Effects of corneal irregular astigmatism on visual acuity after conventional and femtosecond laser-assisted Descemet's stripping automated endothelial keratoplasty

Corneal higher-order aberrations in corneal endothelial decompensation secondary to obstetric forceps injury

Forceps corneal injuries during infant delivery cause Descemet membrane (DM) breaks, that cause corneal astigmatism and corneal endothelial decompensation. The aim of this study is to characterise corneal higher-order aberrations (HOAs) and corneal topographic patterns in corneal endothelial decompensation due to obstetric forceps injury. This retrospective study included 23 eyes of 21 patients (54.0 ± 9.0 years old) with forceps corneal injury, and 18 healthy controls. HOAs and coma aberrations were significantly larger in forceps injury (1.05 [0.76-1.98] μm, and 0.83 [0.58-1.69], respectively) than in healthy controls (0.10 [0.08-0.11], and 0.06 [0.05-0.07], respectively, both P < 0.0001). Patient visual acuity was positively correlated with coma aberration (r_s = 0.482, P = 0.023). The most common topographic patterns were those of protrusion and regular astigmatism (both, six eyes, 26.1%), followed by asymmetric (five eyes, 21.7%), and flattening (four eyes, 17.4%). These results indicate that increased corneal HOAs are associated with decreased visual acuity in corneal endothelial decompensation with DM breaks and corneal topography exhibits various patterns in forceps injury.

Penetrating Keratoplasty Versus Descemet Stripping Automated Endothelial Keratoplasty in Children With Congenital Hereditary Endothelial Dystrophy: Long-Term Results

PURPOSE

The purpose of this study was to compare the outcomes of Descemet stripping automated endothelial keratoplasty (DSAEK) and penetrating keratoplasty (PKP) in patients with congenital hereditary endothelial dystrophy (CHED).

METHODS

This was a retrospective, comparative study of all the patients with a histopathological diagnosis of CHED who underwent PKP or DSAEK between January 1, 1990, and December 31, 2016. All the cases were included except those patients who had clear grafts but did not complete 2 years of postoperative follow-up. The main outcome measure was graft clarity 2 years after surgery.

RESULTS

There were 111 eyes of 63 patients. Seventy-six eyes underwent PKP, and 35 eyes underwent DSAEK. The median age at surgery was 6.8 years in the PKP group and 10.32 years in the DSAEK group. At 2 years postoperatively, clear grafts were noted in 66 of 76 (86.8%) eyes in the PKP group and 30 of 35 (85.7%) eyes in the DSAEK group. At the last follow-up, 80.3% of PKP grafts and 82.8% of DSAEK grafts were clear ( P =0.5). The type and timing of complications differed between the 2 groups. The PKP group had a statistically significant higher rate of graft rejection (19.5%) versus the DSAEK group (0%) ( P =0.01). DSAEK complications were mainly lenticule detachment that developed within one month postoperatively. There was no statistically significant difference in the visual outcomes at the last follow-up between the groups.

CONCLUSION

Endothelial keratoplasty is a safe alternative to conventional PKP in CHED. The visual outcome and survival rates were comparable, but DSAEK had a lower rejection rate and fewer suture-related complications.

SMILE after DALK to reduce residual refraction: two-year results

PURPOSE

To determine the two-year results of small incision lenticule extraction (SMILE) for correcting post-keratoplasty myopia and myopic astigmatism.

METHODS

In this case-series study, 10 eyes of 10 patients with a 6- to 10-year history of successful deep lamellar keratoplasty (DALK) underwent SMILE using the VisuMax laser platform. Ophthalmologic examinations and visual acuity and refraction measurement were taken pre- and 1, 3, 6, 12, and 24 months postoperatively. The Pentacam and Sirius imaging were done in the first and last follow-up sessions.

