Scientific Area - Accademia Italiana di Ortocheratologia

>Bibliografia-Atti

Articolo:Studio pilota sulla correzione ortocheratologica notturna nei bambini (COOKI) 2/2004
Titolo originale. The Children's Overnight Orthokeratology Investigation (COOKI) Pilot Study

Articolo:Studio clinico "Orthokeratology practice in children in a university clinic in Hong Kong"

Atti Convegno: Sicurezza, Efficacia dell’Ortho-K. Sei anni di Follow-up; Carlo LOVISOLO MD. Giornate di aggiornamento in ortocheratologia AIOK - Ottobre 2008 Imola.

Articolo: Slowing Myopia Progression with Lenses - Luglio 2007

Articolo: European Ortho K Symposium, report: Ortho K: Exciting new tomorrow, or death throes of an old idea? - Dicembre 2006

Articolo: Orthokeratology: An Update - Dicembre 2005

Articolo: Reduction of Myopia From Corneal Refractive Therapy - Giugno 2005

Articolo: Is fluorescein pattern analysis a valid method of assessing the accuracy of reverse geometry lenses for orthokeratology? - Gennaio 2005

Articolo: Asymmetrical Increase in Axial Length in the Two Eyes of a Monocular Orthokeratology Patient - 2004

Articolo: The Myopia Epidemic. Is There a Role for Corneal Refractive Therapy? - 2004

Articolo: Comparison of Reverse-Geometry Lens Designs for Overnight Orthokeratology - 2003

Menicon y la Clínica Novovisión de Madrid colaboran en un estudio para elucidar si las lentes de ortoqueratología producen un control de la progresión de la miopía en niños. Giugno 2008
Madrid - Aunque estudios de investigación recientes parecen indicar que el uso de lentes de ortoqueratología en niños producen una ralentización de la progresión de la miopía frente a otros tipos de corrección visual como gafas o lentes de contacto, estos estudios han sufrido importantes problemas en su diseño y metodología. Con el objetivo de evaluar de una manera rigurosa y salvando los problemas de diseño y metodología de estudios anteriores, Menicon y la clínica Novovisión de Madrid están realizando un estudio, conocido como el MCOS (The Myopia Control with Orthokeratology contact lenses in Spain, según sus siglas en inglés), que pretende comparar el crecimiento axial del ojo entre niños de raza blanca usuarios de lentes de ortoqueratología (Orto-K) y gafas con corrección de visión lejana (GVL) durante un periodo de 2 años. Para este estudio, se han reclutado 62 niños de 6 a 12 años de edad con miopías entre -0,75 y -4,00D, y astigmatismos ≤ 1,00D a los que se les ha asignado aleatoriamente a usar lentes de Orto-K en modalidad nocturna o GVL. Se están realizando medidas de longitud axial (mediante interferometría coherente parcial, IOLMaster de Zeiss), longitud de la cámara anterior, topografía corneal, refracción cicloplégica y agudeza visual cada 6 meses. Hasta la fecha, ningún niño ha abandonado el estudio, no se ha detectado ninguna reacción adversa y no se han requerido modificaciones en las lentes adaptadas en el grupo de Orto-K. El estudio MCOS ofrece una serie de características únicas: diseño prospectivo; equilibrados grupos experimentales y medidas biométricas oculares de gran resolución que, conjuntamente, deben elucidar si el uso de lentes de ortoqueratología es un método efectivo de control de la miopía.

“Este estudio pretende confirmar, mediante el riguroso método científico y usando precisos instrumentos de medida, si el uso de lentes de ortoqueratología reduce la progresión de la miopía en niños. Este estudio es de especial relevancia debido a que la incidencia de la miopía en adolescentes ha aumentado sustancialmente a lo largo de las ultimas décadas alcanzado porcentajes del 20 al 50% en países occidentales y de hasta el 80% en algunos países del este asiático, considerándose en estos últimos la miopía como una epidemia”, comentó el Dr Jacinto Santodomingo, Director Global de Relaciones Profesionales de Menicon Co., Ltd.

“Llegamos varios años adaptando lentes de ortoqueratología en nuestra clínica, durante los cuales hemos observado que la miopía parece progresar menos en niños portadores de lentes de ortoqueratología frente a niños usuarios de otra modalidades de compensación óptica. Este estudio nos permitirá confirmar si nuestras observaciones preliminares son correctas”, añadió César Villa, Director de Optometría en la clínica Novovisión.

