Analysis of deposit depth and morphology in granular corneal dystrophy type 2 using fourier domain optical coherence tomography

Contrast Sensitivity Changes after Phototherapeutic Keratectomy in Heterozygote Granular Corneal Dystrophy Type 2

Purpose: Contrast sensitivity, the ability to distinguish the relative difference in luminance of an object from its surrounding or adjacent objects, is a useful measure of visual function. In granular corneal dystrophy type 2 (GCD2), opacity of the corneal stroma causes deterioration in visual function. We compared the contrast sensitivity of GCD2 patients before and after phototherapeutic keratectomy (PTK) to evaluate the perioperative visual function in these patients.Methods: This study included 22 eyes of heterozygote GCD2 patients. The visual acuity and contrast sensitivity were measured before and after PTK. The contrast sensitivity was measured in mesopic and photopic background luminances, with glare (G) levels of 0-2 (G0, G1, and G2, respectively) and spatial frequencies at 1.5, 3, 6, 12, and 18 cycles per degree (cpd).Results: The contrast sensitivity increased after PTK at 1.5 and 3 cpd in mesopic and photopic conditions with G0-2 glare (p < 0.05). At 6 cpd, the contrast sensitivity increased in the mesopic condition with G1 glare, and in the photopic condition with G0-2 glare (p < 0.05). However, there was no change in contrast sensitivity at any glare level at 12 and 18 cpd after PTK.Conclusions: In GCD2 patients, the contrast sensitivity increased significantly after PTK. The vision of GCD2 patients, which is decreased due to corneal opacity, is improved after PTK.

Exacerbation of Granular Corneal Dystrophy Type 2 After Small Incision Lenticule Extraction

PURPOSE

To report the outcome of unilateral small incision lenticule extraction (SMILE) in a patient with granular corneal dystrophy type 2 (GCD2).

METHODS

Slit-lamp photography and Fourier domain optical coherence tomography were used to document the clinical course and appearance of the corneas in a patient with genetically determined GCD2 who underwent unilateral SMILE in the right eye.

RESULTS

Slit-lamp examination of a 23-year-old woman revealed 2 faint opacities at the surgical interface approximately 2 months after the SMILE procedure had been performed on her right eye. Nine and 3 typical GCD2 deposits located immediately beneath the Bowman layer were observed in the right and left corneas, respectively. Over time, the deposits at the interface increased in size, density, and number in the right eye. Fourier domain optical coherence tomography performed 33 months after the SMILE procedure revealed deposits at the SMILE interface that were distinct from those located immediately beneath the Bowman layer. The severity of disease exacerbation was less in this patient than what is typically observed in others who have undergone laser-assisted in situ keratomileusis or photorefractive keratectomy.

CONCLUSIONS

SMILE is contraindicated in patients with GCD2, as are other corneal refractive surgical procedures. This case highlights the importance of genetic testing before the performance of refractive corneal procedures-especially for patients with corneal opacities on preoperative slit-lamp examination or a family history of corneal disease compatible with that of a corneal dystrophy.

Rare stromal corneal dystrophic diseases in Oman: A clinical and histopathological analysis for accurate diagnosis

INTRODUCTION

Corneal dystrophy (CD) encirclements a heterogeneous group of genetically determined corneal diseases. Many features still remain unknown.

AIM

The purpose of this study was to highlight the clinical and the histopathological aspects of rare stromal CDs and to assess the clinical and the histopathological roles in their diagnosis.

PATIENTS AND METHODS

This study incorporated 10 eyes of six patients, clinically diagnosed as follows: four patients with bilateral lattice stromal CD (8 eyes) and two patients, each one eye, one with macular and the other with granular-type CD. Histopathological examination with applications of many special stains was done in four eyes (4 patients) after penetrating keratoplasty.

RESULTS

The histopathological examination was in concordance with the clinical diagnosis of three examined corneas and revealed first eye with lattice dystrophy, second eye with macular dystrophy, and third eye with granular dystrophy. The fourth examined cornea was not that in concordance with the clinical diagnosis of lattice CD as it showed mixed stromal CD patterns of granular, macular, and lattice types.

