2012 FAQs-Contact Lens

More Contact Lens FAQs

Are colored contacts more expensive? Are contacts bad for your eyes? Are contacts expensive? Are contacts hard to put in? Are contacts safe for kids? Can contacts cause headaches? Can contacts get lost in your eye? Can contact lenses damage your eyes? Can contacts be stored in water? Can you use water as contact solution? Contact stuck in eye? Do contacts make your eyes worse? How contacts are made How contacts work How much do contacts cost?

How to choose contact lenses Is my contact inside out? What are contacts made of? What color contacts should I get? What contacts are right for me? What contacts did they use in Twilight? When contact lenses were invented Where to buy contact lenses with no prescription Which contact lenses are the best? Which contact solution is the best? Why do contacts burn? Why do contacts hurt my eyes? Why do contact lenses expire?

2012 Dạy và học

Bức thư của cố tổng thống Mỹ Abraham Lincoln (1809-1865) gửi thầy hiệu trưởng ngôi trường nơi con trai ông theo học.

Được viết ra từ gần 200 năm trước, lại là ở nước Mỹ, nhưng bức thư vẫn giữ nguyên tính “thời sự” và gợi nhiều suy nghĩ cho chúng ta.

Kính gửi thầy…

Con tôi sẽ phải học tất cả những điều này. Rằng không phải tất cả mọi người đều công bằng, tất cả mọi người đều chân thật. Nhưng xin thầy hãy dạy cho cháu biết: cứ mỗi một kẻ vô lại ta gặp trên đường phố, thì ở đâu đó, sẽ có một con người chính trực; bên cạnh một chính trị gia ích kỷ, sẽ xuất hiện một nhà lãnh đạo tận tâm.

Xin hãy dạy cho cháu biết rằng cứ mỗi một kẻ thù ta gặp ở nơi này thì ở nơi khác ta lại tìm thấy một người bạn. Bài học này sẽ mất nhiều thời gian, tôi biết; nhưng xin thầy hãy dạy cho cháu hiểu rằng một đồng đôla kiếm được do công sức lao động của mình bỏ ra còn quý giá hơn nhiều so với nǎm đô la nhặt được trên hè phố…

Xin hãy dạy cho cháu cách chấp nhận thất bại và cách tận hưởng niềm vui chiến thắng. Xin hãy dạy cháu tránh xa sự đố kỵ. Xin dạy cho cháu biết được bí quyết của niềm vui thầm lặng. Dạy cho cháu biết được rằng những kẻ hay bắt nạt người khác là những kẻ dễ bị đánh bại nhất…

Xin dạy cho cháu biết đến thế giới kỳ diệu của sách… nhưng cũng để cho cháu có đủ thời gian để lặng lẽ suy tư về sự bí ẩn muôn thuở của cuộc sống: đàn chim tung cánh trên bầu trời, đàn ong bay lượn trong nắng, và những bông hoa nở ngát bên đồi xanh.

Ở trường, xin thầy hãy dạy cho cháu biết chấp nhận thi rớt còn vinh dự hơn gian lận khi thi.

Xin hãy tạo cho cháu có niềm tin vào ý kiến riêng của bản thân, cho dù tất cả mọi người xung quanh đều cho rằng ý kiến đó là không đúng…

Xin hãy dạy cho cháu biết cách đối xử dịu dàng với những người hoà nhã và cứng rắn đối với những kẻ thô bạo. Xin tạo cho cháu sức mạnh để không chạy theo đám đông khi tất cả mọi người đều chạy theo thời thế.

Xin hãy dạy cho cháu biết phải lắng nghe tất cả mọi người nhưng cũng xin thầy dạy cho cháu biết cần phải sàng lọc những gì nghe được qua một tấm lưới Chân Lý để cháu chỉ đón nhận những gì tốt đẹp mà thôi.

Xin hãy dạy cho cháu biết cách mỉm cười khi buồn bã… Xin hãy dạy cho cháu biết rằng không có sự xấu hổ trong những giọt nước mắt. Xin hãy dạy cho cháu biết chế giễu những kẻ yếm thế và cẩn trọng trước sự ngọt ngào đầy cạm bẫy.

Xin hãy dạy cho cháu rằng có thể bán cơ bắp và trí tuệ cho người ra giá cao nhất nhưng không bao giờ được để cho ai ra giá mua trái tim và tâm hồn mình.

Xin hãy dạy cho cháu biết ngoảnh tai làm ngơ trước một đám đông gào thét… và đứng thẳng người bảo vệ lẽ phải.

Xin hãy đối xử với cháu dịu dàng nhưng đừng vuốt ve nuông chiều cháu bởi vì chỉ có sự thử thách của lửa mới tôi luyện nên những thanh sắt cứng rắn. Hãy giúp cháu có can đảm biểu lộ sự thiếu kiên nhẫn và có đủ kiên nhẫn để biểu lộ sự can đảm.

Xin hãy dạy cho cháu biết rằng cháu phải luôn có niềm tin tuyệt đối vào bản thân bởi vì khi đó cháu sẽ luôn có niềm tin tuyệt đối vào nhân loại.

Đây quả là một yêu cầu quá lớn, tôi biết, thưa thầy, nhưng xin thầy cố gắng hết sức mình… con trai tôi là một cậu bé tuyệt vời.

2012 Phẫu thuật mã hóa màu lấy tế bào ung thư

Quyen Nguyen: Phẫu thuật mã hóa màu
http://www.ted.com/talks/lang/vi/quyen_nguyen_color_coded_surgery.html

Một khám phá mới của một Bác Sĩ Phẫu thuật rất trẻ người VN, Nguyễn Quyên, hiện ở Đại Học San Diego (UCSD).
Đây là một phương pháp mổ lấy tế bào ung thư hoàn toàn mới và có một áp dụng tầm mức rất lớn. Hiện nay chỉ là thành công lúc ban đầu, chưa bào đảm sẽ được thành công trên bình diện lớn, điều này còn phải đợi nhiều BS phẫu thuật khác nhúng tay vào và chấp nhận. Cái quan trong của phương pháp mổ này là chỉ có tề bào ung thư mới phát quang (fluorescence) (do proteases hiện diện trong tế bào ung thư thủy giải fluorescent probe và phát huỳnh quang, còn tế bào thường không có enzyme này và sẽ không phát ra anh sáng này). Phương pháp này giúp surgeon nhìn thấy một cách khá chắc chắn chỗ cần mổ ngay tức khắc và sẽ không bỏ sót. Nếu được kiểm tra và công nhận thì chắc có thể là được giải thưởng Nobel prize in Medicine, như là GS Roger Tsien, người đã phát minh ra technique này và đã được lãnh giải thưởng Nobel prize in chemistry cách đây ba năm.
Ông này cũng làm việc tại UCSD và cộng tác với BS VN này. Mời các bạn theo dõi cái video sau đây sẽ rõ.
Một cô bác sĩ trẻ gốc VN đã nghiên cứu được Molecular marker để có thể nhuộm màu các tế bào ung thư (hay tế bào bệnh khác) để bác sĩ có thể cắt bỏ mà không bỏ sót những tế bào bị bệnh lại trong người.
Video clip cô trình bày trước Hội đồng Y khoa về phương pháp mới này:
http://www.ted.com/talks/lang/vi/quyen_nguyen_color_coded_surgery.html

