Patterns of Corneal Topography after Penetrating Keratoplasty

Background

The topography of corneas after penetrating keratoplasty is highly variable. We classify the topography into five groups.

Methods

We performed videokeratography on 45 clear compact penetrating keratoplasties, with all sutures removed. Three ophthalmologists classified the keratographs independently into five previously defined topographic groups, based on the pattern of the normalized color-coded videokeratograph.

Results

The five topographic patterns included: prolate bow tie, 14 (30%); oblate bow tie, 14 (30%); mixed prolate and oblate bow tie, 8 (17%); asymmetric, 3 (9%); and steep/flat, 6 (14%). The three ophthalmologists agreed in their initial classification in 87% of the cases and after discussion, in 96%.

Conclusion

The topography of the cornea after penetrating keratoplasty can be classified into five qualitative groups by trained observers, with good clinical reliability.

Monocular Diplopia Related to Asymmetric Corneal Topography After Laser in situ Keratomileusis

PURPOSE

To show a specific relationship between monocular diplopia and corneal refractive asymmetry after laser in situ keratomileusis (LASIK).

METHODS

One hundred thirty-eight eyes of 98 patients who underwent LASIK for myopia between -2.12 and -17.75 D were examined under room-lighted conditions. We examined 51 eyes at 2 weeks, 46 eyes at 3 months, 32 eyes at 6 months, and 9 eyes at 1 year after LASIK. We attempted to correlate the presence of monocular diplopia with their corneal topographical features.

RESULTS

Eight eyes of five patients (five eyes at 2 weeks, three eyes at 3 months after LASIK) produced symptoms of monocular diplopia. These symptomatic patients had a common corneal topographical feature caused by decentralized or inhomogeneous ablation. Every pupillary area in the patients' topographies contained steeper and flatter areas. The range of refractive power variation in these asymmetric areas was at least 1.50 D. The location of the secondary image correlated with the direction of the steeper area in all eight eyes. Pinhole viewing eliminated or reduced the prominence of secondary images in every case.

CONCLUSION

Monocular diplopia following LASIK appears to correlate with postoperative corneal refractive power variation inside the pupillary area, caused by decentralized or inhomogeneous ablation.

Two-year outcomes of intrastromal corneal ring segments for the correction of myopia

OBJECTIVE

To evaluate the safety and efficacy of Intrastromal Corneal Ring Segments (ICRS) for the correction of myopia.

DESIGN

Nonrandomized, comparative trial.

PARTICIPANTS

Patients enrolled in the United States Food and Drug Administration phase II and phase III clinical trials of the ICRS had best spectacle-corrected visual acuity (BSCVA) of 20/20 or better, myopia of -1.00 to -3.50 diopters (D), and a cylindrical correction of 1.00 D or less as measured by manifest refraction.

INTERVENTION

Surgical correction of myopia with an ICRS.

MAIN OUTCOME MEASURES

Efficacy was assessed by predictability of refractive outcome (deviation from predicted cycloplegic refraction spherical equivalent), stability of refractive effect, and postoperative uncorrected visual acuity. Safety was assessed by adverse events, maintenance or loss of preoperative BSCVA, and induced manifest refraction cylinder.

RESULTS

Four hundred fifty-two patients were enrolled at 11 investigational sites in both studies. Of the 454 surgical attempts, 449 received an ICRS in one eye (0.25, 0.30, and 0.35 mm in 148, 151, and 150 eyes, respectively). First surgeries were attempted in 452 patients. An ICRS was successfully implanted in 447 initial eyes, and 5 surgeries were discontinued. Of the five discontinued surgeries, three patients subsequently exited from the study, and two patients went on to have the ICRS implanted in the second eye, bringing the total number of successful implants to 449 patient eyes. Month 24 postoperative follow-up was completed on 358 patients (80%). At month 24, 328 of 354 eyes (93%) were within +/-1.00 D of predicted refractive outcome. Refraction changed by 1 D or less in 97% of eyes (421/435) between 3 and 6 months after implantation and in 99% (343/348) between months 18 and 24. Before surgery, 87% of eyes (390/448) saw worse than 20/40 uncorrected; 24 months after surgery, 55% of eyes (196/358) saw 20/16 or better, 76% (271/358) saw 20/20 or better, and 97% (346/358) saw 20/40 or better. Although two eyes (2/358; 0.5%) lost two or more lines of BSCVA at 24 months; visual acuity in both was 20/20 or better. Intraoperative complications included anterior corneal surface perforation (three eyes) and anterior chamber perforations (two eyes, one during an attempted exchange procedure); all healed spontaneously without suturing and without loss of BSCVA. The ICRS was repositioned in five eyes to increase correction. Postoperative complications in one eye each were infectious keratitis, shallow segment placement, and loss of two lines of BSCVA at two or more consecutive examinations (subsequently regained).

CONCLUSIONS

The ICRS safely, predictably, and effectively reduced or eliminated myopia of -1.00 to -3.50 D. The refractive effect was stable over time.

Laser in situ keratomileusis: surgical technique

Laser in-situ keratomileusis is an increasingly popular technique for the correction of refractive errors that was initially described by Pallikaris in 1990. It involves the excimer laser ablation of corneal stroma beneath a hinged corneal flap that is created with a microkeratome. The purpose of this chapter is to report the LASIK surgical technique that has evolved at the Emory Vision Correction Center since 1995 when an investigation study of this technique for the correction of myopia began.

Laser in situ keratomileusis for myopia up to -11 diopters with up to -5 diopters of astigmatism with the summit autonomous LADARVision excimer laser system

OBJECTIVE

To assess the safety and effectiveness of the Summit Autonomous LADARVision active tracking narrow beam excimer laser system for laser in situ keratomileusis (LASIK) correction of myopia and astigmatism.

DESIGN

A multicenter, prospective noncomparative case series.

PARTICIPANTS

This cohort consisted of 177 eyes corrected for spherical myopia up to -11 diopters (D) and 170 eyes corrected for myopia up to -11 D spherical equivalent with astigmatism up to -5 D.

INTERVENTION

Treatments were performed at four sites in the United States using a 6-mm optic zone for spherical myopes and a 5.5-mm optic zone with a 1-mm blend for astigmats.

MAIN OUTCOME MEASURES

Visual acuity, subjective refraction, vector analysis, subject satisfaction, intraocular pressure, complications, and adverse reactions.

RESULTS

Six-month follow-up was available on 157 spherical eyes and 113 astigmatic eyes. For spherical myopes, uncorrected visual acuity (UCVA) was 20/20 or better in 60.5%, 20/25 or better in 80.3%, and 20/40 or better in 93.9%. The mean spherical equivalent was -0.29 +/- 0.45 D with 75.2% +/- 0.50 D and 94.9% +/- 1.00 D of intended. A loss of two lines of best spectacle-corrected visual acuity (BSCVA) occurred in 0.6%, and no eyes lost greater than two lines of BSCVA. For astigmatic myopes, UCVA was 20/20 or better in 52.0%, 20/25 or better in 74.5%, and 20/40 or better in 94.1%. The mean spherical equivalent was -0.23 +/- 0.49 D with 75.2% +/- 0.50 D and 95.6% +/- 1.00 D of intended. A loss of two lines of BSCVA occurred in 0.9%, and no eyes lost greater than two lines of BSCVA. Vector analysis showed that 99% of the intended cylinder was corrected on average with a mean angle of error of 4.2 degrees. Refractive stability was achieved between 1 and 3 months in 97.5% of spherical eyes and 99.4% of astigmatic eyes and confirmed between 3 and 6 months in 100% of both spherical and astigmatic eyes.

