Corneal wavefront-guided customized laser in situ keratomileusis after penetrating keratoplasty.

PURPOSE: To assess the efficacy and safety of corneal wavefront-guided custom laser in situ keratomileusis (LASIK) to correct refractive errors and higher-order aberrations (HOAs) after penetrating keratoplasty (PKP). SETTING: Beyoglu Eye Training and Research Hospital, Istanbul, Turkey. DESIGN: Noncomparative case series. METHODS: The study comprised consecutive patients who were unable to tolerate spectacles or contact lenses for the correction of anisometropia after PKP and had corneal wavefront-guided custom LASIK. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction spherical equivalent (MRSE), and corneal HOAs were recorded before and after LASIK. RESULTS: The study evaluated 11 eyes (10 patients). The mean follow-up after LASIK was 24.3 months ± 11.7 (SD) (range 9 to 36 months). The mean MRSE was -2.97 ± 1.66 diopters (D) (range -0.50 to -5.38 D) preoperatively and -0.88 ± 0.96 D (range -2.75 to 0.5 D) postoperatively. The mean total higher-order root mean square (RMS) was 4.65 ± 1.14 µm (range 2.26 to 5.94 µm) preoperatively and 2.71 ± 1.31 µm (range 1.22 to 5.33 µm) postoperatively. Postoperatively, the UDVA improved in 7 eyes and remained unchanged in 4 eyes. The CDVA improved in all eyes postoperatively even cases in which the attempted astigmatic correction was not totally achieved. CONCLUSIONS: Corneal wavefront-guided custom LASIK after PKP did not totally correct both refractive errors and HOAs because of the high volume of laser ablation required and inadequate corneal stromal thickness.

Comparison of non-contact methods for the measurement of central corneal thickness.

BACKGROUND AND OBJECTIVE: This study examined the repeatability of and agreements between central corneal thickness measurements obtained by four different non-contact pachymetry devices. PATIENTS AND METHODS: Seventy-eight eyes of 39 subjects were included. Central corneal thickness of each eye was measured by Visante optical coherence tomography (OCT) (Carl Zeiss Meditec Inc., Dublin, CA), Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany), Orbscan IIz topography (Bausch & Lomb Surgical Inc., San Dimas, CA), and slit-lamp OCT (SL-OCT) (Heidelberg Engineering GmbH, Heidelberg, Germany). Inter-device agreements and correlations and repeatability of each device were examined. RESULTS: All measurement methods correlated well with each other with a correlation coefficient greater than 0.90 and P value of less than .001 for all comparisons. However, Pentacam overestimated central corneal thickness: 546.7 ± 38.2, 535.5 ± 42.7, 531.7 ± 37.6, and 531.2 ± 36.0 µm for Pentacam, Orbscan IIz, Visante OCT, and SL-OCT, respectively (P < .001 for all comparisons versus Pentacam). Despite good correlation, magnitude of differences was high and this bias was proportional (ie, not constant across a range of corneal thickness values) for the following pairs: Orbscan versus Visante OCT, Orbscan versus SL-OCT, and Orbscan versus Pentacam (P < .001 for all comparisons). CONCLUSION: Although measurements obtained by various non-contact methods correlate well, numerical agreement of the results may not be sufficient for their interchangeable use in clinical practice.

Corneal biomechanical properties of patients with pseudoexfoliation syndrome.

