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Zhang Y, Li T, Li Z, Dai M, Wang Q, Xu C. Clinical outcomes of single-step transepithelial photorefractive keratectomy and off-flap epipolis-laser in situ keratomileusis in moderate to high myopia: 12-month follow-up. BMC Ophthalmol 2022; 22:234. [PMID: 35606707 PMCID: PMC9128200 DOI: 10.1186/s12886-022-02443-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2021] [Accepted: 05/03/2022] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND To compare the quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TPRK) and off-flap epipolis-laser in situ keratomileusis (Epi-LASIK) in moderate to high myopia. METHODS In this prospective self-control study, we included patients with moderate to high myopia who were randomized to undergo TPRK in one eye and Epi-LASIK in the other eye. Twelve-month follow-up results for visual acuity, refraction, ocular high-order aberrations, contrast sensitivity, postoperative pain, epithelial healing, and haze grade were assessed. RESULTS A total of 64 eyes (32 patients) were enrolled in the study. More eyes completed re-epithelialization in the TPRK group than in the Off-flap Epi-LASIK group 3-4 days postoperatively, while all eyes completed re-epithelialization by 7 days. More eyes achieved a visual acuity (both UDVA and CDVA) of better than 20/20 in the TPRK group than in the Off-flap Epi-LASIK group. The ±0.50 D predictability for correction of the spherical equivalent (SE) was higher in the eyes of the TPRK group (91%) than in those of the off-flap Epi-LASIK group (80%) 12 months after surgery. No significant differences in ocular aberrations, including coma, spherical, and trefoil, were found between the two groups at 12 months. There were also no significant differences in visual acuity, contrast sensitivity, pain, and haze grading between the two groups. CONCLUSIONS Both TPRK and off-flap Epi-LASIK are safe, effective, and predictable treatments for moderate to high myopia with comparable surgical outcomes. TRIAL REGISTRATION This study was retrospectively registered on ClinicalTrial.gov ( NCT05060094 , 17/09/2021).
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Affiliation(s)
- Yunjie Zhang
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China
| | - Tiankun Li
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China
| | - Zhangliang Li
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China
| | - Mali Dai
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China
| | - Qinmei Wang
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China
| | - Chenchen Xu
- Eye Hospital and School of Ophthalmology and Optometry, Wenzhou Medical University, Wenzhou, Zhejiang, China.
- National Clinical Research Center for Ocular Diseases, Wenzhou, Zhejiang, China.
- Eye Hospital of Wenzhou Medical University Hangzhou Branch, 270 West Xueyuan Road, Wenzhou, 325027, Zhejiang, China.
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Mohammadpour M, Rezaei F, Heirani M, Khorrami-Nejad M. Comparison of Postoperative Symptoms of Alcohol-Assisted Versus Mechanical Epithelial Removal in Photorefractive Keratectomy: A Contralateral Double Blind Clinical Trial. Eye Contact Lens 2021; 47:655-659. [PMID: 34393178 DOI: 10.1097/icl.0000000000000829] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/30/2021] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the short-term complaints of postoperative pain, and other ocular discomfort symptoms in patients who underwent photorefractive keratectomy (PRK) with alcohol-assisted epithelial removal in one eye versus mechanical debridement in the other eye. METHOD A prospective, interventional, contralateral double blind clinical trial was performed on 164 eyes of 82 candidates of PRK surgery. The patients were divided into two groups. The first group was alcohol-assisted PRK group in which the epithelial removal was performed on their right eye. The second group was mechanical PRK group in which epithelial removal was performed on their left eye. A numerical rating scale was given to the patients to describe the severity of postoperative pain on the first day following PRK. Postoperative discomfort symptoms including the complaints of light sensitivity, tearing, blurring, and foreign body sensation was also provided by the survey form. RESULTS One day following PRK, the mean pain score of the alcohol-assisted PRK group and the mechanical PRK group was 3.4±3.1 and 4.1±3.3, respectively (P=0.019). The highest scores recorded for alcohol-assisted and mechanical treated groups were burning (5.22) and light sensitivity (5.46), respectively. Sixty-eight (82.9%) of all patients experienced postoperative pain, and in 52 (76.5%) of them, the time of pain onset was less than 2 hrs. CONCLUSION We found less pain and discomfort using alcohol-assisted technique compared with mechanical epithelial removal that was provided by a detailed pain and ocular discomfort symptoms assessment one day following PRK surgery.
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Affiliation(s)
- Mehrdad Mohammadpour
- Translational Ophthalmology Research Center (M.M., F.R., M.H., M.K.-N.), Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran; and School of Rehabilitation (M.K.-N.), Tehran University of Medical Sciences, Tehran, Iran
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Coupling of Fibrin Reorganization and Fibronectin Patterning by Corneal Fibroblasts in Response to PDGF BB and TGFβ1. Bioengineering (Basel) 2020; 7:bioengineering7030089. [PMID: 32784578 PMCID: PMC7552779 DOI: 10.3390/bioengineering7030089] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 08/02/2020] [Accepted: 08/05/2020] [Indexed: 11/17/2022] Open
Abstract
We previously reported that corneal fibroblasts within 3D fibrin matrices secrete, bind, and organize fibronectin into tracks that facilitate cell spreading and migration. Other cells use these fibronectin tracks as conduits, which leads to the development of an interconnected cell/fibronectin network. In this study, we investigate how cell-induced reorganization of fibrin correlates with fibronectin track formation in response to two growth factors present during wound healing: PDGF BB, which stimulates cell spreading and migration; and TGFβ1, which stimulates cellular contraction and myofibroblast transformation. Both PDGF BB and TGFβ1 stimulated global fibrin matrix contraction (p < 0.005); however, the cell and matrix patterning were different. We found that, during PDGF BB-induced cell spreading, fibronectin was organized simultaneously with the generation of tractional forces at the leading edge of pseudopodia. Over time this led to the formation of an interconnected network consisting of cells, fibronectin and compacted fibrin tracks. Following culture in TGFβ1, cells were less motile, produced significant local fibrin reorganization, and formed fewer cellular connections as compared to PDGF BB (p < 0.005). Although bands of compacted fibrin tracks developed in between neighboring cells, fibronectin labeling was not generally present along these tracks, and the correlation between fibrin and fibronectin labeling was significantly less than that observed in PDGF BB (p < 0.001). Taken together, our results show that cell-induced extracellular matrix (ECM) reorganization can occur independently from fibronectin patterning. Nonetheless, both events seem to be coordinated, as corneal fibroblasts in PDGF BB secrete and organize fibronectin as they preferentially spread along compacted fibrin tracks between cells, producing an interconnected network in which cells, fibronectin and compacted fibrin tracks are highly correlated. This mechanism of patterning could contribute to the formation of organized cellular networks that have been observed following corneal injury and refractive surgery.
