Fourier analysis of corneal irregular astigmatism after small-incision lenticule extraction and transepithelial photorefractive keratectomy: A comparative study

To compare changes in the spherical component, regular astigmatism, and irregular astigmatism of the anterior surface of the cornea after small-incision lenticule extraction (SMILE) and transepithelial photorefractive keratectomy (TransPRK). Fifty-six patients underwent SMILE in 56 eyes, and 68 patients underwet TransPRK in 68 eyes. The right eye was chosen to enter the group. Six months after the procedure, Scheimpflug images were acquired, and Fourier analysis of the anterior surface of patients' corneas was performed using the Pentacam built-in software. Fourier parameters encompass various measurements such as the steepest radius of the curvature and average eccentricity of the spherical components (SphRmin and SphEcc), maximum decentration (MaxDec), central and peripheral regular astigmatism (regular astigmatism at the center [AstC] and regular astigmatism at the periphery [AstP]), and irregularity (Irr). At 6 months postoperatively, SphEcc decreased significantly (P < .001), MaxDec increased significantly (P < .001), and Irr increased insignificantly (P = .254) in the SMILE group. SphEcc decreased significantly (P < .001) and MaxDec and Irr increased significantly (P < .001) in the TransPRK group. TransPRK caused greater changes in SphEcc, MaxDec, and Irr on the anterior corneal surface than SMILE (P < .05). The amount of MaxDec-induced changes in SMILE and TransPRK was significantly correlated with the amount of higher-order aberrations and spherical aberration changes (P < .05). SMILE and TransPRK increase overall irregular astigmatism on the anterior surface of the cornea, more so with TransPRK, where changes in decentration are associated with with increased higher-order aberrations.

Phacoemulsification, pinhole pupilloplasty, and pre-Descemet's endothelial keratoplasty for keratoconus with Fuchs' endothelial dystrophy

The comorbidity of keratoconus with Fuchs' endothelial dystrophy with cataract is a rare clinical combination. We present an amalgamation of surgical techniques to manage the above clinical conditions and its complications in single setting. The modified triple procedure, namely, the phacoemulsification, pinhole pupilloplasty, and pre-Descemet's endothelial keratoplasty (PDEK) in the order of description is followed in single sitting. Lens removal by phacoemulsification, correction of irregular astigmatism by pinhole pupilloplasty (pinhole optics), and exchanging the endothelial layer for PDEK forms the main segments of the triple procedure. This combination of techniques may decrease the risk of multiple surgeries and its related complications. Moreover, it will allow the patient for faster visual rehabilitation by improving the uncorrected visual acuity and visual quality.

Correction of moderate to high refractive astigmatism with extended range toric soft contact lenses in patients with different patterns of astigmatism

PURPOSE

This study aimed to evaluate the visual performance of extended range, toric soft contact lenses (TSCLs) in patients with keratoconus and moderate to high astigmatism with different astigmatic patterns.

METHODS

This was a retrospective, cross-sectional clinical study. Extended range TSCL users with astigmatism ≥3.0 D were included. Cases were categorised into three subgroups, namely regular, irregular (non-keratoconus) and keratoconic based on the topographic pattern of astigmatism. In addition, subjects were subdivided based on the degree of astigmatism.

RESULTS

Fifty five patients (82 eyes) were enrolled, of whom 28 (51%) were female. The mean age was 24.2 ± 7.5 (range: 8-41 years) years. Thirty-six eyes with regular astigmatism (43.9%), 34 eyes with irregular astigmatism (41.5%) and 12 eyes with keratoconus (14.6%) were included. The percentage improvement in visual acuity (VA) was significantly higher with contact lenses compared with spectacles in all groups (p < 0.001), with the highest improvement in subjects with keratoconus (p = 0.03). Twenty six (31.7%), 30 (36.6%) and 26 eyes (31.7%) had moderate (-3.0 to -4.24 D), moderate/high (-4.25 to -5.99 D) and high (≤-6.0 D) astigmatism, respectively. The percentage improvement in VA with contact lenses was statistically significantly higher than for spectacle wear in all groups (p < 0.001).

CONCLUSIONS

This study demonstrated that satisfactory visual outcomes can be obtained with extended range TSCLs in patients having moderate to high astigmatism with different astigmatic patterns.

Update on indications, complications, and outcomes of scleral contact lenses

Background

The role of scleral contact lenses (SCLs) has increasingly expanded since the first lens was fitted more than a century ago. While it was initially prescribed for the management of severely compromised corneas, the indications for modern SCL use have expanded to include less severe diseases. In this review, we aimed to provide an up-to-date overview of the current indications, complications, and outcomes for the various types of SCLs.

