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Journal of Refractive Surgery... May 2024To report on the prospective evaluation of photorefractive keratectomy (PRK) in experienced ametropic naval aviators that led to the approval of refractive surgery for...
PURPOSE
To report on the prospective evaluation of photorefractive keratectomy (PRK) in experienced ametropic naval aviators that led to the approval of refractive surgery for military pilots.
METHODS
This was the first study evaluating refractive surgery in naval aviators. Return to flight status after PRK and clinical outcomes and subjective and objective flight performance were evaluated.
RESULTS
A total of 785 U.S. naval aviators were enrolled in the study. Average preoperative refraction was -2.92 ± 1.73 diopters (D) (range: +5.25 to -9.13 D). By 6 months, 85.9% of eyes were within ±0.50 D and 96.4% were within ±1.00 D of emmetropia. 94.4% of eyes achieved 20/20 or better, 74.3% had 20/16 or better, and 45.2% had 20/12.5 or better uncorrected distance visual acuity (UDVA) at 6 months. A total of 78.5% of aviators met return-to-flight criteria by 4 weeks, 83.3% by 8 weeks, and 90.8% by 12 weeks following PRK. All aviators eventually returned to full flight status. Cumulative flight experience included logging more than 48,000 flight hours and 19,500 landings in the 6 months following PRK. Psychometric questionnaire results showed that 78% reported improved ability to detect other aircraft and 92% reported improved ability to land on an aircraft carrier (82% significantly improved) compared to wearing corrective lenses. No one felt their vision was worse in these dynamic environments. All aviators indicated they would undergo the procedure again and would recommend it to a fellow aviator.
CONCLUSIONS
This prospective study in U.S. naval aviators determined PRK to be safe and effective in a unique patient population operating in a visually demanding and hazardous environment. The program continues to be enthusiastically supported by aviators and PRK is now allowed in all branches of the military and for National Aeronautics and Space Administration astronauts. .
Topics: Photorefractive Keratectomy; Humans; Prospective Studies; Military Personnel; Visual Acuity; Adult; Male; United States; Female; Myopia; Lasers, Excimer; Refraction, Ocular; Young Adult; Middle Aged; Aerospace Medicine; Treatment Outcome
PubMed: 38848054
DOI: 10.3928/1081597X-20240422-02 -
Journal of Refractive Surgery... May 2024To assess the predictive accuracy of new-generation online intraocular lens (IOL) power formulas in eyes with previous myopic laser refractive surgery (LRS) and to...
PURPOSE
To assess the predictive accuracy of new-generation online intraocular lens (IOL) power formulas in eyes with previous myopic laser refractive surgery (LRS) and to evaluate the influence of corneal asphericity on the predictive accuracy.
METHODS
The authors retrospectively evaluated 52 patients (78 eyes) with a history of laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) who subsequently underwent cataract surgery. Refractive prediction errors were calculated for 12 no-history new online formulas: 8 formulas with post-LRS versions (Barrett True-K, EVO 2.0, Hoffer QST, and Pearl DGS) using keratometry and posterior/total keratometry measured by IOLMaster 700 and 4 formulas without post-LRS versions (Cooke K6 and Kane) using keratometry and total keratometry. The refractive prediction error, mean absolute error (MAE), and percentages of eyes with prediction errors of ±0.25, ±0.50, ±0.75, ±1.00, and ±1.50 diopters (D) were compared.
RESULTS
The MAEs of the 12 formulas were significantly different (F = 83.66, < .001). The MAEs ranged from 0.62 to 0.94 D and from 1.07 to 1.84 D in the formulas with and without post-LRS versions, respectively. The EVO formula produced the lowest MAE (0.60) and MedAE (0.47), followed by the Barrett True-K (0.69 and 0.50, respectively). Each percentage of eyes with refractive prediction error was also significantly different among the 12 formulas ( < .001).
CONCLUSIONS
The EVO and Barrett True-K formulas demonstrate comparable performance to the other existing formulas in eyes with a history of myopic LASIK/PRK. Surgeons should use these formulas with post-LRS versions and input keratometric values whenever possible. .
