Corneal Wedge Excision in the Treatment of High Astigmatism After Penetrating Keratoplasty

PURPOSE

To report 5 cases of high astigmatism after penetrating keratoplasty (PK) treated with corneal wedge excisions.

METHODS

We report our experience of 5 patients treated with corneal wedge excisions for high astigmatism after PK. A thin sliver of cornea measuring between 0.1 and 0.2 mm in thickness was excised from just inside the graft-recipient interface. The length of the incision centered at the axis of the flatter meridian of the cornea and was extended over a range of 60-90 degrees. The wound was closed with interrupted 10-0 nylon sutures placed every 15 degrees. We also report, for the first time, both pre- and postoperative corneal topography in 3 of our patients who underwent wedge excisions.

RESULTS

The mean preoperative astigmatism was 15.2 D (range, 8.5-29.1 D). Postoperatively, after wedge excision, the mean astigmatism was reduced to 2.3 D (range, 1.9-3.7 D). The mean reduction in astigmatism was 12.9 D (range, 6.3-25.4 D).

CONCLUSIONS

Corneal wedge resection is an effective treatment for high astigmatism after PK. It may prove particularly useful in cases of high astigmatism or where other treatments are not appropriate. We believe that there is still a role for wedge resection as one of many tools to be used in the treatment of high post-PK astigmatism.

Corneal Topography, Arcuate Keratotomy, and Compression Sutures for Astigmatism After Penetrating Keratoplasty

BACKGROUND

Twenty (20) patients with post-penetrating keratoplasty (PKP) (21 eyes) and excessive corneal astigmatism were studied using corneal topography to determine placement of arcuate incisions and compression sutures for astigmatism reduction.

METHODS

Keratoplasty wounds and compression sutures were placed asymmetrically based on corneal topography only. Incisions were at the donor-host junction at a depth of 500 microns.

RESULTS

A 56% reduction in corneal astigmatism was accomplished with an average cylinder reduction of 5.3 D. Keratometry readings were reduced in 18 of 20 (90%) of eyes and refractive cylinder was reduced in 15 of 20 (75%) of eyes. Corrected visual acuity improved in 15 of 20 (75%) declined in 15%, and did not change in 10%.

CONCLUSION

Visual acuity can be improved by manipulating the astigmatism after penetrating keratoplasty using corneal topography maps to determine placement of arcuate incisions and compression sutures.

Dynamic shifts in corneal topography after radial and transverse keratotomy

PURPOSE

The authors aimed to quantitate the dynamic patterns of change in corneal topography after multistaged radial and transverse keratotomy using digitized video-keratography.

METHODS

Single and paired radial and transverse keratotomies, with videokeratoscopy between each stage and at the end of the procedure, were performed on fresh animal cadaver eyes using an artificial orbit system.

RESULTS

All incisions led to central flattening. A single radial keratotomy caused flattening adjacent to the incision, and steepening 180 degrees away. A paired radial keratotomy caused increased flattening in the meridian of the incisions, and less flattening 90 degrees away. A single transverse incision caused steepening adjacent to the incision and diffuse flattening elsewhere. A paired transverse incision caused flattening near the optical center along the meridian bisecting the incisions and steepening 90 degrees away.

CONCLUSION

The authors have demonstrated that computerized videokeratography can be used successfully to systematically quantitate dioptric shifts in multiple hemimeridians and measurement zone diameters after refractive surgery.

Corneal topography of transverse keratotomies for astigmatism after penetrating keratoplasty

We used a topography system to evaluate retrospectively the pattern of power distribution seen preoperatively and postoperatively in six patients with high postkeratoplasty astigmatism. The relaxing incisions had all been placed based on visual inspection of keratoscope mires alone. Computer analysis of keratoscope photographs showed considerable individual variation in the degree of surface irregularity in preoperative topography. Our data suggest that the steep axis of the postkeratoplasty graft is better conceptualized as two steep hemimeridians. These hemimeridians were separated by an angle other than 180 degrees (two of six cases), and often showed fairly large changes in power from the most central to peripheral areas of the graft analyzed (three of six cases). Asymmetry of power between the two steep hemimeridians was seen in all cases. Areas of maximum steepening were often present in the peripheral portions of the graft in areas other than the major hemimeridians. Individual variation in preoperative corneal irregularity and asymmetry appeared to have an effect on the success of the relaxing incisions.

Wound healing after astigmatic keratotomy in human eyes

The authors analyzed three full-thickness corneal buttons and two corneal scleral rims obtained 5 1/2 to 44 months after three trapezoidal keratotomies (Ruiz), one "L," and one "TL" procedure. The indications for the penetrating keratoplasty were photophobia, corneal edema, and loss of best-corrected vision after the astigmatic keratotomy procedures. Epithelial plugs were seen in all five specimens. Complete basal lamina lined the wounds in two cases. Tangential incisions of the Ruiz procedure were shallower and demonstrated more advanced wound healing than the corresponding semiradial incisions. Two of the three Ruiz procedures demonstrated peripheral separation of the semiradial incisions. Wound healing events after astigmatic keratotomy procedures appear similar to those reported previously after standard radial keratotomy with the exception that tangential incisions appear to heal faster than the semiradial incisions.

Scleral flap surgery for modification of corneal astigmatism

We performed resections and recessions of scleral flaps on human cadaver eyes in order to measure the induced change in keratometric astigmatism. We prepared 3-mm scleral flaps that were 3, 5, 7, or 10 mm long and resected or recessed these flaps up to 1 mm in 0.25-mm increments. Scleral flap resection resulted in up to 10.1 D of net corneal steepening along the meridian of the incision. Scleral flap recessions resulted in up to 7.7 D of net corneal flattening along the meridian of the incision; the effect increased with increasing flap length in the recessed eyes. There was a tendency toward mean corneal flattening with resections and mean corneal steepening with recessions.

Postoperative astigmatism

With the numerous significant advances in surgical methodology--e.g., microinstrumentation, the operating microscope, the surgical keratometer, and intraocular lenses--that have been developed over the past two decades, both surgeons and patients have become increasingly aware of the final optic result of any surgical intervention. This is especially so since the development of refractive surgery, where good uncorrected vision is frequently the final arbiter of success. We have progressed to the stage where the optic manipulation of the cornea, whether intentional or otherwise, can be understood in terms of a number of variables. These include the preparation and closure of the surgical wound, the choice of suture material, and both intraoperative and postoperative manipulations. Where these have failed and postoperative astigmatism still occurs, a number of surgical procedures are available to reduce the astigmatic error to an acceptable level.