2012 Tự phê bình và Lợi ích nhóm!!

Đảng bộ chính phủ 'tự phê bình'

Cập nhật: 12:24 GMT - thứ tư, 23 tháng 5, 2012

Sau buổi làm việc với các cựu lãnh đạo, các thành viên chính phủ sẽ tiến hành 'phê và tự phê'

Các thành viên chủ chốt của chính phủ đương nhiệm đã có buổi ‘lắng nghe ý kiến đóng góp’ của các lãnh đạo chính phủ đã nghỉ hưu chiều hôm thứ Ba ngày 22/5.

Buổi làm việc này do Ban cán sự Đảng của chính phủ triển khai để thực hiện Nghị quyết trung ương 4 về xây dựng chỉnh đốn Đảng.

Các bài liên quan

• Trung ương Đảng kỷ luật cán bộ
• Trung ương Đảng họp toàn thể lần thứ 4
• Chỉnh đốn đảng để tránh 'sụp đổ'?

Chủ đề liên quan

• Chính trị Việt Nam

Các ông Phan Văn Khải, người tiền nhiệm của Thủ tướng Nguyễn Tấn Dũng, và các cựu phó thủ tướng Đồng Sỹ Nguyên, Nguyễn Mạnh Cầm, Phạm Gia Khiêm, Nguyễn Khánh, Vũ Khoan và Nguyễn Công Tạn đã được chính phủ mời đến đóng góp ý kiến.

Nội dung về buổi làm việc này gần như không được phổ biến và chỉ có rất ít thông tin được đưa trên báo chí Việt Nam về buổi sinh hoạt Đảng quan trọng này của chính phủ.

‘Nguy cơ tự diễn biến’

Theo tường thuật của Thông tấn xã nhà nước thì các cựu lãnh đạo góp ý với chính phủ về các vấn đề cấp bách trong công tác xây dựng Đảng và những điều đảng viên không được làm.

Theo đó, các cựu lãnh đạo yêu cầu ‘đấu tranh quyết liệt liệt đẩy lùi nguy cơ tự diễn biến’ dẫn đến ‘suy thoái về tư tưởng chính trị, đạo đức, lối sống’, đảm bảo nguyên tắc ‘tập trung dân chủ’ trong công việc của chính phủ.

Các vị được mời đến cũng yêu cần chính phủ quan tâm đến việc phòng chống tham nhũng, lãng phí, bình ổn giá nông sản, trích tường thuật của Thông tấn xã.

Sau buổi họp này, các vị cựu lãnh đạo chính phủ sẽ tiếp tục gửi ý kiến đóng góp bằng văn bản đến tập thể Ban cán sự Đảng chính phủ và từng thành viên Ban cán sự có liên quan.

Thủ tướng Nguyễn Tấn Dũng được dẫn lời thay mặt Ban cán sự Đảng cho biết chính phủ ‘trân trọng tiếp thu’ những ý kiến đóng góp của các cựu lãnh đạo mà ông cho rằng ‘thẳng thắn, xác đáng’.

"Bộ máy Nhà nước bị đồng tiền chi phối nên không đặt lợi ích quốc gia, lợi ích của quần chúng lên trên mà làm theo mệnh lệnh của đồng tiền, của các chủ đầu tư."

Lê Hiếu Đằng, nguyên phó chủ tịch Mặt trận Tổ quốc thành phố Hồ Chí Minh

Theo Thông tấn xã Việt Nam thì sau phiên lắng nghe các cựu lãnh đạo này thì Ban cán sự Đảng chính phủ sẽ có buổi tiến hành kiểm điểm, phê bình và tự phê bình theo kế hoạch mà Bộ Chính trị đã đề ra cho các ban Đảng.

BBC đã liên lạc với nguyên phó Thủ tướng Nguyễn Mạnh Cầm nhưng ông nói ông không thể bình luận với BBC mà chỉ góp ý kiến với người có trách nhiệm.

“Tôi cũng sẽ có ý kiến đóng góp nhưng cũng phải suy nghĩ đã,” ông nói, “Cái chính là các đồng chí đó sẽ có sự kiểm điểm của mình là chính.”

Bốn vấn đề lớn

Ông Lê Hiếu Đằng, nguyên phó chủ tịch Mặt trận tổ quốc thành phố Hồ Chí Minh, nói với BBC rằng ‘trách nhiệm của chính phủ trong tình hình vừa qua là rất lớn’.

Với tư cách là đảng viên, ông Đằng cũng nêu ra bốn vấn đề mà đảng bộ của chính phủ phải tiến hành kiểm điểm: sai phạm của các tập đoàn, cưỡng chế thu hồi đất, chống tham nhũng và an ninh quốc gia.

“Chính phủ thông qua các tập đoàn làm thất thoát tiền bạc của dân rất lớn như Vinashin và Vinalines làm thất thoát cả trăm ngàn tỷ bạc,” ông nói và cho biết thủ tướng có trách nhiệm lớn ‘với tư cách là người phụ trách trực tiếp các tổng công ty đó’.

Kinh tế Việt Nam trải qua nhiều sóng gió với các vụ vỡ́ lỡ ở cać tập đoàn nhà nước

“Ruộng đất của người nông dân thì tại sao để chính quyền đàn áp người dân,” ông nói, “Ở Văn Giang sát Hà Nội mà xua cả ngàn quân đi dẹp dân mà chẳng lẽ các vị không biết?”

Vấn đề thư ba mà chính phủ đã làm không tốt, theo ông Đằng, là chống tham nhũng.

“Tại sao Ban chống tham nhũng của chính phủ đến giờ vẫn không có hiệu quả? Có phải là do bao che nhau hoặc không dám trừng trị thuộc hạ của mình?,” ông đặt vấn đề.

