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Rigid gas-permeable contact lenses for keratoconus in shaping the role of_2858

By Leo Harrison,2014-11-25 12:16
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Rigid gas-permeable contact lenses for keratoconus in shaping the role of_2858

    Rigid gas-permeable contact lenses for keratoconus in shaping the role of

     Abstract Objective: To evaluate the rigid gas permeable contact lenses (rigid gas permeable contact lens, RGPCL) wearing a long-term safety and shaping the role of the corneal

    shape. Methods: Patients with keratoconus matching candidates of high oxygen permeability RGPCL, respectively, to wear before and after wearing 12,18 months line keratometer and corneal topography examination, collection of central corneal

    astigmatism value, cone top K values, cone top eccentric distance, SRI, SAI and other parameters were statistically analyzed. Results: The mild group, the wearing of corneal astigmatism after RGPCL, cone top-K value, cone-top eccentric

    distance, SRI, SAI than to wear the former were significantly lower (P <0.05); moderate group, in addition to 12 months cone top eccentric distance, the value of corneal astigmatism than wearing no significant change before, the other parameters are also significantly lower at 18 months fell more obvious;

    severe group, 12 months In addition to the top cone was significantly reduced K , the other parameters not changed much, except at 18 months eccentric cone top no significant change in the distance, the other parameters significantly

    reduced. All the patients were not complications. Conclusion: The rigid contact lenses of high permeability, long-term wear

    is safe and certain forms of keratoconus shaping role, so as to achieve to reduce or control of keratoconus development.

     Key words keratoconus contact lens shaping the role of

     A Effect of rigid gas permeable contact lens on keratoconus

     [ABSTRACT] Objective: To evaluate the safety and the

orthokeratic effect of long term wearing of rigid gas

    permeable contact lens (RGPCL). Methods: A total of 366 eyes with keratoconus were subjected to wear proper RGPCL. Keratometer and corneal topography were used to determine the central cornea astigmatism, apex K value, apex decenteation distance, SRI and SAI before, 12 and 18 months after wearing

    RGPCL. Results: Of the slight keratoconus group: the above indexes significantly decreased (P <0.05). Of the moderate group: the above indexes, except for the apex decentration distance significantly decreased at 12 months and more

    evidently at 18 months. Of the severe group, the K value significantly decreased at 12 months and other figures remained unchanged. However, all the indexes significantly decreased except that the apex decentration distance remained unchanged at 18 months. No corneal complications were found. Conclusion: Long term wearing of RGPCL is safe and effect for keratoconus.

     [KEY WORDS] Keratoconus; Permeable contact lens; Orthokeratic effect Keratoconus is a non-progressive corneal

    inflammatory connective tissue disease, mainly for the purpose of partial corneal thinning and protrusion, leading to myopia, astigmatism has been increasing, corrected visual acuity gradually reduced, in the past mainly depend on corneal transplant treatment. In recent years, with rigid gas

    permeable contact lenses (RGPCL) of materials, design and processing technology for the continuous improvement of products are being further improved for keratoconus treatment and recovery of sight to provide a good means of non-surgical

    correction. The past six years, we tested a total of 191 cases of 366 patients with keratoconus and found that RGPCL in to get a good corrected visual acuity, delayed lesion development, the shaping of the cornea to a certain extent the role, these are as follows.

     1 Data and methods

     1.1 The clinical data 2001 2005 in Jinan City Central Hospital Laser Center tested 191 cases of patients with keratoconus RGPCL (366), 175 cases of patients with both eyes, monocular in 16 patients. 104 cases were male and female 87

    cases, 638 years old, mean (21.3 ? 8.4) years of age. With

    Xie Ying et al [1] standard, light (including suspicious) keratoconus 142, 193 moderate and severe 31. Corneal cone top

position: temporal inferior quadrant 208 (56.8%), nasal

    inferior quadrant 103 (28.1%), superior temporal quadrant 17 (4.6%), nasal quadrant 8 (2.2%), central corneal 10 (2.7%), not sure who the top cone 20 (5.5%). Form of corneal topography as follows: symmetrical bow tie-shaped 17 (4.6%),

    asymmetric bow tie-shaped 124 (33.9%), nipple-shaped 117

    (32.0%), round and oval-shaped 87 (23.8%), non - Rule-shaped

    21 (5.7%).