Methods

In this narrative review, we thoroughly searched the PubMed/MEDLINE database for literature published from January 1980 to November 2021. Only relevant up-to-date English references were included. Furthermore, the figures in this manuscript were derived from our unit's patient documentation.

Results

Currently, SCLs can successfully be used to manage ocular surface diseases, visually rehabilitate irregular corneas, and correct irregular refractive errors. Although newer materials have yielded the same visual outcomes with fewer complications, these consequences still occur in approximately one-third of contact lens wearers, including difficulties in insertion and/or removal, discomfort or pain, and developing either halos, blurriness, or haze. Even though most of these complications are minor and can be easily treated, a good practice is essential to avoid sight-threatening complications such as microbial keratitis.

Conclusions

SCLs are indispensable in ophthalmic clinics. The development of better-quality SCLs has increased the number of indications and improved the achievable visual rehabilitation. The future of developing improvements in SCL design, materials, and fit, and the expansion of their indication range is promising.

Long-Term Follow-Up of Combined Photorefractive Keratectomy and Corneal Crosslinking in Keratoconus Suspects

Purpose

To present the long-term outcomes of photorefractive keratectomy (PRK) combined with accelerated corneal cross-linking (CXL) for refractive error correction in a series of keratoconus suspects.

Setting

University practice.

Design

Retrospective case series.

Methods

A series of patients with topographic findings suspicious for keratoconus underwent simultaneous PRK and prophylactic accelerated CXL (5 minutes with intensity of 18 mW/cm²) for the correction of their refractive error. The results were recorded for more than 4 years postoperatively.

Results

Ten eyes of 5 patients were included. Mean follow-up was 58.2 months (range from 54 to 62 months). Mean age at presentation was 25 years (range from 22 to 32 years). Mean spherical equivalent (SE) refraction was −2.76 (standard deviation [SD] 0.97D, range from −1.25 to −4.00 diopters [D]), while mean central corneal thickness was 511μm (SD 13μm, range from 485 to 536 μm). At last, follow-up 9 out of 10 eyes had SE refraction within ± 0.50D and all eyes had SE within ± 1.00D. None of the eyes lost any line of corrected distance visual acuity (CDVA), whereas 1 eye gained one line of CDVA. All eyes demonstrated stability of their results during the follow-up period.

Conclusion

Simultaneous PRK followed by prophylactic accelerated CXL (PRK plus) appeared to be a safe and effective option for the correction of the refractive error in this series of keratoconus suspect patients, without compromising corneal stability for up to 5 years postoperatively.

Evidence of a Down Syndrome Keratopathy: A Three-Dimensional (3-D) Morphogeometric and Volumetric Analysis

The aim of this study was to investigate whether a different and abnormal corneal profile is present in Down syndrome (DS) by personalized three-dimensional (3D) modelling. This single-centre cross-sectional study included 43 patients with DS (43 eyes) and 58 age-sex-matched control subjects (58 eyes) with normal karyotype and topography. Refraction, central corneal thickness (CCT), aberrations (high-order, coma and spherical), asphericity and morphogeometric/volumetric parameters based on a 3D corneal model that was generated from raw topographical data were evaluated. Deviation of anterior/posterior apex (D_apexant/D_apexpost) and thinnest point (D_mctant/D_mctpost) from corneal vertex, anterior/posterior surface area (A_ant/A_post), sagittal area passing through the anterior/posterior apex (A_apexant/A_apexpost) and thinnest point (A_mctpost), total corneal volume (V_total) and volumetric progression for each 0.05 mm step of the radius value centred to the thinnest point (VOL_MCT) and anterior/posterior apex (VOL_AAP/VOL_PAP) comprised the morphogeometric/volumetric parameters. In the DS group, 58.1% of the eyes presented abnormal topography. High-order and coma aberrations, asphericity, D_apexant, A_ant, A_post and A_apexant were significantly higher, whereas CCT, A_apexpost, A_mctpost, V_total, VOL_AAP, VOL_PAP and VOL_MCT were lower in the DS group than in the control group (p < 0.05). D_apexpost did not differ between the groups (p > 0.05). This study demonstrates that corneas of the subjects with DS are different and more aberrated than those of normal age- and sex-matched non-DS controls. Anterior corneal apex appears to be displaced in DS even with normal topography, while posterior apex seems stable although topography is abnormal. These findings may help to modify our approach in the diagnosis of keratopathy in subjects with DS.

Use of new-generation hybrid contact lenses for managing challenging corneas

INTRODUCTION

To evaluate the safety and efficacy of new-generation hybrid contact lenses (HCL) among patients with irregular astigmatism.

