keratectomy (PRK) on contrast sensitivity and glare disability using 4 different devices, and to correlate subjective complaints with obj ective scores of visual performance.

METHODS

Preoperative contrast sensitivity for 30 eyes undergoing RK and 30 eyes undergoing PRK was compared with contrast sensitivity at 1, 3, and 6 months postoperatively using the CSV 1000, MCT (Multivision Contrast Tester) 8000, and Pelli-Robson chart. The BAT (Brightness Acuity Tester) and MCT 8000 were used to test for daytime and nighttime glare disability, respectively. At 3 and 6 months postoperatively, a questionnaire was administered to assess visual performance subjectively.

RESULTS

Contrast sensitivity decreased after RK and PRK up to the sixth postoperative month, while glare disability was significantly increased at 1 month after PRK as determined by the MCT 8000 and the BAT, and at the third and sixth months after RK using the MCT 8000. Compared with RK, PRK significantly decreased contrast sensitivity as measured with the MCT 8000 at all spatial frequencies 1 month postoperatively. No significant difference in visual performance between patients undergoing RK and PRK was observed with the CSV 1000, the Pelli-Robson chart, or the BAT up to 6 months postoperatively. No consistent difference was found between glare disability scores of patients undergoing RK and PRK when measured with the MCT 8000. Subjective reports of problems with night driving and blurring correlated only with glare disability scores of the MCT 8000 3 months after RK.

CONCLUSIONS

Both RK and PRK reduce contrast sensitivity and cause glare disability; however, the relative effect is highly dependent on the time postoperative testing is performed and the instrument used for testing. Contrast sensitivity and glare disability, as measured by the instruments used in this study, do not accurately reflect patients' subjective assessment of visual performance in daily life.

Histopathology of traumatic corneal rupture after radial keratotomy

Two patients (three eyes) had previously undergone technically successful radial keratotomy procedures and subsequently sustained blunt injury to the eyes in motor vehicle accidents one and two years after surgery, respectively, with rupture of the cornea along the keratotomy scars. One case subsequently required penetrating keratoplasty to recover 20/50 visual acuity. The second patient died, but had he survived, the extensive ocular injuries would have required significant surgical and medical care to restore vision. Histologic and ultrastructural studies demonstrated incomplete wound healing in the three corneas. Individuals who have had radial keratotomy, like those who have had penetrating keratoplasty, are at increased risk of corneal rupture after direct ocular trauma.

Contact lens fitting to correct irregular astigmatism after corneal refractive surgery

PURPOSE

To study a technique of contact lens fitting and its visual results in patients with irregular astigmatism induced by corneal refractive surgery.

SETTING

Department of Cornea and Refractive Surgery, Instituto Oftalmológico de Alicante, Alicante, Spain.

METHODS

This prospective noncomparative study comprised 29 eyes with irregular astigmatism after corneal refractive surgery. Different types of contact lenses were used to correct the astigmatism: hard, gas permeable, hybrid, and toric hydrophilic. Preoperative and postoperative data were analyzed for proper fitting including the preoperative keratometeric reading and corneal ablation zone.

RESULTS

Proper contact lens fitting was achieved in 23 eyes (79.3%). In 6 eyes (20.7%), fitting was not possible despite an improvement in best corrected visual acuity (BCVA). Of the eyes with proper fitting, 14 (60.9%) had rigid gas-permeable lenses (9.80 mm), 6 (26.1%) had hydrophilic lenses (14.00 mm), and 3 (13.0%) had hybrid lenses (14.3 mm). Comparing the BCVA with that with spectacles, 23 eyes (79.3%) gained 2 lines or more of BCVA, 4 (13.8%) gained 1 line, and 2 (6.9%) maintained the same acuity as with spectacles. No eye lost lines of BCVA.

CONCLUSIONS

Results indicate that contact lens fitting is a good-and sometimes the only-alternative for patients with induced irregular astigmatism. Rigid gas-permeable contact lenses provided the best visual performance and patient tolerance.

