Postoperative Central Corneal Thickness Research Articles

Viscoanaesthesia in cataract surgery: a prospective, randomized clinical trial

We aimed to compare viscoanaesthesia (VisThesia) with intracameral lidocaine in cataract surgery carried out under topical anaesthesia. In this prospective study 98 patients were randomly assigned to receive VisThesia (group 1, n = 49) or 0.5 cc of 1% unpreserved lidocaine (group 2, n = 49). All surgery was carried out by one surgeon using clear corneal technique. Pachymetry, the status of the cornea and anterior chamber, and intraocular pressure (IOP) were checked pre- and postoperatively. Mean pain scores were 0.12 (maximum: 3) in group 1 and 0.37 in group 2; the difference between the groups was not statistically significant (95% confidence interval [CI] 0.003-0.487; p = 0.05). A total of 48 patients in group 1 (98%) and 49 in group 2 (100%) reported no discomfort or only mild discomfort. No significant differences in flare and cells in the anterior chamber or IOP were found between the two study groups. There was a significantly greater frequency of corneal oedema in group 1 (p = 0.001). Postoperative central corneal thickness values were also significantly higher in group 1 (95% CI 11.64-57.24; p = 0.003). Results suggest that viscoanaesthesia provides a level of comfort during cataract surgery under topical anaesthesia similar to that facilitated by intracameral lidocaine. However, patients who are given viscoanaesthesia may have increased risk for postoperative corneal oedema.

Clinical Outcomes of Cataract Surgery Using Torsional Mode Phacoemulsification and Soft Shell Technique

Purpose: To evaluate the additional protective effect of the soft shell technique on corneal endothelial cells in torsional mode phacoemulsification. Methods: Torsional mode phacoemulsification was performed on 60 eyes in 38 patients who were diagnosed with moderate cataracts. Thirty eyes were assigned to the soft shell technique group, and a control group with 30 eyes using only cohesive viscoelastics was created to evaluate ultrasound (US) time, mean US intensity, cumulative dissipated energy (CDE), and amount of used balanced salt solution. Corneal endothelium and corneal thickness were measured before and after the procedure. Results: There were no statistically significant differences in US time, mean US intensity, cumulative dissipated energy, and dosage of the balanced salt solution between the two groups. There were no statistically significant differences between the two groups in postoperative central corneal thickness. Corneal endothelial cell densities decreased significantly after surgery in both groups, but there were no statistically significant differences between the two groups. Conclusions: There are no significant differences in the intensity of ultrasound, the density of corneal endothelial cells or the thickness of the cornea between the two groups. Therefore, the soft shell technique is not needed under torsional mode phacoemulsification.

Effect of bimatoprost on intraocular pressure after cataract surgery

Background: An increase in intraocular pressure (IOP) frequently occurs after otherwise uneventful phacoemulsification cataract surgery. This study was conducted to determine the efficacy of bimatoprost 0.03% drops given preoperatively in preventing IOP rise following phacoemulsification cataract surgery. Methods: In this prospective, randomized, double-masked, placebo-controlled study, 91 eyes of 85 patients scheduled to have clear corneal phacoemulsification cataract surgery were randomly divided into 2 groups. One hour before surgery, 1 group (48 eyes) received 1 drop of bimatoprost 0.03%, and the other group (43 eyes) received 1 drop of a balanced saline solution (placebo). A masked observer measured IOP preoperatively, and 3 and 24 hours postoperatively. Anterior chamber cellular reaction was measured on the first day after surgery. Preoperative and postoperative central corneal thickness (CCT) was assessed. Results: The mean IOP changes from baseline were not statistically different between the 2 groups at 3 hours ( p = 0.618). At 24 hours, there was a statistically significant difference between the mean IOP changes of the groups ( p = 0.001). The incidence of IOP elevation greater than 5 or 10 mm Hg at 24 hours was significantly higher in the control group (9 of 43 eyes) than the bimatoprost group (3 of 48 eyes) ( p = 0.039). Anterior chamber reaction was not increased by bimatoprost. Mean CCT change was not different between the groups at 24 hours ( p = 0.615). Interpretation: When compared with placebo, prophylactic use of 1 drop of bimatoprost before phacoemulsification cataract surgery failed to produce a significantly different effect on IOP levels from placebo at 3 hours postoperatively, but it caused a significant IOP reduction at 24 hours.

