Clinical Guide to Degenerative Myopia
Article By: Matthew Geller
Co-Authored By: Antonio Chirumbolo & Stefania Paniccia
This article, created by Interns Geller, Chirumbolo and Paniccia was created to educate students on the basics of degenerative myopia. But really there is something deeper here. The authors felt that patients with high myopia really rely on their optometrist at yearly eye exams and these patients want to feel confident in their OD. Patients with high myopia can have vision threatening fundus pathology and it is important that as optometry students we really understand what is going on in their eyes. Expressing to your patients that you thoroughly understand their condition will help you to build a patient base when you are out in practice. There should be no need to refer their patients out… Understanding degenerative myopia and attracting these patients to your practice is a great way to ensure your future success as an OD.
Degenerative myopia is severe myopia greater than 6.00 Diopters that begins in youth (usually pre-teen years) and progresses in stages. To be classified as degenerative myopia, the myopia must be associated with degenerative changes in the posterior segment of the eye. Generally, myopia is the result of elongated axial length in the region of 25.5 or 26.5mm. (1,2)
Degenerative myopia is also known as other terminology including:
The epidemiology of this ocular condition generally has a prevalence with refractive error of greater than -7.9D. In the USA 0.2% – 0.4% of general population are classified as degenerative myopes while 1% of the Japanese population (approximately 1.25 million are degenerative myopes. Overall, 6-18% of myopes meet the degenerative criterion (3,4)
A very common question is how do patients become myopic? The answer is complex and involves many different mechanisms encompassing various systemic disorders, ocular disorders, and genetics:
It is important as primary eye care providers to be cognizant of the signs of degenerative myopia which commonly include:
The question becomes, which of the following signs are most common in this population of degenerative myopes. Several studies were conducted, and it appears that a majority of high myopes possess diffuse atrophy and fuch’s spots.
[Prevalence of fundus changes in 1584 consecutive eyes with high myopia. (5)]
[VA Log MAR with different fundus changes in 1,584 consecutive eyes with high myopia. (5)]
TOOLS TO MONITOR
Once a patient has been established as a degenerative myope, what is next? How do we manage and monitor these patients?
[Photo Courtesy of Co-Author of this article: Antonio Chirumbolo]
TIGROID FUNDUS: As the eye enlarges, the retinal pigment epithelium thins, resulting in a tessellated (checkered) appearance of the fundus and increased visibility of the choroidal vasculature.
POSTERIOR STAPHYLOMA: Staphylomas are localized ectasia (“enlargement”) of the sclera, choroid, and RPE. It can be easily seen on B-scan or a CT Scan. Staphylomas can eventually lead to atrophy and loss of vision.
FUCHS SPOTS: Fuch’s spots are dark spots due to RPE hyperplasia. They can involve subretinal neovascular membrane with an overlying retinal pigment epithelial hyperplasia. The CNV can eventually cause disciform scars on the macula in the 4th-6th decade of life.
LACQUER CRACKS: are spontaneous ruptures of the elastic lamina of Bruch’s membrane that appear yellowish-white and are usually located in the posterior pole. They generally have linear or stellate patters. IVFA will show hyperfluorescence, as the fluorescein leaks through Bruch’s membrane, highlighting these cracks. These can lead to CNV in the 4th-6th decade of life.
LATTICE DEGENERATION: is a vitreo-retinal degeneration that causes retinal atrophy (“thinning”). It can be classified as pigmented or non pigmented. It takes on a lattice formation (“crisscrossing”) because the retinal vessels become sclerotic, and the collagen is laid down in this crisscross pattern. Due to the retinal thinning, it is prone to causing retinal breaks, tears, or holes, which of course might lead to retinal detachment. However it is important to remember that retinal breaks due to lattice degeneration rarely turn into retinal detachments.
LATTICE WITH ATROPHIC HOLES: Atrophic holes occur due to retinal thinning. Vitreous traction is not the pathogenic mechanism. Atrophic retinal holes are often associated with lattice degeneration (LD). The incidence of retinal holes in LD ranges from 18-42%. Atrophic holes are generally asymptomatic and rarely require treatment.
WHITE WITHOUT PRESSURE (WsP): refers to geographic areas of apparent “whiteness” in the peripheral retina that is not caused by scleral indentation (therefore, without pressure). It is an optical phenomenon most likely related to collagen deposition at the retinal interface. In degenerative myopia, it is indicative of an area where the retina has been stretched, and is correlated with an increased risk for future retinal detachment in these eyes.
TILTED DISCS: are another sign of degenerative myopia. They are the result of oblique insertion of the optic nerves into the globe. The tilt is usually located inferonasal or inferotemporal. Corresponding arcuate blood vessels are often directed nasally before sweeping temporally. This misdirection of vessels is termed situs inversus. Visual field loss is common in patients with tilted discs and often presents as a bitemporal hemianopic field loss, especially when a scleral crescent is present inferotemporally. Visual acuity can be mildly or moderately impaired and is often attributed to an overlying refractive amblyopia.
CHOROIDAL NEOVASCULARIZATION (CNV): the growth of new blood vessels that originate from the choroid through a break in the Bruch membrane into the sub-retinal pigment epithelium (sub-RPE) or subretinal space, creating what is called a choroidal neovascular net. These vessels subsequently break and cause fibroblast proliferation, a disciform scar and loss of vision (if on macula). Mechanisms of CNV are not well understood. Virtually any pathologic process that involves the RPE and damages the Bruch membrane can be complicated by CNV. CNV may be considered as a wound healing response to an insult of the RPE. Choroidal neovascularization (CNV) is a major cause of visual loss.