Ông nói thêm rằng trạng tham nhũng thất thoát diễn ra ngày càng nhiều và các cơ quan chính phủ có khả năng tham nhũng nhất vì nắm quyền lực trong tay.

Ông Đằng cũng cho rằng chính phủ đã xử lý không tốt vấn đề an ninh quốc phòng.

“Tại sao cho Trung Quốc thuê đất rừng 50 năm tại những vùng xung yếu chiến lược? Ai biết Trung Quốc làm gì mà người Việt Nam bây giờ vào cũng không được?,” ông bức xúc.

Concert-Love music

Xin mời thưởng thức 65 bản nhạc quốc tế bất hủ trên một tiếng đồng hồ, do các nhạc sỹ và dàn nhạc giao hưởng thính phòng lừng danh trên thế giới hòa tấu. 
Chỉ cần bấm vào bản thứ nhất là cứ thế tự động tuần tự nghe hết danh sách.
Hoặc muốn nghe tắt cũng được.

http://www.saigonocean.com/nghenhacHoaTau/jukebox.swf

Mời nghe nhạc xưa:http://sangtao.org/phong-video-nhac

2012 PRK-LASEK

• Journal of Refractive Surgery
• January 2012 - Volume 28 · Issue 1: 65-71
• DOI: 10.3928/1081597X-20111004-01

Abstract

PURPOSE: To evaluate visual outcomes following epi-LASIK compared to photorefractive keratectomy (PRK).

METHODS: Of a total 294 patients aged ≥21 years, 145 (290 eyes) underwent epi-LASIK and 149 (298 eyes) underwent PRK for low to moderate myopia or myopic astigmatism. Epi-LASIK was performed with the Amadeus II epikeratome (Abbott Medical Optics) and PRK with the Amoils rotary epithelial brush (Innovative Excimer Solutions). All ablations were performed using the same excimer laser system. Outcome measures included intraoperative complications, corneal reepithelialization, postoperative pain, uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), corrected distance visual acuity (CDVA), corneal haze, and quality of vision.

See Also

• Thin flap LASIK to Increase the Range of Treatments Using ...
• Effect of Keratometry on Visual Outcomes 1 Month After ...
• LASIK Using the NIDEK EC-5000 for the Correction of ...

RESULTS: Mean preoperative MRSE was −2.97±1.19 diopters (D) for epi-LASIK versus −2.95±1.06 D for PRK. Complete reepithelialization was achieved by postoperative day 4 in 46.9% of epi-LASIK eyes versus 92.4% of PRK eyes, with superior UDVA at postoperative day 1 in the PRK group (P=.002). Using Fisher exact test, a significantly higher percentage of epi-LASIK eyes compared to PRK eyes achieved 20/15 or better at 1 month (25.8% vs 17.8%, P=.031), 3 months (62.3% vs 49.3%, P=.004), 6 months (77.1% vs 57.9%, P<.001), and 12 months (75.9% vs 61.9%, P=.002). A change in MRSE >0.50 D occurred in 8.4% of epi-LASIK eyes within the 3- and 12-month interval versus 17.7% of PRK eyes (P=.04). No differences were noted between the two procedures in CDVA or clinically significant haze.

CONCLUSIONS: Epi-LASIK showed superior refractive efficacy and stability but required more time for wound healing, resulting in inferior early visual outcomes and a tendency to overcorrect higher refractive errors compared to PRK. Both treatments were safe and comparable in terms of pain and haze formation.

From the Ophthalmology Service, Walter Reed Army Medical Center, Washington, DC (Sia, Coe, Ryan); the Department of Ophthalmology, University of Florida College of Medicine, Jacksonville, Florida (Edwards); and The Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland (Bower).
Portions of this material were presented at the Association for Research in Vision and Ophthalmology Annual Meeting, April 27–May 1, 2008, and May 3–7, 2009, Ft Lauderdale, Florida.
The authors have no financial interest in the materials presented herein.
The opinions expressed in this manuscript are those solely of the authors and do not represent the views or official policies of the United States Army or Department of Defense.
AUTHOR CONTRIBUTIONS
Study concept and design (C.D.C., D.S.R., K.S.B.); data collection (C.D.C., D.S.R.); analysis and interpretation of data (R.K.S., C.D.C., J.D.E., D.S.R., K.S.B.); drafting of the manuscript (R.K.S., C.D.C., J.D.E., K.S.B.); critical revision of the manuscript (R.K.S., C.D.C., D.S.R., K.S.B.); statistical expertise (C.D.C.); administrative, technical, or material support (C.D.C.); supervision (C.D.C., D.S.R., K.S.B.)
Correspondence: Rose K. Sia, MD, Center for Refractive Surgery, Walter Reed Army Medical Center, 6900 Georgia Ave, Washington, DC. Tel: 202.782.8327; Fax: 202.782.4653

Received: January 04, 2011

Accepted: August 08, 2011

Posted Online: October 10, 2011

Although LASIK is the most common refractive surgery, surface ablation may be indicated in patients with thin corneas, dry eyes, anterior basement membrane dystrophy, and in patients at risk for trauma due to occupational or recreational considerations.^1–3 However, reepithelialization typically takes 3 to 5 days, during which time patients frequently experience discomfort and fluctuating vision. In addition, photorefractive keratectomy (PRK) can result in corneal haze in up to 2% to 4% of patients.^4,5
Alternative surface techniques have been developed to overcome postoperative PRK pain and haze. Epi-LASIK uses a microkeratome-like device to mechanically separate the epithelium from Bowman layer. The cell morphology and physiology of the resulting epithelial sheet is less affected compared to the chemical separation used in laser epithelial keratomileusis (LASEK)^6,7 and remains intact for at least 24 hours postoperatively,⁷ acting as a mechanical barrier to tear cytokine mediators^8,9 and controlling the corneal wound response. Preliminary studies have shown epi-LASIK to be a safe and effective treatment in the short term.^10–13 This study evaluates the visual outcomes of epi-LASIK compared to PRK up to 12 months postoperatively.

