Clinical trial NCT03531047: Refractive Corneal Cross-linking for Progressive Keratoconus
Official title: A Prospective, Controlled Study of Refractive Corneal Cross-linking for Progressive Keratoconus
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Keratoconus
Keywords: progressive
cross-linking
customised
refractive
Lead sponsor: Moorfields Eye Hospital NHS Foundation Trust
Sponsor class: OTHER
First posted: 2018-05-21
Enrollment: 53
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: NA
Intervention model: SINGLE_GROUP
Primary purpose: TREATMENT

Brief summary: Young patients with keratoconus face two problems: disease progression and corneal shape irregularity. Both underlie the 20% rate of corneal transplantation in keratoconics required to maintain useful vision.

Corneal collagen cross-linking (CXL) is a now the gold-standard treatment to halt disease progression. The aim is to strengthen the cornea to prevent further shape deterioration. For patients whose quality of vision has already suffered, standard CXL can generally only prevent further deterioration, rather than improving vision. Refractive CXL, a new iteration of CXL in which a bespoke treatment pattern is applied to the cornea, aims to smooth out surface irregularities thereby improving vision.

This primary objective of this study is to compare the visual outcome in patients with progressive keratoconus treated with refractive CXL, as compared with historical controls treated with standard CXL.

Detailed description: Irregular astigmatism (irregular corneal shape leading to irregular focus) is a common cause of failure to achieve an adequate spectacle correction for many patients with corneal disease. For patients affected, rigid gas permeable contact lenses are the only means of visual rehabilitation. Not all patients tolerate rigid contact lens wear, and those that do are often uncomfortable and have a restricted wearing time.

Keratoconus, in which the corneal shape becomes progressively steeper and more irregular in the 2nd to 4th decades of life, is a common cause of irregular astigmatism. Disease progression in keratoconus can be stabilised with corneal collagen cross-linking (CXL), effective in 90% of cases. Pre-existing irregular astigmatism often remains after CXL, with many patients requiring rigid gas permeable contact lenses to regain good vision.

The investigators have recently demonstrated improvements in vision following simultaneous combined cross-linking with laser refractive surgery (TransPRK/CXL). The excimer laser is used to create a smoother, more regular focusing shape on the cornea to improve the quality of vision achieved in spectacles. Although effective, the downsides of using this approach are both the cost and limited availability of excimer laser equipment in the National Health Service (NHS) in the United Kingdom. Also, excimer laser smoothing works by removing corneal tissue. It is not yet known whether this tissue removal will have any detrimental effect on corneal shape stability post CXL.

As a cheaper and potentially more widely accessible alternative, refractive CXL aims to regularise the corneal surface by applying a bespoke treatment pattern based on pre-operative corneal surface shape (topography) scans. At least two-thirds of patients undergoing standard CXL already have impaired vision at the time treatment. The investigators are aiming to offer these patients both long-term stability of their keratoconus and an improvement in vision in a single treatment.

Eligibility criteria: Inclusion Criteria:

* Patients with progressive stage I - III keratoconus
* Corrected distance visual acuity (CDVA) \< 0.00 logMAR

Exclusion Criteria:

* Patients under the age of 18 years
* Active ocular surface disease
* Minimum corneal thickness \< 375 µm
* Vulnerable groups
* Pregnancy

Primary outcomes:
measure: Change in corrected distance visual acuity
timeFrame: 24 months
Secondary outcomes:
measure: Change in uncorrected distance visual acuity
timeFrame: 24 months
measure: Manifest refraction
timeFrame: 24 months
measure: Tomography
timeFrame: 24 months
measure: Rates of keratitis
timeFrame: 24 months
Other outcomes:
Locations:
city: London
country: United Kingdom
facility: Moorfields Eye Hospital NHS Foundation Trust
Study officials:
affiliation: Moorfields Eye Hospital NHS Foundation Trust
name: Daniel M Gore
role: PRINCIPAL_INVESTIGATOR
References:
citation: Gore DM, Shortt AJ, Allan BD. New clinical pathways for keratoconus. Eye (Lond). 2013 Mar;27(3):329-39. doi: 10.1038/eye.2012.257. Epub 2012 Dec 21.
citation: O'Brart DP, Chan E, Samaras K, Patel P, Shah SP. A randomised, prospective study to investigate the efficacy of riboflavin/ultraviolet A (370 nm) corneal collagen cross-linkage to halt the progression of keratoconus. Br J Ophthalmol. 2011 Nov;95(11):1519-24. doi: 10.1136/bjo.2010.196493. Epub 2011 Feb 24.