CONCLUSIONS

Eyes treated for myopia up to -11 D of spherical equivalent with or without astigmatism up to -5 D show early refractive stability, good UCVA outcomes, no significant loss of BSCVA, accurate correction of astigmatism, and slight undercorrection without a change from the photorefractive keratectomy algorithm and with a single treatment.

Intrastromal Corneal Ring Segments: Reversibility of Refractive Effect

PURPOSE

To evaluate the reversibility of refractive effect following removal of the ICRS (intrastromal corneal ring segments; Intacs).

METHODS

Data from 34 eyes from which ICRS were removed during United States FDA Phase II and III clinical trials were evaluated with regard to segment size, loss or change of best spectacle-corrected visual acuity (BSCVA), any change of uncorrected visual acuity (UCVA), manifest spherical equivalent refraction, manifest cylinder refraction, stability of manifest cylinder refraction, and subjective visual symptoms.

RESULTS

Out of 725 initial or contralateral eyes placed with the ICRS during Phase II and III clinical trials, segments were removed from 34 eyes (4.7%). Other than one (1/725, 0.1%) safety related ICRS removal, 30/725 (4.1%) were due to visual symptoms. ICRS removal was accomplished under topical anesthesia without complications in all eyes. The mean length of time the segments remained in the cornea after initial surgery was 10.3 +/- 5.4 months. At 3 months after ICRS removal, 21 eyes had monitored data available and were within +/-1 line or 10 letters of their preoperative BSCVA. Twenty eyes (20/21, 95%) returned to within +/-1.00 D of their preoperative manifest spherical equivalent refraction. All eyes had a stable refraction at the 3-month examination after removal, and a manifest spherical equivalent refraction within +/-1.00 D of their 1-month examination after removal. Nineteen eyes (19/21, 90%) returned to within +/-2 lines and 16 eyes (16/21, 76%) returned to within +/-1 line of preoperative UCVA.

CONCLUSION

The ICRS (Intacs) was easily and safely removed, and eyes returned to preoperative refractive status within 3 months.

Effects of laser in situ keratomileusis (LASIK) on the corneal endothelium 3 years postoperatively

PURPOSE

To investigate the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium 3 years postoperatively.

METHODS

Patients who were subjects of a previous prospective study (Am J Ophthalmol 125:465-471, (April) 1998) were contacted for a follow-up analysis of the central corneal endothelium. Noncontact specular microscopy was performed 35 to 37 months after LASIK on 52 eyes of 27 patients of the original cohort of 98 eyes of 65 patients and six eyes of three patients who were previously lost to follow-up after their initial post-LASIK evaluation. Patient age ranged from 29 to 66 years at the time of the original LASIK procedure. Attempted corrections ranged from 2.25 to 14.5 diopters of myopia, giving theoretical ablation depths of 182 to 332 microm below the corneal surface. Forty-eight eyes (83%) had a history of preoperative contact lens use (3 to 33 years). Central endothelial cell density, coefficient of variation of cell size, and percent of hexagonal cells were analyzed using 72 to 152 cells from each image. Multivariate analysis was used to search for factors that might predict changes in cell density, coefficient of variation, and percent of hexagonal cells.

RESULTS

The mean +/- SD preoperative cell density was 2,498 +/- 354 cells per mm(2), the mean coefficient of variation was 0.36 +/- 0.07, and the percent of hexagonal cells was 58 +/- 6. Three years after surgery there was no statistically significant change in the mean endothelial cell density (2,489 +/- 335 cells per mm(2); P = 0.88, paired t test) or the percent of hexagonal cells (60 +/- 7; P = 0.14, paired t test). The mean coefficient of variation was significantly lower postoperatively (0.32 +/- 0.04; P = 0.0006, paired t test); a repeated measures analysis showed that this significant improvement could not be explained by cessation of contact lens wear after LASIK (P = 0.34). Multivariate analysis did not identify any factors that were predictive of change in cell density, coefficient of variation, and percent of hexagonal cells.

CONCLUSIONS

Laser in situ keratomileusis for the correction of 2.25 to 14.5 diopters of myopia had no significant effect on central corneal endothelial cell density or the percent of hexagonal cells 3 years after surgery. The coefficient of variation of cell size improved significantly 3 years after surgery.

Diurnal stability of refraction after implantation with intracorneal ring segments

PURPOSE

To investigate diurnal changes in visual acuity and refraction in myopic eyes implanted with intracorneal ring segments (ICRS).

SETTING

University of California San Diego Shiley Eye Center, La Jolla, California, and Emory University Vision Correction Center, Atlanta, Georgia, USA.

METHODS

This prospective study involved 2 groups of patients who had ICRS (Intacs) implantation and a follow-up of at least 6 months. The first group included 102 eyes of 51 bilaterally treated patients; the second group, 32 eyes of 16 unilaterally treated patients. Examinations including visual acuity, manifest refraction, and videokeratography were done in the morning and evening at least 9 hours apart on a single day. Refractive changes were analyzed by power vectors; multivariate statistics were used to determine the significance of change in any component of the spectacle prescription.

RESULTS

In the bilateral treatment group, 97 eyes (95%) were within 1 line of spectacle-corrected visual acuity from morning to evening. The mean change in manifest refraction was -0.14 +0.08 x 4 and in spherical equivalent, -0.10 diopters (D) (sigma = 0.3; range -0.750 to +0.875 D). Ninety-six eyes (94%) had a change in refraction within 0.50 D of spherical equivalent. There was no significant change in corneal power (P =.20). In the unilateral treatment group, there was no significant difference between treated and untreated eyes in changes in spectacle-corrected visual acuity, manifest refraction, or corneal power and toricity (P.05).

CONCLUSION

No clinically significant diurnal variation in visual acuity or manifest refraction was observed after ICRS implantation or in untreated paired eyes. Moreover, the data suggest less diurnal change in visual acuity and refraction after ICRS implantation.

Videokeratography after excimer laser in situ keratomileusis for myopia

OBJECTIVE

The purpose of this study was to define qualitative patterns of videokeratography after excimer laser in situ keratomileusis (LASIK) for myopia and to identify associations of videokeratography patterns with clinical variables.

DESIGN

Single-center, retrospective, cohort study.

PARTICIPANTS

One hundred twenty-six eyes of 68 patients with myopia who desired surgical correction of myopia ranging from -1.50 to -8.80 diopters.

INTERVENTION

Myopia was corrected with LASIK using a Summit OmniMed/Apex excimer laser. Computer-assisted videokeratography data were acquired at 3 months after primary LASIK, and associations of videokeratography pattern with clinical variable were assessed.

MAIN OUTCOME MEASURES

Seven subgroup ablation zone patterns were characterized using tangential curvature maps; these subgroups were combined into pooled symmetric and asymmetric groups. Associations with age, attempted correction, single-zone or multizone ablation, postoperative uncorrected and spectacle-corrected visual acuity, predictability, astigmatism, corneal uniformity, glare disability, and contrast sensitivity were analyzed.

