Central Corneal Thickness Values Research Articles

Comparison of intraocular pressure measurements between Icare PRO Tonometer, Goldmann Applanation Tonometer and non-contact tonometer in healthy and glaucomatous eyes

Abstract Purpose: To validate the comparative measurements of intraocular pressure performed with IcarePRO tonometer (IPT) in relation to Goldmann applanation tonometer (GAT) and non-contact tonometer (NCT), as well as to evaluate the influence of central corneal thickness (CCT) on these values. Methods: This was a prospective and comparative study conducted during 6 months in the Department of Ophthalmology, Hospital de Braga, Portugal. The study population comprised two groups: healthy adults and adults with primary open angle glaucoma (POAG). The IOP values were obtained by the three tonometers and the order of execution was randomly selected. CCT values were obtained by ultrasonic pachymetry. Results: A total of 168 eyes (74 with diagnosis of POAG and 94 healthy) of 84 patients were included in this study. The mean IOP values obtained by IPT, GAT and NCT were 17.36±3.78 mmHg; 14.59±3.32 mmHg; and 17.04±4.01 mmHg, respectively. The comparison between IPT and NCT did not reveal statistically significant differences in the two groups studied. However, statistically significant differences were obtained between IPT and GAT values (p <0.001). The IOP values, recorded by all the tonometers, were significantly and positivily correlated with the CCT (p <0.001). Conclusion: IOP readings measured by IPT are comparable with those obtained by NCT, but higher than those obtained by the GAT. CCT values are correlated with IOP measurements with IPT, as it does in GAT and NCT, and should be always taken into consideration.

Comparison of anterior segment measurements using Sirius Topographer® and Nidek Axial Length-Scan® with assessing repeatability in patients with cataracts

Purpose:The purpose of this study is to evaluate anterior segment measurements obtained using CSO Sirius Topographer® (CSO, Firenze, Italy) and Nidek Axial Length (AL)-Scan® (Nidek CO., Gamagori, Japan).Methods:A total of 43 eyes of 43 patients were included in this prospective study. The central corneal thickness (CCT), anterior chamber depth (ACD), white-to-white distance (WTW), flat keratometry (K1), steep keratometry (K2), and mean keratometry (K) values were randomly measured three times with each device by the same examiner. The intraclass correlation coefficient of repeatability was analyzed. The compatibility of both devices was evaluated using the 95% limits of the agreement proposed by Bland and Altman.Results:Examiner achieved high repeatability for all parameters on each device except the WTW measured by Sirius. All measurements except WTW and K1 taken with the Sirius were higher than that taken with the Nidek AL-Scan®. The difference in CCT, ACD, and WTW values was statistically significant.Conclusion:High repeatability of the measurements was achieved on both devices. Although Km, K1, and K2 measurements of the Sirius and the AL-Scan® showed good agreement, WTW, CCT, and ACD measurements significantly differed between two devices. Thus, anterior segment measurements except for Km, K1, and K2 cannot be used interchangeably between Sirius and Nidek AL-Scan® devices.

Comparative morphological evaluation of animal corneal parameters

The purpose of this study was to broaden the basic knowledge of corneal morphological structures in pigs, cows and rabbits and to find morphological and histological differences in the constituent corneal structures. After slaughter, corneal samples of 24 animals, including cows, pigs and rabbits, were investigated. Forty-eight eyeballs (n=48) of 8 pigs, 8 cows and 8 rabbits were used for this study. Central corneal thickness (CCT) values in cows were higher than those in pigs (P &amp;lt; 0.001) and rabbits. In rabbits, CCT, as a percentage of the eye axis length, was 55.03% greater than in cows and 40.55% greater than in pigs (P&amp;lt;0.001). The thickness of substantia propria (stroma) depended on the species and accounted for more than 80% of the thickness of all layers of the cornea. The thickness of the anterior epithelium amounted to 15.81% of the thickness of all layers of the cornea in cows, 11.79% in pigs, and 8.48% in rabbits (P&amp;lt;0.001). The data analysis showed that the caudal limiting membrane + endothelium was the thinnest layer of the cornea, with thickness ranging from 0.88% to 2.40% of the total thickness of all layers of the cornea in the three species under study (P&amp;lt;0.001). A statistically significant negative correlation was determined between the anterior epithelium and substantia propria in corneas of cows, pigs and rabbits (P&amp;lt;0.001). This paper describes the morphometric parameters of the cornea in pigs, cows and rabbits. These parameters will be of use to scientists using animal models in vision science research. .