Complications of hexagonal keratotomy

We examined 15 eyes of ten patients with complications of hexagonal keratotomy, which included glare, photophobia, polyopia, fluctuation in vision, overcorrection, irregular astigmatism, corneal edema, corneal perforation, bacterial keratitis, cataract, and endophthalmitis. Wound healing abnormalities and anterior displacement of the central cornea adjacent to the incisions were common. Eight eyes lost best-corrected visual acuity of two or more Snellen lines. Three eyes required penetrating keratoplasty for visual rehabilitation. Histologic analysis of two of these corneas disclosed variations in wound depth and abnormalities of wound configuration, including considerable wound gaping. Hexagonal keratotomy appears to be an unpredictable, unsafe surgical procedure with a high complication rate, and it should be abandoned until well-controlled experimental trials establish its safety and efficacy.

Visual, refractive, and keratometric results of radial keratotomy. Five-year follow-up

This article presents five-year findings on the first 156 radial keratotomies in our series. Results are compared with findings on these same eyes at one and three years and with results from other studies. Follow-up at five years was on 123 eyes (79%). Before surgery, the mean spherical equivalent was -5.0 diopters (D). Five years after surgery, the mean change in the spherical equivalent was 5.17 D, and 53% of eyes were within 1 D of emmetropia. Uncorrected visual acuity was 20/200 or worse in 96% of eyes before surgery. At five years, 36% had 20/20 acuity or better, and 75% were 20/40 or better. Best corrected acuity was at least 20/20 in 90% of eyes before surgery. At five years, 85% retained at least 20/20 best corrected acuity. Although some patients still have shown refractive and visual acuity changes through five years after surgery, the overall group has been stable.

Hyperopic laser-assisted in situ keratomileusis for radial keratotomy induced hyperopia

PURPOSE

To evaluate hyperopic laser in situ keratomileusis (H-LASIK) for radial keratotomy (RK)-induced hyperopia.

DESIGN

Noncomparative interventional retrospective nonconsecutive case series.

PARTICIPANTS

Sixty-nine eyes of 47 patients who had undergone RK and were seen with induced hyperopia.

METHODS

H-LASIK was performed with an excimer laser.

MAIN OUTCOME MEASURES

The mean refractive error, in spherical equivalents (SE), uncorrected visual acuity (UCVA), and best spectacle-corrected visual acuity (BSCVA) before and after H-LASIK are reported. Safety was analyzed using a mean follow-up time of 6.6 plus minus 3.24 months.

RESULTS

Preoperative mean SE was +3.4 plus minus 1.6 diopters (D). Postoperative mean SE was -0.32 plus minus 1.2 D. A high percentage of eyes (79.7%; n = 55) were between plus minus1.0 D of emmetropia and 88% within plus minus 2.0 D. Preoperative BSCVA was 20/20 in 53.6% of eyes (n = 37) and 20/40 or better in 100% (n = 69). Postoperative BSCVA was 20/20 in 55% of eyes (n = 38) and 20/40 or better in 95.6% (n = 66) of eyes. Preoperative UCVA was less-than-or-equal20/50 in 52 cases (75.4%). Postoperative UCVA was 20/20 in 13 cases (18.8%) and greater-than-or-equal20/40 in 45 cases (65.2%). Four eyes lost 2 Snellen lines because of epithelial ingrowth in the interface (n = 3) and diffuse lamellar keratitis (Sands of the Sahara syndrome; n = 2). One of the eyes with Sahara syndrome also had epithelial ingrowth and flap necrosis. Thirteen eyes lost 1 Snellen line, and 50 eyes maintained or gained Snellen lines. The only intraoperative complication was incision opening (n = 8) while the flap was lifted; there were no further complications. These patients did not lose any Snellen lines of their BSCVA.

CONCLUSIONS

H-LASIK can be used successfully to correct RK-induced hyperopia.

Photorefractive keratectomy to treat myopia and astigmatism after radial keratotomy and penetrating keratoplasty

Fifteen eyes with an initial myopia between -5.00 diopters (D) and -12.00 D were treated with radial keratotomy (RK) followed by photorefractive keratectomy (PRK) at least 6 months later and observed for 6 months to 24 months. Five eyes that had penetrating keratoplasty (PKP) were treated for residual ametropia by PRK and followed for up to two years. For the RK-treated eyes, mean pre-PRK refraction was -4.00 D sphere and + 1.25 D cylinder, which improved to -0.52 D sphere and + 0.73 D cylinder. Incidence of complications, including corneal haze, was extremely low in both the RK and PKP groups. In summary, PRK is a valuable method for correcting ametropia following RK and PKP, with risks similar to that for eyes having PRK as the initial refractive procedure.

