Development of unilateral corneal ectasia after PRK with ipsilateral preoperative forme fruste keratoconus

PURPOSE: To describe clinical and topographic features of keratectasia after photorefractive keratectomy (PRK) in a patient with abnormal preoperative topography. METHODS: A 25-year-old man underwent uneventful bilateral PRK for moderate myopia of -5.75 -1.75 x 95 in the right eye and -7.50 -1.25 x 80 in the left eye with best spectacle-corrected visual acuity (BSCVA) of 20/25 in both eyes. Preoperative corneal thickness was 500 microm in the right eye and 460 microm in the left eye. The total calculated ablation depth was 70 microm in the right eye and 100 microm in the left eye. Preoperative corneal topography revealed forme fruste keratoconus in the right eye with an inferior-superior ratio of 4. RESULTS: Five years postoperatively, the patient developed unilateral inferior keratectasia in the right eye with refraction of +0.50 -5.50 x 90, BSCVA of 20/100, and central corneal thickness of 481 microm with inferior corneal thickness of 374 microm. CONCLUSIONS: This case report adds to the growing body of evidence in the ophthalmic literature suggesting that patients with preoperative forme fruste keratoconus or early keratoconus may develop clinically significant progression of corneal ectasia after PRK.     

Corneal ectasia after photorefractive keratectomy

Two patients developed corneal ectasia after photorefractive keratectomy (PRK). Case 1 had evidence of early keratoconus preoperatively, with manifest refractions of -4.00 +2.50 x 160 (20/20) in the right eye and -7.00 +3.00 x 180 (20/30) in the left eye; thin corneas (472 microm and 441 microm, respectively); and inferior paracentral steepening in the right eye and central steepening in the left eye on topography. Case 2 had manifest refractions of -8.50 +3.75 x 123 (20/20(-2)) in the right eye and -9.25 +4.00 x 077 (20/20(-1)) in the left eye; corneal thickness of 509 microm and 508 microm, respectively; and symmetric bow-tie patterns in both eyes on topography. Case 2 had a family history suspicious for keratoconus, with a sibling who had bilateral corneal transplantation at a young age. Both patients developed bilateral corneal ectasia after PRK.     

False corneal ectasia in patients referred for corneal crosslinking,topography-guided photorefractive keratectomy,and intrastromal corneal rings

ObjectiveTo determine the misdiagnosis of ectasia in patients referred for corneal crosslinking and possible topography-guided photorefractive keratectomy (PRK) or intrastromal corneal rings.SettingBochner Eye Institute, Toronto, Ontario, Canada.DesignRetrospective data review.MethodsChart review of consecutive cases referred for corneal crosslinking to determine the number of cases of misdiagnosis of ectasia. Examination findings were reviewed consisting of best-corrected spectacle distance acuity, slit lamp examination, and computerized tomography.ResultsThe study analyzed 1000 consecutive records of patients referred with a presumed diagnosis of keratoconus, pellucid marginal degeneration, and ectasia after laser vision correction that were examined between January 1, 2010 and November 1, 2016. There were 26 eyes without ectasia detected in 20 patients. The etiology of these misdiagnoses was epithelial basement membrane dystrophy (9 eyes), superficial punctate keratitis (7 eyes), amblyopia secondary to high astigmatism (3 eyes), amiodarone keratopathy (2 eyes), corneal warpage from rigid gas permeable lenses (2 eyes), corneal scars (1 eye), and measurement or alignment error with topography (2 eyes).ConclusionAnalysis of data detected a misdiagnosis of ectasia in 20 patients (26 eyes), a finding of 2.0% (20 of 1000) of referred cases that did not satisfy the diagnostic criteria of corneal ectasia. These conditions are considered a contraindication to corneal crosslinking and there is usually no benefit to topography-guided PRK or intrastromal corneal rings. It is important that clinicians recognize the clinical findings of these conditions and differentiate from true keratoconus, pellucid marginal degeneration, or ectasia after laser vision correction.     

