Intraocular lens power calculation using standard formulas and ray tracing after DMEK in patients with Fuchs endothelial dystrophy.

BACKGROUND: The study presented here aims to optimize the accuracy of intraocular lens (IOL) power calculations in patients after DMEK by evaluation of the impact of the altered anterior/posterior corneal curvature relationship. METHODS: Scheimpflug-based Oculus Pentacam imaging was performed after DMEK surgery for Fuchs endothelial dystrophy. The IOL power was calculated for all patients by ray tracing, aiming for postoperative emmetropia. We also performed the IOL calculation using four third-generation formulas (SRK-T, Hoffer-Q, Holladay-1 and Haigis). The residual refractions for the individual target IOL were compared and analyzed. RESULTS: This retrospective study included 42 eyes of 33 patients (age 68.73 ± 10.11 years) after DMEK surgery. The differences between the expected residual refraction based on ray tracing and that predicted with the third-generation formulas were statistically significant (all formulas p < 0.001). The highest mean difference in the residual refraction between the target IOL measured by ray tracing and that calculated with third-generation formulas was found for the Haigis formula (0.90 ± 0.40 D), and the lowest mean difference for the SRK/T formula (0.73 ± 0.49 D). CONCLUSIONS: DMEK surgery induced a relevant change in the anterior to posterior corneal curvature relationship; this needs to be taken into account in the IOL power calculation to avoid hyperopic refractive surprises.

Changes in Anterior, Posterior, and Total Corneal Astigmatism after Descemet Membrane Endothelial Keratoplasty.

Purpose. To evaluate changes in anterior, posterior, and total corneal astigmatism in patients after Descemet membrane endothelial keratoplasty (DMEK). Methods. We retrospectively included 29 eyes of 23 patients (age 67.6 ± 9.8 years, 13 female, 10 male) after DMEK surgery. The magnitude and axis orientation of anterior, posterior, and total corneal astigmatism before and after DMEK were determined using a rotating Scheimpflug system (Pentacam HR, Oculus). Results. The magnitude of anterior, posterior, and total corneal astigmatism in the central cornea did not change significantly after surgery. Before surgery, we found a significant correlation between the magnitudes of anterior and posterior corneal astigmatism (Spearman's correlation coefficient (rS) = 0.526, P = 0.003), while after surgery this correlation was no longer significant (rS = 0.038, P = 0.843). There was a significant correlation between the vector difference between preoperative and postoperative posterior astigmatism and the change in corneal pachymetry (rP = 0.47, P = 0.010). Conclusions. Posterior corneal astigmatism (especially the orientation) and therefore the relationship between anterior and total corneal astigmatism may change after DMEK. This should be considered to improve the accuracy of toric IOL power calculations following phakic DMEK or in combined procedures.

Changes in Corneal Densitometry in Patients with Fuchs Endothelial Dystrophy after Endothelial Keratoplasty.

PURPOSE: The aim of the study was to quantify corneal densitometry in patients with Fuchs endothelial dystrophy (FED) after endothelial keratoplasty. MATERIALS AND METHODS: We retrospectively reviewed the charts and anterior segment data of patients with FED before and after endothelial keratoplasty. Patients were examined using the Scheimpflug-based Oculus Pentacam corneal densitometry module. Densitometry parameters in different corneal layers and in different annuli were extracted and analyzed. RESULTS: 27 eyes of 27 patients after endothelial keratoplasty (11 DSAEK, 16 DMEK) were included. After endothelial keratoplasty the total corneal light backscatter at total corneal thickness in the central cornea (0-2 mm annulus) was significantly lower than before (DSAEK: p = 0.026, DMEK: p = 0.001). In the entire group the total corneal light backscatter at total corneal thickness and at total diameter before surgery correlated with the postoperative values (Pearson correlation = 0.49, p = 0.01). The strongest correlation was found in the central layer in the DMEK group (Pearson correlation = 0.79, p < 0.001). CONCLUSIONS: Corneal densitometry is a useful, objective method for quantification of the outcome of posterior lamellar keratoplasty irrespective of visual acuity. There is a significant correlation between preoperative and postoperative corneal light backscatter values after endothelial keratoplasty, especially in the case of the DMEK procedure.

