Apparent cleavage of the retinal nerve fiber layer in asymptomatic eyes with high myopia

Progression of Glaucoma in Highly Myopic Eyes with Paravascular Inner Retinal Defects

Purpose: To report a case of glaucoma progression in highly myopic eyes with paravascular inner retinal defects.Case summary: Retinal nerve fiber layer (RNFL) defects with cleavage-like irregular margins and internal areas were found around the retinal vessels in highly myopic eyes of a 17-year-old female. On suspicion of paravascular inner retinal defect (PIRD) instead of glaucomatous RNFL defect, observation without treatment was recommended. After 10 years of follow-up, RNFL defects and neuroretinal rim thinning were found around the pre-existing PIRD on fundus photographs. Optical coherence tomography also revealed decreased RNFL thickness.Conclusions: Glaucomatous changes progressed around the pre-existing PIRD area over the 10-year follow-up. This indicates the need for caution when assessing glaucoma in highly myopic eyes with PIRD.

Anatomical and functional changes in paravascular abnormalities after epiretinal membrane removal

PURPOSE

To investigate the anatomical and functional changes in areas containing paravascular abnormalities (PVA) in eyes with epiretinal membrane (ERM) after surgery.

METHODS

Twenty-eight eyes with concurrent idiopathic ERM and PVA were enrolled in this prospective study. Best-corrected visual acuity (BCVA), central macular thickness (CMT), and areas of PVA in the superficial and deep capillary levels detected on en face optical coherence tomography were measured preoperatively and 1, 3, and 6 months postoperatively. Retinal sensitivity in selected PVA lesions was evaluated by microperimetry preoperatively and 1 and 6 months postoperatively.

RESULTS

The areas of PVA at the superficial capillary level before and 1, 3, and 6 months after surgery measured 1.65 ± 1.27, 0.44 ± 0.62, 0.40 ± 0.64, and 0.38 ± 0.62 mm², respectively, while those at the deep capillary level measured 0.27 ± 0.57, 0.10 ± 0.26, 0.09 ± 0.29, and 0.05 ± 0.15 mm², respectively. The areas of PVA in the superficial and deep capillary levels were significantly smaller postoperatively (all p < 0.001 at the superficial capillary level and p = 0.010 at the deep capillary level). Average retinal sensitivity values in the PVA lesions before and 1 and 6 months after surgery were 11.2 ± 3.5, 12.9 ± 3.2, and 13.2 ± 2.7 dB, respectively; the values at postoperative months 1 and 6 were significantly improved (p = 0.045 and p < 0.001, respectively). BCVA and CMT were significantly improved postoperatively.

CONCLUSION

PVA not only improves anatomically but also functionally after ERM surgery. Vitrectomy can improve not only central vision but also retinal sensitivity in areas of PVA.

An Examination of the Frequency of Paravascular Defects and Epiretinal Membranes in Eyes With Early Glaucoma Using En-face Slab OCT Images

PURPOSE

To examine the frequency of paravascular defects (PDs) and macular epiretinal membranes (ERMs) in eyes categorized as having mild glaucoma or glaucoma suspect using en-face slab analysis of optical coherence tomography (OCT) scans.

MATERIALS AND METHODS

Fifty-seven glaucomatous eyes, 44 low-risk suspect eyes, and 101 healthy control eyes were included in the study. The 101 glaucomatous and suspect eyes had a mean deviation better than -6 dB on the 24-2 visual field, and a spherical refractive error between±6 D or axial length <26.5 mm. Two OCT-graders masked to eye classification identified ERMs and PDs on en-face slab images of the macula and peripapillary retina using horizontal B-scans and derived vertical B-scans.

RESULTS

Glaucomatous eyes had a significantly higher number of PDs and ERMs than healthy controls (PD, P<0.001; ERM, P=0.046) and low-risk glaucoma suspects (PD, P=0.004; ERM, P=0.043). PDs and/or ERMs were present in 16 of 57 (28.1%) glaucomatous eyes, 2 of 44 (4.5%) suspect eyes, and 3 of 101 (3.0%) control eyes. Further, PDs were present in 11 of the 57 (19.3%) glaucomatous eyes, 1 of the 44 (2.3%) suspect eyes and 0 of the 101 (0%) control eyes, ERMs were seen in 7 of the 57 (12.3%) glaucomatous eyes, 1 of the 44 (2.3%) suspects, and 3 of the 101 (3.0%) control eyes.