Mar 2008 Abstract: Long-Term Clinical Outcomes for Overnight Corneal Reshaping in Children and Adults. Marzo 2008
The researcher retrospectively evaluated outcomes of overnight corneal reshaping (OCR) in children aged 12 years or younger compared to children older than 12 years and adults at one practice to establish the efficacy and safety of OCR during a period of 51 months.
Examination records of OCR patients were reviewed for pretreatment data, including manifest refraction, keratometric readings, topography, corneal staining, and age at beginning OCR. Post treatment records were reviewed for manifest refraction, unaided visual acuity, keratometric readings, topography, corneal staining, adverse events, and duration of OCR lens wear.
Records of 296 OCR patients were evaluated. One hundred fifty-four (52.0%) patients were 12 years old or younger. Sixty-eight percent of all patients in the study were Asian, and almost 95% of the patients aged 12 years or younger were Asian. The patients aged 12 years or younger had a mean original spherical equivalent refractive error of -3.50 +/- 1.50 diopters (D).
The patients older than 12 years had a mean original spherical equivalent refractive error of -3.20 +/- 1.50 D. Refractive changes were similar between the group aged 12 years or younger and the group older than 12 years (3.30 +/- 1.40 D vs. 3.10 +/- 1.40 D) (P=0.14). The mean unaided, binocular logMAR visual acuity was 0.03 +/- 0.06 (i.e., 20/20) for the group aged 12 years or younger and 0.02 +/- 0.07 (i.e., 20/20) for the group older than 12 years.
There were three adverse events during the study that did not result in a loss of best-corrected visual acuity. A total of 507 patient-years of wear were represented in the study.
CONCLUSION: The author concluded that OCR resulted in comparable safety and efficacy in temporarily reducing myopia for children younger than 12 years as it is for children older than 12 years and adults.
Lipson MJ. Long-term clinical outcomes for overnight corneal reshaping in children and adults. Eye Contact Lens. 2008 Mar;34(2):94-9.

October 3, 2004 Abstract: Reducing Myopia with Ortho-k
A 13-year-old boy who had been receiving ortho-k treatment in his left eye only since 1999 participated in a retrospective study on the effects of ortho-k. Researchers presented the changes in the axial length, the unaided visual acuity and the refractive error during a two-year period. In 1999 (when the boy was 11), he was fitted with an ortho-k lens in his left eye. His refractive errors were OD -0.25 -0.75 x 168 and OS -2.50 -0.50 x 170 before beginning ortho-k wear. He made yearly visits in 2001, 2002 and 2003 to the researchers' clinic, where they assessed logMAR visual acuity, refraction, ocular health and axial length. In 2003, the boy's unaided visual acuity was OD 0.40 logMAR and OS -0.04 logMAR and the axial length in his left eye had increased slightly (0.13mm). The right eye experienced a significant increase in axial length (0.34mm) with a corresponding increase in spherical equivalent refractive error (0.75D). According to the researchers, this case suggests that ortho-k wear in the eye undergoing treatment may have slowed myopia progression in a boy undergoing unilateral ortho-k treatment.
Cheung SW, Cho P and Fan D. Asymmetrical Increase in Axial Length in the Two Eyes of a Monocular Orthokeratology Patient Optometry & Vision Science 2004 Sept;81(9):653-656.

Riassunto: Riduzione della miopia con Orto-K
Un ragazzo di 13 anni corretto con l'orto-K soltanto dal 1999 nel suo occhio sinistro ha partecipato ad uno studio retrospettivo sugli effetti dell'orto-K. I ricercatori hanno presentato i cambiamenti nella lunghezza assiale, nell'acuità visiva non corretta e nell'errore refrattivo durante il periodo biennale. Nel 1999 (quando il ragazzo era di undicenne), fu corretto con una lente per orto-k nel suo occhio sinistro (-2.50). Le sue correzioni erano OD sf -0.25 cil -0.75 x 168 ed OS sf -2.50 cil -0.50 x 170 prima di cominciare l'orto-K.

Ripetè i controlli annuali nel 2001, nel 2002 e nel 2003 nella clinica dei ricercatori, dove valutarono l'acuità visiva del logMAR, la rifrazione, la salute oculare e la lunghezza assiale. Nel 2003, l'acuità visiva di non corretta del ragazzo era logMAR del OD 0.40 ed il logMAR di OS -0.04 e la lunghezza assiale del suo occhio sinistro (quello miope di -2.50) era aumentata un po'(0.13mm). L'occhio destro ha avvertito un aumento significativo nella lunghezza assiale (0.34mm) con un aumento corrispondente nell'errore rifrangente dell'equivalente sferico (0.75D). Secondo i ricercatori, questo caso suggerisce che l'orto-K applicata all'occhio trattato, può ritardare la progressione miopica in un ragazzo corretto con l'orto-K unilaterale.
Cheung SW, Cho P. e Fan D.- Incremento asimmetrico della lunghezza assiale nei due occhi di un paziente corretto con Ortocheratologia unilaterale; Optometry & Vision Science - Settembre 2004; 81(9)653-656