RESULTS

Thirty-two eyes (25.4%) showed a uniform pattern, 14 eyes (11.1%) showed a bow-tie pattern, 22 eyes (17.5%) showed a peninsula pattern, 22 eyes (17.5%) showed a semicircular pattern, 22 eyes (17.5%) showed an off-center blue spot pattern, 10 eyes (7.9%) showed an irregular pattern, and 4 eyes (3.2%) showed a central island pattern. Spectacle-corrected visual acuity, astigmatism, corneal uniformity, glare disability, and contrast sensitivity were significantly related to videokeratography pattern, although the difference among videokeratography groups was clinically small. Age, attempted correction, single- or multizone ablation, and postoperative uncorrected visual acuity and predictability were not predictive of videokeratography pattern.

CONCLUSIONS

Most eyes in this study had an asymmetric videokeratography pattern 3 months after LASIK. Small but statistically significant differences were identified among the videokeratography patterns that potentially may affect postoperative quality of vision.

Multiple regression and vector analyses of laser in situ keratomileusis for myopia and astigmatism

PURPOSE

To construct a quantitative model relating refractive results to laser settings and other factors.

METHODS

A prospective clinical trial was performed, including 14 surgeons and 523 eyes of 278 patients who desired correction of myopia from -1.00 to -16.00 D (mean, -6.20 D) and astigmatism up to 6.00 D (mean, 1.10 D). Myopia and astigmatism were corrected by laser in situ keratomileusis (LASIK) with sequential spherical and cylindrical ablations using a 5.5-mm ablation zone and a transition zone to 7.0 mm. The Nidek EC-5000 excimer laser and the Chiron Automated Corneal Shaper were used.

RESULTS

Surgically induced refractive changes 3 months after surgery were measured. Spherical ablation by LASIK produced a 19% greater refractive change than that predicted by the Nidek PRK algorithm. The laser setting needed to achieve each 1.00 D of cylinder correction induced 1.30 D change in spherical equivalent refraction (0.80 D more than expected). Patient age and nonlinear effects had small but statistically significant influences on refractive outcome. Sex, left/right eye, and surgeon were not significant factors. Residual variations in spherical equivalent refraction included a 0.50-D constant plus 9% of the predicted spherical equivlanet change. Residual variations in the parallel and orthogonal components of cylinder correction were, respectively, 28% and 13% of the predicted cylinder change plus a 0.30-D constant component. The standard deviation of axis alignment error for cylinder ablation was 3.7 degrees.

CONCLUSIONS

Cylindrical ablation produced a spherical change that was larger than expected. To compensate for this, spherical ablation should be reduced in eyes with astigmatism. Variability in the correction of astigmatism was proportionally larger than that for spherical correction and was primarily due to magnitude rather than axis error.

Conjunctival deposits as an initial manifestation of sarcoidosis

PURPOSE

To report conjunctival deposits as an initial manifestation of sarcoidosis.

METHODS

Case reports.

RESULTS

Two patients with bilateral bulbar conjunctival white deposits underwent conjunctival biopsy. The biopsy specimens showed noncaseating granulomas with prominent Schaumann bodies. Serum angiotensin-converting enzyme levels were increased in both patients. The first patient had abnormal results of pulmonary function tests. Sarcoidosis was diagnosed in both patients.

CONCLUSIONS

Conjunctival deposits may represent the initial clinical manifestation of sarcoidosis.

Diurnal fluctuations in corneal topography 10 years after radial keratotomy in the Prospective Evaluation of Radial Keratotomy Study

PURPOSE

To correlate clinically observed fluctuations in manifest refraction, visual acuity, keratometry, and intraocular pressure (IOP) with changes in the anterior corneal surface as measured by videokeratography in patients 10 years after radial keratotomy (RK).

SETTING

Four clinical centers in the United States that participated in the Prospective Evaluation of Radial Keratotomy (PERK) study.

METHODS

Thirty-two eyes of 20 PERK patients who noted diurnal fluctuations in vision had clinical examination and videokeratography (TMS-1, Computed Anatomy Inc.) in the morning and evening of the same day a mean of 10.3 years (range 7.8 to 11.7 years) after RK. The videokeratographs were analyzed in terms of various indexes generated by custom-designed software. Morning-to-evening changes in the means of the various clinical and videokeratographic values were assessed using pairwise methods.

RESULTS

The mean increase in myopia was 0.36 diopters (D) +/- 0.58 (SD) from morning to evening (P < .01). Analysis of the videokeratographs showed a corresponding increase in average corneal power (ACP), reflecting a steepening of 0.52 +/- 0.45 D (P < .001). The change in ACP was correlated with a change in the manifest spherical equivalent refraction (R = 0.39, P = .03) and a change in best spectacle-corrected visual acuity (R = 0.38, P = .03) over the same period. Similarly, simulated keratometry (SimK) readings correlated with the change in the manifest spherical equivalent refraction (R = 0.38, P = .03 for SimK1; R = 0.37, P = .35 for SimK2; R = 0.4, P = .02 for average SimK), although the standard clinical keratometric data did not (P = .26 for K1, P = .11 for K2, and P = .09 for the mean K). The elevation depression magnitude, a measure of the low-frequency irregularities of the cornea, showed a decrease of 0.32 +/- 1.59, which also correlated with the change in the manifest spherical equivalent refraction (R = 0.37, P = .04). Intraocular pressure tended to decrease from morning to evening (mean change of -0.97 +/- 3.29 mm Hg), but the difference was not significant. Variations in IOP in individual patients, however, were correlated with changes in the manifest spherical equivalent refraction (R = 0.37, P = .04).

CONCLUSIONS

Diurnal fluctuations in corneal topographic indexes can be used to evaluate the diurnal fluctuations in refraction and visual acuity after RK. The study findings provide statistical support for the idea that IOP contributes to the diurnal fluctuation in visual acuity after RK.

Prospective randomized comparison of simultaneous and sequential bilateral laser in situ keratomileusis for the correction of myopia

OBJECTIVE

To study the safety and efficacy of simultaneous bilateral laser in situ keratomileusis (LASIK).

DESIGN

Prospective randomized clinical trial.

PARTICIPANTS

Fourteen surgeons and 714 consecutive eyes of 357 patients who desired surgical correction of myopia ranging from -2.00 to -22.50 diopters.

INTERVENTION

Patients were randomized to simultaneous or sequential bilateral LASIK.

MAIN OUTCOME MEASURES

Primary outcome measures were safety and efficacy. Procedure safety was assessed, for simultaneous and sequential groups, by comparison of intraoperative and postoperative complication rates and the percentage of eyes losing two or more lines of spectacle-corrected visual acuity. Procedure efficacy was assessed by comparison of the percentage of eyes with uncorrected visual acuity better than or equal to 20/20 and 20/40 and the percentage of eyes within +/-0.50 and +/-1.00 diopters of intended outcome.

RESULTS

Three hundred seventy-eight eyes were enrolled in the simultaneous group, and 331 eyes were enrolled in the sequential group. Mean follow-up was 10 months (+/-4.2 months standard deviation; range, 2 weeks-22 months). There was no significant difference in intraoperative complication rate (P = 0.55), loss of two or more lines of spectacle-corrected visual acuity (P = 0.87), or percentage of eyes within +/-0.50 diopters of intended correction (P = 0.17) between simultaneous and sequential groups. Postoperative complications were not significantly different in the two groups except for the unexplained more frequent epithelial ingrowth in the simultaneous group (2.9%) than in the sequential group (0.6%). The adjusted odds ratio for epithelial ingrowth in the simultaneous group was 1.02 (95% confidence interval, 1.01-1.08). There was no increased likelihood of epithelial ingrowth in the second of two simultaneously treated eyes (P = 0.95).