Topics: Humans; Retrospective Studies; Myopia; Lenses, Intraocular; Female; Male; Refraction, Ocular; Middle Aged; Photorefractive Keratectomy; Keratomileusis, Laser In Situ; Lens Implantation, Intraocular; Adult; Optics and Photonics; Visual Acuity; Lasers, Excimer; Cornea; Reproducibility of Results; Biometry; Phacoemulsification; Aged
PubMed: 38848053
DOI: 10.3928/1081597X-20240422-01 -
Indian Journal of Ophthalmology May 2024This study aimed to report the long-term results of combined topography-guided photorefractive keratectomy (PRK) and accelerated corneal collagen cross-linking (CXL) for...
PURPOSE
This study aimed to report the long-term results of combined topography-guided photorefractive keratectomy (PRK) and accelerated corneal collagen cross-linking (CXL) for keratoconus using the Zeiss refractive coordinated system.
METHODS
A prospective interventional study was conducted in a tertiary eye care hospital in South India. Patients with mild-to-moderate progressive keratoconus and corneal pachymetry greater than 450 μm were included. They underwent customized topography-guided PRK followed by CXL. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and keratometry readings and complications were evaluated at 1, 3, 6, 12, and 24 months postoperatively.
RESULTS
Thirty patients (30 eyes) were included in the study. All study parameters showed a statistically significant improvement postoperatively over baseline values. At 24 months, the mean UDVA improved from 0.8 ± 0.180 logarithm of the minimum angle of resolution (logMAR) to 0.38 ± 0.118 logMAR ( P -value <0.001) and CDVA improved from 0.467 ± 0.142 logMAR to 0.227 ± 0.078 logMAR ( P -value <0.001). The mean flat, steep, and maximum keratometry values were significantly reduced by 2.133, 3, and 4.54 diopters, respectively, at the last follow-up examination ( P -value <0.001).
CONCLUSION
The combined topography-guided PRK and accelerated CXL procedure seem to be a promising treatment alternative for early keratoconus. This is the first such study on the Zeiss refractive coordinated system. However, further studies with a larger study population and longer follow-up periods are required to draw final conclusions about the benefits of this procedure in keratoconus.
PubMed: 38767551
DOI: 10.4103/IJO.IJO_791_23 -
Journal of Glaucoma May 2024The study showed that Corvis ST's bIOP and ORA's IOPcc do not agree well, before or after PRK, and may not be used interchangeably. bIOP remained unchanged after PRK.
PRECIS
The study showed that Corvis ST's bIOP and ORA's IOPcc do not agree well, before or after PRK, and may not be used interchangeably. bIOP remained unchanged after PRK.
PURPOSE
To evaluate the agreement between the biomechanically-corrected intraocular pressure (bIOP) measured by the Corvis-ST and the cornea-compensated IOP (IOPcc) measured by the Ocular Response Analyzer (ORA) before and after photorefractive keratectomy (PRK).
METHODS
In this prospective interventional study, a total of 53 patients (53 eyes) were included. Measurements were acquired using both the Corvis-ST and ORA devices before and 3 months post- PRK. The agreement between the two devices was evaluated using limits of agreement (LoA) and Bland-Altman plots.
RESULTS
The participants had a mean age of 29.6±5.21 years (range: 21 to 40), with 41 (77.4%) of them being female. Following the surgery, the average change in IOP was 0.3±1.7 mmHg for bIOP and -1.6±4.0 mmHg for IOPcc. The corresponding 95% LoA were -3.5 to 4.2 mmHg and -9.5 to 6.3 mmHg, respectively. The 95% LoA between bIOP and IOPcc after PRK was -2.3 to 8.5 mmHg. Notably, the bIOP values were higher for IOPs <20 mmHg and lower for IOPs >20 mmHg compared to IOPcc.
CONCLUSIONS
The findings indicate a weak agreement between the Corvis ST-bIOP and the ORA- IOPcc both before and after PRK. These devices may not be used interchangeably for IOP measurement. bIOP exhibited less variation compared to the IOPcc, suggesting that the bIOP is a superior option for IOP reading following PRK.
PubMed: 38767500
DOI: 10.1097/IJG.0000000000002434 -
International Journal of Ophthalmology 2024To study the effect of mitomycin C (MMC) applied during transepithelial photorefractive keratectomy (TPRK) on the corneal endothelium one week (W1) and three months (M3)...