Corneal endothelial changes in patients with vitamin D deficiency.

Purpose:The purpose of this study is to evaluate the effect of vitamin D deficiency on corneal endothelial layer using specular microscopy.Methods:Fifty-eight eyes of 58 patients whose vitamin D level was below 15 ng/ml and who had no ocular pathology were included in the study (Group 1). Forty eyes of 40 age-and sex-matched subjects were enrolled as control group (Group 2). Corneal endothelial cell density (CD), coefficient of variation (CV), hexagonal cell ratio (HEX), and central corneal thickness (CCT) were measured using specular microscopy (Konan Medical Inc., Nishinomiya, Japan). The obtained data were compared between the groups.Results:There was no significant difference between the groups in terms of age and gender (P = 0.344, P = 0.399, respectively). The mean CD value was 2772.79 ± 202.21 cells/mm2 in Group 1 and 2954.97 ± 116.89 cells/mm2 in Group 2 (P = 0.001). The mean CV value was 30.31 ± 3.65 in Group 1 and 28.20 ± 2.71 in Group 2 (P = 0.003). The mean HEX value was 46.56 ± 6.32 in Group 1 and 51.07 ± 5.28 in Group 2 (P = 0.001). The mean CCT value was 555.87 ± 36.90 μ in group 1 and 549.0 ± 37.39 μ in Group 2 (P = 0.96).Conclusion:Vitamin D deficiency may affect the corneal endothelial layer. Patients with vitamin D deficiency should be evaluated for endothelial parameters in particular before an intraocular surgery. Further studies are needed to confirm our results.

Evaluation of anterior segment parameters in patients with Turner syndrome using Scheimpflug imaging

To compare the anterior segment parameters in patients with Turner syndrome (TS) as measured by the Pentacam HR-Scheimpflug imaging system with those of healthy control subjects. This cross-sectional prospective study included 35 patients with TS and 30 age-matched controls. Corneal topographic analysis was performed using the Pentacam HR-Scheimpflug imaging system (Oculus, Wetzlar, Germany). The power of the corneal astigmatism, mean keratometry (Km) values for the both front and back surfaces of the cornea, maximum keratometry (Kmax), central corneal thickness (CCT), corneal volume (CoV), white-to-white diameter (WTW), chamber volume (CaV), angle and anterior chamber depth (ACD) values were recorded. The mean age of TS subjects was 17.2±6.1years; of controls, 16.4±5.7years. All participants were female. There was a significant difference in the mean values of WTW (11.3±0.5mm vs 12.0±0.4mm [P<0.001]), CaV (148.4±33.5mm3 vs 191.9±27.6mm3 [P<0.001]), and ACD (2.8±0.3mm vs 3.1±0.2mm [P<0.001]) between TS versus group and the control group. The mean values of the power of the corneal astigmatism, Km values for the both front and back of the corneal surface, Kmax, CCT, CoV, and angle values were similar between groups (P>0.05 for each one). There was a reduction in CaV, ACD, and WTW measurements in TS patients compared with controls.

Diurnal variations in intraocular pressure and central corneal thickness and the correlation between these factors in dogs.

To study the diurnal variation in intraocular pressure (IOP) and central corneal thickness (CCT) in healthy Beagles by rebound tonometry and ultrasonic pachymetry, respectively, in addition to determining whether a correlation exists between these two variables. Twenty eyes from 10 healthy Beagle dogs were included in the study. The IOP and CCT were measured by rebound tonometry and ultrasonic pachymetry, respectively, at 2-h intervals over an 8-hour period between 10:00 and 18:00. The mean values (± SD) of IOP obtained were 11.45±2.96 at 10:00, 10.00±1.89 at 12:00, 8.25±1.62 at 14:00, 7.05±1.05 at 16:00, and 6.55±1.36 at 18:00. The mean values (± SD) of CCT obtained were 554.95±72.41 at 10:00, 549.20±69.10 at 12:00, 566.15±80.56 at 14:00, 545.45±70.19 at 16:00, and 538.30±73.33 at 18:00. The IOP and CCT of dogs were found to decrease progressively from the first to the last measurement. There were statistically significant differences between the IOP (P=0.000) and CCT values (P=0.032) measured at different times of the day. There was no effect or interaction between gender and eye with the dependent variables. The IOP and CCT were found to be positively correlated (r=0.213, P=0.034). The regression equationdemonstrated that for every 100μm increase in CCT, there was an elevation in IOP by 0.8mmHg. The CCT and IOP values were lower in the afternoon/evening than in the morning, and these were positively correlated. Both findings are important for the diagnostic interpretation of IOP values in dogs.