CONCLUSION

The outcomes and complications of performing bilateral simultaneous LASIK were not significantly different from those of sequential treatments, with the unexplained exception of more frequent epithelial ingrowth in the simultaneous group.

Randomized bilateral comparison of excimer laser in situ keratomileusis and photorefractive keratectomy for 2.50 to 8.00 diopters of myopia

OBJECTIVE

To compare effectiveness, safety, and stability of excimer laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for low-to-moderate myopia.

DESIGN

Prospective, randomized, bilateral study.

PARTICIPANTS

Thirty-three patients with a manifest refraction of -2.50 to -8.00 diopters (D) participated.

INTERVENTION

For each patient, one eye received LASIK and the other received PRK. The first eye treated, and surgical method in the first eye, were randomized. Both eyes were treated by the same surgeon during the same operative session with a Summit Omnimed I laser (6-mm-diameter ablation) and a Chiron Automated Corneal Shaper. Follow-up was 90% at 1 and 2 years.

RESULTS

At baseline, mean (+/-standard deviation) spherical equivalent manifest refraction was -4.80 +/- 1.60 D in LASIK-treated eyes and -4.70 +/- 1.50 D in PRK-treated eyes. At 1 day after surgery, 81% of patients (21 eyes) reported no pain in the LASIK-treated eye, whereas no patient (0%) reported being pain-free in the PRK-treated eye. At 3 to 4 days after surgery, 18 (80%) LASIK-treated eyes either improved or remained within 1 line of baseline spectacle-corrected visual acuity; only 10 (45%) PRK-treated eyes achieved this result. At 2 years after surgery, 18 (61%) LASIK- and 10 (36%) PRK-treated eyes achieved an uncorrected visual acuity of 20/20 or better, with no statistically significant difference in refractive outcome between the two techniques. Quantitative videokeratography showed more regularity after LASIK. Complications were similar in the two groups. Patients preferred LASIK by a margin of 2 to 1 at 1 year but showed no preference at 2 years.

CONCLUSIONS

Using a 6-mm-diameter single-pass, large area ablation and an automated microkeratome to treat myopia of -2.50 to -8.00 D with 1.00 D or less astigmatism in 1994, the authors used LASIK to produce a higher percentage of eyes with an uncorrected visual acuity of 20/20 or better, more regular postoperative corneal topography, less postoperative pain, and more rapid recovery of baseline spectacle-corrected visual acuity than PRK. Both LASIK and PRK achieved successful correction of low-to-moderate myopia at 1 and 2 years after surgery.

Complications of laser in situ keratomileusis for the correction of myopia

OBJECTIVE

To determine the incidence and severity of complications from laser in situ keratomileusis (LASIK) for the correction of myopia by experienced and inexperienced surgeons.

DESIGN

Prospective, observational clinical study.

PARTICIPANTS

Fourteen surgeons and 1062 eyes of 574 myopic patients who desired surgical correction of myopia ranging from -2.00 to -22.50 diopters (D; mean, -7.57 D) and astigmatism no greater than 4.00 D participated in this study.

INTERVENTION

Myopia was corrected with LASIK. Astigmatism was corrected with arcuate keratotomy at the same time as the initial procedure or subsequently.

MAIN OUTCOME MEASURES

Primary outcome measures were change in best spectacle-corrected visual acuity (BSCVA) and the incidence of complications.

RESULTS

Eyes were followed for a mean of 9.5 months after their last surgical procedure (range, 2 weeks-21 months). Three hundred eighty-one eyes (36%) underwent 468 enhancement procedures 3 months or more after the initial treatment. There were 27 (2.1%) intraoperative and 40 (3.1%) postoperative complications. Laser ablation was not performed during the initial treatment of 17 (1.6%) eyes because of intraoperative complications. Seventy-four eyes gained 2 or more lines of BSCVA, while 50 eyes lost 2 or more lines of BSCVA. Only three eyes lost two or more lines of BSCVA to a level worse than 20/40. One eye with a flap buttonhole (BSCVA 20/50) also had an epiretinal membrane. The second eye (BSCVA 20/60) had a flap buttonhole that may have been related to a previous corneal transplant. The third eye (-22.50 D before surgery) had a rhegmatogenous retinal detachment develop, reducing BSCVA from 20/60 to 20/200. The incidence of intraoperative complications decreased from 3.1% during the first 3 months to 0.7% during the last 9 months of the study (P = 0.02).

CONCLUSIONS

LASIK is acceptably safe for the correction of myopia. Although complications occur in approximately 5% of cases, these rarely lead to visual loss of more than two Snellen lines and postoperative acuity below 20/40. Flap buttonholes were more likely to cause loss of BSCVA than free or incomplete flaps (P = 0.02); flap buttonholes may be more likely in eyes that have undergone previous surgery. Complication rates can be reduced as the surgical team gains experience.

Prospective comparison of single-zone and multizone laser in situ keratomileusis for the correction of low myopia

OBJECTIVE

This study aimed to determine whether there is a true difference in predictability between single-zone and multizone laser in situ keratomileusis (LASIK) for the correction of low myopia or whether any difference in predictability is because of a need for separate clinical nomograms for the two treatments.

DESIGN

A prospective, randomized, clinical trial.

PARTICIPANTS

Fourteen surgeons and 190 eyes of 95 patients with myopia who desired surgical correction of myopia ranging from -2.00 to -7.00 diopters (D) participated.

INTERVENTION

Fellow eyes of patients with myopia undergoing bilateral simultaneous LASIK were randomized to single-zone and multizone ablation. Astigmatism was not corrected at the time of LASIK.

MAIN OUTCOME MEASURES

Predictability, postoperative videokeratography, and contrast sensitivity were assessed at 3 months after surgery.

RESULTS

At 3 months, r2 values relating laser setting to change in spherical equivalent refraction were 0.78 for single-zone and 0.76 for multizone ablation; mean outcome with respect to intended was -0.84 D (0.65 standard deviation [SD]) for single-zone and -0.62 D (0.78 SD) for multizone eyes (P = 0.035). There was no relationship between single-zone and multizone ablation and the likelihood of asymmetric postoperative videokeratography (P = 0.83). The only difference in contrast sensitivity was a significantly greater decrease in log contrast for multizone eyes at 12 cyc/deg under undilated conditions.

CONCLUSIONS

There is no true difference in predictability between single-zone and multizone LASIK for the correction of low myopia. Separate clinical nomograms for single-zone and multizone LASIK should eliminate the difference in predictability that was observed in this clinical trial.

Effects of laser in situ keratomileusis (LASIK) on the corneal endothelium

PURPOSE

To assess the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium.

METHODS

In a prospective study, the corneal endothelium of 98 eyes of 65 consecutive patients (mean age, 41 years; range, 22 to 66 years) was photographed before, 2 weeks after, and 12 weeks after LASIK for the correction of 2.75 to 14.5 diopters of myopia. Theoretical ablation depths were 200 to 330 microm below the corneal surface. Cell density, coefficient of variation, and percent of hexagonal cells were determined using 150 to 200 cells from each image. Eighty-eight eyes (91%) of 59 patients had a history of contact lens wear.