CONCLUSION

Histopathological assessment of corneal dystrophy cases, subjected to keratoplasty is recommended to avoid missing cases with mixed stromal corneal dystrophy. Also, using low magnification slit lamp alone in the clinical assessment of the corneal opacity appeared to be limited mode and thus, the imaging corneal methods such confocal microscopy and high-definition optical coherence tomography are recommended for future cases especially in cases with unclassic query diagnosis.

Long-term Clinical Outcomes of Phototherapeutic Keratectomy in Corneas With Granular Corneal Dystrophy Type 2 Exacerbated After LASIK

PURPOSE

To investigate the long-term clinical outcomes and recurrence patterns of phototherapeutic keratectomy (PTK) in patients with granular corneal dystrophy type 2 (GCD2) exacerbated after LASIK.

METHODS

Fifty-one patients (76 eyes) with GCD2 exacerbated after LASIK who underwent PTK between January 2007 and February 2017 were included. Participants underwent ophthalmic examination, including slit-lamp microscopy, corrected distance visual acuity (CDVA), slit-lamp photography, and Fourier domain optical coherence tomography at preoperative and postoperative visits. PTK was performed using VISX S4 IR (VISX, Inc., Santa Clara, CA). Visual acuity, complications, interval, and contributing factors of recurrence were evaluated.

RESULTS

The follow-up period ranged from 1 to 108 months (mean: 35.22 months). The mean logMAR CDVA was 0.55 ± 0.43 (Snellen equivalent 20/80) preoperatively and 0.09 ± 0.43 (Snellen equivalent 20/25) at 3 months postoperatively. Forty-five (61.6%) eyes developed biomicroscopic recurrence at a mean of 18.6 months after PTK; 20 (27.4%) eyes developed significant recurrence at a mean of 31.3 months after PTK. The flap removal group demonstrated better CDVA at 3 years after surgery and lower recurrence and complication rates than the flap conservation group. Multivariate analysis revealed that flap removal remarkably reduced the risk of both any sign of and significant recurrence.

CONCLUSIONS

PTK improved corneal transparency and visual acuity in patients with GCD2 exacerbated after LASIK, although GCD2 eventually recurred. PTK with flap removal was superior to PTK with flap conservation in terms of visual acuity, recurrence, and complications. [J Refract Surg. 2018;34(2):132-139.].

Retinal nerve fibre layer and ganglion cell complex thickness in patients with keratoconus

Background: Keratoconus, a corneal ectasia, is associated with corneal thinning and altered optical media. Consequently, assessment of the visual field, optic nerve head and intraocular pressure measurements may be challenging in patients with keratoconus. Few studies have investigated posterior segment variables including the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) thickness in patients with keratoconus.Aim: To investigate RNFL and GCC thickness in patients with keratoconus.Methods: A comparative quantitative research design was used. The sample consisted of 56 participants (28 with mild, moderate or severe keratoconus, and 28 controls) who accessed the optometry clinic at the University of KwaZulu-Natal. There was an equal distribution of male (n = 14) and female (n = 14) participants in the keratoconus and control groups. Most participants were black (n = 34) or Indian (n = 18). Corneal power and refractive error were assessed with the Oculus Keratograph and subjective refraction respectively. The iVue-100 optical coherence topography device was used to measure RNFL and GCC thickness. Data were analysed by descriptive and inferential statistics.Results: The mean global RNFL thickness was slightly higher in the control group than the keratoconus group for the right (106 µm vs. 99 µm) and left (103 µm vs. 98 µm) eyes but these differences were not significant (p ≥ 0.057). For all RNFL quadrants, slightly lower mean RNFL measurements were found in the keratoconus group. The mean GCC thicknesses were marginally higher (3 µm – 6 µm) in the control group.Conclusion: The RNFL and GCC thickness differences between patients with keratoconus and controls are not clinically significant. Therefore, abnormally reduced RNFL and GCC thickness measurements in patients with keratoconus warrant further investigation for other pathologies specifically glaucoma.

