scholarly journals The sag: A forgotten parameter in need of resurrection?

2016 ◽  
Vol 75 (1) ◽  
Author(s):  
Wayne D.H. Gillan
Keyword(s):  
Contact Lens ◽  
Contact Lenses ◽  
Empirical Studies ◽  
Large Diameter ◽  
Rigid Contact

The advent of large-diameter rigid contact lenses (semi-scleral lenses) has necessitated renewed understanding of the concept of ‘the sag’ of a contact lens and/or cornea. This article reviews the concept of ‘the sag’ and how to calculate the sag for spherical and aspherical surfaces. Reviews of empirical studies investigating the sag of the eye are presented. Data for normal and keratoconic corneas for sags as measured with an Oculus Keratograph are also included. How to include empirical measurements obtained in practice, in the determination of a first-trial semi-scleral lens, is suggested.

scholarly journals Preliminary Clinical Exploration of Scleral Lens Performance on Normal Eyes

2018 ◽  
Vol 2 (2) ◽  
pp. e14-e21
Author(s):  
Melissa Barnett ◽  
Jonathon Ross ◽  
Blythe Durbin-Johnson
Keyword(s):  
Visual Acuity ◽  
Contact Lens ◽  
Healthy Subjects ◽  
Contact Lenses ◽  
Front Surface ◽  
Contact Lens Wear ◽  
Factors Associated ◽  
Rigid Contact ◽  
Lens Wear ◽  
Spectacle Correction

Abstract Objectives: The purpose of this study was to evaluate the performance (i.e. vision, comfort and fit) of spherical and front-surface toric scleral lenses in subjects with regular, healthy corneas. Methods: Scleral lenses were fitin the eyes (n = 16) of healthy subjects (n = 9) with regular corneas, absent of pathology, and studied using an observational, multi-visit design. Lens fit was objectively evaluatedby an experienced practitioner.Following 1 month of successful lens wear, participants completedsubjective satisfaction surveys regarding the scleral lens wearing experience. Results:  According to participant surveys, scleral lenses were subjectively preferred over soft toric or gas permeable contact lenses in 88% of eyes, including in all eyes fit with a front-surface toric scleral lens (n = 3). Seventy-five percent (75%) of eyes achieved visual acuity of 0.1 logMAR or better, while all eyes with prior spectacle wear achieved visual acuity with a scleral lens within 1 Snellen line of spectacle correction. Seventy-five percent (75%) of eyes achieved good subjective comfort with a scleral lens. No participants reported poor subjective vision and/or comfort. Conclusions:  Our findings suggest that subjects preferred the performance of a scleral lens (spherical or front-surface toric) compared to a soft toric or gas permeable contact lens. Moreover, scleral lenses may provide a viable, alternative contact lens modality option for patients considering discontinuation of traditional soft toric and/or rigid contact lens wear; so long as the factors associated with hypoxia remain minimized. Key Words:  scleral lens; scleral contact lens; front-surface toric scleral lens; lens performance; normal eyes; healthy eyes

Nanophotonic Rigid Contact Lenses: Engineering and Characterization

2013 ◽  
Vol 633 ◽  
pp. 239-252
Author(s):  
Đuro Koruga ◽  
Dragomir Stamenković ◽  
Ivan Djuricic ◽  
Ivana Mileusnic ◽  
Jovana Šakota ◽  
...  
Keyword(s):  
Contact Lens ◽  
Materials Science ◽  
Contact Lenses ◽  
Base Material ◽  
Material Structure ◽  
Exclusion Zone ◽  
Characterization Methods ◽  
Rigid Contact ◽  
Complex Engineering

Contact lenses are a common optical aid to provide help with refractive anomalies of the human eye. Construction of contact lenses is a complex engineering task as it requires knowledge of optics, materials science, production and characterization methods for product quality. Besides correcting refractive anomalies, by using contact lenses it is possible to change the characteristics of light through the manipulation of material structure properties. Nanomaterials, such as fullerene C60, are candidates for the medium that interacts with light, thus changing its properties. During material syntheses for contact lenses, fullerenes are added to the base material and optical characteristics of the new nanophotonic material are compared with the base material. The engineering, manufacture and characterization of both a commercial and a new nanophotonic contact lens is presented in this paper. The interaction of water with both base and nanophotonic contact lens materials is described. Using experimental techniques, the phenomena of an exclusion zone (EZ) is also identified.

scholarly journals Anterior Eye Profilometry-guided Scleral Contact Lens Fitting in Keratoconus

2017 ◽  
Vol 6 (2) ◽  
pp. 97-100
Author(s):  
Roberto Soto-Negro
Keyword(s):  
Contact Lens ◽  
Potential Benefit ◽  
Contact Lenses ◽  
Spherical Model ◽  
Future Studies ◽  
Rigid Contact ◽  
The Stability ◽  
Fitting In ◽  
Contact Lens Fitting

ABSTRACT We report the case of a 35-year-old woman diagnosed with keratoconus since she was 18 years old and wearer of corneal rigid contact lenses (CLs). We refitted the case with the fully scleral CL ICD16.5 (Paragon Vision Sciences) for obtaining not only a successful visual restoration, but also a comfortable wear. We initiated the fitting with the spherical model of the CL, but it failed due to instability of the lens. We confirmed the presence of a clear asymmetry in the anterior scleral geometry in both eyes by using the profilometer eye surface profiler (ESP, Eaglet Eye), with a difference between nasal and temporal sagittal heights of 470 and 170 μm in right and left eyes respectively. Although this profile suggested the need for the fitting of a CL with significant peripheral toricity, we followed the manufacturer's guidelines and performed a trial with a CL of moderate peripheral toricity (125 μm of difference between steep and flat meridian). The stability of the CL failed again and finally a CL with a peripheral toricity close to that measured with the profilometer was fitted. With this lens, good visual performance, lens stability, and comfort was obtained and maintained during a 1-year follow-up. This case suggests that fully scleral CLs fitting might be optimized with the use of corneo-scleral profilometers, minimizing potentially the number of trials. This potential benefit should be investigated further in future studies. How to cite this article Piñero DP, Soto-Negro R. Anterior Eye Profilometry-guided Scleral Contact Lens Fitting in Keratoconus. Int J Kerat Ect Cor Dis 2017;6(2):97-100.

scholarly journals Clinical characteristics of keratoconus patients at the University of KwaZulu-Natal eye clinic

2020 ◽  
Vol 79 (1) ◽  
Author(s):  
Shishka Rupnarain ◽  
Nomvelo Madlala ◽  
Ntokozo Memela ◽  
Simpiwe Ngcobo ◽  
Nonkazimulo Shabalala ◽  
...  
Keyword(s):  
Contact Lens ◽  
Clinical Characteristics ◽  
Contact Lenses ◽  
Corneal Ectasia ◽  
Kwazulu Natal ◽  
Rigid Contact ◽  
The Mean ◽  
The University ◽  
Severe Grade ◽  
Eye Clinic

Background: Patients with keratoconus, which is a common corneal ectasia, often present to specialised clinics for management. Understanding the clinical characteristics of keratoconus patients can help improve knowledge of the presentation and management of this corneal ectasia and predict the needs of the clinic providing care for affected individuals.Aim: To describe the clinical characteristics of keratoconus patients attending the University of KwaZulu-Natal (UKZN) eye clinic.Setting: University of KwaZulu-Natal eye clinic.Methods: The study used a retrospective research design by reviewing the clinical record cards of patients attending the UKZN contact lens eye clinic over a 4-year period (January 2014 to December 2017). Data related to age, clinical characteristics and method of management of the keratoconus patients were extracted and analysed using descriptive statistics.Results: Just less than one-quarter of all patients (n = 1210) attending the UKZN contact lens eye clinic had keratoconus that was most often bilateral. The mean age at presentation was 25.2 ± 9.6 years with 74% of the sample being younger than 30 years. More than 90% (n = 419) of the sample reported refractive reasons as the primary reason for presenting to the clinic. The majority of the sample had severe keratoconus (n = 257) and rigid contact lenses were most commonly used for management of keratoconus patients.Conclusion: Keratoconus presents at an early age with a more severe grade and it is most commonly managed using rigid contact lenses. These findings should be considered for keratoconus screening, diagnosis and treatment programmes in KwaZulu-Natal.

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