Evaluation of Corneal Biomechanical Changes After Collagen Crosslinking in Patients with Progressive Keratoconus by Ocular Response Analyzer.

OBJECTIVES: To evaluate corneal biomechanics before and after collagen crosslinking (CXL) in patients with progressive keratoconus. MATERIALS AND METHODS: In this prospective study, CXL was performed under topical anesthesia after removal of the epithelium (epi-off technique) by applying ultraviolet A (UVA) light at a wavelength of 365 nm and power of 3 mW/cm2 or 5.4 joule/cm2. Isoosmolar 0.1% riboflavin solution was administered before and during UVA irradiation. In addition to ophthalmologic examination, ocular response analyzer measurements were performed pre- and postoperatively. Corneal hysteresis (CH), corneal resistance factor (CRF), corneal compensated intraocular pressure (IOPcc), Goldmann-correlated intraocular pressure (IOPg), and central corneal thickness (CCT) were recorded. RESULTS: The study included 35 eyes of 30 patients with progressive keratoconus. The mean age was 28.2±6.5 years and postoperative follow-up time was 20.2±14.7 months (range: 6-74 months). The mean CH was 8.60±1.23 mmHg preoperatively, 8.96±2.05 mmHg in the early postoperative period (1-6 months), (p=0.28) and 8.96±1.28 mmHg in the late postoperative period (10-29 months) (p=0.48). Mean CRF was 7.13±1.50 mmHg preoperatively, 8.48±2.16 mmHg in the early postoperative period (p=0.009), and 7.71±1.29 mmHg in the late postoperative period (p=0.40). Mean IOPcc was 12.78±2.34 mmHg preoperatively, 15.38±4.21 mmHg in the early postoperative period (p=0.12) and 13.68±3.61 mmHg in the late postoperative period (p=0.48). Mean IOPg was 9.56±2.73 mmHg preoperatively, 13.01±4.45 mmHg in the early postoperative period (p=0.046), and 10.86±3.47 mmHg in the late postoperative period (p=0.44). Mean CCT was 484.43±41.26 µm preoperatively, 474.16±64.74 µm in the early postoperative period (p=0.70), and 470.38±33.64 µm in late postoperative period (p=0.71). CONCLUSION: CXL is a treatment modality believed to affect corneal biomechanics in keratoconus, but the results of larger patient series with longer follow-up periods may enable a better evaluation.

Pregnancy and the Eye.

Pregnancy causes significant changes in all systems of the body. Although most of them are physiological, they may also lead to pathological consequences. The resulting pathological changes may occur for the first time or existing diseases affected by pregnancy can become more serious or change course. Diseases specific only to pregnancy may arise. Like all systems of the body, the visual system is also affected by pregnancy, developing a wide range of physiological and pathological changes. Knowing the ocular physiological changes and diagnosing eye diseases that may develop during pregnancy, and preventing and treating these diseases is crucial to ensure the baby's healthy development. Therefore, we have reviewed the conditions that an ophthalmologist should recognize, follow-up, and pay attention to during treatment and summarized them under the topic "pregnancy and the eye".

The complementary benefit of anterior segment optical coherence tomography in penetrating keratoplasty.

PURPOSE: To evaluate the utility of anterior segment optical coherence tomography (AS-OCT) assessment in the pre- and postsurgical management of full-thickness corneal grafts. METHODS: Seventy eyes of 58 patients who had penetrating keratoplasty were included in the study. High resolution AS-OCT scans of the cornea and the anterior segment were performed before and after transplantation in 17 eyes with the Visante™ optical coherence tomography. Fifty-three eyes were examined in the late postoperative period. RESULTS: The mean follow-up was 4.3 years (range, 1-15 years). Six different graft-host junctions were identified. Three patients with graft rejection, four patients with anterior synechia, and three patients with corneal ulcer were evaluated. Preoperative evaluation of eyes with semiopaque and totally opaque corneas revealed important information about anterior segment structures additional to slit-lamp findings. CONCLUSION: AS-OCT is a useful complementary tool for the evaluation of penetrating corneal transplantation surgery and in the management of its postoperative complications.

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.

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 software's 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.

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.

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

PURPOSE: To assess the influence of intrastromal corneal ring segment (ICRS) implantation on corneal biomechanics in patients with keratoconus. METHODS: Patients 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. RESULTS: The 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. CONCLUSIONS: In 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.

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.

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.

Immediate evaluation of the flaps created by femtosecond laser using anterior segment optical coherence tomography.

BACKGROUND AND OBJECTIVE: To demonstrate the practical and functional evaluation of flaps created intraoperatively by femtosecond laser using anterior segment optical coherence tomography (AS-OCT). PATIENTS AND METHODS: The study prospectively examined 11 eyes of 6 patients who underwent uneventful LASIK surgery with the aid of the IntraLase femtosecond laser (IntraLase Corp., Irvine, CA). During the waiting period between femtosecond laser and excimer laser, all eyes were evaluated by AS-OCT to image each flap immediately before flap lifting and laser ablation. Flap thickness and residual stromal bed thickness were calculated automatically using the software's flap tool. RESULTS: A uniform flap was created by femtosecond laser not only in the central cornea, but also in all quadrants. CONCLUSION: The qualitative and quantitative evaluation of the corneal flap created by a femtosecond laser using AS-OCT before lifting the flap confirms that the femtosecond laser is a practical intraoperative approach that offers a safer surgery.

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 ORA's integrated handheld ultrasonic pachymeter. RESULTS: The mean preoperative CCT (537 microm+/-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 (ACD(1)), pupil-referenced (ACD(2)), and lens-referenced (ACD(3)) 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 ACD(1) (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 ACD(2), 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 ACD(3), 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.