Contact Lens and Anterior Eye

Introduction. Keratoconus and related corneal ectatic disorders are typically managed with corneal rigid gas permeable contact lenses (CRGPcl). When these are unsuccessful patients may be fitted with scleral rigid gas permeable contact lenses (SRGPcl). It has been hypothesised that the use of SRGPcl in the management of ectatic corneal disorders should be expanded and SRGPcl may even considered as the first option. The present research investigates this hypothesis. Purpose. To compare the performance of CRGPcl versus SRGPcl in participants with keratoconus, who are successfully wearing “habitual” CRGPcl. Methods. RCT) with a 2x2 crossover, 34 participants were recruited. The outcome measures were: Early Treatment Diabetic Retinopathy (ETDRS) log of minimum angle of resolution (logMAR) best corrected visual acuity (BCVA); VectorVision 1000E contrast sensitivity function (CSF), expressed in both numeric and log contrast sensitivity (logCS); National Eye Institute Visual Function Questioannaire-25 (NEI-VFQ) to assess the visual Qol; and reported o a scale from 1–10, the Levit Subjective Vision Scores (LSVS) and the Levit Subjective Comfort Scores (LSCS). The final outcome was the selection of the preferred lens type at research completion. Results. The only measures, which exhibited statistically significant differences between the two lens types, rejecting H0, were the LSCS, which was significantly higher in SRGPcl (p=0.002). The LSCS whilst wearing the experimental CRGPcl, was significantly higher in participants who selected CRGPcl [N=16, (52%)] as their preferred lens for future use, compared to those who selected SRGPcl (p=0.009). All other outcomes supported H0. The Final lens choice: CRGPcl were preferred by 53% (n=16) and SRGPcl by 47% (n=14). Conclusion. The research population exhibited significantly better comfort in SRGPcl compared with CRGPcl. Significantly higher comfort in CRGPcl was found in those who preferred CRGPcl, than those who preferred SRGPcl. Furthermore, Successful CRGPcl wearers whose LSCS in CRGPcl is < 7 are likely to achieve better comfort / tolerance with SRGPcl. This research indicates that on average, successful CRGPcl wearers find SRGPcl more comfortable and there should be no visual and visual Qol advantage or disadvantage in refitting successful keratoconic CRGPcl wearers with SRGPcl and vice versa.

Visual acuity and contrast sensitivity date with multifocal contact lenses

An Analysis of Anterior Scleral Shape and its Role in the Design and Fitting of Scleral Contact Lenses Purpose In the past 15 years the demand for Scleral Contact Lenses has grown exponentially. Yet the shape of the anterior sclera has not been fully described by sagittal height and transition angles in the four cardinal and the four oblique segments individually. Materials and Methods In the study 78 normal eyes, void of any pathological changes, of 39 subjects (mean age 25.4 ±2.0 yrs.) were investigated. The sagittal height, corneoscleral angle and scleral angle were measured individually in all eight segments of the anterior eye at three chord lengths 10mm, 12.8mm and 15mm by utilizing the Visante OCT. A Medmont E300 topographer was used to quantity the corneal power and the Grand Seiko WAM-5500 to show the objective refraction. Results Significant differences were found in comparison of horizontal and vertical corneal diameter (external and internal both p < 0.0001), and in all sagittal height and scleral angle measurements at a chord of 15mm in the opposite segments (sagittal height p ≤ 0.0021; scleral angle p ≤ 0.0105). At a chord of 12.8mm the shape of the anterior eye is symmetrical and becomes slightly irregular at a chord of 15mm. The nasal hemisphere showed a flatter scleral angle and a concave transition. In the temporal hemisphere scleral angles were steeper and a rather tangential or convex transition occurred.   Conclusion These findings are relevant factors to consider in the fitting and designing of Scleral and Soft Contact Lenses in the future. Further investigations of the scleral shape beyond 15mm are required. Keywords (Max. 6 Keywords) Anterior scleral shape, scleral contact lens, soft contact lenses, sagittal height, corneo-scleral profile, Visante OCT