A multicenter trial of photorefractive keratectomy for residual myopia after previous ocular surgery. Summit Therapeutic Refractive Study Group

PURPOSE

The Summit Therapeutic Refractive Clinical Trial is a nine-center prospective, nonrandomized, self-controlled trial to assess the efficacy, stability, and safety of using a standardized technique of excimer laser photorefractive keratectomy (PRK) to correct residual myopia in eyes with previous refractive surgery or cataract surgery.

PATIENTS AND METHODS

Eligible eyes with a mean residual myopia of -3.7 +/- 1.8 diopters (D) (range, -0.63 to -11.00 D) underwent PRK with a 193-nm excimer laser for myopic corrections between -1.50 and -7.50 D. Standardized settings were used for the ablation zone, ablation rate, repetition rate, and fluence. One hundred seven of the first 114 treated eyes were examined 1 year after PRK, with 98% of eyes having had refractive keratotomy and 2% having had cataract surgery.

RESULTS

One year postoperatively, the mean manifest spherical equivalent refraction was -0.6 +/- 1.4 D (range, -6.50 to 2.50 D); 63% of eyes were within +/-1.00 D of the attempted correction; and uncorrected visual acuity was 20/40 or better in 74% of eyes. Twenty-nine percent of eyes lost two or more Snellen lines of best-corrected visual acuity, and central corneal haze was moderate or severe in 8% of eyes.

CONCLUSIONS

Excimer laser PRK is effective in reducing residual myopia after previous refractive and cataract surgery. However, it is less accurate than PRK in eyes that did not undergo surgery and is more likely to cause a loss of best-corrected visual acuity 1 year after treatment.

Morning-to-evening change in refraction, corneal curvature, and visual acuity 11 years after radial keratotomy in the prospective evaluation of radial keratotomy study. The PERK Study Group

PURPOSE

Previous reports demonstrate morning-to-evening changes in ophthalmic measurements at 3 months, 1 year, and 4 years after radial keratotomy. The authors determine whether diurnal change in refractive error persists 11 years after radial keratotomy surgery in the Prospective Evaluation of Radial Keratotomy (PERK) study.

METHODS

Seventy-one patients were examined in the morning and evening a mean of 11.1 +/- 0.6 years (range, 10-12.7 years) after undergoing radial keratotomy under a standardized protocol using a diamond blade.

RESULTS

Between the morning and evening examinations, the mean change in the spherical equivalent of refraction was a 0.31 +/- 0.58-diopter (D) increase in minus power in first eyes. Thirty-six (51%) eyes had an increase in minus power of the manifest refraction of 0.50 to 1.62 D; 22 (31%) had a change in refractive cylinder power of 0.50 to 1.25 D; 9 (13%) had a decrease in uncorrected visual acuity of two to seven Snellen lines; and 25 (35%) showed central corneal steepening measured by keratometry of 0.50 to 1.94 D. Two (3%) eyes lost two lines of spectacle-corrected visual acuity, whereas one (1%) eye gained two lines. In patients whose both eyes underwent surgery, a high degree of symmetry was observed in morning-to-evening refractive change.

CONCLUSION

In some patients after radial keratotomy, morning-to-evening change of refraction and visual acuity persists for at least 11 years, although in most patients the magnitude of this change is small. Thus, diurnal fluctuation may be a permanent sequela of radial keratotomy in some individuals.

Visual, refractive, and keratometric results of radial keratotomy. A two-year follow-up

We report two-year follow-up findings on 142 (91%) of the first 156 radial keratotomies performed. The results are contrasted with our earlier six-month and one-year results and with findings from other studies. Mean spherical equivalent before surgery was -5.0 diopters and two years after surgery was -0.10 D; 51% of the eyes were within 1 D of emmetropia. Uncorrected distance acuity was 20/200 or worse in 96% of the eyes before surgery. At two years, 39% had 20/20 acuity or better and 76% had 20/40 or better. At one year, 49% had 20/20 acuity and 76% had 20/40 acuity or better. Refractive results between one and two years showed an overall increase in mean spherical equivalent of 0.23 D. Our results indicate radial keratotomy to be relatively safe and effective two years after surgery.

