Response of the Cornea for up to Four Years After Photorefractive Keratectomy for Myopia

Inverted lens provides reverse geometry solution for post laser vision correction (LVC) corneas

Many patients require optical correction post-laser vision correction (LVC). While mildly irregular corneal topographic patterns or asymmetry can sometimes be treated with conventional soft lenses, often this proves inadequate. This article introduces a novel technique to provide visual improvement and comfort for these patients. An inverted senofilcon A (Acuvue Oasys®, Johnson & Johnson Vision Care) lens (off-label)was inserted on a patient's eyes that reported discomfort with his current soft contact lenses, which provided improved centration as was seen with a slit lamp and high molecular fluorescein through a yellow filter. The patient achieved a visual acuity of 6/6+ in each eye and reported that the vision did not fluctuate. The post-lens tear film decreased to 35micron versus 43micron in the conventional position, as shown in OCT. The patient reported that he wore the lenses 9 hours a day. His Dry Eye Questionnaire-8 (CLDEQ-8) score decreased from 22 to 15 when wearing the lenses in the inverted position. This case demonstrates that post-laser vision correction patients with minimal asymmetric topography within the treated zone requiring refractive correction may be helped using an inverted conventional soft frequent replacement lens.

Toric intraocular lens versus monofocal intraocular lens implantation and photorefractive keratectomy: a randomized controlled trial

PURPOSE

To compare the outcomes of phacoemulsification with toric intraocular lens implantation vs phacoemulsification with monofocal intraocular lens implantation followed by photorefractive keratectomy (PRK) for correction of pre-existing astigmatism.

DESIGN

Randomized controlled trial, 6-month study.

METHODS

setting: Institutional.

STUDY POPULATION

Sixty eyes of 52 patients with age-related senile cataract and regular corneal astigmatism ranging from 1.50 to 3.00 diopters, enrolled and randomly allocated in 2 groups based on computer-generated random number table.

INTERVENTION

Group 1 patients underwent phacoemulsification with toric intraocular lens (IOL) implantation and Group 2 patients underwent phacoemulsification with monofocal IOL implantation followed by PRK 3 months later.

MAIN OUTCOME MEASURES

The main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual cylinder, contrast sensitivity, glare acuity, pain score, and higher-order aberrations.

RESULTS

At 6 months 53.3% of eyes in the toric IOL and 60% eyes in the monofocal IOL with PRK group attained UDVA of 20/20. Median residual refractive cylinder value was higher in the toric IOL group (toric IOL = -0.5, monofocal IOL with PRK = 0; P = .02). Mean root mean square value of total aberrations (5 mm pupil) was higher in monofocal IOL with PRK eyes (toric IOL= 1.02 ± 0.44, monofocal IOL with PRK = 1.28 ± 0.5; P = .04). Mean contrast sensitivity values were comparable. Mean toric IOL rotation was 1.3 ± 2.1 degrees. Mean glare acuity was better in toric IOL eyes (toric IOL = 0.46 ± 0.16, monofocal IOL with PRK = 0.73 ± 0.12; P < .001). Median postoperative pain scores were higher in monofocal IOL with PRK eyes.

CONCLUSION

PRK yields lesser residual cylinder compared to toric IOL. However, it causes greater postoperative pain and corneal aberrations, and poor glare acuity.

Evaluation of femtosecond laser clear corneal incision: an experimental study

PURPOSE

To evaluate the changes of corneal topography following femtosecond laser and manual clear corneal incision (CCI).

METHODS

Inflation testing was performed in 14 human eye globes to evaluate the topographic response of the cornea to CCIs. In seven samples (femtosecond laser group), a 2.75-mm three-plane CCI was created using the iFS femtosecond laser (Abbott Medical Optics, Inc., Santa Ana, CA); the remaining seven samples (control group) received a 2.75-mm manual CCI using disposable angled knives. Topographic maps of the anterior and posterior cornea were acquired using a Scheimpflug topographer Pentacam HR (Oculus Optikgeräte GmbH, Wetzlar, Germany). Keratometric data were used to analyze the curvature changes of the cornea. The changes of corneal astigmatism were analyzed by vector analysis.

RESULTS

After CCI, the mean change of the anterior keratometric power was 0.04 ± 0.39 and 0.05 ± 0.51 diopters (D) (analysis of variance, P > .05) in the femtosecond laser and control groups, respectively. The mean change (P > .05) of the posterior corneal keratometric power was 0.16 ± 0.19 and 0.15 ± 0.18 D, respectively. The average change of the anterior and posterior corneal astigmatism vector magnitude was 0.17 D or less in both groups (P > .05). A slight against-the-rule astigmatic change of the anterior and posterior corneal interfaces was found after both CCI techniques.

