Contact lens fitting in keratoconus
The treatment of keratoconus can be implemented by the use of spectacle lenses, contact lenses of various kinds, and surgery. In this article, we deal with the procedures of contact lens fitting in patients diagnosed with keratoconus. The different types of specific contact lenses and the methodology of fitting these contact lenses for keratoconus are described. To select a contact lens for the individual patient depends upon the severity of keratoconus and the amount of corneal ectasia. Pending these criteria, a contact lens is chosen, which will give the best visual acuity and tolerance. At present, many designs of special contact lenses exist in oxygen-permeable materials; in addition, other systems, such as piggy-back, SoftPerm, semi-scleral, and scleral contact lens types are used. Contact lens fitting on a conical cornea will smooth out the highly irregular optical surface of the cornea and improve visual acuity considerably. Contact lenses are one of the better solutions to correct refractive errors induced by pathology, and they should be prescribed as soon as the keratoconus is detected to avoid development of amblyopia. The quality and quantity of vision is far better than with spectacle lens correction.
Available from: Ahmet Altun
- "The quality and quantity of vision is far better than with spectacle lens correction . Success in the contact lens usage in the keratoconus patients may increase the visual acuity and vision related quality of life. "
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ABSTRACT: Purpose. The purpose of this study is to evaluate the vision related quality of life in patients with keratoconus by using the National Eye Institute Visual Function Questionnaire-25 (NEI-VFQ-25). Methods. Thirty patients presented with keratoconus (keratoconus group) and 30 healthy patients (control group) were included in this study. Twenty patients were using rigid gas permeable and 10 patients were not using contact lenses in keratoconus group. High and low contrast visual acuity and mean K values of the patients were recorded. Each subject completed the 25-item NEI-VFQ-25. Results. All subscales of NEI-VFQ-25 were lower in the keratoconus patients. The difference was more evident in the subscales of general vision, ocular pain, near vision, vision-specific mental health, vision-specific role difficulties, and peripheral vision . Overall composite score was 75.2 +/- 17.2 in the keratoconus group and 93.2 +/- 5.6 in the control group . Contact lens wearers had higher best corrected visual acuity in comparison with noncontact lens wearers . Patients with low visual acuity (logMAR > 0.4) in the better eye had lower distance vision, social functioning, mental health, and role difficulties. Meanwhile, patients with low visual acuity (logMAR > 0.4) in the worse eye had lower general health scores . Conclusions. Vision related quality of life was worse in keratoconus patients. Success in the contact lens usage and maintaining higher visual acuity may improve vision related quality of life.
Available from: Langis Michaud
- "One of the ways to address both issues is to consider the use of a soft lens fitted under the rigid one, so-called piggyback system (PBS) . Other alternatives include custom toric soft  or hybrid lenses  or large-diameter RGP lenses (mini-scleral or scleral) . "
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This study aims to report on the measured in vivo contribution of soft lenses of various powers to the optics of a piggyback system (PBS).
This prospective, non-dispensing clinical study was conducted on regular wearers of contact lenses who showed regular corneal profiles. Subjects were masked to the products used. The study involved the use of a spherical soft lens of three different powers in a PBS, used as a carrier for a rigid gas permeable lens. Baseline data were collected and soft lenses were then fitted on both eyes of each subject. Both lenses were assessed for position and movement. Over-refraction was obtained. Soft lens power contribution to the optics (SLPC) of a PBS system was estimated by computing initial ametropia, lacrymal lens, rigid lens powers and over-refraction. A set of data on one eye was kept, for each subject, for statistical analysis.
Thirty subjects (12 males, 18 females), aged 24.4 (±4.5) years, were enrolled. The use of plus powered soft lenses enhanced initial RGP lens centration. Once optimal fit was achieved, all lenses showed normal movement. SLPC represented 21.3% of the initial soft lens power when using a -6.00 carrier, and 20.6% for a +6.00. A +0.50 did not contribute to any power induced in the system. These results are generally in accordance with theoretical model developed in the past.
On average, except for the low-powered carrier, the use of a spherical soft lens provided 20.9% of its marked power. To achieve better results, the use of a plus-powered carrier is recommended.
Available from: Fateme Alipour
- "The optical features of soft and rigid contact lenses, including correction at the corneal plane and elimination of surface irregularities, offer advantages in corneal ectasia, thus contact lenses are the next step in treatment. As the cornea becomes more irregular and conical, difficulties in achieving satisfactory contact lens fit present  . "
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ABSTRACT: Prosthetic replacement of the ocular surface ecosystem (PROSE) uses custom designed and fabricated prosthetic devices in a treatment that restores vision, supports healing, reduces symptoms and improves quality of life in patients with complex corneal disease. We report the success rate for PROSE treatment of corneal ectasia.
Records of 59 patients with corneal ectasia seen in consultation over 6months were reviewed. Candidacy for treatment, topographic indices, change in visual acuity, achievement of satisfactory fit, device wear status and change in visual function at 6months were recorded.
Sixteen eyes were non-candidates because conventional correction was adequate. Trial devices were inserted but not dispensed for 13 eyes. No eyes were excluded for severity of ectasia. In the remaining 89 eyes, satisfactory fit was achieved and a device was dispensed. Twenty-one eyes (15 patients) had undergone penetrating keratoplasty. Device wear at 6months was documented in 78/89 eyes (88%). NEI VFQ-25 score improved 27.6 points (p<0.001) on a 100 point scale in patients wearing a device at 6months.
All candidate eyes with corneal ectasia could be fitted with a PROSE device. PROSE treatment has a high success rate when measured by ability to achieve satisfactory fit, impact on visual acuity and 6month data on both rate of continued wear and impact on visual function. PROSE treatment is an alternative to penetrating keratoplasty for patients with corneal ectasia who are contact lens intolerant.
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