Macular hole (MH) is a full thickness defect in the
neurosensory retina at fovea. Earlier 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 whole
concept 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
advent of optical coherence tomography (OCT), the understanding of idiopathic
MH has improved considerably. Therapeutic strategies including 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. Degeneration of the inner layer of coalesced cysts can
thereby lead to FTMH. 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)