CONCLUSIONS

Eyes with early glaucoma have a higher frequency of PDs and ERMs than suspects or controls and exhibit PDs even in the absence of ERMs or high myopia.

Long-term follow-up of retinal nerve fiber layer cleavages in glaucoma patients and suspects

PURPOSE

To investigate the structural and functional characteristics and change of the retinal nerve fiber layer cleavages (RNFLCs) in glaucoma patients and suspects in long-term follow-up.

METHODS

This is a retrospective longitudinal study. Within 43 eyes of 30 subjects, 62 RNFLC locations were detected on color fundus photography. Basic ophthalmic examinations, color fundus photography, optical coherence tomography (OCT), and visual field (VF) test were performed in 6-month intervals. Clinical characteristics and the structural and functional changes of the cleaved areas were analyzed.

RESULTS

RNFLC and localized vitreoretinal traction occurred most commonly along the superotemporal retinal vessel arcade. Nine locations had corresponding defects on OCT deviation map, while 31 locations were associated with defects on OCT deviation map. Three locations had corresponding VF defects. More of the non-highly myopic eyes had lamellar hole than the highly myopes (p = 0.038). The RNFLC lesions in glaucomatous eyes were more frequently associated with OCT defects on deviation map (p = 0.021). There was no difference in the presence of lamellar hole or the number of RNFLCs between the glaucomatous and non-glaucomatous eyes. During a 66.8 ± 37.8-month follow-up, there was no structural or functional progression of the RNFLCs as determined by color fundus photography, VF test, and GPA of OCT interpreted by three ophthalmologists. There was no statistically significant change of RNFLC area (p = 0.268).

CONCLUSIONS

RNFLC did not show detectable functional or structural change in early glaucoma patients and suspects after long-term follow-up.

Paravascular inner retinal abnormalities in healthy eyes

PURPOSE

To investigate the prevalence and characteristics of paravascular inner retinal abnormalities in healthy eyes.

MATERIALS AND METHODS

In this prospective observational case series, we included 178 healthy eyes (178 patients) with no ocular diseases. Eyes with co-existing ocular diseases, e.g., epiretinal membrane, glaucoma, or high myopia, were excluded from the current study. The posterior pole and paravascular areas of the temporal arcade vessels were comprehensively examined by dense radial scanning of optical coherence tomography (OCT) with the extended field imaging technique.

RESULTS

On fundus photography, no inner retinal abnormalities were detected along the temporal arcade vessels. On OCT sections, paravascular inner retinal abnormalities were seen in 77 (43.3%) eyes. In 71 (39.9%) eyes, inner retinal cystoid or fissure-like spaces that had no connection to the vitreous cavity were seen adjacent to the temporal arcade vessels. Most of these lesions were detected only on several consecutive OCT sections. In four (2.2%) eyes, inner retinal cleavages with openings to the vitreous cavity were seen adjacent to the temporal arcade vessels. These lesions were more frequently detected in the inferior hemisphere and along the major retinal veins. No eyes showed typical broad defects of the inner retinal tissue. There were no significant differences in age, gender, visual acuity, refractive error, or axial length between eyes with or without paravascular inner retinal abnormalities.

CONCLUSIONS

Paravascular cystoid or fissure-like spaces were frequently seen in the inner retina of healthy eyes. However, we detected no typical paravascular inner retinal defects in healthy eyes.