Comparison of a torsional handpiece through microincision versus standard clear corneal cataract wounds

To directly compare intraoperative and clinical parameters using a torsional handpiece through microincision and standard clear corneal cataract wounds with appropriately configured tips and sleeves. Duke University Eye Center, Durham, North Carolina, USA. Cataracts in both eyes of 32 patients needing bilateral surgery were extracted using the OZil torsional handpiece. Tips and sleeve selections were optimized for the incision chosen. Right eyes had cataract surgery using a standard method consisting of a 2.8 mm incision with a 0.9 mm tapered 30-degree bevel Kelman configuration tip with a Microsleeve. Left eyes had cataract surgery through a 2.2 mm microincision using a 0.9 mm miniflared 45-degree bevel Kelman configuration tip with an Ultrasleeve. Intraoperative measurements included cumulative dissipated energy (CDE) and balanced salt solution use. Clinical measurements included preoperative and 1-day postoperative central corneal thickness (CCT), preoperative and 6-month postoperative endothelial cell count (ECC), and preoperative and postoperative anterior segment optical coherence tomography (AS-OCT). Intraoperatively, the microincision (2.2 mm) group had less CDE use than the standard incision (2.8 mm) group (P= .001). Clinical measurements showed less ECC loss at 6 months in the microincision group (P<.05). No difference in CCT or AS-OCT findings was detected between groups. Phacoemulsification using the OZil torsional handpiece through a microincision with an Ultrasleeve and a 45-degree miniflared tip showed favorable clinical and intraoperative characteristics such as less total energy use and less endothelial cell loss at 6 months. Further studies are warranted to substantiate these preliminary findings.

DisCoVisc versus the soft-shell technique using Viscoat and Provisc in phacoemulsification: Randomized clinical trial

To compare the effects and outcomes of DisCoVisc (hyaluronic acid 1.6%-chondroitin sulfate 4.0%) with those of the soft-shell technique using Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%) and Provisc (sodium hyaluronate 1.0%) in phacoemulsification. Iladevi Cataract & IOL Research Centre, Ahmedabad, India. This prospective randomized clinical trial comprised 100 eyes having phacoemulsification by the same surgeon using a standardized technique. Eyes were randomly assigned to DisCoVisc (Group 1) or Viscoat and Provisc (Group 2). Preoperative and postoperative examinations included absolute change in pachymetry, percentage difference in endothelial cell density (ECD) and coefficient of variation (CV), and anterior segment inflammation. The mean postoperative central corneal thickness (CCT) in Group 1 and Group 2 was 590.96+/-46.05 microm and 586.94+/-50.57 microm, respectively, at 1 day; 554.14+/-35.45 microm and 551.65+/-37.69 microm, respectively, at 7 days; and 533.74+/-29.12 microm and 536.44+/-35.59 microm, respectively, at 1 month. The between-group differences in CCT were not statistically significant. At 3 months, the mean ECD was 2427.06+/-243.26 cells/mm2 and 2475.30+/-222.83 cells/mm2, respectively, and the mean CV, 42.38+/-7.94 cells/mm2 and 41.66+/-7.71 cells/mm2, respectively. There was no significant difference in the mean ECD between preoperatively and 3 months postoperatively or in corneal thickness between preoperatively and 1, 7, and 30 days postoperatively. A single injection of DisCoVisc was effective, and its postoperative outcomes were comparable to those of combined Viscoat and Provisc.

