Erhan Özyol

Posterior corneal elevation and back difference corneal elevation in diagnosing forme fruste keratoconus in the fellow eyes of unilateral keratoconus patients

Purpose To evaluate posterior corneal elevation and back difference corneal elevation in patients with keratoconus in 1 eye and forme fruste keratoconus in the fellow eye. Setting Kudret Eye Hospital, Ankara, Turkey. Design Case‐control study. Methods This study retrospectively reviewed patients with keratoconus in 1 eye and forme fruste keratoconus in the fellow eye and eyes of normal subjects. All subjects were evaluated with a rotating Scheimpflug imaging system (Pentacam), including sagittal and tangential anterior curve analysis, keratometry, and posterior elevation. The back difference elevation values were extrapolated from the difference maps of the Belin‐Ambrosió enhanced ectasia display of the Scheimpflug system. The receiver operating characteristic (ROC) curves were analyzed to evaluate the sensitivity and specificity of the parameters. Results The corneal power, pachymetric progression index, and posterior corneal elevation (posterior elevation and back difference elevation) measurements were statistically significantly higher in eyes with keratoconus or forme fruste keratoconus than in eyes of normal control subjects (P<.05). Using ROC analysis, the area under the curve values of mean keratometry, steepest point on the tangential curve, minimum corneal thickness, pachymetric progression index, Ambrósio’s relational thickness, posterior elevation, and back difference elevation to distinguish forme fruste keratoconus from control subjects were 0.51, 0.84, 0.65, 0.81, 0.72, 0.68, and 0.76, respectively. Conclusions Back difference elevation was better than posterior elevation in diagnosing forme fruste keratoconus. However, as sole parameters, both had limited sensitivity and specificity to differentiate between forme fruste keratoconus eyes and normal control eyes. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Hydro-visco-implantation Technique for Wound-assisted Foldable Intraocular Lens Implantation During Microincision Cataract Surgery

We have described a hydro-visco-implantation technique (simultaneous use of sodium hyaluronate and balanced salt solution) for wound-assisted intraocular lens (IOL) implantation and passive removal of ophthalmic viscosurgical device (OVD). In the technique, the capsular bag was filled approximately up to half with OVD, and anterior chamber was formed by bimanual irrigation cannula with continuous irrigation mode from the side port. Sometimes after adequate tonus is provided, continuous mode could be off to reduce wash effect on OVD during injection of IOL. Injection of foldable IOL with the support of wound edges was completed. While the continuous irrigation mode was on, firm downward pressure was applied with the tip of aspiration canula to the posterior lip of main incision, and dynamic outflow was created, and viscoelastic material was removed from the eye.

Biocompatibility of Intraocular Lenses

The performance of an intraocular lens is determined by several factors such as the surgical technique, surgical complications, intraocular lens biomaterial and design, and host reaction to the lens. The factor indicating the biocompatibility of an intraocular lens is the behavior of inflammatory and lens epithelial cells. Hence, the biocompatibility of intraocular lens materials is assessed in terms of uveal biocompatibility, based on the inflammatory foreign-body reaction of the eye against the implant, and in terms of capsular biocompatibility, determined by the relationship of the intraocular lens with residual lens epithelial cells within the capsular bag. Insufficient biocompatibility of intraocular lens materials may result in different clinical entities such as anterior capsule opacification, posterior capsule opacification, and lens epithelial cell ongrowth. Intraocular lenses are increasingly implanted much earlier in life in cases such as refractive lens exchange or pediatric intraocular lens implantation after congenital cataract surgery, and these lenses are expected to exhibit maximum performance for many decades. The materials used in intraocular lens manufacture should, therefore, ensure long-term uveal and capsular biocompatibility. In this article, we review the currently available materials used in the manufacture of intraocular lenses, especially with regard to their uveal and capsular biocompatibility, and discuss efforts to improve the biocompatibility of intraocular lenses.

The Efficacy of a Latanoprost/Timolol Fixed Combination Versus Latanoprost and Timolol Gel-forming Solution Unfixed Combination on Daytime Intraocular Pressure.

