Macular hole (MH) is defined as a full thickness disruption
of the neurosensory retina at fovea. In the nineteenth century, interest into
the MH pathophysiology and treatment was limited. Later, Kelly and Wendel
performed the pioneering work on vitrectomy with cortical vitreous detachment
and gas tamponade in MH.(1) This revolutionised the understanding
behind the pathophysiology and management of MH.
Primary or idiopathic MH occurs due to abnormal
vitreo-foveal traction in the absence of other ocular pathologies. With the continuing
advancements in optical coherence tomography (OCT), the understanding of
idiopathic MH has improved considerably. Therapeutic strategies such as chromo
vitrectomy and internal limiting membrane (ILM) peeling are continuously being
optimised for idiopathic MH. On the other hand, secondary MH arise out of
several ocular pathologies. With improvement in imaging technologies, they are
more frequently seen nowadays. The pathogenetic mechanisms, morphology,
prognostic factors and surgical outcomes in secondary MH are all equivocal.
This article reviews and aims to categorize all reported causes of secondary MH
into meaningful domains which can then help one in determining the prognosis
and rationale management approach in individual cases.
Typical and atypical macular holes
Idiopathic MH develop due to oblique
antero-posterior vitreo-foveal traction (VFT) occurring during the course of
posterior vitreous detachment (PVD).(2) Old age and female gender are
important risk factors for idiopathic MH formation.(3) Gass proposed the biomicroscopic
description and staging of MH from impending to full thickness MH.
Trauma and myopia are among the most
common causes of secondary MH and their characteristics and management have been
well documented. Indeed the first MH described by Knapp in 1869 was a traumatic
MH.(4) Traumatic MH develops as a consequence
of combination of factors like contusion necrosis, cystoid degeneration, and
vitreous traction.(5,6) It is advisable to wait for 6 months
before surgical intervention in such eyes to allow spontaneous hole closure.(5,6)
Myopic eyes develop MH due to
tangential vitreous traction, rigid ILM and progressive chorioretinal atrophy
within the area of posterior staphyloma.(7,8) Presence of full thickness MH in
myopic retinoschisis is a definitive indication for surgery. However prognosis
worsens once MH develop in eyes with foveoschisis.
As idiopathic, traumatic and myopic MH are among the
commoner causes of MH and have been discussed in detail in literature, we
prefer to use the term ‘typical’ MH for these. The term ‘atypical’ will be used
throughout the review for rest of the MH.
Classification of atypical macular
The various causes of atypical macular holes are
categorised and mentioned in table 1.
Retinitis Pigmentosa (RP), Best dystrophy (BD), and
adult onset foveal vitelliform dystrophy (AOFVD) are among the most common
retinal dystrophies associated with secondary MH formation. The characteristics
of MH associated with various vitreo-retinopathies are shown in table 2.
Macular abnormalities, especially
cystoid macular edema (CME) frequently occur in RP.(9–14) RPE dysfunction and pump failure
leads to fluid leakage and CME. The presence of vitreomacular traction (VMT)
may also add to CME formation due to the mechanical pull of cortical vitreous
on inner retinal layers. FTMH may form after degeneration of the inner layer of
cysts. Progressive retinal atrophy, epiretinal membrane (ERM) contraction,
vascular disturbances, and inflammatory insult are among other presumed
mechanism behind MH formation in such eyes.(11,15–17)