Bilateral keratectasia after photorefractive keratectomy

PURPOSE: To report the clinical features, management, and outcome of a patient who developed bilateral ectasia after photorefractive keratectomy (PRK). METHODS: Case report of a 35-year-old man who underwent bilateral PRK. Preoperative uncorrected visual acuity was 20/200 in the right eye and 20/100 in the left eye. The patient's history was unremarkable and he denied a family history of ocular disorders. RESULTS: Two weeks after surgery, the patient presented with loss of visual acuity in both eyes. Uncorrected visual acuity was 20/80 in the right eye and 20/200 in the left eye. Objective refraction could not be obtained. Slit-lamp microscopy showed corneal thinning in both eyes. After examining the patient's family, his sister was found to have clinical and topographic keratoconus. CONCLUSIONS: Ectasia is a rare complication of PRK. We report the occurrence of bilateral ectasia after PRK in a patient with asymmetric bowtie topographies. We recommend that refractive surgery, even surface techniques such as PRK, be avoided in patients with a family history of keratoconus.     

Fellow eye treatment in excimer photo refractive keratectomy

PURPOSE: To describe symmetry of response in fellow eyes of patients undergoing photorefractive keratectomy (PRK) for myopia, analyse the risk factors leading to asymmetry in response and to determine if delayed treatment of the second eye increases safety and predictability of PRK. METHODS: Retrospective review of case records of 133 patients who underwent bilateral myopic PRK and had a minimum follow up of 6 months in both eyes. RESULTS: Postoperative uncorrected visual acuity, spherical equivalent (SE) refraction within +/- 1 D of emmetropia, best-corrected visual acuity (BCVA) and corneal haze were not significantly different in fellow eyes of patients undergoing PRK for myopia. Of 87 eyes in group 1 (myopia < 6 D), 96.6% had uncorrected visual acuity > or = 6/12, 89.7% were within +/- 1 D of emmetropia, none lost > or = 1 line BCVA, and none had haze > or = grade 3. Similar results for 98 eyes in group II (myopia 6 to 9.9 D) were 75.6%, 55.1%, 2.0% and 2.0% respectively. For 81 eyes in group III (myopia > or = 10 D) the results were 42.7%, 33.3%, 8.6%, and 4.9% respectively. Among 84 patients with similar preoperative myopia in both eyes, 54 (64.3%) patients had a postoperative SE difference < or = 1 D in fellow eyes. Risk factors for asymmetric response among fellow eyes included increasing preoperative myopia (p < 0.001) and dissimilar treatment technique in the two eyes (p = 0.03). Corneal haze did not increase significantly after the third postoperative month. CONCLUSION: This study demonstrates that considerable symmetry of response exists in fellow eyes of patients undergoing myopic PRK. Early PRK in the fellow eye of patients with < 6 D myopia is safe and allows quick visual rehabilitation of the patient. In patients with myopia > or = 6 D, a 3-month interval before treating the second eye may improve the safety of the procedure.     

Unilateral corneal ectasia after laser in situ keratomileusis in a patient with uncomplicated photorefractive keratectomy in the fellow eye

We report a patient treated for low myopia with laser in situ keratomileusis (LASIK) in one eye and photorefractive keratectomy (PRK) in the fellow eye. Corneal ectasia developed in the LASIK-treated eye. Preoperative corneal pachymetry, topography, and attempted correction were similar in both eyes. In patients whose corneas may be predisposed to instability, PRK may be a safer alternative procedure than LASIK.     