Correlation between central corneal thickness and myopia.

To analyze the correlation between central corneal thickness (CCT) and myopia in refractive surgery candidates. Patients that underwent myopic laser refractive surgery between January 2000 and December 2014 were included. Preoperative CCT was measured by ultrasonic pachymetry, and refractive status determined by manifest and cycloplegic refraction. A total of 30,245 individuals were included. Mean age was 28.2±8.6years, and 45.9% were female. Mean refractive error was 4.02±2.17 D (range 0.25-19.5), and the mean CCT measurement was 533.5±35.5µm (range 404-794). Younger individuals showed higher degree of myopia (p=0.006). No difference in CCT was found between women and men (533.0±35.1 and 533.6±35.9µm, respectively, p=0.19). Though CCT showed no correlation with age (p=0.226) participants above age 40 expressed higher CCT values (p<0.001). No significant correlation was found between the CCT and cylinder (p>0.05). An increase in mean keratometry was associated with a decrease in CCT (p<0.001). There was a direct correlation between the degree of myopia and CCT (r=0.94, p<0.001). The result remained the same after adjusting for age group and gender in stepwise backward regression analysis (p<0.001). Central corneal thickness is correlated with the degree of myopia among adults undergoing refractive surgery.

Biometric evaluation of myopic eyes without posterior staphyloma: disproportionate ocular growth.

To evaluate changes in the anterior segment of myopic eyes and assess anterior biometry as a function of axial length (AL). Retrospective investigational study. Patients evaluated for phakic intraocular lens surgery at a tertiary eye care centre. Patients with corrected visual acuity >20/40 and AL>24.5mm were included in the study. Posterior staphyloma and maculopathy were ruled out in all the patients, and 176 eyes were included for analysis. AL was measured with partial coherence interferometry, while keratometry, central corneal thickness (CCT), anterior chamber depth (ACD), and horizontal white to white (WTW) were measured with slit-scanning topography. Group 1 included 55 eyes with AL<26.5mm, group 2 had 57 eyes with AL between 26.5 and 28.5mm while group 3 had 64 eyes with AL>28.5mm. Correlation of AL with anterior biometry. The mean AL of the study eyes was 27.88+2.14mm. The mean values of ACD (2.99mm), CCT (0.52mm), WTW (11.68mm), and keratometry (43.62D) were within the normal range. Overall, very weak correlations could be established between AL and CCT (R=0.17, p=0.02), AL and keratometry (R=-0.28, p<0.001), and AL and WTW (R=0.22, p=0.002), while ACD did not relate to AL significantly. The ACD and CCT did not relate significantly to AL in any of the three groups. Keratometry had a weak negative relation with AL in groups 1 and 2, while WTW had a weakly positive relation with AL in group 2 only. No variable had any significant relation with AL in group 3. There is disproportionate elongation of the eyeball in myopic patients with very weak or no correlation between anterior biometry and AL. This discord is more in longer eyes. Such a scenario can be challenging to a refractive surgeon treating highly myopic eyes and needs further evaluation.

Canine central corneal thickness measurements via Pentacam-HR® , optical coherence tomography (Optovue iVue® ), and high-resolution ultrasound biomicroscopy.

To compare central corneal thickness (CCT) values in canine eyes using Pentacam-HR® Scheimpflug imaging (Pentacam), Optovue® iVue spectral-domain optical coherence tomography (SD-OCT), and high-resolution ultrasound biomicroscopy (UBM) and generate normative canine Pentacam CCT values. Twenty-four client-owned dogs (37 eyes) with nondiseased cornea(s) presenting to the Colorado State University Veterinary Teaching Hospital. Corneal images were acquired via Pentacam, SD-OCT, and UBM in the listed order. Machine-calculated values of CCT from Pentacam and SD-OCT were compared to operator-measured values from UBM. Bland-Altman analysis was performed to evaluate agreement between instruments. Mean CCT ± SD measured by Pentacam was 629.73 ± 64.57 μm, by SD-OCT was 610.56 ± 57.48 μm, and by UBM was 689.77 ± 55.93 μm. On average, Pentacam CCT was 19.17 ± 32.90 μm (3%) thicker than SD-OCT and 65.12 ± 44.52 μm (10.3%) thinner than UBM. SD-OCT was on average 82.47 μm (13.5% ) thinner than UBM. The 95% limits of agreement were (-45.31, 83.65), (-152.38, 22.13), and (-126.674, -38.270) for Pentacam vs. SD-OCT, Pentacam vs. UBM, and SD-OCT vs. UBM respectively. All differences were statistically significant (P < 0.01). Considering there is an average of 7.5% normal diurnal variation in canine CCT, a 3.0% difference between Pentacam and SD-OCT values is likely not clinically relevant. However, Pentacam measurements were both statistically and clinically significantly different from UBM and SD-OCT measurements.

