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Visual rehabilitation in keratoconus patients is optimally achieved with multicurve lenses such as ROSE K2 CL as compared to spectacles, soft, mono-curve or bi-curve GP lenses.¹  Studies have also reflected the use of ROSE K2 lenses for the enhancement of binocular resolution and three-dimensional depth perception in keratoconic eyes as compared to spectacles.² Literature has shown that visual rehabilitation with RGP or multicurve contact lenses help in restoring vision and improving the quality of lives with better comfort and satisfaction in patients with keratoconus eyes.^3-5 The higher magnitude of irregular astigmatism is optimally corrected with these contact lens systems, thereby avoiding, or postponing the need for surgical intervention.⁶ CL fitting in post collagen crosslinked (C3R) keratoconic corneas is performed after stabilization of the corneal topography for an invariable contact lens fit in the long term.⁷

Lens fitting parameters protocol offered by the manufacturer needs to be modified according to the fitting characteristics and fluorescein pattern observed on a custom basis, in order to achieve a tailored fit.⁸ Post C3R corneas were included in order to avoid the probable risk of lens parameter change due to altered corneal topography if the corneal ectasia progresses.^9-10 Unlike the conventional RGP lenses, ROSE K2 lenses are multicurve, which are designed by utilizing computerized digital lathes that compensate the parameters such as base curve, diameter, power, center thickness and paracentral fitting curves whenever a change is made to the central or peripheral parameters of CL.¹ The aim for this adjustment is to maintain the optimum posterior lens touch (sagittal height) when a change in edge lift is required. 

The ROSE K2 lens applies very small changes to the curves on both the anterior and posterior surface which help in focusing the light within the pupil zone to a single point providing better sight with minimum aberrations.^11-13 The expected primary measure outcome was to analyze the modifications required in fitting parameters of ROSE K2 contact lenses in post collagen crosslinked keratoconic corneas to achieve optimal and successful fitting.

A retrospective observational study of all patients of keratoconus following collagen crosslinking treatment who were referred to the Low vision services – cornea, of our centre for contact lens fitting. This study was performed to analyze the fitting parameters of ROSE K2 contact lenses (CL). Institutional ethics clearance was obtained. 

Cases records of patients of post C3R treated keratoconic corneas on ROSE K2 contact lens wear between the period of March 2015 – April 2018 and on follow-up for a minimum of three months were included for analysis. All eyes had undergone CL fitting on documenting stable corneal topography after C3R treatment (Figure 1). Data of those patients of keratoconus using other contact lens systems, or those with other ocular morbidities was excluded. Data included demographic details (stage of keratoconus, time following collagen crosslinking treatment of ROSE K2 CL fitting, laterality, uncorrected visual acuity (UVCA), best corrected visual acuity (BCVA) with spectacles, BCVA with ROSE K2 CL, refraction details, details of ROSE K2 contact lens fitting parameters, duration of ROSE K2 contact lens wear, lens exchanges, post wear problems, Scheimpflug corneal topography (for corneal curvature of anterior surface – K1 & K2, K-max, average K, thinnest pachymetry). The ROSE K2 contact lens fitting parameters included ROSE K2 CL initial trial (base curve, overall diameter, edge fit) and prescribed CL fitting parameters and modifications (BC, lens diameter, edge lift, Asymmetrical Corneal Technology (ACT) and Toric Periphery (TP) designs), lens exchanges, time duration of daily wear, period of follow up, and post CL fitting problems.

As per manufacturer’s recommendations, the first trial lens was selected and inserted on the patient’s eye. After approximately 20 minutes, sodium fluorescein dye was instilled in the eye for contact lens fitting assessment. Static and dynamic fit of the lens were assessed. The Back Optic Zone Radius (BOZR) was evaluated for apical feather touch, if attained other CL fitting parameters were evaluated otherwise trial lens was changed. Depending on the central staining, the BOZR of the lens was flattened or steepened in 0.10 mm steps until an apical feather touch was obtained. Once the CL achieves feather touch, the overall diameter and edge fitting were assessed to ensure that the lens was well centered and has a proper lens movement and the lens facilitates tear exchange. Lens Diameter and Edge lift were empirically modified by observing trial lens and visual acuity with the trial contact lens was noted and CL was prescribed to the patient after over-refraction. 