Purpose:To evaluate the effect of a latanoprost/timolol fixed combination (LTFC) versus a latanoprost and timolol gel-forming solution unfixed combination (LTuFC) on daytime intraocular pressure (IOP) levels and fluctuations. Methods:This was an 8-week, randomized, parallel-group study. Ninety eyes of 90 patients diagnosed with primary open-angle glaucoma or ocular hypertension that were insufficiently controlled with latanoprost monotherapy were enrolled. Randomized patients received either a single evening dose of LTFC or unfixed combination of latanoprost administered once daily in the evening and timolol gel-forming solution administered once daily in the morning without a washout period. IOP measurements were taken at 8 AM, 11 AM, 2 PM, and 5 PM. The mean IOP, daytime IOP measurements, and fluctuation in IOP were assessed at weeks 4 and 8. Results:The mean IOP reduction from baseline to each visit was significant in both groups (P<0.01). There was a significant difference in the mean IOP between groups at week 4 (P=0.0021). At week 8, the mean IOP reduction was 3.2±2.1 and 5.7±3.2 mm Hg in LTFC and LTuFC groups, respectively, and the difference was significant (P=0.001). A decrease in the daytime IOP fluctuation was observed in both groups over time, but the decrease in each group was not significant. At week 8, the mean IOP measurements at 8 AM, 11 AM, 2 PM, and 5 PM in LTuFC group were significantly lower than in the LTFC group (P=0.024, 0.0001, 0.0008, and 0.0011, respectively). Conclusions:The concomitant use of latanoprost and timolol gel-forming solution leads to a larger additional IOP reduction and lower daytime IOP levels as compared with the fixed combination.

Assessment of Corneal Backward Light Scattering in Diabetic Patients

Objectives: To analyze corneal backward light scattering differences in patients with type 2 diabetes mellitus. Methods: We enrolled 43 eyes from 43 diabetic patients and 40 eyes from 40 healthy controls. Corneal backward light scattering was evaluated using densitometry measurements from different corneal layers and zones obtained using Scheimpflug tomography (PentacamHR). Results: When densitometry values were divided by depth, anterior layer of diabetic corneas displayed significantly higher corneal backward light scattering values than controls (32.05, 95% confidence intervals [CI], 31.02–33.08 vs. 29.18, 95% CI, 27.60–30.76, P=0.024). Corneal densitometry measurements were also significantly higher in diabetic eyes compared with control eyes, when considered by concentric zones of total cornea in the 0 to 2 mm (21.65, 95% CI, 20.28–23.01 vs. 18.87 95% CI, 18.49–19.25, P=0.020), and anterior layer in the 0 to 2 mm (27.3, 95% CI, 25.04–29.56 vs. 22.31, 95% CI, 20.57–24.05, P<0.001), 2 to 6 mm (26.2, 95% CI, 24.99–27.41 vs. 22.4, 95% CI, 20.18–24.62, P<0.001) and 6 to 10 mm (32.19, 95% CI, 29.98–34.40 vs. 27.2, 95% CI, 25.39–29.01, P=0.022). There was excellent positive correlation between anterior total corneal densitometry measurements and duration of diabetes (r=0.802, P<0.001), although no significant correlation was observed with anterior total corneal densitometry measurements and hemoglobin A1c levels (r=0.080, P=0.621) in diabetic eyes. Conclusions: Backward light scattering values from the anterior layer of the cornea is greater in diabetic eyes than in controls. Anterior total corneal densitometry measurements show positive correlation with the duration of diabetes.