Effects of selective serotonin reuptake inhibitors on intraocular pressure and anterior segment parameters in open angle eyes

Purpose: To evaluate the short- and long-term effects of selective serotonin reuptake inhibitors (SSRIs) on intraocular pressure (IOP) and anterior segment parameters in open angle eyes.Materials and methods: This cross-sectional study included 325 eyes of 166 subjects. Subjects were divided into three groups: Group 1 included 116 eyes of 58 patients receiving SSRIs for 1 week–6 months, Group 2 included 102 eyes of 53 patients receiving SSRIs for longer than 6 months and Group 3 included 107 eyes of 55 healthy subjects not receiving any drugs. All of the patients receiving SSRIs were diagnosed as major depressive disorder. All groups were chosen to be similar in terms of age and gender. All patients underwent a detailed ophthalmologic examination including IOP measurement by Goldmann applanation tonometer and gonioscopy. Anterior segment parameters including pupil diameter (PD), central corneal thickness (CCT), anterior chamber depth (ACD), anterior chamber volume (ACV), and anterior chamber angle (ACA) were assessed by a Scheimpflug system.Results: Pupil diameter was significantly larger in patients receiving SSRIs for <6 months and ≥6 months than the control subjects (3.53 ± 0.71 mm, 3.48 ± 0.60 mm versus 3.11 ± 0.72 mm, p < 0.05) but this effect was independent from the duration of SSRI treatment. IOP was significantly lower in patients receiving SSRIs for <6 months and ≥6 months than the control group (16.04 ± 2.17 mm Hg, 16.11 ± 2.13 mm Hg versus 17.34 ± 2.15 mmHg, p < 0.05), but there were no statistically significant differences between the patients receiving SSRIs for <6 months and ≥6 months. There were no statistically significant differences between the patient and the control group in values of CCT, ACD, ACV and ACA. The ACAs were measured between 25° and 55° with Scheimpflug system and also classified as grade 3–4 (Shaffer system) by gonioscopy.Conclusions: Selective serotonin reuptake inhibitors cause mydriasis which is persistent during the treatment. In depression patients with open angle eyes, short- and long-term use of SSRIs leads to decrease in IOP.

Assessment of Corneal Densitometry in Rheumatoid Arthritis Patients.

Objectives:To evaluate corneal densitometry and anterior segment parameters of rheumatoid arthritis (RA) patients and compare these results with those of age-matched healthy control subjects.Materials and Methods:Anterior segment parameters and corneal densitometry of patients with RA and healthy control subjects were assessed by Scheimpflug corneal topography. For densitometry analysis, the 12-mm diameter area of the cornea was subdivided into four concentric radial zones and anterior, central, and posterior layers based on corneal depth. Right eyes of subjects were used for statistical analysis.Results:Twenty-three consecutive patients with RA and 22 healthy control subjects were included in the study. There was no significant difference with regard to age (p=0.487) or gender (p=0.514). When anterior segment parameters of both groups were compared, no significant difference was found (p>0.05). Total corneal densitometry values were statistically higher in the RA group (p=0.030). In addition, when subdivisions of the cornea were evaluated, higher densitometry values were found in the RA group in 0-2 and 2-6 mm radial zones both in the anterior and total depth (p=0.001, p=0.003 for the 0-2 mm zone and p=0.002, p=0.009 for the 2-6 mm zone). Corneal densitometry measurement was not correlated with central corneal thickness or simulated keratometry value in RA patients or healthy control subjects.Conclusion:The corneal densitometry values were higher in RA patients when compared to healthy control subjects, even if they had clinically clear corneas. Corneal densitometry as an objective measure of corneal clarity warrants further studies in order to ascertain its clinical relevance in RA patients.