Patients and Methods

The present report compares data from two separate non-randomized, prospective, clinical studies performed at Walter Reed Army Medical Center after approval by the institutional review board and conducted in accordance with the Declaration of Helsinki. After informed consent, consecutive enrollment and treatment were done between May 2005 and July 2006 for PRK and between November 2006 and December 2007 for epi-LASIK. Enrollment criteria and all study methods pre- and postoperatively were identical between the two study cohorts. All patients were aged ≥21 years with myopia or myopic astigmatism between −0.50 and −6.25 diopters (D) of manifest refraction spherical equivalent (MRSE), refractive cylinder up to 3.00 D, stable refraction for at least 12 months, and corrected distance visual acuity (CDVA) of 20/20 or better in both eyes.
All treatments were performed with the LADAR Vision 6000 (Alcon Laboratories Inc, Ft Worth, Texas). Treatments were conventional with a 6.5-mm optical zone; no wavefront-guided treatments were performed. Stromal ablation in PRK was performed after epithelial debridement with the Amoils rotary brush (Innovative Excimer Solutions, Toronto, Ontario). The stromal bed was irrigated with chilled balanced saline solution (BSS), moxifloxacin 0.5% ophthalmic solution and ketorolac 0.4% were administered, and a bandage contact lens applied. In epi-LASIK, a nasal-hinged epithelial flap was created using the Amadeus II epikeratome (Abbott Medical Optics, Santa Ana, California), using manufacturer-recommended epikeratome parameters. After the flap was reflected nasally with use of a microspatula, photoablation was performed on the underlying stroma. During flap creation, if a complication occurred in the first eye (right eye), a new epithelial separator was used for the second eye. Immediately following ablation, the stromal bed was irrigated with chilled BSS before repositioning the epithelial sheet, which was retained whenever possible. After the epithelial sheet was in position and adherent moxifloxacin 0.5% and ketorolac 0.4% were administered, a bandage contact lens was applied.
Postoperative medications for both groups included topical moxifloxacin 0.5% one drop four times daily for 1 week or until complete reepithelialization; fluorometholone 0.1% one drop four times daily for 4 weeks, followed by a 6-week taper; carboxymethylcellulose 0.5% one drop four to eight times daily for 2 weeks and then as needed; topical ketorolac 0.4% up to four times daily for the first 48 hours after surgery as needed; and oxycodone/acetaminophen 5 mg/325 mg orally as needed for postoperative pain. The bandage contact lens was removed on postoperative day 4 if there was no epithelial defect or replaced as needed until complete reepithelialization. Pain, corneal reepithelialization, uncorrected distance visual acuity (UDVA), and any complications such as corneal infiltrates were assessed on postoperative days 1, 4, and 7. Pain was assessed using a five-point scale¹⁰: 0 (none), 1 (minimal), 2 (mild), 3 (moderate), and 4 (severe/worst possible pain).
Uncorrected distance visual acuity, CDVA, MRSE, wavefront aberrometry, patient satisfaction questionnaire, 5% and 25% low contrast visual acuity, and slit-lamp microscopy were assessed at 1, 3, 6, and 12 months postoperatively. The questionnaire focused on visual difficulties and the general satisfaction of postoperative vision using a 10-point scale ranging from 1 (no symptoms) to 10 (severe, disabling symptoms).¹⁴ Low contrast visual acuity was performed using back illuminated logMAR charts with 5% and 25% contrast (Precision Vision Inc, La Salle, Illinois). Corneal haze was graded on a standard 5-point scale: 0 (completely clear), 1+ (trace), 2+ (mild), 3+ (moderate), and 4+ (severe).¹⁵
Aberrometry was performed using the LADARWave wavefront analyzer (Alcon Laboratories Inc) at 850 nm, and the wavefront error at 550 nm was estimated using the instrument’s proprietary chromatic aberration correction factor. Monochromatic aberrations were calculated using pupil diameters of 3 and 6 mm and a Zernike polynomial series up to and including 4th order was calculated for each measurement. For analysis, the absolute root-mean-square (RMS) wavefront error of each Zernike mode was determined and the absolute level of higher order aberrations calculated.
Visual outcomes of epi-LASIK and PRK were compared. Epi-LASIK eyes that had intraoperative complications resulting in flap amputation were excluded from comparative analysis. SPSS software version 16.0 (SPSS Inc, Chicago, Illinois) was used for statistical analysis. Fisher exact test was performed to compare visual outcomes, reepithelialization, and presence of clinically significant haze between epi-LASIK and PRK. The Mann-Whitney test was used to compare early postoperative UDVA, pain scores, and questionnaire data. Odds ratios (OR) were used to determine likelihood of flap complications. P<.05 was considered statistically significant for all testing.

Results

A total of 294 patients, mean age 34.2±7.8 years (range: 21 to 52 years), were enrolled; 145 were consecutively assigned to epi-LASIK and 149 to PRK. Age, gender, preoperative MRSE, UDVA, 25% low contrast visual acuity, central corneal thickness, and keratometry were comparable between groups (Table 1).

Table 1: Preoperative Demographics and Clinical Characteristics of Eyes That Underwent Epi-LASIK and PRK for Low to Moderate Myopia

Intraoperative Complications

A summary of intraoperative epi-LASIK complications is shown in Table 2. Overall, a flap complication occurred in 102 (35%) of 290 epi-LASIK eyes, 57 of which resulted in flap amputation. A relative increase in rate of complications was noted for age ≤34 years and the right eye, but only age was statistically significant (P=.02). Odds ratios are shown in Table 3. No intraoperative complications occurred in the PRK group.

Table 2: Intraoperative Flap Complications That Occurred During Epi-LASIK

Table 3: Preoperative Findings and Risk of Intraoperative Epithelial Flap Complications in Epi-LASIK

Follow-Up Rate

Follow-up availability was comparable between the groups at 1 and 3 months. Significantly fewer epi-LASIK (82.8%) patients returned for 6-month follow-up compared with PRK patients (89.3%, P=.024), whereas significantly more epi-LASIK (86.9%) than PRK patients (75.8%, P=.001) were seen at 12 months. No significant differences were noted in age, gender, baseline MRSE, UDVA, CDVA, or 5% and 25% low contrast visual acuity between initial patients and those seen at each time point studied.

Pain, Epithelial Healing, and Early Visual Recovery

Few patients reported significant pain on postoperative days 1, 4, or 7. Of the 298 eyes treated with PRK and 233 eyes treated with epi-LASIK, reepithelialization was significantly faster in PRK eyes compared with epi-LASIK eyes by postoperative day 4 (92.4% vs 46.9%, P<.001) and postoperative day 7 (99.3% vs 86.3%, P<.001). Five epi-LASIK eyes required an additional visit on postoperative day 10. Epi-LASIK was associated with significantly worse UDVA at postoperative day 1 (P=.002); however, no other significant difference was noted in UDVA in the early postoperative period.

