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The Official Scientific Journal of Delhi Ophthalmological Society
Customized Toric Soft Contact Lens in the Management of Advanced Keratoconus
Haile Woretaw Alemu1, Preetam Kumar2
1Optometry Department, University of Gondar, Gondar, Ethiopia
2L.V. Prasad Eye Institute, Kallam Anji Reddy Campus, Hyderabad, India
Corresponding Author:
Haile Woretaw Alemu 
B Opt, MSc, FLVPEI
Senior Optometrist, Lecturer of Contact Lens
University of Gondar, Optometry Department 
PO Box 196
Gondar, Ethiopia
Email id: haileworetaw@gmail.com
Published Online: 01-NOV-2018
DOI: http://dx.doi.org/10.7869/djo.406
Abstract
A 33 year old medical doctor complained of bilateral gradual reduction of distant vision for the past 4 months. He was a known case of keratoconus and was referred to LV Prasad Eye Institute for further management. Following extensive examination, both eyes showed advanced keratoconus. With refraction, vision improved to 20/40 and 20/20 for the right and left eye respectively. Rigid gas permeable contact lenses trials were performed but were unsatisfactory. Then, customized hydrogel toric soft contact lens trials were done which improved the right eye vision to 20/25 and left eye to 20/20. Custom made hydrogel toric soft contact lens improved vision secondary to advanced keratoconus.
Keywords : Keratoconus, Toric contact lens, Rigid Gas Permeable contact lens, Kerasoft
Introduction
Refractive errors secondary to keratoconus can be corrected using spectacles, contact lenses, intra-corneal ring segment implantation and corneal transplantation. Correction modalities depend on visual morbidity, progressive nature and stage of keratoconus.1,2,3 Various contact lens correction modalities offer satisfactory visual rehabilitation through masking the anterior corneal surface irregularities, thus, considered as the mainstay of optical correction.2,4,5 Spherical soft contact lenses, toric soft contact lenses, or customized toric soft contact lenses could be adequate for early stages of keratoconus. But as the condition progresses, rigid gas-permeable (RGP) contact lenses or various specialized contact lenses might be obligatory.3,4 This case discussion focused on indications of custom-made hydrogel toric soft contact lens in the management of advanced keratoconus.

Case 
A 33 year old medical doctor came to the Contact Lens clinic with chief complaints of gradual bilateral decreased vision for distance for the past 4 months. He had history of ophthalmic consultation locally and was diagnosed keratoconus in both the eyes. As a result, he came for further opinion and better treatment. In both the eyes, slit lamp examination revealed narrow palpebral fissure height with tight lid tonicity, corneal findings showed Fleischer ring inferiorly with prominent corneal nerves and ectasia, pupillary findings were round, reactive and symmetrical in both the eyes, presence of a clear crystalline lens and transparent media. Other anterior and posterior segment structures were within normal limits.
Status of ocular condition, modes of correction and likely visual prognosis was explained to the patient who opted for contact lens trial. Hence tri-curve RGP contact lens (purecon) trials were performed in both eyes. Trial fitting was started using parameterbase curve (BC) 6.35 mm, power (P) -10.00 diopters (Ds) and diameter (Dia) 9.20 mm (BC/P/Dia) for the right eye and 6.60/-5.00/9.20 mm for the left eye. Lens fitting characteristics was flat fit in each eye. Furthermore, four lens trials for the right eye and two lens trials for the left eye were conducted. Finally, lens parameter 6.25/-10.50/8.90 mm for the right eye and 6.20/-5.00/8.90 mm for the left eye were chosen based on preceding lenses fitting feedback. The right eye lens fitting was unstable with a thin edge clearance on horizontal periphery with central pooling and unstable during post blink assessment. The left eye fitting was stable but with thin edge clearance on horizontal periphery with central pooling. After 45 minutes of adaptation, the patient reported discomfort. Further Rose K2 standard RGP contact lens trials were performed for both the eyes, but fitting characteristics were unsatisfactory. Hence lathe cut custom-made Kerasoft IC hydrogel toric soft contact lenses (SCL) trial were advised and subsequently dispensed to the patient. Lens fitting characteristics were according to MoRoCCo-VA guidelines in each eye.