RESULTS

The mean age of the patients was 39.60 ± 7.86 years. Six subjects were male. Two years after SMILE, the mean improvement in UDVA and CDVA was 3.60 ± 1.84 (P < 0.001) and 1.60 ± 2.91 (P = 0.231) LogMAR, respectively. The mean decrease in spherical equivalent, spherical error, and cylinder power was 1.92 ± 1.96 diopter (D) (P = 0.013), 0.70 ± 3.05D (P = 0.213), and 2.42 ± 2.91D (P = 0.024), respectively. The vector mean target-induced astigmatism, surgical-induced astigmatism, and difference vector were 1.30D@44˚, 1.11D@24˚, and 0.86D@73˚, respectively. Two years after SMILE, vertical coma, horizontal coma, and spherical aberration increased by 0.44 ± 0.51, 0.23 ± 0.32, and 0.02 ± 0.16 µm, respectively, (all P > 0.05) while trefoil reduced by 0.29 ± 0.75 µm (P = 0.428).

CONCLUSION

SMILE can be an effective procedure for reducing refraction and astigmatism after DALK in patients with moderate myopia and moderate to severe astigmatism and improves the visual acuity in these patients. Axis rotation during surgery may result in under-correction of astigmatism. Refinement of SMILE treatment nomogram for post-DALK cases seems necessary.

Efficacy of Thin and Ultrathin Descemet Stripping Automated Endothelial Keratoplasty and Influence of Graft Thickness on Postoperative Outcomes: Systematic Review and Meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis on the efficacy of thin and ultrathin Descemet stripping automated endothelial keratoplasty (T-DSAEK and UT-DSAEK, with graft thickness <130 and <100 µm, respectively), depending on graft thickness.

DESIGN

Systematic review and meta-analysis.

METHOD

PubMed, Cochrane Library, Embase, ClinicalTrials.gov, and ScienceDirect databases were searched until October 1, 2021. We computed random-effect meta-analysis on postoperative outcomes of T/UT-DSAEK, stratified by graft thickness (<80 μm, 80-100 μm, and 100-130 μm). The main postoperative outcome was visual acuity (logarithm of the minimum angle of resolution [logMAR]). Secondary outcomes were pachymetry (μm), endothelial cell count (cell/mm²), spherical equivalent (diopter [D]), rebubbling rate (%), and rejection rate (%). Meta-regressions compared postoperative outcomes depending on graft thickness and search for putative confusion factors.

RESULTS

We included 47 articles for a total of 2141 eyes of 2040 patients. T/UT-DSAEK globally improved visual acuity (effect size = -0.38 logMAR [95% confidence interval {CI} -0.46 to -0.30 logMAR]), without difference depending on graft thickness. Overall, pachymetry improved (-60.6 µm [95% CI -101 to -19.7 µm]), endothelial cell count decreased (-1039 cells/mm² [95% CI -1209 to -868 cells/mm²), spherical equivalent resulted in a hyperopic shift (0.74 D [95% CI -0.50 to 1.97 D), the graft rejection rate was 0.2% (95% CI -0.1% to 0.4%), and the rebubbling rate was 8.7% (95% CI 6.8%-10.5%). Grafts >100 μm induced a hyperopic shift. Metaregressions did not demonstrate differences between the 3 groups (<80 μm, 80-100 μm, or 100-130 μm) in any outcomes.

CONCLUSION

All T/UT-DSAEK thickness groups provided similar visual acuity, pachymetry, endothelial cell count, rejection rate, and rebubbling rate regardless of graft thickness. A hyperopic shift was induced by grafts >100 μm.

Corneal higher-order aberrations in phlyctenular keratitis

PURPOSE

To characterize tomographic patterns and quantify corneal higher-order aberrations (HOAs) in eyes with corneal scar due to phlyctenular keratitis.

STUDY DESIGN

Retrospective consecutive case series.

METHODS

This study included 51 eyes of 38 patients (24 women; 14 men) with corneal scar due to phlyctenular keratitis. HOAs of the total cornea, and of the anterior and posterior surfaces were measured using anterior segment optical coherence tomography (AS-OCT). Corneal tomographic patterns were classified into five types: increased regular astigmatism, ectasia, asymmetric, flattening and minimal change patterns. The correlation between corneal HOAs and visual acuity was evaluated.

