Topography versus non-topography-guided photorefractive keratectomy with corneal cross-linking variations in keratoconus

INTRODUCTION

Effective therapy for corneal ectatic diseases, such as iatrogenic corneal ectasia, keratoconus, and pellucid marginal degeneration, involve confronting two specific parameters: the corneal optical deficiency and the biomechanical inconsistency of the irregular cornea

. Contact lenses have corrected patients with irregular astigmatism for years (scleral lenses and rigid gas permeable contact lenses) in mild cases of keratoconus, and penetrating keratoplasty has been the surgical option in severe cases. Other effective surgical methods are now being used, such as intracorneal ring segments and deep anterior lamellar keratoplasty while other approaches were proposed and attempted in the past, such as conductive keratoplasty and epikeratophakia

.

在學習函數綜合應用知識時，可以引發學生思考其圖象(有無交點、交線圍成的圖形面積、數形結合等)，也可以通過多媒體向學生展示不同函數所表示的圖象，學生通過這些圖象的變換很快就能理解函數的概念了.除了多媒體教學，教師還可以組織學生參加動手繪畫等有趣的活動來學習數學.綜上所述，高中數學的教學應該有意識、有目的、有策略地針對學生邏輯思維能力培養的需要進行變通，讓學生在日常生活中養成邏輯思維的習慣，以此提高高中數學教學效率、促進學生學習效率的提高.

Corneal collagen cross-linking (CXL) opened a new horizon in the effective treatment of progressive corneal ectasia

.The blend of ultra-violet A and riboflavin as a light sensitivity factor produced inter-fibrillary connection between cornea stromal collagen fibers, and as a result, decreased corneal deformability, corneal resistance, and stabilized keratoconus

.With CXL, the issue of biomechanical instability has been effectively confronted, as indicated by the confirmation that CXL has been successful in stopping the progression of ectatic disorders

.

射頻模塊采用5 V 外部供電，其主要供電需求為3.3 V和5 V，可分為控制部分和下變頻變頻部分。控制部分僅僅是STC15W408S控制器的電源，采用通用的LM1117-3.3穩壓到3.3 V。下變頻變頻部分電源涉及到低噪聲放大器、鎖相環、混頻器等噪聲敏感器件的供電，需要選擇高文波抑制比的低壓差穩壓器[31]。MIC5245系列與MIC5205系列專為射頻器件穩壓而設計，采用該兩個系列作為射頻部分的穩壓器件。圖8展示了系統部分電源網絡。

[21] Richardson H W., “Economies and Diseconomies of Agglomeration”, in Urban Agglomeration and Economic Growth, Springer Berlin Heidelberg, 1995, pp. 123-155.

However, the visual outcomes and the topography of patients treated only by CXL demonstrate no change or insignificant change due to remaining irregular astigmatism. Excimer laser surgery in the form of non-topography-guided and topographyguided photorefractive keratectomy, besides decreasing irregular astigmatism, changes the shape of the cornea improving visual outcomes

. The combination of CXL with excimer laser photorefractive keratectomy has recently gained interest in treating mild to moderate keratoconus

. However, there is still no evidence confirming the potential benefits of topography-guided photorefractive keratectomy method over standard, non-topograph-guided photorefractive keratectomy.This study aims to compare and appraise the visual outcomes of topography and non-topography-guided photorefractive keratectomy with sequential and simultaneous CXL in keratoconus patients.

SUBJECTS AND METHODS

The study received approval from the local ethics committee (IR. SBMU. RETECH.RECH.1400.1216).As a standard protocol, all surgeries were performed by one surgeon (Doroodgar F) after obtaining appropriate written consent from a trained, certified good clinical practice (GCP)examiner.

This prospective study included four groups of keratoconus patients: Sequential topographyguided photorefractive keratectomy with CXL (sequential TGPRK, 19 eyes/10 patients), simultaneous topography-guided photorefractive keratectomy with CXL (simultaneous TGPRK, 15 eyes/8 patients), simultaneous non-topography guided photorefractive keratectomy with CXL (simultaneous non-TG-PRK, 17 eyes/9 patients), and sequential non-topography guided photorefractive keratectomy with CXL (sequential non-TG-PRK, 18 eyes/9 patients). The patients were treated between January 2014 and October 2015.

Inclusion criteria for the study focused on patients over 34y(range from 34 to 41y) with stable corneal topography and refraction for at least six months and an estimated residual bed thickness of ＞410 μm.

9月23日18時，杜家臺分洪閘開始關閉閘門，歷時5分50秒全部關閉完畢。整個分流期間，杜家臺分洪閘共開啟53小時36分，共分流漢江下游超額洪水約2億m3，有效降低仙桃以下河段水位約0.6m，減少仙桃站超保證水位時間50小時。

CXL increases the level of entombed fibrillar linkages enhancing the biomechanical quality of the cornea. Many investigations have confirmed the effective stabilization of keratoconus progression after CXL

. Almost all previous studies have proven that TG-PRK and non-TG-PRK with sequential, and simultaneous CXL are effective and safe and result in good visual performance in keratoconus eyes

. Most studies have reported that simultaneous treatment (TG-PRK and non-TG-PRK followed immediately by CXL) produces excellent results compared to sequential treatment

, and other studies have not indicated a difference between these two methods

. Efficacy and safety of simultaneous and sequential methods would enhance the refractive condition of the eye

.To our knowledge, this is the first study to compare four surgical methods in keratoconus patients. The comparison aims to determine the best method to treat patients with keratoconus and evaluate functional and consistent outcomes. Achieving useful vision comprises enhancing UCVA and BCVA and standardization of corneal topography, demonstrating that these patients are less subject to contact lens use. Therefore, a higher postoperative visual quality would be achieved.

成本信息數據庫是將項目的歷史數據進行沉淀。該數據庫平臺主要用于成本核對，為投資、拿地決策提供信息，為供應商選擇，甚至是項目實施過程中的變更和認質認價提供依據。……