CONCLUSION

The 2.75-mm three-plane CCI created with femtosecond laser showed minimal changes of the anterior and posterior corneal topography, comparable with those of single-plane angled manual incision.

Long-term corneal wavefront aberration variations after photorefractive keratectomy for myopia and myopic astigmatism

PURPOSE

To analyze the higher-order corneal wavefront aberration during an 8-year follow-up after photorefractive keratectomy (PRK).

SETTING

IRCCS Fondazione G.B. Bietti, Rome, Italy.

DESIGN

Case series.

METHODS

Patients having PRK using the Technolas 217C excimer laser platform were divided into 3 groups according to the preoperative refraction as follows: low myopia, high myopia, and astigmatism. The preoperative and 1-, 4-, 6-, and 8-year postoperative root mean square (RMS) values of coma, spherical aberration, and total higher-order aberrations (HOAs) were calculated with 3.5 mm and 6.0 mm simulated pupils. The mean preoperative and postoperative higher-order corneal wavefront aberration maps, point-spread functions, and radial modulation transfer functions (MTFs) were represented to describe the impact of PRK on the optical quality of the anterior cornea.

RESULTS

The study enrolled 33 patients (66 eyes). Corneal spherical aberration was statistically significantly higher after PRK for simple myopia with 3.5 mm and 6.0 mm pupils (P<.05). The postoperative increase in coma was statistically significant in the high-myopia group with both pupil sizes (P<.05). Total RMS HOAs increased postoperatively with a 6.0 mm pupil in all groups (P<.05). The mean radial MTF was almost stable in all groups between preoperatively and postoperatively.

CONCLUSIONS

Higher-order corneal wavefront aberrations stabilized 1 year after PRK to treat myopia or myopic astigmatism. The effect of induced corneal HOAs tended to increase after correction of high myopia with large pupils, although without degrading the image optical quality of the cornea over the long term.

Investigation of corneal topography after deep lamellar endothelial keratoplasty

PURPOSE

To analyze the 6-month anterior and posterior topographic changes of the cornea after deep lamellar endothelial keratoplasty.

METHODS

Orbscan topographies of 22 eyes from 21 patients with corneal decompensation were retrospectively analyzed: 11 eyes received a 9-mm scleral access incision (large-incision group) and 11 eyes received a 5-mm scleral access incision (small-incision group). All the preoperative and postoperative corneal raw data were imported into custom software which computed the average composite corneal maps and difference maps for both study groups in order to evaluate the corneal response to the surgery. The software delineated 2 concentric zones of the cornea to characterize the regional response following the surgery: the central and peripheral regions.

RESULTS

There were no significant differences (analysis of variance, <0.35 D, p>0.05) between 6-month postoperative and preoperative average anterior central corneal topographies in either group. At the end of follow-up, the average posterior curvature tangential map did not significantly differ from before surgery in either group (<0.35 D, p>0.05). However, a significant increase (>0.60 D, p<0.01) in the average posterior central astigmatic power of the cornea was found in both groups.

CONCLUSIONS

Deep lamellar endothelial keratoplasty effectively preserves the preoperative keratometric corneal topography, minimizing changes in curvature and astigmatism of the cornea. The great predictability of corneal topography following deep lamellar endothelial keratoplasty is likely to be attributed to the minimal changes that occur in the anterior stroma, the portion of the cornea that appears to be mainly responsible for maintenance of corneal shape.

Long-term optical quality of the photoablated cornea

High-order coreal wavefront analysis was performed in a population of 60 myopic eyes that underwent photorefractive keratectomy. Corneal aberration data over 3, 5, and 7 mm pupils were collected for up to three years after surgery. The optical performance of the anterior cornea was characterized by estimation of the modulation transfer function (MTF) and the point-spread function. The high-order corneal wavefront aberrations were shown to stabilize one year after surgery. Over photopic pupils, after an early slight increase, corneal RMS-high-order aberrations (HOA) tended to decrease toward preoperative values. On the other hand, over mid- and large-pupil sizes, corneal HOA significantly increased compared with the preoperative state, while the optical performance of the cornea was diminished. The MTF ratio showed a distinct decline in the optical quality of postoperative corneas at low and middle spatial frequencies over larger pupils in the range between 6 and 19 c/deg, especially for deeper ablations.