AIM
To study the effect of mitomycin C (MMC) applied during transepithelial photorefractive keratectomy (TPRK) on the corneal endothelium one week (W1) and three months (M3) after surgery and its determinants.
METHODS
In this two-armed cohort study conducted in 2022, eyes treated with MMC during TPRK (group 1) were compared with eyes not treated with MMC (group 2). The corneal endothelial cell (EC) count, EC density (ECD; cells/mm), average (µm), standard deviation (µm), coefficient of variation (CV%), EC, EC, and EC percentage of hexagonality were estimated at W1 and M3. The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables.
RESULTS
Group 1 had 26 eyes, and group 2 had 78 eyes. All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2. The MMC usage was not a significant predictor of the change in ECD (=0.644), change in CV (=0.374), and change in the percentage of hexagonality of EC (=0.164) at W1. However, the use of MMC was a significant predictor of changes in CV (=0.014) and the change in the percentage of hexagonality of EC (=0.039) at M3. The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices, postoperatively.
CONCLUSION
The use of MMC doesn't affect ECD, CV, and percentage of hexagonality at W1 if other surgical indices are considered. At M3 after operating myopic eyes by TPRK, MMC significantly influence the CV and percentage of hexagonality. The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.
PubMed: 38766343
DOI: 10.18240/ijo.2024.05.16 -
Merging PRK and Collagen Crosslinking: An Analysis of Literature and a Guide to Prevalent Protocols.Cornea May 2024The purpose of this review was to summarize the different surgical approaches combining photorefractive keratectomy (PRK) and corneal crosslinking (CXL), present each...
PURPOSE
The purpose of this review was to summarize the different surgical approaches combining photorefractive keratectomy (PRK) and corneal crosslinking (CXL), present each protocol template in a simple format, and provide an overview of the primary outcomes and adverse events.
METHODS
A literature review was conducted as outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eight different databases were searched. Papers were included if PRK was immediately followed by CXL.
RESULTS
Thirty-seven papers met the inclusion criteria of a total yield of 823. The latest research into simultaneous PRK and CXL has been shown to not only stabilize the cornea and prevent keratoconus progression but also improve the visual acuity of the patient. Improvements in uncorrected distance visual acuity and (spectacle) corrected distance visual acuity were found to be significant when considering all protocols. There were also significant reductions in K1, K2, mean K, Kmax, sphere, cylinder, and spherical equivalent. Random-effects analysis confirmed these trends. Corrected distance visual acuity was found to improve by an average of 0.18 ± 1.49 logMAR (Cohen's D [CD] 0.12; P <0.02). There was also a significant reduction of 2.57 ± 0.45 D (CD 5.74; P <0.001) in Kmax. Cylinder and spherical equivalent were also reduced by 1.36 ± 0.26 D (CD 5.25; P <0.001) and 2.61 ± 0.38 D (CD 6.73; P <0.001), respectively.
CONCLUSIONS
Combining the 2 procedures appears to be of net benefit, showing stabilization and improvement of ectatic disease, while also providing modest gains in visual acuity. Since customized PRK and CXL approaches appear superior, a combination of these would likely be best for patients.
PubMed: 38759151
DOI: 10.1097/ICO.0000000000003536 -
Translational Vision Science &... May 2024Computational models can help clinicians plan surgeries by accounting for factors such as mechanical imbalances or testing different surgical techniques beforehand....
PURPOSE
Computational models can help clinicians plan surgeries by accounting for factors such as mechanical imbalances or testing different surgical techniques beforehand. Different levels of modeling complexity are found in the literature, and it is still not clear what aspects should be included to obtain accurate results in finite-element (FE) corneal models. This work presents a methodology to narrow down minimal requirements of modeling features to report clinical data for a refractive intervention such as PRK.
METHODS
A pipeline to create FE models of a refractive surgery is presented: It tests different geometries, boundary conditions, loading, and mesh size on the optomechanical simulation output. The mechanical model for the corneal tissue accounts for the collagen fiber distribution in human corneas. Both mechanical and optical outcome are analyzed for the different models. Finally, the methodology is applied to five patient-specific models to ensure accuracy.