Visual Outcomes

Visual outcomes of eyes treated with epi-LASIK (n=233) and PRK (n=298) were compared.
Safety. Safety indices progressively improved over time for both groups (Table 4). No eye lost ≥2 lines of CDVA in either group at 12 months. Distribution of CDVA line changes in epi-LASIK and PRK groups 12 months postoperatively are shown in Figure A.

Table 4: Safety and Efficacy Indices of Epi-LASIK and PRK

Figure. Twelve-month outcomes of epi-LASIK and PRK. A) Change in corrected distance visual acuity. B) Uncorrected distance visual acuity. C) PRK spherical equivalent attempted vs achieved. D) Epi-LASIK spherical equivalent attempted vs achieved. E) Spherical equivalent refractive accuracy. F) Stability of spherical equivalent refraction.

Efficacy. Efficacy index of epi-LASIK was consistently higher compared to PRK. A statistically significant difference was noted in the number of eyes achieving UDVA of 20/20 or better at 3 months, favoring epi-LASIK (95.5% vs 86.9%, P=.001), but not at any other time point. A significantly higher percentage of epi-LASIK eyes compared to PRK eyes achieved 20/15 or better at 1 month (25.8% vs 17.8%, P=.031), 3 months (62.3% vs 49.3%, P=.004), 6 months (77.1% vs 57.9%, P<.001), and 12 months postoperatively (75.9% vs 61.9%, P=.002) (Fig B).
Predictability. The number of eyes within ±0.50 D of emmetropia was comparable between epi-LASIK and PRK at 1 month (69.5% vs 68.5%, P=.85), 3 months (86.3% vs 81.5%, P=.157), and 6 months (92.3% vs 89.2%, P=.295) but significantly lower for epi-LASIK than PRK at 12 months postoperatively (86.2% vs 92.5%, P=.04). Figures C and D illustrate scatterplots of 12-month attempted versus achieved MRSE. A strong correlation was noted between attempted and achieved MRSE in both groups, but with higher refractive errors, epi-LASIK tends to overcorrect whereas PRK tends to undercorrect. The distribution of final spherical equivalent refraction is shown in Figure E.
Stability. Between 3 and 12 months postoperatively, 17 (8.4%) epi-LASIK eyes compared to 40 (17.7%) PRK eyes had >0.50-D change in refractive spherical equivalent (P=.004). Mean MRSE at each time point is depicted in Figure F.

Quality of Vision

Subjective Visual Performance and Patient Satisfaction. Subjective optical quality was the same between the two procedures at all time points for vision fluctuations, double vision, glare, light sensitivity, halos, starbursts, patient satisfaction, postoperative vision quality, and the chance to have the procedure again. However, epi-LASIK patients reported more frequent artificial tear use at 3 (P<.001) and 6 (P<.001) months and slightly greater difficulty in their daily activities when compared to PRK patients (P=.012).
Low Contrast Visual Acuity. Both 5% and 25% low contrast visual acuity results were comparable between treatment groups at all time points except at 12 months postoperatively; 5% low contrast visual acuity was maintained or improved in 94% of epi-LASIK versus 78.6% of PRK eyes (P<.001) whereas 25% low contrast visual acuity was unchanged or better than preoperative in 87% of epi-LASIK versus 75.8% of PRK eyes (P=.024).
Higher Order Aberrations and Low Contrast Vision. Correlation analysis showed that for 3- and 6-mm artificial pupils, epi-LASIK demonstrated a significant but weak association between increasing higher order aberrations and diminished low contrast visual acuity (3-mm pupil: 25% low contrast visual acuity: r=0.16, P=.019; 6-mm pupil: 5% low contrast visual acuity: r=0.17, P=.015; 25% low contrast visual acuity: r=0.25, P<.001) at 12 months postoperatively. No significant correlation was noted for 3-mm pupils at 5% low contrast visual acuity.
Optical Quality. Mean absolute higher order aberrations increased postoperatively in PRK and epi-LASIK eyes. For a 3-mm artificial pupil, epi-LASIK eyes increased from 0.068±0.029 μm to 0.095±0.036 μm (P<.001) and PRK eyes increased from 0.075±0.10 μm to 0.089±0.043 μm (P=.03) postoperatively. For a 6-mm artificial pupil, epi-LASIK eyes increased from 0.66±0.28 μm to 0.99±0.39 μm (P<.001) and PRK eyes increased from 0.72±0.28 μm to 0.98±0.46 μm (P<.001) postoperatively. However, no significant difference was noted between epi-LASIK and PRK in postoperative optical quality for either a 3-mm pupil (P=.14) or 6-mm pupil (P=.61).

Corneal Haze

Clinically significant haze was observed in two epi-LASIK eyes at 1 month, one eye at 3 months, and one eye at 6 months postoperatively; each case progressively improved and resolved. No PRK eye developed clinically significant corneal haze at any time.

Visual Outcomes After Flap Complication

Two hundred ninety eyes planned to undergo epi-LASIK were subgrouped by whether a quality flap was made (n=188), the flap was removed by automatic amputation or surgeon amputation (n=57), or a complication occurred where the flap was retained (n=45). Measurements of safety, efficacy, predictability, and stability were found to be statistically comparable among the subgroups.
Stromal Incursion. Six (2.1%) of 290 epi-LASIK eyes had inadvertent stromal incursion of the epikeratome during epithelial separation. All treatments were completed during the same session as planned. Mitomycin C (MMC) was not used in any case. Postoperatively, complete reepithelialization was noted in 4 of 6 eyes at postoperative day 4, 1 eye at postoperative day 7, and 1 eye at postoperative day 10. One eye had clinically significant haze at 1 month postoperatively, which subsequently improved with topical steroids. Although midperipheral mild linear corneal scarring was observed in 2 eyes at 3 months postoperatively, no eye lost ≥2 lines of CDVA at any time point. No irregular astigmatism was detected in any of these patients. All eyes had UDVA 20/20 or better starting at 3 months postoperatively.