     1.2 Methods

     1.2.1 routine examination, including slit-lamp

    microscopy, intraocular pressure, fundus examination to exclude contraindications. Keratometer and corneal topography inspection.

     1.2.2 Matching the right RGPCL spherical design of 102, non-spherical design 237, keratoconus specially designed 27; parallel fitting 98, fitting 241 three-point contact, two-

    point contact fitting 27. Way to wear daily wear (each wearing RGPCL less than 12? H), flexible wear and continuous wear one week.

     1.2.3 Review to wear before and after wearing 12,18 months with routine examination, with appropriate checks, keratometer and corneal topography examination, collection of central corneal astigmatism value, K value of the top cone, cone top eccentric distance from the cornea surface regularity index (SRI), the corneal surface asymmetry index (SAI) and other data.

     1.3 Statistical analysis of data using SPSS12.0

    statistics, using paired t test analysis.

     2 Results

     This group of all keratoconus patients wearing rigid contact lenses of high permeability, the visual acuity markedly improved, preoperative visual acuity of 0.1 0.3, an

    average of 0.18 ? 0.11, after wearing glasses vision 0.6 1.2, with an average 0.79 ? 0.16. In addition to 12 cases of mild corneal epithelial erosion, the non-corneal complications,

    corneal epithelial erosion who points with epidermal growth factor eye drops after 2 4? D back to normal.

     2.1 mild keratoconus group before and after wearing the parameters in Table 1. Central corneal astigmatism value, K value of the top cone, cone top eccentric distance, SRI, SAI wear RGPCL after 12 months and 20 months were significantly

    lower, with statistical significance compared to the pre wear. Note: The wearing earlier, * for P <0.05, * Table 2 the parameters of moderate keratoconus group Note: The wearing earlier, * for P <0.05, ** for P <0.01 Table 3 with severe

    keratoconus Group parameters

     3 Discussion

     Keratoconus is an autosomal recessive congenital corneal abnormalities, the sick rate of 1 / 2000 [2], mostly occurs in young people, seriously affecting visual acuity, in serious cases lead to blindness. In recent years, with computer-aided

    inspection equipment such as corneal topography instrument popularity, more and more cases were diagnosed early [3]. Reposted elsewhere in the Download Center http:// free papers

     Permeability, rigid contact lenses used in keratoconus patients, their safety and efficacy has been widely recognized. With the RGPCL materials, design and processing of continuous improvement, RGPCL fitting method with the continuous improvement and even personality tests, has to

    become the preferred treatment of keratoconus [4,5]. Menicon Z RGPCL its high oxygen permeability rate (DK value: 163), non-

    spherical design, special design for keratoconus, improved peripheral arc, etc., not only the visual function of patients

    has been well restored, and the success rate of wear and comfort has been greatly improved, while reducing the incidence of complications. Fink et al [6] studied the high permeability of the microscope RGPCL corneal tear circulation and oxygen conditions, results show that the non-spherical

    design of the microscopic tear RGPCL exchange index was significantly higher than spherical design RGPCL, the degree of corneal hypoxia was significantly lower than spherical design of The RGPCL. This study followed up 191 patients, with

    the exception of severe herein, can wear or flexible continuous wear, daily wear can also ensure that those who wear the daily average of not less than 12? H.

     RGPCL ocular surface tear film can be an effective

    bridge, reshape the cornea anterior surface, forming a new optical system that allows the cornea to restore the optical interface for smooth, play tear lens effect, the use of tear mirror way of correcting irregular astigmatism, while significantly reducing the prism effect, thereby effectively

    improving visual acuity and contrast sensitivity, elimination of aberration and improve visual quality [7,8]. However, whether RGPCL like Ortho K CL play a shaping role in the

    same pairs of the cornea [9], using different designs and

    fitting way, take the initiative to shape the cornea of keratoconus favorable toward the direction of development? For this purpose, we undertook a review of patients with keratoconus research and analysis, results showed that mild to moderate keratoconus group of corneal topography shows that in wearing RGPCL 12 months, corneal shape that has undergone significant change in central corneal to reduce astigmatism, SRI, SAI and the cone from the top of eccentricity were significantly lower, indicating a good fitting of keratoconus