RESULTS

Mean months from onset was 50.7 ± 74.7 and mean number of recurrences 2.1 ± 1.1 (1-5). Mean logarithm of the minimal angle of resolution (logMAR) was 0.19 ± 0.31. AS-OCT showed ectasia pattern in 16 eyes (31.4%), asymmetric pattern in 12 eyes (23.5%), increased regular astigmatism pattern in 9 eyes (17.6%), flattening pattern in 3 eyes (5.9%) and minimal change pattern in 11 eyes (21.6%). HOAs of the total cornea were 0.57 ± 0.44 μm and 1.16 ± 0.77 μm within a 4-mm and 6-mm diameter, significantly larger than in normal controls (P < 0.0001). LogMAR visual acuity was significantly correlated with corneal HOAs (4-mm: r = 0.558, P < 0.0001, 6-mm: r = 0.566, P < 0.0001), central corneal thickness (r = - 0.349, P = 0.016), and corneal astigmatism (r = 0.414, P = 0.004), but not with average keratometric value (r = - 0.092, P = 0.537).

CONCLUSIONS

The most common tomographic pattern was ectasia, followed by a asymmetric pattern in eyes with phlyctenular keratitis. Corneal HOAs were associated with decreased visual acuity in phlyctenular keratitis patients.

Comparison of Artificial Anterior Chamber Internal Pressures and Cutting Systems for Descemet's Stripping Automated Endothelial Keratoplasty

Purpose

To optimize methods of preparing donor cornea tissue for Descemet's stripping automated endothelial keratoplasty (DSAEK), we compared five experimental conditions with different internal pressures and cutting systems.

Methods

The artificial anterior chamber internal pressure (IP) was set at 100 or 200 mm Hg. The microkeratome cut was performed with or without an artificial chamber pressurizer (ACP), using a CBm turbine (CBm) or one use-plus automated (OUP-A). Thirty human research corneas were divided into five groups, and compared after the cut with donor tissue quality parameters, including cutting depth, graft uniformity, cell evaluation, and smoothness of the stromal surface.

Results

The smallest variation in mean cut depth was observed in the condition, which had IP of 200 mm Hg used ACP and OUP-A. In experimental groups cut using CBm, significantly more consistent thicknesses were made at an IP of 200 than 100 mm Hg. There were no statistically significant differences among the groups in either endothelial cell density or cell viable assay results after cuts. Using an IP of 200 mm Hg with ACP and CBm produced the roughest stromal surface, and the roughness grading scores showed a positive correlation with the percentage of cut depth.

Conclusions

An IP of 200 mm Hg was the best setting for DSAEK grafts with high predictability of cut depth and uniformity of graft thickness without endothelial cell damage.

Translational Relevance

For successful DSAEK, it is recommended that a set internal pressure of 200 mm Hg be used during microkeratome cutting for donor tissue preparation.

Lamellar keratoplasty techniques

Lamellar keratoplasty (LK) has revolutionized corneal graft surgery in several ways. Deep anterior LK (DALK) has eliminated risk of failure due to endothelial rejection. Endothelial keratoplasty (EK) has almost eliminated induced astigmatism and the “weak” graft–host junction as seen with penetrating keratoplasty (PK) and also reduced the risk of endothelial rejection. LK provided new insights into posterior corneal anatomy that led to better understanding and performance of DALK and to the development of another EK procedure, namely pre-Descemet's EK (PDEK). Surgical procedures for LK were further refined based on the improved understanding and are able to deliver better surgical outcomes in terms of structural integrity and long-term patient satisfaction, reducing the need of further surgeries and minimizing patient discomfort. In most specialist centers, anterior lamellar techniques like DALK and EK techniques like Descemet's stripping EK (DSEK) and Descemet's membrane EK (DMEK) have replaced the full-thickness PK where possible. The introduction of microkeratome, femtosecond laser, and PDEK clamp have made LK techniques easier and more predictable and have led to the innovation of another LK procedure, namely Bowman membrane transplant (BMT). In this article, we discuss the evolution of different surgical techniques, their principles, main outcomes, and limitations. To date, experience with BMT is limited, but DALK has become the gold standard for anterior LK. The EK procedures too have undergone a rapid transition from DSEK to DMEK and PDEK emerging as a viable option. Ultrathin-DSEK may still have a role in modern EK.