Intraocular pressure dynamics with prostaglandin analogs: a clinical application of water-drinking test

Aim To evaluate the clinical applicability of the water-drinking test in treatment-naive primary open-angle glaucoma patients. Methods Twenty newly diagnosed primary open-angle glaucoma patients and 20 healthy controls were enrolled in this prospective study. The water-drinking test was performed at baseline and 6 weeks and 3 months after prostaglandin analog treatment. Peak and fluctuation of intraocular pressure (IOP) measurements obtained with the water-drinking test during follow-up were analyzed. Analysis of variance for repeated measures and paired and unpaired t-tests were used for statistical analysis. Results The mean baseline IOP values in patients with primary open-angle glaucoma were 25.1±4.6 mmHg before prostaglandin analog treatment, 19.8±3.7 mmHg at week 6, and 17.9±2.2 mmHg at month 3 after treatment. The difference in mean baseline IOP of the water-drinking tests was statistically significant (P<0.001). At 6 weeks of prostaglandin analog treatment, two patients had high peak and fluctuation of IOP measurements despite a reduction in baseline IOP. After modifying treatment, patients had lower peak and fluctuation of IOP values at month 3 of the study. Conclusion Peak and fluctuation of IOP in response to the water-drinking test were lower with prostaglandin analogs compared with before medication. The water-drinking test can represent an additional benefit in the management of glaucoma patients, especially by detecting higher peak and fluctuation of IOP values despite a reduced mean IOP. Therefore, it could be helpful as a supplementary method in monitoring IOP in the clinical practice.

Endophthalmitis and clear corneal cataract incisions.

Dear Sir, I have read the article by Yoon et al.,[1] with great interest. The authors have rightly compared two differently located incisions for right-handed surgeons. However, I would like to make a few observations. The first point that I want to make a stand on is endophthalmitis. Several risk factors are known to be associated with endophthalmitis following cataract surgery. The incision location is one of the important factors that may increase the risk of endophthalmitis. As well known, the recent literatures have shown the increased risk of endophthalmitis with clear corneal temporal incisions. A temporal location may be potentially more problematic, as these incisions are not protected by the eyelid or conjunctiva, and thus have increased exposure to bacteria residing in the tear film and eyelid margins.[2,3] The pure nasal corneal incision is out of this comparison, as it is not widely used. The nasal incisions may be more risky for endopthalmitis due to near anatomical relation with both inferior and superior punctums. It should be considered by right-handed surgeons, especially for nasal incisions. In addition, in this study, the interval between procedures for patients is just one day. We know from the literature that acute-onset endophthalmitis after cataract surgery begins within 2-5 days.[4,5] Based on this knowledge, the interval between surgeries should be at least 5 days for bilateral cataract surgery. However, the authors indicate that a single suture was used for corneal incisions and removed 7 days after surgery. Although it may be appropriate to decrease the risk of endophthalmitis, there is no study on the subject. In addition, in practice many surgeons do not use the suture for clear corneal incisions. I think, the take-home message should be given for nasal incisions by considering the endophthalmitis. Yoon and associates draw our attention to the astigmatism-neutral cataract surgery through temporal and nasal incisions, especially in Asian eyes. However, in this article, axis schift was not evaluated by authors. Based on our experience, symmetric corneal incisions (superior-superior, temporal-temporal, and superiortemporal-superiortemporal) may be more favorable or more acceptable to keep the corneal axis symmetry after bilateral cataract surgery. As mentioned in the article, the optical center is located more nasally and inferiorly, and axis schift is affected by the size and location. We know that horizontal meridian is approximately 1 mm wider than vertical length. When it is considered with the location of optical center, the temporal and nasal incisions are the farthest locations to each other, although they are on the same horizontal axis. A nasal incision is closer to the corneal apex than a temporal incision, which could explain the greater effect on the central corneal curvature and may cause the more axis schift compared with temporal incision. I think, it would be better to evaluate not only the corneal astigmatism but also axis schift. In my opinion, ideally, the incision locations in right and left eyes should be closer as much as possible for right-handed surgeons to minimize the postoperative axis asymmetry. Superior nasal incision for left eye and superior temporal incision for right eye that are mostly chosen by right-handed surgeons might be a better option, if the incisions are located closer to vertical axis as much as possible.

