Afsun Sahin

Corneal biomechanical changes in diabetes mellitus and their influence on intraocular pressure measurements.

PURPOSE To investigate possible corneal biomechanical changes in patients with diabetes mellitus and understand the influence of such changes on intraocular pressure measurements. METHODS The study group was composed of 120 eyes from 61 healthy control subjects and 81 eyes from 43 diabetic subjects. IOP was measured first with an ocular response analyzer (ORA) and subsequently with a Goldmann applanation tonometer (GAT). Central corneal thickness (CCT) was measured with an ultrasonic pachymeter attached to the ORA. Axial length (AL), anterior chamber depth (ACD), and keratometry readings were acquired with partial coherence laser interferometry during the same visit before all IOP and CCT determinations were made. RESULTS Corneal hysteresis (CH) was found to be significantly lower in diabetic patients when compared with healthy control subjects (9.51 +/- 1.82 mm Hg vs. 10.41 +/- 1.66 mm Hg, P < 0.0001). There was no significant difference in terms of corneal resistance factor (CRF; P = 0.8). Mean CCT, GAT IOP, Goldmann-correlated IOP (IOPg), and corneal-compensated IOP (IOPcc) were significantly higher in diabetic patients than in healthy control subjects (P = 0.01 for CCT, P < 0.0001 for GAT IOP, IOPg, and IOPcc). CONCLUSIONS Diabetes affects corneal biomechanics and results in lower CH values than those in healthy control subjects, which may cause clinically relevant high IOP measurements independent of CCT.

Reproducibility and tolerability of the ICare rebound tonometer in school children.

PurposeTo establish the intraobserver and interobserver reliability of the rebound tonometer (RBT) in healthy schoolchildren and to test patient tolerance in an unanesthetized eye. Subjects and MethodsTo examine the reproducibility of the RBT, 2 experienced ophthalmologists undertook 3 consecutive intraocular pressure (IOP) measurements with the RBT without an anesthetic in 304 eyes of 152 healthy schoolchildren. Any pain or discomfort experienced by the children was recorded. Intraobserver and interobserver reliabilities were established by calculating correlation coefficients (r). ResultsOf the 152 patients, 78 (51.3%) were males and 74 (48.7%) were females. The mean patient age was 11.2±2.6 years (range: 7 to 15 y). Mean IOP values obtained by examiners 1 and 2 were 16.48±2.82 mm Hg and 17.27±3.27 mm Hg for the right eyes and 17.15±3.36 mm Hg and 17.06±3.21 mm Hg for the left eyes. Intraobserver correlation coefficients for examiner 1 were 0.970 for the right eyes and 0.974 for the left eyes. For examiner 2, intraobserver correlation coefficients were 0.963 for the right eyes and 0.970 for the left eyes. The interobserver correlation coefficients were 0.798 for the right eyes and 0.858 for the left eyes (all P<0.0001). With the RBT, 98.6% of the subjects felt no pain and/or discomfort. ConclusionsMeasurement of IOP with the RBT is a highly reproducible method in schoolchildren showing high intraobserver and interobserver correlation and it seems to be very comfortable when performing IOP measurements in schoolchildren without an anesthetic.

Measurement of angle kappa with synoptophore and Orbscan II in a normal population.

PURPOSE To obtain normative values of angle kappa in a normal population by synoptophore and Orbscan II and to compare the reliability of these devices. METHODS Three hundred consecutive healthy individuals were enrolled in the study. A complete orthoptic and ophthalmologic examination was performed. Synoptophore and Orbscan II corneal topography were used to measure angle kappa. To evaluate the association of the angle kappa and refraction measures, individuals were further classified according to the degree of myopia and hyperopia. The spherical equivalent error measures were grouped into six categories: > or = -3.00 diopters (D); -2.75 to -1.50 D; -1.25 to -0.50 D; +0.50 to +1.25 D; +1.50 to +2.75 D; and > or = +3.00 D. Paired t test and Pearsons correlation test were used for statistical analysis. RESULTS The mean age of the individuals was 28.74 +/- 1.63 years (range: 20 to 40 years). The angle kappa values obtained by synoptophore and Orbscan II were normally distributed. In the myopic group, angle kappa values decreased significantly towards negative refractive errors. In contrast, a correlation existed between large positive angles and positive refractive errors in the hyperopic group. Angle kappa values obtained by Orbscan II were significantly higher in all groups when compared to synoptophore (P < .0001). A significant correlation was noted between synoptophore and Orbscan II measurements (r = 0.932, P < .0001). CONCLUSIONS A significant correlation exists between positive refractive errors and large positive angle kappa values. Refractive surgeons must take into account angle kappa, especially in hyperopic patients, to avoid complications related to decentration of the ablation zone.

Comparison of the rebound tonometer with the Goldmann applanation tonometer in glaucoma patients

Purpose:  To determine the agreement between the measurement of intraocular pressure (IOP) by the rebound tonometer (RBT) and by the Goldmann applanation tonometer (GAT) and to find out the effect of central corneal thickness (CCT) values on IOP measurements in glaucoma patients.