Comparison of four methods of surface roughness assessment of corneal stromal bed after lamellar cutting

Corneal lamellar cutting with a blade or femtosecond laser (FSL) is commonly used during refractive surgery and corneal grafts. Surface roughness of the cutting plane influences postoperative visual acuity but is difficult to assess reliably. For the first time, we compared chromatic confocal microscopy (CCM) with scanning electron microscopy, atomic force microscopy (AFM) and focus-variation microscopy (FVM) to characterize surfaces of variable roughness after FSL cutting. The small area allowed by AFM hinders conclusive roughness analysis, especially with irregular cuts. FVM does not always differentiate between smooth and rough surfaces. Finally, CCM allows analysis of large surfaces and differentiates between surface states.

Corneal Higher-Order Aberrations in Infectious Keratitis

PURPOSE

To characterize the corneal higher-order aberrations (HOAs) in eyes with Acanthamoeba keratitis (AK), bacterial keratitis (BK), and fungal keratitis (FK).

DESIGN

Retrospective consecutive case series.

METHODS

This retrospective study includes 18 normal subjects and 63 eyes of 62 consecutive patients with corneal scarring due to AK (20 eyes), BK (35 eyes), and FK (8 eyes) from 2010 to 2016. HOAs of the anterior and posterior surfaces and the total cornea were analyzed by anterior segment optical coherence tomography. Corneal HOA patterns were assigned on the basis of corneal topography maps. Corneal opacity grading was assigned on the basis of slit-lamp examinations. We evaluated corneal HOAs, corneal opacity grading, and their correlation with visual acuity.

RESULTS

HOAs of the total cornea within a 4-mm diameter were significantly larger in eyes with infectious keratitis (AK, 1.15 ± 2.06 μm; BK, 0.91 ± 0.88 μm; FK, 1.39 ± 1.46 μm) compared with normal controls (0.09 ± 0.01 μm, all, P < .001). Asymmetric pattern was the most common topographic pattern (30% in AK, 51.4% in BK, and 37.5% in FK), followed by the protrusion patterns (10% in AK, 20% in BK, and 12.5% in FK). The visual acuity significantly correlated with HOAs (anterior surface: R = 0.764, P < .0001; posterior surface: R = 0.745, P < .0001; total cornea: R = 0.669, P < .0001).

CONCLUSIONS

Larger corneal HOAs in patients with infectious keratitis were associated with poorer visual acuity values. Asymmetric pattern was the most common topographic pattern in infectious keratitis.

Corneal Higher Order Aberrations in Granular, Lattice and Macular Corneal Dystrophies

Purpose

To evaluate the corneal higher-order aberrations (HOAs) in granular, lattice and macular corneal dystrophies.

Methods

This retrospective study includes consecutive patients who were diagnosed as granular corneal dystrophy type2 (GCD2; 121 eyes), lattice corneal dystrophies type 1, type 3A (LCDI; 20 eyes, LCDIIIA; 32 eyes) and macular corneal dystrophies (MCD; 13 eyes), and 18 healthy control eyes. Corneal HOAs were calculated using anterior segment optical coherence tomography, and the correlations between HOAs and visual acuity were analyzed.

Results

HOAs of the total cornea within 4 mm diameter were significantly larger in GCD2 (0.17 ± 0.35 μm), in LCDI (0.33 ± 0.27), LCDIIIA (0.61 ± 1.56) and in MCD (0.23 ± 0.18), compared with healthy controls (0.09 ± 0.02μm, all P < 0.01). HOAs of the total cornea within 6 mm diameter were significantly larger in GCD2 (0.32 ± 0.48), in LCDI (0.60 ± 0.46), LCDIIIA (0.83 ± 2.29) and in MCD (0.44 ± 0.24), compared with healthy controls (0.19 ± 0.06, all P < 0.001). In GCD2, there was no significant correlation between logMAR and HOAs (r = 0.113, P = 0.227). In MCD, LCDI and LCDIIIA, logMAR was positively significantly correlated with HOAs (r = 0.620 and P = 0.028, r = 0.587 and P = 0.007, r = 0.614 and P < 0.001, respectively).

Conclusions

Increased HOAs occur in eyes with corneal dystrophies, especially in eye with LCD and MCD. Larger amount corneal HOAs are associated with poorer visual acuity in patients with LCD and MCD.