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Khattak A, An-Nakhli F. Incidence and quantification of corneal haze by Pentacam Scheimpflug densitometry following photorefractive keratectomy for myopia in virgin and post corneal transplant eyes with dark irides. Saudi J Ophthalmol 2020; 34:8-12. [PMID: 33542980 PMCID: PMC7849850 DOI: 10.4103/1319-4534.301295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 07/26/2019] [Accepted: 02/26/2020] [Indexed: 12/03/2022] Open
Abstract
PURPOSE: To assess the incidence and quantification of corneal haze after myopic photorefractive keratectomy in virgin and post corneal transplant eyes with dark irides. METHODS: In this retrospective study at the tertiary eye hospital, the corneal haze was evaluated by slit-lamp and quantified by Pentacam Scheimpflug densitometry after myopic photorefractive keratectomy with mitomycin C in virgin eyes (group I) and post corneal transplant eyes (group II) with dark irides over 12 months. RESULTS: Group I compromised 126eyes from 77patients (35males and 42females) aged 31.31 years (24.11–36.18 years), and group II compromised 44eyes from 33patients (18males and 15females) aged of 32.25 years (26.15–36.66 years). The incidence of corneal haze was 9.5% (95%CI: 5.0%–16%) and 6.8% (95%CI: 1.4–18.7%) in group I and II respectively (P = 0.587). The corneal densitometry was 22.69 ± 8.28GSU preoperatively and 17.98 ± 3.13GSU at 12 months postoperatively (P = 0.010) in group I. The corneal densitometry was 21.86 ± 6.22GSU preoperatively and 21.23 ± 4.29GSU at 12 months postoperatively (P = 0.815) in group II. High corneal maximal densitometry was associated with the thin central corneal thickness (P = 0.027), the presence of haze (P = 0.028), post-keratoplasty (P = 0.004), steep keratometry (P = 0.035). CONCLUSION: The incidence of corneal haze was comparable in virgin and post corneal transplant eyes. The Pentacam Scheimflug densitometry can be helpful in the diagnosis of corneal haze; however, the cutoff values need to be studied further in larger studies.
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Affiliation(s)
- Ashbala Khattak
- Dhahran Eyes Specialist Hospital, Eastern Province, Saudi Arabia
| | - Fouad An-Nakhli
- Dhahran Eyes Specialist Hospital, Eastern Province, Saudi Arabia
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Oberflächenverfahren in der refraktiven Chirurgie. SPEKTRUM DER AUGENHEILKUNDE 2019. [DOI: 10.1007/s00717-019-00439-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Zarei-Ghanavati S, Shandiz JH, Abrishami M, Karimpour M. Comparison of mechanical debridement and trans-epithelial myopic photorefractive keratectomy: A contralateral eye study. J Curr Ophthalmol 2019; 31:135-141. [PMID: 31317090 PMCID: PMC6611919 DOI: 10.1016/j.joco.2019.01.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 12/25/2018] [Accepted: 01/04/2019] [Indexed: 11/29/2022] Open
Abstract
Purpose To compare clinical outcomes between mechanical debridement photorefractive keratectomy (m-PRK) and trans-epithelial photorefractive keratectomy (t-PRK) in myopic patients. Methods Eighty eyes of 40 myopic patients with age between 18 and 55 years were included in this study. In each patient, one eye was randomly assigned for t-PRK, using the Amaris laser's ORK-CAM software and the other eye for m-PRK, using a spatula. Stromal ablation was done by Schwind Amaris 750S. Uncorrected and best corrected visual acuity (BCVA), refractive outcomes, epithelial healing, pain, and discomfort were compared between the groups on day 1, 3, 7 and month 1, 3, and 6. Results Preoperative spherical equivalent (SE) were −3.97 ± 2.08 diopter (D) and −3.98 ± 2.06 D in m-PRK and t-PRK eyes, respectively (P = 0.981). Operation time was significantly shorter in the t-PRK group than m-PRK (P < 0.001). Postoperative pain was experienced significantly higher in the t-PRK group measured by 11-point numeric scale of pain questionnaire on the first postoperative day (P < 0.001). Photophobia, tearing, and vision fluctuation were also significantly higher in the t-PRK group postoperatively. However epithelial defect size and re-epithelialization time were lower in the t-PRK group (P = 0.012 and P < 0.001, respectively). Postoperative parameters including SE, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and contrast acuity did not show any significant difference between the two groups during all intervals. Conclusions Although epithelial defect size and epithelial healing time were lower in t-PRK, postoperative pain, photophobia, and vision fluctuation were significantly less in the m-PRK group in the first postoperative days. There was no statistically significant difference between the groups after one week, and both mechanical and trans-epithelial techniques were shown to be safe and effective.