METHODS

Medical records of 25 patients fit with new-generation HCL (Eyebrid^® and AirFlex^®) were retrospectively reviewed. The data collected included etiology of irregular astigmatism, uncorrected visual acuity, manifest refraction, spectacle-corrected visual acuity (S-CDVA), steep / flat keratometric values, corneal astigmatism, records of rigid / soft CL fitted before HCL, all parameters of the trial lenses, and the final prescribed HCL parameters and HCL-CDVA.

RESULTS

The study included 34 eyes from 25 patients (nine females and 16 males) with an average age of 29 ± 13 (ranging from 8-56) years. In total, 25 eyes with keratoconus, four with post - keratoplasty astigmatism, three with irregular astigmatism due to corneal trauma and two with residual astigmatism after radial keratotomy were fit with HCL. The mean S-CDVA (logMAR) improved significantly from 0.76 ± 0.41 to 0.14 ± 0.15 with HCL (p < 0.01). The most common indication for HCL was inability to fit with rigid gas permeable (RGP) lenses (22 eyes). The average number of lenses to successful fit was 1.4 (mode, 1; median, 1) and ideal fit was achieved with the first trial lens in 25 eyes (73%). Seven patients (nine eyes, 36%) discontinued lens use within the first 6 months because of discomfort (six eyes, 24%), ocular allergy (two eyes, 8%) and tearing of contact lens (one eye, 4%).

DISCUSSION

New-generation HCL may be a suitable option for fitting challenging corneas with irregular astigmatism that cannot be rehabilitated efficiently with rigid lenses.

High-resolution wavefront-guided surface ablation with corneal cross-linking in ectatic corneas: a pilot study

Purpose

A preliminary study to evaluate the outcomes of high-resolution wavefront-guided (HRWG) photorefractive keratectomy (PRK) with simultaneous corneal cross-linking (CXL) in ectasia eyes.

Methods

Sixteen eyes of 11 patients (mean age 31.9±9.8 years; range: 15–48 years) with keratoconus or post-laser-assisted in situ keratomileusis ectasia underwent HRWG PRK with simultaneous CXL. Manifest refraction, uncorrected (UDVA) and corrected distance visual acuity (CDVA), and keratometric and aberrometric outcomes are reported at 12 months.

Results

Significant improvement was observed postoperatively in visual acuity, refraction, and keratectomy in all eyes. At postoperative 12 months, 87.5% eyes were within ±1.0 D of attempted correction and 81.25% of eyes had a postoperative UDVA of 20/32 or better. A gain of 2 or more lines of CDVA was observed in 12.5% (2/16) of eyes and there was no change in CDVA lines in 25% (4/16) eyes. A substantial reduction in higher-order aberrations was observed in all eyes postoperatively; however, the improvement was not statistically significant.

Conclusion

The outcomes of HRWG PRK in ectasia eyes with estimated residual stromal bed thickness of at least 350 μm (without epithelium) are promising at postoperative 1 year and provide surgeons with a valuable tool to improve vision with a high degree of refractive predictability.

Validity of autorefractor based screening method for irregular astigmatism compared to the corneal topography- a cross sectional study

AIM

To present a method of screening for irregular astigmatism with an autorefractor and its determinants compared to corneal topography.

METHODS

This cross-sectional validity study was conducted in 2013 at an eye hospital in Spain. A tabletop autorefractor (test 1) was used to measure the refractive status of the anterior surface of the cornea at two corneal meridians of each eye. Then corneal topography (test 2) and Bogan's classification was used to group eyes into those with regular or no astigmatism (GRI) and irregular astigmatism (GRII). Test 1 provided a single absolute value for the greatest cylinder difference (Vr). The receiver operating characteristic (ROC) were plotted for the Vr values measured by test 1 for GRI and GRII eyes. On the basis a Vr value of 1.25 D as cut off, sensitivity, specificity were also calculated.

RESULTS

The study sample was comprised of 260 eyes (135 patients). The prevalence of irregular astigmatism was 42% [95% confidence interval (CI): 36, 48]. Based on test 2, there were 151 eyes in GRI and 109 eyes in GRII. The median Vr was 0.75 D (25% quartile, 0.5 D) for GRI and 1.75 D (25% quartile, 1.25 D) for GRII. The area under curve was 0.171 for GRI and 0.83 for GRII. The sensitivity of test I was 78.1% and the specificity was 76.1%.

CONCLUSION

A conventional autorefractor can be effective as a first level screening method to detect irregular corneal astigmatism in places where corneal topography facilities are not available.