Corneal hysteresis using the Reichert ocular response analyser: findings pre‐ and post‐LASIK and LASEK

To evaluate and compare corneal hysteresis in patients prior to and following laser in situ keratomileusis (LASIK) and laser-assisted subepithelial keratectomy (LASEK) using the Reichert ocular response analyser (ORA). Corneal hysteresis was recorded prior to and 3 months after corneal laser refractive surgery for myopia. Preoperative corneal hysteresis was correlated with age and preoperative central corneal thickness (CCT). Postoperative corneal hysteresis was correlated with postoperative CCT in both the LASIK and LASEK treatment groups. The correlations between postoperative change in hysteresis and stromal ablation depth, percentage of tissue ablated, optical zone and patient age were also examined. A total of 84 eyes of 84 patients were involved in the study. LASIK was performed in 63 eyes and LASEK in 21. Mean preoperative corneal hysteresis of all eyes was 10.8 +/- 1.5 mmHg. Mean age, preoperative CCT, corneal hysteresis and ablation profile were similar in both groups. A statistically significant decrease in hysteresis occurred following LASIK (p < 0.01) and LASEK (p < 0.01) with similar decrements observed in both treatment groups. A moderate correlation was found between postoperative hysteresis and postoperative CCT in LASIK (r = 0.7) and LASEK (r = 0.7) treated eyes. A weak correlation was found between postoperative decrease in hysteresis and the parameters examined. Corneal hysteresis decreased following LASIK and LASEK. Similar reductions occurred following both procedures, indicating that LASIK involving a thin 120-mum flap did not induce additional biomechanical change. Postoperative reduction in hysteresis did not correlate with the amount or percentage of corneal tissue removed, nor with optical zone or patient age.

Measurement of Intraocular Pressure in LASIK and LASEK Patients Using the Reichert Ocular Response Analyzer and Goldmann Applanation Tonometry

To determine the efficacy of the Reichert Ocular Response Analyzer (ORA) to measure intraocular pressure (IOP) following corneal laser refractive surgery. Intraocular pressure was measured using Goldmann applanation tonometry preoperatively and 3 months following LASIK and LASEK for all levels of myopia and low levels of hyperopia. In LASIK eyes, 120-microm flaps were cut using the Hansatome XP. The ORA was used to measure Goldmann correlated IOP and corneal compensated IOP 3 months postoperatively. Postoperative central corneal thickness, hysteresis, and corneal curvature were assessed to determine their relationship with postoperative change in Goldmann applanation tonometry IOP. Efficacy of ORA IOP measurement was analyzed by comparing Goldmann applanation tonometry IOP with Goldmann correlated IOP. LASEK was performed on 35 eyes, and LASIK was performed on 90 eyes. In the LASIK group, mean Goldmann applanation tonometry IOP decreased 3.7+/-2.3 mmHg postoperatively (P=.00). Postoperative Goldmann applanation tonometry did not differ significantly (P=.06) from postoperative ORA Goldmann correlated IOP (10.2+/-2.1 mmHg). In the LASEK group, mean Goldmann applanation tonometry IOP decreased 3.9+/-2.3 mmHg (P=.00). Postoperative Goldmann applanation tonometry did not differ significantly (P=.6) from postoperative ORA Goldmann correlated IOP (10.7+/-2.5 mmHg). Postoperative decrease in Goldmann applanation tonometry IOP did not correlate with age, ablation depth, pre- and postoperative central corneal thickness or corneal hysteresis, or postoperative decrease in corneal curvature. Intraocular pressure measurements were similar using both the ORA Goldmann correlated IOP and Goldmann applanation tonometry following keratorefractive surgery.

Central Corneal Thickness Measurements by Ultrasound, Orbscan II, and Visante OCT After LASIK for Myopia

To compare central corneal thickness measurements obtained with Orbscan II scanning slit topography, Visante optical coherence tomography (OCT), and ultrasound pachymetry in myopic eyes after LASIK. This retrospective study included 34 consecutive patients (68 eyes) who underwent LASIK for the correction of myopia. Six months after surgery, central corneal thickness measurements were obtained using ultrasound pachymetry, Orbscan scanning slit topography, and Visante OCT. Data were analyzed using paired sample t test, Bland and Altman plot, and linear regression. Average postoperative central corneal thickness was 436.65+/-43.82 microm for ultrasound pachymetry, 422.84+/-51.04 microm for Orbscan (0.89 acoustic equivalent correction factor), and 422.26+/-42.46 microm for Visante. Compared to the ultrasound measurement, Orbscan and Visante measurements significantly underestimated the corneal thickness by 13.81+/-17.34 microm (P<.01) and 14.38+/-10.13 microm (P<.01), respectively. Both Orbscan and Visante OCT underestimated central corneal thickness compared to ultrasound pachymetry 6 months after LASIK, although measurements obtained with Visante OCT had better agreement and correlation with ultrasound pachymetry than with Orbscan.