January 4, 2004

Contact Lenses Today® is edited by Dr. Joseph T. Barr and the staff of Contact Lens Spectrum.
Abstract: Studiare archi pigmentati nell'ortocheratologia

I ricercatori hanno osservato archi pigmentati in due pazienti 23-year-old iniziare di una settimana, di sei settimane e di 28 settimane di uso. I soggetti hanno partecipato a uno studio di un anno e hanno quindi fermato uso di lente. Gli archi non erano più presenti dopo due mesi di sospensione lenti.

Cho P, Chui WS, Cheung SW. Reversibility of Corneal Pigmented Arc Associated with Orthokeratology. Optometry and Vision Science 2003;80(12):791-795.

December 28, 2003

Contact Lenses Today® is edited by Dr. Joseph T. Barr and the staff of Contact Lens Spectrum. This week CLToday® reaches nearly 10,000 readers in 74 countries.

Fitting Tip: Ortho-k Monovision Options
Orthokeratology on a presbyope presents us with options. We can mold both eyes for far or we can mold one eye for far and the other for near (monovision). With standard contact lens fits, if the patient selects monovision, then we traditionally choose the dominant eye as the distance eye. However, with orthokeratology, there have been times when I've had difficulty getting the dominant eye to acceptable distance visual acuity. Rather than risk this outcome, I now always begin my orthokeratology therapy with full-distance molding in both eyes. The patient will have to wear near correction for a while until I can determine which eye has the best and most consistent distance visual acuity. After I determine this, I refit the other eye with a steeper mold (decreasing molding) until I reach the desired near visual acuity. This technique has the added benefit of allowing the patient to experience both binocular vision and monovision.
--Steven R. Shum, OD
Germantown, Tennessee

September 2003

Digging Through the Literature
Use this review to catch up with the latest contact lens and nutrition news.
By Marjorie J. Rah, OD, PhD
http://www.clspectrum.com/archive_results.asp?article=12419&sub=1007

Clin Exp Optom. 2003 Sep

An assessment of consecutively presenting orthokeratology patients in a Hong Kong based private practice. Cho P, Cheung SW, Edwards MH, Fung J.

Centre for Myopia Research, Department of Optometry and Readiography, The Hong Kong Polytechnic University, Hong Kong SAR, China.

PURPOSE: The aim of this study was to collect objective, subjective and demographic data on consecutively presenting orthokeratology (ortho-k) patients who attended for routine follow-up examination in a Hong Kong based private practice in May 2001. METHOD: Sixty-nine patients who returned to the surveyed practice for follow-up visits during the study period (May 2001) were interviewed and relevant data extracted from their files. Data collected included identification and estimation of the extent of complications encountered by ortho-k patients and their satisfaction with the treatment. RESULTS: Among the 61 patients who had been wearing ortho-k lenses for at least one month, 50 patients were younger than 16 years old. Twelve children (24 per cent) had been reluctant to wear ortho-k lenses before undergoing the treatment but, after commencement of lens wear, only one child was not very willing to wear the ortho-k lenses. The mean pre-ortho-k spherical refractive error of these patients was -3.93 +/- 2.30 D (OS only). Of the 59 patients who wore ortho-k lenses for at least one month and who were on night therapy, 10 patients had to wear spectacles or contact lenses in the daytime due to significant residual myopia. There was no statistically significant correlation between post-ortho-k unaided visual acuity and pre-ortho-k refractive error (spherical, cylindrical or the equivalent sphere) in the 49 patients who did not need to wear any vision correction in the daytime. Of the 61 patients, four reported eye inflammation/infection during the treatment. All recovered their ocular health without any effect on their vision or corneal health. The incidence of corneal staining that required lens wear to be stopped appeared to increase with the duration of ortho-k lens treatment. The incidence of staining was not related to refractive error, unaided visual acuity or the age of the subjects. The most common problem reported by the patients was lens binding and there were also reports of increased redness, itching, light sensitivity and secretion of mucus in the morning after opening their eyes. More than 50 per cent of the patients experienced some distance vision blur, which was worse towards the end of the day. For most patients, these problems occurred only occasionally. Higher pre-ortho-k spherical refractive error was related to poor near and distance vision and worse distance vision towards the end of the day. CONCLUSION: The majority of the patients interviewed were children who reported being 'happy with the results of the treatment'. Night wear is the main wearing modality and in view of the increased risk of complications in overnight wear and the fact that a large number of the patients are children, the need for strict compliance with the practitioner's instructions for lens use and care cannot be overemphasised. With careful monitoring and good compliance, complications with overnight ortho-k wear can be minimised. In view of the high incidence of lens binding, it is essential that patients and parents of young patients know the correct method to free a bound lens.

