Outer Foveal Microdefects
Posted injournal club

Outer Foveal Microdefects

Outer Foveal Microdefects 26-7-2021

Outer Foveal Microdefects (OFMD)

General Overview

  • Outer Foveal Microdefect (OFMD) is a spectral-domain OCT (SD-OCT) finding characterized by focal disruption of foveal photoreceptors, specifically the cone outer segment tip line, with an intact retinal pigment epithelium (RPE).

  • Previously termed “macular microhole” or “foveal spot,” but OFMD is the preferred term to avoid confusion with full-thickness macular holes requiring surgery.

  • Observed in various macular conditions, not limited to vitreomacular disorders, including traumatic and degenerative etiologies.

  • Prevalence is not well-established, but it is a relatively rare clinical sign detected on SD-OCT.

Clinical Presentation

  • Patient demographics: Affects both genders (30 females, 15 males), wide age range (10–88 years, mean 58.8 years).

  • Symptoms: Central scotoma, metamorphopsia, and mild to moderate visual loss.

  • Visual acuity (VA): Initial VA ranges from 50–85 ETDRS letters (mean 76.2 letters), typically stable during follow-up (±3 letters in most cases).

  • OFMD diameter: Ranges from 10–249 μm (mean 88.6 μm), with diameter <250 μm as an inclusion criterion.

  • Prognosis: Improvement (reduced diameter or full disappearance) in 9 of 14 eyes with follow-up (mean 29.8 months); stable in 5 eyes.

Associated Conditions

  • Most common etiology: Posterior vitreous detachment (PVD) or vitreomacular interface changes (24/51 eyes).

    • Includes vitreomacular traction (VMT, 2 eyes), epiretinal membrane (ERM, 3 eyes), and irregular foveal pit suggestive of prior vitreofoveal detachment.

  • Retinal phototoxicity (5 eyes): Caused by laser therapy (2 eyes) or sun gazing (3 eyes).

  • Blunt trauma (2 eyes): Results in photoreceptor damage due to shock wave convergence at the fovea.

  • Macular edema sequelae (3 eyes): Secondary to retinal vein occlusion (RVO).

  • Macular telangiectasia type 2 (MacTel 2) (2 eyes): Associated with Müller cell loss leading to photoreceptor defects.

  • Other reported conditions (not observed in this study but relevant):

    • Acute retinal pigment epitheliitis.

    • Occult macular dystrophy (larger, less defined defects).

    • Tamoxifen maculopathy.

    • Chronic central serous chorioretinopathy.

    • SSRP1-dominant optic atrophy and foveopathy.

 

 

Diagnostic Imaging

  • Spectral-Domain OCT (SD-OCT):

    • Hallmark finding: Focal disruption of the ellipsoid zone (EZ) or cone outer segment tip line at the fovea, with preserved RPE.

    • May show intraretinal hyperreflective lines (IHL) in some cases (3 eyes), potentially linked to high choroidal pressure.

    • Subfoveal choroidal thickness: Ranges from 97–578 μm (mean 289 μm); >320 μm in 16/51 eyes, suggesting pachychoroid features.

  • Fundus photography:

    • Shows subtle yellowish or grayish foveal spots.

  • Fundus autofluorescence (FAF): May reveal subtle changes but not diagnostic.

  • Fluorescein angiography (FA) and indocyanine green angiography (ICGA): Limited utility; ICGA rarely used but may support pachychoroid diagnosis.

  • OCT Angiography (OCTA): No significant findings in this study.

  • Pachychoroid features:

    • Observed in 35/51 eyes (definite/likely), especially in patients >55 years (48.2% definite, 6.8% possible).

    • Features include thick choroid, dilated choroidal veins in Haller’s layer, subretinal exudation, or peripapillary pachychoroid syndrome.

Pathophysiology

  • Mechanism: Various injuries (vitreomacular traction, phototoxicity, trauma, edema) lead to focal photoreceptor loss, often with incomplete recovery of foveal architecture.

  • Pachychoroid hypothesis: High choroidal pressure in pachychoroid spectrum disorders (e.g., central serous chorioretinopathy, pachychoroid pigment epitheliopathy) may impair photoreceptor-RPE adhesion post-detachment, promoting OFMD.

  • MacTel 2: Müller cell loss secondarily affects cones, causing rectangular or central photoreceptor defects.

  • Trauma and phototoxicity: Direct photoreceptor damage from mechanical or light-induced injury.

 

Management and Prognosis

  • No specific treatment: Most cases are observed, as spontaneous improvement is common (e.g., reduced OFMD diameter in PVD, RVO, trauma cases).

  • Monitoring:

    • Regular SD-OCT to assess OFMD diameter and choroidal thickness.

    • Visual acuity and symptom monitoring for stability.

  • Prognosis: Generally favorable with stable VA and potential for defect reduction, but long-term studies are needed.