Corneal Densitometry as a Novel Technique for Monitoring Amiodarone Therapy.

PURPOSE: The clinical efficacy and toxicity of amiodarone may be determined more effectively by tissue deposition than by levels of the agent in serum. Therefore, corneal densitometry might be useful for therapeutic monitoring. The aim of the study is to evaluate Scheimpflug corneal densitometry in patients with amiodarone keratopathy (AK). DESIGN: Comparative case series. PARTICIPANTS: Sixty-six patients receiving amiodarone therapy and 66 healthy controls were consecutively enrolled in this study. METHODS: Patients were examined using the Oculus Pentacam (Wetzlar, Germany). MAIN OUTCOME MEASURES: Densitometry data from different corneal layers and different annuli were extracted, analyzed, and compared with densitometry values of healthy controls. Duration of treatment, cumulative dose, Orlando stage (slit-lamp biomicroscopy), and serum concentrations of amiodarone and N-desethylamiodarone also were determined, and the correlation to different densitometry data was evaluated. RESULTS: The total corneal light backscatter at total corneal thickness and at total diameter was significantly higher in the amiodarone group compared with the control group (AK group: 28.3±5.2; control group: 24.4±4.2; P < 0.001). Upon dividing the corneal surface into different layers at total thickness, the differences were significant in all layers (P < 0.001). The serum concentrations of the metabolite N-desethylamiodarone correlate with densitometry values, especially in the 0- to 2-mm annulus in the anterior layer (r = 0.419; P = 0.001), whereas the cumulative dose and duration of treatment correlate significantly with the densitometry values in the 0- to 2-mm annulus at total thickness (P = 0.014 and P = 0.022, respectively). CONCLUSIONS: Corneal densitometry is a useful, objective method for quantifying AK and can help in monitoring amiodarone therapy. The serum concentration of the active metabolite N-desethylamiodarone correlates with the extent of keratopathy in the anterior layer, whereas chronic changes in the stroma correlate with the cumulative dose and duration of treatment.

Changes in Corneal Refractive Power for Patients With Fuchs Endothelial Dystrophy After DMEK.

PURPOSE: To quantify changes in the refractive power of the anterior and posterior corneal surfaces after Descemet membrane endothelial keratoplasty (DMEK) so as to optimize the accuracy of intraocular lens (IOL) power calculations. METHODS: This study included 28 eyes of 21 patients (age 66.6 ± 9.4 years, 11 female, 10 male). Scheimpflug-based Oculus Pentacam imaging was performed before and after DMEK surgery for Fuchs endothelial dystrophy. Corneal power was measured using the K-value of simulated keratometry (SimK) of Pentacam and total corneal refractive power (TCRP) in corneal zones from 1 to 8 mm (SimK 1-8, TCRP1-8). We also analyzed changes in the keratometric power deviation (KPD) and pachymetry. RESULTS: Changes in the SimK in the central cornea were minimal and not significant (SimK 3: before = 43.24 ± 1.33 D; after = 43.01 ± 1.37 D; P = 0.101) but they decreased significantly in the corneal periphery (SimK 4: P = 0.021; SimK 5: P = 0.004; SimK 6: P = 0.002; SimK 7: P = 0.002; SimK 8: P = 0.008). Postoperative TCRP in the central cornea decreased significantly compared with preoperative values (TCRP 3: before = 43.05 ± 1.44 D; after = 41.94 ± 1.34 D; P < 0.001); [TCRP 4: before = 43.16 ± 1.40 (D); after = 41.99 ± 1.27 (D); P < 0.001]. The keratometric power deviation increased significantly after DMEK (before = 0.74 ± 0.45 D; after = 1.40 ± 0.26 D; P < 0.001). CONCLUSIONS: DMEK surgery induced a significant change in the refractive power of the posterior surface of the cornea and thus a decrease in the TCRP of about 1 D, whereas the SimK, which measures only the anterior cornea, remained nearly unchanged. To avoid a hyperopic surprise, it is essential that this TCRP decrease is not overlooked in intraocular lens power calculations.

Corneal Densitometry, Central Corneal Thickness, and Corneal Central-to-Peripheral Thickness Ratio in Patients With Fuchs Endothelial Dystrophy.