Myopia and diabetes mellitus as modificatory factors of glaucomatous optic neuropathy

Myopic deformation of the eye and metabolic alterations of the nerve tissue of patients with diabetes may modify glaucomatous optic neuropathy (GON). Blockage of axonal transport of neurotrophic factors (NTFs) is the event crucial to understanding the factors that affect GON. The primary, but not sole, blockage site is at the lamina cribrosa (LC). Other than this primary site of damage at the LC, 7 other factors may explain atypical nerve fiber layer (NFL) defects and the vulnerability of the nerve fibers in eyes with high myopia and glaucoma: a second point of blockage at the edge of the posterior scleral foramen; ectatic strain on the NFL; ectasia and distortion of the LC; association of a hypoplastic optic disc; thin and weak collagen fibers; peripapillary chorioretinal atrophy; and myopic neuropathy. Among diabetic patients, diabetic neuropathy in the retinal NFL is present initially, and increased resistance to aqueous outflow leads to ocular hypertension. Superimposition of GON on diabetic neuropathy and ocular hypertension in patients with diabetes may enhance their susceptibility to nerve damage. Results of a meta-analysis study suggested a positive association between diabetes mellitus and glaucoma whereas other reports suggested that leakage of vascular endothelial growth factor, a survival mechanism of ischemic neural tissue, and enhanced stiffness of the LC as a result of diabetic glycation may protect neurons from apoptosis. Thus, modification of GON as a result of diabetes remains controversial.

Early and late inner retinal changes after inner limiting membrane peeling

Pars plana vitrectomy and inner limiting membrane (ILM) peeling are standard procedures for macular hole and epiretinal membrane surgery. However, ILM peeling is known to cause mechanical traumatic changes to the retinal nerve fiber layer. Recently there have been numerous reports of anatomical changes in the macula after ILM removal. A comprehensive review of the literature. The earliest change in the macula after ILM peeling is post-operative swelling of the arcuate retinal nerve fiber layer (SANFL), which disappears within the 3 month; the swelling is not detected on biomicroscopic fundus examination but appears as hypoautofluorescent arcuate striae in the macular region on infrared and autofluorescence imaging, with corresponding hyperreflectant swelling demonstrated on spectral-domain optical coherence tomography (OCT). SANFL is followed by dissociated optic nerve fiber layer defect, faintly visible on fundus examination and corresponding on OCT to "dimples" in the inner retinal layers. The en face tomographic aspect of this defect appears as concentric macular dark spots. Post-operative foveal displacement toward the optic disc might be responsible for the stretching and thinning of the retinal parenchyma in the temporal subfield and the thickening of the nasal macula. This shortening of the papillofoveal distance after surgery is probably secondary to axonal transport and contractility alterations in the nerve fiber layer, which might also account for apoptotic and atrophic degeneration of the peripapillary retinal nerve fiber layer. Ganglion cells do not seem to be affected by ILM peeling, even if the ganglion cell complex loses some volume because of trauma to the Müller cells contained in the ganglion cell layer. Despite its clear indication in macular hole and epiretinal membrane surgery, ILM peeling is a traumatic procedure that has acute effects on the underlying inner retinal layers. Further investigation of these subclinical changes may assist in aiding the development of minimally traumatic techniques for ILM removal.

"Dissociated optic nerve fiber layer appearance" after internal limiting membrane removal is inner retinal dimpling

PURPOSE

To examine volume-rendered spectral-domain optical coherence tomography images in patients who had undergone vitrectomy, many of whom had internal limiting membrane removal to investigate a condition termed "dissociated optic nerve fiber layer appearance."

METHODS

Patients who had undergone vitrectomy for either macular hole or epiretinal membrane were evaluated. Spectral-domain optical coherence tomography B-scan images were acquired with the use of eye tracking at an interval of either 30 μm or 60 μm. These were registered and exported to a volume-rendering program, and the resultant volume-rendered images were evaluated. The images were graded for the presence of inner retinal abnormalities, and correlates were made to corresponding alterations seen in fundus photographs and B-scan spectral-domain optical coherence tomography images.

RESULTS

There were 25 eyes of 24 patients with a mean age of 72.4 (± 7.3) years, 15 of whom were women. The primary preoperative diagnosis was macular hole in 10 eyes (40%) and epiretinal membrane in 15 eyes (60%). As part of the surgery, 18 eyes (72%) had planned peeling of the internal limiting membrane. Volume rendering showed that 13 eyes had pitting or dimples of the inner retinal surface that seemed to follow the course of the nerve fiber layer in the region of the macula. The inner retinal dimples occurred only in eyes that had internal limiting membrane peeling. Correlation of the volume-rendered images with B-scan spectral-domain optical coherence tomography showed focal areas of thinning of the ganglion cell layer with decreased reflectivity from the nerve fiber layer in the areas of the dimples.