August 2003

A Look at Ortho-k and Corneal Epithelium Health
This study investigates the use of single-fit lenses for ortho-k and how they effect the corneal epithelium.
By Ruiduan Liao, Juanjuan Feng, Yongcong Chen, Jingwen Wang and Wenhui Zhu
http://www.clspectrum.com/archive_results.asp?article=12401&iss=8/1/03

Eye Contact Lens. 2003 Jul

Unusual morphology in orthokeratology contact lens-related cornea ulcer. Wang JC, Lim L.

The Eye Institute at National University Hospital, Singapore.

PURPOSE: To report a case of unusual ulcer morphology in orthokeratology-related corneal ulcer. METHODS: A single observational case report of a 14-year-old Chinese female myope with a 1.5-month experience wearing overnight B.E. orthokeratology (Capricornia) lenses and presenting with a right stellate-shaped central cornea abscess. Cornea scrapings for Gram stains, culture, and antibiotic sensitivity were performed. The patient was prescribed hourly fortified cefazolin and gentamicin drops. RESULTS: Pseudomonas aeruginosa grew on blood and chocolate agar cultures. The ulcer was successfully treated with antibiotics and reepithelialized over 5 days. There was a residual central corneal scar. The refraction changed from -4.25 sphere OD and -1.75 -1.75 x160 OS to -3.50 -1.50 x160 OD and -1.50 -1.75 x165, giving a visual acuity of 20/ 25 OD and 20/20 OS. CONCLUSIONS: A flatter fit of orthokeratology lenses may be associated with unusual cornea ulcer morphology.

Zhonghua Yan Ke Za Zhi. 2003 Jun

[Topographical evaluation on decentration of orthokeratology lenses] [Article in Chinese] Yang X, Gong XM, Dai ZY, Wei L, Li SX.

Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China. yangxiao100@163.net

OBJECTIVE: To evaluate the degree and correlative factors of decentration of orthokeratology lenses and its effect on the visual function. METHODS: Two different kinds of orthokeratology lenses were fitted to 270 eyes of 135 patients [initial mean refractive error: (-3.98 +/- 1.51) D]. Humphery Instruments ATLAS 8.0 was used for the computer-assisted analysis of corneal differential topographical maps. The examination of corneal topography was proceeded on the patients before the fitting of orthokeratology lenses and 6-month later. The distance from center of optic zone to apex of the cornea was measured as the value of decentration of orthokeratology lenses. The factors influenced the value of decentration were analyzed, including the initial refraction error, astigmatism, keratometry values, corneal eccentricity, and the diameter of the lens. The complaints of patients were recorded. Questionnaires, involving the symptoms of monocular diplopia and glare, were used to evaluate the effects of decentration of orthokeratology lenses on the visual function. RESULTS: The mean distance of decentration was (0.49 +/- 0.34) mm after one night fitting, the mean distance of decentration after follow-up for 1 month, 3 months and 6 months was (0.57 +/- 0.41) mm, (0.55 +/- 0.48) mm and (0.59 +/- 0.39) mm, respectively. After one month, the distance of decentration was less than 0.5 mm in 51.1% eyes, 0.5 - 1.0 mm in 35.6% eyes and more than 1.0 mm in 13.3% eyes.The direction of decentration in eyes with more than 0.50 mm decentration was mainly in the temporal side (48.5%). Patients with greater initial astigmatism and smaller diameter of lens showed greater distance of decentration (P < 0.05). There was no statistically significant difference in the distance of decentration between two groups with different corneal eccentricities and keratometry values (P > 0.05). The distance of decentration was greater in patients with monocular diplopia and glare. CONCLUSIONS: The degree of decentration of orthokeratology depends on the degree of initial refractive error, astigmatism and the design of orthokeratology lenses. The degree of decentration can influence the visual function.