PURPOSE: To assess the corneal biomechanical properties of patients with pseudoexfoliation syndrome (PEX syndrome). METHODS: Fifty-two eyes of 52 patients (27 unilateral and 25 bilateral) and 42 eyes of 42 age-matched control subjects were enrolled in the study. Metrics of corneal biomechanical properties, including corneal hysteresis (CH) and corneal resistance factor (CRF), were measured with the ocular response analyzer (ORA). The ORA also determined the values of Goldmann-correlated intraocular pressure and corneal-compensated intraocular pressure. Central corneal thickness (CCT) was measured by the ORA integrated handheld ultrasonic pachymeter. The values recorded by the ORA were compared between eyes with PEX syndrome and those without PEX syndrome. Eyes with unilateral PEX syndrome and fellow eyes without PEX syndrome were also compared. RESULTS: The mean CH and CRF of all eyes with PEX syndrome were significantly lower than those of control eyes (P < 0.05). Neither corneal-compensated intraocular pressure nor Goldmann-correlated intraocular pressure showed a statistically significant difference in both the groups. Mean CCT values also did not show significant difference. Comparison of the unilateral eyes with PEX syndrome with the apparently normal fellow eyes revealed no significant difference between the mean CCT, mean CH, and mean CRF values (P > 0.05). However, the mean corneal-compensated intraocular pressure and Goldmann-correlated intraocular pressure were relatively higher in the PEX syndrome eye (P < 0.05). There was no significant difference between the mean CCT values of these groups (P > 0.05). CONCLUSIONS: The CH and CRF decrease in both unilateral and bilateral PEX syndrome suggested that PEX syndrome has a weakening effect on corneal biomechanical properties. Moreover, in subjects with clinically unilateral PEX syndrome, these properties were closer to eyes with PEX syndrome than to normal control eyes.

AS-OCT as a tool for flap thickness measurement after femtosecond-assisted LASIK.

BACKGROUND AND OBJECTIVE: to investigate the efficacy of anterior segment optical coherence tomography (AS-OCT) for calculating flap thickness in femtosecond laser-assisted laser in situ keratomileusis. PATIENTS AND METHODS: fifty-one eyes of 26 patients with myopia and myopic astigmatism were included in this prospective study. High-resolution corneal images were evaluated at 1 week and 1 month postoperatively. Images along the horizontal meridian were measured with the flap tool at seven points. RESULT: measurements at vertex and at 1 mm nasally and temporally from the vertex were indistinct but easily defined. Although statistically not significant, flaps were found to be thinner in the central cornea and thicker in the periphery (P > .05). CONCLUSION: AS-OCT provides detailed high-resolution images for quantitative evaluation of the flap-stroma relationship, but it may not be precise in the central 2-mm area of the cornea. Despite this, AS-OCT is an imaging tool with significant utility.

In Vivo Confocal Microscopy in Presumed Central Cloudy Dystrophy of François.

A 70-years-old woman with no visual symptoms was incidentally diagnosed with presumed central cloudy dystrophy of François (CCDF) on regular ophthalmic examination. Bilateral polygonal opacities separated by clear spaces were seen in corneal biomicroscopic examination. The opacities were prominent in the central cornea and occupied full-thickness corneal stroma. Confocal microscopy revealed small highly refractile granules and deposits in the anterior and deeper stromal layers. Multiple dark acellular striae among extra-cellular matrices with increased intensities were seen in the posterior stroma. No stromal layer of keratocytes was observed. In the right eye, the corneal endothelial cell density was 3,319 cells/mm(2), polymegathism was 52.9%, and pleomorphism was 34.3%. In the left eye, endothelial cell counts could not be performed because of high stromal reflectance intensity. Full-thickness involvement of the corneal stroma with hyperreflective granules and microstriae and absence of keratocytes may represent a more advanced stage of the dystrophy.

Evaluation of corneal topography with Orbscan II in first-degree relatives of patients with keratoconus.