Evaluation of inflammation and intraocular pressure after cataract surgery

Evaluation of inflammation and intraocular pressure after cataract surgery Lane and Holland have rightly compared 2 medications, loteprednol etabonate 0.5% and prednisolone acetate 1.0%, after cataract surgery. However, we would like to make a few observations. The intraocular pressure (IOP) after cataract surgery is affected by preoperative levels, the retained ophthalmic viscosurgical device (OVD), and the central corneal thickness (CCT). We know that CCT increases after phacoemulsification and recovers over time. Based on this knowledge, it is clear that postoperative corrected IOP is different from the uncorrected IOP. In the current study, we do not know that the CCT increase was the same in the 2 groups. The preoperative CCT level, effective phaco time, surgical time, use of OVD, and many other factors may affect the increase in CCT and its course. In addition, the amount of retained OVD can vary in multicenter studies. In the early postoperative period, the retained OVD may affect the IOP. The elevation of IOP due to OVD is marked at 6 to 24 hours, and the effect of OVD on IOP may take up to 72 hours. Therefore, we think evaluating corrected IOP early postoperatively and then 24 to 48 hours later will providemore clear results about the efficacy of loteprednol etabonate 0.5% and prednisolone acetate 1.0% on IOP changes.

Overnight orthokeratology with two brands of reverse-geometry contact lenses.

PURPOSE To evaluate the refractive and corneal topographical changes of overnight orthokeratology in myopia with two brands of contact lenses. METHODS Fourty-four eyes of 22 myopic patients with manifest refraction spherical equivalent (MRSE) of -1.00 to -5.00 D (cylinder≤-1.0) were fitted with either DreamLens (Hanita Lenses Investments, Hanita, Israel) (group A) or Rinehart-Reeves (R&R; Danker Laboratories, Sarasota, FL) (group B) reverse-geometry lenses. Each subject eye was evaluated in regards to the uncorrected and corrected distance visual acuities, manifest refraction, slit lamp biomicroscopy, and corneal topography at each follow-up examination. RESULTS The follow-up was 1 year. For groups A and B, the mean uncorrected distance visual acuity was -0.02±0.10 logMAR (20/20) and -0.08±0.12 logMAR (20/20) respectively at year-1 examination. The mean MRSE decreased from -2.70±0.9D to -0.50±0.08D in group A and -3.1±1.1 to -0.62±0.18D in group B at week-1; and remained stable thereafter in each group. For both groups, starting with week-1, the mean anterior best-fit sphere (ABFS) was statistically significantly flatter from baseline. A high correlation was found between the change in apical corneal power (ACP) and MRSE (r1=0.79, r2=0.71), and there was a good correlation between the change in ABFS and MRSE (r1=0.67, r2=0.64) in both groups. No significant ocular adverse events were observed during study. CONCLUSIONS Both types of contact lenses safely and effectively decreased the myopic refractive error at 1 year follow-up. The refractive effect was mainly induced by the changes in the anterior corneal shape and the ACP.

The Interaction of Nepafenac and Prostaglandin Analogs in Primary Open-angle Glaucoma Patients.

Purpose:To investigate the effect of nepafenac on intraocular pressure (IOP) in primary open-angle glaucoma (POAG) patients treated with prostaglandin (PG) analogs. Materials and Methods:This prospective clinical study included 35 patients who had been receiving latanoprost (n=12), travoprost (n=12), or bimatoprost (n=11) for POAG. Nepafenac 0.1% and placebo drops were administered to the right and left eyes of patients, respectively, 3 times a day for 7 days. IOP measurements were taken at 9:00 AM, 12:00 PM, and 4:00 PM at baseline and all consecutive visits. The visits were scheduled on days 1 and 7 during treatment and 1 and 7 days after discontinuation of the treatment. Results:The mean age of the patients was 60.28±7.51 years (range, 48 to 75 y). The baseline IOP was similar in the nepafenac and placebo groups (15.33±1.45 vs. 15.41±1.41, respectively, P>0.05). The decrease in the mean IOP was significant in the nepafenac group compared with the placebo group throughout the treatment period (P<0.001). After the discontinuation of nepafenac treatment, the mean IOP became similar with the placebo group from the first day (P>0.05). The change in mean IOP was not significant between the PG subgroups during treatment and discontinuation periods (P=0.712). Conclusions:Nepafenac potentiates the IOP-lowering effects of 3 different PG analogs in POAG patients.