Twenty-Year Follow-Up of Excimer Laser Photorefractive Keratectomy: A Retrospective Observational Study

Effect of Ablation Depth on the Endothelial Status of Eyes of Myopic Patients Undergoing Transepithelial Photorefractive Keratectomy: A Retrospective Study in Saudi Arabia

PURPOSE

The aim of this study was to correlate ablation depth on corneal endothelial cell (EC) indices following transepithelial photorefractive keratectomy (TPRK) in Saudi myopic patients.

METHODS

This was a retrospective cohort study of myopic eyes treated with TPRK. The changes in EC density and other indices were noted one week (W1) and 12 weeks (W12) after TPRK, which was the primary outcome. The laser ablation depth (AD) was correlated to the EC indices. The preoperative factors were also correlated to the outcomes using regression analysis to review predictors of change in the EC density.

RESULTS

We had 120 eyes of 60 myopic patients operated on for TPRK. The mean of maximum AD (Adm) and central AD (ADc) were 110.3±23.7 µ and 108.8±24.4 µ, respectively. The median change in EC count at W1 and W12 were -9.5 (interquartile range (IQR) -33.0, 17.0) and -3.0 (IQR -29.3, 13.3), respectively. The ADm was negatively correlated to a change in EC density at W1 (Wilcoxon (Z) =-2.7, P = 0.006) and at W12 (Z = -3.74, P <0.001). ADm (Kruskal-Wallis (K-W) test (P) = 0.167), ADc (K-W P = 0.08), central corneal thickness (K-W P = 0.65), and use of mitomycin-C (K-W P = 0.357) were not significant predictors of the change in EC density at W1. None of the variables significantly influenced the change in EC density at W12.

CONCLUSIONS

The corneal ablation depth for TPRK is correlated to changes in EC density at W1 and W12 after TPRK.

Refractive Errors Among Members of the Armed Forces of the Czech Republic

Objective: To evaluate the prevalence of refractive errors among members of the Armed Forces of the Czech Republic, to recommend a safe way of correcting refractive errors with regard to the specific needs of military personnel (especially members of combat units and flying personnel), and to propose a system for solving these errors in order to increase combat effectivity. Methodology: Questionnaire to determine previous refractive surgery and spectacle correction wear. Measurement of refraction with a hand-held autorefractometer and evaluation of current visual acuity on ETDRS optotypes (Landolt rings). Results: 259 servicemen (518 eyes) were investigated. The return rate of the questionnaires was 100%. The incidence of myopia greater than -0.75D was 22% (113 eyes), myopia greater than -0.5D 32% (166 eyes). The mean value of myopia was -0.78 D (SD ±0.6). Hypermetropia values ranged from +0.25 to +5.0 D. The mean value of hypermetropia was 0.63 D (SD ±0.7). Astigmatism values ranged from -0.25 to -3.75. The mean value of astigmatism was -0.55 Dcyl (SD ±0.49). The average visual acuity was 84.1 letters ETDRS SD (±6.1), visual acuity worse than 80 letters was manifested by 23% of the members of the monitored group. 25 people (10%) had undergone laser refractive surgery. Visual acuity after laser refractive surgery was measured in 19 people (38 eyes). Mean uncorrected post-laser visual acuity was 83.87 (SD ±6.1) ETDRS letters. The mean follow-up period after laser refractive surgery was 6.78 (SD ±4.8) years. Conclusion: Despite the initial selection of military personnel and entry limitations, the prevalence of refractive errors is comparable to the general population. However, in contrast with the general population, refractive errors larger than -3.0 D were not represented in the group. Due to the finding of insufficient correction of refractive errors, increased emphasis should be placed on identifying and regularly observing military personnel with refractive errors

A No-History Multi-Formula Approach to Improve the IOL Power Calculation after Laser Refractive Surgery: Preliminary Results