Comparison of Optical Low Coherence Reflectometry and Ultrasound Pachymetry in the Measurement of Central Corneal Thickness Before and After Photorefractive Keratectomy

To compare an ultrasound pachymeter with an optical low coherence reflectometry (OLCR) pachymeter for measuring pre- and postoperative central corneal thickness of patients undergoing photorefractive keratectomy (PRK). In a prospective, noncomparative, interventional study, 48 myopic eyes (mean manifest refractive spherical equivalent: -4.93 +/- 2.93 diopters [D]) of 30 healthy patients underwent PRK. Pre- and postoperative central corneal thickness was measured by two examiners (E1, E2) with an ultrasound pachymeter and an OLCR pachymeter. Agreement and inter-rater repeatability were determined using the comparison method described by Bland and Altman. The limits of agreement between the two devices ranged from 17.8 microm (E1) to 20.5 microm (E2) preoperatively and from 22.4 microm (E1) to 16.9 microm (E2) postoperatively. The coefficient of inter-rater repeatability ranged from 9.1 microm (ultrasound pachymeter) to 5.4 microm (OLCR pachymeter) preoperatively and from 7.1 microm (ultrasound pachymeter) to 4.7 microm (OLCR pachymeter) postoperatively. The OLCR pachymeter seems to show better pre- and postoperative repeatability compared to the ultrasound pachymeter. The agreement between the two devices should be considered acceptable for clinical practice. Photorefractive keratectomy did not affect the postoperative agreement and repeatability of the pachymeters.

Intraoperative performance and postoperative outcomes of microcoaxial phacoemulsification: Observational study

To evaluate the intraoperative performance and postoperative outcomes after microcoaxial phacoemulsification. Iladevi Cataract & IOL Research Centre, Ahmedabad, India. A prospective observational case series comprised 84 eyes with age-related uncomplicated cataract having microcoaxial phacoemulsification through a 2.2 mm clear corneal incision by a standard surgical technique. Phacoemulsification parameters (Infiniti Vision System, Alcon) were microburst width, 30 ms; preset power, 50%; vacuum, 650 mm Hg; aspiration flow rate, 25 cc/minute. A single-piece Alcon AcrySof intraocular lens was implanted with the C cartridge (Alcon) cartridge. The incision was measured at the end of surgery. Observations included surgical time (from commencement of sculpting to end of epinucleus removal), cumulative dissipated energy (CDE), wound burns, intraoperative complications, postoperative increase in mean central corneal thickness (CCT) at 1 day and 1 month, mean % decrease in endothelial cell density (ECD), absolute mean change in coefficient of variation (cv) 3 months, and uncorrected visual acuity (UCVA) at 1 day. Data were analyzed using a 1-sample t test with 95% confidence intervals (CIs). The mean follow up was 3 months +/- 0.3 (SD). The mean incision size at the end of surgery was 2.3 +/- .09 mm; mean surgical time, 4.5 +/- 1.5 minutes; and mean CDE, 2.3 +/- 2.2 seconds. No wound burns or other intraoperative complications occurred. The postoperative CCT increased by a mean of 16 microm at 1 day (95% CI, 8-25; P = .66;) and by a mean of 3.14 microm at 1 month (95% CI, 2.26-4.05; P = .92). The ECD decreased by a mean of 5.8% (95% CI, 6.8-3.5; P = .82) and the mean coefficient of variation, by 3.3 (95% CI, 4.5-2.0; P = .65). At 1 day, the UCVA was 20/20 in 29% of cases, 20/20 to 20/40 in 58%, and 20/40 to 20/50 in 12%. Microcoaxial phacoemulsification was safely and effectively performed, achieving consistent and satisfactory postoperative outcomes.