PURPOSE: To evaluate the corneal topographic characteristics of first-degree relatives of patients with keratoconus with corneal topography to determine the incidence of clinical keratoconus and topographic abnormalities. METHODS: Between February and August 2006, Orbscan II analysis was done in 144 eyes of 72 cases who were first-degree relatives of patients diagnosed with clinical keratoconus. The findings were compared with preoperative Orbscan analyses of 52 clinically normal individuals who underwent laser in situ keratomileusis surgery and did not develop corneal ectasia in 3 years of follow-up. RESULTS: In 8 of the 72 first-degree relatives of patients with keratoconus, clinical keratoconus was diagnosed by the topographic pattern in Orbscan and clinical examination (group 1). The remaining 64 subjects (group 2) were compared with the control group (group 3). The central corneal thickness was 523.7 +/- 40.4 microm in group 2, whereas it was 546.3 +/- 33.1 microm in group 3 (P < 0.05). The central corneal thickness, thinnest pachymetric reading, posterior elevation value, distance between the greatest anterior/posterior elevation points, and corneal center, posterior best fit sphere (BFS) values, posterior BFS:anterior BFS ratio, and irregularity values were significantly different between group 2 and group 3 (P < 0.05). CONCLUSIONS: The keratoconus incidence was found to be 11% in first-degree relatives of patients with keratoconus as opposed to a reported incidence of keratoconus of 0.05% in the general population. In first-degree relatives of patients with keratoconus who did not have a topographic keratoconus pattern, abnormal corneal topographic values were detected. The asymptomatic relatives of patients with keratoconus should undergo a thorough preoperative analysis for subtle topographic abnormalities before any keratorefractive surgery.

A comparison of induced astigmatism in conventional and wavefront-guided myopic LASIK using LADARVision4000 and VISX S4 platforms.

PURPOSE: To evaluate and compare the surgically induced astigmatism in myopic eyes undergoing conventional and wavefront-guided LASIK. METHODS: A retrospective review was performed of the charts of 200 myopic eyes of 121 patients who underwent either custom or conventional treatments via the VISX S4 or LADARVision4000 platforms (50 consecutive eyes in each of the four groups). The primary outcome measure was manifest refraction, which was evaluated preoperatively and at 3 months postoperatively. The magnitude and axis of the unintended surgically induced astigmatism were calculated using vector analysis. The Student t test was used to compare the magnitudes of the surgically induced astigmatism and the absolute angle of error. RESULTS: The mean preoperative manifest cylinder was 0.66 +/- 0.38 diopters (D) for conventional VISX S4 and 0.68 +/- 0.39 D for VISX CustomVue (P = .795), and 0.76 +/- 0.56 D for LADARVision and 0.61 +/- 0.36 D for LADAR CustomCornea (P = .114). The success index was 0.19 +/- 0.41 for VISX S4 and 0.49 +/- 0.49 for VISX CustomVue (P = .0013), and 0.25 +/- 0.47 for LADARVision and 0.20 +/- 0.39 for LADAR CustomCornea (P = .5721). The absolute mean angle of error was 4.4 +/- 13.9 degrees for VISX S4 versus 14.9 +/- 23.9 degrees for VISX CustomVue (P = .0085), and 6.1 +/- 12.30 for LADARVision versus 3.9 +/- 11.1 degrees for LADAR CustomCornea (P = .3501). Of the VISX CustomVue eyes, 32% had an absolute angle of error > 10 degrees, as compared to 10% for both the VISX S4 and LADAR CustomCornea eyes (P = .013), and 16% for the LADARVision group (P = .056). CONCLUSIONS: Wavefront-guided ablation is associated with higher surgically induced astigmatism and larger astigmatic axis shift on the VISX platform as compared to the LADAR CustomCornea and the LADAR and VISX conventional platforms. Care should be emphasized mainly during registration/alignment to minimize surgically induced astigmatism in wavefront-guided LASIK.

Hyperopic laser in situ keratomileusis in eyes with previous radial keratotomy.

