Raciha Beril Kucumen

Corneal biomechanical properties and intraocular pressure changes after phacoemulsification and intraocular lens implantation

PURPOSE: To evaluate corneal viscoelastic and intraocular pressure (IOP) changes measured by an ocular response analyzer (ORA) after phacoemulsification and intraocular lens (IOL) implantation. SETTING: Yeditepe University Department of Ophthalmology, Istanbul, Turkey. METHODS: Fifty‐one eyes scheduled for cataract surgery were included in the study. Corneal hysteresis (CH), corneal resistance factor (CRF), corneal‐compensated intraocular pressure (IOPcc), and Goldmann‐correlated IOP (IOPg) were measured by ORA preoperatively and 1 week and 1 and 3 months postoperatively. Central corneal thickness (CCT) was measured using the ORAs integrated handheld ultrasonic pachymeter. RESULTS: The mean preoperative CCT (537 μm ± 46 [SD]) did not change significantly by the end of 1 month postoperatively. The mean preoperative IOPcc (17.2 ± 3.0 mm Hg) decreased significantly by 3 months postoperatively (15.2 ± 3.7 mm Hg) (P = .018). The mean CH decreased from 10.36 ± 1.48 mm Hg preoperatively to 9.64 ± 1.26 mm Hg at 1 week (P = .028); it increased to preoperative values at the end of 1 month (10.20 ± 1.70) and 3 months (10.74 ± 1.54) (P>.05). The mean CRF decreased from 10.94 ± 2.54 mm Hg preoperatively to 9.99 ± 1.77 at 1 week (P = .026); it increased to preoperative values at 1 month (10.26 ± 1.59) and 3 months (10.35 ± 1.46) (P>.05). CONCLUSIONS: Although CH and the CRF decreased in the early postoperative period, the parameters increased and reached preoperative values by 3 months postoperatively, showing that corneal biomechanical properties are influenced by phacoemulsification and IOL implantation.

Anterior segment optical coherence tomography measurement of anterior chamber depth and angle changes after phacoemulsification and intraocular lens implantation.

PURPOSE: To use anterior segment optical coherence tomography (AS‐OCT) to evaluate anterior chamber depth (ACD) and angle after phacoemulsification and intraocular lens (IOL) implantation. SETTING: Department of Ophthalmology, Yeditepe University, Istanbul, Turkey. METHODS: Forty‐seven eyes (37 patients) had uneventful phacoemulsification and IOL implantation through a clear corneal incision. Anterior segment OCT was performed preoperatively and 1 week and 1 month postoperatively. The angle‐referenced (ACD1), pupil‐referenced (ACD2), and lens‐referenced (ACD3) ACDs, crystalline lens rise (CLR), pseudophakic posterior chamber depth (PPCD), and nasal and temporal iridocorneal angles were measured. Statistical analysis was by a 1‐way analysis of variance and Pearson correlation analysis. RESULTS: The mean age of patients was 70 years ± 10.17 (SD). The mean ACD1 (mean increase) was 3.06 ± 0.25 mm preoperatively, 3.16 ± 0.22 mm at 1 week (0.1 mm), and 3.16 ± 0.19 mm at 1 month (0.1 mm); the mean ACD2, 2.76 ± 0.47 mm preoperatively, 3.62 ± 0.24 mm at 1 week (0.86 mm), and 3.63 ± 0.20 mm (0.87 mm) at 1 month; and the mean ACD3, 2.54 ± 0.46 mm preoperatively, 3.97 ± 0.28 mm at 1 week (1.43 mm), and 3.91 ± 0.25 mm at 1 month (1.37 mm). The mean CLR was 0.497 ± 0.363 mm and the mean PPCD, 0.322 ± 0.150 mm. The increase in nasal and temporal iridocorneal angles was statistically significant at both postoperative examinations (P<.01). CONCLUSION: Deepening of the anterior chamber and widening of the nasal and temporal angles after cataract extraction was shown on AS‐OCT.

Changes in corneal biomechanics in patients with keratoconus after penetrating keratoplasty.

Purpose: To examine the biomechanical properties of keratoconic eyes following penetrating keratoplasty and to compare results with the biomechanical characteristics of manifest keratoconus, forme fruste keratoconus and normal eyes as measured with the Reichert ocular response analyzer (ORA). Methods: This retrospective analysis comprised a total of 169 eyes: 34 eyes with forme fruste keratoconus (group FF), 36 eyes with manifest keratoconus (Group KC), 36 eyes that have undergone penetrating keratoplasty (Group PK) and a control group of 63 normal eyes (Group N). Corneal hysteresis (CH), corneal resistance factor (CRF), corneal compensated intraocular pressure, and Goldmann correlated intraocular pressure were measured by ORA. Central corneal thickness was calculated by the integrated handheld ultrasonic pachymeter of the ORA. The statistical analysis focused on CH and CRF changes among the 4 groups. Results: When compared with normal eyes, mean CH and CRF values were found significantly lower in all groups (P < 0.05). Mean CH values were 8.19 ± 1.49 mm Hg in Group KC, 9.21 ± 1.38 mm Hg in Group FF, 10.16 ± 1.93 mm Hg in Group PK, and 11.43 ± 1.52 mm Hg in normal eyes (Group N). Although there was not a significant difference in mean CH values between Groups PK and FF (P = 0.072), the difference was significant between Groups KC as well as FF and Groups KC and PK (P < 0.05). Mean CRF values were found as 6.79 ± 1.81 mm Hg (Group KC), 8.21 ± 1.64 mm Hg (Group FF), 9.94 ± 2.34 mm Hg (Group PK), and 11.53 ± 1.83 mm Hg in Group N. The difference was statistically significant among all groups (P < 0.05). Conclusions: Penetrating keratoplasty has a beneficial effect on corneal biomechanics in keratoconic eyes. CH and CRF parameters approach the range of normal eyes after corneal transplantation.