RESULTS
To simulate the postsurgical corneal optomechanics, our results suggest that the most precise outcome is obtained with patient-specific models with a 100 µm mesh size, sliding boundary condition at the limbus, and intraocular pressure enforced as a distributed load.
CONCLUSIONS
A methodology for laser surgery simulation has been developed that is able to reproduce the optical target of the laser intervention while also analyzing the mechanical outcome.
TRANSLATIONAL RELEVANCE
The lack of standardization in modeling refractive interventions leads to different simulation strategies, making difficult to compare them against other publications. This work establishes the standardization guidelines to be followed when performing optomechanical simulations of refractive interventions.
Topics: Humans; Finite Element Analysis; Cornea; Photorefractive Keratectomy; Computer Simulation; Lasers, Excimer; Models, Biological
PubMed: 38748408
DOI: 10.1167/tvst.13.5.11 -
Vestnik Oftalmologii 2024The study investigates the influence of changes in keratometric parameters after refractive surgery on the results of Maklakov tonometry.
PURPOSE
The study investigates the influence of changes in keratometric parameters after refractive surgery on the results of Maklakov tonometry.
MATERIAL AND METHODS
The study examined a total of 61 people (121 eyes). The patients were divided into a control group with no history of surgery (16 people, 31 eyes), a LASIK group (13 people, 26 eyes), a femtosecond-assisted LASIK (FS-LASIK) group (16 people, 32 eyes), and a photorefractive keratectomy (PRK) group (16 people, 32 eyes). The patients underwent standard examination, keratometry (Km), Maklakov tonometry with a 10 g weight, and elastotonometry with 5, 7.5, and 15 g weights.
RESULTS
In the LASIK group, the indentation diameter with 5 and 7.5 g weights correlated with Km in the central and near-paracentral zone (=0.3-0.5). Tonometry with a 10 g weight did not correlate with anything. Tonometry with a 15 g weight inversely correlated with Km in the paracentral points (4 mm) of the strong meridian (= -0.5 ... -0.7). In the FS-LASIK group, a significant inverse correlation with Km was observed only for the indentation diameter with a 10 g weight in the paracentral (3-4 mm) zone (= -0.4 ... -0.5). In the PRK group, weak (<0.4) correlations were found between Km and the indentation diameter of the 7.5 and 10 g weights for the central zone (1-2 mm). No significant correlations were found for 5 and 15 g weights.
UNLABELLED
In the control group, there were practically no correlations for 5 and 7.5 g weights. The indentation diameter of the 10 g weight evenly correlated with Km at all points (= -0.38 ... -0.60), the indentation of the 15 g weight correlated mainly with the curvature of the horizontal meridian (= -0.37 ... -0.49).
CONCLUSION
Tonometry readings with the 10 g weight are the most dependent on Km in different groups, and the readings with the 5 g weight are the least dependent. LASIK is characterized by the largest scatter of dependencies for weights of different masses, FS-LASIK - by the smallest. Tonometry readings with the 5 g weight correlated with Km only in the LASIK group, and this was the only direct correlation. Considering the inverse nature of most correlations, higher Km may be associated with an overestimation of tonometry results, and lower Km - with its underestimation.
Topics: Humans; Adult; Male; Female; Tonometry, Ocular; Photorefractive Keratectomy; Keratomileusis, Laser In Situ; Cornea; Myopia; Intraocular Pressure
PubMed: 38739131
DOI: 10.17116/oftalma202414002251 -
Journal of Refractive Surgery... May 2024To compare the effects of three common refractive surgeries on corneal biomechanics. (Comparative Study)
Comparative Study
PURPOSE
To compare the effects of three common refractive surgeries on corneal biomechanics.
METHODS
Two hundred seven patients who had refractive surgery were included in this study, of whom 65 received transepithelial photorefractive keratectomy (tPRK), 73 received femtosecond laser-assisted laser in situ keratomileusis (FSLASIK), and 69 received small incision lenticule extraction (SMILE). Each patient had biomechanical measurements using the Corvis ST (Oculus Optikgeräte GmbH) preoperatively and at 3 and 6 months postoperatively. The measurements included five parameters expected to be associated with corneal biomechanics: deformation amplitude ratio at 2 mm (DAR2), integrated inverse radius (IIR), stiffness parameter at first applanation (SP-A1), highest concavity time (HCT), and the updated stress-strain index (SSIv2). The variations in these parameters postoperatively among the three surgeries, and their relationship with corneal thickness (CCT) and intraocular pressure measured by the Dynamic Contour Tonometer (DCT-IOP) were analyzed.