Descemet’s Stripping with Endothelial Keratoplasty: Comparative Outcomes with Microkeratome-Dissected and Manually Dissected Donor Tissue

To compare outcomes with 2 donor dissection methods for Descemet's stripping with endothelial keratoplasty (DSEK). Retrospective, comparative, nonrandomized case series. Three hundred thirty consecutive transplants, 114 with manually dissected and 216 with microkeratome-dissected donor tissue. Donor posterior stroma/endothelium was transplanted, after stripping recipient Descemet's membrane/endothelium and dissecting the donor tissue by hand or with a microkeratome. Incidences of donor perforation and donor detachment were compared for all eyes. Visual and refractive outcomes were compared for the first 100 consecutive eyes in each group. Visual recovery was faster with microkeratome-dissected donor tissue, as evidenced by statistically better best spectacle-corrected visual acuity (VA) in that group 1 month after surgery (P = 0.015). Best spectacle-corrected VA was statistically comparable for the 2 groups preoperatively and 3 and 6 months postoperatively. Best spectacle-corrected VA was not correlated significantly with postoperative central corneal thickness (P = 0.25). Corneal thickness was significantly higher in the microkeratome group (690+/-77 mum, compared with 610+/-62 mum after hand dissection; P<0.0001). Mean refractive astigmatism was 1.5 diopters (D) preoperatively and 6 months postoperatively in both groups. Spherical equivalent refraction did not change in the microkeratome group (P = 0.64) but increased by 0.66 D in the hand dissection group (P = 0.0007). Methods designed to remove fluid from the donor/recipient graft interface ultimately reduced the detachment rate to <1% (1 in the last 140 cases). No donor perforations occurred in 216 microkeratome dissections, compared with 5 in 114 hand dissections (P = 0.002). Microkeratome dissection reduced the risk of donor tissue perforation, provided faster visual recovery after DSEK, and did not alter the refractive outcome.

The effect of elective phacofragmentation on central corneal thickness in the dog

To characterize the short- and intermediate-term effects of elective phacofragmentation on central corneal thickness (CCT) in the dog. Forty-three dogs (66 eyes) undergoing elective phacofragmentation cataract surgery over an 8-month period at a single private ophthalmology referral clinic were enrolled in the study. Central corneal thickness was measured by ultrasonic pachymetry just prior to surgery, 1 day following surgery, 1 week postoperatively, 1 month postoperatively, and more than 2 months postoperatively. Statistical comparisons were made using descriptive and inferential statistical methods with a level of significance set at P < 0.05. The initial mean CCT of 611 microm increased dramatically to 741 microm 1 day postphacofragmentation. Mean CCT remained slightly elevated (666 microm) at 1 week postoperatively, but became indistinguishable from preoperative measurements by 1 month postsurgery (626 microm) and remained so at the > 2-month time period (618 microm). The change over time and trends remained statistically significant and remarkably similar, even when adjusted separately for age, gender, surgeon status, diabetic status, cataract type, and total surgery time (all P < 0.0001). Corneas of diabetic dogs were thicker than those of nondiabetic dogs at all time periods, and the overall effect of diabetic status was significant (P = 0.016). There was a sharper increase from the preoperative to 1-day postoperative CCT in the diabetic group compared to the nondiabetic group. The mean CCT of the pseudophakic group took longer to return to baseline than the aphakic group. The mean CCT of the foldable intraocular lens (IOL) group took longer to return to baseline than both the rigid IOL and aphakic groups. Dogs with documented in-hospital postoperative intraocular pressure spikes (> 25 mmHg) developed a greater 1-day postsurgical increase in CCT. It appears that there was a sharper decrease in mean CCT from 1 month to more than 2 months postoperatively in the postoperative hypertension group. Elective phacofragmentation cataract surgery results in an increase in CCT in dogs, but this increase is transient. Particular care may be indicated to protect the endothelium of diabetic patients undergoing phacofragmentation. These data do not clearly support an advantage of the small-incision cataract surgery made possible by the use of foldable IOLs.