Combined femtosecond laser-assisted intracorneal ring segment implantation and corneal collagen cross-linking for correction of keratoconus

Purpose

To assess the safety, predictability, and effectiveness of Keraring intrastromal corneal ring segments (ICRS) insertion assisted by femtosecond laser and corneal collagen cross-linking (CXL) for keratoconus correction.

Patients and methods

In this prospective, noncomparative, and interventional case series, 160 eyes of 100 adult keratoconus patients with poor best-corrected visual acuity (BCVA) (less than 0.7) and intolerance to contact lens wear were included. Patients underwent femtosecond laser-assisted placement of ICRS and CXL. All patients were examined for a complete ophthalmological test: uncorrected visual acuity (UCVA), BCVA, spherical equivalent, keratometry (K1-flat and K2-steep), pachymetry, and Scheimpflug imaging with the Pentacam at 1 week and at 1, 3, and 6 months postoperatively.

Results

At 6 months, a significant difference was observed (P<0.001) in mean UCVA and BCVA from 0.92±0.677 and 0.42±0.600 logMAR preoperatively to 0.20±0.568 and 0.119±0.619 logMAR, respectively. Mean spherical equivalent refractions were significantly lower (P<0.001) at 6 months. Mean keratometry (K) also significantly reduced (P<0.001) from 50.93±5.53 D (K1-flat) and 55.37±5.76 D (K2-steep) to 47.32±4.61 and 51.08±5.38 D, respectively. In terms of pachymetry, no significant difference was observed preoperatively versus postoperatively (P=1.000).

Conclusion

Keraring ICRS insertion assisted by femtosecond laser and corneal CXL provided significant improvement in visual acuity, spherical equivalent, and keratometry, which suggests that it may be effective, safe, and predictable for keratoconus correction.

Effects of rigid contact lenses on optical coherence tomographic parameters in eyes with keratoconus

BACKGROUND

The aim was to evaluate the effect of irregular astigmatism on the retinal nerve fibre layer (RNFL), macular thickness and ganglion cell analysis obtained by spectral domain optical coherence tomography (OCT) in eyes with keratoconus.

METHODS

Fifty-two eyes of 31 patients (20 females) with keratoconus that required correction of irregular astigmatism with rigid gas-permeable (RGP) contact lenses were included to this study. The average, superior, nasal, inferior, temporal and 12 clock hour sector's RNFL, ganglion cell and macular thickness analyses before and 30 minutes after RGP contact lens (Rose K2 -Menicon Z material, David Thomas Contact Lenses Ltd, Northampton, United Kingdom) wear were performed to all patients with Cirrus HD spectral domain optical coherence tomography.

RESULTS

The average thickness of the retinal nerve fibre layer, the thickness at the nasal quadrants and 1-2-3-4 o'clock hour sectors and mean signal strength were increased significantly by RGP contact lens wearing independent of the stage of keratoconus. Central sub-field thickness increased after correction with RGP contact lens (p = 0.037). After wearing RGP contact lenses, changes on ganglion cell analysis were not significant (all p values ≥ 0.111).

CONCLUSIONS

OCT is a widely used device for retinal nerve fibre layer and macular thickness evaluation in patients with glaucoma and macular diseases. The study demonstrates that OCT parameters such as retinal nerve fibre layer, central sub-field thickness and mean signal strength are affected by irregular astigmatism. Correction of irregular astigmatism with RGP contact lenses should be recommended before analysing keratoconic eyes to obtain optimum results on OCT measurements.

The effect of pterygium surgery on wavefront analysis

Background:

Pterygium is a common disorder of the ocular surface. It causes vision impairment -usually irregular type astigmatism- through different mechanisms. In addition, it is believed that surgical excision of the pterygium improves visual problems. The appropriate method to investigate irregular astigmatism is using wavefront analysis. This study was aimed to evaluate wavefront analysis pre and post pterygium surgery.

Materials and Methods:

This study was performed on 32 patients who underwent surgical excision of pterygium in January 2012. Data were recorded and compared after pre and postoperative comprehensive ophthalmologic examinations including uncorrected and best corrected visual acuity, Orbscan, wavefront analysis and autorefraction to figure out the effects of surgery on different parameters.

Results:

Comparison of pre and postoperative parameters showed that surgical treatment of the pterygium improves numerous parameters significantly including uncorrected and best corrected visual acuity, spherical and cylinder refractive error, higher order aberration, quadrafoil (Z440), corneal astigmatism and 3 and 5 mm central zone corneal irregularity (all P-values < 0.0001). In addition, it improves vertical coma (P:0.003) and secondary astigmatism (Z420) (P:0.004).