CONCLUSION

A high proportion of eyes with internal limiting membrane peeling develop inner retinal dimples that course along the path of the nerve fiber layer. The dimples seem to be the result of an interplay between trauma and healing processes constrained by nerve fiber layer and do not appear to be because of dissociation of optic nerve fibers. The true nature of the abnormalities induced should be investigated to evaluate the long-term risks and benefits of routine internal limiting membrane peeling.

Inner retinal cleavage associated with idiopathic epiretinal membrane

PURPOSE

To report a case of inner retinal cleavages that disappeared after idiopathic epiretinal membranes were removed.

METHODS

A 72-year-old woman with epiretinal membranes and inner retinal cleavages in her nonmyopic eye underwent pars plana vitrectomy and epiretinal membrane removal. Fundus examination and optical coherence tomography were performed before and after surgery.

RESULTS

Inner retinal cleavages disappeared after epiretinal membranes were removed.

CONCLUSION

We postulate that the inner retinal cleavages are associated with tangential retinal tractions.

Detection of Paravascular Lamellar Holes and Other Paravascular Abnormalities by Optical Coherence Tomography in Eyes with High Myopia

OBJECTIVE

To investigate the morphologic alterations at or around the blood vessels of the retinal vascular arcade by optical coherence tomography (OCT) in highly myopic eyes.

DESIGN

Observational case series.

PARTICIPANTS

Two hundred eighty-seven eyes of 149 patients with high myopia (refractive error >/=-8.00 diopters [D] or axial length >26.5 mm) were studied. Fifty-six emmetropic (+1.00 to -1.00 D) eyes and 44 eyes with low (<-6.00 D) myopia were examined as controls.

METHODS

The participants had a complete ophthalmologic examination, including stereoscopic fundus observations and OCT examinations. Multiple OCT scans were made along the entire extent of the posterior vascular arcade and across the fovea in each patient.

MAIN OUTCOME MEASURES

The incidence of paravascular retinal cysts, vascular microfolds, and paravascular retinal holes was determined. Retinoschisis at the retinal vessels and a macular retinoschisis were also evaluated.

RESULTS

In 287 eyes with high myopia, paravascular retinal cysts were detected in 142 eyes (49.5%), vascular microfolds in 128 eyes (44.6%), and paravascular retinal holes in 77 eyes (26.8%) by OCT. The paravascular retinal holes were partial-thickness lamellar holes in all of the patients; full-thickness holes were never detected. Vascular microfolds and paravascular lamellar holes were always accompanied by paravascular retinal cysts. Optical coherence tomography examinations revealed the presence of vitreoretinal traction on the inner walls of retinal cysts in sections adjacent to the retinal holes. In the 77 eyes with paravascular lamellar holes, 34 eyes (44.2%) were associated with internal limiting membrane (ILM) detachments and 15 eyes (19.5%) were associated with a macular retinoschisis. In fact, 15 of 18 eyes (83.3%) with a macular retinoschisis had paravascular lamellar holes. None of the 100 control eyes had these paravascular abnormalities.

CONCLUSIONS

These findings indicate that different types of paravascular abnormalities are relatively common in highly myopic eyes. Our findings suggest that paravascular lamellar holes form when the inner wall of paravascular retinal cysts is avulsed by vitreous traction. The presence of paravascular lamellar holes might enhance the proliferative response of the ILM, and this might be an important causative factor for the development of a macular retinoschisis in highly myopic eyes.

Scanning laser polarimetry in myopic and hyperopic subjects

PURPOSE

To investigate the effect of refraction error and axial length on retinal nerve fiber layer (RNFL) measurements as obtained by scanning laser polarimetry (SLP).

METHODS

Besides ophthalmological standard examination (refractive error, keratometry, visual acuity, slit-lamp examination, applanation tonometry, funduscopy), perimetry, axial length measurement by means of ultrasound, and SLP were performed. Seventy-five myopic eyes (between -0.75 D and -8.5 D), 24 hyperopic eyes (0.75 D-6.5 D) and 40 emmetropic eyes were investigated. SLP parameters were compared in the different groups.