Influence of intrastromal corneal ring segment implantation on corneal biomechanical parameters in keratoconic eyes

PurposeTo assess the influence of intrastromal corneal ring segment (ICRS) implantation on corneal biomechanics in patients with keratoconus.MethodsPatients with keratoconus who underwent femtosecond laser-assisted ICRS (Keraring) implantation were evaluated with the ocular response analyzer (ORA). Metrics of corneal biomechanical parameters, including corneal hysteresis (CH) and corneal resistance factor (CRF) were measured both before and after surgery. The postoperative measurements recorded at the 1st, 3rd and 6th months, and 1st and 2nd years after surgery were analyzed.ResultsThe mean CRF was significantly lower in the early postoperative period (1st and 3rd month); however, the difference between the mean preoperative and late postoperative (6th months, 1st and 2nd years) CRF values was not significant. There were no significant differences between the mean preoperative and postoperative CH values.ConclusionsIn the early postoperative period a significant temporary decrease in CRF was observed after the femtosecond laser-assisted ICRS implantation; however, this surgery did not alter the CH significantly in the same time interval. Both CH and CRF did not show significant alteration from preoperative values in the late postoperative period.

Penetrating keratoplasty for corneal ectasia after laser in situ keratomileusis.

Purpose To improve the visual acuity of patients with progressive keratectasia following laser in situ keratomileusis (LASIK). Methods Five eyes of four patients underwent penetrating keratoplasty for ectasia after LASIK. In one patient the second eye was operated on 10 months after the first keratoplasty. The pre- and postoperative refraction, best spectacle-corrected visual acuity, and topographic data were evaluated. Results The preoperative refraction was −20.0 diopters (D) with high cylindrical values in all eyes at the time of surgery. After penetrating keratoplasty, mean spherical equivalent was −13.08±3.62 (SD) and mean refractive cylinder was −3.87±1.12 (SD). In one eye Urrets-Zavalia syndrome was noted as an early postoperative complication. In the second operated eye of another patient, there had been graft rejection several times. In this patient, frequent steroid use led to secondary glaucoma and he required filtering surgery. Conclusions Penetrating keratoplasty is effective and successful in treating iatrogenic keratectasia after LASIK, but these patients need a close and lifelong follow-up to treat late-term complications such as graft rejection and secondary glaucoma.

Assessment of Intrastromal Corneal Ring Segment Position With Anterior Segment Optical Coherence Tomography

BACKGROUND AND OBJECTIVE To examine the exact position of implanted Keraring (Mediphacos, Belo Horizonte, Brazil) segments by high-resolution anterior segment optical coherence tomography (AS-OCT). PATIENTS AND METHODS This study included 17 eyes of 13 patients with keratoconus who underwent uneventful intracorneal ring segment implantation with the aid of femtosecond laser. Eyes were evaluated by AS-OCT at the third postoperative month. Distance from the apex of the triangular cross-section of the ring segment to the anterior corneal surface and distances from two basal corners to the posterior corneal surface were measured. RESULTS Distance from apex to anterior corneal surface (263.1 ± 42.9 μm) was significantly smaller than target depth calculated intraoperatively (356.9 ± 35.7 μm, P < .001). Distance between outer basal corner and posterior corneal surface was significantly greater than distance between inner basal corner and posterior corneal surface. CONCLUSION High-resolution AS-OCT is a rapid, convenient, and valuable technique in the follow-up of patients with implanted Keraring segments that may be helpful in predicting ring-related complications.

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.

Intraoperative use of AS-OCT during intrastromal corneal ring segment implantation.

BACKGROUND AND OBJECTIVE To evaluate femtosecond laser-created tunnels intraoperatively by anterior segment optical coherence tomography (AS-OCT) during intrastromal corneal ring segment implantation. PATIENTS AND METHODS The study prospectively examined 13 eyes of 11 patients who underwent intrastromal corneal ring segment surgery with the aid of femtosecond laser. All eyes had keratoconus as the primary diagnosis. Eyes were examined by AS-OCT to image the tunnel immediately after femtosecond laser and before ring segment implantation. Tunnel depth was calculated automatically using the softwares flap tool and calipers. RESULTS The presence of air bubbles demonstrated the tunnel successfully by AS-OCT. Tunnel depth was measured at eight locations in four cross-sections of high-resolution cornea images. An overall evaluation was also made by changing the scan direction 360°. After confirmation that a uniform tunnel was satisfactorily created at the aimed depth, surgery proceeded with segment implantation. CONCLUSION AS-OCT can be used intraoperatively to assess femtosecond laser-created tunnel in intrastromal corneal ring segment implantation. The qualitative and quantitative evaluation of the intrastromal tunnel by AS-OCT before implantation of the ring segments is a practical intraoperative approach that may offer a safer surgery.

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.

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.