RESULTS

The mean+/-SD preoperative endothelial cell density was 2,549+/-365 cells per mm2, and the mean coefficient of variation was 0.35+/-0.06. There was no statistically significant change in the mean endothelial cell density or mean coefficient of variation of cell size at the 2-week (2,561+/-360 cells per mm2 and 0.35+/-0.06) or 12-week (2,541+/-364 cells per mm2 and 0.35+/-0.05) postoperative examinations. The percent of hexagonal cells was not significantly changed 2 weeks postoperatively; however, 12 weeks postoperatively (P=.0413, two-tailed t test), the percent of hexagonal cells was decreased by 1%.

CONCLUSIONS

Corneal endothelial cell density and morphology were unchanged 2 and 12 weeks after LASIK for the correction of up to 14.5 diopters of myopia. In this LASIK study, the correction of up to 14.5 diopters of myopia appears to cause no clinically significant effect on corneal endothelial cell density or morphology.

Keratocyte repopulation in epikeratoplasty specimens

PURPOSE

To study the histology and pattern of keratocyte repopulation of surgically removed human epikeratoplasty lenticules.

METHODS

Removed epikeratoplasty lenticules and penetrating keratoplasty buttons that contained epikeratoplasty lenticules were evaluated for duration of epikeratoplasty, histologic and ultrastructural features, and average number of keratocytes per high-power microscopic field. The keratocyte density was compared with age-matched controls.

RESULTS

Fifteen epikeratoplasty specimens from eight penetrating keratoplasties and seven removed lenticules were reviewed. The indications for keratoplasty were myopia, keratoconus, and aphakia. The lenticules were in place for 7-120 months, and the keratocyte count ranged from 14 to 40 per high-power field. Keratocyte density increased to 30-40 per high-power field, similar to age-matched controls, at approximately 48 months postoperatively, similar to the density of the controls. Keratocytes appeared to have migrated from the periphery to the center of the lenticules.

CONCLUSIONS

Normal keratocyte density in epikeratoplasty lenticules is reached by approximately 48 months after surgery.

Results of phase III excimer laser photorefractive keratectomy for myopia. The Summit PRK Study Group

OBJECTIVE

The purpose of the study is to determine safety and efficacy outcomes of excimer laser photorefractive keratectomy (PRK) for the treatment of mild-to-moderate myopia.

DESIGN

A prospective, multicenter, phase III clinical trial.

PARTICIPANTS

A total of 701 eyes of 701 patients were entered in the study; 612 eyes were examined at 2 years after surgery.

INTERVENTION

Intervention was photorefractive keratectomy using the Summit ExciMed UV200LA excimer laser (Summit Technology, Inc., Waltham, MA). The treatment zone diameter used was 4.5 mm in 251 eyes (35.8%) and 5 mm in 450 eyes (64.2%). Attempted corrections ranged from 1.50 to 6.00 diopters (D).

MAIN OUTCOME MEASURES

Predictability and stability of refraction, uncorrected and spectacle-corrected visual acuity, refractive and keratometric astigmatism, corneal haze, contrast sensitivity, subjective reported problems of glare and halo, and patient satisfaction were the parameters measured.

RESULTS

At 2 years, 407 (66.5%) eyes achieved 20/20 or better uncorrected visual acuity and 564 (92.5%) eyes achieved 20/40 or better visual acuity. Three hundred thirty-six (54.9%) eyes were within 0.5 D and 476 (77.8%) eyes were within 1.0 D of attempted correction. Stability of refraction improved with time; 86.8% of eyes were stable within 1.0 D from 6 to 12 months, 94% were stable from 12 to 18 months, and 96.3% were stable from 18 to 24 months. There was no evidence of progressive or late myopic or hyperopic refractive shifts. One hundred fourteen (18.6%) eyes gained 2 or more lines of spectacle-corrected visual acuity, whereas 42 (6.9%) eyes lost 2 or more lines; however, of the latter, 32 (76.2%) had spectacle-corrected visual acuity of 20/25 or better and 39 (92.9%) eyes had 20/40 or better. Four hundred forty-two (72.2%) corneas were clear, 138 (22.5%) showed trace haze, 20 (3.3%) mild haze, 9 (1.5%) moderate haze, and 3 (0.5%) marked haze. On patient questionnaires, 87 (29.7%) patients reported worsening of glare from preoperative baseline; 133 (50.1%) reported worsening of halo symptoms from baseline.

CONCLUSIONS

Photorefractive keratectomy appears effective for myopic corrections of -1.50 to -6.00 D. Uncorrected visual acuity is maximized in most eyes by 3 months, although some patients require between 6 months and 1 year to attain their best postoperative uncorrected visual acuity and some may require from 1 to 2 years for stabilization of refraction. Refraction stabilizes progressively without evidence of late myopic or hyperopic refractive shifts. Optical sequelae of glare and halo occur in some patients treated with a 4.5- or 5-mm treatment zone.

Excimer Laser In Situ Keratomileusis to Correct Compound Myopic Astigmatism

PURPOSE

We studied the efficacy, predictability, stability, and safety of excimer laser in situ keratomileusis (LASIK) to correct myopia and astigmatism.

METHODS

We prospectively studied 87 consecutive eyes of 56 patients who received LASIK, divided into two groups: the myopic group included eyes with myopia more than -2.00 diopters (D) and astigmatism less than 0.50 D and the astigmatism group included eyes with myopia of more than -2.00 D and astigmatism of 0.50 D or more. The Chiron automated corneal shaper and the Nidek EC-5000 excimer laser were used in all eyes. A modified personal nomogram was used in all eyes. The changes in refractive sphere and cylinder, and complications were studied at 2 and 6 weeks, 3, 6, and 12 months after surgery. Preoperatively, the mean spherical equivalent refraction was -4.41 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.79 D (range, -2.25 to -15.50 D; SD, 2.45) in the astigmatism group. The mean spherical component of the refraction was -4.39 D (range, -2.25 to -7.25; SD, 1.74) in the myopia group and -5.19 D (range, -2.00 to -14.00; SD, 2.32) in the astigmatism group. The mean refractive cylinder was 1.19 D (range, 0.5 to 3.00 D; SD, 0.62) in the astigmatism group.

RESULTS

At 12 months, 81 eyes (93.6%) of 51 patients were examined; the mean spherical equivalent refraction was -0.43 D (range, +0.50 to -1.25 D; SD, 0.35) in the myopia group and -0.33 D (range, +1.25 to -2.13 D; SD, 0.52) in the astigmatism group. The mean spherical component of the refraction at 12 months was -0.33 D (range, +0.50 to -1.25 D; SD, 0.33) in the myopia group and -0.17 D (range, +1.50 to -1.50; SD, 0.48) in the astigmatism group. The mean refractive cylinder was 0.19 D (range, 0 to 0.75 D; SD, 0.25) in the myopia group and 0.32 D (range, 0 to 1.25 D; SD, 0.30) in the astigmatism group. The mean change in spherical equivalent refraction between 6 weeks and 12 months after surgery was -0.08 D toward myopia (range, -0.50 to -0.75 D; SD, 0.23) in both groups. No eyes lost two or more lines of spectacle-corrected visual acuity. Patient satisfaction was high in both groups. Complications included undercorrection that necessitated reoperation (three eyes), overcorrection (two eyes), and small disc diameter (one eye). No vision threatening complications were observed.

CONCLUSION

LASIK with the Nidek EC5000 laser is effective, reasonably predictable, stable, and safe for correction of compound myopic astigmatism with a spherical component between -2.00 and -14.00 D, and a cylindrical component between 0.50 and 3.00 D using the techniques in this study. Astigmatism is undercorrected with the current algorithm. Correction of higher amounts of astigmatism requires further study.