Association Between Visual Acuity and the Corneal Area Occupied by Granular Lesions, Linear Lesions, or Diffuse Haze in Patients With Granular Corneal Dystrophy Type 2

PURPOSE

In granular corneal dystrophy type 2 (GCD2), corneal deposits containing fragments of transforming growth factor-β-induced protein appear in sequence as granular lesions (GLs), linear lesions (LLs), and diffuse haze (DH). We aimed to investigate the association between visual acuity and age-related changes in lesion types in patients with GCD2.

METHODS

We retrospectively evaluated the medical records and slit-lamp photographs of 533 patients (1066 eyes) with genetically confirmed GCD2 (heterozygous). Deposits were classified into GLs, LLs, and DH, after which the area occupied by each lesion type was measured. The associations between visual acuity and each lesion area were also evaluated using univariable and multivariable models.

RESULTS

The area occupied by GLs increased beginning in the teen years, whereas the area occupied by DH began to increase after age 40. However, the area occupied by LLs increased until patients had reached their 40s, after which no further increases occurred. Multivariable analyses revealed no association between GLs and low visual acuity after adjusting for age and sex. Increases in the LL area were associated with lower odds for low visual acuity (adjusted odds ratio = 0.4 for the third tertile, 95% confidence interval, 0.2-0.97), whereas increases in the DH area were positively associated with low visual acuity (adjusted odds ratio = 3.3 for the third tertile of the DH area, 95% confidence interval, 1.3-8.3).

CONCLUSIONS

Our findings indicated that LLs associated with GCD2 do not produce significant decreases in visual acuity, whereas DH exerts the most significant negative impact on visual acuity. Late-onset DH may be associated with the termination of LL formation.

Outcomes of photorefractive keratectomy instead of phototherapeutic keratectomy for patients with granular corneal dystrophy type 2

PURPOSE

The purpose of this study was to evaluate visual function and postoperative refractive errors in patients with granular corneal dystrophy type 2 (GCD2) and cataracts who underwent photorefractive keratectomy (PRK) instead of phototherapeutic keratectomy (PTK) following cataract surgery to avoid PTK-induced central island formation and reduce refractive errors after cataract surgery.

METHODS

The medical records of 14 eyes from nine patients (one man and eight women; mean age, 69.0 ± 8.5 years) with GCD2 and cataracts were evaluated. All patients underwent PTK using the PRK mode 3 months after cataract surgery. We analyzed corrected distance visual acuity (CDVA), refractive errors, and corneal astigmatism derived from Fourier analysis and assessed the incidence of complications in cataract surgery and PTK.

RESULTS

The mean CDVA logMAR values were 0.42 ± 0.19, 0.38 ± 0.18, and 0.16 ± 0.12 before and after cataract surgery and after PTK, respectively. CDVA improved significantly after PTK, as compared with both before and after cataract surgery (P < 0.001). The mean absolute errors after cataract surgery and PTK were 0.53 ± 0.43 and 1.61 ± 1.01 diopters, respectively. Pre- and postoperative Fourier indices did not significantly vary in the 3-mm diameter zone, and only the asymmetry component of the 6-mm diameter zone significantly (P <0.01) increased postoperatively. No central island formation and no other marked complications were observed postoperatively in any case.

CONCLUSIONS

Performing PTK using the PRK mode following cataract surgery may be effective for patients with GCD2 and cataracts.

Characteristics of corneal dystrophies: a review from clinical, histological and genetic perspectives

Corneal dystrophy is a common type of hereditary corneal diseases. It includes many types, which have varied pathology, histology and clinical manifestations. Recently, the examination techniques of ophthalmology and gene sequencing advance greatly, which do benefit to our understanding of these diseases. However, many aspects remain still unknown. And due to the poor knowledge of these diseases, the results of the treatments are not satisfoctory. The purpose of this review was to summarize the clinical, histological and genetic characteristics of different types of corneal dystrophies.