Conclusion:

It is concluded that surgical excision of the pterygium improves visual acuity, refractive errors and most of the corneal topographic indices and wavefront analysis parameters.

Visual and subjective outcomes of phototherapeutic keratectomy after Descemet's stripping endothelial keratoplasty

Background

Patients with endothelial disease also often have scarring or surface corneal disease. This study examined the outcomes of phototherapeutic keratectomy (PTK) performed in patients with prior Descemet’s stripping endothelial keratoplasty (DSEK).

Methods

This retrospective case series examined all patients undergoing PTK after DSEK in a single private practice. The primary outcome was best-corrected visual acuity, with secondary outcomes of change in spherical equivalent versus targeted change, change in endothelial cell count, improvement in corneal topography, and subjective satisfaction with vision.

Results

For the ten patients who met the inclusion criteria, mean best-corrected visual acuity improved from logarithm of the minimum angle of resolution (logMAR) 0.43 to 0.36 (P=0.24) at the most recent postoperative visit. PTK treatments that included a refractive component showed good predictability of 1.13 diopters spherical equivalent/diopter attempted. There was no evidence of a decrease in endothelial cell count from PTK, even with the use of mitomycin C (P=0.95). Subjectively, 80% of patients noted improvement in their vision.

Conclusion

PTK after DSEK has the potential to improve patients’ vision with high levels of patient satisfaction, even though many patients had significant ocular comorbidities. Surgeons should consider using PTK to treat anterior corneal pathology following DSEK.

Collagen cross-linking with riboflavin and ultraviolet-A light in keratoconus: One-year results

Background:

The aim of this study is to evaluate the safety and effectiveness of riboflavin-ultraviolet type A (UV-A) light rays induced cross-linking of corneal collagen in improving visual acuity and in stabilizing the progression of keratoconic eyes. The method of corneal cross-linking using riboflavin and UV-A light is technically simple and less invasive than all other therapies proposed for keratoconus. It is the only treatment that treats not only the refractive effects of the condition but the underlying pathophysiology.

Materials and Methods:

In this prospective, nonrandomized clinical study, 20 eyes of 19 patients with keratoconus were treated by combined riboflavin UV-A collagen cross linking. The eyes were saturated with riboflavin solution and were subjected for 30 min under UV-A light with a dose parameter of 3 mW/cm². Safety and effectiveness of the treatment was assessed by measuring the uncorrected visual acuity, best corrected visual acuity, manifest cylinder/sphere, keratometry, pachymetry, posterior and anterior elevations from Pentacam and corneal aberrations at 6 months and 1 year post-treatment.

Results:

Comparative analysis of the pre-operative and 1 year post-operative evaluation showed a mean gain of 4.15 lines of UCVA (P= 0.001) and 1.65 lines of BCVA (P= 0.002). The reduction in the average keratometry reading was 1.36 D (P= 0.0004) and 1.4 D (P= 0.001) at the apex. Manifest refraction sphere showed a mean reduction of 1.26 D (P= 0.033) and 1.25 D (0.0003) for manifest cylinder. Topo-aberrometric analysis showed improvement in corneal symmetry.

Conclusion:

Cross-linking was safe and an effective therapeutical option for progressive keratoconus.

High Dk piggyback contact lens system for contact lens-intolerant keratoconus patients

BACKGROUND

The aim of the study was to examine the clinical success of high Dk (oxygen permeability) piggyback contact lens (PBCL) systems for the correction of contact lens intolerant keratoconus patients.

METHODS

Sixteen patients (29 eyes) who were not able to wear gas-permeable rigid lenses were included in this study. Hyper Dk silicone hydrogel (oxygen transmissibility or Dk/t = 150 units) and fluorosilicone methacrylate copolymer (Dk/t = 100 units) lenses were chosen as the PBCL systems. The clinical examinations included visual acuity and corneal observation by biomicroscopy, keratometer reading, and fluorescein staining before and after fitting the PBCL system.

RESULTS

INDICATIONS FOR USING PBCL SYSTEM WERE: lens stabilization and comfort, improving comfort, and adding protection to the cone. Visual acuities increased significantly in all of the patients compared with spectacles (P = 0). Improvement in visual acuity compared with rigid lenses alone was recorded in 89.7% of eyes and no alteration of the visual acuity was observed in 10.3% of the eyes. Wearing time of PBCL systems for most of the patients was limited time (mean 6 months, range 3-12 months); thereafter they tolerated rigid lenses alone except for 2 patients.

CONCLUSION

The PBCL system is a safe and effective method to provide centering and corneal protection against mechanical trauma by the rigid lenses for keratoconus patients and may increase contact lens tolerance.