Evaluation of the Orssengo-Pye IOP corrective algorithm in LASIK patients with thick corneas

The objective of this study was to evaluate the Orssengo-Pye central corneal thickness (CCT) Goldmann applanation tonometry (GAT) corrective algorithm by observing changes in GAT and CCT before and after laser in situ keratomileusis (LASIK) surgery in patients with CCT that remains greater than 545 microm postoperatively. Tonometric and pachymetric measurements were made on 14 patients (28 eyes) before and after LASIK surgery. The selected patients were required to have average or above average postoperative central corneal thickness values in both eyes (not less than 545 microm). Preoperatively, all patients had CCT and GAT measurements taken. Postoperatively patients had CCT, GAT, and dynamic contour tonometric (DCT) measurements taken. Preoperatively, median CCT values were 589.536 microm. Median GAT values were 16.750 mmHg. Median corrected preoperative GAT values were 14.450 mmHg. After LASIK treatment, median CCT values were 559.417 microm. The decrease in median CCT was 30.119 microm. Median postoperative GAT values were 11.500 mmHg (decrease, 5.250 mmHg). Median corrected postoperative GAT values were 10.775 mmHg (decrease, 3.675 mmHg). Median postoperative DCT values were 17.858 mmHg. LASIK treatment causes a significant reduction in measured GAT intraocular pressure (IOP) values. The Orssengo-Pye formula, which attempts to correct for GAT error associated with individual variation in CCT, appears to yield misleading results in these circumstances. An unexpected 3.675-mmHg decrease in "corrected IOP" by the Orssengo-Pye method seen in this study may be attributed to some limitation or error in the formula. After adjusting for the approximate1.7-mmHg difference, which has been demonstrated between DCT and GAT, postoperative DCT values were similar to preoperative measured GAT values.

Intraocular Pressure Change after Laser In Situ Keratomileusis (LASIK)

To analyze the relationship between change in intraocular pressure (IOP) after laser in situ keratomileusis (LASIK), and preoperative central-corneal thickness (CCT), and central-corneal ablation depth (CCAD), a prospective study was conducted of 30 patients (60 eyes) with myopia or myopic astigmatism who underwent LASIK and who were followed up for a mean of 6 months. The parameters evaluated included IOP 1 week preoperatively and 3 months postoperatively, pre- and postoperative CCT, and CCAD; in addition, the anterior ocular segment and the fundus were examined, as was the apparent and cycloplegic refraction. There were 11 male patients and 19 female patients (mean age, 28.3 years) involved in the study. Mean IOP readings were 14.9 mmHg 1 week preoperatively, and 8.3 mmHg 3 months postoperatively; thus, the mean decrease in IOP after LASIK was 6.6 mmHg. Mean values for preoperative CCT, postoperative CCT, and CCAD were 537.2+/-34.7 microm, 434.0+/-32.5 microm, and 101.6+/-23.90 microm, respectively. IOP correlated with CCT both pre- and postoperatively. The mean change in IOP after LASIK for myopia and myopic astigmatism was statistically significant, but did not correlate with CCAD or age. We postulate that CCAD is not a significant predictor of IOP after LASIK.

Estimating residual stromal thickness before and after laser in situ keratomileusis

Purpose To determine the factor(s) that influences measurement of residual stromal thickness (RST) after laser in situ keratomileusis (LASIK) surgery. Setting Clinical office-based excimer laser refractive surgery center. Methods In this retrospective comparative interventional case study of 6235 eyes, ultrasonic corneal pachymetry was performed immediately before and after flap creation and immediately after laser ablation in the primary procedure and after 647 enhancements. Differences in the methods for calculating RST were compared statistically. Results Using the RST measured at enhancement as the actual RST, measurements of RST immediately after laser ablation underestimated residual thickness due to laser-induced stromal dehydration and microkeratome effects ( P<.001). Estimates of RST using a “standard” or estimated flap thickness were less accurate predictors of residual thickness ( P<.001) than use of the theoretical laser resection with a measured flap thickness (RST–4) ( P = .78) or a modified flap thickness subtracted from the postoperative corneal thickness (RST–8) ( P = .98), which provided the best RST estimates. Conclusions Before LASIK, the best means of estimating RST is to subtract the theoretical laser resection obtained from the laser computer and the expected flap thickness normally obtained with a given microkeratome system from the preoperative central corneal thickness. After LASIK, the most accurate means of calculating RST is to subtract the original flap thickness from the postoperative central corneal thickness.