Lamina Cribrosa Thickness in Patients With Keratoconus

Is Keratoconus More Than Just a Corneal Disease?

PURPOSE

The aims of this study were to compare the scleral thickness (ST), lamina cribrosa thickness (LCT), and lamina cribrosa curvature index between patients with keratoconus and healthy controls and to evaluate the relationship between these values and corneal parameters.

METHODS

This cross-sectional study included 41 eyes of 41 patients with keratoconus and 30 eyes of 30 age-matched, sex-matched, and axial length-matched controls. Nasal and temporal STs were measured vertically, 4 mm posterior to the scleral spur, using anterior segment optical coherence tomography. The LCT was measured on the radial scans of the optic nerve head. The lamina cribrosa curvature index (lamina cribrosa curvature depth/curvature width × 100) was calculated to determine the degree of posterior bowing of the lamina cribrosa.

RESULTS

The nasal ST and temporal ST were significantly lower in the keratoconus group than in the control group ( P = 0.016 and P = 0.023, respectively). The LCT was significantly lower in the keratoconus group compared with the control group ( P < 0.001). There was no significant difference between the groups for the lamina cribrosa curvature index ( P = 0.375). Correlation analysis revealed a significant correlation between the nasal and temporal STs and the central corneal thickness (r = 0.376, P < 0.001 and r = 0.387, P < 0.001, respectively). There was also a significant correlation between the temporal ST and the minimum corneal thickness in the keratoconus group (r = 0.332, P = 0.015). The LCT was significantly correlated with the central corneal thickness (r = 0.445, P < 0.001).

CONCLUSIONS

Structural features of the cornea, sclera, and lamina cribrosa with similar collagen content may be similarly affected in patients with keratoconus. Further histologic studies are needed to confirm our results.

New Findings in Early-Stage Keratoconus: Lamina Cribrosa Curvature, Retinal Nerve Fiber Layer Thickness, and Vascular Perfusion

PURPOSE

Our aim was to investigate the involvement of posterior pole structures in eyes affected by keratoconus (KC). Optical coherence tomography (OCT) and OCT angiography (OCTA) were used to determine the status of lamina cribrosa (LC), peripapillary retinal nerve fiber layer (RNFL), macular and peripapillary microvasculature.

DESIGN

Observational, cross-sectional, case-control analysis.

METHODS

Single-center investigation involving patients with KC and healthy control subjects. Enrolled subjects underwent anterior segment OCT combined with Placido-disk topography, macular and optic nerve head swept-source OCT and swept-source OCTA scans, and 3D wide glaucoma module for peripapillary RNFL thickness measurement. The LC curvature index was used to express the degree of LC posterior bowing. We calculated the vessel density and vessel length density at the macular superficial capillary plexus, deep capillary plexus, choriocapillaris, and nerve radial peripapillary capillary plexus.

RESULTS

Overall, 32 eyes with KC and an equal number of age- and axial length-matched control eyes were included in the analysis. Almost all (97%) of eyes with KC were classified as early stage. KC displayed a reduction in peripapillary RNFL thickness (104.8 ± 11.9 µm vs 110.7 ± 10.5 µm; P = .039) and nerve radial peripapillary capillary plexus vessel density (46.31% ± 3% vs 43.82% ± 4%; P = .006) when compared with control subjects; these differences were more evident in the temporal sector and were associated with a higher LC curvature index (9.9% ± 2.6% vs 8.48% ± 1.7%; P = .012). Mean macular superficial capillary plexus vessel density was 3 percentage points lower in eyes with KC than in healthy controls (P < .001).

CONCLUSION

Early-stage KC may be characterized by a posterior bowing of the LC along with a subtle peripapillary RNFL thinning and vascular impairment. These findings support the hypothesis that KC may be a corneal manifestation of a more generalized "eye collagen disease."

Evaluation of the optic nerve head and macular vessel density in keratoconus patients using optical coherence tomography angiography- a cross-sectional study

PURPOSE

Our study evaluated macular and optic disc vascular density (VD) changes in patients diagnosed with keratoconus, as compared with gender and age-matched healthy controls, in relation to the keratoconus stage.

METHODS

This comparative cross-sectional study included adult patients who received a diagnosis of keratoconus at the Cornea Clinic. All scans consisted of two 4.5 mm × 4.5 mm images of the optic disc area and 6 × 6 mm images of the macular area using optical coherence tomography angiography.