Effect of Light Scattering and Higher-order Aberrations on Visual Performance in Eyes with Granular Corneal Dystrophy

This study was aimed to assess the relationship of intraocular forward scattering, corneal backward scattering, and corneal higher-order aberrations (HOAs) with corrected distance visual acuity (CDVA) in eyes with granular corneal dystrophy (GCD). We retrospectively examined forty two eyes of 42 consecutive patients who diagnosed GCD, and age-matched 20 eyes of 20 healthy subjects. We assessed objective scattering index (OSI) using the double-pass instrument (OQAS II, Visiometrics), corneal densitometry (CD) using the Scheimpflug rotating camera (Pentacam HR, Oculus), and corneal HOAs using the Hartmann-Shack aberrometry (KR-9000, Topcon). The OSI, CD, and corneal HOAs were significantly larger in the GCD group than those in the control group (Mann-Whitney U test, p < 0.001). We found significant correlations of logMAR CDVA with the OSI (Spearman correlation coefficient r = 0.577, p < 0.001), and with the CD (r = 0.340, p = 0.028), but no significant association with corneal HOAs (r = 0.061, p = 0.701). Intraocular forward scattering, corneal backward scattering, and corneal HOAs in eyes with GCD were higher than that in normal eyes. The CDVA was significantly correlated with intraocular forward scattering, but not with corneal HOAs in eyes with GCD, suggesting that light scattering, especially forward scattering, plays a more vital role in visual performance than corneal aberrations in eyes with GCD.

Repeatability of central and peripheral corneal thickness measurements with the iVue100 optical coherence tomographer

Background: Accurate assessment of corneal thickness is essential in corneal refractive surgery, contact lens wear and corneal pathology.Aim: To assess the repeatability (intra-observer, inter-observer and inter-session) of central (0 mm – 2 mm), mid-peripheral (2 mm – 5 mm) and peripheral (5 mm – 6 mm) corneal thickness measurements using the iVue 100 spectral domain optical coherence tomographer (SD-OCT).Setting: Optometry Eye Clinic at the University of KwaZulu-Natal (UKZN).Methods: Corneal thickness measurements were taken on 50 healthy participants by two observers independently. A second set of readings was taken by one observer on another session. Repeatability was assessed using Bland–Altman analysis, the intraclass correlation coefficient, coefficient of variation and one-way analysis of variance (ANOVA) analysis.Results: For all corneal regions, the intraclass correlation coefficients for observer one ranged from 0.942 to 0.999 and that for observer two ranged from 0.946 to 0.999, indicating good intra-observer repeatability. Using linear regression, the corneal thickness measurements were found to be comparable (within 1 µm of each other) in all regions with the exception of the nasal and temporal mid-periphery and periphery. The inter-session repeatability was based on the measurements of observer one only with the mean differences ranging from 0.02 µm to 0.63 µm. Linear regression revealed no significant differences between session 1 and session 2 (p > 0.05) except for the measurement of minimum corneal thickness.Conclusion: This study found evidence of good intra-observer, inter-observer and intersession repeatability of central, mid-peripheral and peripheral corneal measurements with the iVue 100 SD-OCT.

Determination of Surgical Strategies for Burn-Induced Conjunctivalized Corneas Using Optical Coherence Tomography

PURPOSE

To evaluate the clinical use of optical coherence tomography (OCT) in optimizing surgical treatment strategies for conjunctivalized corneas secondary to ocular burns.

METHODS

This noncomparative observational study included 25 patients with stable ocular burns and conjunctivalized corneas. OCT was performed on each eye. The thickness of corneal opacity or pseudopterygium and the underlying healthy stroma were measured. Individual surgical strategies were performed based on clinical examination and OCT images.

RESULTS

Three types of conjunctivalized corneas were evaluated, including conjunctival pannus (4 of 25), pseudopterygium (10 of 25), and a white fibrovascular membrane (11 of 25). All 25 patients received a procedure of allograft limbal stem cell transplantation. In addition, with information provided in OCT images, 8 patients had combined lamellar keratoplasties; 3 patients had deep anterior lamellar keratoplasties, and 2 patients received penetrating keratoplasties. The remaining 12 patients received limbal stem cell transplantation alone. All fibrovascular tissues were successfully removed from the cornea in all patients.