PURPOSE: The aim of the study was to quantify Scheimpflug corneal densitometry in patients with Fuchs endothelial dystrophy (FED). METHODS: In this study, we retrospectively reviewed the charts and anterior segment data of 49 patients with FED before posterior lamellar keratoplasty and 51 healthy controls. The patients were examined using the Scheimpflug-based Oculus Pentacam. Central corneal thickness (CCT), ring-averaged (on a circle of 2, 2.4-10 mm diameter) noncentral corneal thickness, and densitometry data in different corneal layers and in different annuli were extracted and analyzed. RESULTS: The total corneal light backscatter at total corneal thickness (CT) and at total diameter was significantly higher in the FED group when compared with the control group (FED group: 28.8 ± 6.7; control group: 24.3 ± 4.1; P < 0.001). When the corneal surface was divided into concentric annular zones at total CT, the differences were significant only in the 2 central annuli (P < 0.001). The total corneal light backscatter at total CT in the central 0-2 mm annulus correlated moderately with the central corneal thickness (Pearson's correlation = 0.55, P < 0.001). CONCLUSIONS: Corneal light backscatter in the central cornea was greater in patients with FED than in normal subjects. Corneal densitometry enables us to evaluate the optical quality of the cornea in different corneal layers and in different annuli. It is a useful, objective method that, in combination with central corneal thickness and corneal central-to-peripheral thickness ratio, can help to quantify FED severity.

Changes in Corneal Transparency After Cross-linking for Progressive Keratoconus: Long-term Follow-up.

PURPOSE: To determine long-term changes in corneal transparency after riboflavin-ultraviolet A-induced corneal collagen cross-linking (CXL). METHODS: Charts and anterior segment data of patients after CXL for progressive keratoconus were retrospectively reviewed. Patients were examined using the Scheimpflug-based Pentacam corneal densitometry module (Oculus Optikgeräte, Wetzlar, Germany) before CXL and at five postoperative follow-up visits: 1 to 3, 3 to 6, 6 to 12, 12 to 24, and 24 to 36 months. RESULTS: Forty-two eyes of 28 patients (mean age: 27.9 ± 8.6 years) were included. Total corneal light backscatter was higher 1 to 3 months after CXL than before CXL (P < .001). There were significant differences, especially in the anterior (P < .001) and central (P < .001) layer at total diameter and posterior layer (P = .014) and the three central annuli at total corneal thickness (0 to 2 mm: P < .001; 2 to 6 mm: P < .001; 6 to 10 mm: P = .002). Total corneal light backscatter at total corneal thickness and total diameter faded over time following CXL. The backscatter was significantly lower 24 to 36 months after CXL than before CXL (P < .001). CONCLUSIONS: Corneal densitometry peaks in the first months after CXL and returns to preoperative values approximately 1 year after CXL. Two years after CXL, corneal densitometry reaches values obtained for healthy, untreated corneas, thus achieving an improvement in corneal clarity over untreated keratoconic corneas.

Accelerated (18 mW/cm²) Corneal Collagen Cross-Linking for Progressive Keratoconus.

PURPOSE: The aim of this study was to determine the efficacy of accelerated riboflavin-ultraviolet A-induced corneal collagen cross-linking (CXL) (irradiance of 18 mW/cm² for 5 minutes). METHODS: In this study, we retrospectively reviewed the charts and anterior segment data of patients after accelerated CXL. Visual, topographic, pachymetry, and densitometry data were extracted and analyzed before surgery and at follow-up (minimum 12 months) after treatment. RESULTS: A total of 28 eyes of 20 patients (mean age, 28.1 ± 8.1 years) were included in this study. The mean follow-up time was 21.7 ± 7.2 months (range, 12-34 months). No statistically significant changes were found in the mean corrected distance visual acuity, corneal astigmatism, Kmean, Kflat, Ksteep, corneal pachymetry (at the apex and at the thinnest point), and corneal densitometry at follow-up. A significant reduction of Kmax, index of surface variance, index of vertical asymmetry, and Km of the posterior corneal surface (Km(B)) was observed (Kmax: P = 0.018; index of surface variance: P = 0.016; index of vertical asymmetry: P = 0.038; Km(B): P = 0.008). No complications were reported during the postoperative follow-up period in this study. CONCLUSIONS: Based on a mean follow-up time of 21.7 months, accelerated CXL (18 mW/cm; 5 minutes) is effective in stopping the progression of keratoconus without raising any safety concerns. Improvement in Kmax and stabilization of corrected distance visual acuity were noted after treatment. However, prospective studies with longer follow-up using different accelerated CXL settings are needed to validate these findings.