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Affiliation(s)
| | - Javad Heravian Shandiz
- Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.,Refractive Errors Research Center, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Mojtaba Abrishami
- Eye Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
| | - Maliheh Karimpour
- Refractive Errors Research Center, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran.,Student Research Committee, Mashhad University of Medical Sciences, Mashhad, Iran
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Automated Detection and Classification of Corneal Haze Using Optical Coherence Tomography in Patients With Keratoconus After Cross-Linking. Cornea 2018. [DOI: 10.1097/ico.0000000000001570] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Comparison of visual and refractive results after transepithelial and mechanical photorefractive keratectomy in myopia. Int Ophthalmol 2017; 38:627-633. [DOI: 10.1007/s10792-017-0501-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 03/13/2017] [Indexed: 12/14/2022]
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Shapira Y, Mimouni M, Levartovsky S, Varssano D, Sela T, Munzer G, Kaiserman I. Comparison of Three Epithelial Removal Techniques in PRK: Mechanical, Alcohol-assisted, and Transepithelial Laser. J Refract Surg 2015; 31:760-6. [DOI: 10.3928/1081597x-20151021-05] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2015] [Accepted: 08/11/2015] [Indexed: 11/20/2022]
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10
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Kang H, Choe CM, Choi TH, Kim SK. Comparison of Clinical Results between Transepithelial Photorefractive Keratectomy and Brush Photorefractive Keratectomy. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2014. [DOI: 10.3341/jkos.2014.55.9.1284] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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McGrath LA, Lee GA. Techniques, indications and complications of corneal debridement. Surv Ophthalmol 2013; 59:47-63. [PMID: 24239444 DOI: 10.1016/j.survophthal.2013.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2012] [Revised: 03/24/2013] [Accepted: 03/26/2013] [Indexed: 11/18/2022]
Abstract
The cornea is the most exposed surface of the eye and, as such, is vulnerable to external trauma and the risk of infection. Many corneal diseases alter shape, surface, and transparency and thus result in reduced vision. The external position of the cornea, however, lends itself to diagnostic and therapeutic maneuvers that are commonly performed and readily done in the clinic. More sophisticated techniques require the use of complex equipment such as excimer and femtosecond laser. Complications that develop from poor healing and/or secondary infection are best avoided with appropriate technique, antisepsis, and modification of wound healing. We review corneal debridement in the management of corneal disease.
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Affiliation(s)
- Lindsay A McGrath
- City Eye Centre, Brisbane, Queensland, Australia; School of Medicine, University of Queensland, Brisbane, Queensland, Australia
| | - Graham A Lee
- City Eye Centre, Brisbane, Queensland, Australia; School of Medicine, University of Queensland, Brisbane, Queensland, Australia; Department of Ophthalmology, Royal Brisbane & Women's Hospital, Brisbane, Queensland, Australia.
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Sia RK, Ryan DS, Stutzman RD, Psolka M, Mines MJ, Wagner ME, Weber ED, Wroblewski KJ, Bower KS. Alcohol versus brush PRK: Visual outcomes and adverse effects. Lasers Surg Med 2012; 44:475-81. [DOI: 10.1002/lsm.22036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/29/2012] [Indexed: 11/08/2022]
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Spadea L, Verrecchia V. Effectiveness of scraping and mitomycin C to treat haze after myopic photorefractive keratectomy. Open Ophthalmol J 2011; 5:63-5. [PMID: 22262990 PMCID: PMC3258567 DOI: 10.2174/1874364101105010063] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Revised: 07/27/2011] [Accepted: 09/21/2011] [Indexed: 11/26/2022] Open
Abstract
To report the possibility of post myopic photorefractive keratectomy (PRK) haze treatment in a patient with expressed reluctance for any additional laser therapy. Seven months after bilateral PRK with subsequent development of corneal haze and refractive regression in both eyes, a 37-old-year male patient presented a best-spectacle corrected visual acuity (BSCVA) of 20/30 in the right eye and of 20/22 in the left eye. Both eyes were sequentially treated by scraping the stromal surface and application of mitomycin C (MMC) for 2 minutes. Both eyes had significant improvement in corneal transparency. Eighteen months after this treatment BSCVA had improved to 20/20 in each eye. No toxic effects were observed during either re-epithelialization or follow-up periods. In conclusion scraping and application of MMC could be considered a good tool in the treatment of selected cases of haze after myopic PRK, especially with patients that are reluctant to undergo a secondary laser procedure.