May 2003

Corneal Reshaping in Children
BY MARJORIE J. RAH, OD, PHD
http://www.clspectrum.com/archive_results.asp?article=12334&sub=1053

March 2003

Can Orthokeratology Correct Astigmatism?
BY JOHN MARK JACKSON, OD, MS, FAAO
http://www.clspectrum.com/archive_results.asp?article=12305&sub=1007

March 2003

Orthokeratology and Adolescent Myopia Control
This study set out to determine whether overnight wear of an orthokeratology lens would affect the progression of myopia in young people.
By Thomas R. Reim, OD, Max Lund, OD, and Richard Wu, OD
http://www.clspectrum.com/archive_results.asp?article=12316&sub=1007

January 2003

Iron Deposition Line In Ortho-k Patients
BY MARJORIE J. RAH, OD, PHD
http://www.clspectrum.com/archive_results.asp?article=12273&sub=1007

April 2002
Corneal Topography and Orthokeratology: Pre-fitting Evaluation
Corneal topography accurately analyzes the pre-fitting cornea of an orthokeratology patient.
By John Mountford, Dip. App. Sc, FAAO, FCLSA, Patrick J. Caroline, FCLSA, FAAO, and Don Noack, Dip Opt (WA)
http://www.clspectrum.com/archive_results.asp?article=12133&iss=4/1/02

June 2002
Corneal Topography And Orthokeratology: Post-fit Assessment
Corneal topography accurately diagnoses post-fitting problems of ortho-k patients.
By John Mountford, Dip App Sc, FAAO, FCLSA, and Don Noack, Dip Opt (WA)
http://www.clspectrum.com/archive_results.asp?article=12163&sub=1007

December 2002
Combining Two Methods of Correcting Myopia
With a thin cornea post-LASIK, a patient successfully wears reverse geometry lenses to correct residual myopia.
By S. Barry Eiden, OD, FAAO, and Amber Dawson, OD
http://www.clspectrum.com/archive_results.asp?article=12262&sub=1228

Khoo, Chong , Rajan, "A 3-year study on the effect of RGP contact lenses on myopic children", Singapore Med. J., 40(4), 1999: 230-237.

Horner, Soni, Salmon, Swartz, "Myopia progression in adolescent wearers of soft contact lenses and spectacles", Optom. Vis. Sci., 76, 1999:474-479.

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Paige, Mustaler, "Orthokeratology: A Retrospective Study", Contact Lens Spectrum, Sept. 1986: 24 -28.

Paige, "Myopia Control for the Younger Generation", Contact Lens Spectrum, Aug. 1986: 83.

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Perrigin, Perrigin, Quintero, Grosvenor, "Silicone-Acrylate Contact Lenses for Myopia Control: Three-Years Results", Optometry and Vision Science, 67, 1990: 764-769.

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Atti del convegno European Contact Lens Society of Ophtalmologists ECLSO 2003
18-21 Settembre 2003 – Venezia Italia

Abstract del congresso inerenti l’ortocheratologia.

Halons and ghost images during orthokeratology treatment: Problem Solving
Giuseppe Toffoli – Padua – Italy Riccardo Olent – Turin - Italy

ABSTRACT: Introduction. The improvement of the orthokeratology techniques, the aid of instruments for the control of the corneal shape and the use of software for the calculation and design of contact lenses have allowed the practioner to relate the geometric parameters of contact lenses with the corneal shape modification. Purpose.The aim of present study is to solve the problem of halons and ghost images perception during orthokeratology treatment in myopic subjects.Material and Methods. In four young adult subjects night wearing reverse-geometry rigid gas-permeable lenses (custum design fit), corneal topographic changes were monitored (15, 30 60, 90 days after start wearing) using the Optikon Scout corneal topographer. The treatment zone diameter, induced by thecontact lenses, was measured and compared with scotopic pupilaperture. Subjects reported in each topographic session if overnight they perceived halons and gosht images. In subjects in which this problem persisted after 60 days, the contact lenses were changed by enlarging the optic zone dimension. Results. All thesubjects perceived halons after 15 days of treatment. Only 2 subjects had the problem after 30 days and1 subject still after 60 days. This subject, after 30 days from the change of the contact lenses, solves the problem of halons.Conclusion. Although this work need more confirm, the corneal treatment zone dimension is proportional to contact lenses’s optical zone and the problem of halons and gosht image could be present if it’s smaller then scotopic pupill’s aperture.
Key Words: orthokeratology, corneal molding, halons, ghost image, optical zone.