RESULTS

The study included 67 patients (26 women (38.8%) and 41 men (61.2%)) and 74 controls (31 women (41.9%) and 43 men (58.1%)). The mean ages of the keratoconus group and the control group were 30.0 ± 8.0 and 31.1 ± 7.5, respectively. Macular VD (whole, superficial, and deep) and peripapillary VD (whole) values were decreased statistically significant compared with the control group (p < 0.01 and p = 0.015, respectively). The keratoconus stage was negatively correlated with both the macular VD (p = 0.048, r = -0.314) and whole-peripapillary VD values (p = 0.03, r = -0.34).

CONCLUSION

Keratoconus might affect the posterior and anterior segments due to similar etiologies, including diminished collagen quality. Therefore, examination of the posterior segment should be performed thoroughly in keratoconus patients.

Evaluation of Lamina Cribrosa by Using Enhanced Depth Imaging Optical Coherence Tomography in Ocular Sarcoidosis during Quiescent Phase

SIGNIFICANCE

Enhanced depth imaging optical coherence tomography is a useful method to allow for the evaluation of deep ocular structures, such as choroid and lamina cribrosa (LC), which are affected by ocular diseases. We hypothesized that choroidal and optic nerve inflammation in patients with ocular sarcoidosis (OS) might affect the LC structure.

PURPOSE

This study aimed to evaluate changes in the LC and anterior LC depth (ALCD) in patients with OS.

METHODS

Forty-eight eyes of 26 patients with OS who received the treatment of panuveitis and were in the quiescent phase for at least 6 months were included in the study. Thirty healthy subjects' randomly selected eyes were selected as a control group. Eyes with OS were divided into two subgroups according to the presence (OS eyes with glaucoma [OSWG], n = 23) or absence of glaucoma (OS eyes without glaucoma [OSWOG], n = 25). The LC thickness, ALCD, and peripapillary choroidal thickness were measured using enhanced depth imaging optical coherence tomography in eyes with OS and in controls.

RESULTS

The mean LC thickness was found significantly thinner in both OSWG and OSWOG eyes compared with the healthy controls (P < .001 and P = .001, respectively). The mean ALCD was found significantly higher in OSWG eyes (462 ± 65 μm) compared with OSWOG eyes (417 ± 58 μm) and the healthy control eyes (397 ± 59 μm; P = .03 and P = .001, respectively). The average peripapillary choroidal thickness was found to be significantly thinner in OSWG eyes compared with the control eyes (P = .05).

CONCLUSIONS

The present study revealed that OS is associated with a thinned LC independent of the presence of glaucoma. The degenerative changes in the LC, which is the transition point of the retinal nerve fibers, may cause long-term visual dysfunction in OS. These degenerative changes should be prevented by controlling inflammation with early diagnosis and treatment in patients with OS.

The Relationship Between Keratoconus Stage and the Thickness of the Retinal Layers

Objectives

To examine the relationship between keratoconus (KC) stage and the thickness of the retinal layers.

Materials and Methods

Retinal layer thicknesses were compared between 85 eyes of 85 KC patients and 40 eyes of 40 controls similar in age, sex, and axial length. KC patients were staged as stage 1, 2, or 3 according to the Amsler-Krumeich staging system, and segmentation of the retinal layers was performed with spectral domain optical coherence tomography automatic segmentation program. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), and retinal pigment epithelium (RPE) in the central 1 mm Early Treatment Diabetic Retinopathy Study subfield was analyzed.

Results

There was no significant difference between the control and KC groups in the segmentation of the RNFL, GCL, IPL, or OPL (p=0.306; p=0.661; p=0.893, p=0.664, respectively). The INL differed significantly between control and stage 2 KC, control and stage 3 KC, stage 1 and 2 KC, and stage 2 and 3 KC, increasing in thickness with higher stage (p=0.004; p=0.005: p=0.001; p=0.002, respectively). The RPE also differed significantly between control and stage 2 KC, control and stage 3 KC, stage 1 and 2 KC, and stage 2 and 3 KC, showing decreased thickness with higher stage (p=0.03; p=0.001; p=0.001; p<0.001, respectively). The ONL also thinned as stage increased, but the results were not statistically significant (p=0.051).

Conclusion

More advanced KC stage was associated with increased thickness of the INL layer, where the neuroglial cell bodies are located, and decreased thickness in the outer retinal layers, especially the RPE.