RESULTS

The statistical analysis of the absolute thickness values of SLP revealed highly significant ( P< 0.01) reductions in average thickness, ellipse average, superior average, inferior average, and superior integral in both myopic and hyperopic eyes in comparison with the emmetropic control eyes. The amount of reduction was between 12.9% (inferior average; myopia) and 30.2% (superior integral; hyperopia). There were no significant differences between myopes and hyperopes. A significant linear correlation for many of the SLP parameters with the refractive error (spherical equivalent) but not with axial length was found in both the hyperopic and the myopic group.

CONCLUSIONS

Despite a wide interindividual range, SLP measurement values decrease with increasing myopia and hyperopia. In clinical practice, such reduced RNFL thickness values should be viewed with the necessary caution and additional polarimetric signs for glaucomatous damage should be taken into consideration.

Scanning laser polarimetry in normal subjects and patients with myopia

AIMS

To examine the changes in the retinal nerve fibre layer (NFL) thickness with age and myopia in normal population.

METHODS

Retinal nerve fibre layer thickness was measured with a scanning laser polarimeter (NFA-I) in 180 normal subjects of varying age (range 7-83 years) and in 110 eyes of 85 patients with myopia of varying degrees (range -1.00 to -15.00D). They were all voluntary Anatolian people. Superior to nasal (S/N), inferior to nasal (I/N), and the superior to inferior (S/I) ratios were used for the assessment of retinal NFL thickness.

RESULTS

The mean superior NFL ratio was 2.96 and the mean inferior NFL ratio was 2.93 in normal subjects. There was a gradual decrease in NFL ratio with increasing age (simple regression analysis, p<0.05). The mean S/I ratio was 1.01 with a large variation. In patients with myopia, the mean superior NFL ratio was 2.60 and the mean inferior NFL ratio was 2.72. Superior and inferior NFL retardations, and S/I ratio in myopic patients were significantly (15.5%, 10.8%, and 4.9% respectively) lower than that of age matched normals (t test, p<0.05). There was also a gradual decrease in NFL thickness with increasing degree of myopia (simple regression analysis, p<0.05).

CONCLUSIONS

Nomograms we obtained for retinal NFL thickness may serve as reference points for the assessment of normal Anatolian people and myopic patients in future studies. NFL thicknesses gradually decreased with increasing age. Patients with myopia had significantly lower NFL thicknesses than normal subjects and, although weakened by wide age range of myopic group, there is a linear relation between severity of myopia and NFL thickness in myopic patients.

Diagnosis and pathogenesis of glaucomatous optic neuropathy: morphological aspects

Glaucomatous optic neuropathy is classified by morphologic changes in the intrapapillary and parapapillary region of the optic nerve head and the retinal nerve fibre layer. These changes can be evaluated using descriptive optic nerve head variables which are the size and shape of the optic disc; size, shape and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disc; configuration and depth of the optic cup; cup-to-disc diameter ratio and cup-to-disc area ratio; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped haemorrhages; occurrence, size, configuration and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fibre layer. Assessment of these variables is useful for the early detection of glaucomatous optic nerve damage, to follow-up patients with glaucoma, to differentiate various types of the chronic open-angle glaucomas, and to get hints for the pathogenesis of glaucomatous optic nerve fibre loss.

Ophthalmoscopic evaluation of the optic nerve head

Optic nerve diseases, such as the glaucomas, lead to changes in the intrapapillary and parapapillary region of the optic nerve head. These changes can be described by the following variables: size and shape of the optic disk; size, shape, and pallor of the neuroretinal rim; size of the optic cup in relation to the area of the disk; configuration and depth of the optic cup; ratios of cup-to-disk diameter and cup-to-disk area; position of the exit of the central retinal vessel trunk on the lamina cribrosa surface; presence and location of splinter-shaped hemorrhages; occurrence, size, configuration, and location of parapapillary chorioretinal atrophy; diffuse and/or focal decrease of the diameter of the retinal arterioles; and visibility of the retinal nerve fiber layer (RNFL). These variables can be assessed semiquantitively by ophthalmoscopy without applying sophisticated techniques. For the early detection of glaucomatous optic nerve damage in ocular hypertensive eyes before the development of visual field loss, the most important variables are neuroretinal rim shape, optic cup size in relation to optic disk size, diffusely or segmentally decreased visibility of the RNFL, occurrence of localized RNFL defects, and presence of disk hemorrhages.