MICROSTRUCTURAL CORNEAL CHANGES IN ORTHOKERA TOLOGY
Gudrun Bischoff Hamburg, Gennany
Orthokeratology is a method, which modifies the structure of the anterior corneal tissues. The older techniques and lens types darnaged and folded the stromal collagen-larnellae. The question was, if the new technique and lens design is less stress-inducing and if possible changes are restricted to the epithelial celllayer, as the advertisement makes us believe. The cellular structures were pictured by a confocal microscope. Investigated were OK-wearers of different contactological history and time of wearing OK-lenses. The result could not be covered under one headline. The spectrum of results carne from no measurable changes to massive microcysts. Referring to age of patient and type of earlier worn lenses the changes to be found were predictable. Typical distortion of the collagen-lamellae was not detected. So far the new method is more acceptable than the earlier type of OK-lenses, fitted 15 years ago

EMPIRICAL ADVANCED ORTHOKERATOLOGY THROUGH CORNEAL TOPOGRAPHY: THE UNIVERSITY OF HOUSTON CLINICAL STUDY
Sami El Hage, Nonnan Leach, William Miller, Katrina Parker, and Amber Gaume Eye Care Associates, Houston, Texas, U.S.A.
Introduction: There is increasing evidence that reverse geometry rigid gas permeable (RGP) contact lenses when woro at night will flatten central coroeal curvature resulting in improved unaided visual acuity in low to moderate myopes. Traditionally, these designs have characteristically required the use of diagnostic lenses to determine the best fit for a given wearer. Objective: The purpose of this study is to colIect scientific and cIinical data on twenty-five subjects and to determine the validity of fitting advanced accelerated orthokeratology lenses (CKR) empirically from coroeal topography without the use of diagnostic lenses. Method: Seventeen subjects, 18-37 years of age having naturally occurring myopia of between1.00 D. and -4.00 D. with astigmatism no greater than -1.50 D. who signed the informed consent document were entered into this six-months study. Coroeal topography, Confocal microscopy, ultrasound coroeal thickness, aberrometry, and slit-Iamp biomicroscopy were used to assess changes occurring in the coroea. Unaided logMAR visual acuity, subjective refraction, and a questionnaire were used to monitor vision and subjective symptoms. FolIow-up visits are scheduled at one day, one week, two weeks, one month, three months and six months. Results: To date seven subjects have completed their l-month visit. Unaided acuity improved from 0.89:tO.22 OD/0.74:tO.30 OS to 0.03:1:.12 OD/O.Ol:1:.13 OS. Myopia was decreased from -2.61 D.:tO.85 OD/-2.07 D.:tO.29 OS to +0.07 D.:tO.40 OD/Plano:tO.32 OS. Shape factor as deterrnined by coroeal topography increased from 0.83:1:0.13 OD/0.82:tO.07 OS to 1.26:tO.24 OD/1.32:tO.31 OS indicating a shift from a prolate to oblate coroeal surface. Total central coroeal thickness as determined by Orbscan pachymetry was 555.57:1:49.89 mm OD/551.57:1:46.88 mm OS at baseline and 548.71:1:43.61 mm OD/547.00:l:47.23 mm OS at l-month. Total central coroeal thickness as deterrnined by Sonogage ultrasonic pachymetry was 549.71:1:37.88 mm OD/546.43:1:44.11 mm OS at baseline and 561.75:1:44.68 rnm OD/565.50:1:47.22 mm OS at l-rnonth. Total central coroeal thickness as determined by confocal microscopy was 517.52:1:69.15 rnm OD/474.15:1:65.69 mm OS at baseline and 502.17:1:86.82 mm OD/544.00:I:48.23 mm OS at l-month. Central coroeal epithelial thickness measured with the Sonogage was 46.7I:tO.76 mm OD/46.86:tO.38 mm OS at baseline and 47.25:1:1.26 rnm OD/47.25:tO.50 mm OS at l-month. Central coroeal epithelial thickness measured with confocal microscopy was 50.72:1:17.61 mm OD/44.85:1:7.03 mm OS at baseline and 53.53:1:9.13 mm OD/31.96:1:17.92 mm OS at 1month. Discussion: The amount of myopia reduction found at the l-week visit was clinically insignificant from the I-month results indicating that the fulI effect is achieved by one week. However, neither total nor epithelial coroeal thickness measurements show any significant changes from baseline regardless of the method used. Central and inferior coroeal sensitivity measurements also showed no significant changes. These preliminary results demonstrate the effectiveness of the CKR lens design at reducing myopia and improving unaided visual acuity.