PURPOSE: To assess the safety and efficacy of hyperopic laser in situ keratomileusis (LASIK) in eyes with previous radial keratotomy (RK). SETTING: Zale Lipshy University Hospital Laser Center for Vision, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: Thirty-eight eyes of 25 patients were treated with LASIK for secondary hyperopia after RK using a Visx Star S2, S3, S4, or LADARVision excimer laser. Retreatment was done in 7 eyes. The main outcome measures were manifest refraction spherical equivalent (MRSE), uncorrected visual acuity (UCVA), best spectacle corrected visual acuity (BSCVA), predictability of treatment, and complications. RESULTS: Preoperative mean MRSE was +2.39 diopters (D) +/- 1.28 (SD) (range +0.87 to +6.00 D). At the last visit (25 eyes with minimum follow-up of 12 months, including retreatments), the mean follow-up was 23.3 +/- 7.3 months (range 12 to 34 months), the mean MRSE was +0.11 +/- 0.71 D, and the UCVA was 20/40 or better in 24 eyes (96%). Although no significant change in the mean MRSE was observed, the postoperative mean refractive cylinder showed a gradual increase over the follow-up period. No eye lost more than 2 lines of BSCVA. CONCLUSIONS: Laser in situ keratomileusis was a safe and effective treatment with good predictability for the correction of consecutive hyperopia after RK. Cylindrical errors were difficult to correct, and astigmatic correction tended to regress over time. Retreatments are safe when old flaps were relifted.

Ophthalmic examination of the captive western lowland gorilla (Gorilla gorilla gorilla).

This study examined the captive western lowland gorilla (Gorilla gorilla gorilla) eye as compared and contrasted with the human eye. Bilateral ophthalmic examinations of western lowland gorillas (n = 5) while under general anesthesia were performed opportunistically, including slit-lamp biomicroscopy, dilated fundus examination, cycloplegic retinoscopy, Schiotz tonometry, corneal diameter and thickness measurements, A-scan and B-scan ultrasonography, keratometry, and cultures of the eyelid margins and bulbar conjunctiva. Mean spherical equivalent refractive error by cycloplegic retinoscopy was +1.20 +/- 0.59 diopters. Mean intraocular pressure by Schiotz tonometry was 12.0 +/- 4.3 mm Hg. Mean optic nerve head cup to disc ratio was 0.42 +/- 0.11. Mean horizontal corneal diameter was 13.4 +/- 0.8 mm, and mean vertical cornea diameter was 12.7 +/- 0.8 mm. Mean central corneal thickness by ultrasound pachymetry was 489 +/- 52 microm. Mean axial length of the eye by A-scan was 22.75 +/- 0.71 mm. Mean lens thickness by A-scan was 4.23 +/- 0.34 mm. Mean anterior chamber depth by A-scan was 4.00 +/- 0.26 mm. Mean keratometry reading was 44.38 +/- 1.64 diopters. Eyelid margin and bulbar conjunctival cultures isolated Candida sp. (n = 5), Staphylococcus aureus (n = 4), Staphylococcus epidermidis (n = 3), Staphylococcus saccharolyticus (n = 3), and Micrococcus sp. (n = 3). This study suggests important similarities between western lowland gorilla and human eyes. These similarities may allow diagnostics, techniques, and equipment for human eye surgery, such as those used for cataract extraction and intraocular lens implantation, to be successfully utilized for gorillas.

Hyperopic laser-assisted in situ keratomileusis results with LADARVision, Visx Star S2, and Visx Star S3.

PURPOSE: To compare the LADARVision (LV), Visx Star S3 (S3), and Visx Star S2 (S2) excimer lasers in the treatment of spherical hyperopia and hyperopic astigmatism with laser-assisted in situ keratomileusis. SETTING: A parallel, consecutive, three-surgeon, cohort comparison was performed at Zale Lipshy University Hospital, Laser Center for Vision, The University of Texas Southwestern Medical Center at Dallas, Texas for consecutive cases between January 2001 and October 2001. METHODS: Treatment outcomes of 105 hyperopic eyes with manifest refraction spherical equivalents of up to +6.50 diopters and astigmatism up to 3.75 diopters were compared. Forty-one eyes were treated with LV; 25 eyes were treated with S3; and 39 eyes were treated with S2. Outcome measures included uncorrected visual acuity, best spectacle-corrected visual acuity, predictability, and stability of treatments at 1 week and 1, 3, and 6 months. RESULTS: All three lasers were comparable in terms of refractive stability and predictability. The LV group had consistently better uncorrected visual acuities than did the S2 and S3 groups during the follow-up period. At 6 months, the LV group had statistically significantly better visual results than the S3 group at the 20/25 and 20/20 levels, whereas the only significant difference between the LV and S2 groups was at the 20/25 level. Better visual outcomes were achieved with S2 than with S3, but the differences were not statistically significant. No eye lost more than one line of best spectacle-corrected visual acuity. CONCLUSIONS: Predictability and stability of hyperopic laser-assisted in situ keratomileusis treatments with all three lasers were comparable. Visual results with LV at 6 months were statistically significantly better than those with S3 and S2.