Closed-globe injuries of the ocular surface associated with combat blast exposure.

PURPOSE: To describe closed-globe conjunctival and corneal injuries and endothelial cell abnormalities associated with blast exposure and their relationships to other closed-globe injuries and blast-event characteristics. DESIGN: Observational cross-sectional study. PARTICIPANTS: Veterans with a history of blast-related traumatic brain injury (TBI). METHODS: History and ocular examination, including slit-lamp biomicroscopy, gonioscopy, specular microscopy. MAIN OUTCOME MEASURES: Type and location of blast injuries to the conjunctiva and cornea. RESULTS: Ocular surface injuries were present in 25% (16 of 65) of blast-exposed veterans with TBI. Injuries included partial-thickness anterior stromal corneal scars (15 eyes), Descemet membrane ruptures (6 eyes), and conjunctival or corneal foreign bodies (7 eyes). Based on normative information from an age-matched comparison group, endothelial cell abnormalities were identified in 37% of participants. Eyes with ocular surface injury were more likely to have lower endothelial cell density, higher coefficient of variation of cell area, and lower percentage of hexagonal cells compared with eyes without injury. Presence of ocular surface injury or endothelial cell abnormalities was associated with elevated rates of other anterior and posterior segment injuries, as well as impairment of visual acuity. We found no relationship between ballistic eyewear use or severity level of TBI and presence of ocular surface injuries from blast. CONCLUSIONS: Independent of TBI severity or use of protective eyewear, ocular surface injuries and endothelial cell abnormalities were found in significant numbers of veterans with blast-related brain injury. Descemet membrane ruptures from blast exposure were described. Ocular surface trauma was associated with other ocular injuries throughout the globe. Potential mechanisms for the types and locations of ocular injuries seen were discussed. Any corneal or conjunctival injury in a blast survivor should prompt a thorough ocular trauma examination, including gonioscopy and specular microscopy, with appropriate follow-up for associated injuries. Longitudinal studies are required to determine long-term visual outcomes after blast exposure.

Visual performance and the ocular surface in traumatic brain injury.

The pathophysiology of neurotrauma is reviewed and an original study investigating the prevalence of dry eye disease in a sample of veterans with traumatic brain injury (TBI) is presented. Fifty-three veterans with TBI were evaluated by history of injury, past ocular history, and medication use. Ocular Disease Surface Index (OSDI), ocular examination, cranial nerve evaluation, tear osmolarity, tear film break-up time (TFBUT), ocular surface staining and tear production testing were performed. A matched comparison group underwent similar testing. TBI causes were blast (44) or non-blast (9). TBI subjects scored significantly worse on the OSDI (P<.001), and ocular surface staining by Oxford scale (P<.001) than non-TBI subjects. Scores for tear film breakup (P=.6), basal tear production less than 3 mm (P=.13), and tear osmolarity greater than 314 mOsm/L (P=.15) were all higher in TBI subjects; significantly more TBI subjects had at least one abnormal dry eye measure than comparisons (P<.001). The OSDI related to presence of dry eye symptoms (P<.01). These effects were present in both blast and non-blast TBI. Seventy percent of TBI subjects were taking at least one medication in the following classes: antidepressant, atypical antipsychotic, anticonvulsant, or h1-antihistamine. There was no association between any medication class and the OSDI or dry eye measures. Reduced corneal sensation in 21 TBI subjects was not associated with OSDI, tear production, or TFBUT, but did correlate with reduced tear osmolarity (P=.05). History of refractive surgery, previous contact lens wear, facial nerve weakness, or meibomian gland dysfunction was not associated with DED. In summary, we found a higher prevalence of DED in subjects with TBI, both subjectively and objectively. This effect is unrelated to medication use, and it may persist for months to years. We recommend that patients with TBI from any cause be evaluated for DED using a battery of standard testing methods described in a protocol presented in this article. Further research into the pathophysiology and outcomes of DED in neurotrauma is needed.