Discussion

Previous studies of epi-LASIK have shown promising results, with comparisons being made to off-flap versus on-flap epi-LASIK procedures as well as with LASEK procedures.^13,16,17 Our study is different from previous studies as the comparison of epi-LASIK to PRK uses a rotating brush for epithelial removal in the PRK eyes rather than an epikeratome or blunt blade. Early postoperative results showed the two procedures to be equivalent when comparing pain and vision, except for postoperative day 1 when PRK eyes had significantly better UDVA. This is likely due to an edematous and hazy epithelial sheet present in the epi-LASIK eyes. Epi-LASIK eyes were also significantly slower to achieve reepithelialization than PRK eyes. This is consistent with results reported by Torres et al,¹⁸ with epi-LASIK requiring 4.75±1.44 days and PRK eyes requiring 3.95±1.39 days. In contrast, O’Doherty et al¹⁶ reported 72±24 hours for epithelial closure in epi-LASIK eyes, whereas PRK eyes took 96±24 hours. This discrepancy may be a result of different techniques of epithelial removal in the PRK eyes, as Torres et al¹⁸ used a beaver blade whereas O’Doherty et al¹⁶ used an epikeratome.
In the present study, epi-LASIK and PRK were found to be safe procedures but greater refractive stability and efficacy were seen in epi-LASIK than PRK. Although a strong correlation between attempted and achieved refraction was found in both treatments, epi-LASIK seemed to have a tendency to overcorrect higher refractive errors. This observation was similar to the initial results reported in LASEK,^19,20 which were attributed to the PRK nomogram-based treatment and the slower but modulated wound-healing response probably due to the epithelial sheet acting as barrier between tear cytokines and the ablated stroma.^20,21 In contrast, myopic regression and undercorrection tendencies in PRK are likely due to a more intense wound-healing response as more tissues are removed, possibly as a consequence of basement membrane disruption.^7,21 Objective image quality in epi-LASIK seemed to be superior over PRK in terms of retaining or improving low contrast visual acuity but comparable to PRK in terms of absolute level of higher order aberrations. Epi-LASIK patients reported experiencing greater difficulty in performing daily activities but this may not be significantly different from PRK given that the mean score for epi-LASIK patients was 1.5 (±1.0) and PRK was 1.36 (±0.89).
Corneal clarity as measured by clinically significant haze was not detected in PRK eyes but was observed in some epi-LASIK eyes. Kalyvianaki et al¹⁷ reported similar results, with more on-flap epi-LASIK eyes developing haze at 1 and 3 months than off-flap epi-LASIK eyes. The low level of haze is likely a result of mild to moderate levels of myopia treated in the study.
In our study, 35% of epi-LASIK eyes had intraoperative complications, with 20% resulting in amputated flaps. This is similar to previous reports, including O’Doherty et al¹⁶ who reported 33% of eyes resulted in the failed creation of a flap and were converted to PRK. Our data suggest a higher rate of flap complication occurs in younger patients (≤34 years), which could be due to a more adherent epithelium in younger patients.²² Results also suggested complications were more likely to occur in the right eye than the left eye, but this observation is likely biased because the right eye was treated first in all cases. A new epithelial separator was used for the left eye every time a flap complication occurred in the right eye.
Although the study was not designed to compare onflap epi-LASIK versus off-flap techniques, our analysis showed retaining or removing the flap following an unsuccessful creation did not appear to affect the overall visual outcomes, which is consistent with the comparative study by Kalyvianaki et al.¹⁷
Stromal incursion occurred in 2.1% of eyes treated with epi-LASIK in our study, which is comparable to a previously reported 2.99% rate.¹² Despite the small number and insignificant effect on visual outcomes found in our study, we cannot assume that this complication could not be potentially sight-threatening. Two eyes in our study developed midperipheral mild corneal scarring, which could have an adverse effect on their vision if not managed carefully. Widely used in refractive surgery to prevent postoperative haze and scarring, MMC²¹ was used by Katsanevaki et al¹² following stromal incursion whereas no eyes in our study were treated with MMC prophylactically.
In conclusion, epi-LASIK required more time for reepithelialization, had inferior early visual acuity, a tendency to overcorrect higher refractive errors, and a significant number of amputated flaps necessitating conversion to PRK. However, when successful, epi-LASIK showed superior refractive efficacy and stability compared to PRK. Both treatments were comparable in terms of safety and haze formation. Despite being nonrandomized, the prospective design, large sample size, identical study criteria and methods, as well as good follow-up could provide considerable strength for the conclusion of this study. Because this study was limited to myopia up to −6.00 D, the results cannot be extrapolated to higher degrees of myopia or to hyperopic or mixed astigmatism.