 

Epidemiology

  • Rare condition, with fewer than 100 cases reported in the literature.

  • No clear racial or geographic predilection noted in this study.

 

Key Considerations for Exams

  • Differentiate OFMD from full-thickness macular holes, as the latter may require surgical intervention.

  • Recognize pachychoroid features as a potential risk factor, especially in older patients with thick choroids.

  • Understand the broad differential of conditions causing OFMD, including vitreomacular, traumatic, and degenerative etiologies.

  • SD-OCT is the primary diagnostic tool, with characteristic focal EZ disruption and preserved RPE.

 

Citation

  • Cohen SY, Mrejen S, Nghiem-Buffet S, Dubois L, Fajnkuchen F, Gaudric A. Outer Foveal Microdefects. Ophthalmology Retina. 2021;5(6):553-561. Available at: www.ophthalmologyretina.org.

 

Retinal Phototoxicity Following Phacoemulsification Surgery

 

General Overview

Retinal phototoxicity is a rare complication of phacoemulsification cataract surgery, resulting from intense light exposure from the operating microscope.

  • Phacoemulsification is the preferred cataract surgery method, with a low complication rate (1.2%) and high success rate (93%).

  • Phototoxicity can also occur from other light sources, such as sunlight (solar maculopathy).

 

Clinical Presentation

  • Symptoms: Central scotoma immediately post-surgery, as seen in the reported case of a 59-year-old male.

  • Visual acuity:

    • Preoperative: 0.7 (Snellen), improving to 0.9 with pinhole.

    • Six days postoperative: 0.9 (Snellen).

    • Three months postoperative: Improved to 1.2 (Snellen), indicating favorable recovery.

  • Ocular history:

    • Prior refractive laser surgery (LASEK, initial refraction -4.50 D, pre-phacoemulsification -2.75 D).

    • Bilateral retinal detachments treated with pars plana vitrectomy (PPV), resulting in absence of vitreous.

  • No systemic diseases (e.g., diabetes or vascular conditions) or medication use reported.

 

Diagnostic Findings

  • Preoperative:

    • Slit lamp: Nuclear cataract.

    • Fundus examination and optical coherence tomography (OCT): Normal macula.

  • Postoperative (6 days):

    • Slit lamp and fundus examinations: Unremarkable.

    • OCT: Small disruption in central outer retinal layers at the fovea.

  • Postoperative (3 months):

    • Slit lamp and fundus examinations: Normal.

    • OCT: Improvement with only minor outer retinal irregularity remaining.

  • Key imaging modality: OCT is critical for detecting outer retinal disruption and monitoring recovery.

 

Risk Factors for Retinal Phototoxicity

  • Relatively clear lens: Allows greater light transmission to the retina.

  • Emmetropia post-lens implantation: Focuses microscope light precisely on the fovea.

  • Small incision surgery: Minimizes ocular surface distortion, enabling accurate light focusing.

  • Prior vitrectomy: Absence of vitreous allows direct light exposure to the retina without deflection.

  • Absence of residual astigmatism: Enhances precise light focus, especially post-refractive surgery.

  • Light intensity: Higher settings increase phototoxicity risk; should be kept at an acceptable minimum.

 

Pathophysiology

  • Phototoxicity results from the interaction of intense microscope light with ocular structures, damaging the vulnerable retina.

  • Foveal focus: Parallel light from the microscope is focused on the fovea, especially in emmetropic or vitrectomized eyes.

  • Damage primarily affects the outer retinal layers, leading to photoreceptor disruption.

 

Management and Prognosis

  • Management: Watchful waiting is the primary approach, as spontaneous recovery is common.

  • Prognosis: Favorable, with spontaneous resolution of outer retinal disruption and improved visual acuity (e.g., 1.2 Snellen at 3 months).

  • Prevention:

    • Minimize light intensity during surgery.

    • Consider risk factors (e.g., clear lens, prior vitrectomy) to adjust surgical parameters.

 

Epidemiology

  • Very rare complication, with few reported cases post-phacoemulsification.

  • No specific racial or geographic predilection noted in the case report.

 

Key Considerations for Exams

  • Recognize retinal phototoxicity as a rare but testable complication of phacoemulsification, distinct from more common issues like posterior capsule rupture.

  • Understand risk factors, particularly prior vitrectomy, emmetropia, and clear lens, which are likely to be emphasized in OKAP questions.

  • OCT findings (outer retinal disruption improving over time) are critical for diagnosis and monitoring.

  • Differentiate from other causes of postoperative central scotoma (e.g., macular edema, toxic maculopathy).

 

Citation

  • Nazari T, Jalink MB. Central scotoma following phacoemulsification surgery: A case report on retinal phototoxicity. Am J Ophthalmol Case Rep. 2025;38:102334. Available at: www.ajocasereports.com.

Tags: