Clinical Trial: Scleral Versus Corneal RGP Contact Lenses in Irregular Cornea Disorders

Study Status: Enrolling by invitation
Recruit Status: Enrolling by invitation
Study Type: Interventional

Official Title: A Randomised Controlled Research to Asses the Clinical Performance and Effect on Vision Related Quality of Life of Rigid Gas Permeable Scleral Versus Corneal Contact Lenses for Keratoconus and Other I

Brief Summary:

The most common causes for irregular cornea (IC) in hospital contact lens practice are Keratoconus (KC) and related cornea thinning disorders. These conditions cause mild to marked impairment of vision and cannot be effectively corrected by spectacles and soft contact lenses. The gold standard in the management of KC is Corneal Rigid Gas Permeable contact lenses (corneal lenses), which correct approximately 90% of the corneal irregularity.

Compared with a normal cornea, the cornea in KC is irregular and this results in a compromise to the fit of rigid corneal lenses. Specifically, they bear on the cornea and this, together with the vulnerability of the cornea in KC, are implicated in corneal scarring, and disease progression as well as a significantly reduced vision related quality of life (QoL) in KC compared with corneal lens wearers who have no KC.

In cases where the compromise fit of corneal lenses proves problematic, large diameter Scleral RGP contact lenses (scleral lenses) may be used as a problem solver. Unlike the smaller corneal lenses which bear on the cornea, the scleral lenses completely bridge over the cornea and bear on the sclera.

The aim of this research is to investigate the performance of scleral lenses in KC participants who habitually wear corneal lenses.

The research question: is there a measurable difference in the visual performance and visual quality of life in participants with Irregular cornea disorders like keratoconus and other related conditions, who habitually wear corneal lenses in comparison with scleral lenses.


Detailed Summary:

The cornea is the transparent, fixed focus lens at the front of the eye. The cornea's curvature should be regular for good vision. The most common causes of irregular cornea (IC) in hospital contact lens practice are Keratoconus (KC) and related cornea thinning disorders. These conditions cause mild to marked impairment of vision due to High Order optical Aberrations (HOA), which degrade the retinal image quality and cannot be effectively corrected by spectacles and soft contact lenses. The gold standard in the management of KC are Corneal Rigid Gas Permeable contact lenses (corneal lenses), which correct approximately 90% of the corneal irregularity.

The corneal lenses fit differently in patients with a normal cornea compared to KC where they bear on the cornea. This fitting characteristic and the vulnerability of the cornea in KC are implicated in corneal scarring and disease progression as well as a significantly reduced vision related quality of life (QoL) in KC compared with corneal lens wearers who have no KC.

In cases where corneal lenses are not well tolerated, cause corneal insult, reduced visual performance or poor physical fitting characteristic, the large diameter Scleral RGP contact lenses (scleral lenses) may be used as a problem solver. Unlike the smaller corneal lenses which bear on the cornea, the scleral lenses completely bridge over the cornea and bear on the sclera.

The aim of this research is to investigate the performance of scleral lenses in participants who habitually wear corneal lenses.

Methodology The proposed quantitative experimental methodology is a randomised controlled trial (RCT) with cross over. The experimental intervention is a scleral RGP contact lens fitted from a fitting set and manufac
Sponsor: London South Bank University

Current Primary Outcome: Monocular Best Corrected Visual Acuity (BCVA) [ Time Frame: Baseline and after 6 weeks of wear of each interventionhe lens wearing period ]

High contrast BCVA will be measured by the specially constructed crowded, Logarithmic Minimum Angle of Resolution (LogMAR), Early Treatment Diabetic Retinopathy Survey (ETDRS) letter charts. An average score of 3 different, randomly presented charts will be taken as the final acuity score. It will be performed utilising the CSV1000E, under the established recommended standardised testing conditions utilised in a multitude of research protocols.


Original Primary Outcome: Same as current

Current Secondary Outcome:

  • Contrast Sensitivity Function [ Time Frame: Baseline and after 6 weeks of wear of each interventionhe lens wearing period ]
    The Contrast Sensitivity Function (CSF) will be assessed at each of the four spatial frequencies 3, 6, 12 and 18 Cycles Per Degree (CPD) averaging the results from 2 different charts with sinusoidal grating patterns. This will be performed utilising the CSV1000E, under the established recommended standardised testing conditions utilised in a multitude of research protocols.
  • The National Eye Institute-Visual Function Questionnaire (NEI-VFQ) [ Time Frame: Baseline and after 6 weeks of wear of each interventionhe lens wearing period ]
    The National Eye Institute-Visual Function Questionnaire (NEI-VFQ) (Mangione 2000) is a vision-related quality of life instrument designed to assess patients' perception of visual function and quality of life. The measurements include general health, general vision, ocular pain, near and distance activities, driving, colour vision, and peripheral vision. There are four components of psychological well being, these are; social function, mental health, role difficulties, and dependency function. It has been used to characterize the quality of life for patients with uveitis, diabetic retinopathy, glaucoma, and age-related macular degeneration (Mangione, Lee et al. 2001)


Original Secondary Outcome: Same as current

Information By: London South Bank University

Dates:
Date Received: April 21, 2015
Date Started: October 2015
Date Completion: October 2017
Last Updated: September 7, 2016
Last Verified: September 2016