In-vivo corneal biomechanical analysis of unilateral keratoconus

AIM: To evaluate and compare corneal biomechanical findings measured by ocular response analyzer, topographic and pachymetric findings in patients with unilateral keratoconus patients and healthy controls. METHODS: This is an observational, case-control study. Patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with sex and age matched with controls healthy subjects. All subjects were evaluated with rotating scheimpflug imaging system. The receiver-operating-characteristic curves were analyzed to evaluate the sensitivity and specificity of the parameters. RESULTS: Twenty-seven patients with keratoconus in one eye and forme fruste keratoconus in the fellow eye were compared with 40 eyes of 40 normal subjects. Corneal hysteresis (CH) was 8.0±1.7 mm Hg in keratoconus group, 8.3±1.6 mm Hg in forme fruste keratoconus group, and 9.8±1.6 mm Hg in control groups (P=0.54 between keratoconus and forme fruste keratoconus groups, P<0.01 between control group and other groups). Corneal resistance factor (CRF) was 7.1±2.2 mm Hg in keratoconus group, 7.8±1.2 mm Hg in forme fruste keratoconus group and 9.9±1.5 mm Hg in control group (P<0.001 between control group and other groups). Using receiver-operating-characteristic analysis, the area under curve values of the parameters to distinguish forme fruste keratoconus from control subjects were: CH (0.768), CRF (0.866). Best cut-off points were 9.3 mm Hg and 8.8 mm Hg for CH and CRF respectively. CONCLUSION: Ocular response analyzer parameters (CH and CRF) are found to be significantly lower in forme fruste keratoconus patients compared to normal control subjects.     

Topography-controlled excimer laser photorefractive keratectomy

PURPOSE: To assess whether photorefractive keratectomy (PRK) controlled by videokeratography can successfully treat refractive errors in eyes with corneal irregularities and improve spectacle-corrected visual acuity. METHODS: In a prospective clinical study, PRK was performed in 10 eyes of 10 patients. Reason for surgery was irregular astigmatism after penetrating keratoplasty, corneal irregularity after corneal scarring, corneal astigmatism in keratoconus, and decentration after myopic and hyperopic PRK. Excimer ablation was controlled by preoperative videokeratography (Orbscan II, Orbtek) using the MEL-70 system from Aesculap Meditec. Follow-up was 6 months. RESULTS: Concerning manifest refraction, the sphere was reduced on average from +1.92 to +0.57 D, 6 months postoperatively. Cylinder changed from -1.95 D on average to -0.30 D at 6 months postoperatively. There was improvement of uncorrected visual acuity of 2 or more lines in 5 eyes and no change in 5 eyes 6 months postoperatively. Spectacle-corrected visual acuity improved in 2 eyes by 2 to 3 lines, in 9 eyes by 1 to 3 lines, and showed no change in 1 eye. CONCLUSION: Videokeratography-controlled PRK improved refractive errors in irregular corneas with improvement of spectacle-corrected visual acuity.     

Ectasia after laser in situ keratomileusis

Eighty-five cases of post laser in situ keratomileusis ectasia were reviewed and analyzed. Cases of keratoconus or forme fruste keratoconus were eliminated; many remaining case reports lacked key information. The current literature is unable to define a specific residual corneal thickness or a range of preoperative corneal thickness that would put an eye at risk for developing ectasia. The most logical cause for eyes without preexisting pathology to develop ectasia is a postablation stromal thickness that is mechanically unstable; this "minimal" thickness is probably specific to each eye. The preoperative and postoperative corneal thickness, measured flap thickness, and microkeratome and laser parameters used in a given case are required to determine the range of residual corneal thickness that puts the eye at risk for developing ectasia. Other as yet undetermined factors may play a role in the development of this complication.     

Bilateral keratectasia after unilateral laser in situ keratomileusis: a retrospective diagnosis of ectatic corneal disorder

We present a case of iatrogenic keratectasia in the left eye after laser in situ keratomileusis (LASIK) with 14 microm of stromal ablation. Preoperative evaluation did not show significant evidence of keratoconus or forme fruste keratoconus in either eye. Twenty months postoperatively, in addition to postoperative ectasia in the left eye, the right eye developed mild changes in manifest refraction and on corneal topography. A retrospective diagnosis of ectatic corneal disorder was made in a patient who had no obvious findings of corneal pathology prior to LASIK.     