RESULTS
SP-A1 decreased significantly from preoperatively to 3 months postoperatively in all three groups, whereas DAR2 and IIR increased significantly, all indicating stiffness losses. Between 3 and 6 months postoperatively, the results were inconsistent, with DAR2 decreasing (indicating stiffness increases) and IIR increasing (denoting stiffness decreases) in the FS-LASIK and SMILE groups. The decrease in SSIv2 (the only measure of corneal material stiffness) postoperatively was comparatively less pronounced at both 3 and 6 months postoperatively. On the other hand, HCT remained generally stable after all three surgeries. Unlike DAR2, IIR, and SP-A1, the changes postoperatively in stiffness parameters HCT and SSIv2 were independent of the corresponding changes in both DCT-IOP and CCT.
CONCLUSIONS
Among the stiffness parameters considered, SSIv2 was not correlated with CCT or DCT-IOP, and holds promise for representing the corneal material stiffness and how it remains largely unaffected by refractive surgeries. Overall, FS-LASIK had the most significant impact on corneal stiffness, followed by SMILE, and finally tPRK. .
Topics: Humans; Cornea; Adult; Female; Male; Biomechanical Phenomena; Lasers, Excimer; Keratomileusis, Laser In Situ; Young Adult; Elasticity; Myopia; Intraocular Pressure; Photorefractive Keratectomy; Visual Acuity; Refraction, Ocular; Middle Aged; Prospective Studies; Corneal Surgery, Laser; Corneal Topography
PubMed: 38717086
DOI: 10.3928/1081597X-20240322-01 -
Journal of Refractive Surgery... May 2024To review the atypical development of Salzmann's nodular degeneration (SND) after two cases of laser in situ keratomileusis (LASIK) and one case of photorefractive... (Review)
Review
PURPOSE
To review the atypical development of Salzmann's nodular degeneration (SND) after two cases of laser in situ keratomileusis (LASIK) and one case of photorefractive keratomileusis (PRK), and to highlight the pathophysiology of SND and its treatment.
METHODS
Three cases of SND (two following LASIK performed with microkeratomes and one following PRK) were reviewed and Pubmed.gov and internet searches were performed.
RESULTS
SND is myofibroblast-generated fibrosis in the subepithelial space between the epithelium and Bowman's layer that develops years or decades after traumatic, surgical, infectious, or inflammatory injuries to the cornea in which the epithelial basement membrane is damaged in one or more locations and does not fully regenerate. It is hypothesized based on these cases, and the previous immunohistochemistry of other investigators, that myofibroblast precursors, such as fibrocytes or corneal fibroblasts, that enter the subepithelial space are driven to develop into myofibroblasts, which slowly proliferate and extend the fibrosis, by transforming growth factor-beta from epithelium and tears that passes through the defective epithelial basement membrane. These myofibroblasts and the disordered collagens, and other extracellular matrix components they produce, make up the subepithelial opacity characteristic of SND. Nodules are larger accumulations of myofibroblasts and disordered extracellular matrix. If the injury is associated with damage to the underlying Bowman's layer and stroma, as in LASIK flap generation, then the myofibroblasts and fibrosis can extend into Bowman's layer and the underlying anterior stroma.
CONCLUSIONS
SND fibrosis often extends into Bowman's layer and the anterior stroma if there are associated Bowman's defects, such as incisions or lacerations. In the latter cases, SND frequently cannot be removed by simple scrape and peel, as typically performed for most common SND cases, but can be trimmed to remove the offending tissue. This condition is more accurately termed Salzmann's subepithelial fibrosis. .
Topics: Humans; Fibrosis; Keratomileusis, Laser In Situ; Photorefractive Keratectomy; Epithelium, Corneal; Male; Bowman Membrane; Adult; Myopia; Female; Corneal Diseases; Lasers, Excimer; Myofibroblasts; Middle Aged
PubMed: 38717084
DOI: 10.3928/1081597X-20240322-02