Comparison of ocular biometric measurements between a new swept-source optical coherence tomography and a common optical low coherence reflectometry

The purpose of the current study was to compare the measurements between a new optical biometer based on swept-source optical coherence tomography (SS-OCT), the OA-2000 (Tomey, Japan), and an optical biometer based on optical low coherence reflectometry (OLCR), the Lenstar (Haag-Streit, Switzerland). Ninety-nine eyes of 99 healthy subjects were included. The axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), aqueous depth (AD), lens thickness (LT), keratometry (K) readings, including flat K (Kf), steep K (Ks), mean K (Km), astigmatism vectors J0, J45 at diameters of 2.5 and 3.0 mm, and white-to-white diameter (WTW) were measured three times each using both biometer in normal eyes by random sequence. Bland-Altman analysis showed good agreement between the SS-OCT and OLCR devices for AL, AD, ACD, LT, with narrow 95% LoA (−0.05 to 0.07 mm, −0.09 to 0.10 mm, −0.10 to 0.09 mm, and −0.06 to 0.22 mm, respectively), and the P values of ACD were both >0.05. The CCT, Kf, Ks, Km, J0, J45 and WTW values provided by the OA-2000 were in good agreement with the Lenstar, and statistically significant differences were detected for some of them but not clinical differences. The agreement was excellent especially for AL.

Impact of polyethylene glycol 400/propylene glycol/hydroxypropyl-guar and 0.1% sodium hyaluronate on postoperative discomfort following cataract extraction surgery: a comparative study

BackgroundUniversal postoperative guidelines for cataract extraction surgery are yet to be introduced. Artificial tears are gaining popularity as an additional integral component of the postoperative regime. The primary objective of this study was to explore the impact of two prevalent artificial tear preparations on postoperative discomfort following cataract extraction surgery.MethodsA total of 180 patients that underwent cataract extraction surgery were randomly divided into three groups according to their postoperative regime: a) Study group 1 (SG1) received a fixed combination of tobramycin and dexamethasone (FCTD) quid for 3 weeks and, additionally polyethylene glycol 400/propylene glycol/hydroxypropyl-guar quid, for 6 weeks, b) Study group 2 (SG2) received FCTD quid for 3 weeks and, additionally 0.1% sodium hyaluronate provided in the COMOD® device quid, for 6 weeks, and, c) Control Group (CG) received only FCTD quid for 3 weeks. The following indexes were evaluated at three postoperative checkpoints: 1) Subjective discomfort index (SDI) derived from four direct 10-scale Likert-type questions that were addressed to the patient and pertained to: a) foreign body sensation (FBS), b) blinking discomfort (BD), c) stinging sensation (SS), d) tearing sensation (TS), 2) Tear break-up time (TBUT), 3) Central corneal thickness (CCT) and, 4) Central Corneal Sensitivity (CCS).ResultsBoth groups showed increased CCT values at the first examination point and reduced CCS values at all examination points. Furthermore, both SGs had better TBUT times at all examination points compared to CG (CG: 8.86 ± 1.08, SG1: 9.59 ± 1.45, CG2: 9.45 ± 1.33, p < 0.05). BD was significantly better in both SGs only at the 1st week of examination, while SDI values were better until the 3rd week and only borderline better at 6th week. Lastly, no significant differences were detected between SGs, regarding all parameters, at all examination points.ConclusionPolyethylene glycol 400/propylene glycol/hydroxypropyl-guar and 0.1% sodium hyaluronate provided in the COMOD® device seem to be equally efficient in alleviating OSD symptoms following cataract extraction surgery and any of them should be routinely added to the postoperative regime.Trial registrationClinicalTrials.gov Identifier: https://clinicaltrials.gov/ct2/show/NCT02558218NCT02558218

Central corneal thickness and intraocular pressure changes after congenital cataract surgery with intraocular lens implantation in children younger than 2 years

To evaluate the change in central corneal thickness (CCT) and intraocular pressure (IOP) preoperatively to postoperatively in children younger than 2years of age having surgery with primary intraocular lens (IOL) implantation for congenital cataract. Tertiary care institute, Chandigarh, India. Prospective case series. Children younger than 2years old who had phacoaspiration with IOL implantation were studied. The preoperative pachymetry and IOP were compared with the postoperative values at 3months, 6months, and 12months. Pachymetry was measured using an ultrasound pachymeter and IOP with a handheld Perkins applanation tonometer. Thirty-one patients (aged 3 to 24months) were analyzed. There were 24 bilateral cases and 7 unilateral cases. The CCT increased significantly from a preoperative value of 529.84μm±11.7 (SD) to apostoperative value of 553±15.5μm at 1year (P=.022). Themean increase in CCT was 23.16μm and in IOP, 2.59mm Hg. The change in CCT correlated with the change in IOP at 1year (P=.011). After cataract surgery, the CCT in pediatric eyes increased significantly. The CCT values were an important consideration in the measurement of IOP in children younger than 2years having cataract extraction with primary IOL implantation.