Progressive nonulcerative paracentral keratolysis associated with elevated corneal metalloproteinases

PURPOSE

We report a patient with progressive idiopathic, nonulcerative, noninflammatory, avascular, bilateral, paracentral and peripheral corneal thinning monitored for 13 years.

METHODS

Because of progressive corneal thinning, the patient underwent several surgical procedures, including an arcuate lamellar keratectomy with suturing, bilateral 15-mm diameter onlay lamellar corneoscleral epikeratoplasties, and removal of interface epithelial tissue. Over time, the keratolysis also thinned the donor stroma, requiring a lamellar tectonic graft. A biopsy was performed of the patient's cornea and conjunctiva, and the tissue was analyzed for proteolytic enzymes.

RESULTS

Increased quantities of matrix metalloproteinases (57 and 63 kDa) were extracted from the patient's normal-appearing and abnormal corneal samples but not from adjacent conjuctiva and sclera or normal controls. This is the first reported case with these clinical and laboratory findings.

CONCLUSION

A previously undescribed progressive idiopathic paracentral keratolysis is associated with increased quantities of matrix metalloproteinases. Clinical management requires tectonic corneal surgery.

Increased Corneal Scarring after Phototherapeutic Keratectomy in Fuchs' Corneal Dystrophy

PURPOSE

A 63-year-old female with Fuchs' endothelial corneal dystrophy, stromal edema and subepithelial scarring was inappropriately treated with phototherapeutic keratectomy, leading to a central focal circular corneal scar and decreased visual acuity that required penetrating keratoplasty.

METHOD

The host corneal button was bisected and fixed in 10% formaldehyde and in glutaraldehyde immediately after its removal.

RESULTS

Light microscopy demonstrated a central area of absent Bowman's layer with a thin layer of subepithelial fibrosis, stromal corneal edema, and thickened Descemet's membrane.

CONCLUSION

Correct estimation of differential ablation rates of tissue and shallow, repeated ablations followed by slit-lamp microscopy and/or videokeratography help prevent over-treatment.

Prospective, randomized comparison of simultaneous and sequential bilateral LASIK for the correction of myopia

PURPOSE

To study the safety and efficacy of simultaneous bilateral laser in-situ keratomileusis (LASIK) METHODS: Data were obtained from 254 consecutive patients that were randomized to simultaneous or sequential bilateral LASIK.

RESULTS

146 patients were enrolled in the simultaneous group and 108 patients were enrolled in the sequential group. Mean follow-up was 10 months (range 6-18). There was no significant difference in intraoperative complication rate (p = 0.34), loss of two or more lines of spectacle corrected visual acuity (p = 0.9), or percentage of eyes within +/- 0.50 D of intended (p = 0.63) between simultaneous and sequential groups.

CONCLUSIONS

The risk of performing bilateral simultaneous LASIK is not significantly different from that of sequential treatments.

One-year results of a prospective multicenter study of the Casebeer system of refractive keratotomy. Casebeer Chiron Study Group

PURPOSE

To evaluate the clinical results, predictability, stability, safety, and the patient satisfaction after refractive keratotomy for the correction of myopia and astigmatism using a defined protocol (the Casebeer system).

METHODS

The authors enrolled 324 patients (615 eyes) in a prospective study conducted by 18 surgeons. All procedures were performed using ultrasonic pachymetry with the diamond knife blade set at a length of 100% of the temporal paracentral corneal thickness reading and four to eight centripental (Russian style) incisions with or without fixation of the globe. Straight transverse incisions were done for astigmatism in 222 (36%) eyes. One to eight repeated operations (enhancements) were done on 241 (39%) eyes.

RESULTS

Mean baseline cycloplegic refraction was -3.68 +/- 1.59 diopters (D) (range, -0.88 to -8.25 D). One-year data were available for 546 eyes (89%). At 1 year, mean spherical equivalent cycloplegic refraction was -0.27 +/- 0.78 D (range, -3.13 to +3.00 D). There were 373 (68%) eyes with a refraction of +/- 0.50 D, and 483 eyes (89%) within +/- 1.00 D of emmetropia. Ten eyes (2%) were overcorrected by more than 1.00 D. Mean baseline refractive cylinder was 1.01 +/- 0.75 D (range, 0-5.75 D); at 1 year, the mean cylinder was 0.40 +/- 0.55 D (range, 0-2.50 D). Uncorrected visual acuity was 20/20 or better in 297 (54%) eyes and 20/40 or better in 93%. Six eyes (1%) lost two to three lines of spectacle-corrected visual acuity; the worst visual acuity was 20/30. Of patients responding to a standardized questionnaire, 320 (77%) wore no spectacles for distance or near vision; there was a significant increase in glare and fluctuation of vision from baseline; and 247 (90%) were very satisfied with the outcome.

CONCLUSIONS

Refractive keratotomy using radial incisions with or without transverse incisions and following the Casebeer system effectively reduces and often eliminates myopia and astigmatism with a high degree of safety. Enhancement surgery was required in 39% of eyes. Glare and fluctuation of vision increased postoperatively but were rated mild, and patient satisfaction was high.

Excimer laser phototherapeutic keratectomy before cataract extraction and intraocular lens implantation

PURPOSE

To determine whether sequential excimer laser phototherapeutic keratectomy (PTK) followed by cataract extraction and intraocular lens (IOL) implantation with power calculation based on the new corneal curvature is effective in managing superficial corneal disease.

METHODS

Of a consecutive series of 18 eyes of 16 patients who received PTK, extracapsular cataract extraction, and posterior chamber IOL insertion, twelve eyes had spheroidal degeneration and six eyes, calcific band keratopathy. The PTK was done with either a Summit ExciMed laser or a Visx 20/20 laser using a 5.0 to 6.0 mm diameter ablation zone. Intraocular lens calculations were done a mean of 3.3 months after PTK. Cataract surgery was by extracapsular cataract extraction with posterior chamber IOL implantation. Patients were followed up for a mean of 14 months.

RESULTS

Eighteen eyes completed follow-up examinations. Mean time between PTK and cataract surgery was 3.3 months. Phototherapeutic keratectomy was completed in one surgery session using one ablation treatment (ablation and slitlamp microscopy) in five eyes, two treatments in seven eyes, and three to seven treatments in six eyes. Eleven (61%) of 18 eyes had a final spherical equivalent refraction within +/- 1.00 diopter. Two eyes developed moderate to marked subepithelial reticular corneal haze from PTK. No vision-threatening complications occurred.

CONCLUSION

Excimer laser PTK followed by cataract extraction and posterior chamber IOL implantation can safely and effectively treat eyes with superficial corneal disease and age-related cataract. Calculation of the IOL power after the cornea has healed from the PTK compensates for changes in corneal curvature.

The effect of photorefractive keratectomy on the corneal endothelium

PURPOSE

The authors prospectively investigated the effect of excimer laser photorefractive keratectomy (PRK) for myopia on the corneal endothelium.

METHODS

Quantitative computer-assisted morphometric analysis of central and peripheral corneal endothelial cells was performed on 142 myopic eyes before and at 3 months, 1 year, and 2 years after PRK. The mean age of the subjects was 37 years (range, 21-66 years). Ninety-one (64%) of them had a history of contact lens wear. Mean attempted correction was -3.9 diopters (range, -1.6 to -6.0 diopters).