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Affiliation(s)
- Leopoldo Spadea
- Department of Surgical Sciences, University of L'Aquila, Eye Clinic, L'Aquila, Italy
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Barreto J, Barboni MT, Feitosa-Santana C, Sato JR, Bechara SJ, Ventura DF, Alves MR. Intraocular Straylight and Contrast Sensitivity After Contralateral Wavefront-Guided LASIK and Wavefront-Guided PRK for Myopia. J Refract Surg 2010; 26:588-93. [DOI: 10.3928/1081597x-20090930-01] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 09/03/2009] [Indexed: 11/20/2022]
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McLaren JW, Bourne WM, Patel SV. Standardization of corneal haze measurement in confocal microscopy. Invest Ophthalmol Vis Sci 2010; 51:5610-6. [PMID: 20539002 DOI: 10.1167/iovs.10-5614] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Corneal stromal haze cannot be compared in longitudinal studies or across laboratories without standardization. In this study, a method was devised of standardizing image brightness in confocal microscopy of the cornea. METHODS Thirty-six normal corneas of 18 untreated volunteers and 35 corneas of 18 patients 3 years after LASIK were examined by slit scanning confocal microscopy. The mean image intensity of each frame was adjusted for daily variations in sensitivity of the microscope by using scans through a solution of Amco Clear (GSF Chemicals, Columbus, OH). Adjusted image intensities were expressed in scatter units (SU), representing the concentration of Amco Clear that produced the same intensity as the image. The intensity from the stroma in corneas after LASIK was compared to that in untreated corneas by using generalized estimating equation models. RESULTS In the untreated corneas, image brightness was 1079 ± 242 and 758 ± 142 SU in the anterior and mid stroma, respectively. Three years after LASIK, image intensity in the flap was 740 ± 186 SU, approximately 30% lower than in corresponding stroma of the untreated corneas (P < 0.001). At mid stroma, brightness was 715 ± 117 SU after LASIK, and was not significantly different from brightness in untreated corneas (P = 0.26). CONCLUSIONS Clinical confocal microscopy provides a high-resolution measurement of corneal haze, and Amco Clear provides a means of standardizing these measurements. This method can detect subtle decreases in haze in the corneal flap 3 years after LASIK and could be used to examine changes in haze after lamellar keratoplasty.
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Affiliation(s)
- Jay W McLaren
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA.
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Reinstein DZ, Archer TJ, Gobbe M. Corneal ablation depth readout of the MEL 80 excimer laser compared to Artemis three-dimensional very high-frequency digital ultrasound stromal measurements. J Refract Surg 2010; 26:949-59. [PMID: 20128534 DOI: 10.3928/1081597x-20100114-02] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 10/15/2009] [Indexed: 11/20/2022]
Abstract
PURPOSE To evaluate the accuracy of the ablation depth readout for the MEL 80 excimer laser (Carl Zeiss Meditec). METHODS Artemis 1 very high-frequency digital ultrasound measurements were obtained before and at least 3 months after LASIK in 121 eyes (65 patients). The Artemis-measured ablation depth was calculated as the maximum difference in stromal thickness before and after treatment. Laser in situ keratomileusis was performed using the MEL 80 excimer laser and the Hansatome microkeratome (Bausch & Lomb). The Aberration Smart Ablation profile was used in 56 eyes and the Tissue Saving Ablation profile was used in 65 eyes. All ablations were centered on the corneal vertex. Comparative statistics and linear regression analysis were performed between the laser readout ablation depth and Artemis-measured ablation depth. RESULTS The mean maximum myopic meridian was -6.66±2.40 diopters (D) (range: -1.50 to -10.00 D) for Aberration Smart Ablation-treated eyes and -6.50±2.56 D (range: -1.34 to -11.50 D) for Tissue Saving Ablation-treated eyes. The MEL 80 readout was found to overestimate the Artemis-measured ablation depth by 20±12 μm for Aberration Smart Ablation and by 21±12 μm for Tissue Saving Ablation profiles. CONCLUSIONS The accuracy of ablation depth measurement was improved by using the Artemis stromal thickness profile measurements before and after surgery to exclude epithelial changes. The MEL 80 readout was found to overestimate the achieved ablation depth. The linear regression equations could be used by MEL 80 users to adjust the ablation depth for predicted residual stromal thickness calculations without increasing the risk of ectasia due to excessive keratectomy depth as long as a suitable flap thickness bias is included.
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Kalyvianaki MI, Kymionis GD, Kounis GA, Panagopoulou SI, Grentzelos MA, Pallikaris IG. Comparison of Epi-LASIK and Off-Flap Epi-LASIK for the Treatment of Low and Moderate Myopia. Ophthalmology 2008; 115:2174-80. [PMID: 19041475 DOI: 10.1016/j.ophtha.2008.08.025] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2008] [Revised: 08/08/2008] [Accepted: 08/08/2008] [Indexed: 11/18/2022] Open
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Farid M, Morishige N, Lam L, Wahlert A, Steinert RF, Jester JV. Detection of corneal fibrosis by imaging second harmonic-generated signals in rabbit corneas treated with mitomycin C after excimer laser surface ablation. Invest Ophthalmol Vis Sci 2008; 49:4377-83. [PMID: 18502995 DOI: 10.1167/iovs.08-1983] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Recent studies have shown that confocal imaging of second harmonic-generated (SHG) signals can detect corneal collagen organization. The purpose of this study was to assess whether SHG signals can detect differences in corneal fibrosis after excimer laser surface ablation (photorefractive keratectomy [PRK]). METHODS Rabbits received 9-D PRK in one eye followed by treatment with either mitomycin C (MMC) or vehicle. Corneal haze was measured by in vivo confocal microscopy before and 2, 4, 8, and 12 weeks after surgery. Animals were then killed and corneas were evaluated by visible and nonlinear confocal microscopy. RESULTS PRK induced significant haze in vehicle-treated corneas that peaked at 2 weeks and remained elevated at 12 weeks after surgery. MMC treatment significantly (P < 0.05) reduced corneal haze at 2 weeks and was essentially normal by 12 weeks. Imaging of SHG signals in vehicle-treated eyes showed an anterior layer of collagen forming a honeycomb network blending into a dense mat of irregularly arranged collagen fibers that overlaid normal orthogonally arranged collagen lamellae. MMC treatment showed normal collagen organization at the surface. Fibrotic tissue was associated with a high cell density and alignment of intracellular actin filaments with collagen fiber bundles. In MMC-treated eyes, an anterior acellular zone overlaid a sparsely populated stroma containing isolated and enlarged keratocytes. CONCLUSIONS Imaging of SHG signals provides a sensitive means for detection of corneal fibrosis after surface ablation and can be used to assess the effects of antifibrotic therapy on corneal healing after refractive surgery.
