Intraoperative biometry for intraocular lens (IOL) power calculation at silicone oil removal

PURPOSE

Cataract development is common following retinal detachment surgery that necessitates silicone oil injection. Intraocular lens (IOL) power calculation in the presence of silicone oil is challenging for many reasons. The authors evaluated the accuracy of intraoperative biometry during cataract surgery in silicone-filled eyes.

METHODS

Twelve cases of cataract in eyes filled with silicone oil after retinal detachment surgery were included. Preoperatively, keratometric readings were documented. Intraoperative axial length was measured following removal of silicone oil using a sterile probe of the Nidek Echoscan US800 unit. IOL power calculation was computed using the SRK/T formula. This was followed by phacoemulsification and foldable lens implantation. Postoperative refraction allowed evaluation of the accuracy of intraoperative biometry. The predictability of three different formulas was also compared (Holladay, SRK/T, and SRK II).

RESULTS

Seven men and five women with a mean age of 50.2 years were included in the study. The mean postoperative spherical equivalent using the described technique was 6.77 +/- 0.43 diopters. SRK/T and Holladay formula had the best predictability for high axial length eyes, whereas the three studied formulas showed no significant differences in predictability in eyes with normal axial length.

CONCLUSIONS

Intraoperative biometry proved to have good predictability for the absolute postoperative refractive error in cataract surgery for eyes at the time of silicone oil removal. This predictability was accurate independent of axial length.

Phototherapeutic Keratectomy in Patients With Recurrent Corneal Epithelial Erosions

PURPOSE

To evaluate the outcome of phototherapeutic keratectomy (PTK) in the management of recurrent corneal erosions, refractory to other forms of treatment.

METHODS

Phototherapeutic keratectomy was performed on 43 eyes of 41 patients with recurrent corneal erosions. The corneal epithelium was debrided, and laser ablation was performed to a depth of 6 microm with an ablation zone of 7 to 9 mm, using the Technolas Keracor 117C PlanoScan excimer laser. Follow-up time was 12 to 48 months (mean, 23.3+/-9.1 mo).

RESULTS

After PTK, patients were free of symptoms in 31 eyes (72.1%), and eight eyes (18.6%) had occasional mild symptoms of irritation and photophobia upon awakening. Recurrence of painful corneal erosions occurred in four eyes (9.3%). After PTK retreatment, these patients did not report any further episodes and were free of symptoms for 12 to 30 months (mean, 21.0+/-7.7 mo). The mean spherical equivalent manifest refraction was changed by +0.15+/-0.39 D in the hyperopic direction at 1 year after PTK. Thirty-three eyes (76.7%) were within +/-1 line of preoperative best spectacle-corrected visual acuity (BSCVA). BSCVA was improved by two or more lines in 10 eyes (23.3%). There were no significant complications.

CONCLUSION

Excimer laser PTK with the Technolas Keracor 117C excimer laser was a safe and effective procedure for the treatment of recurrent corneal erosions. Excimer laser PTK can also be useful in improving the visual acuity in these patients. A small percentage of patients may require a second PTK to prevent further episodes of corneal erosions.

Changes in Intraocular Pressure After Laser in situ Keratomileusis

PURPOSE

To evaluate changes in intraocular pressure (IOP) measurements by Goldmann applanation tonometry after laser in situ keratomileusis (LASIK) for myopia and myopic astigmatism, and to assess the accuracy of Goldmann applanation tonometry measurements after LASIK in these eyes.

METHODS

LASIK was performed on 166 eyes of 93 patients for correction of myopia and myopic astigmatism. Intraocular pressure was measured by Goldmann applanation tonometry at the central and temporal parts of the cornea before and at 1, 3, 6, and 12 months after LASIK. The amount of change in IOP was computed and its relation to different variables was evaluated by regression analysis.

RESULTS

Intraocular pressure measured at the center of the cornea was reduced by a mean of 3.69 +/- 1.63 mmHg after LASIK. Multiple regression analysis showed that the decrease in IOP was related to the preoperative IOP and the change in central corneal thickness after LASIK. Measurements of IOP at the temporal part of the cornea were also reduced by a mean of 2.39 +/- 1.71 mmHg. There was wide variability in the amount of difference between the temporal and central measurements after LASIK (temporal measurements were higher than central by 0 to +4 mmHg).

CONCLUSION

LASIK for myopia produced underestimation of IOP measured by Goldmann applanation tonometry at the central part of the cornea by a mean of 3.69 +/- 1.63 mmHg. The decrease of IOP was related to preoperative IOP and the change in central corneal thickness after LASIK. Temporal Goldmann applanation tonometry measurements, although decreased after LASIK, were less reliable.