A comparative study between diode laser cyclophotocoagulation and the Ahmed glaucoma valve implant in neovascular glaucoma: a long-term follow-up.

BackgroundTo compare the efficacy, safety, and long-term results of intraocular pressure (IOP) reduction by diode laser contact cyclophotocoagulation (DCPC) and Ahmed glaucoma valve (AGV) implant in cases of neovascular glaucoma. MethodsA total of 66 eyes of 66 patients with neovascular glaucoma were prospectively assigned to either DCPC or AGV implantation. All patients underwent a baseline complete ophthalmologic examination and IOP measurement by Goldmann applanation tonometry before and after 1,3, 6, 12, and 24 months follow-up. Complications and the number of medications were recorded. ResultsMean age of the patients was 60.0±11.7 years (range: 20 to 85) in the DCPC group and 57.2±10.3 years (range: 20 to 85) in the AGV group. The preoperative IOP was 43.4±11.9 mm Hg and 43.3±7.4 mm Hg for the DCPC and AGV group, respectively (P>0.05). The postoperative IOP was 16.5±11.3 mm Hg and 22.09±7.6 mm Hg for the DCPC and AGV groups, respectively (P>0.05) at the last visit. Kaplan-Meier survival analysis showed a probability of success at 24 months of 61.18% and 59.26% for the DCPC and AGV groups (P>0.05). All the patients had a visual acuity of hand movement or worse preoperatively. Visual acuity decreased in 6 eyes (24%) in the DCPC group and 9 eyes (27%) in AGV group. Complications included anterior segment inflammation in 5 eyes (20%), neurotrophic keratitis in 2 eyes (8%), and hypotony in 3 eyes (15%) in the DCPC group and hyphema in 5 eyes (15%) and tube occlusion in 3 eyes (9%) in AGV group. ConclusionsThere was no significant difference in the success rate between the DCPC and AGV implantation in neovascular glaucoma treatment. However, DCPC is less time consuming and easier method for lowering IOP in patients with neovascular glaucoma.

The influence of central corneal thickness and corneal curvature on intraocular pressure measured by tono-pen and rebound tonometer in children.

PurposeTo find out the effect of central corneal thickness (CCT) and radius of the corneal curvature on intraocular pressure (IOP) measurements using rebound tonometer (RBT) and Tono-Pen in healthy schoolchildren. MethodsIOP was measured with Tono-Pen and RBT, respectively, in 165 healthy schoolchildren with a mean age 9.8±3.1 (range: 7 to 12 y) years. Corneal radius of curvature (in mm) was determined using a keratometer before CCT and IOP measurements. CCT was measured using an ultrasonic pachymeter after all IOP determinations had been made. The effect of CCT, radius of the corneal curvature, and sex on measured IOP was evaluated by linear regression analysis. ResultsThe mean IOP readings were 17.47±2.7 mm Hg using Tono-Pen, and 16.81±3.1 mm Hg using RBT. Tono-Pen measured IOP values slightly greater than that of RBT (P=0.006). Mean CCT was found to be 561.37±33 μm. A significant association between measured IOP and CCT was found with each device (r=0.220 for the Tono-Pen, r=0.373 for the RBT; P=0.006 for the Tono-Pen and P<0.0001 for the RBT). The IOP increased 2.2 and 3.7 mm Hg for every 100-μm increase in CCT for the Tono-Pen and the RBT, respectively. The relation between IOP and CCT was not different for boys and girls. Mean radius of the corneal curvature readings was 7.68±0.41 mm (42.75±1.37 D) for both sexes. There was no significant relationship between either the mean corneal curvature readings, or CCT and IOP (r=0.02; P=0.4 for CCT and r=0.01; P=0.5 for IOP). ConclusionsBoth the Tono-Pen and RBT have a systematic error in IOP readings caused by its dependence on CCT. The CCT measurements should be considered to ensure proper interpretation of IOP measurements in children, like in adults. The corneal radius of curvature had no significant effect on measured IOP with each device.

Retinopathy of prematurity: screening guidelines need to be reevaluated for developing countries.

Purpose. Timely screening of premature babies is an important initial step in the management of retinopathy of prematurity (ROP) as earlier treatment results in improved visual prognosis. Screening criteria for ROP currently recommended by the American Academy of Pediatrics may not be applicable in developing countries. The aim of the present study is to find out the incidence of ROP in infants with a gestational age (GA) of ≥32 weeks in Eskisehir, Turkey, to provide information to assist in determining screening criteria. Methods. A total of 96 infants with a GA of 32–35 weeks who were referred for ROP between January 1, 2004, and December 31, 2008, were studied. ROP screening, follow-up, and appropriate therapies were applied. Results. During ROP screening, there were 42 of 96 (43.8%) infants with no ROP. A total of 54/96 (56.2%) infants were noted to have ROP. Among all infants, 7 (7.3%) had threshold ROP. Two infants with threshold disease were born at the 32nd, 2 at the 33rd, and 3 at the 34th week of gestation. The mean birthweight was 1857.9 (range 1060–3200) grams. Conclusions. In our study, it was found that more mature infants may also develop threshold ROP and require early treatment. After more information is gained and widespread screening, screening protocols covering more mature infants can be designed especially for developing countries.

