Intended for healthcare professionals

Letters

Treating myopia

BMJ 1995; 311 doi: https://doi.org/10.1136/bmj.311.6996.58 (Published 01 July 1995) Cite this as: BMJ 1995;311:58

This article has a correction. Please see:

  1. William Jory
  1. Consultant ophthalmologist London Centre for Refractive Surgery, London W1N 1PD

    Incisional keratotomy has a safer track record than photorefractive keratectomy

    EDITOR,--David S Gartry's review restores some balance to the debate about photorefractive keratectomy, emphasising that such surgery must be predictable, effective, and safe with a low incidence of complications.1 The excimer laser was introduced to treat myopia in the expectation that photoreactive keratectomy would surpass incisional keratotomy (microsurgery: the safer American development of Russian radial keratotomy) in predictability. This has not happened since a greater degree of remodelling is required after photoreactive keratectomy.

    It cannot be overemphasised that the fact that “15% of patients lose one or two lines of Snellen acuity, a significant loss,” is unacceptable for surgery on the healthy cornea. Furthermore, a recent study found that a tenth of patients treated with an excimer laser declined treatment of the other eye because of disturbances of night vision in the treated eye.2

    Of greater concern are the possible long term complications. Gartry lists decompensation of the cornea “as unlikely though not impossible.” This could occur from the shock waves in photoreactive keratectomy striking the corneal endothelium. Refractive surgeons remember that Sato's incisions in the posterior cornea eventually caused 85% of eyes to lose their vision, but only after 18 years, from decompensation (waterlogging) of the cornea.3 Photoreactive keratectomy may also reduce corneal tensile strength by altering the corneal structure.4 Complications in refractive surgery historically have been unexpected and emerged only after many years.

    Meanwhile, incisional keratotomy causes far less loss of visual acuity (1-3%), has a long term safety record, and allows almost immediate return of vision. Initial fears that eyes would be more susceptible to traumatic rupture after incisional keratotomy were discounted by Robin's study of 750000 eyes.5 Refractive surgeons have learnt to be conservative to avoid secondary hypermetropia. Currently, the predictability of the result of fourth incision keratotomy is higher than that of any results reported in the same refractive groups after treatment with an excimer laser.6

    Gartry reminds us that photoreactive keratectomy is an experimental, investigative procedure. It is astonishing that in a sophisticated country such as Britain there are minimal controls. It would seem reasonable to limit the numbers undergoing photoreactive keratectomy at approved research centres where independent assessment is done until results improve and more is known of possible long term complications. Whether it is ethical to charge for such experimental procedures for commercial gain is debatable.

    References