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Affiliation(s)
- Marjan Farid
- Gavin S Herbert Eye Institute, University of California, Irvine Medical Center, Orange, California 92868, USA
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Affiliation(s)
- Parag Parekh
- Minnesota Eye Consultants, 9801 Dupont Ave. South, Suite 200, Bloomington, MN 55431, USA
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Ghadhfan F, Al-Rajhi A, Wagoner MD. Laser in situ keratomileusis versus surface ablation: Visual outcomes and complications. J Cataract Refract Surg 2007; 33:2041-8. [PMID: 18053901 DOI: 10.1016/j.jcrs.2007.07.026] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2007] [Accepted: 07/28/2007] [Indexed: 11/17/2022]
Affiliation(s)
- Faisal Ghadhfan
- Anterior Segment Division, Department of Ophthalmology, Research Department, King Khaled Eye Specialist Hospital, Riyadh, Kingdom of Saudi Arabia.
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McCally RL, Connolly PJ, Stark WJ, Jain S, Azar DT. Identical excimer laser PTK treatments in rabbits result in two distinct haze responses. Invest Ophthalmol Vis Sci 2006; 47:4288-94. [PMID: 17003417 PMCID: PMC1790975 DOI: 10.1167/iovs.05-1469] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To obtain objective light-scattering measurements to test a hypothesis that identical PTK treatments cause distinct low- and high-level light-scattering responses in rabbit corneas. METHODS An excimer laser was used to produce identical 6-mm diameter phototherapeutic keratectomy treatments (PTK) in 32 pigmented rabbits. Eyes were treated by performing a 40-microm epithelial ablation, followed by a 100-mum stromal PTK. Objective scattering measurements were made before treatment, weekly up to 5 weeks, and then biweekly to 9 weeks. Confocal microscopy was performed on several corneas at 4 and 7 weeks. RESULTS Mean scattering levels split into distinct low- and high-scattering groups 2 weeks after treatment and remained distinct until week 7 (P < 0.003). Scattering in the low group reached a broad peak that lasted from weeks 2 to 4 at approximately 3 times the pretreatment level. Scattering in the high group peaked at 3 weeks at approximately 12 times the pretreatment level. Scattering levels diminished after reaching their peaks. Confocal images showed a band of highly reflective material in the anterior stroma that extended much deeper in corneas from the high group. The reflective band in the highly scattering corneas obscured the posterior stroma from view for up to 5 weeks. CONCLUSIONS Quantitative scattering data obtained with the scatterometer suggest that identical PTK treatments indeed result in distinct low- and high-level light-scattering responses in rabbits.
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Affiliation(s)
- Russell L McCally
- The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20723-6099, USA.
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Abstract
Confocal microscopy allows non-invasive in vivo imaging of the ocular surface. Its unique physical properties enable microscopic examination of all layers of the cornea and have been used to investigate numerous corneal diseases: epithelial changes, numerous stromal degenerative or dystrophic diseases, endothelial pathologies, corneal deposits, infections, and traumatic lesions. It offers a new approach to study the physiological reactions of the cornea to different stimuli and the pathophysiologic events leading to corneal dysfunction in certain diseases. Confocal microscopy proves to be a powerful diagnostic tool and is especially of value in certain corneal diseases by allowing straightforward and non-invasive recognition of the pathologic conditions.
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Abstract
PURPOSE OF REVIEW To summarize the known uses of in-vivo confocal microscopy in refractive surgery, highlighting the current developments in the field. RECENT FINDINGS Examination of the cornea after laser in-situ keratomileusis demonstrated that the keratocyte density within the laser in-situ keratomileusis flap and anterior residual corneal bed continued to decline during the entire 3-year period of the study. The progressive loss of keratocytes in the flap and anterior portion of the residual corneal bed could have long-term implications in terms of corneal stability, refractive stability and cellular integrity after laser in-situ keratomileusis. Additional studies showed that the density of sub-basal nerves decreased by 90% 1 month after laser in-situ keratomileusis. At some point between 3 and 6 months after laser in-situ keratomileusis, the sub-basal nerves began to recover and by 2 years they had reached approximately 50% of their original preoperative density. Analysis of sub-basal nerve density after photorefractive keratectomy reported that the nerve density completely recovered to preoperative levels by 2 years. Other confocal microscopic studies demonstrated that the microscope can detect infectious organisms in vivo, without stains or dyes. SUMMARY The confocal microscope is a unique diagnostic instrument that can be used to evaluate corneal healing, long-term stability and to assess complications after refractive surgery. The ability of the device to view in-vivo cellular detail, microorganisms, inflammatory cells, epitheliod cells, fibrosis and measure the postoperative thickness of the residual corneal bed after laser in-situ keratomileusis, in a noninvasive manner, highlights the unique capabilities of this instrument.
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Abstract
The conceptual advantage of phototherapeutic keratectomy (PTK) include the option to remove diseased tissue on a micrometer scale. Although less invasive than other forms of corneal surgery, it remains a surgical procedure which carries inherent risks. In phototherapeutic indications this risk is higher than in otherwise healthy eyes undergoing photorefractive surgery. Potential general complications include wound-healing problems, infection, inflammation, or a recurrence of the underlying disease. More specifically, PTK is associated with unwanted refractive changes, such as a hyperopic shift or an irregular astigmatism. In this review, we discuss these problems along with prevention and treatment strategies in detail.
