Sandra C. Belmont

Excmier Laser Keratectomy for Astigmatism Occurring after Penetrating Keratoplasty

Purpose: To review the results of photorefractive keratectomy used to treat astigmatism occurring after penetrating keratoplasty. Methods: Seven patients who had undergone corneal transplantation previously and had significant postoperative astigmatism were included. All these patients were intolerant of spectacle and contact lens correction. Excimer laser keratectomy was performed to reduce the astigmatic error. Minimum follow-up of 12 months was necessary for study inclusion. Results: The average refractive cylinder decreased from 5.32 diopters (D) preoperatively to 2.79 D postoperatively. The refractive cylinder was reduced in six of the seven eyes attempted. The average preoperative keratometric cylinder decreased from 5.54 D (range, 1.50–10.00 D) to 4.00 D (range, 1.00–7.50 D) postoperatively. The best spectacle-corrected visual acuity was unchanged (within 1 line) in three eyes, improved in two, and decreased in two. The complications included a loss of at least two lines in spectacle-corrected visual acuity in two eyes and scarring in one. Conclusions: Excimer laser keratectomy can reduce the astigmatism after penetrating keratoplasty. The excellent results in some eyes offer promise for this technique in the future.

Very High Frequency Ultrasound Analysis of a New Phakic Posterior Chamber Intraocular Lens In Situ

PURPOSE To use very high frequency ultrasound scanning for in situ analysis of a new phakic posterior chamber intraocular lens (No-Touch; International Visions Inc, Cincinnati, Ohio). METHODS In this pilot study, very high frequency ultrasound (50 MHz) wide-angle (15 mm) full anterior segment scans were obtained in two patients who had undergone phakic posterior chamber intraocular lens implantation into legally blind eyes with normal anterior segment anatomy. RESULTS Very high frequency ultrasound B-scan images delineated the phakic posterior chamber intraocular lens within the posterior chamber. The relations to the sulci were clearly imaged. Anatomic relations of the phakic posterior chamber intraocular lens optic and haptics were visualized in both static (light/dark) and kinetic (distance/accommodative) states. CONCLUSION Very high frequency ultrasound wide-angle scanning provides a unique tool to noninvasively evaluate the eye preoperatively and the static and kinetic relations of this new refractive device within the posterior chamber.

Combined Wedge Resection and Relaxing Incisions for Astigmatism After Penetrating Keratoplasty

BACKGROUND Videokeratography may provide information for surgical correction of astigmatism after penetrating keratoplasty. We used a combination of wedge resection and relaxing incisions to treat high refractive astigmatism after penetrating keratoplasty. METHODS Videokeratography using the normalized scale of the Topographic Modeling System was used as a guide in determining the location and the length of incisions and resections. Nine eyes were treated with both relaxing incisions and a wedge resection. All patients had more than 3.00 diopters (D) of refractive astigmatism. All patients were intolerant of spectacles or contact lenses. The depth of the corneal relaxing incisions was constant at 0.5 mm and the width of the corneal wedge resections was constant at 0.75 mm. RESULTS The relaxing incisions produced flattening of the steeper meridian and the wedge resection produced steepening of the flatter meridian. The average preoperative keratometric astigmatism was 7.44 D (range, 3.50 to 11.00 D) and the average refractive astigmatism was 5.56 D (range, 4.00 to 8.00 D). The average preoperative spherical equivalent was 0.08 D (range, -7.00 to 4.25 D). Postoperatively, the average keratometric astigmatism was 2.97 D (range, 1.00 to 5.00 D) and the average refractive astigmatism was 2.58 D (range, 0.00 to 5.00 D). The average postoperative spherical equivalent refraction was -0.32 D. CONCLUSIONS Combined corneal wedge resection and relaxing incisions appears to be effective in reducing high refractive astigmatism following corneal transplantation.

High frequency ultrasound evaluation of radial keratotomy incisions

Abstract Radial keratotomy is a surgical procedure to correct myopia that involves placing corneal incisions of precise partial thickness to induce flattening. It has yielded positive but sometimes unpredictable results. Many surgical variables influence the final result. Among them, incision depth is probably the most difficult to control and evaluate. In this study, we used very high frequency (50 MHz) ultrasound (HFU) to image radial keratotomy incisions in post‐radial keratotomy human corneas to obtain high definition images of the cornea. The images allowed us to measure the depth of incisions as a percentage of corneal thickness.

Very high-frequency ultrasound analysis of non-contact holmium laser thermal keratoplasty treatment spots.

PURPOSE To objectively measure the corneal treatment spots in vivo using very high-frequency ultrasound (VHFU) after non-contact laser thermal keratoplasty (LTK) to better understand the variability and regression of refractive outcomes. METHODS In an institutional setting, VHFU was performed on 128 spots (8 eyes of 4 patients) using an immersion scanning technique 1 to 2 years after LTK with a single element focused transducer (50 MHz arc scanning ultrasound). Biometric techniques were used to evaluate the treatment spot depth, corresponding corneal thickness, and spot profile between patients, eyes (left/right), and by location on the cornea. The identical technique was used in a rabbit immediately after LTK to compare ultrasound versus histologic findings. RESULTS The mean treatment spot penetration depth ranged between 0.373 and 0.533 mm, representing 64% to 78% of the corneal thickness compared to previous reports of 80% to 90%. Treatment spot depth, the corresponding corneal thickness, and percentage of overall cornea penetrated differed significantly across patients. Treatment spot depth was not significantly related to the level of applied laser energy (230 to 258 mJ) (0.082 Pearson sign). Spot profiles were not uniformly cone-shaped; W- and wedge-shaped were also identified. Ultrasound findings in the rabbit were similar to histology results and confirmed evidence of epithelial remodeling. CONCLUSIONS Very high-frequency ultrasound of 128 treatment spots after non-contact LTK demonstrates epithelial remodeling and inconsistencies in penetration depth and profile.

A COMPARISON OF ASTIGMATISM AFTER PENETRATING KERATOPLASTY USING THREE SUCTION TREPHINATION TECHNIQUES

records. Keratometric data after final suture removal at up to 18 months were available for 66 cases in Group 1 and 66 cases in Group 2. Results: Average final keratometry values were 46.80 ± 2.19 D (mean ± SD) for Group 1 and 46.75 ± 2.34 D for Group 2 (p = 0.89). Median keratometric astigmatism was 4.87 ± 3.71 D for Group 1 and 4.00 ± 3.04 D for Group 2 (p = 0.44). Final average keratometry values had increased from preoperative values by 3.30 ± 2.39 D, with no significant difference between the trephine systems (p = 0.69). There was a low correlation between final average keratometry values and preoperative values (r = 0.28, p = 0.007) and with donor age (r = -0.13, p = 0.14). There was no significant difference in final keratometry values with the use of different corneal storage media. Conclusions: There was no statistically significant difference in keratometric results using these two methods of corneal trephination with a standard suture technique. Final keratometry values did not appear to be influenced by donor age or corneal storage media and are poorly correlated with preoperative values. Supported by EY 02037, EY 10255, and Research to Prevent Blindness, Inc.