OCT and Me: A Beginner’s Guide

MACULAR PSEUDOHOLE

From fundoscopy, a macular pseudohole will look indistinguishable to a full thickness and lamellar macular hole. However, the optical coherence tomography (OCT) image allows diagnosis by showing an incomplete hole displaying no retinal tissue loss.¹

A pseudohole may be accompanied with retinal thickening, retinal contraction, and an epiretinal membrane. Looking further out into the retinal periphery, a macular pseudohole will always show a perifoveal epiretinal membrane³ – a macular cube or raster scan can be used to show this.

EPIRETINAL MEMBRANE

Epiretinal membranes (ERMs) are composed of a fibrous proliferation of glial cells, retinal pigment epithelium (RPE) cells and inflammatory cells, found along the inner limiting membrane (ILM).⁴ ERMs are thought to be a proliferation of remnants of the vitreous on the retinal surface.^1,4

OCT is essential for monitoring and managing ERMs to minimise risk for significant vision loss

An ERM will often present with a Weiss ring and vitreal tissue along the retinal surface.¹

Simple ERMs usually only display the mild subjective symptoms of minimal movement and minimal retinal distortion.

there is significant movement, it can escalate to a more complex ERM and lead to vascular distortion, macular pseudohole formation, edema, and thus significant visual symptoms.⁴ The traction from ERMs can also escalate to cause cystic formation, more significant visual symptoms, and subsequent visual loss due to a retinal detachment.

OCT is essential for monitoring and managing ERMs to minimise risk for significant vision loss.

MACULAR OEDEMA

Macular oedema is the presence of serous filled, cystic spaces found in a number of conditions including ERMs, diabetic retinopathy, retinal vein occlusions, retinitis pigmentosa, and post cataract cystoid macular oedema. It can be challenging to detect on fundoscopy and more easily diagnosed with OCT.

Macular oedema usually shows fluid accumulation within the outer plexiform layer. If more fluid accumulates, this fluid accumulation extends into the inner retina.⁵ The associated condition that caused the macular edema determines if there may be accompanying vascular damage, ischemia, and inflammation. These may lead to blood-retinal barrier breakdown and further inability for fluid filtration and removal.⁵

Depending on the condition causing macular oedema, appropriate treatments include anti vascular endothelial growth factor therapy, steroidal therapy, laser photocoagulation or carbonic anhydrase inhibitors.

CENTRAL SEROUS CHORIORETINOPATHY

Central serous chorioretinopathy (CSCR) is fluid accumulation underneath the retina or RPE, and is usually self-limiting.⁶ The formation of CSCR is associated with steroid use and high stress levels,⁷ and it shows a thickened and hyperpermeable choroid.⁸

CSCR is a retinal detachment with or without the presence of a pigment epithelial detachment (PED). PEDs appear to have an orange hue, which can be challenging to distinguish from RPE changes and lipofuscin deposits.

As CSCR resolves, it may leave pigmentary disturbance, which causes symptoms of visual distortion.

Patients… benefit when a more comprehensive investigation with OCT imaging is integrated into their routine eye examination

As a guide to diagnosing serous retinal detachment vs. pigment epithelial detachment, a CSCR is seen as a smooth diffuse elevation of the neurosensory retina, and is usually wider than it is taller.

A PED is usually smaller, and appears to have a similar height and width. A PED diagnosed without a neurosensory detachment can be stable and can sometimes self-resolve. OCT is vital in determining whether a patient may be monitored for a relatively benign case of CSCR or needs to be referred to a retinal specialist to rule out sight threatening conditions that require immediate treatment.

CASE STUDY: 72 YEAR OLD FRANK

Frank is a retired engineer who presented with difficulty reading for prolonged periods of time. He reported that reading for short periods of time at the office was fine, however the text became blurred after 15 minutes, and it was very difficult to continue reading after that. Yet, interestingly, he did not experience the same problem when reading in bed, and could comfortably read at night for a long time. After reading in bed he noticed an after-image that stayed for at least 30 minutes.

