I’m sure you have noticed that myopic patients tend to develop cataracts earlier in life compared to their emmetropic and hyperopic cohorts. What is it about an eye with an elongated axial length that spurs early cataract development? Of course we have a great solution, cataract surgery and that can even address the large refractive error. But why do they develop cataracts earlier? Please leave your comments below if you have insight into this.
The reasons that high myopes are likely to develop both cataracts and glaucoma at an early age is because they are both associated with oxidative damage. High (pathologic) Myopia is associated with vitreous degeneration, more severe and at an earlier age. The vitreous has a function of scavenging reactive oxygen species and that is why when you do a vitrectomy in a phakic patient a cataract invariably develops within a short period of time…..due to oxidative damage to the lens. Cataracts are associated with oxidative damage to the lens from reactive oxygen species which are scavenged by the vitreous delaying that process. When the vitreous is removed it doesn’t take long for the cataract to manifest. Glaucoma is also more common after PPV because of oxidative damage to the TM (among other reasons). When the vitreous undergoes syneresis and becomes degenerative it loses this oxygen scavenging capacity to protect the eye from reactive oxygen species and thus there is a higher incidence of complications from those free radicals. Pathologic myopes present with the triad of vitreous syneresis, cataract and higher rates of glaucoma…..due to oxidative damage. Oxidative damage breaks down the vitreous but also creates a vicious cycle where the vitreous can no longer protect against these reactive species (degenerative vitreous loses this capacity) and thus you see progressive changes rather quickly at an earlier age in these pathologic myopes.
thanks Steve — great insight!
Excellent response!
I am a fellowship trained glaucoma specialist at the age of 64. My AL OD = 27.64 and OS + 27.40. I am scheduled for CE/Hydrus OD on 6/11 and OS 6/18. Previously , I have MS in biochemistry. Their is some literature concerning oxidative stress and low oxygen tension in high myopia. Front Physiol.
2020; 11: 463.
Published online 2020 May 14.
doi:
10.3389/fphys.2020.00463
PMCID:
PMC7240122
PMID:
32477165
Imbalance Between Oxidative Stress and Growth Factors in Human High Myopia
Salvador Mérida
,
Vincent M. Villar
,
Amparo Navea
,
Carmen Desco
,
María Sancho-Tello
,
Cristina Peris
,
and
Francisco Bosch-Morell
Abstract
Myopia is one of the commonest eye pathologies that could affect 2.56 billion people by 2020.Today high myopia is a leading cause of blindness worldwide due to associated ocular illness.Nevertheless, the cellular bases for these diseases to develop are unclear in many areas. We con‐ ducted a prospective study of oxidative stress and growth factors in human myopic and non my‐ opic eyes in an attempt to increase our understanding of the underlying physiopathological condi‐ tions to adequately early diagnose, prevent and treat the retina problem that derives from myopia.Aqueous humor samples were obtained from 41 patients being operated for cataracts in our hos‐ pital. Axial length, refractive status and complete ophthalmologic examination were recorded. TheVEGF and HGF levels were determined by an ELISA kit. Total antioxidant capacity and totalnitrites/nitrate levels were established with a lab kit. We show for the first time an increase in thetotal nitrite levels in high myopia. We also propose for the first time the concurrence of three fac‐ tors: myopia, oxidative stress, and oxidative stress together with growth factors in the same groupof patients. In this way, it would not be accurate to envision high myopia as a type of normal my‐ opia, but one with more diopters or longer axial length.
Keywords:
high myopia, oxidative stress, VEGF, HGF, total nitrates, TAC
very insightful. thank you.