Wavefront-supported photorefractive keratectomy with the Bausch & Lomb Zyoptix in patients with myopic astigmatism and suspected keratoconus

PURPOSE: To evaluate the safety, efficacy, and visual outcome of wavefront-supported photorefractive keratectomy (PRK) for the correction of myopia and myopic astigmatism in patients with suspected keratoconus. METHODS: Forty eyes of 20 patients with myopia -4.0 to -8.0 diopters (D) (mean: -6.25 +/- 1.04 D), cylinder -1.0 to -2.50 D (mean: -1.61 +/- 0.71 D), and corneal thickness 440 to 488 microm were treated with wavefront-supported PRK. Corneal topography evaluation revealed a significantly irregular cylinder (inferior-superior difference > 1.5 D) with possible mild or forme fruste keratoconus. Aberrometry was performed with the Hartmann-Shack aberrometer, and corneal data were evaluated with the Orbscan system. Eyes were treated with the Technolas 217z Bausch & Lomb excimer laser and followed for a minimum of 40 months. RESULTS: Following surgery, mean spherical equivalent refraction was +0.33 +/- 0.8 D. It was within +/- 0.5 D of the intended refraction in 95% of eyes and within +/- 1.0 D in 100% of eyes. Mean uncorrected visual acuity improved from 20/400 preoperatively to 20/25 postoperatively. Mean best spectacle-corrected visual acuity (BSCVA) remained unchanged (20/20) or improved to 20/20 in 92.5% of eyes and to 20/25 in 7.5% of eyes. Individually, BSCVA did not change in 28 (70%) eyes and increased by > or = 2 Snellen lines in 9 (22.5%) eyes; 3 (7.5%) eyes lost 1 Snellen line because of corneal haze. Laser treatment induced a significant flattening of the preoperative inferior corneal steepness in all eyes. Wavefront analysis demonstrated a significant decrease in high order aberrations (total root-mean-square and coma). CONCLUSIONS: Wavefront-supported PRK appears to be effective for the treatment of myopia and astigmatism in patients with suspected keratoconus and thin, irregular corneas. Longer follow-up is needed to prove the safety of the procedure in this patient population.     

准分子激光角膜切削术治疗圆锥角膜行角膜表层镜片术后的屈光不正

目的探讨角膜表层镜片术（EP）联合Ⅱ期准分子激光角膜切削术（PRK）治疗圆锥角膜完成期的临床疗效。方法（1）病例入选标准：①EP入选标准：圆锥角膜完成期患者,角膜中央区无瘢痕,最佳矫正视力（BCVA）≤0．3,角膜曲率≤60．0D;②Ⅱ期行PRK入选标准：角膜拆线后3个月内散光变化〈0．5D,年龄〉18岁,无其他眼部疾病。（2）手术治疗：对进入手术入选标准的患者常规Ⅰ期行EP,Ⅱ期行PRK。（3）术后随访：观察术后植片情况,记录视力、散光变化及并发症发生情况。结果8例（10只眼）患者接受了Ⅰ期EP联合Ⅱ期PRK,术后平均随访时间为40．6（30～94）个月。（1）视力：EP术后12～18个月（角膜全拆线行PRK术前）,10只眼BCVA均〉0．3,其中0．3～0．5者1只眼,≥0．5者9只眼;行PRK术后〉12个月,10只眼BCVA均≥0．5,其中5只眼BCVA达到1．0。（2）角膜散光：EP术前平均角膜散光为（7．3±1．8）D,EP术后12～18个月平均角膜散光为（3．8±1．6）D,PRK术后24个月以上,平均角膜散光为（1．6±0．9）D。（3）植片情况：EP术后所有植片透明,无免疫排斥反应发生。PRK术后1只眼发生0．5级的角膜上皮下雾状混浊,未见圆锥角膜复发。（4）术后并发症与处理：1例（1只眼）患者EP术后当天继发青光眼,前房消失,急诊行前房重建后缓解;1例（1只眼）患者EP术后植床出现较大皱褶,1例（1只眼）患者EP术后3个月内缝线松动,行植片重缝后缓解。结论Ⅰ期EP联合Ⅱ期PRK可能是治疗圆锥角膜完成期的有效方法,行PRK术后视力长期稳定。     