Laser in situ Keratomileusis for the Correction of Hyperopia From +1.25 to +5.00 Diopters With the Technolas Keracor 117C Laser

PURPOSE

To assess the efficacy, predictability, stability, and safety of laser in situ keratomileusis (LASIK) in patients with hyperopia and to evaluate the visual and refractive results of the procedure.

METHODS

LASIK was performed on 85 eyes of 53 patients for correction of hyperopia, with a preoperative mean manifest spherical equivalent refraction of +3.31 +/- 0.69 D (range, +1.25 to +5.00 D) and mean refractive astigmatism of +0.91 +/- 1.06 D (range, 0 to +3.00 D). The Carriazo-Barraquer (Moria) manual microkeratome was used to create the corneal flap, and laser ablation was performed using the Technolas Keracor 117C excimer laser with an ablation zone diameter of 6.0 mm and a transition zone diameter to 9.0 mm. Follow-up was 12 months for all patients.

RESULTS

Refraction was stable by 3 months after surgery. At 1 year after LASIK, the mean manifest spherical equivalent refraction was +0.43 +/- 0.57 D (range, -1.25 to +2.00 D) and refractive astigmatism was reduced to a mean of 0.36 +/- 0.30 D (range, 0 to 1.00 D). Fifty-two eyes (61.2%) had a manifest spherical equivalent refraction within +/- 0.50 D of emmetropia, and 76 eyes (89.4%) were within +/- 1.00 D. Uncorrected visual acuity was 20/20 in 21 eyes (24.7%) and 20/40 or better in 79 eyes (92.9%). Spectacle-corrected visual acuity was reduced by two lines in one eye (1.2%) and improved by two lines in five eyes (5.9%). There were no significant complications.

CONCLUSION

LASIK was an effective, safe, and predictable procedure for the correction of hyperopia up to +5.00 D and hyperopic astigmatism up to +3.00 D with the Technolas Keracor 117C excimer laser. The large size of the corneal flap obtained by the Carriazo-Barraquer (Moria) manual microkeratome facilitated laser ablation entirely in the exposed corneal stromal bed.

Laser in situ Keratomileusis for Correction of High Astigmatism After Penetrating Keratoplasty

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) for correction of high astigmatism after penetrating keratoplasty, and to assess the refractive results and predictability of the procedure.

METHODS

LASIK was performed on 19 patients (19 eyes) with high astigmatism after penetrating keratoplasty, using the Chiron Automated Corneal Shaper and the Chiron-Technolas Keracor 116 excimer laser. The amount of preoperative refractive astigmatism ranged from 6.50 to 14.50 D (mean, 9.21 +/- 1.95 D) and the spherical component of manifest refraction ranged from -7.00 to +1.25 D (mean, -2.14 +/- 2.11 D). All patients completed a minimum follow-up of 12 months.

RESULTS

Refraction was stable after 3 months. At 1 year after LASIK, the amount of refractive astigmatism was reduced to a mean of 1.09 +/- 0.33 D (range, 0.50 to 1.75 D), with 57.9% of the eyes within +/- 1.00 D of refractive astigmatism. The mean percent reduction of astigmatism was 87.9 +/- 3.7%. The postoperative spherical component of manifest refraction ranged from -1.00 to +1.75 D with a mean of +0.43 +/- 0.82 D. Vector analysis showed that the mean amount of axis deviation was 1.1 +/- 1.3 degrees and the mean percent correction of preoperative astigmatism was 92.6 +/- 8.4%. There were no intraoperative complications. Spectacle-corrected visual acuity was not reduced in any eye, and improved by 2 or more lines in 42.1% of eyes after LASIK.

CONCLUSION

LASIK with the Chiron-Technolas Keracor 116 excimer laser was effective for correction of both astigmatism and myopia after penetrating keratoplasty. The procedure proved to be safe and gave fairly predictable and stable refractive results.

Laser in situ Keratomileusis Retreatment for Residual Myopia and Astigmatism

PURPOSE

To evaluate the visual and refractive results of laser in situ keratomileusis (LASIK) retreatment on eyes with residual myopia with or without astigmatism.

METHODS

LASIK retreatment was performed on 35 eyes of 23 patients for correction of residual myopia, with or without astigmatism, with a mean manifest spherical equivalent refraction of -2.17+/-0.82 D (range, -1.00 to -3.87 D) and mean refractive astigmatism of -0.55+/-0.61 D (range, 0 to -1.75 D). Retreatment was performed 3 to 18 months after primary LASIK (mean, 5.1+/-2.6 mo). The corneal flap of the previous LASIK was lifted and laser ablation was performed using the Chiron-Technolas Keracor 116 excimer laser. Follow-up was 12 months for all eyes.