Ptosis following radial keratotomy. Performed using a rigid eyelid speculum

Seven patients with acquired ptosis and normal levator function following anterior radial keratotomy are presented. Five of these patients then elected to undergo radial keratotomy of the opposite eye, and four had symmetrical lid fissures (mild bilateral ptosis) after bilateral surgery. Ptosis is a well-known complication of cataract extraction, but has not been reported following radial keratotomy. Unlike cataract extraction, radial keratotomy does not require anesthetic injections, bridle sutures, or conjunctival flaps. The rigid Knapp eyelid speculum used in these cases remains as the only apparent cause of eyelid trauma and subsequent ptosis. During radial keratotomy, the speculum was opened widely in order to provide good corneal exposure and avoid contact with the diamond knife. Contraction of the orbicularis oculi muscle against the rigid speculum may have traumatized the lid, resulting in a levator aponeurosis disinsertion and subsequent ptosis.

The prediction of surgically induced refractive change from corneal topography

PURPOSE

To develop a method to predict the refractive power of the cornea from corneal topography.

METHODS

We reviewed preoperative and postoperative cycloplegic refraction, keratometry, and corneal topography in 40 eyes of 40 patients who had undergone photorefractive keratectomy, radial keratotomy, myopic keratomileusis in situ, or hyperopic lamellar keratoplasty. For each axial dioptric power map, we calculated the aspheric ellipsoid that best fit that map. Central corneal points were weighted more heavily than peripheral points, based on the Stiles-Crawford effect. The equation of the best-fit ellipsoid yielded the spherical and astigmatic power and axis for each cornea preoperatively and postoperatively.

RESULTS

The preoperative corneal spherical and astigmatic powers measured by the best-fit method were consistent with the spherical and astigmatic powers measured by keratometry and simulated keratometry. The change in corneal spherical power predicted by the best-fit method was significantly (P < .05) more accurate at predicting the change in spherical equivalent refraction than change either in spherical equivalent keratometry or in spherical equivalent simulated keratometry. The prediction of the astigmatic change was less precise than that of the spherical, but the best-fit method was the most accurate.

CONCLUSIONS

The best-fit method is more accurate than simulated keratometry and standard keratometry are in evaluating corneal refractive power after refractive surgery. An improved method of calculating corneal refractive power may facilitate subjective refraction after refractive surgery, improve the accuracy of intraocular lens power calculation for eyes that have had previous refractive surgery, and improve ablation profiles for excimer laser refractive surgery.

Corneal aberrations increase with the magnitude of radial keratotomy refractive correction

BACKGROUND

Refractive surgery induces optically abrupt changes in shape in the midperiphery of the cornea. The abruptness of this change is in part dependent on the magnitude of the surgically induced refractive change. Therefore, the optical aberrations of the cornea, as quantified by wavefront variance (WFV), may be expected to increase as the surgically induced change in the refraction increases.

PURPOSE

It is the purpose of this study to test the hypothesis that as the surgery-induced change in refraction increases, so does the WFV of the cornea.

METHODS

Fourteen radial keratotomy (RK) patients and seven normal patients served as subjects. Measurements were made before and 2 years after RK surgery. To quantify the WFV of the cornea, we used corneal topography measurements to calculate the surgically induced change in corneal WFV with respect to two different reference surfaces, a sphere and the presurgical cornea. To quantify the surgically induced change in the equivalent spherical correction (ESC), cycloplegic refractions were performed. The measurements were summarized by regressing the surgically induced change in the WFV against the surgically induced change in the ESC.

RESULTS

For large pupils (7 mm diameter), the correlation between the change in the WFV referenced to a sphere and the change in the ESC was significant (p < 0.0001, r2 = 0.745) and dominated by fourth order aberrations. Similar results were found for the surgical lens. For small pupils (3 mm diameter), the effects were markedly reduced.

