Enhancement outcomes after photorefractive keratectomy and laser in situ keratomileusis using topographically guided excimer laser photoablation

Main Complications of Photorefractive Keratectomy and their Management

Photorefractive keratectomy (PRK) was the first surface ablation procedure introduced for the treatment of refractive errors and has been proven to be effective and safe. In some cases, however, the patient may not be totally satisfied with the final result and retreatment may be necessary. We performed a literature review to describe the main conditions that may arise following PRK that may require retreatment and new promising techniques to allow customized and effective treatments for patients. There is currently no gold standard for retreatment of residual refractive error after PRK. The surgeon must take into account the patient's history and type of problem when choosing the most appropriate technique. LASIK and PRK are the main options. Haze can be treated with good results with phototherapeutic keratectomy and mytomicin C. High order aberrations and decentration may be addressed with topographically-guided excimer photoablation or with wavefront-guided PRK.

Risk factors of regression and undercorrection in photorefractive keratectomy: a case-control study

AIM

To determine risk factors of regression and undercorrection following photorefractive keratectomy (PRK) in myopia or myopic astigmatism.

METHODS

A case-control study was designed in which eyes with an indication for re-treatment (RT) were defined as cases; primary criteria for RT indication, as assessed at least 9mo postoperatively, included an uncorrected distance visual acuity (UDVA) of 20/30 or worse and a stable refraction for more than 3mo. Additional considerations included optical quality symptoms and significant higher order aberrations (HOAs). Controls were chosen from the same cohort of operated eyes which had complete post-operative follow up data beyond 9mo and did not need RT. The cohort included patients who had undergone PRK by the Tissue-Saving (TS) ablation profile of Technolas 217z100 excimer laser (Bausch & Lomb, Rochester, NY, USA). Mitomycin C had been used in all of the primary procedures.

RESULTS

We had 70 case eyes and 158 control eyes, and they were comparable in terms of age, sex and follow-up time (P values: 0.58, 1.00 and 0.89, respectively). Pre-operative spherical equivalent of more than -5.00 diopter (D), intended optical zone (OZ) diameter of less than 6.00 mm and ocular fixation instability during laser ablation were associated with RT indications (all P values <0.001). These factors maintained their significance in the multiple logistic regression model with odd ratios of 6.12, 6.71 and 7.89, respectively.

CONCLUSION

Higher refractive correction (>-5.00 D), smaller OZ (<6.00 mm) and unstable fixation during laser ablation of PRK for myopia and myopic astigmatism were found to be strong predictors of undercorrection and regression.

Changes in wave-front aberrations after rigid gas permeable contact lens fitting in post-laser in situ keratomileusis patients with visual complaints

OBJECTIVE

To evaluate the effect of rigid gas permeable (RGP) contact lenses in reducing wave-front aberrations in post-laser in situ keratomileusis (LASIK) myopic patients.

DESIGN

Cross-sectional study.

PARTICIPANTS

Thirty patients with visual complaints after conventional LASIK procedure for correcting myopia.

METHODS

The 30 patients were fitted with RGP contact lenses. Wave-front measurements were taken before and after RGP contact lens wearing.

RESULTS

Compared with bare eye examinations, root mean-square values of higher-order aberrations (HOAs) significantly decreased with RGP contact lens use. Among these, spherical aberration decreased from 0.507 (SD 0.304) microm to 0.164 (SD 0.121) microm (t = 7.186, p < 0.001); coma decreased from 0.470 (SD 0.312) microm to 0.165 (SD 0.090) microm (t = 5.566, p < 0.001); secondary coma decreased from 0.079 (SD 0.050) microm to 0.044 (SD 0.027) m (t = 4.118, p < 0.001); and total HOAs decreased from 0.782 (SD 0.449) microm to 0.307 (SD 0.140) microm (t = 6.710, p < 0.001).

CONCLUSIONS

Fitting RGP contact lenses effectively decreased HOAs induced by conventional myopic LASIK surgery. Possible reasons may be the elimination of irregularity and dissymmetry on the corneal anterior surface, relief of the aspherical extent of the central corneal surface, and enlargement of the effective optical zone.

Reverse geometry rigid gas permeable contact lens wear reduces high-order aberrations and the associated symptoms in post-LASIK patients

PURPOSE

This study evaluated the efficacy of custom-made reverse geometry rigid gas permeable (RGP) contact lenses in the control of symptoms related to increased wavefront aberrations after LASIK correction of myopia.

MATERIALS AND METHODS

Twenty-eight myopes treated with LASIK were assessed for post-LASIK symptoms (declined night vision, glare, halos and/or monocular diplopia) and corneal topography. A set of RGP contact lenses was selected as trial lenses based on the matching between the lens and the patient's corneal topography. If the fluorescein pattern between the trial lens and the corneal surface showed a central alignment, a mid-peripheral bearing and peripheral clearance and if the patient felt comfortable with the lens wear, a duplicated lens was ordered for the patient. Otherwise, a lens satisfied with corneal topography of the patient and clinical judgment was used. Visual acuity (VA) and wavefront aberrations were measured after the lens wear.

RESULTS

The custom-made lenses well matched the host cornea with no dislodgment in all subjects. The post-LASIK eyes showed an increase of 1 Snellen line in VA (from 0.90 +/- 0.33 to 1.11 +/- 0.24) and a significant improvement in all symptoms after the lens wear. The total higher-order aberration is significantly reduced after the lens wear with at least 70% reduction in either spherical aberration, coma, third or fourth aberration but only 33% reduction in the fifth aberration.

CONCLUSIONS

Reverse geometry RGP lenses with the design based on individual topographic data can improve visual performance of post-LASIK eyes by reducing higher order aberrations.

Comparison between three- and six-month postoperative refractive and visual results after laser epithelial keratomileusis with mitomycin C

PURPOSE

To compare the residual refraction and visual results between the three- and six-month postoperative visits to detect the optimal moment for enhancement after myopic laser epithelial keratomileusis (LASEK) with mitomycin C (MMC).

DESIGN

Nonrandomized, interventional, prospective study.

METHODS

One hundred and forty-one consecutive eyes that underwent LASEK with MMC to correct their myopia using the Esiris excimer laser (Schwind Eye Tech Solutions, Kleinostheim, Germany), and that showed three months postoperatively a residual defect or a suboptimal uncorrected visual acuity (UCVA) or best spectacle-corrected visual acuity (BSCVA) were included in the study. We compared the residual spherical refraction and cylinder, the UCVA, and the BSCVA between the three- and six-month postoperative examinations.

RESULTS

Preoperative spherical refraction was -5.2 +/- 2.90 diopters (D). Preoperative cylinder was -1.66 +/- 1.20 D. The residual sphere was +0.43 +/- 0.90 D three months and +0.21 +/- 0.90 D six months after surgery (P = .0001). The cylinder was -0.71 +/- 0.60 D and -0.67 +/- 0.60 D, respectively (P = .4). The UCVA was 0.75 +/- 0.2 and 0.81 +/- 0.2 (P = .0001) and the BSCVA was 0.94 +/- 0.1 and 1.01 +/- 0.1 (P = .0001), respectively. Those patients with a myopic defect (sphere or cylinder) three months postoperatively did not show any significant change in UCVA or refractive defect six months after surgery, while those with a hyperopic defect (sphere or cylinder) showed an improvement in UCVA and residual refraction six months postoperatively (P < .05).

CONCLUSIONS

Our results suggest that retreatment after myopic LASEK with MMC may be performed three months after surgery when the residual refraction is myopic, but it seems wise to wait at least six months after surgery when the residual refraction is hyperopic.