Comparison of LADARVision and Visx Star S3 laser in situ keratomileusis outcomes in myopia and hyperopia.

PURPOSE: To compare visual outcomes with 2 commonly used excimer lasers, the Autonomous LADARVision (LV) (Alcon Laboratories Inc.) and the Visx Star S3 (S3), in the performance of myopic and hyperopic astigmatic laser in situ keratomileusis (LASIK). SETTING: Zale Lipshy University Hospital Laser Center for Vision, University of Texas Southwestern Medical Center, Dallas, Texas, USA. METHODS: In this retrospective single-center 3-surgeon cohort comparison, 100 consecutive LV-treated myopic eyes with a mean manifest refraction spherical equivalent (MRSE) of -3.22 diopters (D) (range 0 to -6.00 D) (mean astigmatism 0.95 D [range 0 to 4.00 D]) were compared with 100 consecutive S3-treated eyes with a similar MRSE (mean MRSE -3.19 D; mean astigmatism 0.66 D [range 0 to 2.75 D]). Forty-one consecutive LV-treated hyperopic eyes with a mean MRSE of +2.59 D (range +1.00 to +6.00 D) (mean astigmatism 0.89 D [range 0 to 3.50 D]) were compared with 25 consecutive S3-treated eyes with a similar MRSE (mean MRSE +2.70 D; mean astigmatism 0.87 D [range 0 to 2.75 D]). The following outcomes were compared: uncorrected visual acuity, refractive predictability and stability, gain or loss of best spectacle-corrected visual acuity, and need for enhancement. RESULTS: Statistically significant differences in outcomes were found between lasers in the treatment of hyperopia and hyperopic astigmatism. No outcome differences between lasers were found in the treatment of myopia and myopic astigmatism. CONCLUSION: The LV and S3 lasers yielded equivalent results in myopic LASIK between 0 and -6.00 D; however, the LADARVision yielded statistically significantly better results in hyperopic LASIK between +1.00 and +6.00 D.

Presumed hyposecretory/hyperevaporative KCS: tear characteristics.

PURPOSE: To characterize patients with ocular surface drying and a diagnosis of keratoconjunctivitis sicca (KCS). METHODS: Patients with a prior diagnosis of KCS and symptoms of dryness or foreign-body sensation who also had vital staining of the interpalpebral fissure ocular surface in the absence of lid and ocular surface inflammation were entered into the study along with normal controls. Patients were segregated into those with "classic" KCS, who did not have concomitant meibomian gland dysfunction (MGD), and those with KCS and MGD. The latter had slit-lamp evidence of difficult-to-express or turbid meibomian secretions upon expression. Patients and normal controls were evaluated for tear volume, flow, and turnover using fluorophotometry; meibomian gland dropout by meibography; evaporation by evaporometry; and tear production by the Schirmer 1 test. RESULTS: All patients with KCS had decreased tear volume, flow, and Schirmer 1 values as well as increased meibomian gland dropout. None of the patient groups were found to have increased tear evaporation compared with normals or other disease subgroups. No correlation between degree of meibomian gland dropout and evaporation was found. The degree of total vital staining or presence of corneal staining correlated with a more severe aqueous deficiency. CONCLUSIONS: Patients with ocular surface drying in the absence of inflammation have decreased tear volume, flow, and Schirmer 1 values as well as increased meibomian gland dropout. The role of meibomian gland dropout or slit-lamp MGD in disease is unclear and in our study specifically did not correlate with increased tear evaporation.