References

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2. American Academy of Ophthalmology Refractive Management/Intervention Panel. Preferred Practice Pattern Guidelines. Refractive Errors & Refractive Surgery. San Francisco, CA: American Academy of Ophthalmology; 2007. http://www.aao.org/ppp. Accessed July 28, 2010.
3. Hammond MD, Madigan WP, Bower KS. Refractive surgery in the United States Army, 2000–2003. Ophthalmology. 2005;112(2):184–190. doi:10.1016/j.ophtha.2004.08.014 [CrossRef]
4. Kuo IC, Lee SM, Hwang DG. Late-onset corneal haze and myopic regression after photorefractive keratectomy (PRK). Cornea. 2004;23(4):350–355. doi:10.1097/00003226-200405000-00007 [CrossRef]
5. Seiler T, Wollensak J. Results of a prospective evaluation of photorefractive keratectomy at 1 year after surgery. Ger J Ophthalmol. 1993;2(3):135–142.
6. Pallikaris IG, Katsanevaki VJ, Kalyvianaki MI, Naoumidi II. Advances in subepithelial excimer refractive surgery techniques: epi-LASIK. Curr Opin Ophthalmol. 2003;14(4):207–212. doi:10.1097/00055735-200308000-00007 [CrossRef]
7. Katsanevaki VJ, Naoumidi II, Kalyvianaki MI, Pallikaris G. Epi-LASIK: histological findings of separated epithelial sheets 24 hours after treatment. J Refract Surg. 2006;22(2):151–154.
8. Baldwin HC, Marshall J. Growth factors in corneal wound healing following refractive surgery: a review. Acta Ophthalmol Scand. 2002;80(3):238–247. doi:10.1034/j.1600-0420.2002.800303.x [CrossRef]
9. Li DQ, Tseng SC. Three patterns of cytokine expression potentially involved in epithelial-fibroblast interactions of human ocular surface. J Cell Physiol. 1995;163(1):61–79. doi:10.1002/jcp.1041630108 [CrossRef]
10. Pallikaris IG, Kalyvianaki MI, Katsanevaki VJ, Ginis HS. Epi-LASIK: preliminary clinical results of an alternative surface ablation procedure. J Cataract Refract Surg. 2005;31(5):879–885. doi:10.1016/j.jcrs.2004.09.052 [CrossRef]
11. Dai J, Chu R, Zhou X, Chen C, Qu X, Wang X. One-year outcomes of epi-LASIK for myopia. J Refract Surg. 2006;22(6):589–595.
12. Katsanevaki VJ, Kalyvianaki MI, Kavroulaki DS, Pallikaris IG. One-year clinical results after Epi-LASIK for myopia. Ophthalmology. 2007;114(6):1111–1117. doi:10.1016/j.ophtha.2006.08.052 [CrossRef]
13. Sharma N, Kaushal S, Jhanji V, Titiyal JS, Vajpayee RB. Comparative evaluation of ‘flap on’ and ‘flap off’ techniques of epi-LASIK in low-to-moderate myopia. Eye (Lond). 2009;23(9):1786–1789. doi:10.1038/eye.2008.367 [CrossRef]
14. Schallhorn SC, Kaupp SE, Tanzer DJ, Tidwell J, Laurent J, Bourque LB. Pupil size and quality of vision after LASIK. Ophthalmology. 2003;110(8):1606–1614. doi:10.1016/S0161-6420(03)00494-9 [CrossRef]
15. Fantes FE, Hanna KD, Waring GO III, Pouliquen Y, Thompson KP, Savoldelli M. Wound healing after excimer laser keratomileusis (photorefractive keratectomy) in monkeys. Arch Ophthalmol. 1990;108(5):665–675. doi:10.1001/archopht.1990.01070070051034 [CrossRef]
16. O’Doherty M, Kirwan C, O’Keeffe M, O’Doherty J. Postoperative pain following epi-LASIK, LASEK, and PRK for myopia. J Refract Surg. 2007;23(2):133–138.
17. Kalyvianaki MI, Kymionis GD, Kounis GA, et al. Comparison of epi-LASIK and off-flap epi-LASIK for the treatment of low and moderate myopia. Ophthalmology. 2008;115(12):2174–2180. doi:10.1016/j.ophtha.2008.08.025 [CrossRef]
18. Torres LF, Sancho C, Tan B, Padilla K, Schanzlin DJ, Chayet AS. Early postoperative pain following epi-LASIK and photorefractive keratectomy: a prospective, comparative, bilateral study. J Refract Surg. 2007;23(2):126–132.
19. Feit R, Taneri S, Azar DT, Chen CC, Ang RT. LASEK results. Ophthalmol Clin North Am. 2003;16(1):127–135, viii. doi:10.1016/S0896-1549(02)00063-9 [CrossRef]
20. Azar DT, Suphi T. LASEK. In: Azar DT, Gatinel D, Hoang-Xuan T, eds. Refractive Surgery. 2nd ed. Philadelphia, PA: Elsevier-Mosby; 2007:239–247.
21. Netto MV, Mohan RR, Ambrósio R Jr, Hutcheon AE, Zieske JD, Wilson SE. Wound healing in the cornea: a review of refractive surgery complications and new prospects for therapy. Cornea. 2005;24(5):509–522. doi:10.1097/01.ico.0000151544.23360.17 [CrossRef]
22. Alvarado J, Murphy C, Juster R. Age-related changes in the basement membrane of the human corneal epithelium. Invest Ophthalmol Vis Sci. 1983;24(8):1015–1028.

Table 1 Preoperative Demographics and Clinical Characteristics of Eyes That Underwent Epi-LASIK and PRK for Low to Moderate Myopia

	Epi-LASIK	PRK	PValue*
No. of patients (eyes)	145 (290)	149 (298)	—
Female/male (%)	54/91 (62.8)	48/101 (67.8)	.225
Age (y)	34.1 (21 to 49)	34.8 (21 to 52)	.807
Sphere (D)	−2.68±1.18 (−0.50 to −6.25)	−2.65±1.04 (−0.25 to −5.75)	.716
Cylinder (D)	0.56±0.51 (0.00 to 2.50)	0.59±0.56 (0.00 to 2.75)	.588
MRSE (D)	−2.97±1.19 (−1.00 to −6.25)	−2.95±1.06 (−1.00 to −6.00)	.819
UDVA (logMAR [Snellen])	1.00 (20/200)±0.37	1.00 (20/200)±0.37	.678
CDVA (logMAR [Snellen])	−0.11 (20/16)±0.43	−0.10 (20/16)±0.48	<.001
5% LCVA (logMAR [Snellen])	0.30 (20/40)±0.11	0.33 (20/43)±0.11	.001
25% LCVA (logMAR [Snellen])	0.31 (20/41)±0.08	0.36 (20/46)±0.11	<.001
CCT (μm)	543±35	540±34	.258
Steep K (D)	44.39±1.58	44.36±1.46	.825
Flat K (D)	43.35±2.76	43.55±1.44	.257

Table 2 Intraoperative Flap Complications That Occurred During Epi-LASIK

Complication	No. of Eyes (%)
None	188 (64.8)
Automatic flap amputation	43 (14.8)
Buttonhole flap	17 (5.9)
Hinge tear	14 (4.8)
Surgeon amputation (hinge in treatment zone)	14 (4.8)
Incomplete flap/superficial resection	8 (2.8)
Stromal incursion	6 (2.1)
Total	290 (100.0)

Table 3 Preoperative Findings and Risk of Intraoperative Epithelial Flap Complications in Epi-LASIK

Preop Finding	Odds Ratio (95% CI)	PValue*
Age ≤34 years	1.69 (1.04–2.76)	.02
Right eye	1.63 (1.00–2.65)	.07
Cylinder <1.00 D	1.26 (0.61–2.60)	.59
CCT ≤500 μm	1.23 (0.58–2.58)	.70
Flat K <42.00 D	1.21 (0.62–2.36)	.61
Steep K >46.00 D	0.57 (0.26–1.26)	.16

Table 4 Safety and Efficacy Indices of Epi-LASIK and PRK

Follow-up (mo)	Procedure	Safety Index	Efficacy Index
1	Epi-LASIK	0.61	−0.16
	PRK	0.72	0.39
3	Epi-LASIK	1.09	0.60
	PRK	1.11	0.36
6	Epi-LASIK	1.33	0.78
	PRK	1.18	0.59
12	Epi-LASIK	1.33	0.85
	PRK	1.29	0.67

AUTHORS

From the Ophthalmology Service, Walter Reed Army Medical Center, Washington, DC (Sia, Coe, Ryan); the Department of Ophthalmology, University of Florida College of Medicine, Jacksonville, Florida (Edwards); and The Wilmer Eye Institute, Johns Hopkins University, Baltimore, Maryland (Bower).
Portions of this material were presented at the Association for Research in Vision and Ophthalmology Annual Meeting, April 27–May 1, 2008, and May 3–7, 2009, Ft Lauderdale, Florida.
The authors have no financial interest in the materials presented herein.
The opinions expressed in this manuscript are those solely of the authors and do not represent the views or official policies of the United States Army or Department of Defense.
Correspondence: Rose K. Sia, MD, Center for Refractive Surgery, Walter Reed Army Medical Center, 6900 Georgia Ave, Washington, DC. Tel: 202.782.8327; Fax: 202.782.4653