Optical Coherence Tomography Imaging of the Lamina Cribrosa: Structural Biomarkers in Nonglaucomatous Diseases

The lamina cribrosa (LC) is an active structure that responds to the strain by changing its morphology. Abnormal changes in LC morphology are usually associated with, and indicative of, certain pathologies such as glaucoma, intraocular hypertension, and myopia. Recent developments in optical coherence tomography (OCT) have enabled detailed in vivo studies about the architectural characteristics of the LC. Structural characteristics of the LC have been widely explored in glaucoma management. However, information about which LC biomarkers could be useful for the diagnosis, and follow-up, of other diseases besides glaucoma is scarce. Hence, this literature review aims to summarize the role of the LC in nonophthalmic and ophthalmic diseases other than glaucoma. PubMed was used to perform a systematic review on the LC features that can be extracted from OCT images. All imaging features are presented and discussed in terms of their importance and applicability in clinical practice. A total of 56 studies were included in this review. Overall, LC depth (LCD) and thickness (LCT) have been the most studied features, appearing in 75% and 45% of the included studies, respectively. These biomarkers were followed by the prelaminar tissue thickness (21%), LC curvature index (5.4%), LC global shape index (3.6%), LC defects (3.6%), and LC strains/deformations (1.8%). Overall, the disease groups showed a thinner LC (smaller LCT) and a deeper ONH cup (larger LCD), with some exceptions. A large variability between approaches used to compute LC biomarkers has been observed, highlighting the importance of having automated and standardized methodologies in LC analysis. Moreover, further studies are needed to identify the pathologies where LC features have a diagnostic and/or prognostic value.

Posterior pole retinal thickness distribution pattern in keratoconus

PURPOSE

To evaluate the pattern of retinal thickness distribution in patients with keratoconus (KCN) and its correlation with disease severity.

METHODS

For this cross-sectional cohort study, the study subjects with documented keratoconus and normal eyes were prospectively enrolled. All subjects had anterior segment (Pentacam HR) and posterior segment (Spectralis) imaging. Posterior segment imaging by optical coherence tomography included the posterior pole asymmetry analysis map. Data were analyzed with multiple linear regression models and correlation tests to examine the mean and variance of the measured thickness of the retina and its distribution relative to the presence and severity of KCN.

RESULTS

A total of 24 subjects with keratoconus (48 eyes) and 14 normal subjects (28 eyes) enrolled in this study. The posterior pole retinal thickness, both superior and inferior hemifields, as well as the overall retinal thickness in KCN patients was greater than the control group. There was a direct correlation between the overall retinal thickness of the posterior pole and the severity of KCN (R² = 0.422, P < 0.001). However, the variability of the retinal thickness showed no difference between KCN-afflicted and healthy eyes.

CONCLUSION

Although KCN is a disease of the anterior segment of the eye, we found an orderly increase in posterior pole retinal thickness that is correlated with the severity of disease in KCN eyes compared to control. These findings suggest that the retina may maintain some degree of plasticity to respond to the degraded optical system of the eye.

Intra-ocular pressure variation associated with the wear of scleral lenses of different diameters

PURPOSE

To evaluate the variation of intra-ocular pressure during scleral lens wear, and the influence of the lens diameter on the results.

METHODS

This is a prospective, randomized study performed on Caucasian subjects (16 F; 5 M), aged 24.7 + 4.1 y.o. A diurnal variation pattern (IOPg) was established, then, transpalpebral IOP (IOPt) was taken before and during SL wear. One eye, randomly fitted with a 15.8 diameter SL (L1), was compared to the fellow eye, fitted with an 18 mm SL of the same design, thickness and material (L2). Anterior segment tomography was taken pre-and after lens removal.

RESULTS

Baseline IOPg (L1:15.2 + 3.1 mm HG; L2: 15.1 +/- 2.8 mm) did not reveal significant diurnal variations. Wearing L1, IOPt rose from 10.1 + 1.9 mm HG to 14.4 + 5.5 mm HG after 4.5 + 0.3 hrs, while with L2, it rose from 9.2 + 2.1 mm HG to 14.4 + 4.8 mm Hg. This difference is statistically significant based on time but not on lenses. Anterior segment parameters did not vary except for the anterior chamber volume (L1: -1.53 + 7.61 mm³; L2: -3.47 + 6.4 mm³), and for the corneal thickness (+2.1% with L1 and L2).

CONCLUSION

These results suggest that, as evaluated with a non-standard transpalpebral methodology, IOP during scleral lens wear may be increased in average by 5 mm Hg, regardless of the lens diameter. More work is needed to confirm if practitioners should be warned when using SL on populations at risk for glaucoma.