MODELS OF POSTERIOR CORNEAL CHANGE WITH OVERNIGHT ORTHOKERATOLOGY
Helen Owens*, Leon Gamer*, Greg Gamble**. *Department of Optometry & Vision Science, University of Auckland, AuckIand, New Zealand. ** Department of Medicine, University of AuckIand, AuckIand, New Zealand.
Background The mechanism relating refractive change to coroeal tissue changes foIlowing overoight orthokeratology remains uncertain, particularly with regard to the contribution fcom the posterior coroeal surface. The aim of this work was to assess topographical changes in the posterior coroeal surface following one month of overnight orthokeratology lens wear and to model those changes in relation to coroeal oedema and moulding. Metbods Coroeal topography, subjective refraction, ultrasound coroea1 thickness and Purkinje imaging techniques were used to assess changes occurring in the coroea for 20 subjects over a course of one month, at four separate time periods. Biometric measurements concentrated on areas in the central 2.5mm and mid-peripheral 5mm of the coroea. Results Orthokeratology successfuIly reduced subjects' myopia in an exponential manner over the course of a month. The reduction in myopia was accompanied by flattening of anterior and posterior coroeal surfaces, both centrally and mid-peripheralIy. Changes from baseline were significant at all times for the anterior coroea and significant over the initial 2 weeks for the posterior surface. Conclusions Qur results demonstrate that the coroea bends during the initial 2 weeks of overoight lens wear. Models of the central coroea suggest that a combination of oedema and moulding is likely to account for these posterior coroeal changes.

ORTHOKERATOLOGY WITH OVERNIGHT WEAR REVERSE.GEOMETRY CONTACT LENSES IN PRACTICE
Dr. A J P Rouwen, MD, PhD S. de Graaf, Opt, Orthop. Central Military & University Hospital, Refractive Surgical Centre, Utrecht, The Netherlands
The goal of this presentation is to make the delegates familiar with the fitting process of these lenses in practice, to elaborate the limitations of the results attainable with these lenses and aIso to show methods to judge the final optical results of these lenses. Reverse geometry OK lenses work by virtue of the eccentricity value of the corneal shape. Correction of low-grade myopia with limited correction of comeal astigmatism depends on the actual eccentricity value of the coroea. The amount of correctable myopia can be calcuIated fram the measured corneal shape. Low grade, not completely stable rnyopia in young patients is a good indication for this technique as compared to refractive surgery. Together with refractive surgery this technique is a method to have 20/20 V A during the day without spectacle or contact lens wear.
The fitting procedure is completely different from normal RGP fitting as is the judgement of fluorescein fitting pattems. Calculation is made more easy, because we used a computer program made by NKL, the laboratory also manufacturing these BE MountfordINoack Australian design lenses. The topographic response after the first night sleep in the triallenses is used to find the correct lens to order for successive wear. The correct assessment of these topographic (difference) plots after overnight triallens wear is essential to get good results with this OK technique. On the basis of this response the calculating program often advises to refit with another triallens in order to get the proper first night result and to find the definite recipe lens. The correct power in the finallenses is only used during the (early) night when the patients want to see more with large pupils or fading effect from lens wear the night before. On the other hand some patients are able to skip lens wear every other night, while keeping their correction. Limitations in both refractive effect and topographical changes are shown on the basis of three actual fittings done in our clinic. AdditionalIy some common adverse effects are shown.

RESULTS OF THE FIRST CLINICAL STUDY IN FRANCE ON OVERNIGHT ORTHOKERATOLOGY
Dr. Adrien SARFATI Hopital Hotel-Dieu, Paris, France Claude HATCHUEL, Aix-en-Provence, France
In this clinical study we investigated the performance of modern, overnight Orthokeratology using RGP lenses with reverse geometry design and high oxygen permeability. The patient group included persons of varied ages, and myopia of -1.00 D to-3.50 D. We tested the clinical and optical efficacy of the procedure and the limits of reducing myopia by ovemight wear of the Ortho K lenses over a penod of three months. All patients were regularly controlled for corneal complications. We determined the optimal fitting procedures and evaluated which patients would be eligible for overnight Orthokeratology . Initial results confirm earlier studies: We obtained good results and good safety on patients with low myopia.