Iatrogenic keratoconus as a complication of radial keratotomy

A 47-year-old man with a family history of keratoconus had uneventful bilateral radial keratotomy (RK) with astigmatic keratotomy (AK) enhancements 12 years earlier. He noticed a gradual onset of blurry vision with progressively increasing myopic shift. Visual acuity remained poor even with spectacles or soft contact lenses. Slitlamp examination revealed 16 well-healed RK scars and 2 AK scars with marked corneal steepening inferiorly in an area of astigmatic enhancement in the left eye but an otherwise normal fellow eye with 16 well-healed RK scars. He subsequently had penetrating keratoplasty for decreased vision not correctable by rigid gas-permeable contact lenses. Microscopic examination of the corneal button showed findings consistent with keratoconus. This case represents the first documented incidence of corneal ectasia as a complication of primary RK.     

Hyperopic keratoconus

PURPOSE: To report three patients (four eyes) with hyperopic keratoconus. METHODS: Patients were evaluated with corneal curvature topography, ultrasonic pachymetry, and rotating Scheimpflug camera. RESULTS: One patient, without other risk factors, developed unilateral ectasia after LASIK following primary hyperopic ablation in an eye suspicious for keratoconus. Two additional hyperopic patients (three eyes) had curvature and elevation findings compatible with keratoconus. CONCLUSIONS: Although rare, keratoconus could present in hyperopia. If keratoconus is suspected, we suggest avoidance of LASIK and its potential for development of corneal ectasia.     

Aberrant corneal nerve regeneration after PRK

PURPOSE: To report a case of aberrant corneal nerve regeneration after myopic photorefractive keratectomy (PRK). METHODS: One patient underwent bilateral PRK to correct a refractive error of -5.50 D in each eye. Thirteen months after the original PRK, the left eye underwent an uncomplicated PRK reoperation to correct a regression of -1.00 D. The central corneas were examined by confocal microscopy preoperatively in both eyes, at 1 and 2 years after the original PRK in the right eye, and before and 1 and 2 years after the PRK reoperation in the left eye. RESULTS: Aberrant anterior stromal nerves with a coiled course and irregular branching pattern were identified 22 micro m deep to the most anterior keratocyte layer at 1 year after the PRK reoperation in the left eye and remained unchanged 2 years after reoperation. No abnormal stromal nerves were identified in the left eye before the reoperation or at any time in the right eye. CONCLUSION: Aberrant regeneration of corneal stromal nerves may occur after myopic PRK reoperation.     

LASEK and photorefractive keratectomy for myopia: clinical and confocal microscopy comparison

PURPOSE: To compare postoperative visual acuity and corneal morphology after laser epithelial keratomileusis (LASEK) versus photorefractive keratectomy (PRK) in the correction of low to moderate myopia. METHODS: In a double-blind, randomized clinical trial, 50 myopic patients (mean: -4.5 +/- 1.35 diopters) were randomized to receive LASEK in one eye and PRK in the fellow eye. No mitomycin C eye drops were used in this study. Patients were observed daily for 4 days, then at 1 month and every 3 months up to 1 year. Uncorrected and best-corrected visual acuity (UCVA and BSCVA), manifest refraction, corneal epithelium healing time, postoperative pain, and corneal haze were evaluated. Corneal wound healing was quantified with corneal confocal microscopy. RESULTS: Refractive error, UCVA, and BSCVA were not statistically different between eyes treated with LASEK and PRK. Corneal epithelium healing time was 2.52 +/- 0.99 days in the eyes treated with PRK and 2.29 +/- 0.52 days in the eyes treated with LASEK (P=.22). The postoperative pain score was 2.17 +/- 0.87 in the eyes treated with PRK and 2.62 +/- 0.60 (P=.02) in the eyes treated with LASEK. Corneal confocal microscopy showed fewer stromal activated keratocytes and less extracellular matrix deposition in the eyes treated with LASEK than in the eyes treated with PRK at 1 month postoperatively (P=.003). CONCLUSIONS: LASEK is an effective and safe procedure for low to moderate myopia, but it seems more painful until full corneal reepithelization. In the early postoperative period, the corneal wound healing process is significantly less intense in eyes treated with LASEK than in eyes treated with PRK. The role of LASEK in corneal wound healing modulation remains controversial.     