This retrospective comparative study proposes a multi-formula approach by comparing no-history IOL power calculation methods after myopic laser-refractive-surgery (LRS). One-hundred-thirty-two eyes of 132 patients who had myopic-LRS and cataract surgery were examined. ALMA, Barrett True-K (TK), Ferrara, Jin, Kim, Latkany and Shammas methods were evaluated in order to back-calculate refractive prediction error (PE). To eliminate any systematic error, constant optimization through zeroing-out the mean error (ME) was performed for each formula. Median absolute error (MedAE) and percentage of eyes within ±0.50 and ±1.00 diopters (D) of PE were analyzed. PEs were plotted with corresponding mean keratometry (K), axial length (AL), and AL/K ratio; then, different ranges were evaluated. With optimized constants through zeroing-out ME (90 eyes), ALMA was better when K ≤ 38.00 D-AL > 28.00 mm and when 38.00 D < K ≤ 40.00 D-26.50 mm < AL ≤ 29.50 mm; Barrett-TK was better when K ≤ 38.00 D-AL ≤ 26.50 mm and when K > 40.00 D-AL ≤ 28.00 mm or AL > 29.50 mm; and both ALMA and Barrett-TK were better in other ranges. (p < 0.05) Without modified constants (132 eyes), ALMA was better when K > 38.00 D-AL ≤ 29.50 mm and when 36.00 < K ≤ 38.00 D-AL ≤ 26.50 mm; Barrett-TK was better when K ≤ 36.00 D and when K ≤ 38.00 D with AL > 29.50 mm; and both ALMA and Barrett-TK were better in other ranges (p < 0.05). A multi-formula approach, according to different ranges of K and AL, could improve refractive outcomes in post-myopic-LRS eyes.

Comparison of Vision Correction and Corneal Thickness at 180-Day Follow-Up After Femtosecond Laser-Assisted In-Situ Keratomileusis (FS-LASIK), Photorefractive Keratectomy (PRK), and Small Incision Lenticule Extraction (SMILE): A Study from a Single Center in Poland of 120 Patients with Myopia

BACKGROUND This study from a single center in Poland included 120 patients with myopia, and the aim was to compare vision correction and corneal thickness at the 180-day follow-up after femtosecond laser-assisted in-situ keratomileusis (FS-LASIK), photorefractive keratectomy (PRK), or small incision lenticule extraction (SMILE). MATERIAL AND METHODS The effectiveness and safety of laser vision correction (LVC) procedures were evaluated by determining pre- and post-procedure uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) values on the Snell chart. Twenty patients with diagnosed mild myopia (sphere maximum -3.0 diopters D; cylinder maximum 0.5 D) were qualified for PRK surgery. Fifty patients with diagnosed intolerance (sphere maximum -6.0 D; cylinder maximum 5.0 D) were eligible for the FS-LASIK procedure. Fifty patients with diagnosed myopia (sphere maximum -6.0 D cylinder 3.5 D) were qualified for the SMILE procedure. RESULTS Regardless of which procedure was performed, both UDVA and CDVA improved significantly postoperatively (P<0.05). In addition, the UDVA and CDVA values were similar in the postoperative period (P>0.05). For each procedure, the EI was no less than 0.94. Regardless of which type of LVC procedure was performed, CET at the center and 1.5 mm from the center in 4 meridians thickened, and this change was not statistically significant over the observation period (P>0.05). CONCLUSIONS Our analysis demonstrated similar effectiveness of the 3 methods - PRK, FS-LASIK, and SMILE - in patients with mild and moderate myopia.

Unexpected ocular morphological changes after corneal refractive surgery: A review

Corneal refractive surgery (CRS) currently is widely used to correct refractive errors because of its efficacy and reliability. Several studies dealt with the corneal modification induced by this type of surgery, but it is still debated if CRS can induce unexpected changes namely anterior chamber depth (ACD) and axial length (AL). A literature review was performed, including all articles regarding CRS and eye-variations from 1999 to December 2021. Excluding articles about specific systemic conditions (e.g., pregnancy), pathological conditions, post-surgical complications or about only corneal flattening and thinning post CRS, we found nine studies that met the search criteria. We divided the found articles according to the type of surgery performed (radial keratotomy, PRK/LASEK, lasik) and analyzed the results about ACD and AL. Finally, according to the literature, we can conclude that CRS not only gives a corneal flattening, thinning and biomechanical changes, but also induces AL and ACD decrease. This makes the AL and ACD measurements obtained before CRS uselessness in case of IOL power calculation.

A formula to improve the reliability of optical axial length measurement in IOL power calculation

To verify the influence of axial length (AL) variations after cataract surgery in IOL power calculation. Patients underwent ophthalmic evaluation before surgery, including optical biometry with IOLMaster 500. Same exams were repeated 2 months after surgery: AL of operated eye was evaluated using two modes (pseudophakic/aphakic options). Mean Keratometry and AL changes were analyzed. Furthermore, refractive prediction error (PE) was back-calculated with Barrett Universal-II, Hoffer-Q, Holladay-1 and SRK/T formulas. To eliminate any systematic error, the mean error (ME) was zeroed-out for each formula. MEs and median absolute errors (MedAEs) of PEs were analyzed. Two-hundred-one operated eyes of 201 patients and 201 opposite eyes were evaluated. In operated eyes, mean AL difference was - 0.11 ± 0.07 mm (p < 0.001) with pseudophakic option and 0.00 ± 0.07 mm (p = 0.922) with aphakic option. There were not-statistically significant differences between MedAE of PEs calculated after zeroing-out the ME with different ALs (p > 0.05). Instead, only MEs of PEs obtained with postoperative ALs-pseudophakic option were not-statistically different from zero (p > 0.05). AL measurement change after cataract surgery is probably due to a systematic error in optical biometer in case of phakic eyes. A correction factor applied to preoperative AL could eliminate any systematic error in IOL power calculation without modifying the lens constant.