CONCLUSIONS

(1) As the magnitude of the surgically induced refractive change increases so does the WFV of the cornea, particularly for large pupils. (2) The increase in corneal WFV for large pupils is dominated by fourth order aberrations. (3) The increase in corneal WFV is consistent with reported decreases in visual function (contrast sensitivity and low contrast visual acuity), particularly for large pupil diameters in combination with large surgically induced changes in refractive error.

Treatment of postoperative endophthalmitis

Despite many advances in microsurgery, asepsis, antibiotics and intraocular lenses, postoperative endophthalmitis continues to be responsible for the loss of many eyes. In a series of 153 cases of endophthalmitis with a positive culture, 115 occurred after ophthalmic surgery. Eyes appear to be more vulnerable to this complication after extracapsular lens extraction in particular. The analysis of the patients operated for cataract in our own department shows that the incidence of endophthalmitis is 3 times higher in the extracapsular group with lens implantation than in the group of intracapsular lens extraction without lens implantation. Quick diagnosis and prompt action are essential to successful treatment. The treatment consists of vitrectomy and has the following three purposes: (1) provision of a good specimen for direct bacteriological examination and culture; (2) removal of toxins and cells, and (3) creation of space for the injection of an antibiotic. The authors found highly divergent prognoses and bacteriological patterns for endophthalmitis following vitrectomy, bleb surgery and cataract. Similar bacteriological agents do not give rise to the same prognosis after different operations. The post-lens implantation group (88 cases) permitted a distinction to be made between intracapsular and extracapsular surgery. A statistically significantly higher percentage of infection by low-virulence organisms (e.g. Staphylococcus epidermidis) was seen after extracapsular surgery: 60% compared to 30%. The analysis shows that this difference in bacteriological spectrum is the sole explanation for the better functional results following extracapsular surgery.

Endophthalmitis and orbital cellulitis after radial keratotomy

PURPOSE

To report the findings concerning three patients with endophthalmitis and one with panophthalmitis and orbital cellulitis radial keratotomy surgery.

METHODS

One man referred with panophthalmitis and orbital cellulitis and three women referred with endophthalmitis were treated.

RESULTS

After radial keratotomy surgery, during which no microperforation or macroperforation had been reported, a severe Pseudomonas panophthalmitis and orbital cellulitis developed in the man. All vision was lost in that eye. Staphylococcus epidermidis endophthalmitis developed in one woman, Streptococcus pneumoniae endophthalmitis in the second woman and Pseudomonas endophthalmitis in the third woman, after undergoing radial keratotomy procedures during which microperforations occurred. In the latter patient, bilateral simultaneous surgery was performed, but only one eye became infected. The latter two infections resulted in light perception and hand motion vision respectively. In three cases, an initial keratitis was located in the inferior cornea.

CONCLUSIONS

Severe bacterial endophthalmitis can occur after radial keratotomy surgery, even in the absence of microperforation during the procedure. Any evidence of postoperative keratitis must be regarded seriously and treated aggressively. Despite use of this approach, the effect on final visual acuity can be devastating.

Corneal sensitivity after radial keratotomy

Corneal sensitivity was tested in 76 eyes of 40 patients who underwent radial keratotomy for the correction of myopia, and radial keratotomy plus transverse incisions for the correction of myopia and astigmatism. There was a decrease in corneal sensitivity in 30.9 and 9.5% of patients undergoing radial keratotomy after 6 and 12 months, respectively. Approximately 70% of patients in this group had a recovery of lost sensitivity after 6 months. There was a similar decrease in sensitivity in 79.4 and 47.0% of patients undergoing radial keratotomy with the addition of transverse incisions for astigmatism at 6 and 12 months, respectively. The recovery rate in this group was 40.7%. The most significant loss of corneal sensation was in the areas central to the transverse incisions. The depth of the transverse incision, as well as the preoperative astigmatism, appeared to be factors in the loss of corneal sensation as well as in the recovery of the corneal sensitivity. There were no complications noted in this study as a result of decreased corneal sensitivity.