No differences in central corneal thickness between open-angle and pseudoexfoliation glaucoma patients.

IntroductionMeasurements of intraocular pressure (IOP) with Goldmann applanation tonometry are affected by central corneal thickness (CCT), as thinner corneas underestimate and thicker corneas overestimate the true IOP value. The literature is controversial regarding CCT values in patients with primary open-angle glaucoma (POAG) and exfoliation glaucoma (XFG). The aim of this study was to evaluate CCT in patients with XFG and POAG.MethodsCCT was evaluated with optical coherence tomography (OCT). All participants who were previously diagnosed with either POAG or XFG underwent ophthalmological examinations. Contact lens users and patients with corneal diseases were excluded.ResultsTotally, 145 patients were enrolled in this study. The mean CCT was 535±30.4 µm in patients with POAG and was 536±33.7 µm in patients with XFG. The result was not statistically significant (P=0.98). The mean age for all participants was 73.8±7.7 years. The study included totally 61 women and 84 men. The two groups were similar in their demographic data, and mean deviation was the only parameter that differed statistically when comparing POAG with XFG (P=0.02).ConclusionOur data indicate that patients with XFG do not have thinner corneas than those with POAG, and therefore, CCT can not explain why they progress differently.

Cataracte céruléenne congénitale

To evaluate the change in central corneal thickness (CCT) and intraocular pressure (IOP) preoperatively to postoperatively in children younger than 2 years of age having surgery with primary intraocular lens (IOL) implantation for congenital cataract.Tertiary care institute, Chandigarh, India.Prospective case series.Children younger than 2 years old who had phacoaspiration with IOL implantation were studied. The preoperative pachymetry and IOP were compared with the postoperative values at 3 months, 6 months, and 12 months. Pachymetry was measured using an ultrasound pachymeter and IOP with a handheld Perkins applanation tonometer.Thirty-one patients (aged 3 to 24 months) were analyzed. There were 24 bilateral cases and 7 unilateral cases. The CCT increased significantly from a preoperative value of 529.84 μm ± 11.7 (SD) to a postoperative value of 553 ± 15.5 μm at 1 year (P = .022). The mean increase in CCT was 23.16 μm and in IOP, 2.59 mm Hg. The change in CCT correlated with the change in IOP at 1 year (P = .011).After cataract surgery, the CCT in pediatric eyes increased significantly. The CCT values were an important consideration in the measurement of IOP in children younger than 2 years having cataract extraction with primary IOL implantation.

Effect of High Altitude Exposure on Intraocular Pressure Using Goldmann Applanation Tonometry.

The aim of the study was to quantify changes of intraocular pressure (IOP) during exposure to 4559 m using the state-of-the-art method of Goldmann applanation tonometry for IOP measurement and to detect correlations between IOP and acute mountain sickness (AMS) in a prospective manner. IOP was measured using a Goldmann applanation tonometer AT 900® (Haag-Streit, Switzerland) and central corneal thickness (CCT) with the anterior segment module of a Spectralis™ HRA+OCT® device (Heidelberg Engineering, Germany) at baseline and high altitude. Assessment of AMS was performed using the Lake Louise and AMS-C questionnaires, and Pearson's correlation coefficient was calculated for association between IOP and AMS. Raw IOP values at high altitude were not significantly changed compared to baseline. IOP adjusted to the increase in CCT at high altitude, which is known to alter IOP levels, showed a significant reduction for corrected IOP values on day 3 of exposure (morning -2.1 ± 1.2 mmHg; evening -2.3 ± 1.1 mmHg; p < 0.05). No correlation of IOP with AMS or clinical parameters (heart rate and SpO2) at high altitude was noted. IOP showed a significant reduction of IOP levels when corrected for increased CCT values at high altitude. Furthermore, the prospective measurement of IOP is not useful in diagnosing AMS or for the prediction of more severe high altitude related illnesses as the decrease in IOP and symptoms of AMS do not correlate during altitude exposure.