RESULTS

The mean preoperative endothelial cell density was 2660 cells/mm2 centrally and 2776 cells/mm2 peripherally. There was no change in central endothelial cell density at any of the postoperative examinations. The peripheral cell density decreased 4.1% (P = 0.003) at 3 months and 6.2% (P = 0.0001) at 1 year. However, the peripheral cell density was not significantly different from the preoperative value at 2 years. The peripheral coefficient of variation of cell size was 7.8% lower 2 years postoperatively than it was preoperatively, and this improvement was attributable to cessation of contact lens wear after PRK. The decrease in peripheral endothelial cell density at 1 year correlated with the amount of attempted correction, but there was no correlation between attempted correction and the change in central or peripheral endothelial cell density 2 years postoperatively.

CONCLUSION

For the correction of up to 6.0 D of myopia, PRK causes no detectable changes in central corneal endothelial cell density, but it does cause a transient, modest loss of peripheral corneal endothelial cells at 1 year. Variations in endothelial cell shape caused by contact lens wear resolve after PRK.

A prospective multicenter trial of excimer laser phototherapeutic keratectomy for corneal vision loss. The Summit Phototherapeutic Keratectomy Study Group

PURPOSE

The 193-nm argon fluoride excimer laser can remove corneal scars and smooth corneal irregularities, obviating corneal transplantation. We conducted a prospective multicenter trial of excimer laser phototherapeutic keratectomy for corneal vision loss as a basis for Food and Drug Administration premarket approval.

METHODS

We treated 232 eyes of 211 patients with corneal vision loss. All had corneal pathology in the anterior 100 microns of the stroma. Mean postoperative follow-up was 10 +/- 8 months. The primary outcome variable was change in best spectacle-corrected visual acuity.

RESULTS

At postoperative month 12, best spectacle-corrected visual acuity improved in 46 (45%) of 103 eyes and worsened in nine (9%) of 103 eyes by 2 or more Snellen lines. Best spectacle-corrected visual acuity improved by a mean of 1.6 +/- 2.8 Snellen lines (95% confidence interval, 1.1 to 2.1 lines). Every postoperative visit confirmed statistically significant improvement of mean best spectacle-corrected acuity. At month 12, treated eyes had a mean hyperopic shift in refraction of 0.87 diopter and a mean reduction in astigmatism of 0.36 diopter. Treatment appeared most effective in eyes with hereditary corneal dystrophies, Salzmann's nodular degeneration, and corneal scars, and least effective in eyes with calcific band keratopathy. Complications included recurrence of underlying pathology, corneal graft rejection, and bacterial keratitis.

CONCLUSIONS

Argon fluoride excimer laser phototherapeutic keratectomy is effective, with relatively few complications, for treating vision loss from corneal opacification or irregularity. Efficacy, however, varies widely depending upon individual eyes and underlying diagnoses.

Bacterial Keratitis After Photorefractive Keratectomy

Two patients who had excimer laser photorefractive keratectomy (PRK) for myopia developed bacterial keratitis, one from Staphylococcus epidermidis and the other with a negative culture. Both were treated with topical antimicrobial agents. One eye recovered an uncorrected visual acuity of 20/20. The other was left with a moderate subepithelial scar and an uncorrected visual acuity of 20/150.

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.

Excimer laser in situ keratomileusis under a corneal flap for myopia of 2 to 20 diopters

PURPOSE

We studied the efficacy and safety of a recent technique of keratomileusis for myopia, excimer laser in situ keratomileusis.

METHODS

We studied retrospectively 88 eyes of 63 patients who received excimer laser in situ keratomileusis with the Chiron Automated Corneal Shaper and the Summit OmniMed laser under a hinged corneal flap without sutures.

RESULTS

Mean follow-up was 5.2 months. Mean spherical equivalent of the manifest refraction before surgery was -8.24 diopters (range, -2.00 to -20.00 diopters). Mean spherical equivalent refraction after surgery was +0.22 +/- 1.42 diopters. Of 40 eyes with a baseline refraction from -2.00 to -6.00 diopters, 25 eyes (63%) had refraction within +/- 0.50 diopter of emmetropia, and 37 eyes (93%) had refraction within +/- 1.00 diopter. In eyes with baseline refraction of -6.12 to -12.00 diopters, postoperative refraction was within +/- 1.00 diopter in 19 (65%) of 29 eyes. In eyes with baseline refraction of -12.10 to -20.00 diopters, postoperative refraction was +/- 1.00 diopter in eight (43%) of 19 eyes. Overall, 64 (72.8%) of 88 eyes had a refraction within +/- 1.00 diopter after surgery. Between three weeks and five months after surgery the change in the mean spherical equivalent refraction was -0.61 diopter in the myopic direction. Uncorrected visual acuity after surgery was 20/20 or better in 31 eyes (36%) and 20/40 or better in 61 eyes (71%). Three eyes (3.6%) lost two lines or more of spectacle-corrected visual acuity, two from progressive myopic maculopathy and one from irregular astigmatism. No eyes had vision-threatening complications.

CONCLUSION

Excimer laser in situ keratomileusis under a corneal flap can be an effective method of reducing myopia between -2.00 and -20.00 diopters, with minimal complications. Current surgical algorithms need modification to improve predictability of outcome. Stability of refraction after surgery requires further study.

Hydrogel intracorneal lenses in aphakic eyes

BACKGROUND

The theoretical benefits of synthetic keratophakia over conventional corneal lamellar procedures are the elimination of donor concerns and superior refractive predictability. Additionally, synthetic material can be inspected for optical quality and power, and it can be sterilized. Furthermore, visual recovery should be more rapid since epithelium is not removed from the central part of the cornea and the need for keratocyte repopulation is eliminated.

OBJECTIVE

To present results on patients who received an intracorneal implant (Kerato-Gel, Allergan Medical Optics, Irvine, Calif) that was made from lidofilcon A, a glucose-permeable hydrogel with an equilibrium water content of 68%.

METHODS

The intracorneal implants were implanted in 35 adult patients for correction of aphakia. Inclusion criteria excluded patients with aphakia who were candidates for intraocular lenses.

RESULTS

A total of 19 patients were followed up through 2 years postoperatively. For 16 patients with 2-year postoperative refractive data, the average spherical equivalent was -0.63 +/- 2.07 diopters (D). At 2 years, 88% of patients were within +/- 3.00 D of plano and 50% were within +/- 1.00 D. the mean change in Snellen's line for corrected visual acuity was -3.25 lines at 2 years for all patients and -2.0 lines for a subgroup of five patients who were free of vision-limiting preoperative disease.

CONCLUSIONS

Results suggest that this intracorneal implant is well tolerated by the cornea and can provide predictable refractive results in patients with high-risk aphakia. Limitations of the procedure are uneven microkeratome resections, loss of best-corrected visual acuity, and irregular astigmatism in some patients. Although these data show good evidence of biocompatibility of the implant material, technical surgical progress is needed to advance this procedure into clinical therapeutic practice.

Keratoconus in two pairs of identical twins

We studied two sets of identical twins with keratoconus. The first 21-year-old pair had bilateral fully developed keratoconus and the second 35-year-old pair presented with early bilateral keratoconus detected by videokeratography. To our knowledge, these are the seventh and eighth sets of identical twins with keratoconus reported in the literature. They support the evidence of heredity as a factor in the etiology of keratoconus. Videokeratography proved to be a valuable adjunct for the detection of early keratoconus in a cornea with normal slit-lamp microscopy and photokeratoscopy results. Radial keratotomy in one eye produced an unstable refraction.