Having consulted multiple specialists, none were able to diagnose Frank’s condition. After many years, Frank’s symptoms were so frustrating that they were a key reason for his early retirement from work.

Medical History 

Anxiety, hypertension, raised cholesterol, knee pain, previous left eye corneal ulcer following a metal corneal foreign body many years prior.

Medications include Avapro, Viagra, Panadeine Forte. He had a family history of glaucoma.

Results 

RE +2.00/-0.25 x 90                6/6+,

LE +2.00 sph           6/6 Add +2.00D N5 Near, Amsler grid: normal OU,

Intraocular pressure: RE and LE 25mmHg, both eyes,

Pupils: No relative afferent pupil defect and normal pupil responses,

Fluorescein tear break up time: nine seconds, both eyes, and

Anterior segments: early nuclear cataract, both eyes.

Diagnosis 

OCTs showed mild vitreomacular traction (VMT) which increased in severity after reading for 15 minutes, that is, dynamic VMT exacerbated by reading.

Treatment recommended was a vitrectomy performed to relieve VMT.

Outcome 

One month post operation, Frank was seeing 6/6 in each eye, and was no longer struggling to read. Reading was no longer accompanied by frustration, and was enjoyable again. He was very satisfied with the outcome.

Thanks to Dr. Simon Chen, retinal ophthalmologist, for this case study.

THE VALUE OF OCT IN CLINICAL PRACTICE

Patients with potentially missed pathology can benefit when a more comprehensive investigation with OCT imaging is integrated into their routine eye examination.

Used to complement retinal photography, OCT can help detect and diagnose retinal, macular, and chorioretinal lesions, ocular pathology in the vitreoretinal interface, and choroidal disease. In turn, this enables optometrists to initiate management and achieve better patient visual outcomes.

Margaret Lam is an optometrist with theeyecarecompany. She practices in greater Sydney and Sydney CBD and is an Adjunct Senior Lecturer at the School of Optometry and Vision Science at UNSW. She also works as the Head of Optometry Services for George and Matilda Eyecare.

Margaret practises full scope optometry, but with a passionate interest in contact lenses, retail aspects of optometry and successful patient communication and management. She has extensive experience in specialty contact lens fitting in corneal ectasia, keratoconus and orthokeratology and is a past recipient of the Neville Fulthorpe Award for Clinical Excellence. Margaret writes ‘mipatient’ on alternate months with Jessica Chi.

 

References: 

1. Duker, Jay S., et al.The International Vitreomacular Traction Study Group classification of vitreomacular adhesion, traction, and macular hole. Ophthalmology 120.12 (2013): 2611-2619.
2. newgradoptometry.com/complete-list-ocular-diseasesoptical- coherence-tomography-oct 
3. Haouchine, Belkacem, et al.Diagnosis of macular pseudoholes and lamellar macular holes by optical coherence tomography. American journal of ophthalmology 138.5 (2004): 732-739. 
4. Steel, D. H. W., and A. J. Lotery. Idiopathic vitreomacular traction and macular hole: a comprehensive review of pathophysiology, diagnosis, and treatment. Eye 27 (2013): S1-S21. 
5. Scholl, Stefan, et al. General pathophysiology of macular edema. European journal of ophthalmology 21 (2010): S10-9. 
6. Liegl, Raffael, and Michael W. Ulbig. “Central serous chorior etinopathy.”Ophthalmologica 232.2 (2014): 65-76. 
7. Yannuzzi, Lawrence A. “Type A behavior and central serous chorioretinopathy.” Transactions of the American Ophthalmological Society84 (1986): 799. 
8. Dansingani, Kunal K., et al. “En face imaging of pachychoroid spectrum disorders with swept-source optical coherence tomography.” Retina 36.3 (2016): 499-516.