IS ORTHO-K - OK?
Eef van der Worp Prívate Ophthalmology Clinic, Amsterdam, The Netherlands
Orthokeratology has recently gained renewed attention in the interoationalliterature and on conferences around the world. Reasons for the spectacular comeback of this mode of lens wear are primarily the development of new technology (coroeal topography and better lens designs), new insights in the mechanisms oí coroeal reshaping, and the possibility of overnight wear. lt is our task to evaluate whether this modified technique of orthokeratology is an acceptable mode of vision correction. Is Ortho-K OK?
The mechanism behind orthokeratology is still unclear. Central coroeal thinning is reported in a number of occasions and is presumed to cause the refractive change. The central coroeal thinning appears to be epithelial in origino Compression of epithelial cells, redistribution of epithelial cells or both might cause the effect. In the mid-periphery of the coroea, an increase in coroeal thickness has been noted. According to the leading investigators in this field, this change is presumably stromal. Refractive change usually is restricted 10 low myopia, refractive error change of 2.25D +/- 1.00D is COIWllon. Unaided visual acuity of 20/20 in the morning is possible and is reported in most (74%) successful cases. Higher myopia will typically reduce the optical treatrnent zone and may result in visual compromise. Some lens designs seem better in treating higher myopia than others. Ortho-k is approved by the US Food and Drug Administration for up to -6.00D. Hyperopic and presbyopic corrections are in development, but not available at this stage.
The preferred method for myopia reduction for the vast majority of researchers and practitioners is overoight Ortho-k. Oxygenation of the coroea and the risk of bacterial epithelial binding is therefore an issue and will be discussed in this presentation. There are case reports in the interoational literature reporting coroeal infectious ulcers, predominantly Pseudomonas aeruginosa, resulting in a loss of best corrected visual acuity after recovery in some cases. Most cases reported are from Asian countries, especially China.
Another potential risk in overoight Ortho-k is lens adherence, especially upon awakening. Tear film composition plays a vital role in this and tear supplements in the moroing are usually recommended. Some leos designs have the tendency to create more lens adherence than others. In addition, coroeal rings have been observed in some patients after wearing Ortho-k lenses. These rings are unknown in origin and similar rings have been found in post-PRK and post LASIK patients as well. The location of the coroeal iron rings in Ortho-k coincided with the fitting curve of the reverse-geometry rigid contact lens, suggesting that the rings might have developed from tear pooling.

MORPHOLOGICAL CHANGES OF RABBIT CORNEA BY ORTHOKERATOLOGYLENS
Masao Matsubara and Yasuo Ishii
Dept. of Ophthalmology Tokyo Women's Medical University, Daini Hospital & New Vision Institute, Japan

PUlpose: To investigate the histopathological and physiological changes of coroea after the use of orthokeratology lens.
Methods: Orthokeratology lens (OK lens) (BE, Dreim or Contex. Targeted reduction; 3 or 6 D) was placed on right eyes of white rabbits for 7 hours daily. Eyes were enucleated after 1, 4 and 12 weeks, and served to light or electron microscopic study. Left eyes were used as controls. Eyes with OK lens (Euclid) for 2 or 3 weeks were served to histochemical study.
Results: With successful topographical reduction in refraction, epithelial layer was histologically stable after any periods of the schedule. Epithelial cells showed normal configuration at the center of the coroea. Histochemical staining suggested almost normal function of epitheliallayer. Electron microscopic study revealed higher electron density in epithelial cells than in those of control. Glycogen granules in epithelial ceU cytoplasm and proteoglycans in deep stroma slightIy increased at the center. No other apparent abnormal findings were observed.
Conclusions: Orthokeratology lens gave topographical change with very mild functional and morphological changes in rabbit coroea.

A NEW CUSTOMIZED ESA.CURVE REVERSE GEOMETRY LENS DESIGN FOR OVERNIGHT ORTHOKERATOLOGY
Antonio Calossi Firenze, Italy
We developed and patented a new design and calculation method to custornize a multicurve reverse geometry lens. This new design is based on a biconic model on which we developed an esa-curve custornize reverse geometry lens designo We present the results of a pilot study to evaluate the success and safety of treatment with these ovemight orthokeratology contact lenses. Refractive error, comeal topography, and biomicroscopic data were collected to determine the amount of refractive error change achieved, corneal changes, and a safety profile of overnight wear of these lenses for overnight orthokeratology. In this pilot study we treated 30 eye of 15 patients aged from 18 to 43 years, without any tear, comeal, ocular andlor systemic disease at the baseline time and without any previous ocular surgery. The baseline refractive error was from -1.00 to4.00 D spherical equivalent, WTR astigmatism up to 1.50 D and ATR or oblique astigmatism up to 0.75 D. The preliminary results of our pilot study indicate that the cornea responds rapidly to the application of these custornize esa-curve reverse geometry lenses, with significant central comeal flattening and improvement in visual acuity after just 60 min of lens wear; the comeal shape change from prolate to oblate asphericity after 1 night of wear; improvement in unaided visual acuity up to 20/20 can be obtained for at least 10 h after lens removal in an average time of 10 nights. Qur data suggest that the comeal epithelium is able to be molded or redistributed very rapidly in response to the tear ftlm forces generated behind this reverse-geometry lenses designo Up to 1 year of overnigbt wear, safety and efficacy of the procedure appear to be favorable; however, future studies are needed to determine the more long-term outcomes of treatment

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