Optimal fit was adjudged with that contact lens which achieved the following for lens parameters:

The available designs include ROSE K2, ROSE K2 Irregular Cornea (IC), ROSE K2 Nipple Cone (NC), ROSE K2 Post Graft (PG) and ROSE K2 XL (XtraLimbal) Mini Scleral (Table 1). All detailed ROSE K2 lens parameters available in trial inventory and for dispensing are mentioned in table 1 (a) (b).

All required details of contact lens fitting, and assessment were entered in to a predesigned proforma for analysis. All the parameters that were modified for the optimum ROSE K2 CL fit were also recorded and evaluated.

Case records of 92 eyes of 64 patients (mean age 22.12 ± 5.57 years, range 11 to 36 years) having keratoconic corneas who were fitted with ROSE K2 CL were analyzed. There were 50 male (mean age 21.52 ± 5.59 years) and 14 female (mean age 24.11 ± 5.95 years) patients. The mean age of the patients at the time of collagen crosslinking was 19.46 + 7.42 year (range 11 to 26 years). The time interval between collagen crosslinking and CL fitting was 24.08 ± 24.91 months; (range 2 to 110 months) (Figure 2). 

The characteristics of study eye patients is shown is table 2, the amount of astigmatism in the study subjects is represented in Figure 3(a) and history of contact lens use (type and drop-outs) is shown in Figure 3(b).

The mean follow-up time of our patients was 15.60 + 9.84 months (range 3 to 34 months). The mean logMAR UCVA, BCVA with spectacles and BCVA with ROSE-K2 CL of all study subjects is depicted in (Table 2). The visual outcomes are analyzed in accordance to the base curve of the eyes and stages of keratoconus (Table 4 and Figure 4).

The mean difference of K-mean and the K-max in the entire study group was 0.97 + 0.32 mm (range 0.13 to 1.98 mm), 0.99 ± 0.37 mm in stage I, 1.02 ± 0.34 mm in stage II, 0.94 ± 0.40 mm in stage III and 0.89 ± 0.22 mm in stage IV keratoconus eyes. The distribution of K-max, K-mean, the recommended BC and the prescribed BC in the study eyes is depicted in (Figure 5). 

The mean difference between the manufacturer’s recommended base curve and final prescribed base curve in eyes with K-mean < 6mm was 0.33 ± 0.34mm; (range 0.25 to 0.5 mm) (p=<0.001, one-sample t-test), 6 to 6.99 mm was 0.19 ± 0.17 mm; (range -0.6 to 0.6 mm) and for and = 7 mm 0.18 ± 0.16 mm (range -0.35 to 0.6 mm) as shown in table 5, figure 6a. The mean difference between the trial fit assessment and final prescribed overall diameter in eyes with K-mean < 6.0mm was 0.17 ± 0.11 mm; (range 0 to 0.6 mm), 6.0 to 6.99 mm was 0.19 ± 0.14 mm (range 0 to 0.5 mm) and = 7.0 mm was 0.16 ± 0.12 mm; (range -0.2 to 0.3 mm), table5, figure 6b. In analysis as per severity of the keratoconus, the mean change from manufacturer’s recommendation in CL fitting parameters were mentioned in (Table 5).

Overall Modification: Modifications in overall ROSE K2 CL fitting parameters as against the manufacturer’s recommendations were required in 21 eyes with mean K base curve of < 6mm, 58 eyes with mean K base curve of 6 to 6.99mm and 19 eyes with mean K base curve of = 7 mm.