Ten-Year Outcome of Topography-Guided Transepithelial Surface Ablation for Refractive Myopia Treatment

BACKGROUND

To evaluate 10-year long-term refractive visual stability and participants' satisfaction in the refractive treatment of myopic eyes undergoing topography-guided transepithelial surface ablation using a 1KHz excimer laser.

PATIENTS AND METHODS

This single-center prospective survey assessed participants' satisfaction 10 years after the treatment using a non-validated questionnaire with regards to visual outcome, dry eye, and visual disturbance symptoms. Pre- and postoperative visual and refractive data were evaluated.

RESULTS

Of 106 participants (54% females) with a mean patient age of 36 (± 8.6) years, 166 eyes were included. Mean preoperative spherical equivalent (SE) was - 4.23 (± 2.48) diopters (D). Uncorrected distant visual acuity (UCVA) after 10 years was ≥ 1.0 (Snellen) in 92% of the eyes. Manifest SE was within ± 1.0 D of the desired refraction in 86% of the eyes after 10 years. Mean quality of life (QOL) improvement was high (9.15 out of 10 points). Dry eye symptoms were reported by 35 out of 104 (34%) patients. Visual symptoms like halos or starbursts were reported by 24 out of 101 (24%) and 12 out of 100 (12%) patients, respectively.

CONCLUSIONS

Topography-guided transepithelial surface ablation for myopia provided stable long-term results in terms of UCVA and SE. Participant satisfaction was high, with only low rates of dry eye or visual symptoms.

[Long-term outcomes of PRK, LASIK and SMILE]

BACKGROUND

Patients and refractive surgeons have a legitimate interest in the long-term results of the most commonly used laser procedures for correction of ametropia.

OBJECTIVE

To assess the safety, predictability, stability and late complications according to the current recommendations of the committee for refractive surgery (KRC).

METHODS

Literature search in PubMed with the search term "long-term outcome" combined with either "PRK", "LASIK" or "SMILE". Articles about PRK and LASIK with a minimum follow-up of 10 years and SMILE with a minimum follow-up of 5 years were evaluated and duplications were eliminated.

RESULTS

From a total of 440 articles that matched these search terms 15 articles were selected and analyzed. The results of PRK were described in 4 studies with a total of 666 eyes, 7 studies (566 eyes) described the results of LASIK and 5 studies (188 eyes) the results after SMILE.

CONCLUSION

Long-term studies with follow-up periods of at least 10 years have shown that PRK and LASIK treatment carried out in the early days of medical excimer lasers have a very high level of safety and late complications occurred only rarely. The effectiveness of particularly high corrections declined over time. In contrast, there was no clinically significant regression within the indications recommended by the KRC. The results of SMILE were not inferior to those of PRK and LASIK. In direct long-term comparisons no procedure showed a clear superiority. Due to technological improvements in hardware and software for both preoperative diagnostics and lasers, treatment performed nowadays is presumably even safer, more efficient and also more stable over a long period of time.

Comparison between two devices in the detection of corneal thickness changes after cataract surgery

This study compared corneal thickness (CT) changes obtained with specular microscopy (SM) and a rotating Scheimpflug camera (RSC) after conventional phacoemulsification surgery (PS). One hundred sixty six eyes of 83 patients were analyzed before and one month after PS. One eye underwent PS, while the fellow phakic one was used as control. CT was measured with SM at the center of the cornea and with RSC at the pupil center, at the corneal apex and at the thinnest point. In the operated eye, SM showed a larger CT mean increase than those one detected at the three different measurements’ points evaluated by RSC. Inversely, in the fellow phakic eye, SM showed a greater CT mean decrease than those one registered by RSC at its three measurement’s points. Thus, one month after surgery, even if cornea appears clear at the slit-lamp, a significant thickness increase is still present. This is even more evident if the slight decrease of the fellow phakic eye is considered. The differences between the two devices are probably related to the different measured areas.