Evaluation of the retinal nerve fiber layer

In normal eyes, the retinal nerve fiber layer (RNFL) is usually best visible in the inferior temporal part of the fundus, followed by the superior temporal region, the nasal superior region and the nasal inferior region. This distribution correlates with the configuration of the neuroretinal rim, the diameter of the retinal arterioles, the location of the foveola, and the lamina cribrosa morphology. With increasing age, the RNFL visibility decreases diffusely without preferring special fundus regions and without the development of localized defects. With all optic nerve diseases, the visibility of the RNFL is decreased in addition to the age-related loss, in a diffuse and/or a localized manner. The localized defects are wedge-shaped and not spindle-like defects, running toward or touching the optic disk border. Typically occurring in about 20% of all glaucoma eyes, they can be found also in other ocular diseases, such as optic disk drusen, toxoplasmotic retinochoroidal scars, longstanding papilledema or optic neuritis due to multiple sclerosis. Since they are not present in normal eyes, they almost always signify an abnormality. RNFL evaluation is especially helpful for early glaucoma diagnosis and in glaucoma eyes with small optic disks. In advanced optic nerve atrophy, other examination techniques, such as perimetry, may be more helpful for following optic nerve damage. Considering its great importance in the assessment of optic nerve anomalies and diseases and taking into account the feasibility of its ophthalmoscopic evaluation using green light, the retinal nerve fiber layer should be examined during any routine ophthalmoscopy.

Evaluation of the peripapillary circulation in healthy and glaucoma eyes with scanning laser Doppler flowmetry

In order to study peripapillary perfusion, one randomly selected eye of 34 of healthy volunteers and 40 glaucoma patients (27 suffering from primary open-angle glaucoma (POAG) 10 from normal pressure glaucoma (NPG) nd three from other types of glaucoma) was studied with a Heidelberg Retina Flowmeter. Temporal flow adjacent to the disc edge was significantly higher than the nasal flow (p < 0.01). It was reduced significantly in myopia both in controls (p < 0.05) and in glaucoma patients (p < 0.001). However, there was no difference between either controls and glaucoma patients or between POAG and NPG patients. It was independent of treatment type in glaucoma. Within the temporal peripapillary area extremely high flow values (values higher than the mean + 2 SD of the corresponding individual retinal flow) seemed to represent deep peripapillary vascular rings. They were significantly more frequent in glaucoma (72%) than in healthy volunteers (44%, p < 0.05). Their frequency was 83% in myopic and 23% in non-myopic eyes in the control group (p < 0.001). However, in glaucoma patients they were common both in myopic eyes (71%) and in non-myopic ones (75%). The results suggest that capillary perfusion adjacent to the temporal edge of the disc is significantly reduced in myopia. Deep peripapillary vascular structures can be measured on images focused on the surface of the retina, especially if the retina is thinner than normal (healthy myopic eyes and glaucomatous eyes independently of the refraction). This may mask a deficient function of the retinal capillary bed.

Covariation of optic disc measurements and ocular parameters in the healthy eye

To understand the variations in optic disc topography that may affect the local susceptibility of nerve fibers to glaucomatous damage, we evaluated the correlations between optic disc topography and selected ocular parameters in 210 normal eyes of healthy Japanese. In the total study group, eyes with a longer axial length had a longer distance between the disc and foveola, a larger index of ovalness and a larger disc (P < 0.01). A longer disc-foveola distance correlated with a larger index of ovalness (P < 0.01). The optic discs of severely myopic eyes had a considerably different structure from other eyes. Eyes with a tilted optic disc were unique in that the area of the optic disc was not large despite a positive correlation with long axial length (P < 0.01) a long disc-foveola distance (P < 0.01), and a large index of ovalness (P < 0.01). Eyes with a rotated optic disc were another special case. This eye type correlated in a contradictory fashion with two parameters: a large axial length (P < 0.01) and a short disc-foveola distance (P < 0.01). These findings suggest that changes in optic disc topography or susceptibility to glaucomatous damage correlate with selected ocular parameters but are not completely parallel.