1. 17100 Contact lens fitting after corneal CXL
Varsha Rathi
Somasheila I Murthy
L V Prasad Eye Institute, Hyderabad, India
The authors have no financial interest to disclose

2. Introduction
Keratoconus is a bilateral progressive, asymmetric, non-inflammatory ectatic disorder of the cornea that results in high irregular astigmatism resulting in reduced vision
Management of keratoconus
Arrest progression with CXL
Improve vision with glasses, contact lenses and surgery
Effectiveness of CXL with the help of ultraviolet A and the photosensitizer riboflavin to arrest the progression of keratoconus and ‘freeze’ the cornea with resultant flattening of the central corneal curvature, improvement in the best-corrected visual acuity, reduction in sim k values is known

3. Introduction
Contact lenses especially rigid gas permeable (RGP) lenses can be considered in improving vision and the selections of RGP lens parameters is mainly dependent on the severity and morphology of the cone
Corneal topography helps in determining the severity and morphology
It is of interest to study how the contact lens fitting relationship changes after this procedure
Purpose: To evaluate the rigid contact lens fitting following CXL

4. Materials & Methods Retrospective observational study
Patients who underwent CXL and presented to contact lens clinic from January, 2008 to July, 2011 were reviewed
Comprehensive eye examination
Corneal topography with Orbscan IIz before and after CXL
Inclusion criteria - Patients who had pre and post CXL contact lens usage
Diagnostic Contact lens fitting method based on topography data
Trial continued till an acceptable dynamic and static fit achieved
Acceptable dynamic fit - well centered lens on cornea, exhibited post blink movement of 1.5 to 2.0 mm and stable in all directions of gaze movements
Acceptable static fit - a minimal central fluorescein clearance to minimal central bearing and edge clearance of 0.4 to 0.6 mm
Over CL refraction was done once the lens fit was found to be acceptable to finalize the contact lens power

5. Static fit This photograph shows central This photograph shows a
pooling of fluorescein with contact lens
after CXL in keratoconus patient
This photograph shows a
fluorescein pattern of 3 point touch after
CXL in keratoconus patient

6. Statistical analysis
Descriptive statistics was used to describe patient demographics and paired test was used to compare the pre and post collagen cross linking data on refraction, visual acuity and contact lens parameters. The statistical significance was kept at p<0.05

7. Results n= 34 eyes of 27 patients Male 23
Mean age 19.4 ± 4.3 years, range (range, years)
Diagnosis -
Keratoconus (n=32 eyes)
Pellucid marginal degeneration (PMCD=1 eye)
Post LASIK ectasia (n=1 eye)
One patient had keratoconus associated with vernal keratoconjuntivitis
Vogt’s striae (n= 19 eyes), Fleischer’s ring (n= 27 eyes), apical scar pre-operatively (n=7eyes)
Mean duration between the surgery and contact lens use =2.53 months (range: 1-5 months)
One third of the patients started wearing contact lens one month following the surgery

8. Pre and postpost-operative refraction, corneal topography and contact lens parameters
Variables Pre-operative Post-operative p value
Refraction_ sphere ± ±
Refraction_cyl ± ±
BSCVA ± ±
Sim K_max ± ±
Sim K_min ± ±
Contact lens
Base Curve ± ±
Power ± ±
Visual acuity with CL 0.07 ± ±
Average daily wear ± ±
Central fit
(3 point-touch vs
central pooling) n=(24, 10) n=(30, 4)
Best spectacle corrected visual acuity - BSCVA

9. Keratoconus – CL after CXL
Same lens Different lenses
continued
n=12 eyes n=20 eyes
Pre Post Pre Post
Sim k
51.63 ± ± ± ±5.05
55.85 ± ± ± ±4.31
Base curve ± ± ±0.35
Diameter ± ± ±0.47
visual acuity 0.09± ± ± ±0.07
3 point touch
Central pooling

10. Complications
Central corneal haze after CXL n= 31 eyes ( no significant difference in BCVA)
Post CXL CL intolerance n=1 eye
The central fitting has changed in 12 (35%) eyes. Among them change from central pooling to 3 point touch was seen in 9 eyes and from 3 point touch to central pooling was seen in 3 eyes (p=0.146)

11. Results and discussion
The change in the contact lens fit indicates the changes in the shape of the cone after CXL
Our study describes RGP contact lens fitting following CXL and results show that RGP contact lens can be fitted in these eyes immediately after the healing of the cornea
As evident from our study one could use patients own RGP contact lens or similar parameter lens in the absence of significant changes in the corneal topography
With higher Sim k values, the base curve of the lenses changed compared to when the patients continued using their own lenses