ROSE K2 CL base curve modifications were required in 19 eyes, in ROSE K2 diameter in 16 eyes and edge lift modifications in 18 eyes of those keratoconic eyes with mean K < 6mm; ROSE K2 CL base curve modifications were required in 53 eyes, in ROSE K2 diameter in 53 eyes and edge lift modifications in 37 eyes of those keratoconic eyes with mean K 6- 6.99mm; ROSE K2 CL base curve modifications were required in 18 eyes, in ROSE K2 diameter in 13 eyes and edge lift modifications in 10 eyes of those keratoconic eyes with mean K = 7.0 mm; (Table 6). ACT and TP were prescribed in 20 eyes (one eye in Kmean < 6 mm, 16 eyes in 6 – 6.99 mm, three eyes >7 mm) and 5 eyes (one eye in Kmean > 6 mm, three eyes in 6 – 6.99 mm, two eyes > 7 mm) respectively which ensured a better and comfortable lens fit.

This study describes clinical evaluation of ROSE K lens fitting for the visual rehabilitation of post C3R keratoconic corneas. The ROSE K2 CL for keratoconus is a proprietary design. It is a multi-spherical posterior design with aberration control aspheric optics across the front and back optic zone diameters. The ROSE K2 contact lens design being effective in providing good comfort, better quality of vision with less chair time for fitting has been described to have a greater acceptability in the management of corneal ectasias.¹² As per the earlier study, first definite apical clearance lens (FDACL) was chosen as a starting point in oval and nipple cones and the result showed that an average of 2.3 trial ROSE K2 lenses were required to achieve an optimal lens fit. Study also mentioned that eye care practitioners should anticipate higher optimal lens fit rates when using three-point-touch (83%) in comparison with apical touch contact lens fittings (71%).¹⁴  Another study reflected that two to four diagnostic trial lenses were required to determine the best fitted base curve for a desired three-point touch fitting on a keratoconic eye 2 ). An Indian retrospective study reported that a mean of 1.73 ± 0.9 (range 1-5) ROSE K trial lenses were required to lens base curve parameters to achieve desired fit.¹

This retrospective study describes the results of our experience of ROSE K2 CL fitting in post collagen crosslinked keratoconic corneas. The standard manufacturer’s recommendations may require modifications in several cases of advanced keratoconus depending on the severity or the stage of the corneal ectasia being dealt with. In several instances, custom modifications need to be adopted upon observing the static and dynamic fluorescein fitting characteristics in order to achieve an optimal contact lens fit. All our patients were referred for CL fitting after a minimum period of three months of collagen crosslinking treatment the trend observed in stabilization of collagen crosslinking treated corneas was immediate worsening between baseline and 1 month, resolution at approximately 3 months, and improvement thereafter.¹⁵ The relatively varying interval between the time of collagen crosslinking and contact lens fitting is due to the late reporting of patients (in accordance to their convenience for reporting), as most of our patients were referred and come to our clinics from areas located far away from our centre. Analysis of our contact lens fitting experience in 105 post collagen-crosslinked keratoconic corneas in this study observed that the optimal contact lens fit concurred well with manufacturer’s recommendations in eyes with where the mean K values ranged between 6.0 to 6.99 mm (56.25 to 48.12 D) and mean K = 7mm (=48.21 D).

The mean difference between the recommended and final prescribed CL base curve in cases of Kmean < 6.00 mm was found to be statistically significant. In Kmean <6.0mm, 95% of study eyes required modification in lens base curve, 80% in lens diameter and 90% of eyes required modification in edge lift as compared to those study eyes in group 2 and 3 (Table 7).

The Box and Whiskers plots (figure 4) clearly demonstrate that recommended BC and prescribed BC are in alignment with each other in group 2 of Kmean 6 - 6.99mm and group 3 of Kmean = 7.0mm whereas prescribed BC in group 1 of Kmean < 6.0mm shows deviation with preponderance towards steeper side.