Analysis of the learning curve for pre‐cut corneal specimens in preparation for lamellar transplantation: a prospective, single‐centre, consecutive case series prepared at the Lions New South Wales Eye Bank

This study is the first paper to establish a learning curve by a single technician. Preparation of pre-cut corneal endothelial grafts commenced at Lions New South Wales Eye Bank in December 2014. The primary objective of this study was to review the safety and reliability of the preparation method during the first year of production. This is a hospital-based, prospective case series. There were 234 consecutive donor corneal lenticules. Donor lenticules were prepared by a single operator using a linear cutting microkeratome. Immediately prior to cutting, central corneal thickness values were recorded. Measurements of the corneal bed were taken immediately following lenticule preparation. Outcomes were separated by blade sizes, and intended thickness was compared to actual thickness for each setting. Early specimens were compared to later ones to assess for a learning curve within the technique. The main parameter measured is the mean difference from intended lamellar cut thickness. The mean final cut thickness was 122.36 ± 20.35 μm, and the mean difference from intended cut was 30.17 ± 37.45 μm. No significant difference was found between results achieved with early specimens versus those achieved with later specimens (P = 0.425). Thin, reproducible endothelial grafts can routinely be produced by trained technicians at their respective eye banks without significant concerns for an extended learning curve. This service can reduce perioperative surgical complexity, required surgical paraphernalia and theatre times. The consistent preparation of single-pass, ultrathin pre-cut corneas may have additional advantages for surgeons seeking to introduce lamellar techniques.

Effects of Mydrin eye‐drops on central corneal thickness values in adult patients with myopia

ObjectiveThis study aimed to evaluate the effect of Mydrin eye‐drops on central corneal thickness values and investigate the duration of the effect.MethodsIn this prospective randomised self‐controlled study, we enrolled 60 myopic patients (120 eyes) undergoing corneal laser refractive surgery. The central corneal thickness was measured before and one and four hours after administration of Mydrin eye‐drops (major components are tropicamide and phenylephrine hydrochloride) using the Orbscan II anterior segment analysis system and a SP-2000P non‐contact specular microscope, respectively.ResultsUsing the Orbscan II system, the baseline central corneal thickness (545 ± 27 µm) was significantly lower than that at one hour after Mydrin eye‐drop application (559 ± 31 µm; p < 0.001); it was comparable to that at four hours post‐Mydrin eye‐drop administration (544 ± 26 µm; p < 0.74). Measured by non‐contact specular microscopy, the baseline central corneal thickness (508 ± 26 µm) was significantly lower than that at one hour after Mydrin eye‐drop application (521 ± 29 µm; p < 0.001); it was comparable to that at four hours after Mydrin eye‐drop administration (506 ± 24 µm; p = 0.62). A significant difference was observed in the central corneal thickness at one and four hours after Mydrin eye‐drop application by both methods (p < 0.001). Bland–Altman plots showed agreement between the measurements by the two methods at different times.ConclusionCentral corneal thickness increases one hour after topical application of Mydrin eye‐drops and is normalised at four hours following the administration of the drops. For patients scheduled to undergo excimer laser corneal refractive surgery, the central corneal thickness should be measured before or four hours after administration of Mydrin eye‐drops.

Central corneal thickness in glaucoma

The purpose of this review is to summarize the role of central corneal thickness (CCT) in the clinical management of a glaucoma patient. The prognostic value of CCT is well recognized in patients with ocular hypertension. However, its predictive value in other glaucoma suspects and patients with established glaucoma is less certain. Tonometry artefacts can result from variations in CCT. However, an adequately validated correction algorithm for Goldmann applanation tonometry measurements does not exist. Newer methods of tonometry are potentially less influenced by CCT but are limited in their clinical use. There may also be biological and genetic associations between corneal thickness and glaucoma. Demographics, environmental factors, glaucoma treatment and the measurement device used have a significant influence on CCT, and should be considered when interpreting the effect of cornea thickness in patients with glaucoma. New measurements of the biomechanical properties of the cornea are likely to be better approximations of the globe biomechanics than CCT, but these require further evaluation. The clinical significance of CCT is well recognized in the context of glaucoma diagnosis and management, though the extent of its importance remains debatable. Corneal biomechanical properties may be more significantly associated with glaucoma than CCT.