Discussion 
Optical correction with contact lens creates a homogeneous smooth anterior optical surface aiming to minimize an optical aberration and to improve visual acuity.4,6 Even though SCLs are known for their comfort, RGP contact lens provide maximum quality of vision compared to any other modality for moderate and advanced stage of keratoconus.4,5
Based on Allegro Oculyzer topography report, both the eyes had an oval shape cone with symmetric bowtie shape involving 7 mm zone in the right eye (Figure 1) and inferior asymmetric bowtie involving 7 mm zone in the left eye (Figure 2). According to Buxton et al classification of keratoconus8, both the eyes were diagnosed as advanced stage of keratoconus. Options of RGP contact lens or custom made toric SCLs were given to the patient. Trial lenses base curve were selected using Oculyzer Best Fit Sphere (BFS) values and average-K readings, while the diameter was based on cone size.7 In addition to lens design and adaptation habit; factors such as eye lid characteristics, stage of keratoconus, cone location and cone size largely influence the contact lens type and parameter selection.4



Neophyte contact lens users likely tolerate RGP contact lenses faster than experienced SCL users.4 Accordingly, initial trials were performed using tri-curve RGP (Purecon, New Delhi, India) contact lenses. The right eye lens parameters were 6.35/-10.0/9.20 mm but fitting suggested central touch, thick edge clearance and edge lift inferiorly with poor stability. Attributing factors were narrow palpebral fissure size, tight lid tonicity and large cone size. Whereas the left eye lens parameters were 6.60/-5.00/9.20 mm, Lens fitting revealed central pooling, adequate edge clearance and good stability in all gazes. Further, four more trials were performed aiming to improve the right eye lens fitting. The final lens parameters were 5.90/-10.0/8.70 mm. The lens diameter was reduced to minimize edge lift and to improve fitting stability. However, it was ill fitted and remained uncomfortable. In addition to the degree of keratoconus and eye lids characteristics, limitations of purecon RGP tri-curve aspheric design with 3F peripheral curve could contribute to poor lens fitting. Unlike limitations observed on Purecon RGP contact lenses, Rose K2 lenses (Boston XO material from David Thomas) has multi curve aspheric design, flexible edge lift system, wide range of parameters, comfortable lens material and a likely fit on diverse corneal shapes. Hence, trial was performed using lens parameter 6.0/-10.0/8.70 mm, but overall, the fitting was not different from prior tri-curve contact lens designs.
According to Fernández et al9, custom-made hydrogel toric soft contact lenses (Kerasoft IC) and corneal RGP contact lenses have a comparable advantage like low rate of complications, comfortable visual acuity and adequate wearing time. Moreover, Kerasoft IC contact lenses are less dependent on lid tonicity, palpebral fissure size and blink pattern.6 Hence it can be considered as an alternative option for managing keratoconus.9,10 Kerasoft IC lenses have single laser mark at 6 O'clock position and can incorporate spherical power up to ±30.0 Ds, cylinder up to 16.0 Dc, axis 1-degree steps, front surface aspheric/aspheric toric design, base curve ranges from 7.40 mm to 9.40 mm in 0.20 mm steps and diameter from 14.0 mm to 15.50 mm.
Based on the patient corneal topography information and Kerasoft IC fitting guideline, selected trial lens parameters were 7.80/0.0/14.50 mm for the right eye and 8.00/0.0/14.50 mm for the left eye. Following 45 minutes of adaptation time, both static and dynamic lens fittings were acceptable and over refraction was BVP -4.00Ds/-9.00Dcx 170 degree for the right eye and -1.00Ds/-4.50Dcx 170 degree for the left eye. The final lens fitting characteristics were deemed acceptable and in line with company fitting guidelines for both the eyes. Dynamic fitting revealed adequate post blink movement (estimated 1.5 mm), with no rotation, well centered and comfortable. The final right eye lens parameters were BC 7.80 mm, BVP -3.75Ds/-7.50DcX 160 degree and total diameter of 14.50 mm and improved VA to 20/25. The left eye contact lens parameter BC 8.00 mm/ BVP -1.00 Ds/-4.25Dcx 170 degree and total diameter 14.50 mm improved VA to 20/20. According to MoRoCCo-VA fitting guidelines, (post blink movement range from 1-2 mm, zero lens rotation, well centered, comfortable to the eyes and stable visual acuity), final lens fittings were unconditionally satisfactory. Finally, lenses were dispensed with recommendation of 10 hours maximum wearing time per day along with careful lens care instructions and regular follow-up advice.
In conclusion, custom made hydrogel toric soft contact lenses provided an optimum visual acuity and better comfort for the eyes with advanced keratoconus. Moreover, it can be considered as the best option for keratoconic patients having RGP contact lens intolerance.

Reference 
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Haile Woretaw Alemu, Preetam KumarCustomized Toric Soft Contact Lens in the Management of Advanced Keratoconus.DJO 2018;29:73-75
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Haile Woretaw Alemu, Preetam KumarCustomized Toric Soft Contact Lens in the Management of Advanced Keratoconus.DJO [serial online] 2018[cited 2018 Dec 13];29:73-75. Available from: http://www.djo.org.in/articles/29/2/Customized-Toric-Soft-Contact-Lens-in-the-Management-of-Advanced-Keratoconus.html
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