The relationship between corneal biomechanical properties and confocal microscopy findings in normal and keratoconic eyes.

Purpose: To investigate the relationship between corneal biomechanical properties and confocal microscopy (CM) findings in normal and keratoconic eyes. Methods: The study consisted of 28 eyes of 28 healthy volunteers and 23 eyes of 15 patients with keratoconus. The diagnosis of keratoconus was made with corneal topography and clinical findings. The corneal hysteresis (CH) and corneal resistance factor (CRF) were measured by the ocular response analyzer. In vivo CM was performed with NIDEK Confoscan 3. CH and CRF were compared with corneal morphological findings (detailed cell counts of endothelial, stromal, and epithelial cells) in vivo. Results: CH was 10.1 ± 1.3 mm Hg in normal eyes and 7.4 ± 1.5 mm Hg in keratoconic eyes (P < 0.0001). CRF was 10.1 ± 1.8 mm Hg in normal eyes and 6.2 ± 1.4 mm Hg in keratoconic eyes (P < 0.0001). CH and CRF were negatively correlated with full-thickness stromal keratocyte density (P < 0.01; r = −0.52 and P < 0.001; r = −0.67, respectively) in healthy eyes. Keratocyte density of the posterior half of the stroma was found to be significantly related with CRF in healthy eyes (β = −0.404; P = 0.01). There was no significant relationship among CH, CRF, and CM findings in eyes with keratoconus. Conclusions: There is a significant relationship between CRF and keratocyte density of the posterior half of the stroma in healthy eyes. Our results suggest that corneal elasticity is related to not only stromal matrix but also cellular structure of the cornea.

Topical cyclosporine a in the treatment of superior limbic keratoconjunctivitis: a long-term follow-up.

Purpose: To report the efficacy of topical cyclosporine A (CsA) 0.05% drops (Restasis; Allergan, Irvine, CA) in the treatment of superior limbic keratoconjunctivitis (SLK). Methods: Seven patients with SLK refractory to corticosteroid drops and topical silver nitrate application were treated with 0.05% topical CsA 4 times a day, preservative-free artificial tears, and a lubricant ointment. The patients were evaluated for symptomatic and clinical improvement after 2 weeks, 1 month, 3 months, 6 months, and in 6 patients, >12 months. Results: After 2 weeks of topical CsA treatment, symptoms of foreign-body sensation, irritation, and photophobia and signs of conjunctival hyperemia, tarsal papillary reaction, and filamentous keratopathy improved remarkably in all patients. The patients had some burning of short duration after administration of topical CsA. However, none of them suffered from systemic or serious local side effects. After cessation of the topical CsA treatment, 6 patients were followed up for at least 6 months. In this period, the patients continued using lubricant agents. Three patients (50%) showed signs of recurrence after 3 months, and topical CsA was restarted. The clinical findings improved again within a 2-week period, and none of these patients needed further use of topical steroids. Conclusions: Topical CsA 0.05% can be effective in patients with SLK who do not respond to other treatment modalities. It can also be used in the long term to prevent recurrences during treatment and to avoid steroid dependency and the side effects of steroids.

Intraocular pressure values obtained by ocular response analyzer, dynamic contour tonometry, and goldmann tonometry in keratokonic corneas.

PurposeTo determine the agreement between dynamic contour tonometer (DCT), Goldmann applanation tonometer (GAT), and Ocular Response Analyzer (ORA) in keratoconic corneas and to find out the effect of corneal biomechanics on intraocular pressure (IOP) measurements obtained by these devices. Subjects and MethodsIOP was measured with the ORA, DCT, and GAT in random order in 120 eyes of 61 keratoconus patients. Central corneal thickness (CCT) and keratometry were measured after all IOP determinations had been made. The mean IOP measurement by the ORA and DCT was compared with the measurement by the GAT, using Student t test. Bland-Altman analysis was performed to assess the clinical agreement between these methods. The effect of corneal hysteresis (CH), corneal resistance factor (CRF), and CCT on measured IOP was explored by multiple backward stepwise linear regression analysis. ResultsThe mean±SD patient age was 30.6±11.2 years. The mean±SD IOP measurement obtained with GAT, ORA Goldmann-correlated IOP (IOPg), ORA corneal-compensated IOP (IOPcc), and DCT was 10.96±2.8, 10.23±3.5, 14.65±2.8, and 15.42±2.7 mm Hg, respectively. The mean±SD CCT was 464.08±58.4 microns. The mean difference between IOPcc and GAT (P<0.0001), IOPcc and DCT (P<0.001), GAT and DCT (P<0.0001), IOPg and GAT (P<0.002), and IOPg and DCT (P<0.0001), was highly statistically significant. In multivariable regression analysis, DCT IOP and GAT IOP measurements were significantly associated with CH and CRF (P<0.0001 for both). ConclusionsDCT seemed to be affected by CH and CRF, and the IOP values tended to be higher when compared with GAT. ORA-measured IOPcc was found to be independent of CCT and suitable in comparison to the DCT in keratoconic eyes.