Received: January 04, 2011

Accepted: August 08, 2011

Posted Online: October 10, 2011

2012 Case finding in the clinic: refractive errors-ca lâm sáng khúc xạ

Case finding in the clinic: refractive errors

Kovin Naidoo OD MPH

Director, ICEE AFRICA, University of Durban-Westville, Department of Optometry, Private Bag X54001, Durban 4000, South Africa

Pirindhavelli Govender BOptom CAS

Research Co-ordinator, ICEE AFRICA

The detection of refractive errors includes effective screening programmes in the school or community. However, the lack of human and other resources often prevent such programmes from occurring. Therefore, patients with many conditions, both refractive and non-refractive, present at clinics. The separation of these patients into refractive and non-refractive conditions is important in the good organisation of eye care clinics, as members of the eye clinic team can then carry out their different duties more effectively.

General considerations

Refractive error can be detected through the routine examination of patients who present to clinics, or through vision screening of the population at large.1An added component is the screening of patients in the clinic setting and combining this with the eye examination. This process will thus incorporate a case history, visual acuity, pinhole visual acuity, retinoscopy and a subjective examination.

Complaints of frontal headaches, poor concentration in school, inappropriate viewing distances, presence of tropias (eye-turns), tilting of the head (high cylinders), and 'squinting'/peering are indicators of refractive error. The pinhole occluder assists in determining the best visual acuity possible with a refractive correction. History combined with visual acuity tests and visual acuity through the pinhole, should enable the clinician to determine if refractive error is the cause of the patient's problem. 2

Retinoscopy is an effective tool in determining the presence of refractive error in adults. Retinoscopy with cycloplegia is the most appropriate method of determining refractive error in children, given the accommodative status of children.3

A subjective refraction should include a binocular balancing technique and a full eye examination to detect other ocular abnormalities.

Detecting refractive cases

Patients referred from a screening programme

If the vision screening programme is known to have been established through proper protocols and training of staff, then the patients should be accepted in the clinic on the basis of the preliminary findings and a full refractive examination conducted. However, many screening programmes are incomplete, only using visual acuities and not a pinhole or +2.00D lens to detect latent hyperopia (hypermetropia). Such patients should be managed in a similar way to the self-presenting patients.

Patients not screened/self-presenting

Primary level

Adults

All patients should be tested using a Snellen acuity test (E Chart) at distance. Those with <6/6 vision should then be further tested with a pinhole test. Should the vision improve to 6/6 then the patient is classified as having a refractive error. Those patients with no improvement to 6/6 with a pinhole, are classified as non-refractive and referred to a secondary level for a full eye examination.

Patients with a refractive error

1. Adults over 45 years of age

The Refractive Error Working Group (REWG)1 recommends that patients with a distance acuity of 6/18 or better (binocularly) should be provided with reading glasses for near. Patients with a visual acuity less than 6/18 should be referred to the secondary level for a refraction.

Patients with specific occupational demands may also need to be referred to the secondary level for a full eye examination.

2. Adults less than 45 years of age

These patients will fall into the early presbyope or pre-presbyope category.

Should there be no occupational demands, patients with 6/18 or better (binocularly) need not be referred for a refraction while those with occupational demands should be referred to the secondary level for a full eye examination. Patients with 6/18 and better but with near occupational visual demands should be dispensed presbyopic glasses ('readers').

3. Children

The REWG recommends that children be referred for refraction should they have a binocular visual acuity less than 6/12.3 They should be referred to the secondary level for a full eye examination (including a cycloplegic refraction).

Secondary Level

Many patients present directly to the secondary level clinics, a consequence of which is an unnecessary increase in patient numbers.

Ancillary personnel (clinic assistants) should screen patients and determine the appropriate management -prior to seeing the Eye Care Practitioner (ECP) -utilising:

    Snellen acuity (E Chart)

    Pinhole test for those with <6/6

    History -to determine age and symptoms

    Visual acuity with a +2.00 D lens for children.

Who is referred for refraction?

1. Adults

    All patients failing the Snellen acuity test, improving to 6/6 with the pinhole test but with less than 6/18 binocularly (Figure 1)

    Patients complaining of headaches and with decreased visual acuity that is improved with a pinhole

    Patients with occupational and special needs experiencing better visual acuity with the pinhole

    Patients who are presbyopic.

2. Children

    All children failing the Snellen test (<6/12 binocularly) (Figure 2) but improving with the pinhole test

    Children with better than 6/12 vision but with no blurring of vision with a +2.00D lens

    Children who present with symptoms consistent with refractive error

    Children with tropias.

Figure 1. Screening adults in an eye clinic

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Figure 2. Screening children in an eye clinic

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Screening: false referrals

Given the percentage of false referrals, children referred for ocular disease evaluation should be referred from the ECP for refraction should no ocular disease be detected.

Malingerers

Malingering could indicate behavioural and other problems or just a desire to wear spectacles and be like parents or friends.

Children failing the Snellen test and showing no improvement in visual acuity could, in fact, be malingerers. Retinoscopy, with cycloplegia, is the best method to determine if a refractive condition exists.

The REWG recommends that children be considered myopic or hyperopic based on the following criteria:3

    Myopia: = -0.50D

    Hyperopia: > + 2.00D

Tests for malingering may also use the following techniques:

    Put plano lenses into the trial frame and observe any improvement

    Move the child closer to the chart and then take visual acuity. No improvement indicates malingering.

General comments

Children with binocular vision of 6/12 or better, with a visual acuity difference between the two eyes of more than two lines on the chart, should be referred for a refraction as amblyopia is a consideration.

If patient numbers are low, the screening protocol could be applied for all patients attending the hospital or clinic, not just the eye clinic patients.

Conclusion

There is great variation in the availability of resources from region to region and country to country. Should the appropriate resources exist then consideration should be given to the 'lowering' of the referral criteria.

References      

1 Dandona R, Dandona L. Refractive error blindness. Bull WHO 2001; 79(3): 237-243.

2 Amos JF, Bartlett JD, Eskridge JB. (1991). Clinical Procedures in Optometry. Philadelphia: Lippincott.

3 World Health Organization. Elimination of avoidable disability due to refractive errors. (WHO/PBL/00.79). Geneva: WHO, 2000.