Among all the myopic fundus pathologies, macular CNV is the most common vision-threatening complication reported to occur in 5-10% of patients with high myopia. (6)
The incidence of myopic CNV in patients with preexisting myopic CNV in the fellow eye is even higher, as more than 30% of patients will develop CNV in the second eye within eight years after the first eye. (7)
Choroidal neovascular membranes are small, flat, subretinal membranes with a grey appearance in the fundus. They are typically less than 1 disc diameter in size and are located between the neurosensory retina and retinal pigmented epithelium. The membrane forms in response to elevated VEGF and occurs primarily in the presence of lacquer cracks also associated with high myopia. Membranes are frequently subfoveal or juxtafoveal with minimal subretinal fluid or exudate. Patients with significantly high myopia must be monitored for membrane formation, which may warrant treatment with argon laser photocoagulation, anti-VEGF therapy, or photodynamic therapy if present. The incidence of myopic choroidal neovascularization in a patient with a preexisting membrane in the fellow eye is increased. Nominally, it is estimated that 30% of patients will develop a membrane in the second eye within 8 years of occurrence in the first eye.
WHAT DOES EVIDENCE BASED MEDICIN TELL US?
In summation, high myopes are prevalent in our patient population and we should feel confident in managing such cases. By demonstrating your proficiency with this condition, patients will remain loyal, visit yearly, refer your services, and generate revenue. In turn, the ultimate reward is positively impacting their quality of life.
This article was written by Matthew Geller of SUNY Optometry, Antonio Chirumbolo of SUNY Optometry and Stefania Paniccia of IAUPR Optometry. All students are graduating in the year 2013.
SOURCED CLINICAL STUDIES
(1) (OPTOMETRIC CLINICAL PRACTICE GUIDELINE CARE OF THE PATIENT WITH MYOPIA, David A. Goss, O.D., Ph.D., Et Al. Published August 9, 1997 Reviewed February 2001, Reviewed 2006)
(2) (Goss DA, Eskridge JB. Myopia. In: Amos JF, ed. Diagnosis and management in vision care. Boston: Butterworths, 1987:121-71.)
(3) (Sperduto RD, Seigel D, Roberts J, Rowland M. Prevalence of myopia in the US. Arch Opthalmol 1983; 101:405-v407)
(4) (Tokoro T. On the definition of pathological myopia in group studies. Acta Ophthalmol 1988;66:107-108)
(5) (Tokoro T. Mechanism of axial elongation and chorioretinal atrophy in high myopia. Nippon Gannka Gakkai Zasshi 1994;98:1213-1237)
(6) (Curtin BJ. Ocular finidings and complications. In:Curtin BJ Editor. The myopias. Philadelphia: Harper & Row, 1985, pp 277-347)
(7) (Ohno-Matsui K, Yoshida T, Futagami S, et al. Patchy atrophy and lacquer cracks predispose to the development of choroidal neovascularization in pathologic myopia. Br J Ophthalmol 2003;87:570-3.)
(8) Takayuki Baba, Kyoko Ohno-Matsui, Soh Futagami, Takeshi Yoshida, Kenjiro Yasuzumi, Ariko Kojima, Takashi Tokoro, Manabu Mochizuki, Prevalence and characteristics of foveal retinal detachment without macular hole in high myopia, American Journal of Ophthalmology, Volume 135, Issue 3, March 2003, Pages 338-342, ISSN 0002-9394, 10.1016/S0002-9394(02)01937-2. (http://www.sciencedirect.com/science/article/pii/S0002939402019372)
(9) Jorge L. Alió, Orkun Muftuoglu, Dolores Ortiz, Juan Jose Pérez-Santonja, Alberto Artola, Maria Jose Ayala, Maria Jose Garcia, Gracia Castro de Luna, Ten-year Follow-up of Laser In Situ Keratomileusis for High Myopia, American Journal of Ophthalmology, Volume 145, Issue 1, January 2008, Pages 55-64.e1, ISSN 0002-9394, 10.1016/j.ajo.2007.08.035. (http://www.sciencedirect.com/science/article/pii/S0002939407007817)
(10) The quality of life in patients with pathologic myopia. Takashima T Et al Jpn J Ophthalmol. 2001 Jan-Feb;45(1):84-92.
(11) Association between high myopia and progression of visual field loss in primary open-angle glaucoma. Yi-An Lee, Yung-Feng Shih, Luke Long-Kuang Lin, Jehn-Yu Huang, Tsing-Hong Wang. J Formos Med Assoc. 2008 December; 107(12): 952–957. doi: 10.1016/S0929-6646(09)60019-X
(12) U.S. Food and Drug Administration clinical trial of the Implantable Contact Lens for moderate to high myopia. Donald R. Sanders, John A. Vukich, Kimberley Doney, Monica Gaston, Implantable Contact Lens in Treatment of Myopia Study Group. Ophthalmology. 2003 February; 110(2): 255–266. http://www.ncbi.nlm.nih.gov/pubmed/12578765
(13) An analysis of high myopia in a pediatric population less than 10 years of age. David E Fitzgerald, Ida Chung, Ira Krumholtz. Optometry. 2005 February; 76(2): 102–114.
Give it a title.
Don't forget to enter your Clinical Pearl!
Are you a robot?