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Affiliation(s)
- G Geerling
- Klinik für Augenheilkunde, Bayerische Julius-Maximilian-Universität, Josef-Schneider-Strasse 11, 97080 Würzburg.
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Lee HK, Lee KS, Kim JK, Kim HC, Seo KR, Kim EK. Epithelial healing and clinical outcomes in excimer laser photorefractive surgery following three epithelial removal techniques: mechanical, alcohol, and excimer laser. Am J Ophthalmol 2005; 139:56-63. [PMID: 15652828 DOI: 10.1016/j.ajo.2004.08.049] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/19/2004] [Indexed: 11/21/2022]
Abstract
PURPOSE To evaluate epithelial healing, postoperative pain, and visual and refractive outcomes after photorefractive keratectomy (PRK) using three epithelial removal techniques. DESIGN Prospective, nonrandomized, comparative trial. METHODS SETTING Department of Ophthalmology, Yonsei University College of Medicine and Balgensesang Ophthalmology Clinic, Seoul, Korea. INTERVENTIONS For the PRK procedure, the corneal epithelium was removed in one of three ways: mechanically (conventional PRK [PRK]) in 88 eyes of 44 patients; using excimer laser (transepithelial PRK [tPRK]) in 106 eyes of 53 patients; or using 20% diluted alcohol, laser-assisted subepithelial keratomileusis (LASEK) in 106 eyes of 53 patients. MAIN OUTCOME MEASURES Epithelial healing, postoperative pain, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and remaining refractive error. RESULTS The mean postoperative pain scores were 4.84 +/- 1.45 for PRK, 4.71 +/- 1.62 for tPRK, and 4.63 +/- 1.52 for LASEK (P = .125). The mean epithelial healing rates were 12.3 +/- 4.6 for PRK, 15.2 +/- 4.9 for tPRK, and 18.1 +/- 5.2 mm2/day for LASEK (P < .001). The postoperative 6-month remaining mean spherical equivalents (diopters) were -0.46 +/- 1.01 for PRK, 0.18 +/- 0.91 for tPRK, and -0.82 +/- 1.18 for LASEK (P = .01). The LASEK group showed less favorable UCVA than other groups. There was no significant difference in BSCVA between the groups. CONCLUSIONS Postoperative pain, subepithelial opacity and BSCVA were similar regardless of the epithelial removal procedure. A faster epithelial healing rate did not result in better visual or refractive outcomes. Using the same nomogram, tPRK resulted in a slight overcorrection, and LASEK resulted in a slight undercorrection.
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Affiliation(s)
- Hyung Keun Lee
- Institute of Vision Research, Yonsei University College of Medicine, Seoul, Korea
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Dennis RJ, Beer JMA, Baldwin JB, Ivan DJ, Lorusso FJ, Thompson WT. Using the Freiburg Acuity and Contrast Test to measure visual performance in USAF personnel after PRK. Optom Vis Sci 2004; 81:516-24. [PMID: 15252351 DOI: 10.1097/00006324-200407000-00013] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Photorefractive keratectomy (PRK) may be an alternative to spectacle and contact lens wear for United States Air Force (USAF) aircrew and may offer some distinct advantages in operational situations. However, any residual corneal haze or scar formation from PRK could exacerbate the disabling effects of a bright glare source on a complex visual task. The USAF recently completed a longitudinal clinical evaluation of the long-term effects of PRK on visual performance, including the experiment described herein. METHODS After baseline data were collected, 20 nonflying active duty USAF personnel underwent PRK. Visual performance was then measured at 6, 12, and 24 months after PRK. Visual acuity (VA) and contrast sensitivity (CS) data were collected by using the Freiburg Acuity and Contrast Test (FrACT), with the subject viewing half of the runs through a polycarbonate windscreen. Experimental runs were completed under 3 glare conditions: no glare source and with either a broadband or a green laser (532-nm) glare annulus (luminance approximately 6090 cd/m) surrounding the Landolt C stimulus. RESULTS Systematic effects of PRK on VA relative to baseline were not identified. However, VA was almost 2 full Snellen lines worse with the laser glare source in place versus the broadband glare source. A significant drop-off was observed in CS performance after PRK under conditions of no glare and broadband glare; this was the case both with and without the windscreen. As with VA, laser glare disrupted CS performance significantly and more than broadband glare did. CONCLUSIONS PRK does not appear to have affected VA, but the changes in CS might represent a true decline in visual performance. The greater disruptive effects from laser versus broadband glare may be a result of increased masking from coherent spatial noise (speckle) surrounding the laser stimulus.
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Erie JC, Hodge DO, Bourne WM. Confocal microscopy evaluation of stromal ablation depth after myopic laser in situ keratomileusis and photorefractive keratectomy. J Cataract Refract Surg 2004; 30:321-5. [PMID: 15030819 DOI: 10.1016/j.jcrs.2003.09.058] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/03/2003] [Indexed: 11/15/2022]
Abstract
PURPOSE To compare the measured ablation depth after myopic laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) with the predicted ablation depth. SETTING Mayo Clinic, Rochester, Minnesota, USA. METHODS Twenty-five eyes of 15 patients had PRK and 25 eyes of 15 patients had LASIK to correct refractive errors between -1.50 diopters (D) and -11.00 D. The corneas were examined by in vivo confocal microscopy before and 1 month after both procedures. Thickness measurements were obtained from digital-image analysis of confocal scans. The measured ablation depth, an estimate of the actual photoablation depth, was obtained as the surgically induced stromal thinning between the preoperative and the 1-month post-PRK or post-LASIK central stromal thickness. The predicted ablation depth was recorded from the laser's software program. RESULTS In LASIK, the measured ablation depth (81 microm +/- 34 [SD]) was 25% greater than the predicted ablation depth (65 +/- 13 microm, P =.007) and the difference between the measured and predicted ablation depths was positively associated with the mean ablation depth (r = 0.81, P<.001). In PRK, there was no difference between the measured ablation depth (48 +/- 19 microm) and the predicted ablation depth (47 +/- 18 microm, P =.84). CONCLUSION Significantly more tissue than predicted was removed by LASIK than by PRK excimer photoablation with the laser system used in this study.