RESULTS

At 1 year after retreatment, manifest spherical equivalent refraction was reduced to a mean -0.23+/-0.28 D (range, 0 to -0.87 D), and refractive astigmatism was reduced to a mean -0.16+/-0.25 D (range, 0 to -0.75 D). Thirty-two eyes (91.5%) had a manifest spherical equivalent refraction within +/-0.50 D of emmetropia, and 33 eyes (94.3%) had 0 to 0.50 D of refractive astigmatism. Uncorrected visual acuity was 20/20 or better in 11 eyes (31.4%). Spectacle-corrected visual acuity was not reduced in any eye after retreatment. There were no significant complications.

CONCLUSION

LASIK retreatment was effective for correction of residual myopia or astigmatism after primary LASIK. Refractive results were predictable with good stability after 3 months. Lifting the flap during LASIK retreatment was relatively easy to perform and did not result in visual morbidity in eyes treated from 3 up to 18 months after primary LASIK.

Laser in situ keratomileusis for myopic astigmatism

PURPOSE

To evaluate the refractive results of laser in situ keratomileusis (LASIK) for myopic astigmatic eyes, and to assess the efficacy, accuracy, stability, and safety of the procedure.

METHODS

LASIK was performed on 113 eyes of 73 patients for correction of myopic astigmatism ranging from 1.00 to 5.00 D, as measured by manifest refraction, with a mean baseline refractive astigmatism of 2.09 +/- 1.12 D. The Chiron Automated Corneal Shaper was used to create a corneal flap, and laser ablation was performed using the Chiron-Technolas Keracor 116 excimer laser. Follow-up time was 12 months for all eyes.

RESULTS

Refractive astigmatism was stable by 3 months after surgery. At 1 year after LASIK, refractive astigmatism was reduced to a mean of 0.25 +/- 0.31 D (range 0 to 1.00 D). Sixty-one eyes (54%) had no residual astigmatism and 98 eyes (86.7%) had 0 to 0.50 D of refractive astigmatism. The mean percent reduction of preoperative astigmatism was 87.9 +/- 14.9%. The mean axis deviation of the surgically induced astigmatism was 2.1 +/- 3.1 degrees, with 96 eyes (84.9%) within 5 degrees of the desired axis. The percent correction of preoperative astigmatism in the proper axis was 97.1 +/- 15.5%. Spectacle-corrected visual acuity improved by 2 lines in 11 eyes (9.7%), and was reduced by 1 line only in 1 eye. There were no other significant complications.

CONCLUSION

LASIK with the Chiron-Technolas Keracor 116 excimer laser was effective for correction of myopic astigmatism, with good stability after 3 months. The results were predictable with an acceptable degree of accuracy. LASIK is a safe procedure with very few complications.

Laser in situ keratomileusis for myopic anisometropia in children

PURPOSE

To evaluate the visual and refractive results of laser in situ keratomileusis (LASIK) in pediatric patients with myopic anisometropia and amblyopia, and to assess the predictability, safety, and efficacy of the procedure in children.

METHODS

Fourteen patients aged 7 to 12 years with myopic anisometropia and amblyopia had LASIK in the more myopic eye (14 eyes) using the Chiron Automatic Corneal Shaper and the Chiron-Technolas Keracor 116 excimer laser. Preoperative spherical equivalent manifest refraction ranged from -4.62 to -12.50 D (mean, -7.87 D) and spectacle-corrected visual acuity ranged from 20/40 to 20/100 (median, 20/50). All patients completed a minimum follow-up of 12 months.

RESULTS

One year after LASIK, spherical equivalent manifest refraction ranged from 0 to -1.50 D (mean, -0.55 D). Spectacle-corrected visual acuity improved in all eyes (range, 20/20 to 20/40; median, 20/25). Six eyes (42.9%) had a postoperative spectacle-corrected visual acuity of 20/20. Uncorrected visual acuity was 20/40 or better in 10 eyes (71.4%) (range, 20/20 to 20/70; median, 20/30). Uncorrected visual acuity exceeded preoperative spectacle-corrected visual acuity in all eyes by an average of 2 lines. There were no significant complications.

CONCLUSION

LASIK was effective for correction of myopic anisometropia in this small group of children and reversed refractive amblyopia. LASIK in these children was safe, predictable, and provided good visual results.