    RGPCL state can play a shaping role, to effectively improve the irregular nature of keratoconus, asymmetric nature of its rule-based and sphere-based, not only control the progress of keratoconus disease, but also to reduce the extent and

    patterns of disease improvement in 20 months time, this positive change has been strengthened. However, in severe keratoconus group, this change is only at 20 months has been reflected this mean that RGPCL shaping the role of keratoconus severity of time-dependent and differences? Severe keratoconus RGPCL use more special designs, and its myopic refraction larger, so that the thickness and RGPCL fitting state, the wearing of location is also different from the mild to moderate group, and this difference in shaping the process of

    corneal RGPCL The role needs to be further explored. How to take the initiative to master RGPCL the design process, making it right with appropriate state role in shaping the cornea towards the healthy development into a challenging task.

     RGPCL fitting of the main methods are: the parallel fitting method, the top filling method, the top compression method [10]. Parallel fitting method is more ideal as a fitting manner in keratoconus patients with difficult to achieve, in parallel with this group of cases are mild and fitness status of patients with suspected keratoconus. Three-

    point contact method and two-point contact method is the top

    of oppression or to optimize the evolution of the law, pure

the top of the oppression of law can not exist. Three-point

    contact method is that most patients with keratoconus wearing RGPCL in a relatively ideal [11], will be RGPCL the top of the pressure on the corneal scatter cone, both to reduce the top of the cone too much pressure, but also to make the location

    of RGPCL , stability, good condition, a serious keratoconus, the implementation of two-point contact method. France has

    increased due to the top of oppression or corneal scar corneal epithelial abrasion risk, the top filling method has been

    largely respected optical doctor, but this approach has increased corneal steepening, microscopic tears poor circulation and easy to appear monocular diplopia, glare and other defects. Top oppression law is conducive to reshape the cornea of the role played by RGPCL similar to orthokeratology lens (Ortho K CL) mechanism, and control the development of keratoconus. We RGPCL fitting process, the full use of this principle, in order to minimize the risk of corneal complications, the application of materials with high oxygen

    permeability rate of peripheral arc adjusted to increase the frequency and reduce the referral time for continuous wear and so on, no serious complications.

     Early keratoconus in the past does not encourage wearing RGPCL, we found that the more early stage patients, RGPCL the shaping role of the more obvious, and many patients with corneal shape completely back to normal. Our principle is that early detection and wear, dynamic observation, as soon as there is progress in keratoconus disease, whether mild or

    suspected keratoconus, early wear appropriate RGPCL, so as to achieve better vision, control development purposes.

     References

     [1] ZK (#] Xie Ying, Cheng Ying. Liu Yueh-101 cases of

    contact lens correction of keratoconus and treatment [J]. Optometry Journal, 1999,1:195 198.

     [2] Binowitz YS. Keratoconus [J]. Surv Ophthalmol, 1998, 42:297 319.

     [3] Guire LJ, Boume WM. Corneal topography of early keratoconus [J]. Am J Ophthalmol, 1989, 108:107 112.

     [4] Riffiths M, Zahner K, Collins M, et al. Masking of irregular corneal topography with contact lenses [J]. CLAO J, 1998, 24:76 81.

     [5] Schirmbeck T, Paula JS, Martin LF, et al. Efficacy and low cost in keratoconus treatment with rigid gas permeable

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     [6] Fink BA, Mitchell GL, Raasch TW, et al. Enhancing RGP contact lens performance: comparing back surface options [J]. Optometry, 2002, 73 (10): 605 613.

     [7] XU Si-Yi, LU Fan. Wearing contact lens corneal

    sensitivity changes after the research [J]. International

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     [8] Xie Ying, Wang Dan, Yang Lina, et al. Permeability rigid contact lens correction of keratoconus visual quality assessment [J]. Chinese Journal of Ophthalmology 2005,41:1086

     1091.

     [9] Dorronsoro C, Barbero S, Lorente L, et al. On eye

    measurement of optical performance of rigid gas permeable contact lens bases on ocular and corneal aberrometry [J]. Optom Vis Sci, 2003, 80:115 125. reposted elsewhere in the

    paper for free download http://

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