Ophthalmology

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Ophthalmology2017-07-06T20:48:48+00:00

Ophthalmology

Cataract surgery 800 BC image from New Medical Terms

cataract surgery, state of the art 800 BC

Ophthalmology is one of the oldest fields of medicine. The Indian physician Sushruta (circa 800 BC), described a primitive procedure to address clouded eyesight due to cataracts, by poking a needle through the cornea and pushing it out of the line of vision*. Two thousand years passed before removal of cataracts became a standard of care in the 18th century through the work of Baron Johann de Wenzel (1724–90), German oculist to King George III of England. 

*The curious can read a translation of Sushruta’s original description from Sanskrit with this link http://ultadin.com/2016/08/04/cataract-surgery-was-first-found-in-ancient-india-and-then-introduced-to-other-countries-by-the-indian-physician-sushruta/

The 19th century saw von Helmholz’s 1851 invention of the ophthalmoscope, ushering in a new era of ophthalmology. In 1857,  Albrecht von Graefe (1828-1870), the so-called father of modern ophthalmology, performed a partial iridectomy, the first successful treatment for acute glaucoma. Glaucomas remained a surgical disease until carbonic anhydrase inhibitors, in particular acetazolamide*, proved their mettle in the medical management of increased intraocular pressure (IOP).

*Acetazolamide inactivates carbonic anhydrase and interferes with the sodium pump, reducing aqueous humor formation, reducing IOP. 

Ophthalmology image from New Medical Terms

ophthalmologic surgery state of the art 2017

The retina was the final frontier in managing diseases of the eye. Like stopping the hiccups, it seemed that every ophthalmologist in the early 20th century had a theory of what caused retinal detachment (RD) and how to manage it. In 1912, DT Vail examined the data and concluded that the success rate was 1 in 1000 and none of the proposed therapies worked. In 1920, Jules Gonin formally ran his theory on RD up the flagpole, attributing RD to breaks in the retina, and proved it by cauterising the sclera overlying the breaks, closing them and causing the retina to re-attach. By today’s standards, Gonin’s success rate was dismal at 50%, but compared to those of the day, they were spectacular. 

In the current environment, retinal surgeons have a number of options for managing RD. Increasingly popular is vitrectomy*, which involves removing the vitreous gel and filling the eye with either a gas (SF6 or C3F8) or silicone oil. The advantage of vitrectomy is that it doesn’t cause a post-operative myopic shift typical of scleral buckle surgery, in which an already myopic eye may be made more so by external pressure on the eyeball from the scleral band/tire. A third procedure, pneumatic retinopexy*, is waning in popularity as it has the disadvantage of requiring that the patient strictly maintain a specific head position to ensure that the bubble of gas (as above) rests against the retinal hole and has a significantly lower success rate, based on a Cochrane review of the data. 

 *Lasers are often used (bottom image), either as an adjunct to vitrectomy or pneumatic retinopexy to “spot-weld” the retina in place or, less commonly, as a stand-alone procedure for managing RD. 

Just over the horizon for ophthalmology, as well as all other fields of medicine, is the promise of gene therapy for inherited diseases. It is now known that whilst many hereditary conditions share the same clinical picture, for example retinitis pigmentosa, they are caused by different, often many different, genes. As an example, retinitis pigmentosa 4 (RP4) is caused by a defect in RHO—the gene that encodes rhodopsin, a transmembrane receptor protein; RP14 is caused by a defect of TULP1—the gene that encodes tubby like protein 1, which is required for normal development of photoreceptor synapses, photoreceptor function and for long-term survival of photoreceptor cells; RP19 is caused by a defect of ABCA4—the gene that encodes ATP-binding cassette—sub-family A (ABC1)—member 4, a protein expressed exclusively in retina photoreceptor cells, indicating that it mediates transport of an essential molecule across the photoreceptor cell membrane

This means that gene therapy, when it transitions from the research bench to the bedside…and it will, will respond to manipulation of the defective gene, and only that gene. 

These are truly exciting times. 

References https://en.wikipedia.org/wiki/Ophthalmology

https://www.drugs.com/drug-class/carbonic-anhydrase-inhibitors.html

http://eknygos.lsmuni.lt/springer/381/1-24.pdf

JOE Add this reference later.

https://en.wikipedia.org/wiki/Retinal_detachment