A greater deviation from the recommended BC is noted in eyes with advanced ectasia (of Kmean < 6.0mm). The recommended base curve of contact lens in group 1 was noted to be slightly flatter than the mean K, concurring with the manufacturer guidelines i.e., 0.3 mm flatter than the Kmean, but prescribed CL BC is even steeper than mean K, shifting towards K-max Figure 5(a). In eyes with advanced keratoconus (stage IV), the deviation of K-mean from K-max is (0.89 ± 0.22 mm). Analysis of the overall diameter and lens edge modifications noted that the mean difference between these fitting parameters of Kmean <6.00mm group corelated with study eyes of KC stage IV, Kmean 6 to 6.99mm aligned well with study eyes KC stage II and III and Kmean =7.00 mm was in proportionate to the modification of KC stage 1 as depicted in (Figure 5). This highlights that the steeper radii of curvature of advanced keratoconic corneas necessitated modifications in the base curve fitting parameters as compared to recommended guidelines, leading to more amount of change in lens diameter and edge lift.

As the available steepest base curve option with the trial lens set of ROSE K2 lens is 5.0 mm, in those corneas where the trial CL was assessed to have less than desirable fit parameters, we proceeded with adopting modifications in the final prescription, based on the fitting observations in our experience. Achieving an optimal base curve fitting is paramount in being able to fit these irregular corneal contours and influences the overall diameter requirements and edge lift modifications. ROSE K2 multicurve lenses do provide a custom fit to mask the irregularities where the modification in one parameter is independent of the other and allows a wide range of modifications to facilitate the desired modification in lens diameter and edge lift.

Asymmetric Corneal Technology (ACT) and Toric Periphery (TP) incorporations in the final lens fit prescriptions were prescribed in 20 study eyes (1, e in Kmean group <6mm, 16 in 6 to 6.99mm, 3 in =7mm) and 5 study eyes (1 in Kmean group <6mm, 3 in 6 to 6.99mm, and 1 in =7mm) for better and stabilized lens fit. Our protocol recommendation that was followed in prescribing ACT incorporation in the final lens fit prescription is in those cases where an edge stand-off was noted with heavy pool at inferior lens quadrant. The amount of ACT prescribed depended directly on the quantity of edge lift at 6 O’clock. TP incorporation in the final lens fit prescription was in those cases where toric periphery was asymmetrical. This served appropriately for all our patients with all accepting their final prescribed contact lens well. None of our patients required any CL exchange.

The number of modifications, i.e., whether only one of the three (base curve, overall diameter, edge lift) or more was required was also analyzed and it was observed that 3, 15, 8 eyes required one parameter modification, 11, 21, 10 eyes required two parameters modification and 12, 15, 3 eyes require three or more parameters modification in cornea with Kmean <6mm, Kmean 6 to 6.99mm, Kmean =7mm respectively. Corneas with advanced keratoconus with base curve < 6.0 mm seem to require more modifications in terms of adjustments required for optimal base curve fit, overall diameter and edge lift fitting.  

Our experience can serve to guide ophthalmologist and optometrist dealing with contact lens fitting about the optimal modifications which can affect better customization of multicurve contact lens fits achieved based on base curve parameters. It is imperative for health care personnel dealing with contact lens fitting to understand the corneal topography of each cornea that is being dealt with in order to plan an optimal fitting that would minimize chair time and patient discomfort during the fitting trials. Patients with advanced corneal ectasia present with significant low and distorted vision as vision correction with spectacles and conventional rigid gas permeable contact lenses is not successful. Visual rehabilitation is best achieved in these eyes with the use of multicurve and cornea-scleral /scleral contact lens. These patients tend to over wear their contact lenses for long periods of time during the day due to the better quality of vision afforded by these and hence get dependent on these contact lenses. Comprehension of the optimal fitting parameter changes required to achieve ideal contact fits will result in enhancing the comfort of contact lens wear and alleviate the need for to look for options of corneo-scleral / scleral lens in these scenarios.