CONCLUSIONS

OCT is a valuable method in the evaluation of conjunctivalized corneas. This is helpful in determining the surgical treatments for individual patients, allowing for less corneal graft rejection and making good use of corneal donors.

Comparative Study of Anterior Eye Segment Measurements with Spectral Swept-Source and Time-Domain Optical Coherence Tomography in Eyes with Corneal Dystrophies

Purpose. To compare anterior eye segment measurements and morphology obtained with two optical coherence tomography systems (TD OCT, SS OCT) in eyes with corneal dystrophies (CDs). Methods. Fifty healthy volunteers (50 eyes) and 54 patients (96 eyes) diagnosed with CD (epithelial basement membrane dystrophy, EBMD = 12 eyes; Thiel-Behnke CD = 6 eyes; lattice CD TGFBI type = 15 eyes; granular CD type 1 = 7 eyes, granular CD type 2 = 2 eyes; macular CD = 23 eyes; and Fuchs endothelial CD = 31 eyes) were recruited for the study. Automated and manual central corneal thickness (aCCT, mCCT), anterior chamber depth (ACD), and nasal and temporal trabecular iris angle (nTIA, tTIA) were measured and compared with Bland-Altman plots. Results. Good agreement between the TD and SS OCT measurements was demonstrated for mCCT and aCCT in normal individuals and for mCCT in the CDs group. The ACD, nTIA, and tTIA measurements differed significantly in both groups. TBCD, LCD, and FECD caused increased CCT. MCD caused significant corneal thinning. FECD affected all analyzed parameters. Conclusions. Better agreement between SS OCT and TD OCT measurements was demonstrated in normal individuals compared to the CDs group. OCT provides comprehensive corneal deposits analysis and demonstrates the association of CD with CCT, ACD, and TIA measurements.

[Imaging of corneal dystrophies: Correlations between en face anterior segment OCT and in vivo confocal microscopy]

PURPOSE

To evaluate the usefulness of en face Optical Coherence Tomography (OCT) for evaluation of corneal dystrophies and to describe correlations with in vivo confocal microscopy (IVCM).

PATIENTS AND METHODS

Thirty-two eyes of 16 patients with 4 types of corneal dystrophies (epithelial basement membrane dystrophy, Fuchs dystrophy, Reis-Bücklers corneal dystrophy and Crocodile Shagreen dystrophy) were enrolled in this study. Axial and reconstructed en face scans were acquired using OCT. Images were then correlated to IVCM findings.

RESULTS

En face OCT provided new insights into the structure, size and depth of corneal tissue alterations in various corneal dystrophies. OCT en face images were well correlated with IVCM features. Despite lower resolution than IVCM, en face OCT offers the advantages of being non-invasive and allowing the analysis of larger corneal areas.

CONCLUSION

En face OCT provides useful new information in corneal dystrophies. This imaging technique will probably increase in popularity in the near future for the assessment of various anterior segment diseases.

Role of optical coherence tomography on corneal surface laser ablation

This paper focuses on reviewing the roles of optical coherence tomography (OCT) on corneal surface laser ablation procedures. OCT is an optical imaging modality that uses low-coherence interferometry to provide noninvasive cross-sectional imaging of tissue microstructure in vivo. There are two types of OCTs, each with transverse and axial spatial resolutions of a few micrometers: the time-domain and the fourier-domain OCTs. Both have been increasingly used by refractive surgeons and have specific advantages. Which of the current imaging instruments is a better choice depends on the specific application. In laser in situ keratomileusis (LASIK) and in excimer laser phototherapeutic keratectomy (PTK), OCT can be used to assess corneal characteristics and guide treatment decisions. OCT accurately measures central corneal thickness, evaluates the regularity of LASIK flaps, and quantifies flap and residual stromal bed thickness. When evaluating the ablation depth accuracy by subtracting preoperative from postoperative measurements, OCT pachymetry correlates well with laser ablation settings. In addition, OCT can be used to provide precise information on the morphology and depth of corneal pathologic abnormalities, such as corneal degenerations, dystrophies, and opacities, correlating with histopathologic findings.