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Affiliation(s)
- Jay C Erie
- Department of Ophthalmology, Mayo Clinic, Rochester, MN 55905, USA.
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Kaufman SC, Musch DC, Belin MW, Cohen EJ, Meisler DM, Reinhart WJ, Udell IJ, Van Meter WS. Confocal microscopy. Ophthalmology 2004; 111:396-406. [PMID: 15019397 DOI: 10.1016/j.ophtha.2003.12.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVE To review the available evidence for the use of confocal microscopy in diagnosing infectious keratitis and for other applications for ophthalmic practice. METHODS A MEDLINE search of the peer-reviewed literature for the years 1990 to 2001 yielded 94 citations. The search was limited to studies of human subjects published in English with abstracts. The Ophthalmic Technology Assessment Committee Cornea Panel evaluated these 94 articles for possible clinical relevance and selected 51 (54%) for content review by the panel members. Of these 51 articles, 24 were selected for the panel methodologist to review and rate according to the strength of evidence. RESULTS Of the 24 articles, 21 (87.5%) were classified as case reports or case series and were rated as level III evidence. Three articles were classified as independent, masked, or objective comparisons performed in a narrow spectrum of patients or in a nonconsecutive series of patients and were rated as level II evidence. No studies were rated as level I evidence, defined as an independent masked comparison of an appropriate spectrum of consecutive patients. CONCLUSION Confocal microscopy is a new technology with clinical applications in ophthalmology. Although confocal microscopy has been used in other fields of medicine, the optical transparency of the cornea and other structures of the eye provides a unique opportunity to apply this technology. The targeted literature review of 24 articles found no level I studies to support the use of confocal microscopy in the management of eye disorders. Three level II studies pertained to promising clinical applications of the confocal microscope and provided evidence that supports the use of confocal microscopy as an adjunctive modality for diagnosing Acanthamoeba keratitis. The remaining 21 articles, rated as level III evidence, focus on the use of confocal microscopy to facilitate the diagnosis of infectious keratitis, including amoebic and fungal, but currently there are no definitive studies of its role in the differential diagnosis of this condition. There are also level III studies that support the use of the confocal microscope in refractive surgery. Facilitating the diagnosis of infectious keratitis and applying the confocal microscope to refractive surgery may hold the greatest promise of this new technology.
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Jalbert I, Stapleton F, Papas E, Sweeney DF, Coroneo M. In vivo confocal microscopy of the human cornea. Br J Ophthalmol 2003; 87:225-36. [PMID: 12543757 PMCID: PMC1771516 DOI: 10.1136/bjo.87.2.225] [Citation(s) in RCA: 226] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
AIMS To describe the optics of in vivo confocal microscopy, its advantages over previous methods, and to summarise the literature that arose from its use for the observation of the human cornea. A critical review of the clinical usefulness of this new technology for the corneal examination is undertaken. METHODS Confocal microscopes obtain increased resolution by limiting the illumination and observation systems to a single point. Rapid scanning is used to reconstruct a full field of view and allows for "real time" viewing. RESULTS Coronal sections of the in situ epithelium, Bowman's membrane, stroma, and endothelium can be visualised at a resolution of 1-2 micro m. A backscattered light intensity curve allows objective measurements of sublayer thickness and corneal haze to be taken. In vivo confocal microscopy is therefore particularly useful in the areas of infective keratitis, corneal dystrophies, refractive surgery, and contact lens wear, where it aids in differential diagnosis and detection of subtle short and long term changes. Real time endothelial cell assessment can also be performed. CONCLUSION Because of their ability to visualise living tissue at cellular levels, confocal microscopes have proved useful additions to the current clinical tools.
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Affiliation(s)
- I Jalbert
- Cooperative Research Centre for Eye Research and Technology, University of New South Wales, Sydney, Australia.
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Abstract
PURPOSE To analyze clinical and in vivo microstructural characteristics of both corneas of a 13-year-old male subject with Scheie's syndrome and compare the observations with the pathologic reports in the literature. METHODS Standard clinical examination and real-time, slit-scanning in vivo confocal microscopy were performed and repeated after 1 year. RESULTS In vivo confocal microscopy images at all cellular layers demonstrated brighter intercellular spaces than those of normal corneas. Cicatrization of the anterior stroma was identified, and the keratocytes of the middle and posterior stroma exhibited markedly altered morphology, often round or elliptical in shape, and with clearly demarcated, hyporeflective centers. The nerve fibers of the subbasal plexus were somewhat more irregular and difficult to distinguish, possibly due to underlying fibrosis. CONCLUSIONS The potential of in vivo confocal microscopy to highlight microstructural alterations of the intact human cornea and evaluate such changes over time might reduce reliance on histopathologic investigations in such conditions and contribute to the ophthalmic management of the mucopolysaccharidoses in the future.