Corneal topography and fluctuating visual acuity after radial keratotomy

A high-resolution photokeratoscope using computer graphics to model corneal topography was used on patients who had undergone radial keratotomy. After radial keratotomy, central optical zones are created that can be characterized as round, oval or band-like, or dumbbell-shaped or split. The dumbbell form of optical zone was associated with larger amounts of refractive and keratometric astigmatism than the round or band-like zones. The authors correlated the shape of the optical zone with the presence or absence of diurnal variation (fluctuation) in visual acuity. Of the 26 eyes studied, 11 experienced fluctuation and 15 did not. Of those 11 eyes with fluctuating visual acuity, 10 (91%) had dumbbell-shaped or split optical zones and 1 (9%) had a round optical zone. Of the 15 eyes without fluctuation, 12 (80%) had round optical zones and 3 (20%) had band-like zones. The presence of a split or dumbbell-shaped optical zone after radial keratotomy indicates that the patient is likely to experience diurnal fluctuation of visual acuity.

Hyperopic automated lamellar keratoplasty: complications and visual results

OBJECTIVE

To examine the long-term safety and efficacy of hyperopic automated lamellar keratoplasty (H-ALK) for correction of primary hyperopia and for consecutive hyperopia following overcorrected myopic refractive surgery.

METHODS

A prospective study was done on 67 eyes of 50 consecutive patients who underwent H-ALK between March 17, 1993, and August 18, 1995. Hyperopic automated lamellar keratoplasty was performed for primary hyperopia in 25 eyes (group 1) and for consecutive hyperopia after myopic refractive surgery in 42 eyes (group 2, radial keratotomy, 41 eyes, and myopic automated lamellar keratoplasty, 1 eye). The eyes were followed up for a mean+/-SD of 19.2+/-12.8 months (range, 3-49 months), 58 (87%) of them with 6 months' follow-up, and 45 (67%) of them with at least 1 year's follow-up. Twenty-one eyes were followed up for 2 to 4 years.

RESULTS

The overall mean+/-SD preoperative spherical equivalent was +2.87+/-1.28 diopters (D). The mean+/-SD postoperative spherical equivalent was -0.03+/-1.42 D at 3 months, -0.42+/-2.25 D at 6 months, -0.55+/-3.00 D at 1 year, -1.58+/-1.53 D at 2 years, and -0.35+/-1.79 D at the last follow-up. A mean myopic shift of 0.50 D was noted between 3 months and 1 year, and of 1.00 D between 1 and 2 years. Hyperopia was meaningfully reduced and visual acuity was improved by H-ALK, especially for patients with primary hyperopia. Long-term refractive instability, however, is a serious problem with this procedure. In this series, 11 (26%) of 42 eyes in which H-ALK was performed for consecutive hyperopia developed iatrogenic keratoconus.

CONCLUSION

Based on this study, the long-term instability of H-ALK and the high incidence of iatrogenic keratoconus following the procedure should discourage its use, especially for consecutive hyperopia following radial keratotomy.

Photorefractive keratectomy to correct hyperopic shift after radial keratotomy

To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) to correct post-radial-keratotomy (RK) hyperopic shift. University of Sherbrooke, Sherbrooke, Québec, Canada.This retrospective nonconsecutive case series comprised 53 eyes of 53 patients who had PRK to correct hyperopic shift after RK. Both RK and PRK were performed by the same surgeon at the same clinic from 1993 to 2001.The mean time after RK was 57 months (range 24 to 84 months). The mean follow-up after hyperopic PRK (HPRK) was 10 months (range 3 to 33 months). The mean hyperopic shift 1 month post-RK to HPRK was +1.6 diopters (D) +/- 1.0 (SD) (range +0.25 to +4.125 D). The mean pre-HPRK spherical equivalent (SE) was +2.15 +/- 0.80 D (range +1.00 to +4.125 D) and the mean post-HPRK SE, -0.10 +/- 0.80 D (range -2.00 to +2.125 D). At the last examination, 47 eyes (88.7%) had a refractive error within +/-1.0 D of emmetropia and 38 eyes (71.7%) had an uncorrected visual acuity of 20/25 or better. Two eyes lost 1 Snellen line of best corrected visual acuity. No significant haze or complications developed in any eye. Hyperopic PRK with a conservative technique (large optical zone and small ablation thickness) can be used successfully to correct RK-induced hyperopia in patients with small to moderate refractive errors. It appeared to be effective, predictable, and safe.