A laboratory exercise in the study of the gross structure of the eye

The dissection of the bovine eye, when it is based on procedures used in ophthalmic surgery, results in an enthusiastic reception by medical students.

Automated In situ Keratomileusis for Myopia

BACKGROUND

In situ keratomileusis is a rapidly changing refractive corneal surgical procedure for the correction of myopia. We report here the results of a retrospective study of in situ keratomileusis with the refractive cut made with a microkeratome. The technique represents an intermediate stage of development that used a sutured corneal disc, an early automated microkeratome, and no reoperations for residual refractive error.

METHODS

We carried out a retrospective chart review of the first 107 consecutive eyes (73 patients) that received in situ keratomileusis with an automated microkeratome (Ruiz corneal shaper) at the El Maghraby Hospital in Jeddah, Saudi Arabia between November, 1991 and February, 1993. Sixty-three eyes (59%) were followed for a mean of 1 year. Manifest refraction measured by an ophthalmologist or optometrist was the major response variable. Surgery followed the Ruiz nomogram, which specified an anterior corneal disc approximately 7.2 mm in diameter and 160 microns in thickness and a plano in situ refractive cut a mean of 4.2 mm in diameter and 93 microns in thickness.

RESULTS

The mean baseline spherical equivalent of the manifest refraction was -11.97 +/- 5.30 diopters (D) (range, -3.75 to -28.00 D). At a mean of 1 year after surgery, the mean refraction was -1.86 +/- 3.13 D (range, -13.25 to +4.63 D); 13 eyes (21%) had a refraction within +/- 0.50 D and 22 (35%) within +/- 1.00 D. Undercorrection of more than -1.00 D was present in 36 eyes (57%). At baseline, 48 of 63 eyes (75%) could see 20/40 or better with spectacle correction. At 1 year, 13 of 63 eyes (21%) could see 20/40 or better uncorrected. To measure the stability of refraction in 61 eyes, the mean refraction at 1 month of +0.62 +/- 2.43 D was compared to that at 1 year after surgery (mean, -1.41 +/- 3.10 D), indicating a loss of effect in the direction of increasing myopia. Nine eyes (14%) lost two to five lines of spectacle-corrected visual acuity. Two eyes had central epithelial implantation plaques in the lamellar bed that required removal.

CONCLUSION

In situ keratomileusis using an automated corneal shaper and sutured corneal discs at an intermediate stage of development produced less than desirable refractive and visual acuity results.

Posterior amorphous corneal dysgenesis

PURPOSE

Posterior amorphous corneal dysgenesis is a rare disorder previously described in only four families. We expanded the spectrum of findings and updated the classification by adding seven additional cases.

METHODS

Three index cases were identified during ophthalmic examination at the El Maghraby Eye Hospital and Eye Center in Jeddah, Saudi Arabia. We examined all available members of three families of different ethnic origin (Saudi Arabian, Egyptian, and Indian) and found seven cases of affected patients. Videokeratography and slit-lamp photomicrography were done in selected cases.

RESULTS

In all seven cases, the corneas showed bilateral, diffuse, sheetlike opacities in the posterior stroma, with extension to the corneoscleral limbus, and corneal thinning in the more severely affected eyes. The clinical findings included variations in corneal thickness noted by slit-lamp microscopy and ultrasonic pachymetry, cornea plana, marked corneal astigmatism, and progressive ectasia of the cornea.

CONCLUSIONS

Posterior amorphous corneal dysgenesis is characterized by gray sheetlike opacities in the posterior stroma. It occurs in many ethnic groups and exhibits a varied spectrum of clinical findings, including iridocorneal adhesions and cornea plana. We think the anatomic abnormalities of the cornea warrant classification as a corneal dysgenesis rather than as a dystrophy. Longitudinal studies of individual eyes and investigation of associated abnormalities in other pedigrees may help resolve this distinction.

Climatic proteoglycan stromal keratopathy, a new corneal degeneration

PURPOSE

To characterize a previously undescribed corneal disorder, climatic proteoglycan stromal keratopathy.

METHODS

We prospectively characterized the disorder in 58 eyes of 29 patients (ages 41 to 84 years) at the El Maghraby Eye Hospital, Jeddah Saudi Arabia. Light and transmission electron microscopy were performed on six corneal specimens.

RESULTS

Clinical criteria for the diagnosis included a central, horizontally oval, corneal stromal haze with a ground glass appearance, a uniform or lamellar pattern, greater extent anteriorly and involvement of 50% to 100% of stromal thickness. It occurred bilaterally but sometimes asymmetrically. Density varied from mild to moderate and seldom decreased visual acuity. Sixteen (28%) of 58 corneas had additional degenerative lesions (spheroidal degeneration, mild calcific band keratopathy, and Salzmann's nodular degeneration). Refractile stromal lines or posterior white dots were present in six (10%) of 58 eyes. Videokeratography in 11 (29%) of 38 eyes demonstrated flat areas that overlay the stromal haze. Pathologic analysis demonstrated focal intracellular and extracellular deposits of excess proteoglycans. One specimen showed amyloid. We postulate that climatic factors play a pathogenic role because the disorder occurs in individuals who were exposed to the sunny, dry, dusty environment of the Middle East and because other corneal degenerative disorders were present concomitantly.

CONCLUSIONS

Climatic proteoglycan stromal keratopathy is a corneal degeneration that appears as an oval, central, gray, ground-glass haze associated with central corneal flattening on videokeratography and as excess proteoglycans on histologic examination. It seldom severely decreases visual function.

Regional Variation in Corneal Topography and Wound Healing Following Photorefractive Keratectomy

BACKGROUND

After excimer laser photorefractive keratectomy, corneal epithelial and anterior stromal wound healing may produce corneal haze and variability in refractive results among patients and eyes.

METHODS

We report a retrospective study of 17 selected eyes that received excimer laser photorefractive keratectomy with one of three brands of laser and that exhibited regional variations in corneal wound healing as observed with slit-lamp microscopy and videokeratography (Tomey TMS) within the ablation zone.

RESULTS

All 17 eyes were selected to show that the clear areas in the ablation zone corresponded with flat zones on the videokeratographs and the areas of subepithelial haze corresponded with steeper zones. Spectacle-corrected visual acuity was measured in 12 or the 17 eyes, and was 20/20 or better in 58% and 20/30 or better in 100%, indicating that the regional variation did not severely degrade Snellen visual acuity. Further studies are needed to determine how often regional variability occurs and to better define the relationship of corneal haze and corneal curvature.

CONCLUSION

Regional variations in corneal topography and haze can occur within the ablation zone in an individual cornea after photorefractive keratectomy.

[A study on stretching capacity of continuous circular capsulorhexis and nucleus delivery]

The stretching capacity of continuous circular capsulorhexis (CCC) in 20 human cadaver eyes was determined. The increases in circumference of the tear opening ranged from 164. 5% to 190.9% and that in area of the opening ranged from 235.2% to 364.6%. If a proper technique of capsulorhexis is adopted, the nucleus of 7-9.5 mm in diameter and 3-4.5mm in thickness can be delivered through a CCC opening of 4-6mm in diameter by hydrodissection and hydroexpression of nucleus without capsular tear.