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Affiliation(s)
- Christina N Grupcheva
- Department of Ophthalmology, Faculty of Medical and Health Science, Auckland, New Zealand
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Ivarsen A, Stultiens BAT, Møller-Pedersen T. Validation of confocal microscopy through focusing for corneal sublayer pachymetry. Cornea 2002; 21:700-4. [PMID: 12352089 DOI: 10.1097/00003226-200210000-00013] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To evaluate the accuracy and precision of confocal microscopy through focusing (CMTF) for corneal sublayer pachymetry. METHODS A tandem scanning confocal microscope equipped with a nonapplanating contact objective was used to perform CMTF. The accuracy of CMTF measurements was evaluated using nine custom-made calibration contact lenses (PMMA) with varying thickness (300-600 microm) and radius of curvature (7.0-9.0 mm). The influence of immersion fluid stabilization and the consequence of prolonged corneal examination were assessed by performing CMTF in rabbits. Additionally, factors related to the instrumental setup and to sedation of experimental animals were examined. RESULTS For all calibration contact lenses, the thickness measured by CMTF was within +/-1.0 microm of the certified value. Varying the target thickness or radius of curvature had no consistent impact on the high accuracy of CMTF. When performing CMTF in vivo, z-axis motion was readily identified by sampling and comparing both in- and out-scans. Apart from involuntary eye movements, z-axis motion was due to initial thinning of the immersion fluid with stabilization obtained after approximately 1.5 minutes. Continued confocal examination led to slight but significant swelling of both the stroma (0.5 microm/min) and epithelium (0.1 microm/min). CONCLUSIONS CMTF is an accurate and precise technique for corneal sublayer pachymetry with concurrent display of cellular morphology. The precision of CMTF can be improved by allowing time for methylcellulose stabilization and by performing repeated two-way (in and out) scans to account for z-axis motion.
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Affiliation(s)
- Anders Ivarsen
- Department of Ophthalmology, Aarhus University Hospital, Denmark
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Petroll WM, Yu A, Li J, Jester JV, Cavanagh HD, Black T. A prototype two-detector confocal microscope for in vivo corneal imaging. SCANNING 2002; 24:163-170. [PMID: 12166802 DOI: 10.1002/sca.4950240401] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Confocal microscopy through-focusing (CMTF) of the cornea produces a three-dimensional (3-D) display of corneal structure and intensity profiles that allow objective measurements of corneal sublayer thickness and relative assessment backscattering of light. In this study, a prototype confocal instrument was evaluated in which a photon counting photomultiplier tube (PMT) detector was added to provide faster and more quantitative measurements, while still maintaining the imaging capability of the microscope. To acquire images and measure backscattered light simultaneously, an uncoated pellicle beam splitter was incorporated into the light path of the confocal microscope. This beam splitter reflects 8% of the confocal signal to the PMT. The CMTF scans were performed on four rabbits using the prototype instrument. Corneal images and 3-D reconstructions acquired with and without the beam splitter in the light path appeared identical. Both the camera and PMT CMTF curves had easily identifiable peaks corresponding to the epithelium, basal lamina, and endothelium. No significant differences were found between PMT and camera CMTF measurements of epithelial, stromal, or corneal thickness (n = 12 scans). Furthermore, a high correlation was found between camera and PMT measurements (linear regression analysis, y = 0.999 x -0.4, r = 0.99, p < 0.001). The data suggest that by adding a pellicle beam splitter, CMTF intensity data can be acquired using a PMT. The PMT has a faster sampling rate and greater dynamic range than the camera and provides a count of the photons detected. Thus, the instrument has the potential for improving corneal pachymetry and back-scattering measurements while still providing high-resolution corneal images.
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Affiliation(s)
- W Matthew Petroll
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas 75390-9057, USA.
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Gokmen F, Jester JV, Petroll WM, McCulley JP, Cavanagh HD. In vivo confocal microscopy through-focusing to measure corneal flap thickness after laser in situ keratomileusis. J Cataract Refract Surg 2002; 28:962-70. [PMID: 12036637 DOI: 10.1016/s0886-3350(02)01275-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
PURPOSE To measure flap thickness in laser in situ keratomileusis (LASIK) patients using in vivo confocal microscopy through-focusing (CMTF) and compare measured versus intended flap thickness achieved by 2 microkeratomes, the Automated Corneal Shaper(R) (ACS) (Chiron Bausch & Lomb) and the Hansatome (Bausch & Lomb). SETTING Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA. METHODS Twenty-seven eyes of 27 patients were examined by in vivo CMTF 3 to 12 months after LASIK was performed with the ACS (12 patients) or Hansatome (15 patients) microkeratome. The central cornea was scanned, and the epithelium, flap, stroma, and total corneal thickness were measured. Normalized flap thickness (NFT) was also calculated to account for changes in epithelial thickness that may have occurred postoperatively. RESULTS The mean posterior stromal thickness was 341.1 microm +/- 53.9 (SD) (range 233 to 431 microm) in the ACS group and 320.3 +/- 42.3 microm (range 258 to 382 microm) in the Hansatome group. The mean nonnormalized flap thickness was 132.7 +/- 12.5 microm (range 11 to 151 microm) in the ACS group and 167.4 +/- 21.4 microm (range 141 to 209 microm) in the Hansatome group. The NFT was 129.6 +/- 9.5 microm and 158.4 +/- 22.1 microm, respectively. Both microkeratomes cut significantly less than intended (P <.05); however, the ACS cut a thinner-than-intended thickness in all cases, and the Hansatome cut thicker than intended in 13% of cases. The Hansatome also showed significantly greater variability in flap thickness than the ACS (P <.05). CONCLUSIONS A significant difference in precision was noted between the 2 microkeratomes. The findings emphasize the importance of performing thickness measurements and the usefulness of in vivo CMTF in making these determinations to ensure the safety and effectiveness of LASIK.
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Affiliation(s)
- Fusun Gokmen
- Department of Ophthalmology, University of Texas Southwestern Medical Center at Dallas, USA
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