兔眼准分子激光近视角膜切削术后角膜膨出的研究

目的：探讨兔眼在准分子激光近视角膜切削术（Excimer laser in-situ keratomileusis,LASIK)手术后在不同的眼压下角膜膨出的程度。方法：26兔52眼随机分为对照组，LASIK手术组，单盲法，术前，术后测量角膜厚度和角膜地形图后，再将两组随机交叉分为正常眼压组，低度高眼压组，高度高眼压组，并观察1个月，用角膜地形图对实验前后的角膜形态进行分析。并应用统计学方法将手术切削量和眼压两个因素对角膜扩张的影响做双因素方差分析。结果：LASIK手术的角膜切削量，术后高眼压以及两者的交互效应对角膜抵抗力都有显著影响。较大的切削量和术后持续高眼压后的兔眼角膜地形图经分析符合圆锥角膜模式，并出现前，后弹力膜断裂的形态学改变。结论：角膜较大的切削量和术后持续的高眼压是导致兔眼LASIK术后发生圆锥角膜的重要原因。     

Photorefractive keratectomy in keratoconus suspects

PURPOSE: To compare the refractive outcome after photorefractive keratectomy (PRK) in keratoconus-suspect patients with that in patients with normal corneal topography. SETTING: Gimbel Eye Centre, Calgary, Alberta, Canada. METHOD: In a retrospective study, 3 patients (5 eyes) with unusually shaped corneal topography before surgery were selected as keratoconus suspects. Corneal topography (inferior-superior [I-S] value, central corneal power, and central power difference between both eyes), preoperative and 1 year postoperative refraction, and visual acuity in the keratoconus suspects were compared with those in a control group. RESULTS: The mean preoperative I-S value was 1.79 diopters (D) in the keratoconus-suspect eyes and 0.35 D in the control group eyes (P = .0001). The I-S value of individual corneas in the keratoconus suspects was more than 2 standard deviations above the mean in the control group except in 1 eye in which the steepened area was located in the central cornea. The central power difference between the eyes of this patient was 3.60 D, which was significantly higher than that in the control group. The refractive outcomes in the keratoconus suspects were comparable to those in the control group. CONCLUSION: In this study, the refractive outcomes after PRK in the keratoconus suspects and controls were comparable. However, further investigation with a larger sample and longer follow-up is needed.     

Photorefractive keratectomy for the correction of residual refractive error with Intacs intrastromal corneal ring segments in place

PURPOSE: To evaluate the efficacy and safety of photorefractive keratectomy (PRK) for residual refractive errors in patients who had previous insertion of intrastromal corneal ring segments (Intacs, Addition Technology, Inc.) for treatment of low myopia. SETTING: Shiley Eye Center, University of California San Diego, La Jolla, California, USA. METHODS: This retrospective case series comprised patients who had Intacs segment implantation and subsequently developed myopic regression. Eight eyes of 5 patients had PRK over the Intacs in situ for the correction of the residual refractive error. RESULTS: Six (75%) of the 8 eyes had plano refraction with 20/20 or better uncorrected visual acuity (UCVA) 1 month after PRK enhancement. Three months postoperatively, all eyes had plano refraction with 20/20 or better acuity. At the last follow-up examination (up to 2 years), all eyes had near plano vision (20/10 to 20/25). The corneal surface epithelium in all eyes healed in 3 to 5 days. One patient had subepithelial haze in both eyes, which resolved with epithelial scraping with mitomycin-C (MMC) application and a phototherapeutic keratectomy enhancement. CONCLUSIONS: This small series showed that PRK can be used to treat residual refractive error after Intacs insertion. The UCVA was 20/25 or better in all cases after PRK enhancement. The incidence of post-PRK haze in this series of patients was high; topical MMC might be used in future cases to mitigate the problem.